ELECTRONIC SPECTRAL STUDIES OF THIOSEMICARBAZONE COMPLEXES OF Vo(IV), Co(II), Ni(II) and Cu(II)

ABSTRACT: Diamagnetic character and spectral bands around 19800 and 19420 cm-1 in the Ni(II) complexes indicate square planar geometry. The magnetic moments of the Ni(II) complexes are found in the range (1.75-1.82 B.M.) which are subnormal to the range (2.9-3.4 B.M.) normally expected for octahedral nickel complexes. In the electronic spectra of nickel coplexes bands observed at 8510, 8475, 8530, 8583 (n1); 16100, 15870, 15860, 16130 (n2) and 25320, 25640, 24500, 24390 cm-1 (n3) are attributable to 3A2g(F)®3T2g; 3A2g(F)®3T1g(F) and 3A2g®3T1g(P) transitions respectively. The spectral data are utilized to compute important ligand field parameters using ligand field theory of spin allowed transition in d8 configuration. The values of 10Dq and B can be utilized to calculate n2- and n3. The electronic spectral data together with reported magnetic moment values suggest an octahedral geometry for the nickel complexes. Copper(II) complex shows magnetic moment around 1.82 B.M. which is close to the spin only value for a d9 ion. The electronic spectrum displays a broad band in vicinity of 17980 cm-1 which may be assigned to 2Eg ® 2T2g transition indicating the presence of copper(II) ion in an octahedral field. The magnetic moment of the complex indicates no copper-copper interaction. The absence of any band below 10000 cm-1 or above 17000 cm-1 ruled out the possibility of tetrahedral or square planar symmetry. Broadness of the band in complexes may be due to Jahn Teller distortion. Key Words: Ni (II) complexes, electronic spectrum, ligand field, charge-transfer band