Molecular structure investigation of neutral, dimer and anion forms of 3,4-pyridinedicarboxylic acid: a combined experimental and theoretical study.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 270–282

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa

Molecular structure investigation of neutral, dimer and anion forms of 3,4-pyridinedicarboxylic acid: A combined experimental and theoretical study Mehmet Karabacak a, Sibel Bilgili b, Ahmet Atac b,⇑ a b

Department of Mechatronics Engineering, H.F.T. Technology Faculty, Celal Bayar University, Turgutlu, Manisa, Turkey Department of Physics, Celal Bayar University, Manisa, Turkey

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

Monomeric and anion conformations

and dimeric structure of 3,4-PDCA were investigated. Spectroscopic features of 3,4-PDCA were examined by NMR, UV, infrared and Raman techniques. The vibrational frequencies, chemical shifts and electronic absorption wavelengths were calculated by DFT.

a r t i c l e

i n f o

Article history: Received 5 May 2014 Received in revised form 18 June 2014 Accepted 25 June 2014 Available online 3 July 2014 Keywords: FT-IR and FT-Raman NMR and UV spectra DFT 3,4-Pyridinedicarboxylic acid Dimer and anion forms

a b s t r a c t In this study, the structural and vibrational analysis of 3,4-pyridinedicarboxylic acid (3,4-PDCA) are presented using experimental techniques as FT-IR, FT-Raman, NMR, UV and quantum chemical calculations. FT-IR and FT-Raman spectra of 3,4-pyridinedicarboxylic acid in the solid phase are recorded in the region 4000–400 cm1 and 4000–50 cm1, respectively. The geometrical parameters and energies of all different and possible monomer, dimer, anion1 and anion2 conformers of 3,4-PDCA are obtained from Density Functional Theory (DFT) with B3LYP/6-311++G(d,p) basis set. There are sixteen conformers (C1AC16) for this molecule (neutral form). The most stable conformer of 3,4-PDCA is the C1 conformer. The complete assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes calculated with scaled quantum mechanics (SQM) method. 1H and 13C NMR spectra are recorded and the chemical shifts are calculated by using DFT/B3LYP methods with 6-311++G(d,p) basis set. The UV absorption spectrum of the studied compound is recorded in the range of 200–400 nm by dissolved in ethanol. The optimized geometric parameters were compared with experimental data via the X-ray results derived from complexes of this molecule. In addition these, molecular electrostatic potential (MEP), thermodynamic and electronic properties, HOMO–LUMO energies and Mulliken atomic charges, are performed. Ó 2014 Elsevier B.V. All rights reserved.

Introduction ⇑ Corresponding author. Tel.: +90 236 2013105. E-mail address: [email protected] (A. Atac). http://dx.doi.org/10.1016/j.saa.2014.06.130 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

Pyridine carboxylic acids (PCAs) are beneficial compounds for human organism. PCAs are involved in several essential

M. Karabacak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 270–282

biochemical processes. 3-Pyridine carboxylic acid (3-PCA) is converted to nicotinamide adenine nucleotide which serves as intermediate in two-electron transfer in organism [1]. PCAs act as chelating agents of elements such as chromium, zinc, manganese, copper, iron, and molybdenum in the body. They are involved in phenylalanine, tryptophan, and alkaloids production, and for the quantitative detection of calcium. This forms a complex with zinc, may facilitate the passage of zinc through the gastrointestinal wall and into the circulatory system. PCAs and their derivatives can be studied for these effects. PCAs are used as intermediate to produce pharmaceuticals and metal salts for the application of nutritional supplements. The metal complexes of biologically important ligands are sometimes more effective than free ligands [2]. McCann et al. [3] investigated vibrational modes and theoretical calculations of 2,6-, 3,5-pyridinedicarboxylic acid (3,5-PDCA) and their calcium and sodium salts. Experimental and theoretical vibrational spectra of picolonic (2-pyridine carboxylic), nicotinic (3-pyridine carboxylic) and isonicotinic (4-pyridine carboxylic) acid were studied by DFT calculations with different methods by Koczon et al. [4]. Besides all these, Whitfield et al. [5] and Xu et al. [6] synthesized complex crystal of 3,5-PDCA. In our previous works, we presented theoretical and experimental spectroscopic features included FT-IR, FT-Raman and UV of monomer and dimer conformers [7] and FT-IR, FT-Raman and NMR analysis of neutral and anion forms [8] for 3,5-PDCA. The cadmium crystal of 3,4-PDCA was synthesized by Wang et al. [9]. Also, the structural relationship between the two crystal forms of 3,4-PDCA was investigated by single crystal X-ray diffraction and examined vibrational spectroscopy by Braga et al. [10]. However, literature surveys reveals that to the best of our knowledge, there is no theoretical study on 3,4-PDCA has been published yet. This insufficiency observed in the literature stimulate us to make theoretical and experimental study on 3,4PDCA. Also, the present work is a continuation of our previous study [7,8]. This present work aim to give a comprehensive working which included both a complete description of the molecular structure and vibrations of monomer, dimer and anion forms of 3,4PDCA. Also this work includes NMR and UV spectroscopic analyses, electronic and thermodynamic properties of 3,4-PDCA. Experimental 3,4-PDCA in solid phase was purchased from Merck Company with a stated purity of 97%. The sample was prepared using a KBr disc technique. The FT-IR spectrum of 3,4-PDCA molecule was recorded between 4000 and 400 cm1 on a Perkin–Elmer FT-IR System Spectrum BX spectrometer, which was calibrated using polystyrene bands. FT-Raman spectrum of the sample was recorded using 1064 nm line of Nd: YAG laser as excitation wavelength in the region 4000–50 cm1 on a Bruker FRA 106/S FT-Raman. The detector is a liquid nitrogen cooled Ge detector. Five hundred scans were accumulated at 4 cm1 resolution using a laser power of 100 mW. NMR experiments were performed in Varian Infinity Plus spectrometer at 300 K. The 3,4-PDCA molecule was dissolved in dimethylsulfoxide (DMSO). Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H NMR, 13C NMR spectra. 1H and 13C NMR spectra were obtained at a base frequency of 75 MHz for 13C and 300 MHz for 1H nuclei. The UV absorption spectrum of 3,4-PDCA was examined in the range of 200–400 nm using Shimadzu UV1700 PC, UV recording Spectrophotometer. The UV pattern is taken from a 105 molar solution of 3,4-PDCA, solved in ethanol. Computational details In order to obtain stable structure, the geometrical parameters for possible 16 conformers of 3,4-PDCA in the ground state are

271

optimized at DFT/B3LYP level of theory using the 6-311++G(d,p) basis set and then the most stable conformer of 3,4-PDCA is chosen as the C1 conformer because it has the smallest energy. The vibrational frequencies of 3,4-PDCA are calculated with DFT method for monomer, dimer and two anion forms of C1. The wavenumbers from 4000 to 1700 cm1 and lower than 1700 cm1 are scaled with 0.958 and 0.983, respectively [11]. The detailed theoretical calculations are compared with the experimental IR and Raman spectra of the title molecule. The fundamental vibrational modes are characterized by their TED which was calculated by using the SQM method [12,13]. All the calculations are performed by using Gaussview molecular visualization program and Gaussian09 package program. The Becke’s three-parameter hybrid density functional, B3LYP [14,15], is used to estimate harmonic vibrational wavenumbers with the 6-311++(d,p) basis set. For NMR calculations, 1H and 13C NMR chemical shifts are calculated using the gauge-invariant atomic orbital (GIAO) method [16] in DMSO at DFT/B3LYP method with 6-311++G(d,p) basis set for the optimized structure. Relative chemical shifts are estimated by using the corresponding TMS shielding calculated in advance at the same theoretical level as the reference. UV spectrum is recorded in ethanol and computed. The electronic transitions such as the highest occupied molecular orbital (HOMO) and the lowest lying unoccupied molecular orbital (LUMO) energies are computed with DFT method. Also, thermodynamic properties; heat capacity (C), enthalpy changes (H) and entropy (S) for the title molecule are obtained from the theoretical harmonic frequencies. The polar and electronic properties as the chemical potential (l), electronegativity (v), electrophilicity index (x) and chemical hardness (g) of the title molecule are computed. The charge distribution is calculated and the MEP of the studied molecule are evaluated to investigate the reactive sites of the title compound using the B3LYP/6-311++G(d,p) method. Results and discussion The all possible monomer molecular structures (C1-C16), dimer and two anion forms with numbering of the atoms of 3,4-PDCA are shown in Figs. 1–3, respectively. Energetic values of C1 and CS point groups of all conformers are presented in Table 1. The energies of dimer, anion1 and anion2 forms are given with energy of the neutral form (C1) in Table S1. The energetic values of C1 and CS point groups of all conformers of anion1 structure are given in Table S2. The stable structure is chosen C1 point group of C1 conformer as the structure has minimum energy and Cs point group of C1 conformer has negative frequency, therefore C1 conformer has been taken into account in the present discussion for all calculations. The point group of dimeric conformer of 3,4-PDCA is calculated as Ci and the calculations have been made with respect to this point group. We reported some geometric parameters and vibrational frequencies for 3,4-PDCA by using DFT (B3LYP) and compared with the experimental data (bond lengths and bond angles) and experimental frequencies. Geometrical structure The optimized structure parameters (bond lengths and bond angles) are calculated DFT (B3LYP) with the 6-311++G(d,p) basis set. The geometric data of 3,4-PDCA molecule have been taken from X-ray structure of complex of this molecule [5,6,10] as there is not any data of free 3,4-PDCA in literature yet. Theoretical and experimental structure parameters are listed in Table 2 for neutral (monomer), dimer and anion forms of title molecule. Taking into account that the molecular geometry in the gas phase may be different from in the solid phase, owing to

272


extended hydrogen bonding and stacking interactions there is reasonable agreement between the calculated and experimental geometric parameters. The CC bond lengths of the pyridine ring of the molecule showed good agreement with experimental values. For example, the calculated C1AC2 bond length is 1.390 Å for the neutral, dimer forms and 1.384 Å, 1.388 Å for anion1 and anion2 forms, respectively. The same bond length has been found as 1.393 Å and 1.389 Å by Whitfield and Xu [5,6] respectively. The C2AC3 bond length in the pyridine ring is calculated at 1.395 Å, 1.396 Å and 1.402 Å for the neutral, dimer and anion1 forms and the bond length was observed at 1.390 Å and 1.392 Å [5,6]. C13AO14 bond length was observed at 1.253 Å by Braga [10] is computed at 1.300 Å and 1.251 Å for anion1 and anion2 forms of 3,4-PDCA. As seen in Table 2, comparing of the calculated and observed bond lengths, the theoretical values (CAN and CAO) are slightly shorter than experimental ones. Also the C@O bond length of anion2 structure is closer to the experimental value than the neutral, dimer and anion1 forms of the title molecule. Other bond length in the ring also shows convenient with experimental results in general. The calculated CCC and CNC angles of the pyridine ring are good agreement with the experimental values. For examples C2AC1AN6 angle is calculated at 123.2°, 123.4° for the neutral, dimer structures and at 123.3° anion1 and anion2 forms. This angle was observed at 123.1° both by Xu et al. [6] and by Braga et al. [10]. C1AN6AC5 bond angle has been found 117.5° and 117.8° and calculated at 117.0° (for the neutral form). However, the calculated bond angles of the carboxylic groups of 3,4-PDCA are not good agreement with the experimental data. The reason may be that X-ray data presented here are pertain to complex of 3,5-PDA. The

intermolecular hydrogen bonds are almost linear. We calculated this angle and length at 178.6° and 1.703 Å. Vibrational spectra 3,4-PDCA is a molecule which has 17 atoms and therefore it has 45 vibrations. In order to obtain the spectroscopic features of 3,4-PDCA, we performed wavenumber calculation analysis. Vibrational wavenumbers are calculated for the title molecule by using the DFT/B3LYP method with the 6-311++G(d,p) basis set. The experimental and theoretical infrared and Raman spectra of 3,4-PDCA have been shown in Figs. 4 and 5, respectively. The experimental wavenumbers have been tabulated together with the calculated wavenumbers for C1 conformer in Table 3 and the theoretical wavenumbers of dimer and anion forms of the studied molecule have been tabulated in Tables S3–S4, respectively. A detailed description of the normal modes was given based on the TED in the last column. The most characteristic feature of carboxylic group is observed usually in the 1700–1800 cm1 region [17] and this band is assigned as the C@O stretching vibration. The C@O stretching vibrations were observed at 1704 cm1 in FT-IR spectrum and 1702, 1646 cm1 in FT-Raman spectrum. This band was calculated at 1679 and 1667 cm1 with contribution of 84% and 81% using DFT/6-311++G(d,p) for the most stable conformer. The C@O stretching vibration calculated at 1667 cm1 was not observed in FT-IR spectrum. Whereas, this band was shifted negative in FTRaman spectrum of 3,4-PCDA. As for dimeric conformation, because of the hydrogen bonding effect through the carboxyl groups, the C@O stretching modes of C1 dimer conformation were calculated at 1727, 1726, 1666 and 1621 cm1 and the TEDs of

Fig. 1. The geometric structures of all conformers of 3,4-PDCA molecule.


273

Fig. 2. The theoretical geometric structure of dimer structure of 3,4-PDCA molecule.

Fig. 3. The theoretical geometric structure of anion forms of 3,4-PDCA molecule.

these modes are 83%, 82%, 67% and 62%, respectively. Also this mode was calculated at 1718, 1677 cm1 and 1616, 1611 cm1 for anion1 and anion2 forms, respectively. As seen in the given values, the values belong to anion1 form were close to the experimental results than the other anion form of the molecule. For the anion2 form, the mode was significantly shifted to negative. The CAO stretching vibrations were calculated at 1360, 1266, 1133 and 1090 cm1 with contribution of 28%, 26%, 36% and 21% using DFT/6-311++G(d,p) for the most stable C1 conformer. These vibrations are observed at 1268 and 1074 cm1 in FT-IR spectrum, at 1383 and 1124 cm1 in FT-Raman spectrum. The OH vibrations in carboxylic acids are extremely sensitive to formation of hydrogen bonding. Thus the OAH stretching band is characterized by very broadband appearing near about 3400 cm1 [18]. In our work, calculated this bands at 3579 and 2992 cm1 with a contribution of 100% and 99% are pure vibrations. However, the band computed at 3579 cm1 is observed neither in FT-IR spectrum nor in FT-Raman spectrum of the studied molecule. Also, the OAH frequency is computed at 3281 (93%), 3280 (99%), 3142 (87%) and 3076 (100%) cm1 for dimeric conformation. The frequency downshifts of OH stretching vibration in dimer structure may be caused by the presence of intermolecular interaction because the occurrence of dimeric conventions is due to hydrogen bonds which act as the bridging mode. In our previous study, we calculated at 3393 and 3394 cm1 the vibration for monomer and dimer conformers of 3,5-PDA [7]. The OAH in-plane bending vibrations appear in the region 1440–1395 cm1. The OAH in-plane bending vibrations were assigned at 1443 cm1 and 1385 cm1 in FT-IR and 1446 cm1 in FT-Raman experimentally, which were calculated at 1446 and 1395 cm1 for the

structurally similar molecule [19]. In the present work, this band is observed at 1156 cm1 in FT-IR and at 1172 cm1 in FT-Raman. The OAH in-plane bending is calculated between 1430 and 1177 cm1 with B3LYP method. This band also is calculated in the range of 1454 and 1394 cm1 for dimer structure. The OAH out-of-plane bending vibration occurs in 960–875 cm1 [7,20]. We calculated the OAH out-of-plane bending vibration at 975 cm1 by using B3LYP and observed at 942 and 980 cm1 in FT-IR and FT-Raman spectra, respectively for the similar molecule [21]. In this study, the OAH out of plane bending is calculated at 850 and 784 cm1 with B3LYP method. This band is observed at 842 and 801 cm1 in FT-IR and 836 and 800 cm1 in FT-Raman. The OAH out of plane bending for dimer structure is also calculated between 942 and 744 cm1 with B3LYP method. The data available confirm the expectation that the CAH stretching modes of pyridines and quinolines will be essentially similar to those of benzene. Pyridine and picolines show CH absorptions in the range 3070–3020 cm1 [22,23]. In this study, the three adjacent hydrogen atoms around the ring of 3,4-PCDA give rise three CAH stretching vibrations, three CAH in plane bending and three CAH out of plane bending. Theoretic CAH stretching vibrations are calculated at 3090, 3070 and 3042 cm1 and calculated these bands were observed at 3087, 3070 and 3010 cm1 in FT-IR spectrum. The mode computed at 3090 cm1 is in harmony with experimental values both FT-IR (3087 cm1) and FT-Raman (3089 cm1). These vibrations with contribution of 98%, 99% and 98% are pure vibrations. In the anion and dimeric forms of the studied molecule, according to the results of monomer form, these vibrations were shifted to negative (3069, 3055, 2996 cm1 for anion1, 3019, 3006, 2939 cm1 for anion2 and 3084, 3064, 3034 cm1 for dimeric structures). In the aromatic compounds, the CAH in plane bending frequencies appear in the range of 1000–1300 cm1 and the CAH out of plane bending frequencies observe in the range of 750– 1000 cm1 [24]. In this work, the CAH in plane and out of plane bending frequencies are calculated at 1296, 1133 cm1 and 999, 945, 870 cm1, respectively. The CAH in plane vibration is observed at 1317 cm1 in FT-IR and the CAH out of plane frequency is observed at 971 cm1 in FT-IR spectrum of 3,4-PDCA. The change in the frequencies of these deformations from the values in pyridine is almost independent of their nature and is almost determined exclusively by the relative position of the substituents. Both the in-plane and out-of-plane bending modes are illustrated as mixed modes. The detailed assignment contribution of the

274


Table 1 Calculated energies and energy differences for sixteen conformers of 3,4-PDCA by DFT (B3LYP/6-311++G(d,p)) method. Point group: C1

a

Energy differencesa

Energy

Imaginary frequency

Conformers

(Hartree)

(kcal/mol)

(Hartree)

(kcal/mol)

C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16

625.62441906 625.62398534 625.62398521 625.62355669 625.62298346 625.62295918 625.62063130 625.61933095 625.61932609 625.61835281 625.61822808 625.61811438 625.61792592 625.61765780 625.61262955 625.60743300

392585.2664 392584.9942 392584.9941 392584.7252 392584.3655 392584.3503 392582.8895 392582.0736 392582.0705 392581.4598 392581.3815 392581.3101 392581.1919 392581.0236 392577.8684 392574.6075

0.0000 0.0004 0.0004 0.0009 0.0014 0.0015 0.0038 0.0051 0.0051 0.0061 0.0062 0.0063 0.0065 0.0068 0.0118 0.0170

0.0000 0.2722 0.2722 0.5411 0.9009 0.9161 2.3769 3.1928 3.1959 3.8066 3.8849 3.9562 4.0745 4.2428 7.3980 10.6589

Point group: Cs

Energy

Conformers

(Hartree)

(kcal/mol)

(Hartree)

(kcal/mol)

C1 C4 C3 C2 C5 C6 C10 C12 C13 C14 C8 C9 C7 C11 C15 C16

625.62411893 625.62298750 625.61079513 625.60999032 625.60991634 625.60868310 625.59896283 625.59707615 625.59519366 625.59197502 625.58011127 625.57982649 625.57926080 625.58121211 625.56197889 625.55040327

392585.0781 392584.3681 392576.7172 392576.2122 392576.1658 392575.3919 392569.2924 392568.1085 392566.9272 392564.9074 392557.4628 392557.2841 392556.9292 392558.1536 392546.0846 392538.8208

0.0000 0.0011 0.0133 0.0141 0.0142 0.0154 0.0252 0.0270 0.0289 0.0321 0.0440 0.0443 0.0449 0.0429 0.0621 0.0737

0.0000 0.7100 8.3608 8.8658 8.9123 9.6861 15.7857 16.9696 18.1509 20.1706 27.6152 27.7939 28.1489 26.9244 38.9935 46.2573

Energy differencesa

– – – – – – – – – – – – – – – – Imaginary frequency

1 1 2 2 2 2 2 2 1 2 2 2 2 2 3 3

(36.06) (39.05) (115.89, 65.30) (107.97, 63.42) (108.47, 64.04) (107.07, 65.82) (95.84, 45.68) (97.90, 53.90) (128.63) (144.66, 10.33) (228.64, 93.56) (202.46, 94.75) (237.71, 95.87) (207.14, 91.87) (281.48, 252.21, 70.44) (1142.07, 310.82, 73.77)

Energies of the other conformers relative to the most stable C1 conformer.

out-of-plane and in-plane vibrations indicates that out-of-plane modes are also highly pure modes according to TED. The CAN stretching frequency is very difficult task since there are problems in identifying these frequencies from other vibrations. Sundaraganesan et al. [25] assigned this band at 1689 cm1, 1302 cm1 and 1350, 936 cm1 as C@N and CAN stretching for benzimidazole, respectively. The CN stretching vibrations were observed in the range of 1162–1602 cm1 and 1185–1602 cm1 in FT-IR and FT-Raman spectra, respectively for 3,5-PDCA [8]. In the present work, this band is observed at 1405, 1268 and 1040 cm1 in FT-IR and at 1401 and 1063 cm1 in FTRaman. These bands are calculated at 1411, 1266 and 1062 cm1. For this vibration, theoretical values are in harmony with the experimental results. The ring stretching vibrations are very much important in the spectrum of pyridine and its derivatives and are highly characteristic of the aromatic ring itself. Koczon et al. [4] assigned the ring carbonAcarbon stretching vibrations in the region 1430– 1625 cm1. In the present work, the C@C stretching vibrations were calculated at 1593 and 1551 cm1 and the band calculated at 1593 cm1 was observed at 1609 cm1 in FT-IR spectrum. However, the band calculated at 1551 cm1 was not experimentally observed in FT-IR spectrum. The bands computed at 1593 and 1551 cm1 were observed at 1617 and 1536 cm1 in FT-Raman. The other CAC stretching vibrations were theoretically calculated at 1296, 1266, 1177 and 1062 cm1. These bands were observed at 1317, 1268, 1156 and 1040 cm1 in FT-IR spectrum of the studied molecule. As for FT-Raman spectrum of the molecule, these vibrations were observed at 1284, 1172 and 1063 cm1.

The correlation graphic which described harmony between the calculated and experimental wavenumbers is shown in Fig. S1. As can be seen from Fig. S1, experimental fundamentals have a very good coherence with FT-IR results. The relations between the calculated and experimental wavenumbers are linear for IR, Raman and described by the following equations:

For infrared; For Raman;

mcal ¼ 1:0007mexp þ 3:336 ðR2 ¼ 0:9996Þ

mcal ¼ 1:0186mexp 16:347 ðR2 ¼ 0:9988Þ

In consequence, the calculated fundamental vibrational are in good harmony with the experimental results especially for FT-IR. Bond distances and characteristic frequencies The molecular structure of a most stable conformation has been completely examined not only by experimental methods but also by theoretical approaches. 3,4-PDCA possess two carboxylic acid groups established one of the most popular model systems for studying inter-and intra-molecular hydrogen bonds. In order to compare the strength of inter- and intra-molecular hydrogen bonding, some pieces of evidence from geometrical and vibrational motion behavior are chosen to identify the hydrogen bonding effect. The bond distances and the characteristic frequencies of atoms within various conformers or isomers are given in Table 4. According to the calculated values, the relationships between these distances and the strengths of hydrogen bonds are discussed here. We presented flowing interpretation.

275

M. Karabacak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 270–282 Table 2 Bond lengths (Å) and bond angles (°) experimental and optimized monomer (neutral), dimer and two anions forms of 3,4-PDCA by using 6-311++G(d,p). Bond lengths (Å) C1AC2 C1AN6 C2AC3 C3AC4 C3AC13 C4AC5 C4AC10 C5AN6 C10AO11 C10AO12 O11AH16 C13AO14 C13AO15 O14AH17 CAH Ring average

X-raya

X-rayc

Monomer

Dimer

Anion1

Anion2

1.393 1.346 1.390 1.390

1.389 1.346 1.392 1.388

1.393 1.503 1.346 1.260 1.253

1.390 1.497 1.347 1.268 1.252

1.390 1.336 1.395 1.417 1.530 1.406 1.489 1.331 1.330 1.224 0.971 1.323 1.213 0.997 1.083

1.390 1.335 1.396 1.417 1.536 1.409 1.485 1.328 1.314 1.240 0.995 1.329 1.205 0.983 1.083

1.384 1.340 1.402 1.415 1.555 1.409 1.537 1.333 1.232 1.278 1.294 1.300 1.225

1.388 1.342 1.405 1.412 1.546 1.404 1.548 1.343 1.260 1.250

1.085

1.088

123.2 116.7 120.5 116.7 113.1 130.3 117.8 125.8 116.4 124.6 116.3 117.0 113.3 125.5 121.2 108.9 111.0 120.0 119.4 120.5 112.2 164.7 119.6

123.4 116.3 120.5 116.5 114.3 129.1 117.9 126.2 115.8 124.8 116.2 116.8 114.4 124.0 121.5 110.6 111.5 119.6 119.0 121.3 111.8 160.9 119.7

123.3 116.3 120.9 116.6 115.7 127.6 117.2 129.3 113.5 125.8 116.9 116.2 116.6 117.6 125.7 113.8

123.3 116.3 121.1 116.6

1.253 1.233

Bond Angles (°) C2AC1AN6 N6AC1AH7 C1AC2AC3 C2AC3AC4 C2AC3AC13 C4AC3AC13 C3AC4AC5 C3AC4AC10 C5AC4AC10 C4AC5AN6 N6AC5AH9 C1AN6AC5 C4AC10AO11 C4AC10AO12 O11AC10AO12 C10AO11AH16 C10AO12AH17 C3AC13AO14 C3AC13AO15 O14AC13AO15 C13AO14AH17 O12AH17AO14 CACAH Ring average Intermolecular H bond lengths and angles H16. . .O29 H33. . .O12 O11H16. . .O29 O28H33. . .O12 a,b,c

X-rayb

123.1

123.1

118.6 118.9

118.6 121.2 120.2 123.1

118.4 118.8 113.6 129.7 119.1 120.4 120.4 122.4

117.5 119.1 119.9 121.0 119.9

117.8 120.1 119.8 120.0 116.2

– – – –

– – – –

1.251 1.258

117.2 127.1 115.6 126.4 116.0 115.5 115.0 115.9 128.9

118.5 118.6

115.5 115.1 129.1

119.2

119.2

1.703 1.703 178.6 178.6

The X-ray data from Refs. [5,6,10].

As can be seen from Table 4, the bond length of the one of the carbonyl distance of C1 conformer is showed the longest one (dC10@O12 = 1.224 Å) and it has the one of smallest frequencies 1666 cm1 (except for C13 conformer). Also, the other carbonyl distance of C1 conformer is longer than the other conformers (except for C4 and C14 conformers). The carbonyl frequencies of C4 and C14 conformers are smaller than C1 conformer. The reason can be that the carboxyl groups of these conformers are close to one another. This bond length for similar molecules are 1.225 Å, 1.226 Å, and 1.227 Å [26–28], respectively. Similarly, vC@O frequency for these molecules are convenient (1670, 1681, and 1660 cm1). These bond length and frequency are calculated as 1.220 Å and 1672 cm1 [29]. The longest hydroxyl distance (dO14AH17 = 0.997 Å) for C1 conformer of the title molecule has the smallest frequency (vOAH = 2991 cm1) because of the O atom in O@COH of the C1 conformer, which donates electron to form with H in hydroxyl only. As to the other hydroxyl group, the distance also is longer than other conformers (except for C4, C10, C12, C14). It can be that the carboxylic groups of these conformers interaction each other. Also, a parallel result was obtained for the bond distance [26]. This bond length is 0.968 Å for a similar molecule [29].

If we consider dimer structure (inter-molecular hydrogen bonding) shown in Fig. 2 and tabulated in Table S3, we can see the interhydrogen bonding effect through the carboxyl groups. Especially, v (OH) vibration shows a large deviation between monomer and dimer conformers due to inter-molecular hydrogen bonding. These results correspond to for structurally similar molecules [26–28]. NMR spectra 1 H and 13C NMR spectroscopy can provide the required structural data for the investigated compound [30,31]. The isotropic chemical shifts are frequently used as an aid in identification of reactive ionic species. It is recognized that accurate predictions of molecular geometries are essential for reliable calculations of magnetic properties. The isotropic shielding values were used to calculate the isotropic chemical shifts with respect to TMS, x (diso ¼ rTMS iso riso ). The NMR spectra calculations were performed in DMSO solvent. The experimental and theoretical 13C and 1H chemical shifts are summarized in Table 5 and 13C and 1H spectra of 3,4-PDCA are showed in Figs. 6 and 7, respectively. Comparison between experimental and theoretical NMR chemical shifts provides practical

276


Fig. 4. Calculated and experimental Infrared spectra of 3,4-PDCA molecule.

Fig. 5. Calculated and experimental Raman spectra of 3,4-PDCA molecule.

information on the chemical structure and conformation of compounds. As can be seen in Fig. 1, the molecular structure of the title compound includes pyridine ring. This ring include nitrogen atom which shows electronegative property. On the other side, oxygen atom show electronegative property. Therefore, the chemical shift values of C10, C13 and C1, C5 have been observed at 168.28 ppm (C@O), 167.15 ppm (C@O) and 153.21, 150.35 ppm (CN) and calculated at (with respect to TMS) 178.13 ppm, 171.61 ppm and 163.39, 160.90 ppm, respectively by using DFT/B3LYP method and these results are in harmony with the information; the range of 13C NMR chemical shifts for a typical organic molecule usually is >100 ppm [26,27]. Similarly, other carbon peaks are observed at 142.12, 126.32 and 122.32 ppm and calculated at 146.47, 132.54 and 125.10 ppm for neutral form (monomer) by using DFT/B3LYP methods, respectively. Hydrogen attached or nearby electron-withdrawing atom or group can decrease the shielding and move the resonance of

attached proton towards to a higher frequency. By contrast electron-donating atom or group increases the shielding and moves the resonance towards to a lower frequency. In this study, 1 H results calculated for the hydrogen atoms of pyridine ring are higher than experimental values. Because of electronegative oxygen atoms, H17 atom is higher value than others. Its experimental value is observed at 14.27 ppm. The computed at 14.28 ppm is in harmony with experimental value. As can be seen in Table 5, the calculated chemical shifts for 1H are more sensitive as compared to that of 13C and there is a good agreement between experimental and theoretical chemical shift results (especially, for 1H values of the carboxyl groups) of the title compound. The correlation graphics between the experimental and calculated 13C NMR and 1H NMR chemical shifts of title molecule were represented in Fig. S2. The relations between the calculated and experimental chemical shifts (dexp) are usually linear and described by the following equation:

277

M. Karabacak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 270–282 Table 3 Comparison of the calculated and experimental (FT-IR and FT-Raman) vibrational spectra for C1 conformer of 3,4-PDCA using with B3LYP/6-311++G(d,p) basis set. Modes

m1 m2 m3 m4 m5 m6 m7 m8 m9 m10 m11 m12 m13 m14 m15 m16 m17 m18 m19 m20 m21 m22 m23 m24 m25 m26 m27 m28 m29 m30 m31 m32 m33 m34 m35 m36 m37 m38 m39 m40 m41 m42 m43 m44 m45 a

FT-IR

FT-Raman

3087 3070 3010

3089

1704

1702 1646 1617 1536 1492 1457 1401 1383 1284

1609

1405 1317 1268

1251 1156 1074 1040 971

842 801

1172 1124 1063 990 975 836 819 800

729 692 674 659 584 552

582 553

437

441 357 333 283 258 152 112 82

Unscaled

Scaled

TEDa (P10%)

3735 3226 3205 3176 3124 1753 1695 1621 1578 1515 1455 1436 1383 1318 1288 1271 1216 1197 1152 1109 1081 1016 962 885 865 832 798 777 755 706 682 663 587 583 490 449 411 377 338 282 272 188 104 85 43

3579 3090 3070 3042 2992 1679 1667 1593 1551 1490 1430 1411 1360 1296 1266 1250 1195 1177 1133 1090 1062 999 945 870 850 818 784 764 743 694 670 652 577 573 482 441 404 370 332 278 267 185 102 83 42

mOH (100) mCH (98) mCH (99) mCH (98) mOH (99) mC@O (84) + dCOH (24) mC@O (81) mCC (52)ring + mCN (14) + dCCH (10) + dCNH (10) mCC (40)ring + mCN (31) dCCH (45) + mCC (23) + mCN (11) dCOH (74) dCNH (38) dCCH (20) + mCN (13) + mCC (10) mCAO (28) + dCOH (28) + mC-Cring (14) dCCH (36) + mCC (18)ring mCAO (26) + mCC (20)ring + mCN (13) mCC (44) + mCN (30) + mCAO (13) mCN (23) + dCNH (18) + dCOH (10) + mCC (10) + mCO (10) dCOH (33) + dCC (18)ring + dCCH (12) mCAO (36) + mCC (29) + dCCH (17) mCAO (21) + mCC (20) + dCCN (17) + dCCC (15) mCC (24)ring + mCN (28) + dCCH (11) cCH[sCCNH (60) + sCCCH (19)] cCH[sCCCH (54) + s CCNH (21)] cCH[s CCCH (54) + sCCNH (27)] sCCOO (52) + cOH (29) dCCN (29) + mCC (23) sCCCO (43) + cOH (23) dCOH(20) + mCC (18) + dCCO (12) + dCOO (12) sCCCO (45) + cOH[sCOOH (16)] sCCCN (29) + cCH[sCCCH (17)] + sCCCO (11) dCOO (18) + dCCN (16) + dCCO (14) + dCCC (12) dCOO(32) + dCCN (16)+dCCO (11) + dCCC (10) cOH[sCCOH (39) + sCOOH (26)] dCCO (29) + cOH [sCCOH (15) + sCOOH (10)] + dCCC (10) dCCO (40) + mCC (25) sCCCO (21) + sCCCC (15) + sCCCN (14) mCC (35) + dCOO (18) sCCCN (29) + dCCO (21) + cCH[sCCCH (11)] mCACOOH (35) + dCCC (33) dCCC (80) dCCC (62) + dCCO (34) sCCCC (31) + sCCCN (17) + sCCCO (14) sCCCC (32) + sCCCO (20) sCCCO (74) + sCCCC (14) sCCCO (95)

m; stretching, d; in plane bending, c; out of plane bending, s; torsion.

Table 4 The bond distances (Å) and characteristic wavenumbers (cm1) related to C@O and OAH bonds of 3,4-PDCA. Conformers C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16

C@O bond dC10@O12

mC10@O12

Scaled freq.

dC@O bond dC13@O15

Scaled freq. mC13@O15

OAH bond dO11AH16

Scaled freq. mO11AH16

OAH bond dO14AH17

Scaled freq. nO14AH17

1.224 1.212 1.212 1.214 1.210 1.210 1.212 1.205 1.211 1.204 1.205 1.211 1.219 1.212 1.205 1.200

1666 1677 1677 1674 1684 1679 1677 1711 1680 1707 1712 1677 1650 1681 1710 1735

1.213 1.207 1.207 1.221 1.209 1.208 1.205 1.211 1.204 1.210 1.209 1.203 1.211 1.216 1.207 1.206

1678 1696 1696 1638 1689 1697 1716 1685 1719 1682 1690 1716 1685 1662 1704 1696

0.971 0.970 0.970 0.993 0.971 0.971 0.970 0.968 0.970 0.972 0.968 0.977 0.968 0.988 0.968 0.970

3577 3590 3590 3078 3576 3582 3590 3619 3586 3567 3615 3413 3616 3180 3620 3586

0.997 0.972 0.972 0.972 0.971 0.972 0.968 0.971 0.968 0.978 0.971 0.973 0.992 0.968 0.968 0.969

2991 3569 3569 3572 3582 3573 3616 3587 3613 3778 3581 3562 3110 3608 3619 3573

dcal ðppmÞ ¼ 1:0485dexp 0:1415 ðR2 ¼ 0:9992Þ

For13 C; dcal ðppmÞ ¼ 1:0886dexp 6:1147 ðR2 ¼ 0:9802Þ

In the present study, the following linear relationships were obtained for 13C and 1H chemical shifts.

For1 H; dcal ðppmÞ ¼ 0:935dexp þ 1:0312 ðR2 ¼ 0:9828Þ

278


Table 5 Experimental and theoretical, 1H and 13C NMR isotropic chemical shifts (with respect to TMS) of neutral and dimer forms of 3,4-PDCA by DFT (B3LYP/6-311++G(d,p) method. Atoms

C(1) C(2) C(3) C(4) C(5) C(10) C(13)

Carbon

Atoms

Exp.

Neutral

Dimer

153.21 126.32 142.12 122.32 150.35 168.28 167.15

163.39 132.54 146.47 125.10 160.90 178.13 171.61

163.65 132.15 148.34 125.79 160.15 182.93 170.18

H(7) H(8) H(9) H(16) H(17)

Hydrogen Exp.

Neutral

Dimer

8.78 7.58 8.95 7.26 14.27

9.25 8.42 9.72 7.28 14.28

9.36 8.35 9.68 13.24 12.77

As a result of all of these, the performances of the B3LYP method with respect to the prediction of the relative shielding within the molecule were nearly close and the calculated chemical shifts are in good harmony with the experimental results especially for 1H.

UV spectrum and Frontier molecular orbital analysis Ultraviolet spectra analyses of 3,4-PDCA are researched by theoretical calculation and experiment. The electronic absorption

Fig. 6.

13

spectrum of the title molecule is measured in ethanol. The excitation energies, absorbance and oscillator strengths for the title molecule at the optimized geometry are obtained in the framework of DFT calculations by using the B3LYP/6-311++G(d,p) method. The UV spectra (experimental and theoretical) of 3,4-PDCA are shown in Fig. 8. The predicted UV spectra results are depicted in Table 6 such as absorption wavelengths (k), excitation energies (E), oscillator strengths (f), and major contributions of the transitions and assignments of electronic transitions. From the experimental and theoretical UV spectra, the absorption band is centered at 268.51 nm (calculated 234.54 nm) for 3,4-PDCA. The HOMO and LUMO are named as frontier molecular orbitals (FMOs). The FMOs play an important role in the optical and electric properties, as well as in quantum chemistry and UV–Vis spectra [32]. Gauss-Sum 2.2 Program [33] was used to calculate group contributions to the molecular orbitals (HOMO and LUMO). The HOMO presents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron. The energy gap between HOMO and LUMO determines the chemical potential, electronegativity, electrophilicity index and chemical hardness– softness of a molecule. The plots of MOs have been drawn and given in Fig. 9. As can be seen from Fig. 9, the energy gap between HOMO and LUMO is

C NMR spectrum of 3,4-PDCA.

Fig. 7. 1H NMR spectrum of 3,4-PDCA.


279

v ¼ l where I and H are ionization potential and electron affinity of a molecular system. Mulliken atomic charges The computation of the reactive atomic charges plays an important role in the application of quantum mechanical calculations for the molecular system. Mulliken atomic charges are calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. To make comparison, the Mulliken atomic charges of 3,4-PDCA, Pyridine, 3-PCA and 4-pyridinecarboxylic acid (4-PCA) (these molecules have a similar structure with 3,4-PDCA) are tabulated in Table S5 and shown in Fig. S3. We plotted the graph of these values as shown in Fig. S4. Also, to make comparison between neutral and anion forms, the Mulliken atomic charges of these forms are given in Table S6. All hydrogen atoms have a net positive charge. For 3,4-PDCA, the maximum negative charges belong to C5 atom and the value is 0.592. The maximum positive charge belonging to C3 atom is 0.961. The charge of C3 of 3-PCA having a carboxylic acid on C3 atom as 3,4-PDCA molecule is quite low and this worth was 0.108. The N atom of 3,4-PDCA has 0.066 negative charge. The biggest negative charge on N atom belongs to Pyridine (except for 3,5-PDCA). In molecules except for pyridine, while the charges on C atoms of carboxylic acid groups are negative, only the charge on C13 atom of 3,4-PDCA molecule is positive (except for 3,5-PDCA). Molecular electrostatic potential (MEP) Fig. 8. Theoretical and experimental UV spectra of 3,4-PDCA.

11.0560 eV for 3,4-PDCA molecule. From Table 6, the largest contribution to charge transition in 234.54 nm (theoretical value) is from the HOMO to the LUMO with 90%. The largest contribution for 219.18 nm is belonged to transitions which H 1 ? L with 50% and H ? L + 4 with 25%. Also, in 213.87 nm, H 2 ? L transition has the contribution with 67%. The other electronic properties as the chemical potential (l), electronegativity (v), electrophilicity index (x) and chemical hardness (g) have given in Table 7. The v, g and l are important tools to study the order of stability of molecular systems. Using HOMO and LUMO energies, the g and l have been calculated. The chemical hardness and the chemical potential are given by the following expression,

g ¼ ðI HÞ=2

l ¼ ðI þ HÞ=2 The x, which measures the stabilization energy, has been given by the following expression, in terms of electronic chemical potential and the chemical hardness:

x ¼ l2 =g electronegativity (v),

v ¼ ðI þ HÞ=2 or

The MEP is a useful feature to study reactivity given that an approaching electrophile will be attracted to negative regions (where the electron distribution effect is dominant). The importance of MEP lies in the fact that it simultaneously displays molecular size, shape as well as positive, negative and neutral electrostatic potential regions in terms of color grading and is very useful in research of molecular structure with its physicochemical property relationship [34,35]. The resulting surface simultaneously displays molecular size, shape and electrostatic potential value. In the majority of the MEP, while the maximum negative region which preferred site for electrophilic attack indications as red color, the maximum positive region which preferred site for nucleophilic attack symptoms as blue color. The different values of the electrostatic potential at the surface are represented by different colors. Potential increases in the order red < orange < yellow < green < blue. In this study, the color code of the map is in the range between 0.09538 a.u. (deepest red) and 0.09538 a.u. (deepest blue) in the studied compound, where blue indicates the strongest attraction and red indicates the strongest repulsion. The MEPs of 3,4-PDCA molecule in 3D and 2D contour plots are represented in Fig. 10. As can be seen from the MEP map shown in figure, although the regions having the negative potential are over oxygen atoms (the electronegative atoms) belong to the carboxylic group on C3 atom, the oxygen atoms of the other carboxylic group have the positive potential region and also the regions

Table 6 Experimental and theoretical wavelengths k (nm), excitation energies (eV) and oscillator strengths (f) in ethanol solution of 3,4-PDCA. Experimental

Theoretical

Major contribution (P10%)

k (nm)

E (eV)

k (nm)

E (eV)

f

268.51

4.61

204.59

6.06

234.54 219.18 213.87

5.2863 5.6557 5.7971

0.2393 0.0281 0.0042

H; HOMO, L; LUMO.

H ? L (90%) H 1 ? L (50%), H ? L + 4 (25%) H 2 ? L (67%)

280


atom) indicate the strongest attraction and O14 and O15 atoms indicate the strongest repulsion. Thermodynamic properties Thermodynamical parameters such as the zero-point vibrational energies (ZPVE), the entropy, the heat capacity, rotational constants and dipole moment were computed and the results are presented in Table S7 for neutral (monomer), dimer and anion forms. In the different temperature, the standard statistical thermodynamic functions: heat capacity, entropy and enthalpy changes for the compound are obtained from the theoretical harmonic frequencies and listed in Table S8. It can be observed that these thermodynamic functions are increasing with temperature ranging from 100 to 700 K due to the fact that the molecular vibrational intensities increase with temperature. The correlation equations between heat capacity, entropy, enthalpy changes and temperatures are fitted by quadratic formulas. The corresponding fitting factors (R2) for these thermodynamic properties are 0.9994 (for heat capacity), 0.9999 (for entropy) and 0.9998 (for enthalpy), respectively. The corresponding fitting equations are as follows and the correlation graphics of those shows in Fig. 11.

C ¼ 0:9964 þ 0:1364T 6 105 T 2

ðR2 ¼ 0:9994Þ

S ¼ 56:178 þ 0:1537T 4 105 T 2

ðR2 ¼ 0:9999Þ

Fig. 9. The frontier molecular orbitals of 3,4-PDCA.

H ¼ 0:4781 þ 0:011T þ 4 105 T 2 Table 7 The calculated energy values of 3,4-PDCA molecule using DFT/B3LYP method using 6311++G(d,p) basis set. DFT/B3LYP/6-311++G(d,p)

Gas

Ethanol

Etotal (Hartree) EHOMO (eV) ELUMO (eV) EHOMO–LUMO gap (eV) Chemical hardness (g) Electronegativity (v) Chemical potential (l) Electrophilicity index (x)

623.9874711 10.56 0.58 11.14 5.57 4.99 4.99 2.24

622.0967124 10.29 0.77 11.06 5.53 4.76 4.76 2.05

having the positive potential are over H16 atom localized a maximum positive region. From these results, we can say that the ring, the nitrogen atom and all hydrogen atoms (especially H16

ðR2 ¼ 0:9998Þ

Nonlinear optical (NLO) effects In the recent years, a large number research of new materials exhibiting efficient NLO properties has been of great interest because of potential applications in modern communication technology, telecommunication, and optical signal processing [36–40]. It is known that the significance of the polarizability and the first hyperpolarizability of molecular systems is dependent on the efficiency of electronic communication between acceptor and the donor groups as that will be the key to intra molecular charge transfer [41,42]. The acceptor and donor groups have an important role in the polarizability and first hyperpolarizability. The big value of the first hyperpolarizability measured of the NLO activity of the molecular system is associated with the resulting from the electron

Fig. 10. The molecular electrostatic potential 3D map and 2D contour map for 3,4-PDCA molecule.


281

We calculated lo, ao, Da bo values of 3,4-PDCA as 5.780 Debye, 19.950 1024 esu, 43.314 1024 esu and 3401.10 1033 esu, respectively. Conclusions

Fig. 11. Correlation graphic between entropy, heat capacity, enthalpy and temperature of 3,4-PDCA molecule.

cloud movement through p conjugated frame work from electron donor to electron acceptor groups [43]. The polar properties of the title molecule were calculated at the DFT/B3LYP/6-311++G(d,p) level. The components of the dipole moments l (Debye), static polarizability components a (a.u.), the average polarizability (or linear polarizability) ao (1024 esu), the anisotropy of the polarizability, Da (Å), and the first hyperpolarizability components b (a.u.), the first hyperpolarizability bo (1033 esu) of 3,4-PDCA can be seen in Table 8. The lo, ao, Da, b and bo of the title molecule can be calculated by using the following equations, respectively [41,44]. 1=2

lo ¼ ðl2x þ l2y þ l2z Þ ao ¼

In this work, we have performed the experimental and theoretical vibrational analysis of 3,4-PDCA. Based on calculated energy differences, the C1 conformer is found to be most the stable conformer. Also, dimer and anion forms of the 3,4-PDCA is studied. Intermolecular and intramolecular hydrogen bonding between H and O is investigated in monomer and dimer structures of C1 conformer. The molecular geometry, vibrational frequencies, FT-IR and FT-Raman spectra of the molecule in the ground state are calculated by using DFT (B3LYP) method 6-311++G(d,p) basis set. The vibrational wavenumbers are calculated and the complete assignments are performed on the basis of the TED of the vibrational modes. The results are compared with experimental FT-IR and FT-Raman spectra. The correlation graphic is plotted to see the harmony between the calculated and experimental wavenumbers and the graphic showed a very good coherence with FT-IR results. UV spectral analyses are performed and HOMO–LUMO gap is calculated as 11.0560 eV. Also, we have performed 1H and 13C chemical shifts analysis and electronic analysis of 3,4-PDCA. The positions of hydrogen and carbon atoms of the title molecule are determined with help of the computed 1H and 13C NMR chemical shifts. Additionally, the thermodynamic and the electronic properties of the studied compound are calculated. Also, thermodynamic properties in the range from 100 to 700 K are obtained. As a result, this study made for 3,4-PDCA gave us a full work related to the geometry, vibrational properties (based on FT-IR, FT-Raman), electronic transitions, proton and carbon NMR shielding (based on NMR spectra), atomic charge distributions, thermodynamic properties and MEP. Acknowledgement

ðaxx þ ayy þ azz Þ 3

i1=2 1 h Da ¼ pffiffiffi ðaxx ayy Þ2 þ ðayy azz Þ2 þ ðazz ayy Þ2 þ 6a2xx 2

This work was supported by the Celal Bayar University Research fund through research Grant no. FBE-2011/70. Appendix A. Supplementary material

bx ¼ ðbxxx þ bxyy þ bxzz Þ by ¼ ðbyyy þ bxxy þ byzz Þ

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.06.130.

bz ¼ ðbzzz þ bxxz þ byyz Þ

References

1=2

bo ¼ ðb2x þ b2y þ b2z Þ

Table 8 The dipole moment, the polarizability a (a.u.), the average polarizability ao (1024 esu), the anisotropy of the polarizability Da (1024 esu), and the first hyperpolarizability b (1033 esu) of 3,4-PDCA.

lx ly lz lo axx axy ayy axz ayz azz ao Da

5.324 2.250 0.469 5.780 23.699 0.488 25.368 0.587 0.358 10.783 19.950 43.314

bxxx bxxy bxyy byyy bxxz bxyz byyz bxzz byzz bzzz bx by bz bo

981.790 0.108 1994.098 3725.024 480.735 38.104 403.842 65.587 464.312 122.330 946.721 3260.604 199.222 3401.104

[1] J.L. York, in: T.M. Delvin (Ed.), Textbook of Biochem. with Clinical Correlations, Wiley, New York, 1992, p. 135. [2] J.R.J. Sorensen, in: H. Sigel (Ed.), Metal Ions in Biological Systems, vol. 14, Marcel Decker, New York, 1982, p. 77. [3] K. McCann, J. Laane, J. Mol. Struct. 890 (2008) 346–358. [4] P. Koczon, J. Cz. Dobrowolski, W. Lewandowski, A.P. Mazurek, J. Mol. Struct. 655 (2003) 89–95. [5] T. Whitfield, L. Zheng, X. Wang, A.J. Jacobson, Solid State Sci. 3 (2001) 829–835. [6] H. Xu, N. Zheng, Y. Wu, R. Yang, E. Ye, X. Jin, J. Mol. Struct. 606 (2002) 117–122. [7] A. Nataraj, V. Balachandran, T. Karthick, M. Karabacak, A. Atac, J. Mol. Struct. 1027 (2012) 1–14. [8] E. Kose, F. Bardak, A. Atac, M. Karabacak, M.A. Cipiloglu, Spectrochim. Acta A 114 (2013) 38–45. [9] H.S. Wang, W. Shi, B. Zhai, J.-G. Ma, J. Xia, P. Cheng, J. Mol. Struct. 833 (2007) 102–107. [10] D. Braga, L. Maini, C. Fagnano, P. Taddei, M.R. Chierotti, R. Gobetto, Chem. Eur. J. 13 (2007) 1222–1230. [11] N. Sundaraganesan, S. Illakiamani, H. Saleem, P.M. Wojciechowski, D. Michalska, Spectrochim. Acta 61A (2005) 2995–3001. [12] J. Baker, A.A. Jarzecki, P. Pulay, J. Phys. Chem. A102 (1998) 1412–1424. [13] P. Pulay, J. Baker, K. Wolinski, GreenAcres Road, Suite A, Fayettevile, AR 72703, USA, 2013. [14] A.D. Becke, J. Chem. Phys. 98 (1993) 5648–5653. [15] G. Keresztury, S. Holly, J. Varga, G. Besenyei, A.Y. Wang, J.R. Durig, Spectrochim. Acta A 49A (13–14) (1993) 2007–2026.

282


[16] K. Wolinski, J.F. Hinton, P. Pulay, J. Am. Chem. Soc. 112 (1990) 8251–8260. [17] G. Socrates, Infrared and Raman Characteristic Group Frequencies, John Wiley, New York, 2001. [18] D. Lin-Vein, N.B. Colthup, W.G. Fateley, J.G. Grasselli, The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules, Academic Press, San Diego, 1991. [19] M. Karabacak, E. Köse, M. Kurt, J. Raman Spectrosc. 41 (2010) 1085–1097. [20] M. Karabacak, M. Çınar, M. Kurt, J. Mol. Struct. 885 (2008) 28–35. [21] M. Karabacak, M. Kurt, Spectrochim. Acta A 71 (2008) 876–883. [22] L. Marion, D.A. Ramsay, R.N. Jones, J. Am. Chem. Soc. 73 (1951) 305–308. [23] E.A. Coulson, J.L. Hales, E.F.G. Herington, J. Chem. Soc. (1951) 2125–2128. [24] M. Silverstein, G.C. Basseler, C. Morill, Spectrometric Identification of Organic Compounds, Wiley, New York, 1981. [25] N. Sundaraganesan, S. Ilakiamani, P. Subramanian, B.D. Joshua, Spectrochim. Acta 67A (2007) 628–635. [26] A.R. Choudhury, T.N. Guru Row, Acta Cryst. E60 (2004) 1595–1597. [27] Z. Liu, Y. Qu, M. Tan, H. Zhu, Acta Cryst. E60 (2004) 1310–1311. [28] S. Long, M. Siegler, T. Li, Acta Cryst. E63 (2007) 279–281. [29] M. Karabacak, E. Kose, A. Atac, Spectrochim. Acta A 91 (2012) 83–96. [30] K.L. Jayalakshmi, B.T. Gowda, Z. Naturforsch, Acta Cryst. 59A (2004) 491–500. [31] B.T. Gowda, S. Foro, H. Fuess, Acta Cryst. E63 (2007) 2338. [32] I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1976.

[33] N.M. O’Boyle, A.L. Tenderholt, K.M. Langer, J. Comput. Chem. 29 (2008) 839– 845. [34] J.S. Murray, K. Sen, Molecular Electrostatic Potentials, Concepts and Applications, Elsevier, Amsterdam, 1996. [35] E. Scrocco, J. Tomasi, in: P. Lowdin (Ed.), Advances in Quantum Chemistry, Academic Press, New York, 1978. [36] D. Sajan, L. Josepha, N. Vijayan, M. Karabacak, Spectrochim. Acta A 81 (2011) 85–98. [37] M. Cinar, A. Coruh, M. Karabacak, Spectrochim. Acta A 83 (2011) 561–569. [38] D.S. Chemia, J. Zyss, Non Linear Optical Properties of Organic Molecules and Crystal, Academic Press, New York, 1987. [39] J. Zyss, Molecular Non Linear Optics, Academic Press, Boston, 1994. [40] A. Ben Ahmed, H. Feki, Y. Abid, C. Minnot, Spectrochim. Acta A 75 (2010) 1315– 1320. [41] M. Karabacak, L. Sinha, O. Prasad, Z. Cinar, M. Cinar, Spectrochim. Acta A 93 (2012) 33–46. [42] K. Amila, K.M. Jeewandara, S. de Nalin, J. Mol. Struct. Theochem. 686 (2004) 131. [43] N. Sundaraganesan, J. Karpagam, S. Sebastian, J.P. Cornard, Spectrochim. Acta A 73 (2009) 11–19. [44] D. Sajan, J. Hubert, V.S. Jayakumar, J. Zaleski, J. Mol. Struct. 785 (2006) 43–53.

Molecular structure investigation of organic cocrystals of 1,10-phenanthroline-5,6-dione with aryloxyacetic acid: a combined experimental and theoretical study.

A combined experimental and theoretical analysis on molecular structure and vibrational spectra of 2,4-dihydroxybenzoic acid.

Electrocyclic reactions of siloles: a combined experimental and theoretical study.

Molecular and electronic structure of nonradical homoleptic pyridyl-azo-oxime complexes of cobalt(III) and the azo-oxime anion radical congener: an experimental and theoretical investigation.

A combined theoretical and experimental study of the influence of different anion ratios on lithium ion dynamics in ionic liquids.

The molecular structure of methylfluoroisocyanato silane: a combined microwave spectral and theoretical study.

A combined theoretical and experimental study for silver electroplating.

A Combined Experimental and Theoretical Study on Circular Dichroisms of Staggered and Eclipsed Forms of Dimethoxy[2.2]-, [3.2]-, and [3.3]Pyridinophanes and Their Protonated Forms.

Comparative study of water reactivity with Mo₂O(y)⁻ and W₂O(y)⁻ clusters: a combined experimental and theoretical investigation.

Thiocyanate-free cyclometalated ruthenium(II) sensitizers for DSSC: a combined experimental and theoretical investigation.

Effect of hydration on the kinetics of proton-bound dimer formation: experimental and theoretical study.

Anion encapsulation and geometric changes in hepta- and hexanuclear copper(I) dichalcogeno clusters: a theoretical and experimental investigation.

Analysis of the near-edge X-ray-absorption fine-structure of anthracene: a combined theoretical and experimental study.

Structural and spectral properties of a zinc(II) coordination polymer: a combined experimental and theoretical study.

Equation of state of zircon- and scheelite-type dysprosium orthovanadates: a combined experimental and theoretical study.

Fluoride Anion Recognition by a Multifunctional Urea Derivative: An Experimental and Theoretical Study.

Study of the diradicaloid character in a prototypical pancake-bonded dimer: the stacked tetracyanoethylene (TCNE) anion dimer and the neutral K(2)TCNE(2) complex.

Adsorption and desorption of U(VI) on functionalized graphene oxides: a combined experimental and theoretical study.

Valence and Conduction Band Densities of States of Metal Halide Perovskites: A Combined Experimental-Theoretical Study.

A combined experimental and theoretical study of the Ti2 + N2O reaction.

Mechanistic insight into the copper-catalyzed phosphorylation of terminal alkynes: a combined theoretical and experimental study.

Double role of the hydroxy group of phosphoryl in palladium(II)-catalyzed ortho-olefination: a combined experimental and theoretical investigation.

Communication: Remarkable electrophilicity of the oxalic acid monomer: an anion photoelectron spectroscopy and theoretical study.

A combined theoretical and experimental investigation on the solvatochromism of ESIPT3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde.