Abstract
The reconstitution of [Mn]‐hydrogenases using a series of MnI complexes is described. These complexes are designed to have an internal base or pro‐base that may participate in metal–ligand cooperative catalysis or have no internal base or pro‐base. Only MnI complexes with an internal base or pro‐base are active for H2 activation; only [Mn]‐hydrogenases incorporating such complexes are active for hydrogenase reactions. These results confirm the essential role of metal–ligand cooperation for H2 activation by the MnI complexes alone and by [Mn]‐hydrogenases. Owing to the nature and position of the internal base or pro‐base, the mode of metal–ligand cooperation in two active [Mn]‐hydrogenases is different from that of the native [Fe]‐hydrogenase. One [Mn]‐hydrogenase has the highest specific activity of semi‐synthetic [Mn]‐ and [Fe]‐hydrogenases. This work demonstrates reconstitution of active artificial hydrogenases using synthetic complexes differing greatly from the native active site.
Highlights
Artificial enzymes incorporating non-native metal cofactors while exhibiting native activities can serve as important tools for mechanistic studies of enzymes.[1]
The mechanisms of H2 activation in previously reported [Fe]- and [Mn]-hydrogenases all involve metal-ligand cooperation, where a basic 2-OÀ group generated by deprotonation of the 2-OH group of an pyridone derivative deprotonates the H2 molecule coordinated to the metal ion (Figure 1 B).[1d,e,6a] In this study, we design and synthesize a series of MnI complexes with or without an internal base or pro-base (Figure 1 C)
Subsequent to the work with 1 a, we designed a series of new MnI models (1 b–1 e) that could be used to probe the influence of an internal base for H2 activation
Summary
Artificial enzymes incorporating non-native metal cofactors while exhibiting native activities can serve as important tools for mechanistic studies of enzymes.[1]. The mechanisms of H2 activation in previously reported [Fe]- and [Mn]-hydrogenases all involve metal-ligand cooperation, where a basic 2-OÀ group generated by deprotonation of the 2-OH group of an pyridone derivative deprotonates the H2 molecule coordinated to the metal ion (Figure 1 B).[1d,e,6a] In this study, we design and synthesize a series of MnI complexes with or without an internal base or pro-base (Figure 1 C). Among the former complexes, the nature and position of the internal base or pro-base are different. This strategy might be used to expand the functions of Hmd hydrogenases beyond native reactions using novel substrates other than methenyl-/methylene-H4MPT and H2
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