A π-orbital model to study substituent effects in organic room-temperature phosphorescent materials. Issue 24 (10th June 2022)

• Record Type: Journal Article
• Authors: Gong, Wenqi; Qin, Ke; Yao, Xiaokang; Li, Qiuying; Lv, Anqi; Ye, Wenpeng; Shi, Huifang; An, Zhongfu; Ma, Huili
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 24(2022)
• Page Start: 9319
• Page End: 9325
• Publication Date: 2022-06-10
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc01716d
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A π-orbital model, converting (n, π*) to (π, π*) by raising the π-orbital energy level, was built to reveal the changes in room-temperature phosphorescence (RTP) efficiency and lifetime of organic materials caused by electron-donating groups (EDGs). Abstract : The substituent effect is a ubiquitous tool to improve the room temperature phosphorescence (RTP) of organic materials, but it remains unclear as to how to rationally manipulate the RTP performance. However, we establish a π-orbital model to unravel the substituent effect on the organic RTP materials, by using the hybrid quantum mechanics/molecular mechanics (QM/MM) model and N-Electron Valence State Perturbation Theory (NEVPT2). With the substitution of electron-donating groups (EDGs), the increase of the π-orbital energy level separates the hybrid or adjacent n/π-orbitals, converting S1 from (n, π*) to (π, π*) that produces the T n -dependent intersystem crossing process, accounting for the diverse RTP efficiency caused by EDGs. Moreover, this change also transforms T1 (n, π*) to T1 (π, π*), suppressing the nonradiative relaxation of triplet excitons, thereby prolonging the RTP lifetime. Experimental validation was further performed for the predicted organic RTP molecule based on the π-orbital model. This model provides new guidelines to manipulate the RTP performance in organic materials.