Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
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Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies Alper Yardan a,⇑, Cigdem Hopa b, Yasemin Yahsi c, Ahmet Karahan d, Hulya Kara c, Raif Kurtaran e a
Balikesir University, Dursunbey Vocational School, Department of Property Protection and Safety, TR-10800 Balikesir, Turkey Balikesir University, Faculty of Art and Science, Department of Chemistry, TR-10145 Balikesir, Turkey c Balikesir University, Faculty of Art and Science, Department of Physics, TR-10145 Balikesir, Turkey d Suleyman Demirel University, Sutculer Prof. Dr. Hasan Gurbuz Vocational School, Department of Property Protection and Safety, TR-32950 Isparta, Turkey e Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, 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
New heterodinuclear complexes 1
and 2 have been synthesized. Crystal structures of 1 and 2 have
been determined by single crystal XRD analysis. 1 and 2 were characterized by IR spectroscopy, elemental and thermal analysis.
a r t i c l e
i n f o
Article history: Received 10 June 2014 Received in revised form 14 August 2014 Accepted 24 August 2014 Available online 3 September 2014 Keywords: Schiff bases Heterodinuclear complexes Phenoxo bridge Thermal analysis Single crystal X-ray
a b s t r a c t Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where H2L = N,N0 -bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Investigations of coordination complexes of transition metals containing Schiff base ligands continue to attract strong interest ⇑ Corresponding author. Tel.: +90 266 6624940; fax: +90 266 6624941. E-mail address: [email protected] (A. Yardan). http://dx.doi.org/10.1016/j.saa.2014.08.091 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
owing to their importance in material science, molecular electronics, photochemistry, biological activity, molecular magnetic materials and nanostructure studies [1–12]. Especially, the field of molecular magnetism has seen a number of Schiff base complexes synthesized and characterized in the past decades in the search for new systems that behave like a single-molecule magnet (SMM) [13]. SMMs exhibit interesting phenomena, such as slow
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magnetization relaxation, magnetization hysteresis and quantum tunneling of the magnetization (QTM) [14,15]. Salen type tetradentate (ONNO) Schiff base ligands derived from N,N0 -bis(salicylidene)-1,3-diaminopropane (H2L), have been used for complexation in recent years [16,17]. Salen-type Schiff base complexes themselves can act as ligand-complexes and can chelate a second metal substrate using phenolate oxygen atoms of the Schiff base ligand to construct extended homo- or heteropolynuclear complexes [18–22]. Recently, the structural characterization of homodinuclear ZnAZnCl2 [23,24], ZnAZnBr2 [25], CoACoCl2 [26], CuACuCl2 [27] and heterodinuclear NiAHgCl2 [28,29], NiAHgBr2 [30], NiAZnCl2 [31,32], NiAZnBr2 [33], NiACoCl2 [34], NiACoBr2 [34], ZnACdBr2 [35], ZnAHgI2 [36] ONNO type Schiff base complexes have been reported. To the best of our knowledge, the structural characterization of the phenoxo-bridged heterodinuclear ZnANiCl2, ONNO type Schiff base complex, (2), is described here for the first time. This work reports the synthesis of two new phenoxo-bridged heterodinuclear NiIIAHgII (1) and ZnIIANiII (2) complexes along with their characterization, single crystal X-ray structures and thermal studies. Experimental section Materials and methods All reagents and solvents were purchased from Merck, Aldrich or Carlo Erba and used without further purification. Elemental analyses for the ligand and complex were carried out using standard methods with a Eurovector 3018 CHNS analyzer. IR spectra were recorded using a Perkin–Elmer 1600 series automatic recording FT-IR spectrophotometer with the KBr disk technique over the range 400–4000 cm1. The thermogravimetry/differential thermal analysis (TG/DTA) measurements were undertaken using a Perkin Elmer Diamond DTA/TG thermal analyzer. In this study, thermogravimetric curves were obtained using a flow rate of the nitrogen carrier gas (at 3 bar) of 200 mL/min and a heating rate of 20 °C/min and with ceramic crucibles.
slowly to the mixture with constant stirring. The solution was filtered and then allowed to stand at room temperature for three days. Blue crystals of complex 2 were collected by filtration and dried in an air atmosphere. Calcd. Found for 2 (C23H32Cl2N4NiO4Zn) Yield: 0.39 g. (62%), C, 44.3; H, 5.13; N, 8.98. Found: C, 43.7; H, 5.02; N, 8.82%. X-ray structure determination Intensity data for suitable single crystals of 1 and 2 were collected using an Oxford Diffraction Xcalibur-3 single crystal X-ray diffractometer equipped with a Mo Ka radiation source (k = 0.71073 Å at 296 K). Data collection and data reductions were performed using the CRYSALIS CCD and CRYSALIS RED programs [37]. The structures were solved by direct methods and refined using full-matrix least-squares against F2 using SHELXTL [38]. All non-hydrogen atoms were assigned anisotropic displacement parameters and refined without positional constraints. Hydrogen atoms were included in idealised positions with isotropic displacement parameters constrained to 1.5 times the Uequiv of their attached carbon atoms for methyl hydrogens, and 1.2 times the Uequiv of their attached carbon atoms for all others. The Level B Alerts result from the C3, C6, C8, C9, C23 atoms for complex 1 and the C20 atom for complex 2 which were refined isotropically due to its high thermal motion. The absolute structure was determined on the basis of the Flack parameter [39] x = 0.063(9) for 1 and 0.042(16) for 2. A Flack parameter value close to 0 is indicative of a non-centrosymmetric structure. Details of the data collection parameters and crystallographic information for the complexes are summarized in Table 1. Selected bond lengths and angles are listed in Table 2 for complex 1 and Table 3 for complex 2, respectively. Hydrogen bond geometries of the complexes are shown in Table 4. Molecular drawings were obtained using MERCURY [40]. The crystal structures of 1 and 2 along with the atom numbering scheme are given in Figs. 1 and 3, respectively. Packing diagrams are displayed in Fig. 2 for 1 and in Fig. 4 for 2.
Synthesis Synthesis of complex 1 N,N0 -bis(salicylidene)-1,3-propanediamine (H2L) was prepared by reacting a basic ethanolic solution of salicylaldehyde and 1,3diamino propane as described previously in the literature [33]. Triethylamine (Et3N) was added dropwise to the solution of Schiff base ligand (1 mmol, 0.282 g) in 20 mL DMF. A solution of NiCl2.6H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added to the DMF solution. The solution was stirred at the boiling point under an air atmosphere. A solution of HgCl2 (1 mmol, 0.271 g) in ethanol (20 mL) was added to the resulting solution and this too was stirred at the boiling point under an air atmosphere. The solution was filtered and then allowed to stand at room temperature for five days. Green crystals of complex 1 were collected by filtration and dried in an air atmosphere. Calcd. Found for 1 (C23H30Cl2HgN4NiO4): Yield: 0.51 g. (68%), C, 36.4; H, 3.96; N, 7.40. Found: C, 35.7; H, 4.12; N, 7.58%. Synthesis of complex 2 Complexes 1 and 2 were prepared using similar methods. Equivalent amounts of triethylamine (Et3N) was added dropwise to deprotonate the phenolic OH group of the solution Schiff base ligand (1 mmol, 0.282 g) in DMF (20 mL). To a solution of ZnCl2 (1 mmol, 0.135 g) in ethanol was added to the resulting solution and it was stirred at boiling point under an air atmosphere. A solution of NiCl2.6H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added
Table 1 Crystal data and structure refinements for 1 and 2.
Empirical formula Formula weight Crystal system Space group Unit cell dimensions
Volume Z Density (calculated) Absorption coefficient h range for data collection Index ranges
Reflections collected Independent reflections Refinement method Goodness-of-fit on F2 R indices [I > 2r(I)] Flack parameter
1
2
C23H30Cl2HgN4NiO4 756.71 g mol1 Monoclinic Cc a = 10.5428 (11) Å b = 15.1258 (19) Å c = 17.350 (3) Å b = 97.479 (13)° 2743.3 (6) Å3 4 1.832 g.cm3 6.51 mm1
C23H32Cl2N4NiO4Zn 623.51 g mol1 Monoclinic Cc a = 10.4994 (5) Å b = 15.1545 (7) Å c = 17.1967 (6) Å b = 98.709 (4)° 2704.7 (2) Å3 4 1.531 g cm3 1.82 mm1
3.9–27.6°
3.9–28.8°
10 6 h 6 13, 19 6 k 6 19, 22 6 l 6 22 6649 3773 [Rint = 0.076]
8 6 h 6 14 20 6 k 6 20 23 6 l 6 23 7114 4386 [Rint = 0.024]
Full-matrix least-squares on F2 S = 0.71 R1 = 0.046, wR2 = 0.068 0.063(9)
Full-matrix least-squares on F2 S = 0.96 R1 = 0.041, wR2 = 0.115 0.042(16)
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A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356 Table 2 Some selected bond lengths [Å] and angles [°] for 1. Bond lengths (Å) Ni1AO1 Ni1AO2 Ni1AO3 Ni1AO4 Ni1AN1 Ni1AN2
1.980 2.008 2.136 2.159 2.043 2.032
(11) (9) (12) (12) (12) (15)
Bond angles (°) O1ANi1AO2 O1ANi1AN1 O3ANi1–O1 O3ANi1AO2 O3ANi1AN1 O3ANi1AN2 O4ANi1AO1 O4ANi1AO2 O4ANi1AO3 O4ANi1AN1 O4ANi1AN2
81.5 (4) 89.8 (6) 91.7 (5) 91.7 (4) 84.9 (4) 89.6 (5) 91.7 (5) 92.0 (4) 175.4 (5) 91.9 (4) 87.6 (5)
Hg1AO1 Hg1AO2 Hg1ACl1 Hg1ACl2
2.359 2.321 2.345 2.354
(10) (10) (4) (5)
N1ANi1AO2 N2ANi1AO1 N2ANi1AO2 N2ANi1AN1 O2AHg1ACl1 O2AHg1ACl2 Cl1AHg1ACl2 O2AHg1–O1 Cl1AHg1AO1 Cl2AHg1AO1 Ni1AO1AHg1 Ni1AO2AHg1
170.6 (6) 171.3 (5) 89.9 (5) 98.9 (6) 107.1 (3) 103.5 (3) 139.6 (3) 67.6 (3) 104.4 (3) 111.4 (3) 104.6 (4) 105.0 (4)
Fig. 1. DTA/TG/DTG curves of complex 1.
Table 3 Some selected bond lengths [Å] and angles [°] for 2. Bond lengths (Å) Zn1AN2 Zn1AN1 Zn1AO1 Zn1AO2 Zn1AO4 Zn1AO3
2.009 2.012 2.020 2.019 2.124 2.140
(4) (5) (4) (4) (4) (4)
Bond angles (°) N2AZn1AN1 N2AZn1AO1 N1AZn1AO1 N2AZn1AO2 N1AZn1AO2 O1AZn1AO2 N2AZn1AO4 N1AZn1AO4 O1AZn1AO4 O2AZn1AO4 N2AZn1AO3 N1AZn1AO3
99.7 (2) 169.53 (18) 90.80 (18) 90.76 (18) 169.44 (18) 78.79 (14) 88.54 (17) 86.99 (19) 92.35 (16) 91.62 (16) 90.22 (17) 90.64 (18)
Ni1AO2 Ni1AO1 Ni1ACl1 Ni1ACl2
1.985 2.003 2.200 2.224
(4) (4) (2) (2)
O1AZn1AO3 O2AZn1AO3 O4AZn1AO3 O2ANi1AO1 O2ANi1ACl1 O1ANi1ACl1 O2ANi1ACl2 O1ANi1ACl2 Cl1ANi1ACl2 Ni1AO1AZn1 Ni1AO2AZn1
89.34 (16) 91.01 (16) 177.10 (18) 80.01 (15) 112.00 (13) 116.38 (13) 111.94 (12) 111.77 (13) 118.52 (8) 100.04 (17) 100.70 (17)
Results and discussion IR spectra The interest of the IR spectrum of the title complexes lies mainly in the bands arising from the azomethine and hydroxyl groups of the ligands, and the carbonyl group from the DMF ligand.
Fig. 2. DTA/TG/DTG curves of complex 2.
The spectrum of the free ligand (H2L) shows significant bands at 1611 cm1 for C@N stretching, 2752–2748 cm1 for phenolic OAH stretching and 1294 cm1 for phenolic CAO. When the IR spectra obtained from complex 1 is compared with that from the free ligand, the complex exhibits a m(C@N) band at 1624 cm1 showing a shift to higher wavenumbers indicating that the nitrogen atom of the azomethine group is coordinated to the nickel (II) ion [41]. In addition, the phenolic m(OAH) band in the ligand spectrum disappeared in the complex spectrum [42]. These results prove the complexation [43]. The m(C@O) stretching vibration of
Table 4 Hydrogen bond geometry (Å, °) of compounds 1 and 2.
1 2 CAHp 1
2
a
DAH Aa
DAH
H A
D A
DAH A
Symmetry
C11AH11Cl2 C19AH19CCl1 C8AH8Cl1
0.93 0.96 0.93
2.76 2.92 2.88
3.603 3.708 3.711
151 140 150
x, y, 1/2 + z 1/2 + x, 1/2 + y, z x, y, 1/2 + z
C9AH9AR2 C20AH20BR2 C23AH23BR1 C5AH5R3 C16-H16AR2 C20AH20BR2 C23AH23BR3
0.97 0.96 0.96 0.93 0.97 0.96 0.96
2.96 2.98 2.67 2.94 2.86 2.92 2.73
3.836 3.468 3.552 3.689 3.736 3.527 3.494
151 113 153 139 150 122 137
x,y, 1/2 + z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 y, 1/2 + z x, y, 1/2 + z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 + y, z
D: Donor, A: Acceptor, [R1: C12C13C14C15C16C17, R2: C2C3C4C5C6C7 for 1]. [R3: C9C10C11C12C13C14, R2: C2C3C4C5C6C7 for 2].
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Decomposition of complex 1 starts at 53 °C and this step continues up to 134 °C. Two DMF molecules leave in this first step (calcd./ found: 19.3/17.8%) [47,48]. In the DTA curve, there is an endothermic peak at 119 °C for this event. The second weight loss between 134 and 468 °C was attributed to the departure of ligand (calcd./ found: 37.3/39.9%). Over the temperature range 468–654 °C two coordinated chlorides leave the structure with 9.9% weight loss observed compared with the calculated theoretical value of 9.4%. Complex 2 was thermally stable up to 120 °C and decomposition started at this temperature and finished at 1200 °C with four stages. The TG curve (Fig. 2) indicates that DMF molecules depart over the temperature range 119–198oC (calcd./found: 23.5/23.4%) [28,49]. Other steps between 198 and 1200 °C involve the loss of the ligand and two chlorides (calcd./found: 56.9/56.7%) and probably the formation of Zn-Ni as the final residue at 1200 °C (calcd./ found: 19.9/19.9%). Moreover, the thermogravimetric analyses reveal that complex 2 is more stable than complex 1. Fig. 3. Molecular structure of 1.
the DMF molecules can be assigned to the band at 1552 cm1 in the IR spectrum, which is lower than that in free DMF molecules (1655 cm1) because of the coordination of the DMF oxygen atoms to the zinc ion which is consistent with the results of X-ray analysis. Similarly, complex 2 exhibits a m(C@N) band at 1651 cm1 showing a shift to lower wavenumbers indicating that the nitrogen atom of azomethine group is coordinated to the zinc atom [44,45]. In addition, the phenolic m(OAH) band disappeared. The m(C@O) stretching vibration of the DMF molecules can be assigned to the band at 1551 cm1 in the IR spectrum [46].
Thermal analysis To examine the thermal stabilities of the complexes, thermogravimetric and differential thermal (TG/DTA) analyses were carried out in a nitrogen atmosphere at a heating rate of 20 °C/min from ambient temperature to 1200 °C. The DTA/TG/DTG diagrams of complexes 1 and 2 are shown in Figs. 1 and 2, respectively.
Crystal structure description of Complex 1 Complex 1 crystallizes in the monoclinic non-centrosymmetric chiral space group Cc and the asymmetric unit contains one molecule. The molecule comprises a binuclear heterometallic assembly of nickel(II) and mercury(II) in which the Ni(II) centre is connected to the [HgCl2] unit via two bridging phenolate oxygen atoms provided by the Schiff base anion. The molecular unit can be described as a dinuclear species with a six-coordinated nickel atom surrounded by the two phenolate oxygen and two imine nitrogen atoms of tetradentate Schiff base ligand occupying the equatorial positions and two oxygen atoms in the apical positions. The phenolate oxygen atoms bridge the mercury atom which is four-coordinated by those two oxygen atoms and two chlorine atoms. The [HgO2Cl2] unit undergoes severe distortions from ideal tetrahedral geometry which is reflected from its wide range of bond angles, being 67.57–139.59°. The coordination geometry around the nickel corresponds to an elongated octahedral structure because of the presence of the oxygen atoms in the apical positions with average distances of 2.15 Å, while the equatorial NiAN and NiAO bond distances are 1.979–2.043 Å. The deviation of Ni(II) ions from N2O2
Fig. 4. Molecular packing diagram of 1 in the bc plane (dashed lines denote Cl H interactions).
A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356
coordination plane [O1AN1AN2AO2] is 0.026 Å. In complex 1, the intramolecular NiHg distance is 3.44 Å which is close to the values found in similar salen-type compounds [28]. Selected bond lengths and angles are listed in Table 2, which lie well within the range of reported values for corresponding bond lengths and angles of similar hetero-dinuclear complexes [28,29,50–54].
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Complex 1, revealed the presence of intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected (Table 4). In these interactions, the metal bound chlorine atoms Cl1 and Cl2 act as the H-bond acceptor while C11 and C19 atoms act as the H bond donor [55]. These intermolecular interactions result in the formation of a 3D structure. This hydrogen bonded polymeric networks lie in the bc axis and stacks along to the a axis. (Fig. 4). However, these dimeric units are further connected by C–H. . .p interactions (H. . .R = 2.96, 2.98 and 2.67 Å) to the other heterobimetallic dimers present in the unit cell (Table 4). Crystal structure description of Complex 2
Fig. 5. Molecular structure of 2.
Complex 2 crystallizes in the monoclinic non-centrosymmetric chiral space group Cc and the asymmetric unit contains one molecule. The molecule comprises a binuclear heterometallic assembly of zinc (II) and nickel (II) in which the Zn (II) centre is connected to the [NiCl2] unit via two bridging phenolate oxygen atoms contributed by the Schiff base anion. The molecular unit of complex 2 can be described as being a hetero-dinuclear species with a six-coordinated zinc atom and a four-coordinated nickel atom. The Ni (II) ion is bridged by two phenolate oxygen atoms and two chlorine atoms. The Zn (II) ion is surrounded by N2O2 donor atoms of the Schiff base ligand in the equatorial positions and two oxygen atoms in the apical positions (see Fig. 5). The [NiO2Cl2] unit deviates from ideal tetrahedral geometry with the bond angles ranging between
Fig. 6. (a) Molecular packing diagram of 2 along the c axis (dashed lines denote Cl H interactions), (b). Space filling representation of 2 as in Fig. 6a.
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80.00° and 118.52°. The coordination geometry around the Zn (II) ion corresponds to an elongated octahedral structure because of the presence of the oxygen atoms in the apical positions with average bond lengths of 2.13 Å, while the equatorial ZnAN and ZnAO bond distances are 2.008–2.020 Å. The deviation of Zn (II) ions from N2O2 coordination plane [O1AN1AN2AO2] is 0.011 Å and the intramolecular ZnNi distance is 3.44 Å. Selected bond lengths and angles are listed in Table 3, which lie well within the range of reported values for corresponding bond lengths and angles of similar hetero-dinuclear complexes [28,29,50–54]. Complex 2, revealed the presence of intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected (Table 4). In this interaction, the metal bound chlorine atom Cl1 acts as the H-bond acceptor while the C8 atom acts as the H bond donor [55]. This intermolecular interaction results in the formation of infinite one dimensional zig-zag chains in the crystal lattice. The zig-zag chains propagate through the crystallographic c axis (Fig. 6a and b). However, these dimeric units are further connected by CAH. . .p interactions (H. . .R = 2.94, 2.86, 2.92 and 2.73 Å) to the other heterobimetallic dimers present in the unit cell (Table 4). Conclusion Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2 have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. CAH. . .p and CAHClAM interactions play a major role in controlling the molecular packing for complexes 1 and 2. In both structures the intermolecular CAHp separations are equal 2.9 Å and lie in the accepted distance range for this type of contact [39,56–58]. These intermolecular interactions result in the formation of a 3D structure for 1 and 1D zig-zag chains for 2. The thermogravimetric analyses illustrate that complex 2 is more stable than complex 1. Acknowledgements The financial support of the Scientific and Technical Research Council of Turkey (TUBITAK) Grants No: TBAG-108T431 and Balikesir University (Project No. 2007/10) is gratefully acknowledged. In addition, Yasemin Yahsi is also grateful to Dr. Lorenzo Sorace, Dr. Andrea Caneschi (Department of Chemistry, University of Florence) for the use of Xcalibur-3 diffractometer. We are also very grateful to Dr. Andrew Fisher for language corrections. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.08.091. References [1] C. Hopa, H. Yildirim, H. Kara, R. Kurtaran, M. Alkan, Spectrochim. Acta A 121 (2014) 282. [2] S. Celen, E. Gungor, H. Kara, D. Azaz, J. Coord. Chem. 66 (2013) 3170. [3] Y. Yahsi, H. Kara, Inorg. Chim. Acta 397 (2013) 110. [4] H. Kara, A. Azizoglu, A. Karaoglu, Y. Yahsi, E. Gungor, A. Caneschi, L. Sorace, Cryst. Eng. Comm. 14 (2012) 7320. [5] S.-G. Kang, H. Kim, S. Bang, C.H. Kwak, Inorg. Chim. Acta 396 (2013) 10. [6] K.R. Surati, B.T. Thaker, Spectrochim. Acta A 75 (2010) 235. [7] H. Sheykhi, E. Safaei, Spectrochim. Acta A 118 (2014) 915.
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Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies Alper Yardan a,⇑, Cigdem Hopa b, Yasemin Yahsi c, Ahmet Karahan d, Hulya Kara c, Raif Kurtaran e a
Balikesir University, Dursunbey Vocational School, Department of Property Protection and Safety, TR-10800 Balikesir, Turkey Balikesir University, Faculty of Art and Science, Department of Chemistry, TR-10145 Balikesir, Turkey c Balikesir University, Faculty of Art and Science, Department of Physics, TR-10145 Balikesir, Turkey d Suleyman Demirel University, Sutculer Prof. Dr. Hasan Gurbuz Vocational School, Department of Property Protection and Safety, TR-32950 Isparta, Turkey e Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, 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
New heterodinuclear complexes 1
and 2 have been synthesized. Crystal structures of 1 and 2 have
been determined by single crystal XRD analysis. 1 and 2 were characterized by IR spectroscopy, elemental and thermal analysis.
a r t i c l e
i n f o
Article history: Received 10 June 2014 Received in revised form 14 August 2014 Accepted 24 August 2014 Available online 3 September 2014 Keywords: Schiff bases Heterodinuclear complexes Phenoxo bridge Thermal analysis Single crystal X-ray
a b s t r a c t Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where H2L = N,N0 -bis(salicylidene)-1,3-diaminopropane and DMF = dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Investigations of coordination complexes of transition metals containing Schiff base ligands continue to attract strong interest ⇑ Corresponding author. Tel.: +90 266 6624940; fax: +90 266 6624941. E-mail address: [email protected] (A. Yardan). http://dx.doi.org/10.1016/j.saa.2014.08.091 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
owing to their importance in material science, molecular electronics, photochemistry, biological activity, molecular magnetic materials and nanostructure studies [1–12]. Especially, the field of molecular magnetism has seen a number of Schiff base complexes synthesized and characterized in the past decades in the search for new systems that behave like a single-molecule magnet (SMM) [13]. SMMs exhibit interesting phenomena, such as slow
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magnetization relaxation, magnetization hysteresis and quantum tunneling of the magnetization (QTM) [14,15]. Salen type tetradentate (ONNO) Schiff base ligands derived from N,N0 -bis(salicylidene)-1,3-diaminopropane (H2L), have been used for complexation in recent years [16,17]. Salen-type Schiff base complexes themselves can act as ligand-complexes and can chelate a second metal substrate using phenolate oxygen atoms of the Schiff base ligand to construct extended homo- or heteropolynuclear complexes [18–22]. Recently, the structural characterization of homodinuclear ZnAZnCl2 [23,24], ZnAZnBr2 [25], CoACoCl2 [26], CuACuCl2 [27] and heterodinuclear NiAHgCl2 [28,29], NiAHgBr2 [30], NiAZnCl2 [31,32], NiAZnBr2 [33], NiACoCl2 [34], NiACoBr2 [34], ZnACdBr2 [35], ZnAHgI2 [36] ONNO type Schiff base complexes have been reported. To the best of our knowledge, the structural characterization of the phenoxo-bridged heterodinuclear ZnANiCl2, ONNO type Schiff base complex, (2), is described here for the first time. This work reports the synthesis of two new phenoxo-bridged heterodinuclear NiIIAHgII (1) and ZnIIANiII (2) complexes along with their characterization, single crystal X-ray structures and thermal studies. Experimental section Materials and methods All reagents and solvents were purchased from Merck, Aldrich or Carlo Erba and used without further purification. Elemental analyses for the ligand and complex were carried out using standard methods with a Eurovector 3018 CHNS analyzer. IR spectra were recorded using a Perkin–Elmer 1600 series automatic recording FT-IR spectrophotometer with the KBr disk technique over the range 400–4000 cm1. The thermogravimetry/differential thermal analysis (TG/DTA) measurements were undertaken using a Perkin Elmer Diamond DTA/TG thermal analyzer. In this study, thermogravimetric curves were obtained using a flow rate of the nitrogen carrier gas (at 3 bar) of 200 mL/min and a heating rate of 20 °C/min and with ceramic crucibles.
slowly to the mixture with constant stirring. The solution was filtered and then allowed to stand at room temperature for three days. Blue crystals of complex 2 were collected by filtration and dried in an air atmosphere. Calcd. Found for 2 (C23H32Cl2N4NiO4Zn) Yield: 0.39 g. (62%), C, 44.3; H, 5.13; N, 8.98. Found: C, 43.7; H, 5.02; N, 8.82%. X-ray structure determination Intensity data for suitable single crystals of 1 and 2 were collected using an Oxford Diffraction Xcalibur-3 single crystal X-ray diffractometer equipped with a Mo Ka radiation source (k = 0.71073 Å at 296 K). Data collection and data reductions were performed using the CRYSALIS CCD and CRYSALIS RED programs [37]. The structures were solved by direct methods and refined using full-matrix least-squares against F2 using SHELXTL [38]. All non-hydrogen atoms were assigned anisotropic displacement parameters and refined without positional constraints. Hydrogen atoms were included in idealised positions with isotropic displacement parameters constrained to 1.5 times the Uequiv of their attached carbon atoms for methyl hydrogens, and 1.2 times the Uequiv of their attached carbon atoms for all others. The Level B Alerts result from the C3, C6, C8, C9, C23 atoms for complex 1 and the C20 atom for complex 2 which were refined isotropically due to its high thermal motion. The absolute structure was determined on the basis of the Flack parameter [39] x = 0.063(9) for 1 and 0.042(16) for 2. A Flack parameter value close to 0 is indicative of a non-centrosymmetric structure. Details of the data collection parameters and crystallographic information for the complexes are summarized in Table 1. Selected bond lengths and angles are listed in Table 2 for complex 1 and Table 3 for complex 2, respectively. Hydrogen bond geometries of the complexes are shown in Table 4. Molecular drawings were obtained using MERCURY [40]. The crystal structures of 1 and 2 along with the atom numbering scheme are given in Figs. 1 and 3, respectively. Packing diagrams are displayed in Fig. 2 for 1 and in Fig. 4 for 2.
Synthesis Synthesis of complex 1 N,N0 -bis(salicylidene)-1,3-propanediamine (H2L) was prepared by reacting a basic ethanolic solution of salicylaldehyde and 1,3diamino propane as described previously in the literature [33]. Triethylamine (Et3N) was added dropwise to the solution of Schiff base ligand (1 mmol, 0.282 g) in 20 mL DMF. A solution of NiCl2.6H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added to the DMF solution. The solution was stirred at the boiling point under an air atmosphere. A solution of HgCl2 (1 mmol, 0.271 g) in ethanol (20 mL) was added to the resulting solution and this too was stirred at the boiling point under an air atmosphere. The solution was filtered and then allowed to stand at room temperature for five days. Green crystals of complex 1 were collected by filtration and dried in an air atmosphere. Calcd. Found for 1 (C23H30Cl2HgN4NiO4): Yield: 0.51 g. (68%), C, 36.4; H, 3.96; N, 7.40. Found: C, 35.7; H, 4.12; N, 7.58%. Synthesis of complex 2 Complexes 1 and 2 were prepared using similar methods. Equivalent amounts of triethylamine (Et3N) was added dropwise to deprotonate the phenolic OH group of the solution Schiff base ligand (1 mmol, 0.282 g) in DMF (20 mL). To a solution of ZnCl2 (1 mmol, 0.135 g) in ethanol was added to the resulting solution and it was stirred at boiling point under an air atmosphere. A solution of NiCl2.6H2O (1 mmol, 0.237 g) in ethanol (20 mL) was added
Table 1 Crystal data and structure refinements for 1 and 2.
Empirical formula Formula weight Crystal system Space group Unit cell dimensions
Volume Z Density (calculated) Absorption coefficient h range for data collection Index ranges
Reflections collected Independent reflections Refinement method Goodness-of-fit on F2 R indices [I > 2r(I)] Flack parameter
1
2
C23H30Cl2HgN4NiO4 756.71 g mol1 Monoclinic Cc a = 10.5428 (11) Å b = 15.1258 (19) Å c = 17.350 (3) Å b = 97.479 (13)° 2743.3 (6) Å3 4 1.832 g.cm3 6.51 mm1
C23H32Cl2N4NiO4Zn 623.51 g mol1 Monoclinic Cc a = 10.4994 (5) Å b = 15.1545 (7) Å c = 17.1967 (6) Å b = 98.709 (4)° 2704.7 (2) Å3 4 1.531 g cm3 1.82 mm1
3.9–27.6°
3.9–28.8°
10 6 h 6 13, 19 6 k 6 19, 22 6 l 6 22 6649 3773 [Rint = 0.076]
8 6 h 6 14 20 6 k 6 20 23 6 l 6 23 7114 4386 [Rint = 0.024]
Full-matrix least-squares on F2 S = 0.71 R1 = 0.046, wR2 = 0.068 0.063(9)
Full-matrix least-squares on F2 S = 0.96 R1 = 0.041, wR2 = 0.115 0.042(16)
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A. Yardan et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 137 (2015) 351–356 Table 2 Some selected bond lengths [Å] and angles [°] for 1. Bond lengths (Å) Ni1AO1 Ni1AO2 Ni1AO3 Ni1AO4 Ni1AN1 Ni1AN2
1.980 2.008 2.136 2.159 2.043 2.032
(11) (9) (12) (12) (12) (15)
Bond angles (°) O1ANi1AO2 O1ANi1AN1 O3ANi1–O1 O3ANi1AO2 O3ANi1AN1 O3ANi1AN2 O4ANi1AO1 O4ANi1AO2 O4ANi1AO3 O4ANi1AN1 O4ANi1AN2
81.5 (4) 89.8 (6) 91.7 (5) 91.7 (4) 84.9 (4) 89.6 (5) 91.7 (5) 92.0 (4) 175.4 (5) 91.9 (4) 87.6 (5)
Hg1AO1 Hg1AO2 Hg1ACl1 Hg1ACl2
2.359 2.321 2.345 2.354
(10) (10) (4) (5)
N1ANi1AO2 N2ANi1AO1 N2ANi1AO2 N2ANi1AN1 O2AHg1ACl1 O2AHg1ACl2 Cl1AHg1ACl2 O2AHg1–O1 Cl1AHg1AO1 Cl2AHg1AO1 Ni1AO1AHg1 Ni1AO2AHg1
170.6 (6) 171.3 (5) 89.9 (5) 98.9 (6) 107.1 (3) 103.5 (3) 139.6 (3) 67.6 (3) 104.4 (3) 111.4 (3) 104.6 (4) 105.0 (4)
Fig. 1. DTA/TG/DTG curves of complex 1.
Table 3 Some selected bond lengths [Å] and angles [°] for 2. Bond lengths (Å) Zn1AN2 Zn1AN1 Zn1AO1 Zn1AO2 Zn1AO4 Zn1AO3
2.009 2.012 2.020 2.019 2.124 2.140
(4) (5) (4) (4) (4) (4)
Bond angles (°) N2AZn1AN1 N2AZn1AO1 N1AZn1AO1 N2AZn1AO2 N1AZn1AO2 O1AZn1AO2 N2AZn1AO4 N1AZn1AO4 O1AZn1AO4 O2AZn1AO4 N2AZn1AO3 N1AZn1AO3
99.7 (2) 169.53 (18) 90.80 (18) 90.76 (18) 169.44 (18) 78.79 (14) 88.54 (17) 86.99 (19) 92.35 (16) 91.62 (16) 90.22 (17) 90.64 (18)
Ni1AO2 Ni1AO1 Ni1ACl1 Ni1ACl2
1.985 2.003 2.200 2.224
(4) (4) (2) (2)
O1AZn1AO3 O2AZn1AO3 O4AZn1AO3 O2ANi1AO1 O2ANi1ACl1 O1ANi1ACl1 O2ANi1ACl2 O1ANi1ACl2 Cl1ANi1ACl2 Ni1AO1AZn1 Ni1AO2AZn1
89.34 (16) 91.01 (16) 177.10 (18) 80.01 (15) 112.00 (13) 116.38 (13) 111.94 (12) 111.77 (13) 118.52 (8) 100.04 (17) 100.70 (17)
Results and discussion IR spectra The interest of the IR spectrum of the title complexes lies mainly in the bands arising from the azomethine and hydroxyl groups of the ligands, and the carbonyl group from the DMF ligand.
Fig. 2. DTA/TG/DTG curves of complex 2.
The spectrum of the free ligand (H2L) shows significant bands at 1611 cm1 for C@N stretching, 2752–2748 cm1 for phenolic OAH stretching and 1294 cm1 for phenolic CAO. When the IR spectra obtained from complex 1 is compared with that from the free ligand, the complex exhibits a m(C@N) band at 1624 cm1 showing a shift to higher wavenumbers indicating that the nitrogen atom of the azomethine group is coordinated to the nickel (II) ion [41]. In addition, the phenolic m(OAH) band in the ligand spectrum disappeared in the complex spectrum [42]. These results prove the complexation [43]. The m(C@O) stretching vibration of
Table 4 Hydrogen bond geometry (Å, °) of compounds 1 and 2.
1 2 CAHp 1
2
a
DAH Aa
DAH
H A
D A
DAH A
Symmetry
C11AH11Cl2 C19AH19CCl1 C8AH8Cl1
0.93 0.96 0.93
2.76 2.92 2.88
3.603 3.708 3.711
151 140 150
x, y, 1/2 + z 1/2 + x, 1/2 + y, z x, y, 1/2 + z
C9AH9AR2 C20AH20BR2 C23AH23BR1 C5AH5R3 C16-H16AR2 C20AH20BR2 C23AH23BR3
0.97 0.96 0.96 0.93 0.97 0.96 0.96
2.96 2.98 2.67 2.94 2.86 2.92 2.73
3.836 3.468 3.552 3.689 3.736 3.527 3.494
151 113 153 139 150 122 137
x,y, 1/2 + z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 y, 1/2 + z x, y, 1/2 + z 1/2 + x, 1/2 + y, z 1/2 + x, 1/2 + y, z
D: Donor, A: Acceptor, [R1: C12C13C14C15C16C17, R2: C2C3C4C5C6C7 for 1]. [R3: C9C10C11C12C13C14, R2: C2C3C4C5C6C7 for 2].
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Decomposition of complex 1 starts at 53 °C and this step continues up to 134 °C. Two DMF molecules leave in this first step (calcd./ found: 19.3/17.8%) [47,48]. In the DTA curve, there is an endothermic peak at 119 °C for this event. The second weight loss between 134 and 468 °C was attributed to the departure of ligand (calcd./ found: 37.3/39.9%). Over the temperature range 468–654 °C two coordinated chlorides leave the structure with 9.9% weight loss observed compared with the calculated theoretical value of 9.4%. Complex 2 was thermally stable up to 120 °C and decomposition started at this temperature and finished at 1200 °C with four stages. The TG curve (Fig. 2) indicates that DMF molecules depart over the temperature range 119–198oC (calcd./found: 23.5/23.4%) [28,49]. Other steps between 198 and 1200 °C involve the loss of the ligand and two chlorides (calcd./found: 56.9/56.7%) and probably the formation of Zn-Ni as the final residue at 1200 °C (calcd./ found: 19.9/19.9%). Moreover, the thermogravimetric analyses reveal that complex 2 is more stable than complex 1. Fig. 3. Molecular structure of 1.
the DMF molecules can be assigned to the band at 1552 cm1 in the IR spectrum, which is lower than that in free DMF molecules (1655 cm1) because of the coordination of the DMF oxygen atoms to the zinc ion which is consistent with the results of X-ray analysis. Similarly, complex 2 exhibits a m(C@N) band at 1651 cm1 showing a shift to lower wavenumbers indicating that the nitrogen atom of azomethine group is coordinated to the zinc atom [44,45]. In addition, the phenolic m(OAH) band disappeared. The m(C@O) stretching vibration of the DMF molecules can be assigned to the band at 1551 cm1 in the IR spectrum [46].
Thermal analysis To examine the thermal stabilities of the complexes, thermogravimetric and differential thermal (TG/DTA) analyses were carried out in a nitrogen atmosphere at a heating rate of 20 °C/min from ambient temperature to 1200 °C. The DTA/TG/DTG diagrams of complexes 1 and 2 are shown in Figs. 1 and 2, respectively.
Crystal structure description of Complex 1 Complex 1 crystallizes in the monoclinic non-centrosymmetric chiral space group Cc and the asymmetric unit contains one molecule. The molecule comprises a binuclear heterometallic assembly of nickel(II) and mercury(II) in which the Ni(II) centre is connected to the [HgCl2] unit via two bridging phenolate oxygen atoms provided by the Schiff base anion. The molecular unit can be described as a dinuclear species with a six-coordinated nickel atom surrounded by the two phenolate oxygen and two imine nitrogen atoms of tetradentate Schiff base ligand occupying the equatorial positions and two oxygen atoms in the apical positions. The phenolate oxygen atoms bridge the mercury atom which is four-coordinated by those two oxygen atoms and two chlorine atoms. The [HgO2Cl2] unit undergoes severe distortions from ideal tetrahedral geometry which is reflected from its wide range of bond angles, being 67.57–139.59°. The coordination geometry around the nickel corresponds to an elongated octahedral structure because of the presence of the oxygen atoms in the apical positions with average distances of 2.15 Å, while the equatorial NiAN and NiAO bond distances are 1.979–2.043 Å. The deviation of Ni(II) ions from N2O2
Fig. 4. Molecular packing diagram of 1 in the bc plane (dashed lines denote Cl H interactions).
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coordination plane [O1AN1AN2AO2] is 0.026 Å. In complex 1, the intramolecular NiHg distance is 3.44 Å which is close to the values found in similar salen-type compounds [28]. Selected bond lengths and angles are listed in Table 2, which lie well within the range of reported values for corresponding bond lengths and angles of similar hetero-dinuclear complexes [28,29,50–54].
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Complex 1, revealed the presence of intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected (Table 4). In these interactions, the metal bound chlorine atoms Cl1 and Cl2 act as the H-bond acceptor while C11 and C19 atoms act as the H bond donor [55]. These intermolecular interactions result in the formation of a 3D structure. This hydrogen bonded polymeric networks lie in the bc axis and stacks along to the a axis. (Fig. 4). However, these dimeric units are further connected by C–H. . .p interactions (H. . .R = 2.96, 2.98 and 2.67 Å) to the other heterobimetallic dimers present in the unit cell (Table 4). Crystal structure description of Complex 2
Fig. 5. Molecular structure of 2.
Complex 2 crystallizes in the monoclinic non-centrosymmetric chiral space group Cc and the asymmetric unit contains one molecule. The molecule comprises a binuclear heterometallic assembly of zinc (II) and nickel (II) in which the Zn (II) centre is connected to the [NiCl2] unit via two bridging phenolate oxygen atoms contributed by the Schiff base anion. The molecular unit of complex 2 can be described as being a hetero-dinuclear species with a six-coordinated zinc atom and a four-coordinated nickel atom. The Ni (II) ion is bridged by two phenolate oxygen atoms and two chlorine atoms. The Zn (II) ion is surrounded by N2O2 donor atoms of the Schiff base ligand in the equatorial positions and two oxygen atoms in the apical positions (see Fig. 5). The [NiO2Cl2] unit deviates from ideal tetrahedral geometry with the bond angles ranging between
Fig. 6. (a) Molecular packing diagram of 2 along the c axis (dashed lines denote Cl H interactions), (b). Space filling representation of 2 as in Fig. 6a.
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80.00° and 118.52°. The coordination geometry around the Zn (II) ion corresponds to an elongated octahedral structure because of the presence of the oxygen atoms in the apical positions with average bond lengths of 2.13 Å, while the equatorial ZnAN and ZnAO bond distances are 2.008–2.020 Å. The deviation of Zn (II) ions from N2O2 coordination plane [O1AN1AN2AO2] is 0.011 Å and the intramolecular ZnNi distance is 3.44 Å. Selected bond lengths and angles are listed in Table 3, which lie well within the range of reported values for corresponding bond lengths and angles of similar hetero-dinuclear complexes [28,29,50–54]. Complex 2, revealed the presence of intermolecular CAHClAM interactions among the dinuclear complexes which are interconnected (Table 4). In this interaction, the metal bound chlorine atom Cl1 acts as the H-bond acceptor while the C8 atom acts as the H bond donor [55]. This intermolecular interaction results in the formation of infinite one dimensional zig-zag chains in the crystal lattice. The zig-zag chains propagate through the crystallographic c axis (Fig. 6a and b). However, these dimeric units are further connected by CAH. . .p interactions (H. . .R = 2.94, 2.86, 2.92 and 2.73 Å) to the other heterobimetallic dimers present in the unit cell (Table 4). Conclusion Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2 have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. CAH. . .p and CAHClAM interactions play a major role in controlling the molecular packing for complexes 1 and 2. In both structures the intermolecular CAHp separations are equal 2.9 Å and lie in the accepted distance range for this type of contact [39,56–58]. These intermolecular interactions result in the formation of a 3D structure for 1 and 1D zig-zag chains for 2. The thermogravimetric analyses illustrate that complex 2 is more stable than complex 1. Acknowledgements The financial support of the Scientific and Technical Research Council of Turkey (TUBITAK) Grants No: TBAG-108T431 and Balikesir University (Project No. 2007/10) is gratefully acknowledged. In addition, Yasemin Yahsi is also grateful to Dr. Lorenzo Sorace, Dr. Andrea Caneschi (Department of Chemistry, University of Florence) for the use of Xcalibur-3 diffractometer. We are also very grateful to Dr. Andrew Fisher for language corrections. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.08.091. References [1] C. Hopa, H. Yildirim, H. Kara, R. Kurtaran, M. Alkan, Spectrochim. Acta A 121 (2014) 282. [2] S. Celen, E. Gungor, H. Kara, D. Azaz, J. Coord. Chem. 66 (2013) 3170. [3] Y. Yahsi, H. Kara, Inorg. Chim. Acta 397 (2013) 110. [4] H. Kara, A. Azizoglu, A. Karaoglu, Y. Yahsi, E. Gungor, A. Caneschi, L. Sorace, Cryst. Eng. Comm. 14 (2012) 7320. [5] S.-G. Kang, H. Kim, S. Bang, C.H. Kwak, Inorg. Chim. Acta 396 (2013) 10. [6] K.R. Surati, B.T. Thaker, Spectrochim. Acta A 75 (2010) 235. [7] H. Sheykhi, E. Safaei, Spectrochim. Acta A 118 (2014) 915.
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