Vibronic properties of organic semiconductors based on phthalocyanine complexes with asymmetrically distributed electron density

This study is concerned with the optical properties of organic semiconductors based on lanthanide (III) biphthalocyanine and triphthalocyanine complexes with asymmetrically distributed electron density. The $^{\mathrm{Cl}}$PcLu$^{\mathrm{tBu}}$Pc biphthalocyanine and $^{\mathrm{Cl}}$PcEu$^{\mathrm{Bu}}$PcLu$^{\mathrm{Bu}}$Pc triphthalocyanine solid films ($^{\mathrm{Cl}}$Pc = 2, 3, 9, 10, 16, 17, 23, 24-octachlorophthalocyaninate, $^{\mathrm{tBu}}$Pc = 2(3), 9(10), 16(17), 23(24)-tetra- tretbutylphthalocyani-nate, $^{\mathrm{Bu}}$Pc = 2, 3, 9, 10, 16, 17, 23, 24-octabutylphthalo cyaninate) are fabricated, and their transmittance spectra in the middle infrared region are studied. Analysis of the transmittance spectra shows that the addition of complexity to phthalocyanine molecules yields some changes in the spectra. Specifically, the isoindole group can exhibit vibronic properties in the form of four absorption lines in the range 1400–1450 cm$^{-1}$. New absorption lines that may be due to chlorine-carbon bonds are observed in the far-infrared region.