%0 Journal Article
%A Sundar, J. Vijaya
%A Subramanian, V.
%D 2012
%T Mechanistic Studies on
the pH-Controllable Hydrogenation
of NAD+ by H2 and Generation of H2 from NADH by a Water-Soluble Biomimetic Iridium Complex
%U https://acs.figshare.com/articles/journal_contribution/Mechanistic_Studies_on_the_pH_Controllable_Hydrogenation_of_NAD_sup_sup_by_H_sub_2_sub_and_Generation_of_H_sub_2_sub_from_NADH_by_a_Water_Soluble_Biomimetic_Iridium_Complex/2457550
%R 10.1021/om300812k.s001
%2 https://acs.figshare.com/ndownloader/files/4100230
%K NAD
%K nicotinamide adenine dinucleotide
%K H 2
%K NADH
%K pH
%K medium
%K activation barrier height
%K mechanism
%K Ir
%X Functional biomimicking of hydrogenases at ambient conditions
is
challenging. Recently an Ir(III)-cyclometalated complex (J.
Am. Chem. Soc. 2012, 134, 367)
has been shown to catalyze the pH-dependent reversible reduction of
NAD+ (nicotinamide adenine dinucleotide) by dihydrogen
in water medium. Yet, the reaction mechanism for the catalysis has
not been unravelled comprehensively. Hence in this work, mechanisms
for catalytic hydrogenation of NAD+ to the reduced form
of NAD+ (NADH) and the reverse reaction catalyzed by the
Ir(III)-cyclometalated complex have been proposed using the results
obtained from density functional theory based calculations. The mechanism
suggests that the carboxylate group of the Ir(III) complex can act
as a proton relay between hydrogen and water molecules. As a consequence,
the direction of the reaction is controlled by the pH of the medium.
Splitting of H2 and generation of H2 are the
rate-determining steps in the two directions with the same activation
barrier height of 34.6 kcal/mol. Also, the mechanism supports that
the σ-bond metathesis is preferred over oxidative addition of
hydrogen. Results show that NADH may act as an inhibitor of the substrate
at high basic pH.
%I ACS Publications