Odonkor Gideon, Odoh Samuel O
Department of Chemistry, University of Nevada, Reno, Nevada, USA.
Department of Chemistry, University of Nevada Reno, Reno, Nevada, USA.
J Comput Chem. 2025 Mar 30;46(8):e70090. doi: 10.1002/jcc.70090.
Computational investigations of Inverted Singlet-Triplet (INVEST) emitters often rely on ADC(2) and TD-DFT excitation energies (EEs) obtained with the vertical approximation. Here, we first considered several cyclazine derivatives and examine the sensitivity of vertical EEs (VEEs) as well as singlet-triplet gaps, ΔE gaps, to the level at which the ground state (S) structure was optimized. For cyclazine, VEEs and vertical gaps from ADC(2) or TD-DFT are spread over a narrow range (< 0.064 eV) whether the S structure is optimized with various DFT, CCSD, and RI-MP2 methods. However, for asymmetric cyclazines, depending on the protocol for optimizing S structures, not only are VEEs spread over a substantially wider range (up to 0.75 eV) but so are vertical ΔE gaps (up to 0.30 eV), leading to cases where, with different S structures, one obtains positive vertical ΔE gaps or significantly negative gaps. We relate this behavior to the introduction of significant asymmetry and bond-length variations in the cyclazine derivatives, formed by ligand functionalization or modification of the cyclazine core. On a more positive note, adiabatic EEs (AEEs) and adiabatic ΔE gaps display significantly lower sensitivity (7-30× less) to the geometry optimization protocols than their vertical analogs. Crucially, for cyclazine, the M06-HF functional with 100% non-local exchange provides the closest S geometry to available CCSD(T) data. We show that this effect exists also for other frameworks (e.g., azulene, pentaazaphenalene, and non-alternant polycyclic hydrocarbons) that have been considered for the INVEST property, with VEEs spread over a broader range of up to 1.19 eV and vertical ΔE gaps over a range of 0.62 eV. For INVEST emitters, it is therefore extremely important to judiciously choose the computational protocol for optimizing ground state geometries, in computing VEEs and vertical ΔE gaps.
对反向单重态 - 三重态（INVEST）发光体的计算研究通常依赖于通过垂直近似获得的ADC(2)和TD - DFT激发能（EEs）。在此，我们首先考虑了几种环嗪衍生物，并研究了垂直激发能（VEEs）以及单重态 - 三重态能隙（ΔE能隙）对基态（S）结构优化水平的敏感性。对于环嗪，无论S结构是用各种DFT、CCSD和RI - MP2方法进行优化，ADC(2)或TD - DFT的VEEs和垂直能隙都分布在较窄的范围内（< 0.064 eV）。然而，对于不对称环嗪，根据优化S结构的方案，不仅VEEs分布在实质上更宽的范围内（高达0.75 eV），垂直ΔE能隙也是如此（高达0.30 eV），导致在不同S结构的情况下，会得到正的垂直ΔE能隙或显著为负的能隙。我们将这种行为与环嗪衍生物中由于配体功能化或环嗪核心修饰而形成的显著不对称性和键长变化联系起来。更积极的是，绝热激发能（AEEs）和绝热ΔE能隙对几何优化方案的敏感性比其垂直类似物显著更低（低7 - 30倍）。至关重要的是，对于环嗪，具有100%非局部交换的M06 - HF泛函提供了与可用的CCSD(T)数据最接近的S几何结构。我们表明，对于其他已被考虑具有INVEST性质的框架（如薁、五氮杂菲和非交替多环烃）也存在这种效应，VEEs分布在高达1.19 eV的更宽范围内，垂直ΔE能隙分布在0.62 eV的范围内。因此，对于INVEST发光体，在计算VEEs和垂直ΔE能隙时，明智地选择优化基态几何结构的计算方案极其重要。
