Probing non-covalent interactions of phosphine and arsine derivatives: an energy decomposition analysis using localized molecular orbitals

Ab initio (MP2/aug-cc-pVTZ) and density functional theory (DFT) (B3PW91/aug-cc-pVTZ and B3LYP-D3/Def2-TZVPP) analyses have been carried out to characterize the bonding of phosphine and arsine derivatives i.e., M-RH2-HF (M = As or P, R = furan, pyridine, pyrrole, and thiophene) with hydrogen fluoride (HF). Two minima were found on the potential energy surface (PES) for each complex, one in which HF is forming directly an H-bond with pnicogen while the other one in which HF is interacting with the heterocyclic ring in addition to normal H-bond. The latter one is highly stable with MP2/CBS extrapolated binding energies ranging from -10.67 kcal mol(-1) to -6.33 kcal mol(-1). The interaction energies in these complexes follow the order P-PyrHF > P-ThioHF > P-FuHF > P-PyHF > As-PyrHF > As-ThioHF > As-FuHF > As-PyHF. NBO analysis demonstrated that LPAs/P -> sigma H-F orbital interaction plays a major role in stabilizing these complexes, and the largest charge is transferred in P-type complexes compared with their As-type analogs. The LMO-EDA pointed out that all the partitioning terms are stabilizing in nature with a dominant role carried out by exchange energy while as the repulsion energy is the only term being destabilizing in nature. Many body interaction analysis in ternary complexes M-RH2-(HF)(2), in which the other interaction site of heterocyclic rings (N, O, and S) were used for second H-bonding with another HF molecule, revealed that the second H-bond is destabilizing the pnicogen H-bond and showed negative synergetic effects.