123091-96-3Relevant academic research and scientific papers
The tightness contribution to the Bronsted α for hydride transfer between NAD+ analogues
Lee, In-Sook Han,Chow, Kim-Hung,Kreevoy, Maurice M.
, p. 7755 - 7761 (2002)
It has been shown that the rate of symmetrical hydride transfer reaction varies with the hydride affinity of the (identical) donor and acceptor. In that case, Marcus theory of atom and group transfer predicts that the Bronsted α depends on the location of the substituent, whether it is in the donor or the acceptor, and the tightness of the critical configuration, as well as the resemblance of the critical configuration to reactants or products. This prediction has now been confirmed for hydride transfer reactions between heterocyclic, nitrogen-containing cations, which can be regarded as analogues of the enzyme cofactor, nicotinamide adenine dinucleotide (NAD+). A series of reactions with substituents in the donor gives Bronsted α of 0.67 ± 0.03 and a tightness parameter, τ of 0.64 ± 0.06. With substituents in the acceptor α = 0.32 ± 0.03 and τ = 0.68 ± 0.08. The reactions are all spontaneous, with equilibrium constants between 0.4 and 3 x 104, and the two sets span about the same range of equilibrium constants. The two τ values are essentially identical with an average value of 0.66 ± 0.05. These results can be semiquantitatively mimicked by rate constants calculated for a linear, triatomic model of the reaction. Variational transition state theory and a physically motivated but empirically calibrated potential function were used. The computed rate constants generate an α value of 0.56 if the hydride affinity of the acceptor is varied and an α of 0.44 if the hydride affinity of the donor is varied. The calculated kinetic isotope effects are similar to the measured values. A previous error in the Born charging term of the potential function has been corrected. Marcus theory can be successfully fitted to both the experimental and computed rate constants, and appears to be the most compact way to express and compare them. The success of the linear triatomic model in qualitatively reproducing these results encourages the continued use of this easily conceptualized model to think about group, ion, and atom transfer reactions.
Excited-state hydroxide ion release from a series of acridinol photobases
Xie, Yun,Ilic, Stefan,Skaro, Sanja,Maslak, Veselin,Glusac, Ksenija D.
, p. 448 - 457 (2017/12/08)
The excited-state heterolysis of acridinol-based derivatives leads to the release of the OH-ion and the formation of the corresponding acridinium cations. To evaluate the parameters that control the reaction barriers, the kinetics of excited-state OH-release from a series of acridinol photobases were studied using transient absorption spectroscopy. The rate constants were obtained in three solvents (methanol, butanol, and isobutanol), and the data were modeled using Marcus theory. The intrinsic reorganization energies obtained from these fits were found to correlate well with the solvent reorganization energies calculated using dielectric continuum model, suggesting that the excited-state OH-release occurs along the solvent reaction coordinate. Furthermore, the ability of acridinol photobases to photoinitiate chemical reactions was demonstrated using the Michael reaction between dimethylmalonate and nitrostyrene.
