Crystal Lattice-Induced Stress modulates Photoinduced\nJahn–Teller Distortion Dynamics

Efficient photoredox\nchemical transformations are essential to\nthe development of novel, cost-effective, and environmentally friendly\nsynthetic methodologies. The concept of the entatic state in bioinorganic\ncatalysis proposes that a preorganized structural configuration can\nreduce the energy barriers associated with chemical reactions. This\nconcept provides one of the guiding principles to enhance catalytic\nefficiency by maintaining high-energy conformations close to the reaction’s\ntransition state. Copper(I)-based photocatalysts, recognized for their\nlow toxicity and highly negative oxidation potentials, are of particular\ninterest in entasis studies. In this study, we explore the impact\nof entasis caused by stress induced by the surrounding lattice on\nthe excited state dynamics of a prototypical copper(I)-based photocatalyst\nin a single crystal form. Using femtosecond broadband transient absorption\nspectroscopy, we show that triplet state formation from the entactic\nstate is faster (∼3.9 ps) in crystals compared with solution\n(∼11.3 ps). The observed faster intersystem crossing in crystals\nhints toward the possible existence of distorted square planar geometry\nwith higher spin–orbit coupling at the minima of the S<sub>1</sub> state. We further discuss the influence of entasis on vibrationally\ncoherent photoinduced Jahn–Teller distortions. Our findings\nreveal the photophysical properties of the copper complex under lattice-induced\nstress, which can be extended to enhance the broader applicability\nof the entatic state concept in other transition metal systems. Understanding\nhow environmental stress-induced geometric constraints within crystal\nlattices affect photochemical behavior opens avenues for designing\nmore efficient photocatalytic systems based on transition metals,\npotentially enhancing their applicability to sustainable chemical\nsynthesis.