Strategies for Design of Potential Singlet Fission Chromophores Utilizing a Combination of Ground-State and Excited-State Aromaticity Rules
Strategies for Design of Potential Singlet Fission Chromophores Utilizing a Combination of Ground-State and Excited-State Aromaticity Rules
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DOI：
10.1021/jacs.9b12435
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发表时间：
2020-03-25
影响因子：
15
通讯作者：
Ottosson, Henrik
中科院分区：
文献类型：
--
作者：
El Bakouri, Ouissam;Smith, Joshua R.;Ottosson, Henrik
单重态激子裂变光伏技术需要具有最低激发态的发色团，其排列方式为2 E（T-1）< E（S-1）和E（S-1）< E（T-2）。在此，定性理论和量子化学计算用于开发明确的策略，如何使用贝尔德的4 n规则的激发态芳香性，结合休克尔的4 n + 2规则的基态芳香性，以定制新的潜在的生色团的单线态裂变。首先，我们分析了E（T-1），E（S-1），和E（T-2）的苯和环丁二烯（CBD）作为激发态反芳香族和芳香族原型，分别，并揭示CBD满足的标准，对一个单线态裂变发色团的状态排序。然后，我们看看富烯，一类化合物，可以通过选择取代基从贝尔德-反芳族到贝尔德-芳族的T-1和S-1和从休克尔-芳族到休克尔-反芳族的S-0。大多数取代富烯（159/225）的T-1和S-1态由单激发HOMO -> LUMO构型描述，为E（T-1）和E（S-1）沿着近似（反）芳香性坐标同时调谐提供了理论依据.可调谐性的关键是交换积分（K-H，K-L），其理想地在整个化合物类中是恒定的，提供常数E（S-1 - T-1）。这导致我们的几何模型用于识别单线态裂变发色团，我们探索什么因素限制了模型。在苯并稠合的4 n电子化合物类别和噻咯中鉴定出具有类似于1 eV或更高的计算E（T-1）值的候选物。简而言之，它是澄清如何联合利用贝尔德的4 n和休克尔的4 n + 2规则，连同取代基效应（电子和空间位阻）和benzannephrase，可以用来定制新的生色团与潜在的用途在单重态裂变photophrics。
Singlet exciton fission photovoltaic technology requires chromophores with their lowest excited states arranged so that 2E(T-1) < E(S-1) and E(S-1) < E(T-2). Herein, qualitative theory and quantum chemical calculations are used to develop explicit strategies on how to use Baird's 4n rule on excited-state aromaticity, combined with Huckel's 4n + 2 rule for ground-state aromaticity, to tailor new potential chromophores for singlet fission. We first analyze the E(T-1), E(S-1), and E(T-2) of benzene and cyclobutadiene (CBD) as excited-state antiaromatic and aromatic archetypes, respectively, and reveal that CBD fulfills the criteria on the state ordering for a singlet fission chromophore. We then look at fulvenes, a class of compounds that can be tuned by choice of substituents from Baird-antiaromatic to Baird-aromatic in T-1 and S-1 and from Huckel-aromatic to Huckel-antiaromatic in S-0. The T-1 and S-1 states of most substituted fulvenes (159 of 225) are described by singly excited HOMO -> LUMO configurations, providing a rational for the simultaneous tuning of E(T-1) and E(S-1) along an approximate (anti)aromaticity coordinate. Key to the tunability is the exchange integral (K-H,K-L), which ideally is constant throughout the compound class, providing a constant.E(S-1 - T-1). This leads us to a geometric model for the identification of singlet fission chromophores, and we explore what factors limit the model. Candidates with calculated E(T-1) values of similar to 1 eV or higher are identified among benzannelated 4npelectron compound classes and siloles. In brief, it is clarified how the joint utilization of Baird's 4n and Huckel's 4n + 2 rules, together with substituent effects (electronic and steric) and benzannelation, can be used to tailor new chromophores with potential use in singlet fission photovoltaics.