A B3LYP and MP2(full) theoretical investigation into the cooperativity effect between dihydrogen-bonding and H-Ma™a™a™π (M = Li, Na, K) interactions among HF, MH with the π-electron donor C2H2, C2H4 or C6H6

The DFT-B3LYP/6-311++G(3df,2p) and MP2(full)/6-311++G(3df,2p) calculations were carried out on the binary complex formed by HM (M = Li, Na, K) and HF or the pi-electron donor (C2H2, C2H4, C6H6), as well as the ternary system FHa (TM) a (TM) a (TM) HMa (TM) a (TM) a (TM) C2H2/C2H4/C6H6. The cooperativity effect between the dihydrogen-bonding and H-Ma (TM) a (TM) a (TM)pi interactions was investigated. The result shows that the equilibrium distances R (Ha (TM) a (TM) a (TM) H) and R (Ma (TM) a (TM) a (TM)pi) in the ternary complex decrease and both the Ha (TM) a (TM) a (TM) H and H-Ma (TM) a (TM) a (TM)pi interactions are strengthened when compared to the corresponding binary complex. The cooperativity effect of the dihydrogen bond on the H-Ma (TM) a (TM) a (TM)pi interaction is more pronounced than that of the Ma (TM) a (TM) a (TM)pi bond on the Ha (TM) a (TM) a (TM) H interaction. Furthermore, the values of cooperativity effect follow the order of FHa (TM) a (TM) a (TM) HNaa (TM) a (TM) a (TM)pi > FHa (TM) a (TM) a (TM) HLia (TM) a (TM) a (TM)pi > FHa (TM) a (TM) a (TM) HKa (TM) a (TM) a (TM)pi and FHa (TM) a (TM) a (TM) HMa (TM) a (TM) a (TM) C6H6 > FHa (TM) a (TM) a (TM) HMa (TM) a (TM) a (TM) C2H4 > FHa (TM) a (TM) a (TM) HMa (TM) a (TM) a (TM) C2H2. The nature of the cooperativity effect was revealed by the analyses of the charge of the hydrogen atoms in Ha (TM) a (TM) a (TM) H moiety, atom in molecule (AIM) and electron density shifts methods.