Substituent effects on the cooperativity of halogen bonding.

DFT calculations (B97-1) with the 6-31+G(d,p)-LanL2DZdp basis set were used to analyze the intermolecular interactions in 4-Z-Py···XCN···XCN triads (Z = H, F, OH, OCH3, CH3, NH2, NO2, and CN; Py = pyridine; and X = Cl and Br) that are connected by halogen-bond interactions. To understand the properties of the systems better, the corresponding dyads are also studied. Particular attention is given to parameters such as cooperative energy.

Cooperative and diminutive unusual weak bonding in F3CX···HMgH···Y and F3CX···Y···HMgH trimers (X = Cl, Br; Y = HCN, and HNC).

MP2 calculations with cc-pVTZ basis set were used to analyze intermolecular interactions in F(3)CX···HMgH···Y and F(3)CX···Y···HMgH triads (X = Cl, Br; Y = HCN, and HNC) which are connecting with three kinds of unusual weak interactions, namely halogen-hydride, dihydrogen, and σ-hole. To understand the properties of the systems better, the corresponding dyads are also studied. Molecular geometries, binding energies, and infrared spectra of monomers, dyads, and triads were investigated at the MP2/cc-pVTZ computational level.