Synthesis and spectroscopic study of transition metal complexes of tridentate ligand formed by direct condensation of o-vanillin and 2-aminophenol: X-ray structural characterization of the zinc(II) complex European Journal of Chemistry 9 (4) (2018) 281-286 European Journal of Chemistry View Journal Online View Article Online Synthesis and spectroscopic study of transition metal complexes of tridentate ligand formed by direct condensation of o-vanillin and 2-aminophenol: X-ray structural characterization of the zinc(II) complex Amadou Gueye 1, Farba Bouyagui Tamboura 2,*, Jean-Marc Planeix 3, Nathalie Gruber 3 and Mohamed Gaye 1 1 Department of Chemistry, University Cheikh Anta Diop, Dakar 12500, Senegal gueyeamadou23@gmail.com (A.G.), mohamedl.gaye@ucad.edu.sn (M.G.) 2 Department of Chemistry, University Alioune DIOP, Bambey 21400, Senegal farba.tamboura@uadb.edu.sn (F.B.T.) 3 Laboratoire de Tectonique Moléculaire du Solide (UMR 7140), Chimie de la Matière Complexe, Université de Strasbourg, Institut Le Bel, 4 rue Blaise Pascal, F- 67008 Strasbourg, France planeix@unistra.fr (J.M.P.), ngruber@unistra.fr (N.G.) * Corresponding author at: Department of Chemistry, University Alioune DIOP, Bambey 21400, Senegal. Tel: +221.7.72381908 Fax: +221.3.39733093 e-mail: farba.tamboura@uadb.edu.sn (F.B. Tamboura). 10.5155/eurjchem.9.4.281-286.1761 Received: 09 June 2018 Received in revised form: 08 August 2018 Accepted: 28 August 2018 Published online: 31 December 2018 Printed: 31 December 2018 The reactions of the Schiff base 2-((2-hydroxyphenylimino)methyl)-6-methoxyphenol (H2L), obtained by direct condensation of 2-aminophenol and 2-hydroxy-3-methoxybenzaldehyde, with some transition metal ions (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) afforded complexes of general formulae [M2(L)2(solvent)x] (M: Mn, Co, Ni, Cu or Zn; Solvent: DMSO or H2O). These compounds were characterized by elemental analysis, UV-Vis, IR, 1H- and 13C-NMR spectroscopies, molar conductivity and room temperature magnetic measurements. The structure of zinc(II) complex has been determined by X-ray crystallography. Crystal data for C32H34N2O8S2Zn2 (M =769.47 g/mol): Orthorhombic, space group Pbca (no. 61), a = 16.3176(7) Å, b = 9.1247(3) Å, c = 21.8274(10) Å, V = 3250.0(2) Å3, Z = 4, T = 173(2) K, μ(MoKα) = 1.658 mm-1, Dcalc = 1.573 g/cm3, 28116 reflections measured (4.5° ≤ 2Θ ≤ 60.3°), 4457 unique (Rint = 0.0409, Rsigma = 0.0371) which were used in all calculations. The final R1 was 0.0307(0.0466) and wR2 was 0.0649 (0.0701) (all data). The coordination sphere of the Zn center is best described as a trigonal bipyramid. Schiff base Benzaldehyde Metal complexes Trigonal bipyramidal X-ray crystallography Single crystal structure Cite this: Eur. J. Chem. 2018, 9(4), 281-286 Journal website: www.eurjchem.com 1. Introduction The Schiff bases obtained by condensation of 2-amino phenol with a keto-precursor are widely used in the synthesis of transition metal complexes [1-4]. These complexes are of particular interest for the magnetism [5], catalysis [6] or medicine [7] sectors. Some of these complexes are also repor- ted in the literature as antioxidants [8] or antibacterial agents [9,10]. Original structures are obtained thanks to the different modes of coordination of these ligands [11-14]. In recent years, these basic types of Schiff have been used to prepare metallobiosite analogues such as phenoxazinone synthase [15]. It is in this context that we decided to study the behavior of the Schiff base obtained from 2-aminophenol and o-vanillin in the presence of transition metals. Several complexes are isolated and characterized by different techniques. 2. Experimental 2.1. Materials and procedures 2-Aminophenol, 2-hydroxy-3-methoxybenzaldehyde as well as M(OAc)2.nH2O (M = Mn(II), (Co(II), Ni(II), Cu(II) or Zn(II)) were commercial products (from Alfa and Aldrich) and were used without further purification. Solvents were of reagent grade and were purified by the usual methods. Elemental analyses were performed in a Carlo-Erba EA microanalyser. Infrared spectra were recorded as KBr discs on a Bruker IFS-66V spectrophotometer. LSI-MS were recorded using a Micromass Autospec spectrometer with 3-nitrobenzyl alcohol as the matrix. The 1H- and 13C-NMR spectra were recorded in DMSO-d6 on a Bruker 500 MHz spectrometer at room temperature using TMS as an internal reference. ABSTRACT RESEARCH ARTICLE KEYWORDS European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2018 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. http://dx.doi.org/10.5155/eurjchem.9.4.281-286.1761 http://dx.doi.org/10.5155/eurjchem.9.4.281-286.1761 https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.9.4.281-286.1761&domain=pdf&date_stamp=2018-12-31 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.9.4.281-286.1761 mailto:gueyeamadou23@gmail.com mailto:mohamedl.gaye@ucad.edu.sn mailto:farba.tamboura@uadb.edu.sn mailto:planeix@unistra.fr mailto:ngruber@unistra.fr mailto:farba.tamboura@uadb.edu.sn http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.9.4.281-286.1761&domain=pdf&date_stamp=2018-12-31� 282 Gueye et al. / European Journal of Chemistry 9 (4) (2018) 281-286 12 3 4 5 6 1' 2'3' 4' 5' 6' OH O N OH CH3OH NH2 OH CH3 O O H Ethanol Reflux 3 hours Scheme 1 O N O O NO M M OH2 OH2 H2O H2O M(OAc)2 O N O O N O Zn Zn S H3C CH3 O SH3C CH3 O Ethanol Zn(OAc)2 Ethanol/DMSO OCH3 OCH3 H3CO OCH3 OH O N OH CH3 OH O N OH CH3 2 2 Scheme 2. Proposed structures for the binuclear complexes [M2(L)2(H2O)4]·nH2O. M = Mn2+, Cu2+ (n=1); M = Co2+, Ni2+ (n=2) and [Zn2(L)2(DMSO)2]. The UV-Vis spectra were run on a Shimadzu UV-2501 PC Recording spectrophotometer (1000-200 nm). The molar conductance of 1×10-3 M in DMSO solutions of the metal complexes was measured at 25 °C using a WTW LF-330 conductivity meter with a WTW conductivity cell. Room temperature magnetic susceptibilities of the powdered samples were measured using a Johnson Mattey scientific magnetic susceptibility balance (Calibrant: Hg[Co(SCN)4]). Melting points were recorded on a Büchi apparatus and are uncorrected. 2.2. Synthesis of 2-((2-hydroxyphenylimino)methyl)-6- methoxyphenol 2-Aminophenol (2 g, 21.2 mmol) and 2-hydroxy-3-met hoxybenzaldehyde (3.22 g, 21.2 mmol) were refluxed during 3 hours in ethanol (40 mL). On cooling an orange precipitate appeared and was isolated by filtration. The solid was washed with cold ethanol and dried on P2O5 in a desiccator to yield monohydrated 2-((2-hydroxyphenylimino)methyl)-6-met- hoxyphenol (Scheme 1). 2-((2-Hydroxyphenylimino)methyl)-6-methoxyphenol: Color: Orange. Yield: 76%. M.p.: 202-205 °C. IR (KBr, ν, cm-1): 1615 (C=N), 1599-1457 (C=C aromatic), 1328 (C-Ophenolic), 1240 (C-Oether), 3100 (O-H (phenol) and H2O). 1H NMR (500 MHz, DMSO-d6, δ, ppm): 3.80 (s, 3H, OCH3), 6.75-7.40 (m, 7H, Ar-H), 9.00 (s, 1H, H-C=N), 9.80-10.00 (s, 2H, OH). 13C NMR (125 MHz, DMSO-d6, δ, ppm): 56.50 (OCH3), 115 (H-C6’), 117 (H-C5), 119 (H-C4), 120 (H-C4’), 121 (H-C3), 124 (H-C3’), 128 (H-C5’), 135 (C2), 148 (C2’), 151 (C1), 153 (C1’), 153 (C6), 162 (H-C=N). UV-Vis (Liquid, λ, nm): 280, 350. MS (ESI-TOF, m/z): 262.1 [H2LH]+. Anal. calcd. for C14H15NO4: C, 64.36; H, 5.79; N, 5.36. Found: C, 64.26; H, 5.81; N, 5.40%. 2.3. Synthesis of the complexes H2L.H2O (10 mg, 0.41 mmol) was dissolved in ethanol (10 mL) to give an orange solution. The appropriate acetate salt (0.41 mmol) was added. The resulting mixture was stirred and refluxed for two hours. On cooling the suspension was filtered and the resulting solid was dried on P2O5 in a desiccator. A DMSO solution of the zinc(II) complex afforded by crystals suitable for X-ray analysis after one week (Scheme 2). Tetraaqua-bis[µ2-N-(2-oxyphenyl)-3-methoxysalicylaldimi nato]-di-manganese hydrate, [Mn2(C14H11NO3)2(H2O)4].H2O: Yield: 58 %. IR (KBr, ν, cm-1): 1605, 1478, 1388, 1307, 1229. Anal. calcd. for Mn2C28H32N2O11: C, 49.28; H, 4.73; N, 4.10. Found: C, 49.22; H, 4.80; N, 4.08%. UV-Vis (Liquid, λ, nm): 266, 313, 400, 427, 457. µeff = 7.87 MB. Ʌ (Ω-1.cm2.mol-1): fresh solution: 5.0; after 15 days: 12.0. Tetraaqua-bis[µ2-N-(2-oxyphenyl)-3-methoxysalicylaldi minato]-di-cobalt dehydrate, [Co2(C14H11NO3)2(H2O)4].2H2O: Yield: 58 %. IR (KBr, ν, cm-1): 1606, 1480, 1381, 1307, 1296, 1229. Anal. calcd. for Co2C28H34N2O12: C, 47.47; H, 4.84; N, 3.95. Found: C, 47.43; H, 4.80; N, 3.97%. UV-Vis (Liquid, λ, nm): 200, 266, 442. µeff = 7.02 MB. Ʌ (Ω-1.cm2.mol-1): fresh solution: 9.0; after 15 days: 15.0. Tetraaqua-bis[µ2-N-(2-oxyphenyl)-3-methoxysalicylaldi- minato]-di-nickel dehydrate, [Ni2(C14H11NO3)2(H2O)4].2H2O: Yield: 58 %. Anal. calcd. for Ni2C28H34N2O12: C, 47.50; H, 4.84; N, 3.96. Found: C, 47.46; H, 4.86; N, 3.92%. IR (KBr, ν, cm-1): 1608, 1584, 1540, 1477, 1457, 1432, 1379, 1314, 1278, 1218, 2018 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.9.4.281-286.1761 Gueye et al. / European Journal of Chemistry 9 (4) (2018) 281-286 283 Table 1. Crystallographic data and refinement parameters for [Zn2(L)2(DMSO)2]. Parameters Complex Chemical formula C32H34N2O8S2Zn2 Formula weight (g/mol) 769.47 Temperature (K) 173(2) Crystal system Orthorhombic Space group Pbca Wavelength 0.71073 Å Crystal size (mm) 0.090 × 0.090 × 0.110 a (Å) 16.3176(7) b (Å) 9.1247(3) c (Å) 21.8274(10) Volume (Å3) 3250.0(2) Z 4 Dcalc (g/cm3) 1.573 µ (mm-1) 1.658 F(000) 1584 2θ range for data collection (°) 2.25 to 30.15 Index ranges -17 ≤ h ≤ 21, -12 ≤ k ≤ 9, -30 ≤ l ≤ 22 Reflections collected 28116 Independent reflections 4457 [R(int) = 0.0409] Data / restraints / parameters 4457 / 0 / 211 Goodness-of-fit on F2 1.016 Final R Indices [I>2σ(I)] R1 = 0.0307 ; wR2 = 0.0649 Final R Indices (all data) R1 = 0.0466 ; wR2 = 0.0701 Largest diff. peak and hole (e.Å-3) 0.352 / -0.354 1178. UV-Vis (Liquid, λ, nm): 266, 300, 336, 433. µeff = 3.74 MB. Ʌ (Ω-1.cm2.mol-1): fresh solution: 11.0; after 15 days: 11.0. Tetraaqua-bis[µ2-N-(2-oxyphenyl)-3-methoxysalicylaldi minato]-di-copper hydrate, [Cu2(C14H11NO3)2(H2O)4].H2O: Yield: 58 %. IR (KBr, ν, cm-1): 1610, 1600, 1580, 1541, 1479, 1461, 1435, 1381, 1317, 1289, 1270, 1246, 1183. Anal. calcd. for Cu2C28H32N2O11: C, 48.07; H, 4.61; N, 4.00. Found: C, 48.05; H, 4.58; N, 3.98%. UV-vis (liquid, λ (nm)): 287, 315, 404, 435, 462. µeff = 0.64 MB. Ʌ (Ω-1.cm2.mol-1): fresh solution: 4.0; after 15 days: 6.0. Bis[µ2-N-(2-oxyphenyl)-3-methoxysalicylaldiminato]-bis(di methylsulfoxide)-di-zinc, [Zn2(C14H11NO3)2(C2H6SO)2]: Yield: 58 %. IR (KBr, ν, cm-1): 1601, 1581, 1535, 1474, 1433, 1385, 1290, 1258, 1214, 1179. Anal. calcd. for Zn2C32H34N2S2O8: C, 49.95; H, 4.45; N, 3.64. Found: C, 49.92; H, 4.42; N, 3.61%. UV-Vis (liquid, λ (nm)): 283, 342, 432. µeff = Diamagnetic. Ʌ (Ω-1.cm2.mol-1): fresh solution: 6.0; after 15 days: 8.0. 2.4. X-ray data collection, structure determination and refinement Single crystals of C32H34N2O8S2Zn2 were grown by slow evaporation of DMSO solution of the complex. A suitable crystal was selected and mounted on a Bruker APEX-II CCD diffractometer with graphite monochromatized MoKα radiation (λ = 0.71073 Å). The crystal was kept at 173(2) K during data collection. Details of the X-ray crystal structure solution and refinement are given in Table 1. Using Olex2 [16], the structure was solved with the ShelXT [17] structure solution program using direct methods and refined with the ShelXL [18] refinement package using CGLS minimization. 3. Results and discussion 3.1. Formation of [M2(L)2(Solvent)x].yH2O Formation of the title M(II) complex was readily achieved by equimolecular reaction of M(OAc)2.4H2O (M = Mn, Co, Ni, Cu and Zn) and the Schiff base H2L in ethanol under reflux (Scheme 2). The instant color change of the H2L solution upon addition of the ethanolic solution of M(OAc)2.4H2O indicated immediate occurrence of the coordination of the Metal(II) to the metal- binding sites of the acyclic ligand. The precipitate which appears during stirring and refluxing was filtered after cooling the solution. Additional compound was recovered by slow evaporation of the filtrate. Slow evaporation of a DMSO solution of the zinc(II) compound gave crystals suitable for X- ray analysis. 3.2. Characterization The acyclic Schiff bases H2L have been prepared following a method well known in the literature [19,20]. The synthesis of the ligand was achieved in a one-step procedure using the direct condensation of 2-aminophenol and 3-hydroxy-2- metoxybenzaldehyde in a quantitative yield (Scheme 1). The IR spectrum of the ligand shows a moderate-intensity absorp- tion at ca. 1615 cm-1 which is attributable to the ν(C=N). The bands in the region 1599-1457 cm-1 are assigned to the aromatic ν(C=C) vibration and the intense absorption near 3100-3200 cm-1 is assigned to ν(O-H) of the phenol group and H2O. The 1H and 13C NMR spectra of the ligand were recorded in DMSO-d6. The 1H NMR spectrum of the compound revealed a singlet signal at δ 3.80 ppm which is assigned to the methoxy group (OCH3). The complex signals appearing in the range δ 6.75-7.40 ppm are attributable to aromatic protons (Ar-H). The singlet at δ 9.00 ppm is due to a unique iminic proton (H- C=N). On the 1H spectrum, two broad singlets signals appear in the range δ 9.8-10.0 ppm and are attributable to two phenolic protons which are implicated in hydrogen bond interaction. These observations confirm that the reaction is a condensation between the 2-aminophenol and 2-hydroxy-3-methoxy- benzaldehyde. The 13C NMR confirmed these facts. The signal at δ 163 ppm is assigned to –C=N group. The aromatic quaternary carbon atoms show signals at δ 148 (=C-OCH3), 151 (=C-OH) and 153 ppm (=C-OCH3) while the secondary carbon atoms signals appear at 119 (HC-C=) and 135 (=C-N). The signal of the methoxy group (OCH3) is pointed at δ 56.50 ppm. The reactions of H2L with acetate metal salts in 1:1 molar ratio were investigated and the complexation was performed by mixing ethanol solutions of both ligand and metal salt. In all cases the complexes appear to be air stable and soluble in common organic solvents. Crystals suitable for X-ray analysis were obtained by slow evaporation of the DMSO solution of the zinc complex. All compounds are characterized by elemen- tal analysis (C, N, H), IR spectroscopy, molar conductivity, magnetic measurements, and X-ray diffraction for the zinc complex. Upon complexation of H2L with M(II) ions (M: Mn, Co, 2018 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.9.4.281-286.1761 284 Gueye et al. / European Journal of Chemistry 9 (4) (2018) 281-286 Table 2. Electronic data, magnetic moments and conductance data of the complexes. Compound UV Bands Λ (Ω-1cm2mol-1) μ/μB π → π*, n→ π*, MLCT d→d Fresh Two weeks after H2L = C14H13NO3 275, 350, 460 [Ni2(L)2(H2O)4]·2H2O 266, 300, 336 433, 677 11.0 11.0 3.74 [Cu2(L)2(H2O)4]·H2O 287, 315, 328, 406 462, 636 4.0 6.0 0.64 [Mn2(L)2(H2O)4]·H2O 266, 313, 400 446, 600 5.0 12.0 5.87 [Co2(L)2(H2O)4]·2H2O 200, 266, 442 470, 675 9.0 15.0 7.02 [Zn2(L)2(C2H6SO)2] 283, 342, 432 - 6.0 8.0 Dia. Figure 1. Crystal structure of the binuclear complex [Zn2(L)2(DMSO)2], showing partially the atom numbering scheme. Symmetry code (5): -x, -y, -z. Ni, Cu or Zn), an significant shift of the C=N band to lower frequency is observed on comparison to the corresponding band of the free ligand. This fact is indicative of the participation of the imine group in the coordination [21]. The bands of the C-O phenolic group, appearing in the range 1240-1227 cm-1 in the IR spectra of the complexes are suggesting an interaction between the metal ion and the oxygen atom. Two bands in the high frequencies at ~3448 and ~3200 cm-1 are observed and are attributable, respectively, to the ν(OH) of the coordinated water molecule and the lattice water molecule. The electronic spectral data of the complexes are recorded and the main bands are listed in Table 2. The assignments are made by comparison with literature data [21,22]. In the case of phenolic ligand, a π → π* band which is observed around 200- 250 nm is correlated to the electrons transfer in phenyl rings [22]. The band in the regions 300-350 nm and 350-400 nm are respectively due to π → π* and n → π* electron transfer in imine function [22]. The intense band observed in the spectra of the Cu, Ni and Co complexes near 250 nm and is assigned to π → π* transition of the aromatic rings. In the region 300-445 nm intense bands are observed and are assigned to n → π* transition in imine function [21,22]. In the electronic spectra of the complexes bands of d→d transitions are observed. The electronic spectrum of the Mn(II) complex displayed two bands with very low intensities in the visible at 446 and 600 nm which are probably due, respectively, to the electronic transition 6A1→ 4T2g and 6A1→ 4T1g are in accordance with an octahedral geometry around Mn(II) ion [23]. Two bands are pointed at 433 and 677 nm in the Ni(II) complex spectrum. The third transition band has not been pointed due to the low intensity. These values are typical of octahedral Ni(II) complexes and they are attributed, respectively, to 3A2g → 3T2g(P) and 3A2g → 3T1g(F) transitions [24]. In the spectrum of the Cu (II) complex, the bands at 462 and 636 nm are both assigned to d → d transition [25, 26]. The broadness of the band at 636 nm is indicative of a hexacoordinated environment around the copper ions. For the cobalt(II) complex the bands pointed at 470 and 675 nm are assignable, respectively, to 2Eg → 2T2g and 2Eg → 2T1g(P) transitions. These bands are typical for an octahedral environment around Co(II) ions [27]. The spectrum of the Zn2+ complex which has a d10 metal center presents no absorption band over 400 nm. While the Zn(II) is diamagnetic, Mn(II), Ni(II) and Cu(II) complexes are paramagnetic and exhibit room temperature magnetic moments in solid state. The magnetic moment of the manganese(II) complex is 5.87 μB. This value is in accordance with the presence of five unpaired electrons and is indicative of a high spin d5 configuration. These findings support octahedral geometry around the Mn2+ ions [28]. The magnetic moment of the dinuclear nickel(II) complex value of 3.74 μB is lower than the value expected for two Ni2+ ions in octahedral environment. This fact is indicative of antiferromagnetic interaction between the two centers a high spin octahedral complex [29]. The value of the magnetic moment at room temperature of the dinuclear cobalt complex is 7.02 μB. This value is in accordance with the presence of two high-spin Co(II) ions having a spin-orbit contribution and is indicative of octahedral environments around the metal centers [30]. The dinuclear Cu2+ complex presents at room temperature magnetic moment of 0.64 μB. This value is much smaller than the expected spin only calculated value. This observation is indicative of a very strong anti-ferromagnetic coupling between the two copper(II) ions via the phenoxo oxygen atoms acting as bridges [31]. Molar conductivities were measured for freshly prepared DMF solutions and after standing for two weeks (Table 2). The conductivities increased very slightly with time in DMF for all the complexes. For both complexes, the conductance values are observed in the range 04-15 cm2.Ω-1.mol-1. These obser- vations are indicative of a non-electrolyte solution in nature [32]. 3.3. Structure determination The crystal structure of the [Zn2(L)2(DMSO)2] (Figure 1) was solved and refined using the Bruker SHELXTL Software Package. The complex crystallizes in the orthorhombic crystal system with the centrosymmetric space group Pbca. Selected bond distances and angles are listed in Table 3. 2018 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.9.4.281-286.1761 Gueye et al. / European Journal of Chemistry 9 (4) (2018) 281-286 285 Table 3. Selected geometric parameters (Å, °). Bond lengths Zn1-O1 1.9679(11) Zn1-O3 2.0104(11) Zn1-O4 2.0192(11) Zn1-N1 2.0534(13) Zn1-O3 2.1112(11) Bond angles O1-Zn1-O3 105.92(5) O3-Zn1-O4 104.92(5) O1- Zn1-O4 90.27(5) O3-Zn1-N1 116.76(5) O1- Zn1-N1 90.71(5) O3-Zn1-O3 82.95(5) O1-Zn1-O3 168.86(5) O4-Zn1-N1 136.23 (5) N1-Zn1-O3 79.12(5) O4-Zn1-O3 93.95 (4) The asymmetric unit consists of a dimeric complex where each of the two zinc atoms is coordinated by one ligand molecule in a tridentate fashion and one DMSO molecule. One of the phenolic oxygen atom of each ligand acts as bridge between the two zinc atoms resulting in a pentacoordinated zinc (II) ions in NO4 inner. The ligand is coordinated to the metal ion via one azomethine nitrogen atom and two phenolic oxygen atoms. The dimethyl sulfoxide molecule solvent acts as unidentate via the oxygen atom. The ZnNO4 chromophores are best described as distorted trigonal bipyramids. In fact the Addison parameter [33] τ = (β - α)/60, where α and β are the largest angles around the metal center, is a structural index which is used to classified a range of environments between the perfect square planar geometry (τ = 0) and the perfect trigonal bipyramid (τ = 1). The value of τ = 0.5438 is indica- tive of a highly distorted trigonal bipyramid environment the zinc atoms. For each Zn center, the equatorial plane is occupied by two bridged phenoxo oxygen atoms and one unidentate phenoxo oxygen atom, the apical position being occupied by an azomethine nitrogen atom and an oxygen atom of a coordinated DMSO solvent molecule. The bonds lengths Zn-N is 2.0534(13) Å while the distances between the zinc atom and the phenolic oxygen atoms acting as bridges are 2.1112(11) and 2.0104(11) Å, respectively. The Zn–N distan- ces are in the order of those found for the trigonal bipyramidal complex [Zn2(HL)4](ClO4)4 (HL is (2-(-(3-(dimethylamino) propylimino)methyl)-4-bromophenol)) [34]. The Zn‒O bond lengths where the oxygen atom is the unidentate phenolate atom, [Zn‒O, 1.9679(11) Å] are shorter than those found for Zn‒O lengths where the oxygen atom acts as bridge between the two zinc ions, [Zn‒O, 2.1112(11) Å] (Table 3). These values are comparable to those found for a similar complex [35, 36]. The coordination distance to the oxygen atom of the DMSO solvent, [Zn1‒O4, 2.0192(11) Å] are comparable with the values found for the similar zinc trigonal bipyramidal complex [37]. 4. Conclusion The nuclearity of the complexes and the octahedral environment around Mn(II), Co(II), Ni(II) and Cu(II) are supported by the spectral data while the trigonal bipyramidal environment in the Zn(II) complex is demonstrated by the X- ray diffraction structure. In both complexes, the ligand acts as tridentate through one azomethine and two deprotonated phenolic oxygen atoms. The analytical data are in accordance with the proposed structures. The magnetic moments of the diamagnetic complexes are in accordance with the binuclear formulation. The zinc(II) complex differs from other reported complexes by its coordination number although the ligand acts similarly in all complexes. This difference is confirmed by the X-ray structure of the Zn(II) complex. Supplementary material CCDC-1846486 contains the supplementary crystallo- graphic data for this paper. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/, 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 Disclosure statement Conflict of interests: The authors declare that they have no conflict of interest. Author contributions: All authors contributed equally to this work. Ethical approval: All ethical guidelines have been adhered. Sample availability: Samples of the compounds are available from the author. ORCID Amadou Gueye http://orcid.org/0000-0002-3854-114X Farba Bouyagui Tamboura http://orcid.org/0000-0002-1108-0718 Jean-Marc Planeix http://orcid.org/0000-0001-7414-0119 Natalia Gruber http://orcid.org/0000-0003-4986-2931 Mohamed Gaye http://orcid.org/0000-0001-8989-1548 References [1]. Novoa, N.; Justaud, F.; Hamon, P.; Roisnel, T.; Cador, O.; Guennic, B. L.; Manzur, C.; Carrillo, D.; Hamon, J. R. Polyhedron 2015, 86, 81-88. [2]. Saha, S.; Jana, S.; Gupta, S.; Ghosh, A.; Nayek, H. P. Polyhedron 2016, 107, 183-189. [3]. Akila, E.; Usharani, M.; Ramachandran, S.; Jayaseelan, P.; Velraj, G.; Rajavel, R. Arabian J. Chem. 2017, 10, S2950-S2960. [4]. Minelli, M.; Hart-Cooper, W.; Sinnwell, J. G.; Blumberg, D. T.; Guzei, I. A.; Spencer, L. C.; Vazquez, J. P. S.; Peralta, A. S.; Torres, M. S. Polyhedron 2018, 146, 26-34. [5]. Baran, P.; Boca, R.; Breza, M.; Elias, H.; Fuess, H.; Jorik, V.; Klement, R.; Svobodae, I. Polyhedron 2002, 21, 1561-1571. [6]. Capan, A.; Urus, S.; Sonmez, M. J. Saudi Chem. Soc. 2018, 22(6), 757- 766. [7]. Samper, K. G.; Marker, S. C.; Bayon, P.; MacMillan, S. N.; Keresztes, I.; Palacios, O.; Wilson, J. J. J. Inorg. Biochem. 2017, 177, 335-343. [8]. Kavitha, P.; Saritha, M.; Reddy, K. L. Spectrochim. Acta A 2013, 102, 159-168. [9]. Ali, O. A. M.; El-Medani, S. M.; Ahmed, D. A.; Nassar, D. A. J. Mol. Struct. 2014, 1074, 713-722. [10]. Shabbir, M.; Akhter, Z.; Ashraf, A. R.; Ismail, H.; Habib, A.; Mirza, B. J. Mol. Struct. 2017, 1149, 720-726. [11]. Panja, A. Polyhedron 2012, 43, 22-30. [12]. Kose, M.; Goring, P.; Lucas, P.; Mckee, V. Inorg. Chim. Acta 2015, 435, 232-238. [13]. Ebrahimipour, S. Y.; Abaszadeh, M.; Castro, J.; Seifi, M. Polyhedron 2014, 79, 138-150. [14]. Briseno-Ortega, H.; Juarez-Guerra, L.; Rojas-Lima, S.; Mendoza- Huizar, L. H.; Vazquez-Garcia, R. A.; Farfan, N.; Arcos-Ramos, R.; Santillan, R.; Lopez-Ruiza, H. J. Mol. Struct. 2018, 1157, 119-126. [15]. Dey, S. K.; Mukherjee, A. Coord. Chem. Rev. 2016, 310, 80-115. [16]. Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;Puschmann, H. J. Appl. Cryst. 2009, 42, 339-341. [17]. Sheldrick, G. M. Acta Cryst. A 2015, 71, 3-8. [18]. Sheldrick, G. M. Acta Cryst. C 2015, 71, 3-8. 2018 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.9.4.281-286.1761 https://www.ccdc.cam.ac.uk/structures/ mailto:data_request@ccdc.cam.ac.uk http://orcid.org/0000-0002-3854-114X http://orcid.org/0000-0002-1108-0718 http://orcid.org/0000-0001-7414-0119 http://orcid.org/0000-0003-4986-2931 http://orcid.org/0000-0001-8989-1548 286 Gueye et al. / European Journal of Chemistry 9 (4) (2018) 281-286 [19]. Gao, B.; Zhang, D.; Li, Y. Opt. Mater. (Amsterdam, Neth. ) 2018, 77, 77- 86. [20]. Barfeie, H.; Grivani, G.; Eigner, V.; Dusek, M.; Khalaji, A. D. Polyhedron 2018, 146, 19-25. [21]. Sedighipoor, M.; Kianfar, A. H.; Sabzalian, M. R.; Abyar, F. Spectrochim. Acta A 2018, 198, 38-50. [22]. Egekenze, R. N.; Gultneh, Y.; Butcher, R. Inorg. Chim. Acta 2018, 478, 232-242. [23]. Yousef, T. A.; Alduaij, O. K.; Ahmed, S. F.; El-Reash, G. M. A.; El- Gammal, O. A. J. Mol. Struct. 2016, 1119, 351-364. [24]. Tserkezidou, C.; Hatzidimitriou, A. G.; Psomas, G. Polyhedron 2016, 117, 184-192. [25]. Bibi, S.; Mohamad, S.; Manan, N. S. A.; Ahmad, J.; Kamboh, M. A.; Khor, S. M.; Yamin, B. M.; Halim, S. N. A. J. Mol. Struct. 2017, 1141, 31-38. [26]. Kane, C. H.; Tinguiano, D.; Tamboura, F. B.; Thiam, I. E.; Barry, A. H.; Gaye, M.; Retailleau; P. Bull. Chem. Soc. Ethiop. 2016, 30, 101-110. [27]. Hasnan, M. M. I. M.; Abdullah, N.; Said, S. M.; Salleh, M. F. M.; Hussin, S. A. M.; Shah, N. M. Electrochim. Acta 2018, 261, 330-339. [28]. Ammar, R. A.; Alaghaz, A. N. M. A.; Zayed, M. E.; Al-Bedair, L. A. J. Mol. Struct. 2017, 1141, 368-381. [29]. Seals, W.; Arman, H.; Batha, G.; Musie, G. T. Inorg. Chim. Acta 2018, 448, 16-25. [30]. Jana, N. C.; Brandao, P.; Saha, A.; Panja, A. Polyhedron 2017, 138, 31- 36. [31]. Thompson, L. K.; Mandal, S. K.; Tandon, S. S.; Bridson, J. N.; Park, M. K. Inorg. Chem. 1996, 35, 3117-3125. [32]. Geary, W. J. Coord. Chem. Rev. 1971, 7, 81-122. [33]. Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C. J. Chem. Soc., Dalton Trans. 1984, 1349-1356. [34]. Bhattacharyya, A.; Sen, S.; Harms, K.; Chattopadhyay, S. Polyhedron 2015, 88, 156-163. [35]. Azam, M.; Al-Resayes, S. I. J. Mol. Struct. 2016, 1107, 77-81. [36]. Fliedel, C.; Rosa, V.; Alves, F. M.; Martins, A. M.; Aviles, T.; Dagorne, S. Dalton Trans. 2015, 44, 12376-12387. [37]. Parrilha, G. L.; Vieira, R. P.; Rebolledo, A. P.; Mendes, I. C.; Lima, L. M.; Barreiro, E. J.; Piro, O. E.; Castellano, E. E.; Beraldo, H. Polyhedron 2011, 30, 1891-1898. Copyright © 2018 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). 2018 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.9.4.281-286.1761 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2. Experimental 2.1. Materials and procedures 2.2. Synthesis of 2-((2-hydroxyphenylimino)methyl)-6-methoxyphenol 2.3. Synthesis of the complexes 2.4. X-ray data collection, structure determination and refinement 3. Results and discussion 3.1. Formation of [M2(L)2(Solvent)x].yH2O 3.2. Characterization 3.3. Structure determination 4. Conclusion Supplementary material Disclosure statement ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: