Nonconventional hydrogen bonding between clusters of gold and hydrogen fluoride

The bonding patterns between small neutral gold (HF)(1 <= m <= 4) and hydrogen fluoride (HF)1, 54 clusters are discussed using a high-level density functional approach. Two types of interactions, anchoring Au-F and F-(HAu)-Au-..., govern the complexation of these clusters. The F-H... Art interaction exhibits all the characteristics of nonconventional hydrogen bonding and plays a leading role in stabilizing the lowest-energy complexes. The anchor bonding mainly activates the conventional F-H... F hydrogen bonds within HF clusters and reinforces the nonconventional F-(HAu)-Au-... one. The strength of the F-H... Au bonding, formed between the terminal conventional proton donor group FH and an unanchored gold atom, depends on the coordination of the involved gold atom: the less it is coordinated, the stronger its nonconventional proton acceptor ability. The strongest F-H... An bond is formed between a HF dimer and the singly coordinated gold atom of a T-shape Au-4 cluster and is accompanied by a very large red shift (1023 cm(-1)) of the v(F-H) stretch. Estimations of the energies of formation of the F-H... Au bonds for the entire series of the studied complexes are provided.