Coordination behaviour of Schiff base 2-acetyl-2-thiazoline hydrazone (ATH) towards cobalt(II), nickel(II) and copper(II)

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Polyhedron 27 (2008) 879–886 www.elsevier.com/locate/poly

Coordination behaviour of Schiff base 2-acetyl-2-thiazoline hydrazone (ATH) towards cobalt(II), nickel(II) and copper(II) E. Vin˜uelas-Zahı´nos, M.A. Maldonado-Rogado, F. Luna-Giles *, F.J. Barros-Garcı´a Departamento de Quı´mica Orga´nica e Inorga´nica, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain Received 16 October 2007; accepted 14 November 2007

Abstract The synthesis and characterization of Co(II), Ni(II) and Cu(II) complexes of 2-acetyl-2-thiazoline hydrazone (ATH) are reported. Elemental analysis, IR spectroscopy, UV–Vis–NIR diffuse reflectance and magnetic susceptibility measurement, as well as, in the case of copper complex EPR spectroscopy, have been used to characterize the complexes. In addition, the structure of [NiCl2(ATH)2] (2) and [{CuCl(ATH)}2(l-Cl)2] (3) have been determined by single crystal X-ray diffraction. In all complexes, the ligand ATH bonds to the metal ion through the imine and thiazoline nitrogen atoms. X-ray data indicates that the environment around the nickel atom in 2 may be described as a distorted octahedral geometry with the metallic atom coordinated to two chlorine atoms, two thiazoline nitrogen atoms and two imino nitrogen atoms. With regard to 3, it can be said that its structure consists of dimeric molecules in which copper ions are bridge by two chlorine ligands. The geometry about each copper ion approximates to a distorted square pyramid with each copper atom coordinated to one thiazoline nitrogen atom, one imine nitrogen atom, one terminal chlorine ligand and two bridge chlorine ligands. In compound 3, magnetic susceptibility measurements in the temperature range 2–300 K show an intradimer antiferromagnetic interaction (J = 7.5 cm1). Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Crystal structure; Cobalt complex; Nickel complex; Copper complex; Thiazoline; Hydrazone

1. Introduction In the last few year a renewed interest in metal based therapy has been raised: in fact, on coordination, bioactive ligands might improve their bioactivity profiles, while inactive ligands may acquire pharmacological properties [1–5]. In addition, metal coordination is one of the most efficient strategies in the design of repository, slow release or longacting drugs [6]. Furthermore, metal complexes have gained importance as enzyme inhibitors [7]. In this way, the synthesis, structural investigation and reaction of transition metal Schiff bases have received a special attention, because of their biological activities as antitumoral, antifungal and antiviral activities [8]. Thus, Schiff base hydrazones are also interesting from the point *

Corresponding author. Tel.: +34 924289397; fax: +34 924289395. E-mail address: [email protected] (F. Luna-Giles).

0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2007.11.009

of view of pharmacology. Hydrazone derivatives are found to possess antimicrobial [9], antitubercular [10], anticonvulsant [11] and antiinflammatory [12] activities. Particularly, the antibacterial and antifungal properties of bis acyl hydrazone and their complexes with some first transition metal ions was studied and reported by Carcelli et al. [13]. In addition, complexes of salicylaldehide benzoylhydrazone was shown to be a potent inhibitor of DNA synthesis and cell growth [14]. This hydrazone also has mild bacteriostatic activity and a range of analogues has been investigated as potential oral ion chelating drugs for genetic disorders such as thalasemia [15,16]. Following all these observations and as part our program concerning the chelating behaviour of hydrazones [17,18] we report here the synthesis and the characterization by elemental analysis, IR, UV–Vis–NIR diffuse reflectance and magnetic susceptibility measurement of Co(II), Ni(II) and Cu(II) complexes with 2-acetyl-2-thiazoline

880

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hydrazone (ATH). The Ni(II) and Cu(II) complexes have also been characterized through single crystal X-ray diffraction, as well as electronic paramagnetic resonance (EPR) of the latter. 2. Experimental 2.1. General procedures All reagents were commercial grade materials and were used without further purification. The ligand 2-acetyl-2thiazoline hydrazone (ATH) was synthesized according to a reported procedure [17].

Chemical analyses of carbon, hydrogen, nitrogen and sulphur were performed by means of microanalytical methods using a Perkin–Elmer 240C microanalyser. IR spectra were recorded on a Perkin–Elmer FT-IR 1720 spectrophotometer, from a KBr pellet in the 4000–370 cm1 range and on a Perkin–Elmer FT-IR 1700X spectrophotometer, from a polyethylene pellet in the 500–150 cm1 range. The UV– Vis–NIR reflectance spectra for complexes in the 200– 1500 nm range were registered from a pellet of the sample, using a Shimadzu UV-3101 PC spectrophotometer and BaSO4 as reference. Magnetic susceptibility measurements were performed on polycrystalline samples using a magnetometer with pendulum MANICS DSM8, equipped with helium continuous-flow cryostat and an electromagnetometer DRUSCH EAF 16 UE. Data were corrected for temperature-independent paramagnetism and diamagnetic contributions, which were estimated from the Pascal constants. EPR spectra were recorded at room temperature in solid state and at 77 K in methanol solution employing a BRUKER ESP-300E spectrometer using the X band of microwave. 2.2. Synthesis of [CoCl2(ATH)2] (1) This complex was isolated from an ethanol solution (3 mL) of CoCl2  6H2O (166 mg, 0.7 mmol) that was added to an ethanol solution (25 mL) of ATH (200 mg, 1.4 mmol). After an hour, pink crystalline solid was isolated from the solution at room temperature (104 mg, 36%). Solid was filtered and washed with cold ether and air-dried. Anal. Calc. for C10H18Cl2CoN6S2: C, 28.85; H, 4.35; N, 20.18; S, 15.40. Found: C, 29.23; H, 3.98; N, 20.45; S, 15.15%. IR(KBr): m(NH2) 3367, 3247, 3167; d(NH2) 1616; (ring vibration) 1603; m(C@N) 1546; (ring vibrations) 1000, 950, 734, 682; 653, 602, 564, 448 cm1.

Table 1 Crystal data, data collection and refinement details for 2 and 3

Crystal shape Colour Size (mm) Chemical formula Formula weight Crystal system Space group Unit cell dimensions ˚) a (A ˚) b (A ˚) c (A b (°) ˚ 3) Cell volume (A Z Dcalc (g cm3) l (mm1) F(0 0 0) h Range Index ranges

2

3

plate green 0.62  0.26  0.10 C10H18Cl2N6NiS2 416.0 monoclinic C2=c

prism green 0.48  0.40  0.20 C10H18Cl4N6Cu2S2 555.3 monoclinic P 21 =n

16.730(1) 9.142(1) 12.053(1) 107.566(1) 1757.4(2) 4 1.572 1.646 856 2.6–28.3 21 6 h 6 21, 7 6 k 6 12, 15 6 l 6 15 2013

8.645(2) 12.468(3) 8.941(2) 93.333(4) 962.2(4) 2 1.917 2.989 556 2.8–27.5 11 6 h 6 11, 0 6 k 6 16, 0 6 l 6 11

Independent reflections Observed reflections 1811 [F > 4.0r(F)] Data completeness 0.921 Max/min 0.853/0.428 transmission Number of refined 97 parameters R [F > 4.0r(F)]a 0.034 wR [F > 4.0r(F)]b 0.085 1.062 GOFc ˚ 3) qmax, qmin (e A 0.465, 0.247 P P a R ¼ kF o j  j F c k= j F o j. P P b 2 2 2 R ¼ f ½wðF o  F c Þ = ½wðF 2o Þ2 g1=2 . c The Goodness-of-fit (GOF) equals N params Þg1=2 .

2201 1703 0.996 0.542/0.255 110 0.028 0.067 0.974 0.377, 0.321 P f ½wðF 2o  F 2c Þ2 =ðN rf ln s 

2.3. Synthesis of [NiCl2(ATH)2] (2) This complex was isolated from an ethanol solution (2 mL) of NiCl2  6H2O (83 mg, 0.35 mmol) that was added to an ethanol solution (15 mL) of ATH (100 mg, 0.7 mmol). After several hours, 103 mg (71% yield) of a green solid was recovered filtering. This solid was recrystallized from a ethanol/acetonitrile (1:1 v/v) solution, yielding plate dark green crystals, of considerable size, suitable for X-ray diffraction. Anal. Calc. for C10H18Cl2NiN6S2: C, 29.01; H, 4.38; N, 20.30; S, 15.49. Found: C, 28.99; H, 4.45; N, 20.35; S, 15.21%. IR(KBr): m(NH2) 3335, 3245, 3142; d(NH2) 1619; (ring vibration) 1601; m(C@N) 1546; (ring vibrations) 1001, 954, 741, 683, 642, 602, 562, 435 cm1. 2.4. Synthesis of [{CuCl(ATH)}2(l-Cl)2] (3) This complex was isolated from a methanol solution (2 mL) of CuCl2  2H2O (119 mg, 0.7 mmol) that was

E. Vin˜uelas-Zahı´nos et al. / Polyhedron 27 (2008) 879–886

added to a methanol solution (15 mL) of ATH (100 mg, 0.7 mmol). Green crystals were isolated after a slow evaporation of the solution at room temperature (176 mg, 91%). The crystals were filtered and washed with cold ether and air-dried. Anal. Calc. for C5H9Cl2CuN3S: C, 21.63; H, 3.27; N, 15.13; S, 11.55. Found: C, 21.61; H, 3.37; N, 15.11; S, 11.35%. IR(KBr): m(NH2) 3364, 3255; d(NH2) 1614; (ring vibration) 1581; m(C@N) 1550; (ring vibrations) 1002, 949, 751, 684, 657, 621, 566, 440 cm1. 2.5. X-ray determination structure X-ray diffraction data of 2 and 3 were collected on a Bruker SMART CCD diffractometer with Mo Ka radia˚ , graphite monochromator). The first tion (k = 0.71073 A fifty frames were measured at the end of data collection to monitor instrument and crystal stability. The data were empirically corrected for absorption and other effects using the SADABS [19] program. The structures were solved by direct methods and subsequent Fourier differences using the SHELXS-97 [20] program and refined by full-matrix least-squares on F2 with SHELXL-97 [21], included in WINGX [22] package assuming anisotropic displacement parameters for non-hydrogen atoms. All hydrogen atoms attached to carbon and nitrogen atoms were positioned geometrically, with Uiso values derived from Ueq values of the corresponding carbon and nitrogen atoms. Diagrams were generated using ORTEP3 for Windows [23]. A summary of the crystal data, experimental details and refinement results are listed in Table 1. 3. Results and discussion 3.1. Description of the crystal structures The X-ray study of the complex 2 reveals that the crystals are made up of monoclinic unit cells, each containing four [NiCl2(ATH)2] molecules. The overall view and labelling of the atoms of complex are displayed in Fig. 1.

Fig. 1. Molecular structure of 2, showing the atom-numbering scheme. The thermal ellipsoids are drawn at the 50% probability level.

881

Table 2 ˚ ), angles (°) and hydrogen-bond parameters for 2 Selected bond lengths (A Ni–Cl Ni–N(2) C(1)–C(4)

2.4403(6) 2.089(2) 1.466(3)

Ni–N(1) C(1)–N(1) N(2)–C(4)

2.075(2) 1.275(3) 1.290(3)

N(1)–Ni–Cl N(2)–Ni–Cl N(1)–Ni–N(2) N(1)–Ni–N(2a) Cl–Ni–Cl(a) C(4)–N(2)–Ni N(2)–C(4)–C(1)

169.47(15) 91.83(5) 77.61(7) 94.99(7) 93.99(3) 116.47(15) 112.15(18)

N(1)–Ni–Cl(a) N(2)–Ni–Cl(a) N(1)–Ni–N(1a) N(2)–Ni–N(2a) C(1)–N(1)–Ni N(1)–C(1)–C(4)

86.35(6) 95.58(5) 95.26(11) 169.13(11) 112.52(15) 120.71(19)

Bond A  H–D N(3)–H(3C)  Cl

Position of A x, y, z + 1/2

˚) A  D (A 3.280(2)

A  H–D (°) 146.70(14)

Table 2 lists selected bond lengths, angles and hydrogenbond parameters. The complex cation possesses a C2 symmetry, with the twofold axis placed at the bisector of the Cl–Ni–Cl(a) angle. The environment around the nickel(II) atom may be described as a slightly distorted octahedral geometry with the ligand-metal-ligand bite angles varying between 77.61(7)° [N(1)–Ni–N(2)] and 95.26(11)° [N(1)–Ni–N(1a)]. The metallic atom is coordinated by two chlorine ligands ˚ ], two thiazolinic nitrogen atoms [Ni–Cl = 2.4403(6) A ˚ ] and two iminic nitrogen atoms [Ni–N(1) = 2.075(2) A ˚ ]. [Ni–N(2) = 2.089(2) A The Ni–Cl bond distance is similar to the average value ˚ ] calculated using the data of 52 six-coordi[2.449(60) A nated nickel(II) complexes with a chromophore group NiCl2N4 obtained with CONQUEST software [24] from the Cambridge Structural Database (CSD, Version v5.28, May 2007) [25]. Likewise, the Ni–Nimine bond length is ˚ found for 10 comparable to the mean value 2.073(41) A six-coordinated nickel(II) complexes with a Cl2N4 environment in CSD. Finally, the Ni–Nthiazoline bond length is sim˚) ilar to that found in [Ni(ATsc)2](NO3)2  H2O (av. 2.073 A ˚ ) [26], [Ni(L)[18], [Ni(PyTT)2(H2O)2]Cl2  3H2O (2.061 A ˚ ) [27] and [Ni4(OH)4(tzdt)4(H2O)2]ClO4  H2O (2.057 A ˚ ) [28], but somewhat longer to than (py)4]  2py (2.106 A ˚) that observed in [Ni(TzHy)2(H2O)2]Cl2  2H2O (2.027 A [29]. The five-membered chelate ring is essentially planar. The maximum deviation in relation to the corresponding mean ˚ ]. plane is produced for C(1) [0.055 A The thiazoline ring shows an intermediate conformation between envelope and half-chair, with C(2) and C(3) devi˚ above and below, respectively, the ating 0.095 and 0.116 A plane formed by S, C(1) and N(1). This geometry is proved ˚ and / = 134.5°, by the puckering parameters q = 0.160 A calculated according to Cremer and Pople [30]. The crystal structure is stabilized by hydrogen-bonds Cl  H(3C)–N(3) of intermolecular type. This hydrogen bonding (Fig. 2) produces an one dimensional chain parallel to the c-direction. The molecular structure of the complex 3 is shown in Fig. 3. Selected interatomic distances and angles are listed

E. Vin˜uelas-Zahı´nos et al. / Polyhedron 27 (2008) 879–886

882

Fig. 2. View of the hydrogen bonds of 2.

Fig. 3. Molecular structure of 3, showing the atom-numbering scheme. The thermal ellipsoids are drawn at the 40% probability level.

Table 3 ˚ ) and angles (°) for 3 Selected bond lengths (A Cu–N(1) Cu–Cl(1) Cu–Cl(2a) C(1)–C(4) N(1)–Cu–N(2) N(1)–Cu–Cl(2) N(2)–Cu–Cl(1) N(2)–Cu–Cl(2a) Cl(1)–Cu–Cl(2a) Cu–Cl(2)–Cu(a) C(4)–N(2)–Cu N(2)–C(4)–C(1)

1.984(2) 2.2554(9) 2.6598(8) 1.456(3) 79.04(8) 169.49(6) 166.88(6) 91.22(6) 100.13(3) 90.22(3) 114.78(17) 112.3(2)

Cu–N(2) Cu–Cl(2) C(1)–N(1) N(2)–C(4) N(1)–Cu–Cl(1) N(1)–Cu–Cl(2a) N(2)–Cu–Cl(2) Cl(1)–Cu–Cl(2) Cl(2)–Cu–Cl(2a) C(1)–N(1)–Cu C(4)–C(1)–N(1)

2.077(2) 2.2725(8) 1.280(3) 1.287(3) 93.35(6) 94.85(7) 91.46(6) 95.12(3) 89.78(3) 113.90(17) 120.0(2)

in Table 3. The structure consists of centrosymmetric dimeric [{CuCl(ATH)}2(l-Cl)2] units, in which two chlorine ligands bridge the copper atoms forming a four-membered ring; a terminal chlorine ligand and a bidentate chelating molecule of ATH completing five-coordination at each metal. The bridging Cu2Cl2 unit is strictly planar by the presence of the crystallographic inversion centre in the middle of the dimer. The geometry around the copper centres can be described as a slightly distorted tetragonal pyramid with a s value of 0.04 [31] and a D value of 0.86 [32]. The basal plane is made up of one thiazoline nitrogen atom N(1), one

imine nitrogen atom N(2), the bridging chlorine ligand Cl(2) and the terminal chlorine ligand Cl(1), while the apical site is occupied by the other bridging chlorine ligand Cl(2a). The Cl(2a)–metal–basal ligand angles differ from the ideal value for a square pyramid, ranging between 100.13(3)° [for Cl(1)–Cu–Cl(2a)] and 89.78(3)° [Cl(2)–Cu– Cl(2a)]. Likewise, the basal ligand–metal–basal ligand angles differ from the ideal value, ranging between 95.12(3)° [Cl(1)–Cu–Cl(2)] and 79.04(8)° [N(1)–Cu–N(2)]. The Cu–Cl and Cu  Cu bond lengths have been compared with the mean value calculated using the data of 65 dichlorine-bridged dimers of copper(II) with a Cl3N2 environment obtained from CSD [25]. The Cu–Clterminal ˚ ], the short Cu–Clbridging [Cu– [Cu–Cl(1) = 2.2554(9) A ˚ ], the long Cu–Clbridging [Cu–Cl(2a) = Cl(2) = 2.2725(8) A ˚ ] and the Cu  Cu [Cu  Cu(a) = 3.505(1) A ˚] 2.6598(8) A distances are similar than the calculated average values ˚ ], [2.286(33) A ˚ ], [2.74(10) A ˚ ] and [3.53(14) A ˚ ], [2.257(24) A respectively. The Cu–Nimino bond distance is slightly larger ˚ ] for 21 copthan the calculated average value [1.996(33) A per(II) dimers with this type of unions containing two chlorine bridging ligands and a chromophore group CuCl3N2 in CSD [25]. Finally, the Cu–Nthiazoline bond distance is ˚] comparable to the calculated average value [1.960(38) A for 16 copper(II) complexes with the 2-thiazoline ligand collected in CSD [25]. The five-membered chelate ring is essentially planar with ˚ ]. The maximum mean-plane deviation for N(2) [0.059 A geometry of 2-thiazoline ring is similar to that found in 2. Finally, it should be pointed out that the main difference in complexes 2 and 3 with respect to the structure of free ATH [17] is due to the different degree of rotation of the thiazoline ring around the C(1)–C(4) bond, which permits the coordination through thiazoline nitrogen atom [torsion angle S–C(1)–C(4)–N(2) = 169.4° in 2; 178.0° in 3; 9.6° in ATH]. 3.2. Magnetic susceptibility The observed molar magnetic susceptibility for complex 1 were corrected for diamagnetism and temperature-inde-

E. Vin˜uelas-Zahı´nos et al. / Polyhedron 27 (2008) 879–886

pendent paramagnetism to provide the fully corrected magnetic moment at room temperature, 4.89 BM. This value can be considered in the range 4.7–5.2 BM characteristic of complexes with an high-spin octahedral environment around cobalt(II) [33]. The corrected magnetic moment measured for complex 2 was 3.18 BM, which can be related to an octahedral environment in nickel(II) complexes [34]. The temperature dependence of the molar magnetic susceptibility, vM, for complex 3 was measured in 2–300 K temperature range and the plot of vM and vMT versus T is shown in Fig. 4. The vM value is equal to 2.98  103 cm3 mol1 K (l = 1.89 BM) at room temperature, which is the expected value for two uncoupled copper(II) ions. Upon cooling, the vM value for copper(II) firstly increases to a maximum around 10 K, whereupon it decreases. This behaviour is typical for antiferromagnetic interaction between the two Cu(II) centres of the dimer. The fitting of 1/vM versus T above 10 K with the Curie–Weiss equation yields C = 0.95 cm3 mol1 K and h = 17.2 K, which clearly indicates that magnetic interaction between copper(II) ions is antiferromagnetic [35]. To estimate the magnitude of the antiferromagnetic coupling the magnetic susceptibility data were fitted to the modified Bleaney–Bowers equation for two interacting copper(II) ions (S = 1/2) with the Hamiltonian in the form H = 2JS1  S2. The susceptibility equation for such a dimeric system can be written as follows [36]: vM ¼

2Ng2 l2B K B T ½3 þ expð2J =K B T Þ

ð1Þ

883

where vM represents the susceptibility per mole of dimer, corrected for diamagnetism and temperature independent paramagnetism, J is the exchange coupling and the other symbols have their usual meaning. The average value got from EPR spectrum (2.14) has been taken as g value. An attempt to fit the data to the last expression gave a poor fit in the region around the maximum of vM. In a second approach, the possible presence of paramagnetic impurities was considered. These impurities modify extraordinarily the temperature dependence of vM at low temperature in complexes with antiferromagnetic coupling, stretching vM to infinity at 0 K [37]. The plateau of our experimental data at low temperature (see Fig. 4) confirms this fact. Thus, Bleaney–Bowers expression was modified taking into account the paramagnetic impurities [38] vM ¼

2Ng2 l2B Ng2 l2B ð1  qÞ þ q K B T ½3 þ expð2J =K B T Þ 2K B T

ð2Þ

where q is the amount of paramagnetic impurities. The parameters J and q were determined as adjustable parameters, in a least-squares fitting procedure that led to the values J = 7.52(22) cm1 and q = 0.085(5). The agreement factor R, defined as X h  obs i2 calc 2 =vMJ R¼ vobs MJ  vMJ is then equal to 5.58  104. The value of J parameter implies weak antiferromagnetic interaction. Detailed magneto-structural correlations have been carried out on dinuclear copper(II) complexes with a Cu(l-Cl)2Cu

Fig. 4. vM vs. T (j) and vMT vs. T (O) plot for 3. Solid lines represent the best fit of the data with the model described in the text.

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884

motif containing chlorine bridging ligands. In these complexes, the local geometry around the two metal centre is usually a square pyramid with a different degree of distortion towards a trigonal bipyramid. The global arrangement for the square-pyramidal polyhedra can be defined as coplanar, parallel and perpendicular [39]. The extended Hu¨ckel calculations performed by Rodrı´guez et al. [39,40] show that the super exchange pathway with the metal centres will take place mainly through a p* type interaction between the d x2 y 2 orbitals of Cu(II) ions and the p orbitals of chlorine bridging ligands for square pyramids with parallel basal planes sharing one base-to-apex edge, as it is the case of 3. For an ideal geometry with a square core, the overlap integral between the former orbitals would be zero. As above, these complexes with parallel arrangement for square pyramids present very small J values, which are due to structural deviations from the ideal square Cu2Cl2 core. The small calculated J value for 3 is therefore consistent with the calculations performed by the aforementioned authors.

The calculated values of the ligand field parameters 10Dq = 10 331 cm1 and B = 834 cm1 are consistent with the presence of a chromophore group [NiIIN4Cl2] [46,47]. Electronic reflectance spectrum of the copper(II) complex 3 displays one strong band at 26 738 cm1 which can be assigned to Cl ? Cu charge transfer transition [48,49]. Moreover, the reflectance spectrum exhibits a broad band centred at 13 850 cm1 with a shoulder at 12 315 cm1, assigned to the 2B1 ? 2A1 and 2B1 ? 2B2, 2E transitions, respectively, in agreement with the square-pyramidal stereochemistry [50] that presents this complex. EPR spectra of a polycrystalline sample at 298 K (Fig. 5) and at 77 K (Fig. 6) of complex 3 were recorded in the X-band, using the 100 kHz field modulation. The EPR parameters are presented in Table 4. The spectrum of 3 at 298 K is typically elongated axial with well defined g\ and gk values. The geometric parameter

3.3. Spectroscopic studies Cobalt(II) complex 1 exhibits a typical electronic spectrum for octahedral species in the solid state [41]. Two main bands are observed in the 7000–25 000 cm1 range, which are assigned to the m1 [4T1g(F) ? 4T2g(F)] (9295 cm1) and m3 [4T1g(F) ? 4T1g(P)] (20 160 cm1) transitions. Moreover, the spectrum shows one intense band at 31 055 cm1 with a shoulder at 34 965 cm1 which are assigned to a charge-transfer band and the p ? p* transition of the organic ligand, respectively. Ligand field parameters, 10Dq and B, were calculated using the following known Konig’s equations [42]: 1 1 1 m1 ¼ ð10Dq  15BÞ þ ½ð10Dq þ 15BÞ2  12B  10Dq2 2 2 1 2 m3 ¼ ½ð10Dq þ 15BÞ  12B  10Dq2

Experimental Simulated

2600

2800

3000

3200

3400

3600

3800

4000

G Fig. 5. EPR spectrum of 3 in the polycrystalline state at 298 K.

The calculated values of the ligand field parameters 10Dq = 10 478 cm1 and B = 803 cm1 are in good agreement with the predicted values for octahedral complexes of Co(II) [43–45]. Electronic spectrum of the nickel(II) complex 2 shows one intense band at 33 557 cm1, which is assigned to charger transfer band. Moreover, the spectrum exhibits bands at 10 331 and 16 474 cm1, all of which were of low intensity. These bands may be assigned as: m1[3A2g(F) ? 3 T2g(F)] (10 331 cm1) and m2[3A2g(F) ? 3T1g(F)] (16 474 cm1) transitions, in an idealized Oh symmetry. The position of the observed d–d transitions permits to calculate the ligand field parameters, 10Dq and B, using the following known relationships [42]:

Experimental Simulated

3

m1 ½ A2g ðFÞ!3 T2g ðFÞ ¼ 10Dq 3

m2 ½ A2g ðFÞ!3 T1g ðFÞ ¼ ð1=2Þð15B þ 30DqÞ 2

 ð1=2Þ½ð15B  10DqÞ þ 12B  10Dq

2000

2500

3000

3500

G

1=2

Fig. 6. EPR spectrum of 3 in methanol solution at 77 K.

4000

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chlorine ligands. The copper centres are penta-coordinated with a slight distortion from square-pyramidal geometry and present a weak ferromagnetic through chlorine-bridge.

Table 4 EPR parameters of 3 Solid (298 K)

885

Methanol (77 K)

g\

gk

G

g3

g2

g1

R

2.05

2.23

3.80

2.22

2.15

2.08

1.0

Acknowledgements

Table 5 Far IR bands (cm1) with tentative assignments

We would like to thank the Junta de Extremadura (Consejerı´a de Educacio´n, Ciencia y Tecnologı´a) and the FEDER [Project 2PR04A011] for financial support.

Compound m(M–Nimino) m(M–Nthiazoline) m(M–Clterminal) m(M–Clterminal), m(M–Clbridge)

Appendix A. Supplementary material

325 312 333 325

1 2 3

255

213

271 253

214 304 292

G = (gk  2)/(g\  2) value is found to be in the range 3.5– 5.0 and gk > g\ > 2.0023, which is consistent with a distorted square-pyramidal geometry with a ðd x2 y 2 Þ1 ground state [51,52]. These results are in good accord with the Xray structural determination data. With regard to the EPR spectrum in frozen methanol (77 K) is typically compressed rhombic. The geometric parameter R = (g2  g1)/(g3  g2) value is 1, which gives no information indicative to ground state in solution [50–53]. In the low frequency region, the IR spectra of these complexes show bands assignable to metal-ligand stretching vibrations. Tentative assignments are listed in Table 5. Thus, the m(M–Nimino) vibrations [54–56] are registered at 312–333 cm1, the bands in the region 253–271 cm1 can be attributed to m(M–Nthiazoline) vibration [26,44,45,57] and the bands due to m(M–Clterminal) vibrations [58–63] are found in the range 213–304 cm1. Finally the bands at 292 and 304 cm1 in the spectrum of Cu(II) complex can also include the m(M–Clbridge) vibration according to Refs. [58,59,61]. 4. Conclusion In summary we have synthesized and structurally characterized Co(II), Ni(II) and Cu(II) complexes with 2-acetyl-2-thiazoline hydrazone (ATH). In the same way as that in the cadmium(II) complex preliminary reported [17], it should be pointed out that ATH acts as bidentate ligand coordinating to the metal ion through the imine and thiazoline nitrogen atoms. A study of all the characterization methods applied for complex 1 suggests that cobalt(II) ion presents an octahedral environment. Thus, complex 1 could be formulated as [CoCl2(ATH)2]. Crystallographic study of 2 shows a distorted octahedral geometry around the nickel(II), meanwhile the structure of complex 3 is consistent with a dimer copper(II) complex doubly bridged by

1

The unpaired electron is located in d x2 y 2 .

CCDC 271430 and 663500 contain the supplementary crystallographic data for 2 and 3. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/ conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ ccdc.cam.ac.uk. Supplementary data associated with this article can be found, in the online version, at doi: 10.1016/j.poly.2007.11.009. References [1] R.A. Sa´nchez-Delgado, M. Navarro, H. Pe´rez, J.A. Urbina, J. Med. Chem. 39 (1996) 1095. [2] M. Navarro, H. Pe´rez, R.A. Sa´nchez-Delgado, J. Med. Chem. 40 (1997) 1937. [3] Z.H. Chohan, A. Rauf, J. Inorg. Biochem. 46 (1992) 41. [4] R. Malhotra, J.P. Singh, M. Dudeja, K.S. Dhindsa, J. Inorg. Biochem. 46 (1992) 119. [5] F. Lebon, M. Ledecq, Z. Benatallah, S. Sicsic, R. Lapouyade, O. Kahan, A. Garcon, M. Reboud-Ravaux, F.J. Durant, J. Chem. Soc., Perkin Trans. 2 (1999) 795. [6] N. Bharti, M.R. Maurya, F. Naqvi, A. Bhattacharya, S. Bhattacharya, A. Azam, Eur. J. Med. Chem. 35 (2000) 481. [7] A.Y. Louie, T.J. Meade, Chem. Rev. 99 (1999) 2711. [8] S.K. Sridhar, S.N. Pandeya, J.P. Stables, A. Ramesh, Eur. J. Pharm. Sci. 16 (2002) 129. [9] P. Vicini, F. Zani, P. Cozzini, I. Doytchinova, Eur. J. Med. Chem. 37 (2002) 553. [10] B. Kocyigit-Kaymakcioglu, S. Rollas, Farmaco 57 (2002) 595. [11] J.V. Ragavendran, D. Sriram, S.K. Patel, I.V. Reddy, N. Bharathwajan, J. Stables, P. Yogeeswari, Eur. J. Med. Chem. 42 (2007) 146. [12] S. Rollas, N. Gulerman, H. Erdeniz, Farmaco 57 (2002) 171. [13] M. Carcelli, P. Mazza, C. Pelizi, F. Zani, J. Inorg. Biochem. 57 (1995) 43. [14] D.K. Johnson, T.B. Murphy, N.J. Rose, W.H. Goodwin, L. Pickart, Inorg. Chim. Acta 67 (1982) 159. [15] J.D. Ranford, J.J. Vittal, Y.M. Wang, Inorg. Chem. 37 (1998) 1226. [16] J.L. Buss, B.T. Greene, J. Turner, F.M. Torti, S.V. Torti, Curr. Top. Med. Chem. 4 (2004) 1623. [17] F.J. Barros-Garcı´a, A. Bernalte-Garcı´a, F. Luna-Giles, M.A. Maldonado-Rogado, E. Vin˜uelas-Zahı´nos, Polyhedron 24 (2005) 1125. [18] F.J. Barros-Garcı´a, F. Luna-Giles, M.A. Maldonado-Rogado, E. Vin˜uelas-Zahı´nos, Polyhedron 24 (2005) 2972. [19] SADABS, version 2.03 Bruker AXS Inc., Madison, WI, 2001. [20] M. Sheldrick, SHELXS-97, Program for Crystal Structures Solution, University of Go¨ttingen, Germany, 1997. [21] M. Sheldrick, SHELXL-97, Program for Crystal Structures Refinement, University of Go¨ttingen, Germany, 1997. [22] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837. [23] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.

886

E. Vin˜uelas-Zahı´nos et al. / Polyhedron 27 (2008) 879–886

[24] F.H. Allen, Acta Crystallogr., Sect. B 58 (2002) 380. [25] I.J. Bruno, J.C. Cole, P.R. Edington, M. Kessler, C.F. Macrae, P. McCabe, J. Pearson, R. Taylor, Acta Crystallogr., Sect. B 58 (2002) 389. [26] A. Bernalte-Garcı´a, F.J. Garcı´a-Barros, F.J. Higes-Rolando, F. Luna-Giles, Polyhedron 18 (1999) 2907. [27] K.V. Domasevich, E.B. Rusanov, E.K. Yudin, M.D. Kruglyak, A.A. Mokhir, Russ. J. Inorg. Chem. 40 (1995) 1874. [28] L. Ballester, E. Coronado, A. Gutie´rrez, A. Monge, M.F. Perpin˜a´n, E. Pinilla, T. Rico, Inorg. Chem. 31 (1992) 2053. [29] A. Bernalte-Garcı´a, M.A. Dı´az-Dı´ez, F.J. Garcı´a-Barros, F.J. HigesRolando, A.M. Pizarro-Gala´n, J. Romero-Garzo´n, C. ValenzuelaCalahorro, Polyhedron 15 (1996) 1691. [30] D. Cremer, J.A. Pople, J. Am. Chem. Soc. 97 (1975) 1354. [31] A.W. Addison, T.N. Rao, J. Reedijk, J. van Rijn, G.C. Verschorr, J. Chem. Soc., Dalton Trans. (1984) 1349. [32] E.L. Muetterties, L.J. Guggenberger, J. Am. Chem. Soc. 96 (1974) 1748. [33] B.N. Figgis, J. Lewis, Prog. Inorg. Chem. 6 (1967) 185. [34] J. Reedijk, P.W.N.M. van Leeuwen, W.L. Groeneveld, Rec. Trav. Chim. Pays-Bas 87 (1968) 129. [35] M. Melnik, M. Koman, D. Hudecova, J. Moncol, B. Dudova, T. Glowiak, J. Mrozinski, C.E. Holloway, Inorg. Chim. Acta 308 (2000) 1. [36] B. Bleaney, K.D. Bowers, Proc. R. Soc. London Ser. A 214 (1952) 451. [37] J. Ribas Gispert, Quı´mica De Coordinacio´n, Omega, Barcelona, 2000. [38] O. Kahn, Molecular Magnetism, VCH, New York, 1993. [39] M. Rodrı´guez, A. Llobet, M. Corbella, A.E. Martell, J. Reibenspies, Inorg. Chem. 38 (1999) 2328. [40] M. Rodrı´guez, A. Llobet, M. Corbella, Polyhedron 19 (2000) 2483. [41] A.B.P. Lever, Inorganic Electronic Spectroscopy, 2nd ed., Elsevier, Amsterdam, 1984. [42] D.K. Rastogi, K.C. Sharma, S.K. Dua, M.P. Teotia, J. Inorg. Nucl. Chem. 37 (1975) 685. [43] G. Alzuet, S. Ferrer, J. Borra´s, A. Castin˜eiras, X. Solans, M. FontBardı´a, Polyhedron 11 (1992) 2849.

[44] A. Bernalte-Garcı´a, A.M. Lozano-Vila, F. Luna-Giles, R. PedreroMarı´n, Polyhedron 25 (2006) 1399. [45] A. Bernalte-Garcı´a, F.J. Garcı´a-Barros, F.J. Higes-Rolando, F. Luna-Giles, M.M. Pacheco-Rodrı´guez, E. Vin˜uelas-Zahı´nos, Bioinorg. Chem. Appl. 2 (2004) 307. [46] C. Ochs, F.E. Hahn, T. Lu¨gger, Eur. J. Inorg. Chem. (2001) 1279. [47] L. Sacconi, F. Mani, A. Bencini, in: G. Wilkinson (Ed.), Comprehensive Coordination Chemistry, vol. 5, Pergamon Press, Oxford, 1987. [48] S. Menon, M.V. Rajasekharan, Polyhedron 17 (1998) 2463. [49] A.M. Schuitema, A.F. Stassen, W.L. Driessen, J. Reedijk, Inorg. Chim. Acta 337 (2002) 48. [50] J. Hathaway, in: G. Wilkinson (Ed.), Comprehensive Coordination Chemistry, vol. 5, Pergamon Press, Oxford, 1987. [51] B.J. Hathaway, J. Chem. Soc., Dalton Trans. (1972) 1196. [52] S. Tyagi, B.J. Hathaway, J. Chem. Soc., Dalton Trans. (1981) 2029. [53] W. Fitzgerald, B.J. Hathaway, J. Chem. Soc., Dalton Trans. (1981) 567. [54] A. Bernalte-Garcı´a, F.J. Garcı´a-Barros, F.J. Higes-Rolando, F. Luna-Giles, Polyhedron 20 (2001) 3315. [55] M. Shakir, S.P. Varkey, F. Firdaus, P.S. Hamed, Polyhedron 13 (1994) 2319. [56] F.J. Barros-Garcı´a, A. Bernalte-Garcı´a, F.J. Higes-Rolando, F. Luna-Giles, A.M. Pizarro-Gala´n, E. Vin˜uelas-Zahı´nos, Z. Anorg. Allg. Chem. 631 (2005) 1898. [57] F.J. Barros-Garcı´a, A. Bernalte-Garcı´a, F.J. Higes-Rolando, F. Luna-Giles, M.A. Maldonado-Rogado, E. Vin˜uelas-Zahı´nos, Inorg. Chim. Acta 357 (2004) 3574. [58] J.R. Ferraro, Low-frequency Vibrations of Inorganic and Coordination Compounds, Plenum Press, New York, 1971. [59] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compound, 5th ed., Wiley, New York, 1997. [60] G. Ibrahim, M.A. Khan, P. Richomme, O. Benali-Baitich, G. Bouet, Polyhedron 16 (1997) 3455. [61] A. Bernalte-Garcı´a, F.J. Garcı´a-Barros, F.J. Higes-Rolando, F. Luna-Giles, R. Pedrero-Marı´n, J. Inorg. Biochem. 98 (2004) 15. [62] M. Shakir, H.-T.-N. Chishti, P. Chingsubam, Spectrochim. Acta A 64 (2006) 512. [63] M. Joseph, V. Suni, M.R.P. Kurup, M. Nethaji, A. Kishore, S.G. Bhat, Polyhedron 23 (2004) 3064.