title: Regulation mechanism of spin-orbit coupling in charge-transfer-induced luminescence of imidazopyrazinone derivatives.
abstract: The spin transition in the reactions of the derivatives of imidazo[1,2-a]pyrazin-3(7H)-one (1H) with a triplet molecular oxygen (3O2) has been investigated by the geometry optimization at the B3LYP/6-31+G(d) level and the evaluation of the electronic matrix elements for spin-orbit coupling (SOC) using the full Pauli-Breit SOC operator. The reductive activation for the 3O2 reaction is affected by the proton activity and solvent polarity of a surrounding reaction field. In a polar aprotic solvent, a base-prompted anionic substrate may react with 3O2 in a stepwise manner through complete electron transfer from the substrate anion to 3O2, while the irreversible concerted 3O2 addition via intersystem crossing may become complete in a less polar solvent. SOC in the thermal decomposition of a resulting peroxide adduct can be controlled by the protonation state of the substrate. There exists an optimal protonation state for the suppression of SOC in the charge-transfer-induced luminescence (CTIL) of the peroxide, which is closely related with the ability of a substituent to donate an electron. This will constitute a necessary condition for the high efficiency of chemi- and bioluminescence.
authors: Department of Chemistry and Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
authors: Hiroshi
authors: H
authors: Isobe
authors: Syusuke
authors: S
authors: Yamanaka
authors: Seiki
authors: S
authors: Kuramitsu
authors: Kizashi
authors: K
authors: Yamaguchi
mesh_terms: D004583:Electrons; D007093:Imidazoles / Q000737:chemistry*; D049449:Luminescence; D008956:Models, Chemical; D011719:Pyrazines / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D007093:Imidazoles; D011719:Pyrazines