Department of Chemistry, University of Colorado, Boulder, CO 80309-0215, USA.
Photochem Photobiol Sci. 2019 Sep 1;18(9):2112-2124. doi: 10.1039/c9pp00283a. Epub 2019 Aug 29.
A simplified version of the frontier orbital model has been applied to pairs of C, C, C, and C symmetry 1,3-diphenylisobenzofuran rotamers to determine their best packing for fast singlet fission (SF). For each rotamer the square of the electronic matrix element for SF was calculated at 2.2 × 10 pair geometries and a few thousand most significant physically accessible local maxima were identified in the six-dimensional space of mutual arrangements. At these pair geometries, SF energy balance was evaluated, relative SF rate constants were approximated using Marcus theory, and the SF rate constant k was maximized by further optimization of the geometry of the molecular pair. The process resulted in 142, 67, 214, and 291 unique geometries for the C, C, C, and C symmetry molecular pairs, respectively, predicted to be superior to the C symmetrized known crystal pair structure. These optimized pair geometries and their triplet biexciton binding energies are reported as targets for crystal engineering and/or covalent dimer synthesis, and as possible starting points for high-level pair geometry optimizations.
已将简化的前沿轨道模型应用于 C、C、C 和 C 对称的 1,3-二苯基异苯并呋喃旋光异构体对，以确定它们在快速单重态裂变 (SF) 中的最佳堆积方式。对于每个旋光异构体，在 2.2×10 对几何结构中计算了 SF 的电子矩阵元的平方，并在六维的相互排列空间中确定了几千个最重要的物理可及局部最大值。在这些对几何结构中，评估了 SF 的能量平衡，使用 Marcus 理论近似了相对 SF 速率常数，并通过进一步优化分子对的几何形状来最大化 SF 速率常数 k。该过程分别为 C、C、C 和 C 对称分子对产生了 142、67、214 和 291 个独特的几何结构，预测优于 C 对称的已知晶体对结构。这些优化的对几何结构及其三重态双激子结合能被报告为晶体工程和/或共价二聚体合成的目标，以及高水平对几何优化的可能起点。
