Relative energies among S3 intermediates in the photosystem II revealed by DLPNO coupled cluster and hybrid DFT calculations. Possible pathways of water insertion in the S2 to S3 transition

• Published in: Chemical physics letters 2022-04, Vol.793, p.139439, Article 139439
• Main Authors: Miyagawa, Koichi, Shoji, Mitsuo, Isobe, Hiroshi, Kawakami, Takashi, Nakajima, Takahito, Yamaguchi, Kizashi
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2022.139439

[Display omitted] •The relative stability of various S3 intermediates with Mn(IV)4 valence for CaMn4O6 cluster of OEC of PSII were investigated by hybrid DFT and DLPNO-CC calculations.•Interpretation of the intermediate spin states of the S3 state were performed by the exact diagonalization of spin Hamiltonian.•The computational results indicated nearly degeneracy and stability among right and left opened hydroxide intermediates. DLPNO-CCSD(T0) calculations coupled with the exact diagonalization of spin Hamiltonian matrix elucidated two right (R)-opened hydroxide (OH–)-inserted structures with the intermediate spin (IS) (S = 3), left (L)-opened OH– and water-inserted structures with IS (S = 3) and left (L)-opened oxo-inserted structures with the high spin (HS) (S = 6) state. Multiple intermediates in the S3 state revealed by DLPNO-CCSD(T0) are compatible with the EPR and XFEL results for the S3 state of photosystem II.