Substituent effects on the excited states of phenyl-capped phenylene vinylene tetramers

The singlet and triplet excited states of phenyl-capped tetramers of phenylene vinylene with different alkyl, alkoxy or cyano substituents, were investigated in benzene solution. The lowest singlet states were studied by laser flash-photolysis with time-resolved microwave conductivity and flourescence. The triplets were generated by pulse radiolysis, via energy transfer from the solvent excited singlet followed by inter-system crossing or by energy transfer from the naphthalene triplet. Their absorption spectra and rates of quenching by oxygen were determined