Viable access to the triplet excited state in peryleneimide based palladium complex $$^{\S }$$ §

Abstract

Triplet excited state in organic chromophores is ubiquitously significant owing to its utility in light harvesting and photovoltaic device applications. Herein, we report the enhancement in the triplet character of an innately triplet deficient peryleneimide chromophore via incorporation of a heavy atom. Palladium incorporated perylenemonoimide (PMI-Pd) was synthesized via oxidative addition of PMI-Br into Pd(0) under inert experimental conditions. The structural sanctity of the PMI-Pd and the model derivative PMI was characterized via single crystal X-ray diffraction and the close-packing was examined employing Hirshfeld surface analysis. The steady-state spectroscopic measurements of PMI-Pd in chloroform reveal an apparent perturbation in the UV-Vis absorption, fluorescence emission and lifetime characteristics. A much higher perturbation is observed in the ultrafast photoexcited processes of PMI-Pd in chloroform as envisaged via nanosecond transient absorption (nTA) measurements. The nTA measurements of PMI-Pd in chloroform reveal a significant enhancement in the triplet character of PMI-Pd as compared to the model derivative PMI. Spin-orbit coupling (SOC) mediated triplet enhancement in PMI-Pd suggest heavy atom incorporation as a viable route for accessing the triplet excited states in triplet deficient aromatic chromophores. SOC mediated triplet enhancement in innately triplet deficient organic chromophores can revive the utility of these materials for novel photovoltaic and energy storage applications.