untitled European Journal of Chemistry 7 (4) (2016) 448‐453 European Journal of Chemistry ISSN 2153‐2249 (Print) / ISSN 2153‐2257 (Online)  2016 Atlanta Publishing House LLC ‐ All rights reserved ‐ Printed in the USA http://dx.doi.org/10.5155/eurjchem.7.4.448-453.1509 European Journal of Chemistry Journal webpage: www.eurjchem.com Preparation, characterization and crystal structure of dinuclear zinc(II) carboxylate complex with 1‐(pyridin‐4‐yl)ethanone and 4‐methylbenzoate based ligands Efdal Cimen 1, Ilkay Gumus 2,*, Omer Celik 3, Ebru Keskin 4 and Hakan Arslan 2 1 Department of Chemistry and Chemical Process Technology, Kars Vocational School, Kafkas University, Kars, TR‐36100, Turkey 2 Department of Chemistry, Faculty of Arts and Science, Mersin University, Mersin, TR‐33344, Turkey 3 Science and Technology Applied and Research Center, Dicle University, Sur, Diyarbakir, TR‐21280, Turkey 4 Advanced Technology Research and Application Center, Mersin University, Mersin, TR‐33343, Turkey * Corresponding author at: Department of Chemistry, Faculty of Arts and Science, Mersin University, Mersin, TR‐33344, Turkey. Tel.: +90.324.3610001/4559. Fax: +90.324.3610047. E‐mail address: ilkay.gumus@mersin.edu.tr (I. Gumus). ARTICLE INFORMATION ABSTRACT DOI: 10.5155/eurjchem.7.4.448-453.1509 Received: 13 November 2016 Accepted: 03 December 2016 Published online: 31 December 2016 Printed: 31 December 2016   The centrosymmetric binuclear complex, [Zn2(C8H7O2)4(C7H7NO)2], has been synthesized and characterized by FT‐IR and NMR methods. The obtained Zn(II) metal complex has been also characterized by a single crystal X‐ray diffraction study. Crystal data for C46H42N2O10Zn2: Monoclinic, Space group P21/c (no. 14), a = 10.4827(3) Å, b = 8.6141(2) Å, c = 24.7582(6) Å, β = 101.066(1) °, V = 2194.07(10) Å3, Z = 4, Dcalc = 1.383 g/cm3, 22545 reflections measured (3.96° ≤ 2Θ ≤ 52.74°), 4465 unique (Rint = 0.0388, Rsigma = 0.0333) which were used in all calculations. The final R1 was 0.0489 (I ≥ 2(I)) and wR2 was 0.1533 (all data). The four nearest oxygen atoms around each zinc ion form a distorted square‐planar arrangement, and the distorted square‐pyramidal coordination is completed by the nitrogen atom of the 1‐ (pyridin‐4‐yl)ethanone compound. KEYWORDS Synthesis Zinc complex Zinc carboxylate Crystal structure Centrosymmetric Dinuclear zinc(II) complex Cite this: Eur. J. Chem. 2016, 7(4), 448‐453 1. Introduction The zinc ion is of essential importance for biological processes due to the presence of zinc‐containing enzymes in biological systems. These enzymes can contain one, two or three zinc ions at the active binding sites, further the two zinc ions can connected to each other via the Zn⋅⋅⋅Zn bond, and the distance between them are generally in the range of 3.0‐3.5 Å [1‐6]. Zinc compounds supported by carboxylate ligands which structurally similar to zinc enzyme, are of great interest owing to their role in biochemical systems [7‐11]. At the same time, zinc carboxylates are attracting attention as highly active catalysts for the polymerization or copolymerization of a wide range of organic monomers [12‐15]. Carboxylates constitute an important class of ligands in the formation of coordination compounds [16‐24]. Because ambidentate nature of their can display a wide variety of metal coordination modes such as monodentate terminal, chelating, bidentate bridging and monodentate bridging modes (Figure 1), which lead to several types of compounds [25‐27]. The nature of the bridging environment between adjacent zinc ions varies significantly in the structures and often several different environments exist within the same structure. Figure 1. Carboxylate binding modes in metal complexes. Cimen et al. / European Journal of Chemistry 7 (4) (2016) 448‐453 449 Scheme 1 Here, we report the synthesis and characterization of dinuclear zinc(II) complex, tetrakis(μ‐4‐methylbenzoato‐ κ2O:Oˊ)‐bis[(μ‐acetylpyridine‐κN1)‐zinc(II), supported by car‐ boxylate ligands. Structural characterization of complex was achieved by single crystal X‐ray diffraction technique. 2. Experimental 2.1. Instrumentation Infrared measurement was recorded in the range 400‐ 4000 cm−1 on a Perkin Elmer Spectrum 100 series FT‐IR/FIR/ NIR Spectrometer Frontier, ATR Instrument. The NMR spectra were recorded in DMSO‐d6 solvent on Bruker Avance III 400 MHz NaNoBay FT‐NMR spectrophotometer using tetramethyl silane as an internal standard. Crystallographic measurements of the compound were carried out at 296(2) K using a Bruker APEX‐II CCD area‐detector diffractometer. The intensity data were collected using graphite monochromated Mo‐Kα radia‐ tion, λ = 0.71073 Å. Absorption corrections were applied with the program SADABS [28]. The structure was solved by direct methods SHELXS‐97 [29], and refined by full‐matrix least‐ squares techniques on F2 using SHELXL‐97 with refinement of F2 against all reflections. Hydrogen atoms were constrained by difference maps and were refined isotropically, and all non‐ hydrogen atoms were refined anisotropically. The molecular structure plots were prepared using PLATON [30] and ORTEP III [31]. The anisotropic thermal parameters and structure factors (observed and calculated), full list of bond distances, bond angles and torsional angles are given in supplementary materials. The geometric special details: all e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.’s are taken into account individually in the estimation of e.s.d.’s in distances, angles and torsion angles; correlations between e.s.d.’s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.’s is used for estimating e.s.d.’s involving l.s. planes. 2.2. Synthesis A solution of 1‐(pyridin‐4‐yl)ethanone (0.61 g, 5 mmol) in H2O (10 mL) and sodium 4‐methylbenzoate (1.58 g, 10 mmol) in H2O (250 mL) was added dropwise ZnSO4.H2O (0.90 g, 5 mmol) in H2O. The reaction mixture was stirred for 30 min in room temperature. The mixture was filtered and crystals were formed within five days at room temperature (Scheme 1). Tetrakis(μ‐4‐methylbenzoato‐κ2O: Oˊ)‐ bis[(μ‐acetylpyridi ne‐κN1)‐zinc(II)]: FT‐IR (ATR, ν cm‐1): 1630 ν(C=C)ring, 1562 v(COO‐)asym, 1401 ν(COO‐)sym, 1032 ν(C‐N)py, 2920 ν(C‐H)aliphatic, 475 v(Zn‐N). 1H NMR (400 MHz, DMSO‐d6, δ, ppm): 8.82 (dd, 4H, Ar‐H), 7.85 (s, 4H, Ar‐H), 7.83 (ddd, 8H, Ar‐H), 7.21 (dd, 8H, Ar‐H), 2.63 (s, 6H, CO‐CH3), 2.34 (s, 12H, Ph‐CH3). 13C NMR (100 MHz, DMSO‐d6, δ, ppm): 198.08, 171.84, 150.78, 142.65, 140.62, 131.90, 129.58, 128.46, 121.36, 26.88, 21.02. 3. Results and discussion The dinuclear Zn(II) complex was obtained from the reaction with ZnSO4.H2O metal salt of 1‐(pyridin‐4‐yl) etha‐ none and sodium 4‐methylbenzoate compounds in water at room temperature and characterized by various spectroscopic techniques and also by X‐ray crystallography. All the characterization data of the synthesized complex confirm the proposed structures. Scheme 1 outlines the synthesis of the complex. FT‐IR spectral analysis confirms the presence of charac‐ teristic groups in the Zn(II) complex. The main vibrational bands of the complex are given in the experimental section. The stretching vibrations of ν(CH) groups are observed in the region above 3000 cm‐1. The stretching vibrations of aliphatic ν(CH) groups of 1‐(pyridin‐4‐yl)ethanone are at 2952 cm‐1. The ν(C=O) stretching vibration band belong to 1‐(pyridin‐4‐ yl)ethanone ligands are showed at 1672 and 1707 cm‐1, respectively. The potential carboxylate binding modes for zinc complex can determine by infrared spectroscopy. For the IR spectra of carboxylates, the stretching vibrations of the carboxylate group νasym(COO) and νsym(COO) are characteristic. But, stretching vibrations belong to aromatic rings in both benzoate and N‐donor ligands can observe in the same region of the spectrum as the stretching vibrations of the carboxylate group. The value of Δν[νasym(COO)–νsym(COO)] can provide structural insight into the coordination mode of the carboxylate group [32,33]. These values are applied to assign the type of the carboxylate coordination in inorganic complexes [34‐38]. The Δ values determined from the IR spectra of the synthe‐ sized zinc complex. The synthesized complex has stretching νasym(COO) at 1562 cm‐1 and νsym(COO) at 1401 cm‐1 (Figure 1). The experimental Δν value 161 cm−1 which suggested, that zinc complex forms the paddle‐wheel centrosymmetric dimmer with four syn‐syn carboxylato bridges [39]. In the synthesized dinuclear zinc complex, the Δν value (161 cm‐1) is consistent with the coordination modes of the carboxylate group observed in the complex. The NMR spectrum of complex was recorded in DMSO‐d6. The NMR data of the obtained complex is given in the experimental section and are consistent with the structural results. 450 Cimen et al. / European Journal of Chemistry 7 (4) (2016) 448‐453 Figure 1. Infrared spectrum of the zinc complex. Figure 2. 1H NMR spectrum of the zinc complex. Figure 3. 13C NMR spectrum of the zinc complex. The signals belong to the Ph‐CH3 and CO‐CH3 groups of the ligands were observed in the most upfield as a singlet at δ 2.34 and 2.63 ppm in the 1H NMR spectrum, respectively. The protons of the aromatic rings are observed in the region approximately at δ ∼7‐8 ppm (Figure 2). The 13C NMR spectra displayed signals corresponding to the characteristic quarter‐ nary carbonyl and carboxylate groups at δ 198.08 and 171.84 ppm, respectively (Figure 3). The structure of complex was confirmed by the result of single crystal X‐ray diffraction determination. The synthesized dinuclear zinc complex has a paddle‐wheel type structure with two 1‐(pyridin‐4‐yl)ethanone ligands at axial positions and in each case there are four carboxylate ligands bridging the two zinc centers (Figure 4). Asymmetric unit contains half of whole molecule, and there is an inversion center in the middle of Zn– Zn bond. Cimen et al. / European Journal of Chemistry 7 (4) (2016) 448‐453 451 Table 1. Crystallogrphic data for the Zn(II) complex. Parameters [Zn2(C8H7O2)4(C7H7NO)2] Empirical formula C23H21NO5Zn Formula weight 456.78 Temperature (K) 296(2) Crystal system Monoclinic Space group P21/c a, (Å) 10.4827(3) b, (Å) 8.6141(2) c, (Å) 24.7582(6) β, (ᵒ) 101.0660(10) Volume (Å3) 2194.07(10) Z 4 Dcalc (g cm‐1) 1.383 Μ (mm‐1) 1.152 F(000) 944.0 Crystal size (mm3) 0.25 × 0.25 × 0.25 Radiation MoKα (λ = 0.71073) 2Θ range for data collection (°) 3.96‐58.92 Index ranges ‐14 ≤ h ≤ 14, ‐10 ≤ k ≤ 11, ‐34 ≤ l ≤ 34 Reflections collected 22545 Independent reflections 5872 [Rint = 0.0388, Rsigma = 0.0333] Data/restraints/parameters 5872/0/274 Goodness‐of‐fit on F2 1.048 Final R indexes (I≥2σ (I)) R1 = 0.0472, wR2 = 0.1470 Final R indexes (all data) R1 = 0.0733, wR2 = 0.1613 Largest diff. peak/hole / e Å‐3 0.44‐0.28 Figure 4. Crystal structure of dinuclear Zn(II) complex. The each Zn atom is one nitrogen and four oxygen donor atoms penta‐coordinated to form square pyramidal geometry. The paddle‐wheel type structure for dinuclear complex is similar with literature [40‐42]. The coordination sphere around each Zn atom in the complex is shown in Figure 5. The details of crystallographic data and structure refinement parameters are summarized in Table 1. The metal ligand bond distances and angles are listed in Tables 2 and 3. In the geometry of the complex, it is obser‐ ved that the orientation of the two planes of the 1‐(pyridin‐4‐ yl)ethanone rings are perpendicular to each other. Zn–O bond distances range from 2.0276(13) to 2.0512(15) Å, on an average, they are somewhat longer than values observed for a series of structurally characterised zinc benzoate complexes [43,44]. Zn–N bond distance is 2.0397(15) Å which is typical in Zn(II) complexes, and Zn–Zn distance is 2.9332(4) Å (Table 2). The bond lengths of all C‐O bonds of synthesized Zn(II) complex (C1‐O1 1.252(2), C1‐O2 1.252(2), O3‐C9i 1.250(3), O4‐C9 1.250(3) Å, i: 2‐x, 2‐y, 2‐z) are shorter than the normal C‐O single bond and longer than normal C=O double bond. The bond angles of O2i‐Zn1‐O1, O1‐Zn1‐N1, O4‐Zn1‐O3, O2 i‐Zn1‐ O4 and O4‐Zn1‐N1 are 159.84(6), 99.81(6), 159.85(6), 89.29(7) and 89.65(7) (i:2‐x, 2‐y, 2‐z), respectively. The dihedral angle between Zn1‐O1‐O2‐C1 and Zn‐O3‐O4‐C2 planes is 86.33°. The dihedral angles between the planar carboxylate groups O1‐O2‐C1 and O3‐O4‐C2 are 75.45°. Figure 5. The coordination sphere around zinc atom in the complex. 452 Cimen et al. / European Journal of Chemistry 7 (4) (2016) 448‐453 Table 2. Selected bond distances for the Zn(II) complex. Atom Atom Length (Å) Atom Atom Length (Å) Zn1 Zn1i 2.9332(4) C4 C5 1.376(3) Zn1 O1 2.0276(13) C5 C6 1.380(3) Zn1 O2 i 2.0339(14) C5 C8 1.506(3) Zn1 O3 2.0512(15) C6 C7 1.381(3) Zn1 O4 i 2.0348(16) C9 C10 1.497(3) Zn1 N1 2.0397(15) C10 C11 1.384(3) O1 C1 1.252(2) C10 C15 1.374(3) O2 Zn1 i 2.0338(14) C11 C12 1.376(4) O2 C1 1.252(2) C12 C13 1.377(4) O3 C9 1.250(3) C13 C14 1.370(5) O4 Zn1 i 2.0347(15) C13 C16 1.522(4) O4 C9 1.250(3) C14 C15 1.371(3) O5 C22 1.201(3) C17 C18 1.373(3) N1 C17 1.322(3) C18 C19 1.360(3) N1 C21 1.330(3) C19 C20 1.374(3) C1 C2 1.495(3) C19 C22 1.502(3) C2 C3 1.385(3) C20 C21 1.369(3) C2 C7 1.373(3) C22 C23 1.493(3) i 2‐x, 2‐y, 2‐z. Table 3. Selected bond angles for the Zn(II) complex. Atom Atom Atom Angle (˚) Atom Atom Atom Angle (˚) O1 Zn1 Zn1 i 80.71(4) C9 O3 Zn1 132.54(15) O1 Zn1 O2 i 159.84(6) C9 O4 Zn1 i 121.69(15) O1 Zn1 O3 85.59(6) C17 N1 Zn1 120.79(13) O1 Zn1 O4 i 89.65(7) C17 N1 C21 117.26(17) O1 Zn1 N1 99.81(6) C21 N1 Zn1 121.93(14) O21 Zn1 Zn1 i 79.15(4) C5 C4 C3 121.8(2) O21 Zn1 O3 88.51(7) C4 C5 C6 117.2(2) O21 Zn1 O4 i 89.29(7) C4 C5 C8 121.1(2) O21 Zn1 N1 100.16(6) C6 C5 C8 121.7(2) O3 Zn1 Zn1 i 75.57(5) C7 C6 C5 121.6(2) O41 Zn1 Zn1 i 84.34(5) C2 C7 C6 120.6(2) O41 Zn1 O3 159.85(6) O3 C9 O4 125.4(2) O41 Zn1 N1 100.90(7) O3 C9 C10 116.89(19) i 2‐x, 2‐y, 2‐z. Figure 6. The intermolecular C–H···O interactions of dinuclear Zn(II) complex. The C–H···O interactions are shown as green dashed lines. The dinuclear complex present in the crystal lattice of the self‐assembly are held together by weak C–H···O interactions. The intermolecular C–H···O (C10‐H8···O4, 3.581 Å; C11‐ H14···O4, 3.329 Å; C14‐H14···O2, 2.945 Å) interactions of dinuclear Zn(II) complex is shown in Figure 6. The packing diagram of zinc complex is also shown in Figure 7. 4. Conclusions A new class of compound formed by a dinuclear zinc carboxylate complex were prepared and characterized by IR, NMR spectroscopy and single crystal X‐ray diffraction. Single crystal analysis and Δ values determined from the IR spectra revealed that the synthesized zinc complex forms the paddle‐ wheel centrosymmetric dimmer with four syn‐syn carboxylato bridges. Also, the dinuclear complex present in the crystal lattice of the self‐assembly are held together by weak C–H···O interactions. Figure 7. The packing diagram of Zn(II) complex. Cimen et al. / European Journal of Chemistry 7 (4) (2016) 448‐453 453 Acknowledgements This study was supported by the Research Fund of Mersin University in Turkey with Project Number: 2015‐AP4‐1162. Supplementary material CCDC‐1515549 contains the supplementary crystallo‐ graphic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by e‐mailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44(0)1223‐336033. References [1]. Krezel, A.; Maret, W. Arch. Biochem. Biophys. 2016, 611(1), 3‐19. [2]. Jurowski, K.; Szewczyk, B.; Nowak, G.; Piekoszewski, W. J. Bio. Inorg. Chem. 2014, 19, 1069‐1079. [3]. Lipscomb, W. N.; Strater, N. Chem. Rev. 1996, 96, 2375‐2434. [4]. Wilcox, D. E. Chem. Rev. 1996, 96, 2435‐2458. [5]. Strater, N.; Lipscomb, W. N.; Klabunde, T.; Krebs, B. Angew. Chem. Int. Edit. 1996, 35, 2024‐2055. [6]. Steinhagen, H.; Helmchem, G. Angew. Chem. Int. Edit. 1996, 35, 2339‐ 2342. [7]. Jacobsen, F. E.; Lewis, J. A.; Cohen, S. M. J. Am. Chem. Soc. 2006, 128, 3156‐3157. [8]. Weston, J. Chem. Rev. 2005, 105, 2151‐2174. [9]. Parkin, G. Chem. Rev. 2004, 104, 699‐768. [10]. Horrocks, W. D.; Ishley, J. N.; Whittle, R. R. Inorg. Chem. 1982, 21, 3265‐3269. [11]. Horrocks, W. D.; Ishley, J. N.; Whittle, R. R. Inorg. Chem. 1982, 21, 3270‐3274. [12]. W. Kuran, Principles of Coordination Polymerisation, Wiley, Chichester, chap. 9, 2001. [13]. Coates, G. W.; Moore, D. R. Angew. Chem. 2004, 116, 6784‐6806. [14]. Coates, G. W.; Moore, D. R. Angew. Chem. Int. Edit. 2004, 43, 6618‐ 6639. [15]. Darensbourg, D. J. Chem. Rev. 2007, 107, 2388‐2410. [16]. Pedireddi, V. R.; Varughese, S. Inorg. Chem. 2004, 43, 450‐457. [17]. Ng, M. T.; Deivaraj, T. C.; Klooster, W. T.; McIntyre, G. J.; Vittal, J. J. Chem‐Eur J. 2004, 10, 5853‐5859. [18]. Tong, M. L.; Chen, H. J.; Chen, X. M. Inorg. Chem. 2000, 39, 2235‐2238. [19]. Zhang, Y. S.; Enright, G. D.; Breeze, S. R.; Wang, S. New J. Chem. 1999, 39, 625‐628. [20]. Wang, R.; Jiang, F.; Zhou, Y.; Han, L.; Hong, M. Inorg. Chim. Acta 2004, 358, 545‐554. [21]. Zhu, L. G.; Kitagawa, S.; Miyasaka, H.; Chang, H. C. Inorg. Chim. Acta 2003, 355, 121‐127. [22]. Toh, N. L.; Nagarathinam, M.; Vittal, J. J. Angew. Chem. Int. Edit. 2005, 44, 2237‐2041. [23]. Conerney, B.; Jensen, P.; Kruger, P. E.; Moubaraki, B.; Murray, K. S. Cryst. Eng. Comm. 2003, 5, 454‐458. [24]. Carballo, R.; Covelo, B.; El‐Fallah, M. S.; Ribas, J.; Vazquez‐Lopez, E. M. Cryst. Growth Des. 2007, 7, 1069‐1077. [25]. Curtiss, A. B. S.; Bera, M.; Musie, G. T.; Powell, D. R. Dalton Trans. 2008, 2717‐2724. [26]. Aroraa, H.; Mukherjee, R. New J. Chem. 2010, 34, 2357‐2365. [27]. Zelenak, V.; Vargova, Z. Gyoryova, K. Spectrochim. Acta A 2007, 66, 262‐272. [28]. Bruker, SADABS. Bruker AXS Inc. , Madison, Wisconsin, USA, 2007. [29]. Sheldrick, G. M. Acta Crystallogr. A, 2008, 64, 112‐122. [30]. Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 568. [31]. Morsali, A.; Masoomi. M. Y. Coord. Chem. Rev. 2009, 253, 1882‐1905. [32]. Tackett, J. E. Appl. Spectrosc. 1989, 43, 483‐489. [33]. Nakamoto, K. Infrared Spectra of Inorganic and Coordination Compounds, 4th ed. , Wiley, New York, 1986. [34]. Deacon, G. B.; Phillip, R. J. Coord. Chem. Rev. 1980, 33, 227‐250. [35]. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds, John Wiley & Sons, New York, 1997. [36]. Martini, D.; Pellei, M.; Pettinari, C.; Skelton, B. W.; White, A. H. Inorg. Chim. Acta 2002, 333, 72‐82. [37]. Lewandowski, W.; Kalinowska, M.; Lewandowska, H. Inorg. Chim. Acta 2005, 358, 2155‐2166. [38]. Czakis‐Sulikowska, D.; Czylkowska, A. J. Therm. Anal. Calorim. 2007, 90, 681‐686. [39]. Zelenak, V.; Vargova, Z.; Gyoryova, K. Spectrochim. Acta A 2007, 66, 262‐272. [40]. Karmaker, A.; Sarma, R. J.; Baruah, J. B. Inorg. Chem. Commun. 2006, 9, 1169‐1172. [41]. Uhlenbrock, S.; Krebs, B. Angew. Chem. Int. Edit. 1992, 31, 1647‐1648. [42]. Clegg, W.; Little R. I.; Straughan, B. P. J. Chem. Soc., Dalton Trans. 1986, 6, 1283‐1288. [43]. Clegg, W.; Harbron, D. R.; Homan, C. D.; Hunt, P. A.; Little, I. R.; Straughan, B. P. Inorg. Chim. Acta 1991, 186, 51‐60. [44]. Clegg, W.; Harbron, D. R.; Hunt, P. A.; Little, I. R.; Straughan, B. P. Acta Crystallogr. C 1990, 46, 750‐753.