Photoconductive properties of a mesogenic long-chain tetraphenylporphyrin oxovanadium(IV) complex

The photoconductive properties of a mesogenic long-chain tetraphenylporphyr in, 5,10,15,20-tetrakis(4-n-pentadecylphenyl)porphinatooxovanadium(IV) were investigated and compared with those of the metal-free compound for a symm etrical sandwich-type ITO cell. This compound shows two types of lamellar m esophases (M-LC and M-L phases) and the phase transition sequence is Cr 51 M-LC 83 M-L 140 Iso. A similar photocurrent rectification behavior to the c orresponding metal-free tetraphenylporphyrin mesogen was shown. However, th e observed photocurrent was remarkably larger than that of the metal-free c ompound for all phases. The action spectra and the temperature dependence o f the dark- and photocurrents were also investigated on the mesomorphic pha se transition behavior. These results imply that the photoconductive proper ty of mesogenic tetraphenylporphyrin-based compounds could be drastically a ffected by a change of molecular fluctuation and long-range order through m esomorphic phase transitions and a metal species inserted in the central co re. (C) 2001 Elsevier Science B.V. All rights reserved.