Stabilization of unusual discrete diorganotin carboxylates using the intramolecular coordination approach: synthesis, structure, TD-DFT, and Hirshfeld surface analyses

We report the isolation of five new discrete diorganotin di-/mono-carboxylate structures achieved by employing an intramolecular coordination approach. Two diorganotin dicarboxylates, complexes 1 and 2, were obtained from reactions of R2SnCl2 (R = 2-phenylazophenyl) with pyridine-2,6-dicarboxylic acid and pyrazole-3,5-dicarboxylic acid, respectively, in the presence of a base. However, the reactions of R2SnCl2 with 3,4,5-trimethoxybenzoic acid in different stoichiometric ratios in the presence of a base produced two diorganotin monocarboxylates, complexes 3 and 4. An equimolar reaction of R2SnO with 2-(1,8-naphthalimido)ethanoic acid afforded a dinuclear diorganotin carboxylate [R2Sn(μ-OH){C14H8NO4}]2 (5). All the complexes (1-5) are structurally characterized using single-crystal X-ray diffraction analysis. The molecular structures of complexes (1-5) revealed the retention of both N → Sn intramolecular coordinations. Each tin (Sn) center in complexes (1-5) is present in a high coordination number of seven with distorted pentagonal bipyramidal geometry. Time-dependent density functional theory (TDDFT) calculations revealed that ligand-to-ligand transitions dominate electronic transitions in these complexes. The Hirshfeld surfaces and 2D fingerprint plots were analyzed for all the complexes to understand the intermolecular interactions involved in crystal packing.