Absorption Spectra Of Phthalocyanine Research Articles

Stark effect on holes in the absorption spectra of phthalocyanine and the aluminum-phthalocyanine complex in polymer matrices

The effect of an external electric field on narrow spectral holes in S1←S0 absorption bands of molecules of free-base phthalocyanine and its complex with Al in polyvinyl butyral films at 4.2 K was studied. It was found that the average values of the change in the electric dipole moment due to phototransitions in the free-base phthalocyanine and its complex amount to 0.135 and 0.145 D, respectively. Both these values considerably exceed the relevant values for phthalocyanine complexes with Zn and Mg in the same matrix. Possible causes of the observed effects are discussed. Most probably, they are related to the differences in the structure of the central part of phthalocyanine-type molecules.

Calculation of the structure and absorption spectra of phthalocyanines in the gas-phase and in solution

Ab initio calculations have been carried out on both gas-phase and solvated phthalocyanines in order to determine equilibrium structures, vibrational spectra, and electronic spectra. Density functional theory (DFT) optimized geometries have the expected symmetries of D 2h for free-base phthalocyanine, D 4h for copper phthalocyanine, and C 4v for tin phthalocyanine, whereas Hartree–Fock optimized geometries, which also include lead phthalocyanine, are slightly displaced from the expected symmetries. Both sets of optimized geometries agree reasonably well with the available experimental structures. Vibrational spectra, calculated by the Hartree–Fock method, are in partial agreement with measured spectra, whereas visible absorption spectra calculated using molecular geometries obtained at three different levels of theory (DFT, HF, and PM3) showed good agreement with the measured vapor-phase spectra in the Q-band, and using the DFT optimized geometry resulted in very good agreement with measurements in the B-band. The self-consistent reaction field method for including bulk solvent effects in HF calculations had a small, nearly negligible, effect on the molecular structure of SnPc, whereas the DFT/ cosmo solvation model yielded the predictable result of increasing the Sn–N bond length by pulling the Sn atom further out of the molecular plane.