Electronic structure and photophysics of (CC)tetra-p-tolylporphyrin2+

Abstract

The electronic structure and photophysical properties of (CC)TTP²⁺ (TTP = tetra-p-tolylporphyrin) were scrutinized by using quantum mechanical calculations and transient absorption spectroscopic measurements. When compared to a metalloporphyrin, the presence of the CC unit in (CC)TTP²⁺ causes a splitting of the degenerate LUMO and a large decrease in the HOMO–LUMO gap, while the 2+ charge and tolyl groups lead to additional charge-transfer-like transitions in the visible absorption spectrum. The small HOMO–LUMO gap and ruffled structure lead to a very short excited-state lifetime of 10 ± 0.3 ps.