Design of Small Intramolecular Singlet Fission Chromophores: An Azaborine Candidate and General Small Size Effects

Abstract

We report the first attempt to design small intramolecular singlet fission chromophores, with the aid of quantum chemistry and explicitly simulating the time evolution of state populations using quantum dynamics method. We start with three previously proposed azaborine-substituted intermolecular singlet fission chromophores. Through analyzing their frontier orbital amplitudes, we select a BN-substituted azulene as the building block. Covalently connecting two such monomers and tuning their relative configuration, we examine three dimers. One dimer is found to be an eminent candidate: the triplet-pair state is quickly formed within 1 ps, and the two triplets are ready to be disentangled. We elucidate the general small size effects in intramolecular singlet fission and focus on specific aspects which should be taken care of when manipulating the fission rate through steric hindrance.

Rational design of doubly-bridged chromophores for singlet fission and triplet–triplet annihilation

“…[60][61][62] The energy correction on TT state, DE TT , was considered in the previous study on SF. 58 The couplings V FE-TT and V FE-TT 0 represent one-electron contributions to the electronic coupling concerning SF and maybe TTA, and contribute to determining the SF rate 2,19,31,32,43,52,56,63 because they correspond to the off-diagonal part connecting the FE and TT states. In order to estimate an approximate energy balance between the FE and TT states aer the perturbation through the CT states, we dened the effective energy difference between them, 58 (…”

“…The case (I-PN) may be a good way to design weak coupling system, which could lead to slow but high-yield SF and/or TTA systems. 47,52,56,63 The lowest lying state can keep its electronic character from strong mixing with other states due to small electronic couplings from the view point of electronic conguration. At the same time, small electronic couplings, however, would suppress the transition rate between the FE and TT states, and could lead to deactivation pathways for the system before undergoing SF or TTA.…”

“…15,19,22,[34][35][36][37][38][39][40] As another way of controlling electronic coupling, the use of covalently-linked systems is promising because the electronic coupling can be designed at the molecular level. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] In the previous study, we proposed several ways of tuning electronic coupling concerning SF based on the quantum interference. 52 We observed that covalently-linked systems with constructive quantum interference induce faster SF than those with destructive quantum interference.…”

Quantum Master Equation Approach to Singlet Fission Dynamics in Pentacene Linear Aggregate Models: Size Dependences of Excitonic Coupling Effects

“…Namely, in addition to the energy level matching conditions in step (i), design of intermolecular configuration (crystal packing) is found to be indispensable for describing the SF rate, which is proportional to transition probability from FE to TT state. [5,6] Another essential factor for determining the SF efficiency is involved in the exciton dynamics with vibronic couplings, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] which is the main topic in step (iii). In step (iii), various results obtained in steps (i) and (ii) are combined and are mutually correlated with the exciton dynamics caused by vibronic couplings.…”

Intermolecular Singlet Fission in Unsymmetrical Derivatives of Pentacene in Solution

“…Only (TIPS) 2 ‐Pn revealed vibrationally well‐resolved absorption spectra. This is in stark contrast to TIPS‐Pn‐H and TIPS‐Pn‐Me , for which spectral broadening goes hand‐in‐hand with the loss of vibrational fine structure (Figure S11, Supporting Information) …”