Synthesis, characterization, crystal structure, magnetic studies of a novel polymeric zig-zag chain copper (II) complex

Inorganica Chimica Acta 413 (2014) 55–59

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Synthesis, characterization, crystal structure, magnetic studies of a novel polymeric zig-zag chain copper (II) complex Alper Yardan a,⇑, Yasemin Yahsi b, Hulya Kara b, Ahmet Karahan a, Sefa Durmus c, Raif Kurtaran d a

Balikesir University, Faculty of Art and Science, Department of Chemistry, TR-10145 Balikesir, Turkey Balikesir University, Faculty of Art and Science, Department of Physics, TR-10145 Balikesir, Turkey c Duzce University, Faculty of Science and Letter, Department of Chemistry, TR-81620 Duzce, Turkey d Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, Turkey b

a r t i c l e

i n f o

Article history: Received 11 September 2013 Received in revised form 24 December 2013 Accepted 3 January 2014 Available online 17 January 2014 Keywords: Schiff bases Copper (II) complex Thermal analysis Single crystal X-ray Magnetic behavior

a b s t r a c t A single crystal of copper (II) complex (1) has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis and characterized by elemental analyses, IR spectroscopy, thermal analysis, 1H NMR and 13C NMR spectroscopy. The complex crystallizes in orthorombic space group Pnma, with unit cell dimensions a = 9.8944, b = 25.2972, c = 7.4457 Å, b = 90°. Structural analysis of (1) shows that the Schiff base ligand coordinates toward one metal atom in a pentadentate mode and each Cu atom is six-coordinated. The aliphatic oxygen atom of Schiff base ligand links the [CuL] moieties and creates polymeric zig-zag chain structure. In addition, magnetic susceptibilities for complex (1) have been measured over the temperature range 2–300 K and the magnetic parameters have been determined with fitting procedure. Magnetic measurements on (1) reveal the presence of antiferromagnetic exchange interactions between Cu(II) ions in the dimeric unit via bridging oxygen atoms of pentadentate Schiff base ligand. Ó 2014 Elsevier B.V. All rights reserved.

1. Introduction Transition metal–Schiff base complexes have been the subject of growing great interest due to their potential application in different fields of biological activities, molecular magnetic materials and metallosupramolecular chemistry [1–2]. In recent years, much effort has been devoted to the design and synthesis polymeric coordination structures. Such polymeric complexes are formed a discrete number of assembled molecular subunits owing to their metal coordinations, hydrogen bonds and p–p stacking interactions [3–5]. In addition, electrostatic interactions and van der Waals forces play important roles in coordination polymer and supramolecular complex. Schiff base ligands with nitrogen and oxygen donor atoms creates stable coordination and easy to make hydrogen bonds. Therefore these ligands are highly capable of building polymeric coordination structures. Recently our research group and others have reported the structural and magnetic characterization of mono- and binuclear copper (II) complexes [6–7]. It is interesting to note that although some structural and magnetic analyses of oxygen bridge Cu(II) complexes have been reported [8], to the best of our knowledge, complex (1) represents the rare example of two-dimensional Cu(II) complex containing both oxygen and hydrogen-bonds [9]. ⇑ Corresponding author. Tel.: +90 266 6121000; fax: +90 266 6121215. E-mail address: [email protected] (A. Yardan). 0020-1693/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ica.2014.01.006

In this study, we obtained a complex C19H22CuN2O6, since the aliphatic oxygen atom in it may act as bridging ligands coordinating to a second metal atom, which a novel copper (II) complex with an infinite chain structure appeared. In view of the importance of copper (II) compounds and our interest in the chemistry of coordination compounds involving chelating Schiff bases, we report here the synthesis, spectral and thermal studies, magnetic properties and single crystal X-ray diffraction analysis of the chain complex (1). 2. Experimental 2.1. Materials and physical measurements 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 by standard methods with a Eurovector 3018 CHNS analyzer. Melting points were measured using a Gallenkamp melting point apparatus. IR spectra was recorded on a Perkin–Elmer 1600 series automatic recording FT-IR spectrophotometer with the KBr disk technique in the range of 400–4000 cm1. 1H NMR and 13C NMR analysis were performed with a Bruker 400 MHz Superconducting Ultrashield liquid NMR spectroscopy. The thermogravimetry/ differential thermal analysis (TG/DTA) measurements were run on a Perkin Elmer Diamond DTA/TG thermal analyzer. In this study,

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A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59

thermogravimetric curves were obtained with a flow rate of the carrier gas of 200 mL/min and a heating rate of 20 °C/min in nitrogen (3 bar) with ceramic crucibles. Magnetization of a sample powder of (1) was measured between 2 and 300 K with an applied magnetic field H = 1 T using a Cryogenic S600 SQUID magnetometer. The effective magnetic moments were calculated by the equation leff = 2.828(vmT)1/2 [10], where vm, the molar magnetic susceptibility, was set equal to Mm/H. 2.2. Synthesis of H3L ligand A solution of 4-methoxy salicylaldehyde (0.304 g, 2 mmol) in 25 mL ethanol was added dropwise to a solution of 2-hydroxy1,3-diaminopropane (0.090 g,1 mmol) in 25 mL ethanol. The mixture was stirred for 10 min at 70 °C and then filtered and allowed to stand at room temperature for two days. Thin yellow crystals [N,N0 -bis(4-methoxy-salyciliden)-2-hydroxy-1,3-diamino propane] were obtained from the filtrate and dried in open air. Yield: 78% m.p = 154 °C. Anal. Calc. for C19H22N2O5: C, 63.67; H, 6.19; N, 7.82. Found: C, 63.37; H, 6.02; N, 7.94%. 2.3. Synthesis of complex (1) [CuL]

Table 1 Crystal data and structure refinement for (1). Empirical formula Formula weight (g mol1) Temperature (K) Crystal system Space group Unit cell dimensions a = 9.8944(5) Å b = 25.2972(14) Å c = 7.4457(4) Å a = 90° b = 90° c = 90° Volume (Å3) Z Density (calculated) (g cm3) Absorption coefficient (mm1) h range for data collection (°) Index ranges Reflections collected Independent reflections Data/restraints/parameters Goodness-of-fit on F2 R indices [I > 2r(I)] Largest difference in peak and hole (e Å3)

C19H22CuN2O6 437.93 293(2) orthorhombic Pnma

1863.66(17) 4 1.561 1.212 3.78–26.28 11 6 h 6 5, 30 6 k 6 25, 9 6 l 6 5 4454 1614 1018/1/138 0.934 R1 = 0.0418, wR2 = 0.0862 0.290 and 0.280

Equivalent amounts of triethylamine (Et3N) was added dropwise to deprotonate the phenolic OH group of the solution Schiff base ligand (1 mmol, 0.358 g) in 20 mL DMSO. To a solution of CuCl2 (1 mmol, 0.134 g) in ethanol was added to the resulting solution and it was stirred at boiling point under air atmosphere. The mixture was filtered and then allowed to stand at room temperature for three days. Dark-green crystals of complex (1) were collected by filtration and dried in air atmosphere. Yield: 67%. Anal. Calc. for C19H22CuN2O6: C, 52.11; H, 5.06; N, 6.40. Found: C, 51.83; H, 5.14; N, 6.26%. 2.4. X-ray structure determination Intensity data for suitable single crystals of (1) was collected using Oxford Diffraction Xcalibur-3 single crystal diffractometer 0 equipped with a Mo Ka radiation source (k = 0.71073 Å A at 296 K). The data collections and data reductions were performed with the CRYSALIS CCD and CRYSALIS RED programs [11]. The structure was solved by direct methods and refined using full-matrix leastsquares against F2 using SHELXTL [12]. 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 Ueq of their attached carbon atoms for methyl hydrogens, and 1.2 times the Ueq of their attached carbon atoms for all others. The crystallographic data for complex (1) is listed briefly in Table 1. Molecular drawings were obtained using MERCURY [13]. The crystal structure of (1) is shown in Fig. 1. Some selected bond lengths and angles and also hydrogen bond geometry for complex (1) are listed in Tables 2 and 3, respectively. 3. Results and discussion 3.1. IR spectra The IR spectra of H3L and its complex give information about the metal-ligand bonding. Thus, the IR spectrum of the free ligand (H3L) was compared with the complex spectra. The ligand shows a strong band at 1645 cm1 due to the presence of characteristic m(C@N) peaks. Other important peaks, phenolic m(O–H), phenolic m(C–O), aliphatic m(C–H) were appeared at 3438, 1221,

Fig. 1. The molecular structure of (1).

2891 cm1, respectively. These values are consistent with the literature data [14]. The complex exhibits m(C@N) band in the 1620 cm1 showing shift to lower wave numbers indicating the coordination of the azomethine nitrogen to the copper (II) ion [15,16]. 3.2. 1H NMR and

13

C NMR spectra

The changes of the 1H NMR and 13C NMR spectra of complexes were compared with the free ligand. The 1H NMR spectra of the ligand have a peak at 8.4 ppm assigned to azomethine proton. This

A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59 Table 2 Some selected bond lengths [Å] and angles [°] for (1). Bond lengths [Å] Cu1–N1 Cu1–O2 Cu1–O1ii Cu1–O4iii

1.983(3) 1.938(2) 2.593(4) 2.750(5)

Bond angles [°] O2–Cu1–N1 O2–Cu1–O2i N1–Cu1–N1i O2–Cu1–N1i O1ii–Cu1–O4iii O1ii–Cu1–O2 O1ii–Cu1–N1 O2–Cu1–O4iii O4iii–Cu1–N1

90.41(12) 83.52(10) 95.61(13) 173.75(12) 169.79(13) 95.56(9) 83.48(11) 92.04(9) 89.68(11)

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

Table 3 Hydrogen bond geometry for complex (1). D–HA

D–H

HA

DA

D–HA

O1–H1AO4iii O4–H4AO2iv

0.8200 0.7600

2.0300 2.2000

2.8300 2.8679

164.00 146.00

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Cu–O2 = 1.938 Å and the CuO(water) bond length is 2.750 Å, so the compound could be described as having a weakly coordinating water molecule [20]. The deviation of Cu(II) ions from N2O2 coordi0 nation plane [O2N1N1iO2i] is 0.027 Å A. These results are close to the values found in similar salen-type compounds [17,18,21]. However, the structure of (1) consist of an polymeric zigzag chain along the crystallographic a axis of [CuL] repeating units (Fig. 2), each involving one pentadentate ligand that acts as a bridge between two symmetry equivalent Cu(II) ions. The aliphatic oxygen in axial positions link the [CuL] moieties to each other by completing the distorted octahedral geometry of the Cu(II) ions from a neighboring mononuclear fragment and each copper atom is six-coordinated. The crystal packing of Cu(II) complex (Fig. 2) shows that the aliphatic oxygen atom bridges monomeric units with the CuO(bridge) bond length of 2.593 Å and the intra-chain CuCu distance is 6.480 Å. The Schiff base ligand links adjacent copper centers which leads to the polymeric zig-zag chain structure. However, the polymeric zigzag chain structure is formed in 2D networks with hydrogen bonds and the closest non-bonding CuCu distance is 5.925 Å (Fig. 3). This polymeric networks lie in the bc-axis and stacks orthogonally to the a-axis.

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

peak is shifted to the downfield (7.9 ppm) in the complex, suggesting the coordination of azomethine. The phenolic hydroxy proton appeared at 13.9 ppm in the ligand disappeared in the complex, suggesting deprotonation. In 13C NMR spectrums, imine signals (166 ppm) are shifted to lower field (170 ppm) after complexation which means that the shifts are due to coordination of the ligand to metal atom by the azomethine nitrogen. These conditions prove that the complex is formed and consistent with the XRD data and literature [17]. 3.3. DTA–TG curves In order to examine the thermal stability of the complex, thermal gravimetric (TG) and differential thermal analysis (DTA) were carried out between 25 and 1200 °C under nitrogen atmosphere. Endothermic peaks at 154 °C in DTA curve are showing that the melting of the ligand, because there is not seen any weight loss in the TG curve at this temperature [18]. The ligand is committed up to 195 °C. There is no melting point at thermal curves of the complex. TG–DTA curves indicate that complex 1 is not decomposed up to 102 °C and then the gradual decomposition occurs within the temperature range 102–1200 °C with endothermic effects. The first weight loss between 102 and 220 °C is associated with the release of water molecules (observed 4.78%; calc. 4.12%) [19]. Mass losses of the ligand and the complex (1) are demonstrating similarity in this temperature range. Probably, the final residue was found to be CuO at 1200 °C. 3.4. Crystal structure description of (1) The result of the X-ray structure analysis of complex (1) shows that the monomeric complex lies on a crystallographic mirror plane with the Cu(II) ion coordinated by two imine N atoms and two phenolate O atoms of a pentadentate Schiff base ligand and one O atom from a water ligand. In complex (1) the equatorial sites around copper atom are occupied by the N2O2 donor atoms of the ligand, with average bond distances of Cu–N1 = 1.983 Å and

Fig. 2. The polymeric zig-zag chain of (1). A two-dimensional structure formed by hydrogen bonds in the ac-plane of (1).

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Fig. 3. 2D polymeric networks of (1) lie in the bc-axis and stacks orthogonally to the a-axis.

3.5. Magnetic properties The variable temperature magnetic susceptibilities for (1) were measured at 1 T in the temperature range 2–300 K. The magnetic behaviors of complex (1) are depicted in Fig. 4 in the form of v and 1/v being the molar magnetic susceptibility and reciprocal molar magnetic susceptibility per Cu2+ ion. The plot of 1/v versus T is almost linear down to very low temperature, which shows that magnetic susceptibility data of complex (1) obey the Curie–Weiss equation [v = C/(T  h)] and gives Curie 600

0,20

-1

3

400

0,10

200

0,05

-3

300

1/χ (cm mol)

χ (cm mol )

500 0,15

constant C = 0.49 cm3 K mol1 and Weiss constant h = 2.76 K. This definitely indicates that adjacent magnetic spins are coupled antiferromagnetically. The experimental v value decreases sharply in the range of 2–10 K for (1) and then decreases monotonically up to 300 K. As seen in Fig. 4, the increase of magnetic susceptibility (v), below 10 K is due to the proportion, q, of a paramagnetic, uncoupled, Cu(II) impurity. For complex (1), the effective magnetic moment (leff) decreases gradually with the decrease of temperature indicating antiferromagnetic interaction between the two metal ions. The experimental leff value for complex (1) at room temperature is approximately 1.97 lB per Cu2+ which is close to the spin-only value of 1.92 lB, and for lower temperature the magnetic moments decrease to attain a value of 1.88 lB at 2 K. These results indicate the presence of an antiferromagnetic exchange interaction between Cu(II) ions in the dimeric unit via bridging oxygen atoms of pentadentate Schiff base ligand (Scheme 1). 4. Conclusion

100 0,00 0

50

100

150

200

250

300

0

T (K) Fig. 4. Temperature variation of the magnetic susceptibilities of (1) as v[j] and 1/v[d] vs. T plots.

A single crystal of copper (II) complex (1) has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis, elemental analyses, IR spectroscopy, thermal analysis, 1H NMR and 13C NMR spectroscopy. The aliphatic oxygen atoms of Schiff base ligand link the [CuL] moieties to each other and created the polymeric structure. The polymeric zigzag chain structure is formed in 2D networks with hydrogen bonds. Magnetic studies showed the presence of an antiferromagnetic exchange interaction between Cu(II) ions in the dimeric unit via bridging oxygen atoms of pentadentate Schiff base ligand. Acknowledgements

Scheme 1. Scheme of complex (1).

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. And Yasemin Yahsi is also grateful to Dr. Lorenzo Sorace, Dr. Andrea Caneschi and Laboratory of

A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59

Molecular Magnetism (Department of Chemistry, University of Florence) for the use of Cryogenic S600 SQUID magnetometer and Xcalibur-3 diffractometer and helpful suggestions. Appendix A. Supplementary material CCDC 759822 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/ data_request/cif. References [1] (a) E. Gungor, H. Kara, Inorg. Chim. Acta 384 (2012) 137; (b) E. Gungor, H. Kara, Spectrochim. Acta, Part A 82 (2011) 217; (c) Y. Yahsi, H. Kara, L. Sorace, O. Buyukgungor, Inorg. Chim. Acta 366 (2011) 191; (d) C. Hopa, R. Kurtaran, M. Alkan, H. Kara, R. Hughes, Transition Met. Chem. 35 (2010) 1013; (e) R. Kurtaran, S. Odabasioglu, A. Azizoglu, H. Kara, O. Sevi, O. Atakol, Cent. Eur. J. Chem. 7 (2009) 402; (f) H. Kara, Z. Naturforsch. 63b (2008) 6; (g) K.R. Surati, B.T. Thaker, Spectrochim. Acta, Part A 75 (2010) 235; (h) K.R. Surati, B.T. Thaker, J. Coord. Chem. 59 (2006) 1191; (i) M. Nasr-Esfahani, M. Moghadam, G. Valipour, Synth. Commun. 39 (2009) 3867; (j) Y. Yahsi, Inorg. Chim. Acta 397 (2013) 110; (k) S. Celen, E. Gungor, H. Kara, A.D. Azaz, J. Coord. Chem. (2013) 3170. [2] (a) M. Dey, C.P. Rao, P.K. Saarenketo, K. Rissanen, E. Kolehmainen, P. Guionneau, Polyhedron 22 (2003) 3515; (b) M. Amirnasr, K.J. Schenk, A. Gorji, R. Vafazadef, Polyhedron 20 (2001) 695; (c) S.-L. Ma, X.-X. Sun, S. Gao, C.-M. Qi, H.-B. Huang, W.-X. Zhu, Eur. J. Inorg. Chem. 6 (2007) 846; (d) M. Dey, C.P. Rao, P.K. Saarenketo, Inorg. Chem. Commun. 5 (2002) 924; (e) L.R. Nassimbeni, G.C. Percy, A.L. Rodgers, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem. 32 (1976) 1252; (f) S.S.E. Ghodsinia, B. Akhlaghinia, E. Safaei, J. Braz. Chem. Soc. 24 (2013) 895; (g) S.E. Balaghi, E. Safaei, L. Chiang, E.W.Y. Wong, D. Savard, R.M. Clarke, T. Storr, Dalton Trans. 42 (2013) 6829; (h) S.E. Balaghi, E. Safaei, M. Rafiee, M.H. Kowsari, Polyhedron 47 (2012) 94.

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