Chirality-Dependent Modulation of Organic-Inorganic Interaction and Exciton Response in 2D Perovskites under Pressure

High Resolution Image Download MS PowerPoint Slide We investigate how chirality influences the excitonic response to pressure in chiral versus racemic (Cl-methylbenzylammonium) 2 PbI 4 . Above 4 GPa, we observe a reduction of the exciton redshift rate in the chiral samples compared to the racemate, a behavior paralleling the evolution of the N−H vibrational modes in the infrared spectrum. We hypothesize that, at 4 GPa, the asymmetric N−H⋯I bonding network in the chiral systems reaches the limit of its buffering capability. Further compression is then accommodated through octahedral distortion, enhancing the chiral character of the inorganic sublattice. The corresponding modification of the octahedral angles reduces Pb-s/I-p orbital coupling, explaining the decrease in the exciton redshift rate. Conversely, the symmetric N−H⋯I bonds in the racemate prove more effective at accommodating compression without altering the octahedral orientation. Our results demonstrate that chirality governs the tunability of both organic−inorganic interactions and the excitonic response under external stimuli in two-dimensional perovskites.