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oai:figshare.com:article/34046328 2026-10-01T14:23:45Z category_1 category_4 category_915 category_14 category_21 category_24 category_873 category_64 portal_63 item_type_6 month_year_10_2026

Substituent and Hydrostatic Pressure Regulation of Triplet Exciton Dynamics in Organic Room-Temperature Phosphorescent Crystals Yan Wang (15435) Huanling Liu (17698555) Yuzhi Song (8910383) Lili Lin (451927) Xiuneng Song (25156977) Chuan-Kui Wang (1764907) Jianzhong Fan (3349673) Biophysics Biochemistry Physical Sciences not elsewhere classified Molecular Biology Biotechnology Evolutionary Biology Chemical Sciences not elsewhere classified Cancer π orbital mixing weakened excitonic coupling strong intermolecular confinement severe structural relaxation providing new insights induced orbital reconstruction frontier orbital compositions triplet exciton dynamics state structural relaxation state geometry leads state calculations combined reconstructs intermolecular packing localized triplet excitons favorable triplet utilization level design principle employ multiscale excited based molecular crystals 0 </ sub hydrostatic pressure regulation triplet excitons state structure rational design level simulations hydrostatic compression efficient utilization three phenothiazine thereby controlling organic room molecular substitution microscopic origin materials rely flexible excited findings establish enhanced n energy gap emission evolution crystal packing 471 nm Organic room temperature phosphorescence (RTP) materials rely on efficient utilization of triplet excitons, yet the microscopic relationship among molecular distortion, crystal packing, and triplet decay dynamics remains insufficiently understood. Herein, we employ multiscale excited-state calculations combined with crystal-level simulations to elucidate how molecular substitution and hydrostatic pressure regulate RTP properties in three phenothiazine-based molecular crystals (MM-HPT, MH-MPT, and MM-MPT). We demonstrate that methyl substitution induces progressive conformational distortion, which reconstructs intermolecular packing and frontier orbital compositions, thereby controlling the competition between radiative and non-radiative triplet decay pathways. Although MH-MPT exhibits the strongest spin–orbit coupling and the largest phosphorescence radiative rate due to enhanced n-π orbital mixing and localized triplet excitons, its flexible excited-state geometry leads to severe structural relaxation and accelerated non-radiative decay. In contrast, MM-MPT achieves more favorable triplet utilization by rigidifying the excited-state structure through strong intermolecular confinement, resulting in suppressed non-radiative losses. Furthermore, hydrostatic compression of MM-HPT continuously reduces excited-state structural relaxation and enlarges the T₁-S₀ energy gap, producing a pronounced phosphorescence hypsochromic shift from 528 to 471 nm. Pressure-induced orbital reconstruction and weakened excitonic coupling further reveal the microscopic origin of the emission evolution. These findings establish a molecular-level design principle that efficient RTP emission requires balancing triplet generation, radiative transition, and structural relaxation suppression rather than simply enhancing spin–orbit coupling, providing new insights into the rational design of stimulus-responsive organic phosphorescent materials. 2026-10-01T00:00:00Z Text Journal contribution 10.1021/acs.jpca.6c05633.s001 https://figshare.com/articles/journal_contribution/Substituent_and_Hydrostatic_Pressure_Regulation_of_Triplet_Exciton_Dynamics_in_Organic_Room-Temperature_Phosphorescent_Crystals/34046328 CC BY-NC 4.0