Novel binuclear and polymeric diorganotin (IV) complexes with N-nicotinyl phosphoramides: Synthesis, characterization, structural studies and anticancer activity

Abstract

Two new diorganotin complexes with formula {SnCl2(CH3)2L1}2 (C1), L1 = N-nicotinyl, N′,N″-bis(diethylamine) phosphoric triamide and {SnCl2(CH3)2L2}n (C2), L2 = N-nicotinyl, N′,N″-bis(cyclopentylamine) phosphoric triamide were synthesized and characterized by IR and NMR spectroscopy, and elemental analysis. Single crystal X-ray diffraction structural analyses confirmed all-trans and cis–trans configurations for distorted octahedral geometry in C1 and C2, respectively. Also, it revealed that the coordination of L1 and L2 to Sn atom results to a binuclear arrangement in C1 and one-dimensional polymeric chain in C2. The relative stability of M1 (SnCl2(CH3)2L1) and M2 (SnCl2(CH3)2L2) units in binuclear and polymeric arrangements were compared using density functional theory (DFT) calculations. Based on theoretical findings, M1 and M2 prefer polymeric chain structure from energy point of view though the stability difference of M1, in two arrangements, was much lower compared to stability difference of M2. Furthermore, nature of bonds and Sn–ligand interactions was studied by NBO analyses. In vitro cytotoxic assay of complexes against breast cancer cell lines MCF-7, MDA-MB-468 and T47-Dhuman, were also reported. MDA-MB-468 cells are exquisitely sensitive to cell death induced by C1 and C2 complexes treatment. C1 complex exhibited higher anticancer activity, compared to C2, which can be attributed to larger ClSnCl angle in C1.