Influence of heavy central atom on photoelectric, nonlinear optical, and photorefractive properties of metal phthalocyanines

Measurement of the photoelectric and photorefractive characteristics of 2,3,9,10,16,17,23,24-tetra(15-crown-5)phthalocyaninatoacetatoyttrium(III) [(15C5)4Pc]Y(OAc) has made it possible to reliably establish the features of decrease in the quantum yield of generation of charge carriers φ0 and photorefractive two-beam coupling gain Γ with an increase in the atomic weight of the central metal in a series of related gallium(III), yttrium(III), ruthenium(II), and indium (III) phthalocyaninates. These features can be due to an increase in the spin-orbit interaction constant with increasing atomic weight of the central metal, a change that leads to an increase in both the contribution of triplet excited associates to the formation of mobile charge carriers and the rate of the reverse reaction T1 → S0, which effectively inhibits the formation of charge carriers through the excited triplet state. The measurement of photoelectric and photorefractive characteristics at 1064 nm has shown that the quantum yield of electron-hole pairs in the composite polyvinylcarbazole/supramolecular assemblies of yttrium complex is φ0 = 0.6 and the two-beam coupling gain coefficient Γ is about 35 cm−1 at E0 = 120 V/μm. The dielectric susceptibility measured by the z-scan technique in a solution of the yttrium complex in tetrachloroethane (1 mg in 1 mL) is χ(3) = 4.2 × 10−10 esu.