Synthesis of coumarin derivaties of dioxybiphenyl-bridged spiro cylotriphosphazenes fluorescence properties and DFT calculations

The main aim of this study is to obtain derivatives with new applications by the reaction of coumarin and its derivatives, a class of chemicals well known for their photophysical importance, with cyclophosphazene. The structures of the compounds were characterized by NMR (31P, 1H, 13C-APT and HETCOR) and MALDI-TOF MS spectroscopic techniques and the structures of the compounds were confirmed. Furthermore, single crystal X-ray analysis and theoretical calculations were performed to confirm the structure of the molecules. Single crystal X-ray analyses of DPP-Et-Sand-Et and DPP-Sand-Me-Me compounds were performed. A detailed study of the crystal packing arrangement of the DPP-Et-Kum-Et compound crystallized in the P21/n monoclinic space group revealed the presence of stacking interactions between the non-planar conjugated benzene rings of coumarins and diphenyl groups attached to the phosphazene ring. The crystal structure of the DPP-Kum-Me-Me compound is mainly based on classical C-H---O intermolecular hydrogen bonding interactions with an average distance of 2.52 Å. UV absorbance, fluorescence emission, quantum yield and lifetime measurements were performed to determine the optical properties. The activation energies of DPP-Et-Kum-Et and DPP-Kum-Et compounds, which have the lowest band gaps in the theoretical calculations (4.31 eV and 4.30 eV, respectively), were determined with an impedance analyzer using dc conductivity values measured at different temperatures. The calculated activation energies for DPP-Et-Kum-Et and DPP-Kum-Et were found to be 104.49 and 100.92 meV, respectively. The DPP-Kum-Et compound was found to have the lowest conductivity. The results show that both theoretical and experimental calculations are in agreement with each other. The theoretical calculations for the compounds are in close agreement with the experimental data.