Experimental and theoretical investigation of a novel mononuclear copper(II) azido compound with tridentate (NNO) Schiff base

Accepted Manuscript Experimental and theoretical investigation of a novel mononuclear copper(II) azido compound with tridentate (NNO) Schiff Base Ahmet Karahan, Sedat Karabulut, Hakan Dal, Raif Kurtaran, Jerzy Leszczynski PII: DOI: Reference:

S0022-2860(15)00174-X http://dx.doi.org/10.1016/j.molstruc.2015.02.065 MOLSTR 21363

To appear in:

Journal of Molecular Structure

Received Date: Revised Date: Accepted Date:

30 October 2014 17 February 2015 18 February 2015

Please cite this article as: A. Karahan, S. Karabulut, H. Dal, R. Kurtaran, J. Leszczynski, Experimental and theoretical investigation of a novel mononuclear copper(II) azido compound with tridentate (NNO) Schiff Base, Journal of Molecular Structure (2015), doi: http://dx.doi.org/10.1016/j.molstruc.2015.02.065

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Experimental and theoretical investigation of a novel mononuclear copper(II) azido compound with tridentate (NNO) Schiff Base Ahmet Karahan1*, Sedat Karabulut2, Hakan Dal3, Raif Kurtaran4, Jerzy Leszczynski5 1

Department Of Property Protection and Safety Sütçüler Prof. Dr. Hasan Gürbüz Vocational School Süleyman Demirel University, Sütçüler, Isparta, Turkey

2

Department of Chemistry, Faculty of Arts and Sciences, Balıkesir University, Balıkesir, Turkey 3

4

Department of Chemistry, Faculty of Sciences, Anadolu University, Eskişehir, 26470, Turkey

Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, Turkey

5

Interdisciplinary Center for Nanotoxicity, Department of Chemistry and Biochemistry, Jackson State University, 1400 J. R. Lynch Street, Jackson, MS, 39217, USA.

*Corresponding Author: E-mail: [email protected] Fax: +90-246-3512901

1

Experimental and theoretical investigation of a novel mononuclear copper(II) azido compound with tridentate (NNO) Schiff Base

Ahmet Karahan1*, Sedat Karabulut2, Hakan Dal3, Raif Kurtaran4, Jerzy Leszczynski5 1

Department Of Property Protection and Safety Sütçüler Prof. Dr. Hasan Gürbüz Vocational School Süleyman Demirel University, Sütçüler, Isparta, Turkey

2

Department of Chemistry, Faculty of Arts and Sciences, Balıkesir University, Balıkesir, Turkey 3

4

Department of Chemistry, Faculty of Sciences, Anadolu University, Eskişehir, 26470, Turkey

Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, Turkey

5

Interdisciplinary Center for Nanotoxicity, Department of Chemistry and Biochemistry, Jackson State University, 1400 J. R. Lynch Street, Jackson, MS, 39217, USA.

*Corresponding Author: E-mail: [email protected] Fax: +90-246-3512901 Abstract The tridentate (NNO) Schiff base (HL), has been prepared by the condensation of 2(aminomethyl)pyridine with 5-chloro-salicylaldehyde. The mononuclear [N-(2-pyridylmethyl)-3chloro-salicylaldiminato] (azido) copper(II) complex of general formula [Cu(L)(N3)] (1) has been synthesized by the treatment of HL and CuCl2·2H2O with sodium azide. The ligand and complex have been investigated by various methods including IR, TG-DTA and X-ray diffraction techniques. The complex crystallizes in monoclinic space group P21/c, with unit cell dimensions a = 6.7369(4), b = 11.6058(8), c = 17.1379(11) Å, β = 93.823(2)o. The distorted square-planar Cu(II) ion in complex is chelated by one imino N, one phenolic O and one pyridine N atoms of Schiff base ligand and one N atom of azide ion. The electrochemical behavior of the mononuclear copper azido complex was studied with cyclic voltammetry.

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Tautomer stability of the ligand and the complex has been determined by molecular modeling techniques. It has been concluded that the HL is more stable than its tautomeric form (THL) both as ligand and complex structures.

Keywords: Tautomer, square-planar, Cu(II) complexes, thermal analysis, cyclic voltammetry, quantum chemical calculation.

1. Introduction The chemistry of metal complexes with Schiff base ligands and their applications has attracted considerable attention, mainly due to their preparative accessibility, structural variability, magnetic properties and biological properties [1-5]. Recently, there has been considerable interest in NNN, NNO, ONO donor type tridentate Schiff base ligands. In such species all three donor sites can coordinate to a metal ion [6-9]. Interestingly, in this type complexes, the coordination vacancies of metal ion are saturated by solvent and/or bridging ligand which represents pseudohalide groups, N-3, SCN-, OCN-, having a tendency to bond mononuclear complex groups via μ-bridges to form polynuclear complexes [10,11]. Also, pseudohalogens complexes with transition metal have attracted much interest due to their structures, magnetic properties and their versatile behaviors as bridging ligands in end-to-end and/or end-on fashions [12]. Although many coordination compounds of tridentate Schiff base have been studied, the researchers have been rarely reported structures of the [ML(N3)], (M=Cu, Ni, Mn; L=NNO donor atoms) type [13-15]. In this study, as a part of our ongoing research on the synthesis and structural characterization of complexes with Schiff base ligands and azide ion, the synthesis, IR spectra, thermal, electrochemical study and X-ray single crystal structural analysis of a square-planar

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mononuclear [CuLN3] complex (Scheme 1) are presented. Scheme 1 demonstrates the synthetic pathway for [CuLN3]. There is additional tautomeric form possible for HL ligand (Scheme 2), which can provide an alternative structure for copper complex. In order to compare the relative stabilities and properties, ligands (HL and THL) and their complexes (HLCu and THLCu) have been modeled by quantum chemical techniques.

2. Experimantal 2.1 Materials and measurements All reagents and solvents were purchased from Merck, Sigma-Aldrich and used without further purification. The elemental analysis for the ligands and complexes were carried out at the Eurovector 3018 CHNS analyzer. IR spectra were obtained on a Perkin–Elmer Spectrum 65 Series FT-IR spectrophotometer in the range of 4000-600 cm-1. Electronic spectra were obtained using a Double Beam UV-Vis Molecular Spectroscopy T80 Series in wavelength 190-1100 nm. Voltammetric

measurements

were

performed

using

an

IVIUM

Compactstat

potentiostat/galvanostat BASI C3 series. The analyzer was controlled with Trace Master 5 Software. Three-electrode system with a hanging mercury drop electrode (HMDE) as a working electrode, an Ag/AgCl with saturated KCl as a reference electrode, and a platinum wire as an auxiliary electrode was used. The test solutions were deoxygenated with nitrogen for 300 s. The platinum wire was polished routinely with 0.5-lm alumina polish, washed with distilled water and rinsed with acetone. Hexadistilled mercury (Radiometer, Copenhagen) was used throughout the study of HMDE. The thermogravimetry/differential thermal analysis (TG/DTA) measurements were run on a Perkin–Elmer Diamond DTA/TG. In this study, thermogravimetric curves were obtained with a flow rate of nitrogen gas of 200 mL/min and the heating rate 20 ◦

C/min with ceramic pan. Experiments were carried out in the range 30-1200 ◦C

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2.2. Synthesis of tridentate Schiff base ligand (HL) The 1:1 equimolar condensation of 2-picolylamine and 5-chlorosalicylaldehyde for 2 hours in methanolic solvent results in a yellow solution. The color indicates the formation of the Schiff base ligand (HL) which was used without further purification. Yield: 0.178 g (72%), Melting Point: 69oC, Anal. Cal. for [C13H11ClN2O]: C, 63.18; H, 4.12; N, 11.1 Found: C, 63.29; H, 4.49; N, 11.36.

Caution: Azide derivatives in presence of organic ligands are potentially explosive and should be used in small quantities.

2.3. Synthesis of [CuLN3] The slow addition of 30 mL of yellow methanolic solution of the tridentate Schiff base ligand (HL) (0.246 g, 1 mmol) to 20 mL of methanolic solution of CuCl2 (0.134 g, 1 mmol) resulted in a green solution. This solution was stirred for 20 min at 65 0C and then followed by addition of 5 mL aqueous solution of NaN3 (0.260 g, 4 mmol) resulting in a color change from green to dark green solution. The dark green solution was then filtered and kept at room temperature for five days. Dark green crystals were collected by filtration and dried in open air. Yield: 0.270 g (77%), Anal. Cal. for [C13H10ClCuN2O]: C, 44.12; H, 2.96; N, 19.13, Found: C, 44.45; H, 2.87; N, 19.94.

2.4. Crystal structure determination Diffraction measurement was made on a Bruker Apex Kappa CCD diffractometer using graphite monochromated Mo-K radiation (λ = 0.71073 Å) at 100 K. Absorption correction by multi-scan [16] was applied. The intensity data were integrated using the APEXII program [17]. Absorption

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corrections were applied based on equivalent reflections using SADABS [18]. The structures were solved by direct methods and refined using full-matrix least-squares against F2 using SHELXL [19]. All non-hydrogen atoms were assigned anisotropic displacement parameters and refined without positional constraints. Hydrogen atoms were included in idealized 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 details of data collection, refinement and crystallographic data are summarized in Table 2.

2.5. Calculation Details Gaussian 09 and Gaussview 5.0 [20] software packages were used for calculations and modeling the considered molecules. Input files of copper complexes (HLCu and THLCu) were prepared based on experimental X-ray structure. Though, the experimental data includes the unit cell linkages, however due to high computational expenses of the optimization of a complete crystal packing, the structures have been modeled as monomers. Molecular structures of ligands (HL and THL) were optimized at the B3LYP/6-311G++(2d, 2p) [21] level. The complexes (HLCu and THLCu) were optimized at B3LYP/GENECP level and lanl2dz basis set was chosen for Cu and 6-31+G(d,p) for the rest of the molecules. Vibrational frequency calculations have been performed after optimization and no imaginary frequencies were identified . All calculations have been performed in the gas phase.

3. Results and discussion 3.1. Spectral properties 3.1.1. FTIR Spectra The IR spectrum of the free ligand was compared with the spectra of the [CuLN3] in the region 4000-600 cm-1 (Fig. 1). The relevance of the IR spectrum of the title complex lies mainly in the

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as and  bands due to the presence of N-3 ion. This is revealed by bands around 2051 cm-1 and 653 cm-1, respectively. The characteristic bands of azide ion in mononuclear azido complexes are similar to the literature values [22, 23]. The IR spectrum of free ligand shows significant bands at 1632 cm-1 for C=N stretching vibration, at 3250-3350 cm-1 for phenolic O–H stretching (a very broad band possibly because of the hydrogen bonds), and at 1274 cm-1 for phenolic C-O linkage. Azomethine C=N stretching frequency of the mononuclear azido complex (CuLN3) appears as a single and more intense than ligand form at 1632 cm-1 because of complexation, which indicates donation of the lone pair of electrons on azomethine nitrogen to copper center. For free ligand the (C=C) and (C=N) stretching bands appears at (1473 and 1434 cm-1). Same frequencies of Cu complex (C=C and C=N) are assigned at 1454 and 1411 cm-1 for pyridine ring, respectively (Table 1) indicating the coordination of the heterocyclic N-atoms to the copper ion.

3.1.2. Absorption spectra The absorption spectra of the ligand and complex [CuLN3] were recorded in dimethylformamide (DMF). The UV spectra for the ligand shows only an absorption band in the region of 266 nm assigned to electronic transition For the complex, a band occurs near 266 nm (11150 M-1 cm-1) assigned to intra-ligand charge transfer transitions. The bands at 337 and 367 nm may be assigned to d-d transitions, indicating a square planar geometry [24, 25].

3.2. Electrochemical studies CV experiments were carried out using a conventional three-electrode cell containing a glassy carbon electrode (0.1 cm2) as the working electrode. Prior to the measurements, the electrode was cleaned and polished with 0.05 micron alumina, wiped, washed with distilled water, and rinsed with ethanol. The counter electrode was a platinum wire. The reference electrode was an Ag/AgCl electrode with saturated aqueous AgCl solution isolated from the cell via a Huber-

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Lugin capillary tube. The test solutions were deoxygenated with argon for 30 minutes. All measurements were carried out at room temperature and on a VoltaLab 40 system connected to a PC with the VoltaLab 4.0 electrochemical software. The supporting electrolyte used 0.1 M NaClO4.

The electrochemical characteristics of the ligand, the copper complex and copper salt were examined by means of cyclic voltammetry in DMF. A typical cyclic voltammogram of the ligand exhibited an irreversible anodic peak at 0.45 probably as the result of oxidative process (Fig.2). The metal salt on the other hand tends to give two peaks; one at 0.65 corresponding to the anodic oxidation of the copper ion and one at 0.35 volts, corresponding to the reduction of the oxidized species (Fig.3). The oxidation peak could only be obtained after the first cycle meaning that only Cu(I) and Cu(II) species are present in the matrix. The copper complex on the other hand reveals an anodic peak at 0.85 V and a cathodic peak at -0.18 V. It appears that complex formation both hinders the oxidation behavior of the ligand and the copper oxidation potential shifts to higher potentials, as well as the reduction reaction, which shifts to more negative values (Fig.4). Each process is a one electron transfer process. Further metal complexes of the ligand are in preparation as it shows promise, especially in heavy metal technology.

3.3. Thermal analysis HL and its copper (II) complex were studied by thermo gravimetric analysis from 30 °C to 1200 °C in nitrogen atmosphere. DTA/TG curves of HL ligand and [CuLN3] complex are shown in Figures 5 and 6, respectively. The TG curves reveal that the ligand is stable up to 80 °C. On the other hand, complex is more stable than free ligand (up to 172 °C). The remained residue for the HL should be the carbon. The melting point was not observed in complex, indicating that melting has been overlapped by the decomposition of the compounds. In TG curve of [CuLN3]

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complex (Fig. 6) two thermal reactions can be seen. The first thermal reaction in the range of 172-214°C with a fast mass loss corresponds to total mass of azide groups in complex structure (observed loss 12.3%, theoretical loss 11.9%). In the DTA curve, there is an exothermic peak at 197 °C corresponding to this event. In the second thermal reaction with an endothermic peak at 1080 °C, the remaining parts of the complexes decomposed between 214-1200 °C. The residue remained about 1200 °C should be CuO.

3.4. Description of the crystal structure An ORTEP drawing of mononuclear [CuLN3] complex is presented in Figure 2, where the numbering scheme adopted for the respective atoms is also given. The crystal data and structure refinement details for complex 1 are listed in Table 2. Selected bond lengths and angles are listed in Table 3. The complex crystallizes in monoclinic space group P21/c, with unit cell dimensions a = 6.7369(4), b = 11.6058(8), c = 17.1379(11) Å, β = 98.712(4)o, Z=4. The central copper atom, which is located on the inversion centre, has a distorted square-planar coordination geometry with three donor sets, one pyridine N, one azomethine N, one deprotonated phenolic oxygen of ligand together with an azide ion nitrogen. The bond lengths of Cu1-O1, Cu1-N1, Cu1-N2, Cu1N3 are 1.903(2), 1.999(3), 1.937(3), and 1.951(3) Å, respectively. The copper-azide ion (Cu1N3) bond lengths also is in agreement with the results reported by others [26,27]. The terminal coordinated azido anion is nearly linear [N3-N4-N5= 175.9(4) o].

3.5. Computational Results According to the calculated relative energies (zero point energy corrected) the HL ligand is 8 kcal/mol more stable than tautomeric form THL. There should be a high kinetic barrier for HLTHL transformation and the calculated energy difference is another reason for the nonexistence of THL. The energy difference increases to 12.75 kcal/mol for complexes that include both tautomers. These results are compatible with crystallographic data. The molecular driving forces 9

are stabilizing the free ligand (HL) and the complex (HLCu) more than tautomeric forms (THL and THLCu). One can conclude that the internal molecular driving forces are effective on stabilizing molecular structure of HLCu. The HLCu is more stable than THLCu even in monomeric form. The crystal packing effect further stabilizes this form, as evident from experimental studies. The electrostatic potential maps of free ligands and complexes have been generated (Scheme 3). The ESP map of complex (HLCu) clearly show that the attached Cl is one of the most electronegative fragments, and the azide, which is attached the copper, is the one of the most electropositive part of the structure. As it can be understood from the experimental X-Ray results the unit cells are attached to each other by the Cl----N3 intermolecular connection (Scheme 4). This preference is supported by the ESP map results. Negatively charged Cl atom donates electrons to the positively charged N3 group. According to the experimental crystallographic data the position of azide group (Cu–N=N=N) represents gauche arrangement (Dihedral angle for O1Cu1N3N4= -64.71) relatively to the whole molecule plane (Figue 7 and 8). This might be a result of crystal packing effects because the calculation results suggests for the azide group to be located

at the same plane as the rest of

molecule molecule (Dihedral angle for O1Cu1N3N4= 0.05). The imino group (-C=N-) is attached to the aromatic ring, which in HL ligand is also substituted with chlorine and oxygen. Both of these substituents (Cl and O) are mesomerically electron donating groups so the benzene ring attached to Cl and O is relatively more electronegative than the pyridine ring. Attached imino group withdraws electrons mesomerically from the benzene ring in HLCu and decreases the electron density. The other tautomeric complex (THLCu) has no attached imino group to the benzene ring so all attached groups (Cl and O) donate electrons to the benzene ring. The electrons of benzene ring, which because of the electron donating groups

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represents the most electron dense region of the structure are more delocalized than the electrons of the pyridine ring. This may be another factor which stabilizes the HLCu complex. Optimized geometries of free ligands and complexes were summarized in Scheme 3.The stretching absorption bands for azido group (–N=N=N) and imino group (-C=N-) of HLCu have been detected at 2053 cm-1 and 1634 cm-1 respectively at solid state with FTIR spectrofotometer. The same absorption bands have been calculated as 2148 cm-1 and 1673 cm-1.

4. Conclusion In this paper, NNO type tridentate Schiff base ligand and its mononuclear distorted square-planar CuLN3 Cu(II) complex with azide ion have been synthesized and characterized by physicochemical techniques. Pseudohalide ligand, azide ion, can coordinate to the central atom as a terminal or a bridging ligand. The complex considered in this study is coordinated by terminal ligand which neutralizes the charges of the copper (II) complex. Also, electrochemical study of the ligand and its copper complex was carried out. The tautomer stability of the free ligand and the complex has been studied by quantum chemical methods. It has been concluded that the HL tautomer is more stable than the THL form for both ligand and complex structures, as it has been identified by experimental X-Ray diffractometry . Various molecular factors favor the HL structure for free ligand as well as complex. Crystal packing governs the position of azido group (dihedral angle of O1Cu1N3N4).

Supplementary Data Crystallographic data for the structure (2) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre (The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK; e-mail: [email protected]; www: http://www.ccdc.cam.ac.uk; fax: +44(0)1223-336033) and are available free of charge on request, quoting the deposition number CCDC-927053.

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Acknowledgements The financial support of Scientific Research Council of Balikesir University (Project No.2010/30) is gratefully acknowledged. REFERENCES 1. O. Atakol, R. Bõca, I. Ercan, F. Ercan, H. Fuess, W. Haase, R. Herchel, Chemical Physics Letters 423 (2006) 192. 2. W.Liu, Y. Zou, C. Ni, Y. Li, Q. Meng, J. Mol. Structure 751 (2005) 1. 3. R. Tao, C. Mei, S. Zang, Q. Wang, J. Niu, D. Liao, Inorg. Chim. Acta 357 (2004) 1985 4. N. Dharmaraj, P. Viswanathamurthi, K.Natarajan, Transition Metal Chemistry 26 (2001) 105. 5. S. Oz, R. Kurtaran, C. Arici, U. Ergun, F. N. D. Kaya, K. C. Emregul, O. Atakol, D. Ulku, Journal Of Thermal Analysis And Calorimetry 99 (2010) 363. 6. P. R. Reddy, A. Shilpa, Chemistry and Biodiversity 9 (2012) 2262. 7. S. F. Lou, X. Zheng, X.-Y. Qiu, J. Structural Chemistry 52 (2011) 1127-1130. 8. S. Naiya, S. Biswas, M. G. B. Drew, A. Ghosh, Polyhedron 34 (2012) 67. 9. A. R. Stefankiewicz, M. Wałęsa-Chorab, H. B. Szcześniak, V. Patroniak, M. Kubicki, Z. Hnatejko, J. Harrowfield, Polyhedron 29 (2010) 178. 10. R. Kurtaran, K. C. Emregul, C. Arici, F. Ercan, V. J. Catalano, O. Atakol, Synthesis And Reactivity In Inorganic And Metal-Organic Chemistry 33 (2003) 281. 11. L. T. Yildirim, R. Kurtaran, H. Namli, A. D. Azaz, O. Atakol, Polyhedron 26 (2003). 4187. 12. S. Oz, M. Kunduraci, R. Kurtaran, U. Ergun, C. Arici, M. A. Akay, O. Atakol, K. C Emregul, D. Ulku, Journal Of Thermal Analysıs And Calorımetry 101 (2010) 221.

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13. S. Naiya, C. Biswas, M. G. B. Drew, C. J. Gomez-Garcia, J. M. Clemente-Juan, A. Ghosh, Inorg. Chem. 49 (2010) 6616–6627. 14. R. Biswas, S. Mukherjee, P. Kar, and A. Ghosh, Inorg. Chem. 51 (2012) 8150−8160. 15. C. Adhıkaryy, D. Maly, S. Chaudhurız, S. Koner, Journal of Coordination Chemistry 59 (2006) 699–704. 16. Bruker, SADABS, Bruker AXS Inc., Madison; (2005). 17. Bruker-AXS SAINT V7. 60A. 18. G. M. Sheldrick, SADABS V2008/1, University of Göttingen, Germany. 19. G. M. Sheldrick, A short history of SHELX Acta Crystallogr. Sect. A: Found. Crystallogr. A64 (2008) 112. 20. M.J. Frisch et al., Gaussian 09, Revision C.01 2010. 21. C. Lee, W. Yang, R.G. Parr, Phys. Rev. 37 (1988) 785. 22. S. Öz, I. Svoboda, R. Kurtaran, M. Aksu, M. Sari, M. Kunduraci, and O. Atakol, Z. Anorg. Allg. Chem. 637 ( 2011) 257–262. 23. R. Kurtaran, C. Arici, S. Durmus, D. Ülkü, O. Atakol, Analytical Sciences 19 (2003) 335-336. 24. Datta, A.; Struct Chem. 39 (2009) 619-622. 25. . Basak, S. Sen, S. Mitra, C. Marschner, W.S Sheldrick, Struct Chem. 19 (2008) 115-121. 26. X.Y. Qiu, W.S. Liu, H.L. Zhu, Z. Anorg. Allg. Chem. 633 (2007) 1480-1484. 27. H. Wang, Y. Lang, S. Wang, Acta Crystallographica Section E E68 (2012) 540.

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Figure captions Scheme 1. Synthetic pathway for ligand and complex. Scheme 2: Tautomeric equilibria of HL and THL Scheme 3: ESP maps of free ligands (HL and THL) and complexes (HLCU and THLCu), Isovalue:0.0004. Scheme 4: Unit cell connection

Figure 1. Overlaid and splitted FTIR spectra of ligand and Cu complex. Figure 2. Cyclic voltammogram of the HL Figure 3. Cyclic voltammogram of the CuCl2 Figure 4. Cyclic voltammogram of the [CuLN3] Figure 5. TG/DTA curves of the LH. Figure 6. TG/DTA curves of the [CuL(N3)] Figure 7. Ortep drawing of CuLN3 with thermal ellipsoids drawn at 50% probability. Figure 8. A two-dimensional network structure in the ac-plane of the complex. Table 1. Assignments of selected ligand and Cu complex frequencies Table 2. Crystal data and structure refinement of complex. Table 3. Bond lengths [Å] and angles [o] in the metal coordination spheres of complex.

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Scheme 1

Scheme 2:

15

Scheme 3:

HL

THL

HLCu

THLCu

16

Scheme 4:

17

Fig. 1. Overlaid and splitted FTIR spectra of ligand and Cu complex.

18

Fig. 2. Cyclic voltammogram of the HL

Fig 3. Cyclic voltammogram of the CuCl2

19

Fig. 4. Cyclic voltammogram of the [CuLN3]

20

Fig. 5. TG/DTA curves of the HL

Fig. 6. TG/DTA curves of the [CuLN3]

Fig. 7. Ortep drawing of [CuLN3] with thermal ellipsoids drawn at 50% probability.

21

Fig. 8. A two-dimensional network structure in the ac-plane of the complex.

22

TABLE 1. Assignments of selected ligand and Cu complex frequencies

Ligand Frequency Assignment 3058.7 Aromatic C-H stretching 1632.6 C=N stretching 1474.2 Aromatic C=C 1274.6 Phenolic -CO stretching

23

Cu Complex Frequency Assignment 3059.6 Aromatic C-H stretching 2051.8 -N3 stretching 1632.6 1454.3

C=N stretching Aromatic C=C

TABLE 2. Crystal data and structure refinement of complex Empirical formula

C13H10 N5OClCu

CCDC No

927053

Formula weight

351.25

Crystal system

Monoclinic

Space group

P21/c

a (Å)

6.7369(4)

b (Å)

11.6058(8)

c (Å)

17.1379(11)

β (o)

98.712(4)

V (Å)3

1324.50(15)

Z

4 –3

Dcalcd. (Mg.m )

1.761

F(000)

708

μ (mm–1)

1.86



Mo-K 0.71073

T(K)

100

Rint

0.040

h, k, l (o)

-8/8, -11/15, -22/21

θmin-θmax(o)

2.1 - 28.4

Reflection with (I > 2σ (I))

2440

Measured reflections

11780

Independent reflections

3264

R ; R (I >2σ (I))

R1= 0.038 ; wR2= 0.097

S

1.11

Δρmin., Δρmax.(e Å3)

-0.69, 0.41

Crystal colour

Dark green

24

TABLE 3. Bond lengths [Å] and angles [o] in the metal coordination spheres of complex Cu1-O1

1.903(2)

N3-N4

1.185(4)

Cu1-N1

1.999(3)

N2-C7

1.282(4)

Cu1-N2

1.937(3)

N2-C8

1.463(4)

Cu1-N3

1.951(3)

C4-Cl1

1.746 (3)

O1-Cu1-N1

175.60(10)

C1- O1-Cu1

127.3(2)

O1-Cu1-N3

90.60(11)

C7-N2-Cu1

126.8(2)

O1-Cu1-N2

93.08(10)

C8 -N2-Cu1

115.8(2)

N1-Cu1-N3

93.77(12)

C7-N2-C8

117.4(3)

N1-Cu1-N2

82.58(11)

C13-N1-Cu1

125.8(2)

N2-Cu1-N3

175.65(12)

C9-N1-Cu1

115.2(2)

N3-N4-N5

175.9(4)

25

Graphical abstract

26

   

Highlights A square-planar mononuclear copper(II) complex has been identified by single crystal XRay diffractometer. The ligand and complex have been characterized by various methods including FT-IR, TG-DTA and CV. Tautomeric forms of ligand and complex were optimized at DFT level of theory. Tautomeric preferences of both ligand and complex were discussed.

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