2024-03-28T16:18:20Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/666402022-11-17T02:08:08Zhdl_2115_20059hdl_2115_151A DFT and multi-configurational perturbation theory study on O-2 binding to a model heme compound via the spin-change barrierKitagawa, Y.Chen, Y.Nakatani, NaokiNakayama, AkiraHasegawa, Jun-ya431Dioxygen binding to a model heme compound via intersystem crossing (ISC) was investigated with a multi-state multi-configurational self-consistent field method with second-order perturbation theory (MS-CASPT2) and density functional theory (DFT) calculations. In elongated Fe-O distances, the energy levels of the S-0 and T-1 states are separated, which decreases the probability of intersystem crossing in these structures. At the DFT(B97D) level of calculation, the Fe-O distances of the S-0 and T-1 states were 1.91 and 2.92 angstrom, respectively. The minimum energy intersystem crossing point (MEISCP) was located as a transition state at a Fe-O distance of 2.17 angstrom with an energy barrier of 1.0 kcal mol(-1) from the T-1 minimum. The result was verified with MS-CASPT2 calculations including the spin-orbit interaction which also showed the intersystem crossing point at a Fe-O distance of 2.05 angstrom. An energy decomposition analysis on the reaction coordinate showed the important contribution of the ring-shrinking mode of the porphyrin ring, indicating that the reaction coordinates which control the relative energy level of the spin-states play a key role in intersystem crossing.Royal Society of ChemistryJournal Articleapplication/pdfhttp://hdl.handle.net/2115/66640https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/66640/1/MS3a_R1.pdf1463-9076Physical chemistry chemical physics182718137181442016-07-21enginfo:pmid/27328181info:doi/10.1039/c6cp02329kauthor