ЖУРНАЛ НЕОРГАНИЧЕСКОЙ ХИМИИ, 2011, том 56, № 3, с. 463-470
ФИЗИЧЕСКИЕ МЕТОДЫ ИССЛЕДОВАНИЯ
УДК 541.49
SPECTRAL, MAGNETIC AND THERMAL STUDIES ON HOMOMETALLIC
AND HETEROMETALLIC COMPLEXES OF PIPERANOL THIOSEMICARBAZONE
© 2011 г. Ahmed A. El-Asmy*, Sherif A. Mandour
Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt Поступила в редакцию 08.10.2009 г.
Piperanol thiosemicarbazone (HL) has been interacted with Ag+, Co(II), Ni(II) or Cu(II) binary to produce [Ag(HL)]EtOH ■ NO3, [Ag2(L)(H2O)2]NO3, [Co(L)3], [Cu(L)(H2O)3(OAc)]H2O or [Ni(L)2] and template with Ag+ to form [Cu2Ag2(L)2(OH)2(H2O)4]NO3 and [NiAg(L)2(H2O)2]NO3. The prepared complexes are characterized by microanalysis, thermal, magnetic and spectral (IR, XH NMR, ESR and electronic) studies. Ag+ plays an important role in the complex formation. The variation in coordination may be due to the presence of two different metal ions and the preparation conditions. The outside nitrate is investigated by IR spectra. The outer sphere solvents are detected by IR and thermal analysis. Ni(II) complexes are found diamagnetic having a square-planar geometry. Cu(II) is reduced by the ligand to Cu(I). The cobalt complex is found diamagnetic confirming an air oxidation of Co(II) to Co(III) having a low spin octahedral geometry. The ligand and its metal complexes are found reducing agents which decolorized KMnO4 solution in 2N H2SO4. CoNS and NiNS are the residual parts in the thermal decomposition of [Co(L)3] and [Ni(L)2].
Keywords: Thiosemicarbazones; Heterobimetallic complexes; Spectroscopic; Thermogravimety.
1. INTRODUCTION
Binuclear complexes have a great interest because they react with unsaturated and small molecules to give new substrates interesting for catalysis [1]. Much of the study of bimetallic cluster complexes stems from the discoveries that Pt catalysts alloyed with Ir, Re or Sn exhibit properties in petroleum reforming. Bimetallic cluster complexes are valuable precursors for supported bimetallic catalysts, because they contain intimately associated combinations of the metal components, their stoichiom-etries can be accurately controlled and may provide better control of the size of the metal particles [2].
The ability of silver to form heterometallic aggregates with transition metal complexes was reviewed [3]. Heter-obimetallic compounds have become important in drug design.
Thiosemicarbazones and organtins are interesting in various biological effects [4]. Binuclear complexes are of extensive investigation owing to their biological and in-
♦Corresponding author. Tel: 0020101645966. E-mail address: aelasmy@yahoo.com (A.A. El-Asmy).
dustrial applications [5]. Interest in syntheses and magnetic properties ofheterobimetallic complexes propagated by multi atom bridges aimed at understanding the nature of electronic exchange coupling through multi atom bridging ligands and mimicking the active sites and functions of biological substances and designing and preparing new magnetic materials and investigating the spin exchange [6].
Compounds containing sulfur are promising due to their pharmaceutical properties [7, 8]. They have a remarkable interest due to their ability to form stable che-lates with the essential metal ions in which the fungus needs in its metabolism [9]. Transition metal complexes of some thiosemicarbazones possess some degree of cy-totoxin activity [10].
Till now, no work was done on homo- or heterometallic complexes of piperanol thiosemicarbazone (its molecular modeling is shown in Scheme 1 and the length and angles of its bonds are presented in Table 1).
2. EXPERIMENTAL
All materials were purchased from Aldrich, Merck or BDH Chemicals. Piperanol thiosemicarbazone was prepared by a similar method as previously reported [11]. The purity of the ligand was checked by TLC and confirmed by IR and 1H NMR spectra.
2.1. Synthesis of complexes
The homometallic complexes were prepared by heating under reflux a mixture of the ligand (2 mmol) in 30 ml absolute ethanol, and the metal salts (2 mmol), in 20 ml absolute ethanol on a water bath for 2—4 h.
The heterometallic complexes were prepared by heating the same mixture on a water bath for 4—6 h but in the pres-
Table 1. Bond lengths (A) and angles (°) for the different bonds in HL
N(14)-H(24) 0.9946 C(10)-N(11) 1.3067
N(14)-H(23) 0.9949 C(8)-O(9) 1.4384
C(13)-S(15) 1.6581 O(7)-C(8) 1.4398
C(13)-N(14) 1.4068 C(5)-O(9) 1.3882
N(12)-H(22) 0.9983 C(4)-O(7) 1.3850
N(12)-C(13) 1.4068 C(4)-C(5) 1.4129
N(11)-N(12) 1.3900 C(1)-C(10) 1.4616
H(24)N(14)H(23) 114.5559 N(11)C(10)C(1) 119.5966
H(24)N(14)C(13) 118.4739 C(8)O(9)C(5) 106.0894
H(23)N(14)C(13) 114.3105 O(9)C(8)O(7) 108.7349
S(15)C(13)N(14) 119.6209 C(8)O(7)C(4) 106.1455
S(15)C(13)N(12) 127.4839 O(9)C(5)C(6) 128.2877
N(14)C(13)N(12) 112.4598 O(9)C(5)C(4) 109.4710
H(22)N(12)C(13) 118.3614 C(6)C(5)C(4) 122.2414
H(22)N(12)N(11) 107.1126 O(7)C(4)C(5) 109.5592
C(13)N(12)N(11) 128.1788 O(7)C(4)C(3) 128.5529
N(12)N(11)C(10) 125.0397 C(5)C(4)C(3) 121.8879
ence ofAgNO3 (1 mmol) dissolved in 10 ml doubly distilled water, in a round flask surrounded with aluminum foil. The preparation of [Cu2Ag2(L)(OH)2(H2O)4]NO3 is described in detail. To 100 ml reaction flask, surrounded with aluminum foil, 0.44 g (2 mmol) ofHL, in 30 ml ethanol, and 0.40 g (2 mmol) of Cu(OAc)2 ■ H2O, in 20 ml distilled water were added and heated on a water bath for 5 min, then 0.34 g (2 mmol) of AgNO3, in 10 ml distilled water, was added and the reaction mixture was heated for 4 h. The precipitate thus formed was removed by filtration, washed with H2O, EtOH and Et2O then dried at 80°C. In all preparations, the yields are 60—75%.
2.2. Chemical and physical measurements
C, H and N content ofthe complexes were performed at the Microanalytical Unit of Cairo University. Ag(I), Co(II), Ni(II) Cu(II) and Fe(III) were determined either complexometrically using xylenol orange as an indicator or gravimetrically (Ag as AgCl); in some cases Ag+ was determined using ammonium thiocyanate by Vfolhard' method. The IR, UV-Vis. and 1H NMR, in d6-DMSO (200 MHz) spectra were recorded on a Mattson 5000 FTIR Spectrophotometer, UV2 Unicam UV/Vs, and Vrian MAT 311 Spectrometers, respectively. Thermo-gravimetric analysis was performed using an automatic recording thermo balance, type 951 DuPont; samples were subjected to heat on a rate of10°C/min (25—750°C) in N2. All theoretical calculations of the quantum chemistry were performed on a Pentium 4 (3 GHz) computer using HyperChem 7.5 program system [HyperChem 7.51 Version, Hypercube Inc., Florida, USA, 2003]. Initially, molecular geometries of the ligand and its metal(II) complexes were optimized using molecular mechanics (MM+). Secondly, the low lying obtained from MM+ was then optimized at the Semi-Empirical Parameterization (PM3) using the Polak-Ribiere algorithm in RHF-SCF, set to terminate at an RMS gradient of 0.01 kcal A-1 mol-1 and convergence limit was fixed to 1 x 10-8 kcal mol-1.
Table 2. Effect of some organic solvents on the ligand
Solvent Bands (nm) Concentration Molar absorpitivity (s, mol-1 L)
Water 212; 300; 318; 346 P.S. -
Methanol 224; 304; 320*; 346 1.16 x 10-4 2.13 x 104
Ethanol 216; 292; 304; 322*; 342; 348 1.16 x 10-4 2.11 x 104
Chloroform 232; 286; 306; 324; 338; 350 P.S. -
Benzene 308; 324; 338; 352 P.S. -
Acetone 344; 356 P.S.
DMF 297; 308; 322; 335*; 347 4.64 x 10-5 0.3 x 105
DMSO 297; 308; 325; 335*; 349 7.80 x 10-5 0.23 x 105
* The band used to calculate s; P.S. — partially soluble.
3. RESULTS AND DISCUSSION 3.1. Effect of solvents on the ligand
The effect of some polar and nonpolar organic solvents on the ligand was studied. The spectrum of HL was recorded on H2O, C2H5OH, CH3OH, CH3Cl, acetone, benzene, DMF and DMSO. The spectrum in H2O showed bands at 212, 300, 318 and 346 nm. The spectrum in benzene (nonpolar molecule) has four weak bands at 308, 324, 338 and 352 nm. It is observed that the spectrum changed from polar to nonpolar solvent due to the formation ofhydrogen bonding with H2O rather than with benzene. One may calculate the strength of the hydrogen bonding from the difference of the bands between 318 and 338 nm. The spectra in CH3OH, C2H5OH and CH3Cl are nearly similar indicating that the three solvents have the same polarity toward the ligand. The bands
observed at (224, 304, 320 and 346 nm), (216, 304, 322, 342 and 348 nm), and (232, 306, 324, 338 and 350 nm) are found in CH3OH, C2H5OH, and CH3Cl, respectively. The spectra in DMF and DMSO are similar with a band at 335 nm. The molar absorpitivity in both solvents are found to be 0.3 x 105 and 0.23 x 105 mol-1 L, respectively. In acetone, two bands are observed at 344 and 356 nm indicating high polarity and chelating agent. The bands are presented in Table 2. The last band may arrange the different solvents as:
H2O < CH3OH < DMF < CH3CH2OH < < DMSO < CH3Cl < C6H6 < CH3COCH3.
3.2. Characterization of the metal complexes
Homometallic and heterobimetallic complexes of HL have been isolated in a pure state. The analytical data and some physical properties of the complexes are listed in Table 3. The homometallic complexes have the formulae: [Ag(HL)]EtOH ■ NO3, [Ag2(L)(H2O)2]NO3, [Co(L)3], [Cu2(L)(H2O)3(OAc)]H2O and [Ni(L)J. The reaction (ligand + Co(II) acetate + AgNO3) gave [Ag2(L)(H2O)2]NO3 instead ofheterometallic complex. On the other hand, the formed heterometallic complexes have the formulae: [NiAg(L)2(H2O)2]NO3 and [Cu2Ag2(L)(OH)2(H2O)4]NO3. The first complex was isolated from the reaction (ligand + Ni(II) nitrate + + AgNO3).
The isolated homo and heterometallic complexes appear brown or olive green; quite stable in atmospheric conditions; insoluble in water, ethanol and diethyl ether; partially soluble in DMSO and DMF except for the Co(III) and Ni(II) complexes which are completely soluble. The complexes have melting points >300°C. All of the complexes are found diamagnetic, in spite of the pr
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