Synthesis, structural characterization and cytotoxic activity of triorganotin 5‐(salicylideneamino)salicylates

Abstract

Six new triorganotin complexes (1a–1c and 2a–2c) of 5‐(salicylideneamino)salicylic acid, [5‐(3‐X‐2‐HOC6H3CH═N)‐2‐HOC6H3COO]SnR3 (X = H, 1; CH3O, 2; R = Ph, a; Cy, b; CH2C(CH3)2Ph, c), have been synthesized by one‐pot reaction of 5‐aminosalicylic acid, salicylaldehyde and triorganotin hydroxide and characterized using elemental analysis and infrared and NMR (1H, 13C and 119Sn) spectra. The crystal structures of 1a, 1b, 2a·CH3OH, 2b·CH3OH and 2c·CHCl3 have been determined using single‐crystal X‐ray diffraction. In non‐coordinated solvent CDCl3, the tin atoms in the complexes are all four‐coordinated. In the crystalline state, these compounds adopt a four‐ or five‐coordination mode. Complex 1a exhibits a 44‐membered macrocyclic tetrameric structure with trigonal bipyramidal geometry around the tin atoms in which the axial positions are occupied by the oxygen atom of carboxylate group of the ligand and the phenolic oxygen atom from the adjacent ligand. The coordination geometry of tin atom in 1b and 2c·CHCl3 is a distorted tetrahedron shaped by three carbon atoms of alkyl groups and a carboxylate oxygen atom of the ligand. In 2a·CH3OH and 2b·CH3OH, the tin atom has a distorted trans‐C3SnO2 trigonal bipyramidal geometry formed by three alkyl groups, a monodentate carboxylate group and a coordinated methanol molecule. The molecules of 2a·CH3OH and 2b·CH3OH are linked via O─H···O hydrogen bonds into a one‐dimensional supramolecular chain and a centrosymmetric R44(22) macrocycle, respectively. Bioassay results against two human tumor cell types (A549 and HeLa) show the complexes are efficient cytostatic agents and may be explored as potential antitumor drugs.