Molecular structure–spectroscopic property relationships in a series of transition metal-containing phenylacetylene oligomers

To develop novel nonlinear dyes for photonic applications, we synthesized a series of transition metal-containing phenylacetylene oligomers. The optical properties of these compounds were measured by UV/Vis, fluorescence, long-pathlength UV/Vis and nanosecond flash photolysis experiments. The sensitivity of the state energies to molecular size was a measure of their delocalization. The S0 and T1 states were found to be more localized than the S1 and Tn states. The results were consistent with the S0→S1 and T1→Tn transitions having charge transfer character, while the T1→S0 transition was from a confined state to another confined state.