Studies on the Effect of Tetramethylene Sulfoxide and Various Anions on the Stereochemistry of Lanthanide (III) Coordination Compounds of 4[N-(4’-Ethylbenzalidene) Amino]-Antipyrinesemicarbazone

The structural chemistry of the lanthanide (III) compounds has recently undergone considerable development and a wide variety of coordination numbers and geometries have been observed. The coordination numbers exhibited by the tripositive lanthanide ions usually vary from 6 to 10. However, other examples of lanthanide (III) complexes with more than 10- coordination number have also been reported in the literature. In the present studies the effect of tetramethylene sulfoxide (TMSO) on the stereochemistry of the coordination compounds of trivalent lanthanides derived from 4-[N-(4'-ethylbenzalidene) amino] antipyrine semicarbazone (EBAAPS) is reported. The general composition of these coordination compounds is LnX3.n (EBAAPS).TMSO (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy or Ho ; X = NO₃ , n = 1, X = ClO₄ or NCS, n =2). All these compounds were characterized by elemental analysis, molar mass, molar conductance, magnetic susceptibility, infrared and electronic spectra. The infrared studies reveal that the EBAAPS acts as a neutral tridentate (N,N,O), while TMSO is coordinated to the central metal ion via its lone oxygen atom. In nitrato complexes, the nitrates ions are bicovalently bonded, while thiocyanate is coordinated through hard Natom. Perchlorato ions are not participating in coordination and are present outside the coordination sphere. From electronic spectral data, nephelauxetic effect (β), covalence factor (b^1/2), Sinha parameter (δ%)and the covalence angular overlap parameter (η) has been calculated. Antibacterial properties of these compounds were also studied. Thermal studies of these compounds were studied by thermogravimetric analysis. The present studies reveal that the coordination number of lanthanide (III) in the present compounds is either 7 or 10 depending on the nature of anions.