Porphyrin complexes of transition metals with a large dipole moment as active components of new film electret materials

This paper presents the results of a systematic study aimed at searching for organometallic molecules with a large dipole moment in order to create new film electret materials. A number of porphyrin complexes of transition metals, titanium, and vanadium and also complexes with bismuth( iii ) iodide with an axial metal—oxygen bond were synthesized. The obtained compounds were identified by physicochemical methods (IR spectroscopy and X-ray photoelectron spectroscopy). The optimized geometry of the complexes, their vibrational spectra, dipole moments, and charge density distributions were evaluated by quantum chemical calculations. The Mulliken population analysis was performed. The maximum dipole moments were found for BiI etioporphyrin II (6.47 D) and BiI 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (3.87 D). The metal ion acts as a transmitter of electron density from nitrogen atoms to the counterion, resulting in an increase in the dipole moment of the molecule as a whole compared to the starting porphyrin ligands. The inclusion of porphyrin complexes under the action of an electric field resulted in the formation of polyvinyl acetate films. Copper layers 100 nm thick were deposited by magnetron sputtering onto both sides of these films. The dielectric properties and the temperature dependences of thermally stimulated depolarization currents of the obtained samples were studied. All samples were found to have a pronounced electret effect.