Nanographene-Doped Chalcone Derivatives of Dioxybiphenyl-Bridged Dispirocyclotriphosphazenes: Synthesis, Electrical Properties, and DFT Calculations

The cyclotriphosphazenes, which constitute an important class of inorganic compounds, can show new properties in the medical or technological fields depending on the properties of the substituted organic/inorganic groups. Herein, we aimed to determine electrical and theoretical properties of the nanographene-doped chalcone derivatives of dioxybiphenyl-bridged dispiro-cyclotriphosphazenes. For this aim, a new series of chalcone substituted spiro-cyclotriphosphazenes (3 a-g) have been synthesized by the reaction of dioxybiphenyl-bridged dispiro-cyclotriphosphazene (3) with chalcone derivatives (1 a-g), respectively. Then, nanographene was doped to these spiro-cyclotriphosphazene 3 a-g using a hydrothermal system. The dielectric constant and loss factor of 4 % graphene-doped chalcone-substituted spiro-cyclotriphosphazene 3 g were determined as 167 and 2147 at 1 kHz, respectively, showing a significant increase compared to compound 3 g. The energy values of HOMO and LUMO orbitals are computed using DFT theory's level of B3LYP/6-31G(d,p). The FMO's energy gap values for 3 a-g were found to be 7.92, 3.48, 3.26, 3.33, 3.53, 4.03 and 3.75 eV, respectively. Especially at frequencies below 10 kHz, the most striking result was observed for the nanographene-doped 3 d. While the AC conductivity of 3 d at 1 kHz was 3.87x10(-9) S cm(-1), the conductivity of the graphene-doped 3 d was calculated as 5.00x10(-6) S cm(-1). In addition, DC conductivity measurements were completed as a function of temperature and linearly increasing graphs were obtained with temperature. The activation energies calculated from the slopes of these graphs were 0.293, 0.305, 0.364 and 0.920 eV for 3 c, 3 d, 3 e and 3 g, respectively.