Five-membered rings as diazo components in optical data storage devices: an ab initio investigation of the lowest singlet excitation energies

The two lowest singlet excitation energies of 18 azo dyes have been studied by ab initio quantum-chemical methods within the second-order polarization propagator approximation (SOPPA). Various combinations of five-membered rings (furan, thiophene, pyrrole, oxazole, thiazole, and imidazole) have been investigated as diazo components for a potential use in optical data storage materials. It is found that the diazo compounds with two heterocyclic five-membered rings have π→π∗ excitation energies corresponding to laser wavelengths in the region 450–500 nm whereas one five-membered ring and a phenyl group as diazo components results in wavelengths in the region 400–435 nm.