Three-gold cluster hydrogen bonds

THREE-GOLD CLUSTER AS PROTON ACCEPTOR IN NONCONVENTIONAL HYDROGEN BONDS O-H Au AND N-H Au... 

We conclude that the bond O2-H2 AU5 formed in the complex FA Aus is an example of a nonconventional hydrogen bond. The 5d orbital of the gold atom Au5 in three-gold cluster exhibits a lone-pair character which induces its proton acceptor ability. 

To recapitulate what we have discussed so far, we emphasize that three major bonding effects underlie the interaction between the gold clusters Au3 and Au4 and water oligomers. They are the anchor Au-O bonding, the nonconventional O-H Au hydrogen bonding, and the activation of the adjacent O-H bond. We provide a computational evidence that the formation of the donor-acceptor coordinative (anchor) bond Au-O in the studied complexes is a necessary prerequisite (but not sufficient) to the formation of the nonconventional hydrogen bond and to the activation of the adjacent O-H bond, and therefore this bond dominates the interaction mechanism. 

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