Mechanism of Co–C Bond Photolysis in the Base-On Form of Methylcobalamin
PBN-AR
Instytucja
Wydział Matematyki, Fizyki i Chemii (Uniwersytet Śląski w Katowicach)
Informacje podstawowe
Główny język publikacji
EN
Czasopismo
JOURNAL OF PHYSICAL CHEMISTRY A
ISSN
1089-5639
EISSN
Wydawca
AMER CHEMICAL SOC
DOI
URL
Rok publikacji
2014
Numer zeszytu
50
Strony od-do
11718-11734
Numer tomu
118
Identyfikator DOI
Liczba arkuszy
0,8
Autorzy
Pozostali autorzy
+ 3
Streszczenia
Język
EN
Treść
A mechanism of Co–C bond photodissociation in the base-on form of the methylcobalamin cofactor (MeCbl) has been investigated employing time-dependent density functional theory (TD-DFT), in which the key step involves singlet radical pair generation from the first electronically excited state (S1). The corresponding potential energy surface of the S1 state was constructed as a function of Co–C and Co–Naxial bond distances, and two possible photodissociation pathways were identified on the basis of energetic grounds. These pathways are distinguished by whether the Co–C bond (path A) or Co–Naxial bond (path B) elongates first. Although the final intermediate of both pathways is the same (namely a ligand field (LF) state responsible for Co–C dissociation), the reaction coordinates associated with paths A and B are different. The photolysis of MeCbl is wavelength-dependent, and present TD-DFT analysis indicates that excitation in the visible α/β band (520 nm) can be associated with path A, whereas excitation in the near-UV region (400 nm) is associated with path B. The possibility of intersystem crossing, and internal conversion to the ground state along path B are also discussed. The mechanism proposed in this study reconciles existing experimental data with previous theoretical calculations addressing the possible involvement of a repulsive triplet state.
Inne
System-identifier
0192600114994
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