Lasing in Crystals Based on 7‐Azaindole‐Phenylhydrazone Organoboron Compounds

Abstract The development of efficient organic solid‐state lasers requires an in‐depth understanding between chemical structure, intermolecular interactions in the crystal phase, and optical and electronic properties. This study highlights these closed dependencies in novel 7‐azaindole phenylhydrazone derivatives and their corresponding boron complexes, by deploying a combined approach of experimental techniques and theoretical calculations (Density Functional Theory and Time‐Dependent Density Functional Theory) in the solvated and solid‐state phase. Notably, it is found that when these compounds, which are weakly emissive in solution, are processed into crystalline microfibers, they experience a sharp emission enhancement and exhibit laser action at low pump fluence thresholds. This is achieved by partially inhibiting structural relaxation, which drives non‐radiative decay, a critical factor for effective lasing, highlighting the potential of these materials for future optoelectronic applications.