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Synthesis, Characterization and Biological Evaluation of a Novel Series of Mixed Ligand Complexes of Lanthanides(III) with 4[N-(Furfural)amino]antipyrine Semicarbazone as Primary Ligand and Diphenyl Sulfoxide as Secondary Ligand

S. Prasad^a,* R.K. Agarwal^a,b,* and A. Kumar^b

^aDivision of Chemical Sciences, Faculty of Science, Technology and Environment, The University of the South Pacific, Suva, Fiji
^bPresent address: Department of Chemistry, Lajpat Rai Postgraduate College, Sahibabad, Ghaziabad 201005, India

A novel series of complexes of lanthanides(III) with 4[N-(furfuralamino]antipyrine semicarbazone (FFAAPS) as the primary ligand and diphenyl sulfoxide (DPSO) as the secondary ligand with the general composition LnX₃(FFAAPS)_nDPSO (X = NO₃^-,   n = 1; X = NCS^- or ClO₄^-, n = 2; Ln = La³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Tb³⁺, Dy³⁺ or Ho³⁺), is reported. All the synthesized complexes were characterized through various physico-chemical techniques i.e.elemental analysis, conductance measurements and magnetic susceptibilities, spectroscopic and thermal studies. The coordinated FFAAPS behaved as tridentate N,N,O-donor, while DPSO acted as unidentate oxygen donor. Nitrates were bicovalently bonded, while the thiocyanate was coordinated through N-atom. Perchlorate ions did not participate in the coordination sphere. The absorption bands of the representative Pr(III), Nd(III) and Sm(III) complexes in the visible and near infrared region appeared due to transitions from the ground levels to the excited J-levels of 4f-configuration. From the hypersensitive bands, the nephelauxetic effect (β) was calculated. And from the β-values, the covalence factor (b^1/2), Sinha parameter (σ%) and the covalency angular overlap (η) were calculated. The ligand and the corresponding lanthanide(III) complexes were simultaneously screened for their antibacterial and antifungal activities. Thermal stabilities of these complexes were studied by thermogravimetric analysis. Depending on the nature of the anionic ligands, the coordination number of the lanthanide(III) in the case of nitrate or thiocyanate complexes was ten, while it was seven in the case of perchlorate complexes.

Keywords: Lanthanides, Semicarbazone complexes, Diphenyl sulfoxide, Coordination compounds, Biological properties