Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814

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CAH


Pd interactions: One dimensional heteropolynuclear complexes Elvan Sayın a, Günesß Süheyla Kürkçüog˘lu b,⇑, Okan Zafer Yesßilel c, Tuncer Hökelek d a

Eskisßehir Osmangazi University, The Institute of Science, Department of Physics, TR-26480 Eskisßehir, Turkey Eskisßehir Osmangazi University, Faculty of Arts and Sciences, Department of Physics, TR-26480 Eskisßehir, Turkey c Eskisßehir Osmangazi University, Faculty of Arts and Sciences, Department of Chemistry, TR-26480 Eskisßehir, Turkey d Hacettepe University, Faculty of Engineering, Department of Physics, TR-06800 Beytepe Ankara, Turkey b

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

 1D heteropolynuclear three cyanide

complexes were synthesized and characterized.  The complexes 1–3 were extended into 2D and 3D by OAH


N and p


p interactions.  The crystal structure of the complexes 1–3 exhibit intermolecular CAH


Pd interactions.

a r t i c l e

i n f o

Article history: Received 1 April 2014 Received in revised form 13 May 2014 Accepted 22 May 2014 Available online 12 June 2014 Keywords: Tetracyanopalladate(II) complexes 2-Pyridineethanol complexes CAH


Pd interactions Heteronuclear complexes Cyanide-bridged complexes One dimensional complexes

a b s t r a c t Three cyanide complexes, [Cu(hepH)2Pd(l-CN)2(CN)2]n (1), [Zn(hepH)2Pd(l-CN)2(CN)2]n (2) and [Cd(hepH)2Pd(l-CN)2(CN)2]n (3) (2-pyridineethanol abbreviated to hepH), have been synthesized and characterized by various techniques (elemental analysis, FT-IR and Raman spectroscopy, thermal analysis and single crystal X-ray diffraction). FT-IR spectroscopy pointed out the existence of terminal and bridged cyanide ligands in the complexes. The crystallographic analyses reveal that complexes 1 and 2 crystallize in the triclinic system, space group P 1 and complex 3 crystallizes in the monoclinic system, space group P21/n. The palladium atom is coordinated with cyanide-carbon atoms in a square-planar arrangement and the metal(II) atoms are six-coordinated with two cyanide nitrogen, two hepH nitrogen and two hepH oxygen atoms, in a distorted octahedral arrangement. In all the complexes adjacent chains are connected by CAH


Pd, p


p and OAH


N hydrogen bonding interactions to form two- and threedimensional networks. When it comes to thermal analysis, the complexes followed usual decomposition mechanism in which neutral ligands (hepH) are released first, and then cyanide ligands are decomposed. The final decomposition products are found to be the corresponding metal oxides. Ó 2014 Elsevier B.V. All rights reserved.

Introduction Cyanide ligand is versatile due to the nature from its ability to act as both a r-donor and a p-acceptor, its negative charge, and ⇑ Corresponding author. Tel.: +90 222 2393750; fax: +90 222 2393578. E-mail address: [email protected] (G.S. Kürkçüog˘lu). http://dx.doi.org/10.1016/j.saa.2014.05.094 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

its ambidentate feature [1]. In addition, cyanide is an influential ligand for stabilization and the entity of one (1D), two (2D), or three dimensional (3D) structures. Therefore, cyanide complexes have an area of active research because of their areas of usage depending upon the metal center and ancillary ligand used. Among the cyanide anions, the tetracyanopalladate(II) anion [Pd(CN)4]2 used in the syntheses of the cyanide complexes, is an

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E. Sayın et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814

Fig. 1. The FT-IR spectra of K2[Pd(CN)4]
H2O, free hepH and complexes 1–3.

ideal building block that has rarely been studied [2–5]. Squareplanar geometry tetracyanopalladate(II) anions have attracted attention as catalysts in CAC coupling reactions [6]. Since palladium complexes display a behavior as catalyst such as the Suzuki–Miyaura and the Heck–Mizoroki coupling reactions [7–9], cyanide complexes containing palladium central atoms can be used to increase the yield of these reactions. Among the bonding interactions of the cyanide group, hydrogen bonds can also be included. These hydrogen bonds are played an important role in packing and stabilizing the structures formed, and sometimes they are played an important role as a possible exchange path for magnetic interactions [10]. The CAH


M interactions are relevant with d8 systems and considered to be of importance for understanding the catalytic reactions [11]. These CAH


M interactions are best described as the three-center four electrons (3c–4e). However, the nature of the apical CAH


M interactions in the square-planar complexes of d8 metal ions is very rare [12,13]. The face-to-face p


p interaction, where most of the ring-plane area overlaps, is a rare interaction. 2-Pyridineethanol is a good choice in this respect for being able to coordinate itself as chelating or bridging ligand, as well as for possessing OH groups able to participate in hydrogen bondings. In our previous study, we have reported the tetracyanonickelate(II) complexes with hepH [14]. To the best of our knowledge, neither crystallographic, nor vibrational analysis study of tetracyanopalladate(II) with hepH has been reported yet. As a continuation of our previous study, we carried out the syntheses of [Cu(hepH)2Pd(CN)4]n (1), [Zn(hepH)2Pd(CN)4]n (2) and [Cd(hepH)2Pd(CN)4]n (3) cyanide-bridged coordination polymers with hepH ligand. We report herein their crystal structures, and also their vibrational, thermal and elemental analyses results. According to the obtained results, in complexes 1–3, the adjacent planes are

held together by CAH


Pd, p


p and OAH


N interactions, forming two- and three-dimensional networks. Experimental Materials All materials such as copper(II) chloride dihydrate (CuCl2
2H2O, 99%), zinc(II) chloride (ZnCl2, 96%), cadmium(II) chloride hemi (pentahydrate) (CdCl2
2.5H2O, 81%), Palladium(II) chloride (PdCl2, 99%), Potassium cyanide (KCN, 96%) and 2-pyridineethanol (C7H9NO, 98%) were used as received. Syntheses of the complexes To water solution of PdCl2 (0.177 g, 1 mmol) was added a solution of KCN (0.260 g, 4 mmol) in water (10 mL) solution and K2[Pd(CN)4]
H2O was formed as crystallized. K2[Pd(CN)4]
H2O (0.306 g, 1 mmol) to which was added solid metal chloride (CuCl2
2H2O = 0.170 g, ZnCl2 = 0.136 g or CdCl2
2.5H2O = 0.228 g, 1 mmol) became M[Pd(CN)4]
H2O. To M[Pd(CN)4]
H2O (Cu[Pd (CN)4]
H2O = 0.292 g, Zn[Pd(CN)4]
H2O = 0.293 g or Cd[Pd(CN)4]
H2O = 0.340 g; 1 mmol) solution, hepH (0.246 g, 2 mmol) dissolved in ethanol (10 mL) was added a few drops with continuous stirring approximately for 4 h at 55 °C in a temperature-controlled bath, and then filtered. The resultant solutions were filtered and kept for crystallization at room temperature. The suitable crystals for X-ray measurements were formed by slow evaporation after a week. The freshly prepared complexes were analyzed for C, H and N with the following results: Anal. Calcd. for C18H18N6O2PdCu (1) (Mw = 520.32 g mol 1): C, 41.48; H, 3.49; N, 16.15%. Found: C,

E. Sayın et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814

805

Fig. 2. The Raman spectra of K2[Pd(CN)4]
H2O and complexes 1–3.

41.55; H, 3.47; N, 16.19%. Anal. (Mw = 522.17 g mol 1): C, 40.60; 41.40; H, 3.47; N, 16.09%. Anal. (Mw = 569.19 g mol 1): C, 37.97; 37.98; H, 3.19; N, 14.76%.

Calcd. for C18H18N6O2PdZn (2) H, 3.60; N, 16.64%. Found: C, Calcd. for C18H18N6O2PdCd (3) H, 3.30; N, 14.81%. Found: C,

Physical measurements Elemental analyses (C, H and N) were carried out by standard methods using a CHNS-932 (LECO) analyzer at the Middle East Technical University Central Laboratory in Ankara, Turkey. FT-IR spectra of hepH and the complexes were carried out at room temperature by a Perkin–Elmer FT-IR 100 spectrometer in the region of 4000–250 cm 1. Resolution was set up to 4 cm 1, signal/noise ratio

was established by 16 scans with ATR (Attenuated Total Reflection). The thermogravimetric analysis (TG), differential thermal analysis (DTA), and derivative thermogravimetric analysis (DTG) measurements were carried out using a Perkin Elmer Diamond TG/DTA Thermal Analysis instrument under static air atmosphere at a heating rate of 10 K min 1 in the temperature range of 30–700 °C using platinum crucibles. Crystallographic analysis Crystallographic data were recorded on a Bruker Kappa APEXII CCD area-detector diffractometer using Mo Ka radiation (a = 0.71073 Å) at T = 100 (for 1 and 2) and 292 (for 3) K. Absorption corrections by multi-scan [15] were applied. Structures were solved

806

Table 1 The FT-IR and Raman wavenumbers of the hepH and the complexes (cm

1

).

Assignments (PED %) [14]

hepH

1

Experimental (liquid)

dring(CH2) (72) d(CH) (16) + m(NC) (19) + d(HCN) (33) d(CH2) (75) d(CCH) (51) d(COH) (13) + d(CH2) (19) + t(CCCH) (41) d(COH) (19) + d(CH2) (34) + t(CCCH) (10) d(CCH) (33) + d(HCN) (26) d(COH) (20) + t(CCCH) (29) m(NC) (29) + d(HCN) (12) + d(CCH) (15) m(NC) (39) + t(CCCH) (10) d(CC) (24) + d(CCH) (12) + d(CNC) (10) m(CC) (11) + d(CCH) (74) d(COH) (16) + d(CCH) (20) m(CC) (12) + d(CCH) (21) m(CC) (49) m(OC) (87) m(CC) (49) m(CC) (38) + d(HCO) (10) t(CCCH) (48) + t(HCCN) (17) + t(CCCC) (12) m(CN) (10) + m(CC) (11) + d(CCH) (25) t(HCCC) (13) + t(HCCN) (54) + t(CCCN) (14) t(HCCC) (48) + t(HCCN) (24) m(CC) (22) + d(NCC) (11) + d(CCC) (23) t(HCCC) (47) t(HCCC) (13) + t(HCCN) (30) + t(CCCC) (12) + t(CCCN) (11) + t(CNCC) (19) d(CCC) (17) + d(NCC) (32) + d(CCN) (17) d(CCC) (17) + d(NCC) (32) + d(CNC) (17) d(CCC) (24) + d(CNC) (15) t(HCCC) (13) + t(CNCC) (35) t(HCCC) (18) d(CCN) (55) m(CC) (15) + t(HOCC) (15) + d(OCC) (32) t(HOCC) (76) d(CCC) (23) + t(CCCC) (14)

Raman

3382 m 3087 vw 3071 vw 3013 m 2954 m 2929 m 2904 vw 2870 m 1593 s 1569 m 1506 vw 1476 s 1435 s 1417 sh 1370 m 1337 sh 1316 vw 1301 w 1278 sh 1241 m 1223 w 1150 m 1099 m – 1048 s 1002 s 993 sh – 966 vw 952 w 940 sh 890 m 862 m 781 sh 750 vs 728 sh 632 m 585 s 505 m 403 m 357 m 336 sh 285 m 254 m

– 3075 vw – 3024 vw 3008 vw 2925 vw – – 1582 m 1554 w – 1460 sh – – 1392 vs 1320 sh 1295 sh – – 1234 m – 1193 vw 1113 w – 1065 s 1011 s – – 971 vw 968 vw 925 vw 852 w 822 vw 793 m 765 sh 645 m 623 sh 588 m 477 vw 417 vw 350 sh 335 vw 283 m –

3

FT-IR

Raman

FT-IR

Raman

FT-IR

Raman

3677 3066 3055 3020 2971 2951 2911 2900 1610 1591 1495 1485 1466 1446 1392 1364 1325 1304 1289 1263 1226 1161 1138 1104 1056 1038 1023 1004 997 996 966 894 844 786 770 752 640 613 510 411 364 344 292 259

3170 s – 3086 sh 2958 w 2946 w 2925 w 2888 w 2842 m 1607 m 1571 m 1507 sh 1488 m 1475 m 1446 s 1373 sh 1353 w 1311 m 1278 vw 1266 vw 1247 w 1228 w 1163 w 1116 s 1073 m 1038 s 1026 m 998 w – 965 m – – 892 vw 866 m 784 m 766 s 698 m 648 m 583 m 507 m 402 s 351 w 327 sh 287 w 264 m

– 3090 vw – 3016 vw – 2953 m 2926 vw 2870 m 1618 m 1584 m 1551 vw 1490 vw – 1459 w 1394 vw 1330 m 1289 vw – – 1241 m 1201 m 1197 vw 1078 m – 1031 m 1009 vw 997 vw – 981 w 952 vw 933 vw 871 vw 856 vw 798 w 772 vw 657 w – 589 w 525 m – 334 m 317 m 272 m –

3065 m – – 2969 vw 2942 w 2927 w 2903 w 2853 m 1608 m 1572 m – 1488 m 1446 m 1421 sh 1359 m 1340 m 1312 m 1281 vw – 1251 w 1228 vw 1162 w 1115 m 1074 s 1032s 1021 m 1003 w – 966 w 954 w – 893 w 862 m 783 m 750 s 708 sh 644 vw 584 m 517 m 398 vw 363 w 330 vw 293 w –

– 3075 w – – – 2960 vw 2939 vw – 1621 w 1583 w 1556 vw 1487 w 1500 vw 1435 w 1385 w 1348 m 1302 vw – 1282 vw 1239 m – 1188 w 1079 m – 1031 s – – 985 w – 942 vw – 870 vw 843 vw 798 w 778 m 653 w – 594 vw 528 w 405 w 321 m 317 vw 276 m –

3064 m – – 2961 sh 2932 w 2932 w 2899 w 2843 m 1608 m 1571 m – 1487 m 1475 m 1446 s 1352 m 1336 m 1315 m 1284 sh – 1251 w 1227 vw 1162 w 1110 m 1074 s 1024 s 1020 m 1003 w – 974 w 963 vw – 895 vw 861 m 787 m 752 s 695 sh 642 m 582 m 518 vw – 351 w 331 w 298 vw 266 vw

– 3065 m – 2962 m – – 2930 m 2871 m 1615 m 1577 vw 1550 vw – 1491 vw 1457 w 1393 m 1355 m – – – 1230 w 1212 w 1180 m 1082 m – 1030 m – – 980 w 971 vw 955 vw – – – 786 m 763 vw 661 vw – – 517 w – 348 m 312 m 291 w –

Abbreviations used: m, stretching; d, bending; t, torsion; r, ring; s, strong; m, medium; w, weak; sh, shoulder; v, very. Theoretical frequencies scaled by 0.960 in the high wavenumbers region and by 0.988 in the low wavenumbers region (below 1800 cm 1). Only PED values greater than 10% are given.

E. Sayın et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814

m(OH) (100) m(CH) (90) m(CH) (99) m(CH) (94) mas(CH2) + mas(CH2) (99) mas(CH2) + mas(CH2) (87) mas(CH) + ms(CH2) (93) ms(CH2) + ms(CH2) (94) mring(CAC) (54) mring(CAC) (52)

FT-IR

2

Calculated

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E. Sayın et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814 Table 2 The wavenumbers (cm

1

) of the [Pd(CN)4]2 vibrations in the complexes.

Assignments

K2[Pd(CN)4]
H2O [26]

1

2

3

A1g, m(C„N) B1g, m(C„N) Eu, m(C„N) Eu, m(C13N) Eu, m(MAC) A1g, m(MAC) Eu, d(MACN)

(2169) vs (2159) s 2135 vs 2096 w 486 w (436) m 393 s

(2199) vs (2184) m 2183 vs, 2158 s 2115 sh 504 m (459) w 402 m

(2188) vs (2174) m 2170 vs, 2161 s 2114 sh 507 m (465) m 402 s

(2177) vs (2162) sh 2153 vs 2115 sh 507 m (463) m 395 s

Abbreviations used: s, strong; m, medium; w, weak; sh, shoulder; v, very. The symbols m, d and p refer to valence, in-plane and out-of-plane vibrations, respectively. Raman bands are given in parentheses.

Table 3 Experimental data for complexes 1, 2 and 3. Complex

1

2

3

Empirical formula Color/shape Fw Temperature (K) k (Å) Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z l (mm 1) q (calcd.) (g cm 3) Max. crystal dimen. (mm) Range of h Range of k Range of l Number of reflections total Number of reflections unique No of reflections with I > 2r(I) Structure solution Rint 2hmax (°) Tmin/Tmax Number of parameters Goodness-of-fit on F2 R [F2 > 2r(F2)] Rw (Dq) max (e A 3) (Dq) min (e A 3)

C18H18N6O2PdCu Blue/block 520.32 100

C18H18N6O2PdZn Colorless/block 522.17 100 Mo Ka (k = 0.71073 Å) Triclinic P 1 8.1344 (6) 8.2255 (6) 9.0920 (7) 116.110 (2) 105.476 (3) 99.156 (3) 498.85 (6) 1 2.13 1.738 0.28  0.24  0.21 –10 < h < 10 –10 < k < 10 –12 < l < 12 8868 2463 2431 Direct methods 0.026 56.8 0.587/0.663 134 1.13 0.017 0.045 0.32 0.87

C18H18N6O2PdCd Colorless/block 569.19 292

Triclinic P 1 8.0978 (19) 8.3704 (10) 8.9877 (11) 117.329 (4) 106.859 (6) 95.907 (6) 497.58 (15) 1 2.00 1.737 0.31  0.24  0.17 –10 < h < 10 –11 < k < 11 –12 < l < 11 7620 2460 2414 0.054 56.8 0.576/0.728 135 1.09 0.034 0.094 1.12 0.79

by direct methods [16] and refined by full-matrix least squares against F2 using all data [16]. All non-H atoms were refined anisotropically. In compounds (1, 2 and 3), H1 and H1A (for OH groups) atoms were located in difference syntheses and refined isotropically. In all compounds, the remaining H atoms were positioned geometrically at distances of 0.95 Å (CH) and 0.99 Å (CH2) (for 1 and 2) and 0.93 Å (CH) and 0.97 Å (CH2) (for 3) from the parent C atoms; a riding model was used during the refinement processes and the Uiso(H) values were constrained to be 1.2Ueq(carrier atom). Results and discussion Vibrational spectroscopy 2-Pyridineethanol vibrations The FT-IR and Raman spectra of the complexes and free hepH are illustrated in Figs. 1 and 2, respectively. Values of wavenumbers are collected in Table 1, together with the assignment of

Monoclinic P21/n 10.4598 (9) 8.9451 (7) 10.8733 (9) 90 93.632 (3) 90 1015.31 (14) 2 1.96 1.862 0.27  0.21  0.17 –13 < h < 13 –11 < k < 11 –14 < l < 14 17,762 2542 2133 0.023 56.8 0.620/0.732 135 1.13 0.017 0.050 0.47 0.28

characteristic bands [14]. Since the complexes are joined by hydrogen bonds, the vibrational spectral analyses were performed based on the characteristic OH, CH2, CH, CO, CC and ring vibrations. OH vibrations. Unassociated hydroxyl groups absorbs strongly in the region of 3670–3580 cm 1 [17]. A broad stretching of OAH also indicates the presence of intramolecular hydrogen bonding [18]. The observed band due to OAH stretching is very broad in the case of free hepH molecules, which indicates the intermolecular hydrogen bonding between the ACH2OH groups. The shift to lower wavenumbers of these stretching modes may be attributed to covalent bondings in the complexes. The bands observed at 3170 (for 1), 3065 (for 2), 3064 (for 3) cm 1 in the FT-IR spectra are not observed in the Raman spectra. CH2 vibrations. The CH2 antisymmetric stretching vibrations are generally observed in the region of 3000–2900 cm 1, while the CH2 symmetric stretch will appear between 2900 and 2800 cm 1

808

E. Sayın et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 132 (2014) 803–814

Table 4 The selected bond lengths (Å) and angles (°) for complexes 1, 2 and 3. 1

2

3

Bond lengths Pd1AC1 Pd1AC2 Cu1AO1 Cu1AN2 Cu1AN3

1.988 (2) 1.987 (2) 2.3271 (16) 1.996 (2) 2.0486 (16)

Pd1AC8 Pd1AC9 Zn1AO1 Zn1AN1 Zn1AN2

1.9900 1.9880 2.1245 2.1581 2.1327

Bond angles C1APd1AC1i C2APd1AC1 C2iAPd1AC1 O1ACu1AO1ii N2ACu1AN2ii N2ACu1AN3 N2iiACu1AN3 N2ACu1AO1 N3ACu1AO1 C1APd1AC1i C2APd1AC1 N3iiACu1AO1 N3ACu1AN3ii Cu1AO1AH1 C9AO1ACu1 C2AN2ACu1 C3AN3ACu1 C3AN3AC7 C7AN3ACu1 N1AC1APd1 N2AC2APd1

180.000 (1) 89.53 (9) 90.47 (9) 180.00 (10) 180.000 (1) 87.49 (7) 92.51 (7) 88.31 (8) 86.68 (6) 180.000 (1) 89.53 (9) 93.32 (6) 180.000 (1) 124 (2) 122.59 (13) 168.05 (15) 115.56 (13) 118.46 (17) 125.90 (13) 178.9 (2) 178.19 (19)

C8APd1AC8i C9APd1AC8 C9iAPd1AC8 C9APd1AC9i O1AZn1AO1ii O1AZn1AN1 O1iiAZn1AN1 O1AZn1AN2 O1iiAZn1AN2 N1iiAZn1AN1 C8APd1AC8i C9APd1AC8 N2AZn1AN1 N2iiAZn1AN1 N2iiAZn1AN2 Zn1AO1AH1A C7AO1AZn1 C1AN1AZn1 C5AN1AZn1 C8AN2AZn1 N2AC8APd1 N3AC9APd1

180.00 (8) 89.95 (6) 90.05 (6) 180.00 (9) 180.0 87.56 (4) 92.44 (4) 89.50 (5) 90.50 (5) 180.00 (7) 180.00 (8) 89.95 (6) 87.20 (5) 92.80 (5) 180.0 121.7 (17) 125.42 (9) 117.52 (9) 124.17 (9) 166.16 (11) 179.18 (12) 178.96 (14)

Symmetry codes: [(i)

x + 1,

y + 1,

z + 3; (ii)

x,

y + 1,

z + 2 (for 1)], [(i)

x,

Table 5 Hydrogen-bond geometries (Å, °) for complexes 1, 2 and 3. Complex

DAH


A

DAH

H


A

D


A

DAH


A

1

O1AH1


N1iii C3AH3


O1ii C8AH8A


N2ii

0.78 (4) 0.95 0.99

1.95 (4) 2.47 2.58

2.727 (3) 3.098 (3) 3.310 (4)

171 (4) 124 130

2

O1AH1A


N3iii C6AH61


N2ii

0.78 (2) 0.99

1.91 (3) 2.61

2.684 (2) 3.350 (2)

172 (3) 131

3

O1AH1


N1iii

0.81 (3)

1.90 (3)

2.687 (3)

166 (4)

Symmetry codes: (ii) x, y + 1, z + 2; (iii) x, y + 1, z (for 1); (ii) (iii) x, y 1, z (for 2); (iii) x + 1/2, y 1/2, z + 1/2 (for 3).

x + 1,

y,

z + 1;

[19]. In the complexes, CH2 antisymmetric stretching absorption was assigned in the region of 2946–2925 cm 1 in FT-IR spectra (between 3007–2946 cm 1 in Raman spectra). In FT-IR spectra, CH2 symmetric vibrations were observed in the region of 2888– 2842 cm 1. Also, the absorption bands of the dring(CH2) groups in all complexes are observed in the frequency range of 1507– 1330 cm 1, and these bands shifted to higher frequencies when compared to free hepH ligand.

CH vibrations. Usually the carbon hydrogen stretching vibrations give rise to bands in the region of 3100–3000 cm 1 in all aromatic complexes [20]. The bands observed at 3013 cm 1 (FT-IR) and at 3024 cm 1 (Raman) for free hepH are assigned to the previously mentioned mode. In the complexes; the same modes are observed in the regions of 2969–2958 cm 1 (in the FT-IR spectra) and 3021– 3016 cm 1 (in the Raman spectra). The in-plane and out-of-plane CAH bending vibrations are observed in the regions of 1350– 950 cm 1 and 950–600 cm 1, respectively [21]. The modes corresponding to the bending of complexes and free hepH are all assigned and given in Table 1.

y,

z; (ii)

x + 1,

(14) (14) (10) (11) (13)

y,

Cd1AO1 Cd1AN2 Cd1AN3 Pd1AC1 Pd1AC2

2.3023 2.3997 2.3225 1.9851 1.9845

O1iACd1AO1 O1ACd1AN2 O1iACd1AN2 O1iACd1AN2i N2ACd1AN2i N3ACd1AN2 N3iACd1AN2 O1ACd1AN3 O1iACd1AN3 N3iACd1AN3 C1iiAPd1AC1 C2APd1AC1 C2APd1AC1ii C2iiAPd1AC2 Cd1AO1AH1 C3AO1ACd1 C2AN2ACd1 C5AN3ACd1 C9AN3ACd1 N1AC1APd1 N2AC2APd1

180.0 88.38 (6) 91.62 (6) 88.38 (6) 180.00 (8) 85.70 (5) 94.30 (5) 84.34 (5) 95.66 (5) 180.0 180.00 (6) 89.91 (6) 90.09 (7) 180.0 117 (2) 124.98 (10) 147.32 (13) 123.14 (10) 117.96 (10) 178.22 (16) 178.20 (16)

z + 1 (for 2)] and [(i)

x + 1,

y,

z + 1; (ii)

x,

y,

(13) (14) (12) (16) (16)

z + 1 (for 3)].

CC and ring vibrations. The CAC stretching modes frequencies of the pyridine ring appear in the spectral range of 1650–1200 cm 1 [22]. The ring CAC stretching bands appear in the FT-IR spectra at 1607 and 1571 (for 1), 1608 and 1572 (for 2), 1608 and 1571 (for 3) cm 1 and in the Raman spectra at 1623 and 1581 (for 1), 1618 and 1583 (for 2) and 1608 and 1571 (for 3) cm 1. In the complexes, the observed CACAC in-plane and out-of-plane bending modes are presented in Table 1 along with their assignment. When the aromatic ring nitrogen involves in the complex formation, certain ring modes, particularly modes of 1600–1400 cm 1, increase in value both due to the coupling with M–Nligand bond vibrations [23] and due to alterations of the ring force fields [24]. CO vibrations. The CAO stretching modes were observed at 1002 cm 1 (in the FT-IR spectrum) and at 1011 cm 1 (in Raman spectrum) for free hepH. These modes were observed at 1026 (for 1), 1021 (for 2) and 1020 (for 3) cm 1 in the FT-IR spectra, but was not observed in the Raman spectra. The spectral features and assignments of the CAO in-plane and out-of-plane bending vibrations were included in Table 1. [Pd(CN)4]2 vibrations The FT-IR and Raman spectroscopies are very important techniques for the elucidation of metal complex structures containing cyanide moieties. The characteristic bands in the FT-IR and Raman spectra of metal complexes containing cyanide are sharp and strong between 2000 and 2200 cm 1 resulting from m(C„N). The number and positions of m(C„N) absorptions reveal bridging or terminal cyanides in the complexes. Cyanide stretches of ionic cyanides such as KCN are observed at 2080 cm 1 and this peak shifts to 2143 cm 1 in [Pd(CN)4]2 because of coordination of cyanide to palladium as a terminal ligand. As a result of bridging cyanide (PdACNAM), the cyanide stretch is above 2143 cm 1 [25]. In the FT-IR spectrum of complex K2[Pd(CN)4]
H2O, it is observed at 2135 cm 1 [26]. The assigned wavenumbers and modes for

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Fig. 3. The molecular structures of 1 (a), 2 (b) and 3 (c) with the atom-numbering schemes. Symmetry codes: (i) 1, (i) 1 x, y, 1 z; (ii) 1 + x, y, 1 + z for 2, (i) x, y, 1 z; (ii) 1 + x, y, z for 3.

x, 1

y, 2

z; (ii)

1 + x, y,

1 + z, (iii) 1

x, 1

y, 3

z. for

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Table 6 Structural data for complexes supporting CAH


Pd interactions. Complex

CAH


Pd

H


Pd

C


Pd

CAH


Pd

1 2 3 [Cu(N-Meim)4Pd(CN)4]n [29]

C8AH8B


Pd1 C6AH6B


Pd1 C4AH4A


Pd1 C8AH8B


Pd1

2.750 (4) 2.661 (1) 2.869 (2) 3.296

3.638 (3) 3.610 (2) 3.753 (2) 4.013

149.53 (1)° 160.50 (1)° 151.80 (1)° 137.02°

Fig. 4. OAH


N and p


p interactions (a) and CAH


Pd interactions (b) in 1.

[Pd(CN)4]2 group in the complexes are given in Table 2, together with the vibrational wavenumbers of [Pd(CN)4]2 [26]. In the FTIR spectra of 1 and 2, the two observed sharp bands [2183 and 2158 (for 1) and 2170 and 2161 (for 2) cm 1] are attributed to the presence of both bridged and terminal cyanides; the lower wavenumber corresponds to the non-bridging cyanide and the higher wavenumber corresponds to the bridging cyanides. The intensity of the lower wavenumber is stronger than that of

the higher wavenumber [6]. The Raman spectrum of the mononuclear K2[Pd(CN)4]
H2O compound showed two bands at 2169 cm 1 and 2159 cm 1, which can be assigned to the CN stretchings. The two Raman fundamentals are assigned to the bands of 2199 and 2184 (for 1), 2188 and 2174 (for 2) and 2177 and 2162 (for 3) cm 1 (Table 2). These spectral data are in good agreement with the structural data presented. According to this explanation, C1„N1 and C2„N2 bond lengths are 1.141(3) and 1.151(4) Å

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811

Fig. 5. OAH


N interactions (a) and CAH


Pd and p


p interactions (b) in 2.

(for 1) and C9„N3 and C8„N2 bond lengths are 1.142(2) Å and 1.146(2) Å (for 2). The intensity of the lower wavenumber is stronger than that of the higher wavenumber. In complex 3, C1„N1 and C2„N2 bond lengths are 1.138(2) and 1.142(2) Å. No splitting of CN stretching mode occurs at 2153 cm 1 in complex 3, because of the bridging and terminal m(CN) absorption bands cause overlapping [5]. Crystallographic analyses Crystal data and structure refinement parameters for the complexes are presented in Table 3. Selected bond lengths and angles

for 1–3 are collected in Table 4, and the hydrogen bonding geometry for complexes 1–3 is given in Table 5. The molecular structures of the compounds, along with the atom-numbering schemes are depicted in Fig. 3a–c. The Pd atoms are located on inversion centers and surrounded by four C„N groups, the PdAC and C„N bond distances and CAPdAC bond angles are in the ranges of [1.9845(16)–1.9900(14) Å], [1.138(2)–1.151(4) Å] and [89.53(9)–90.47(9)°], respectively. In all three compounds, the coordinations around Pd atoms are square-planar (Fig. 3). On the other hand, the metal (M) atoms, (where M = Cu, Zn and Cd for 1, 2 and 3, respectively) are also located on inversion centers and surrounded by N and O atoms, the MAN and MAO bond distances and

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Fig. 6. OAH


N interactions (a) and p


p interactions (b) in 3.

NAMAN and OAMAN bond angles are in the ranges of [1.996(2)– 2.3297(14) Å], [2.1245(10)–2.3271(16) Å] and [85.70(5)– 94.30(5)°] and [86.68(6)–93.32(6)°], respectively. In all three compounds, the symmetric C„N nitrogens and O atoms of the ethanol groups in the equatorial plane around the M atoms form slightly distorted square-planar arrangements, while the slightly distorted octahedral coordinations are completed by the symmetric pyridine N atoms in the axial positions (Fig. 3). The most striking features of the complexes are the presence of the intermolecular CAH


Pd interactions between Pd and H atoms of the hepH ligands: Pd1


H8B [2.750(4) Å] and Pd1


C8B [3.638(3) Å] distances and C8AH8B


Pd1 [149.53(1)°] angle (for 1), Pd1


H62 [2.661(1) Å] and Pd1


C6 [3.610(2) Å] distances and C6AH6B


Pd1 [160.50(1)°] angle (for 2) and Pd1


H4A [2.869(2) Å] and Pd1


C4 [3.753(2) Å] distances and C4AH4A


Pd1 [151.80(1)°] angle (for 3). Intermolecular CAH


Pd(II) interactions have been reported in the literature [27–29]. As can be seen in Table 6, in the complexes CAH


Pd interaction distances are not

long; therefore these interactions may be taken into account as bonds. In the crystal structures, the intermolecular OAH


N hydrogen bonds link the polymeric chains into a two-dimensional network, in which they seem to be effective in the stabilization of the crystal structures (Table 5 and Figs. 4–6). The p


p contacts between the pyridine rings, Cg3ACg3i [symmetry code: (i) x, y, 1 z (for 1)], Cg3ACg3i [symmetry code: (i) 1 x, 1 y, 2 z (for 2)] and Cg3ACg3i [symmetry code: (i) 1 x, 1 y, 1 z (for 3)], where Cg3 are the centroids of the pyridine rings, [(N3/C3AC7) (for 1), (N1/C1AC5) (for 2) and (N3/C5AC9 (for 3)], may further stabilize the structures, with centroid–centroid distances of 3.9124(15) Å (for 1), 3.9552(9) Å (for 2) and 3.8584(10) Å (for 3) (Figs. 4–6). Thermal analyses of the complexes Thermal behaviors of the complexes were studied by TG, DTG and DTA in the temperature range of 30–700 °C in dry air

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813

Fig. 7. TG, DTG and DTA curves of complexes 1(a), 2(b) and 3(c).

atmosphere. The thermal analyses curves of the complexes are similar to each other and thermal decompositions of complexes proceed in two stages mass loss (Fig. 7a–c). The first stages of the complexes 1–3 lose two hepH ligands in the temperature range of 198–363 °C (for 1), 154–291 °C (for 2) and 183–313 °C (for 3) [found (calcd.): 23.35% (23.66%) (for 1), 44.83% (47.16) (for 2) and 45.25% (43.27%) (for 3)]. The following stage for complexes 1–3 are related with the exothermic removal of CN groups in the temperature range of 363–412 °C [DTAmax = 405 °C; found: 20.00%, calcd.: 20.21% (for 1)], 291 and 440 °C [DTAmax = 437 °C; found: 19.92%, calcd.: 16.54% (for 2)] and 313 and 405 °C [DTAmax = 400 °C; found: 15.59%, calcd.: 18.28% (for 3)]. The final

solid products of thermal decompositions were identified as MO and PO (M = Cu(II), Zn(II) and Cd(II), found: 35.13%, calcd.: 38.81% (for 1), found: 38.96%, calcd.: 39.03% (for 2) and found: 43.07%, calcd.: 44.06% (for 3). The thermal decomposition products were identified by FT-IR spectroscopy. Conclusion This study presents new cyanide complexes. The complexes [Cu(hepH)2Pd(l-CN)2(CN)2]n (1), [Zn(hepH)2Pd(l-CN)2(CN)2]n (2) and [Cd(hepH)2Pd(l-CN)2(CN)2]n (3) have been synthesized and characterized by elemental and thermal analyses, FT-IR and Raman

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spectroscopies, and single crystal X-ray diffraction technique. Vibration assignments are given for all the observed bands and the spectral features support the structures of the polymeric complexes. From the crystallographic data, it was determined that the crystals packings of complexes 1–3 were composed of rare intermolecular CAH


Pd interactions. The anagostic interactions between CAH


Pd play important roles in the constructions of the supramolecular networks. In addition, in all complexes the p


p and OAH


N interactions have also observed. These interactions play an important role in the construction of the supramolecular networks. Acknowledgements This work was supported by the Research Fund of Eskisehir Osmangazi University. Project No.: 201419A207. The authors are indebted to Anadolu University and the Medicinal Plants and Medicine Research Centre of Anadolu University, Eskisßehir, Turkey, for the use of X-ray diffractometer. Appendix A. Supplementary material CCDC reference numbers 991007 (for 1), 991008 (for 2) & 991006 (for 3) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.htmL (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033; e-mail: [email protected]). Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.05.094. References [1] M. Pilkington, S. Decurtins, Comprehensive Coordination Chemistry II: From Biology to Nanotechnology, second ed., Elsevier, Oxford, 2004. [2] A. Sßenocak, A. Karadag˘, E. Sßahin, J. Inorg. Organomet. Polym. 23 (2013) 1008– 1014.

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