{"title":"Polymorphism Controlled Singlet Fission in TIPS-Anthracene: Role of Stacking Orientation","authors":"Kalishankar Bhattacharyya, Ayan Datta*","doi":"10.1021/acs.jpcc.6b10075","DOIUrl":null,"url":null,"abstract":"<p >Generation of multiple triplet excitons from one singlet exciton (singlet fission, SF) has been reported in several organic molecules recently. The overall SF yield in such molecular materials, however, is controlled by polymorphism in organic semiconductors through noncovalent interactions like van der Waals and weak electrostatic interactions. In this article, we demonstrate how SF is strongly perturbed by even small variations in molecular packing for polymorphic crystals of triisopropylsilyethnyl-anthracene derivatives, TIPS-Ant (<b>PI</b> and <b>PII</b>). Based on quantum chemical calculations, SF dynamics have been computed for both <b>PI</b> and <b>PII</b> polymorphs. <b>PI</b> and <b>PII</b> differ in their intermolecular π···π stacking patterns, which eventually control their electronic properties. Using the incoherent hopping model for the crystals, we computed SF rate through the Marcus electron transfer theory. For both <b>PI</b> and <b>PII</b>, the direct two-electron pathway predominates over the charge-transfer (CT) mediated mechanism. <b>PII</b> has higher triplet yield (~196%) compared to <b>PI</b> (~178%). Both time-dependent DFT as well as Weller equation reveal that the charge transfer (CT) state is a high energy state, and hence, CT mediated SF barely influences triplet yield. Interplay of the local excitation (LE), multiple excitation (ME), and correlated triplet (T<sub>1</sub>T<sub>1</sub>) energy levels controlled the overall exciton dynamics/diffusion in TIPS-Ant polymorphs. Polymorphism is shown to be a key factor for the rational design of optimal SF in polyaromatic hydrocarbons (PAH).</p>","PeriodicalId":61,"journal":{"name":"The Journal of Physical Chemistry C","volume":"121 3","pages":"1412–1420"},"PeriodicalIF":3.2000,"publicationDate":"2017-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1021/acs.jpcc.6b10075","citationCount":"50","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Journal of Physical Chemistry C","FirstCategoryId":"1","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.jpcc.6b10075","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 50
Abstract
Generation of multiple triplet excitons from one singlet exciton (singlet fission, SF) has been reported in several organic molecules recently. The overall SF yield in such molecular materials, however, is controlled by polymorphism in organic semiconductors through noncovalent interactions like van der Waals and weak electrostatic interactions. In this article, we demonstrate how SF is strongly perturbed by even small variations in molecular packing for polymorphic crystals of triisopropylsilyethnyl-anthracene derivatives, TIPS-Ant (PI and PII). Based on quantum chemical calculations, SF dynamics have been computed for both PI and PII polymorphs. PI and PII differ in their intermolecular π···π stacking patterns, which eventually control their electronic properties. Using the incoherent hopping model for the crystals, we computed SF rate through the Marcus electron transfer theory. For both PI and PII, the direct two-electron pathway predominates over the charge-transfer (CT) mediated mechanism. PII has higher triplet yield (~196%) compared to PI (~178%). Both time-dependent DFT as well as Weller equation reveal that the charge transfer (CT) state is a high energy state, and hence, CT mediated SF barely influences triplet yield. Interplay of the local excitation (LE), multiple excitation (ME), and correlated triplet (T1T1) energy levels controlled the overall exciton dynamics/diffusion in TIPS-Ant polymorphs. Polymorphism is shown to be a key factor for the rational design of optimal SF in polyaromatic hydrocarbons (PAH).
期刊介绍:
The Journal of Physical Chemistry A/B/C is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and chemical physicists.