Tin(IV) halide complexes with 5,7-dimethyl-8-quinolinol: structures, optical and thermal properties

Three new tin(IV) halide complexes with 5,7-dimethyl-8-quinolinol (dmqo), Sn(dmqo)(2)F-2 (1), Sn(dmqo)(2)Cl-2 (2a and 2 b), and Sn(dmqo)(2)I-2 (3), have been synthesized and characterized by single-crystal X-ray diffraction, UV-Vis spectroscopy, fluorescence, and thermal analysis. The three crystals are of the monoclinic system with space group P2(1)/c. A second polymorph of 2 was observed in the space group C2/c. The Sn(IV) center is six coordinate with two bidentate ligands with N and O donor atoms and two halides in a slightly distorted octahedral geometry. The tin(IV) complexes exhibit parallel displaced packing configuration between 5,7-dimethyl-8-quinolinol ligands. Increasing the size of the halide coordinated with the Sn(IV) center increases molecular packing distortion, resulting in weakening pi-pi interactions between pyridyl rings. Photoluminescence and thermal properties are affected by halide coordination with tin. The relative quantum yields of Sn(dmqo)(2)F-2 and Sn(dmqo)(2)Cl-2 are higher than that of Sn(dmqo)(2)I-2. Complexes 1 and 2 show interesting blue-shifted emissions in the solid state compared to solution. Thermal stability decreases in the order of increasing the size of halide coordinated to Sn(IV).