Abstract
The reaction mechanism and details of the formation of CIDNP (chemically induced dynamic nuclear polarization) in the photoreactions of 2,2‘-dipyridyl (DP) and N-acetyl histidine (HisH) in aqueous solution have been studied using laser flash photolysis and time-resolved CIDNP techniques. The triplet state TDP reacts with protonated HisH2+ via hydrogen atom transfer with a rate constant kH = 1.2 × 108 M-1 s-1, and with deprotonated His- via electron transfer with ke = 7.5 × 109 M-1 s-1. No reaction occurs when the histidine imidazole ring is in its neutral state HisH, or when the dipyridyl triplet is protonated, TDPH+. The nuclear spin−lattice relaxation times in the radicals formed in these reactions have been determined from the CIDNP kinetics: T1 = 44 ± 9 μs for all DP protons, T1 = 196 ± 25 μs for the β-CH2 protons of HisH, and T1 = 16 ± 5 μs for the H-2 and H-4 protons of HisH. Under strongly basic conditions the CIDNP is greatly affected by degenerate electron exchange between the neutral His· radic...
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.