Prolonged Lifetime of Near-IR Emission due to a Reservoir State in a Phenylene-linked Copper(II) Porphyrin–Zinc(II) Porphyrin Dimer

A phenylene-linked copper(II) porphyrin–zinc(II) porphyrin dimer exhibits near-IR emission, the lifetime of which is 310 ns at 300 K in toluene. Based on transient absorption measurements and emission temperature dependence, the observed emission was ascribed to phosphorescence from the trip-doublet state of copper porphyrin, which is thermally activated with an energy gap of 430 cm−1 from the zinc(II) porphyrin triplet state. The zinc–porphyrin triplet state acts as a reservoir and emission lifetime of the dimer is prolonged by ten times compared to the copper–porphyrin monomer, of which the lifetime is 30 ns.