The active sites of metalloenzymes are principally determined by the ligands that aredirectly coordinated to the metal center(s). However, the reproduction of the first coordination sphere is not sufficient to explain many of the properties of metal centers in proteins and enzymes. It is challenging to introduce second coordination effects into active site analogs. Progress in our attempt to model second coordination sphere effects in Ni-Fe hydrogenase enzymes will be presented. The second coordination effects include hydrogen bonding to the coordinated thiolate ligands and to the Ni center and pendant RSH and RS- interactions with the nickel. The major second coordination sphere effects result in the modification of the Ni(III)/Ni(II)redox couple and the reactivity of the nickel center.

Models for the active sites of hydrogenase enzymes: The role of the second coordination sphere

245th National Meeting (2013)

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