Halogen bonding interactions in the XC5H4N···YCF3 (X = CH3, H, Cl, CN, NO2; Y = Cl, Br, I) complexes.

The noncovalent interactions between the σ-hole region outside the halogen atom and the nitrogen atom of pyridine and its para-substituted derivatives are the focus of this work. Based on the analyses of the electrostatic potentials, YCF3 (Y = Cl, Br, I) act as halogen bond donors, XC5H4N (X = CH3, H, Cl, CN, NO2) act as halogen bond acceptors, and the binary halogen-bonded complexes XC5H4N···YCF3 have been designed and investigated by B3LYP-D3/aug-cc-pVDZ calculations together with the aug-cc-pVDZ-PP basis set for iodine. When the halogen bond acceptor remains unchanged, the interactions between C5H5N and YCF3 (Y = Cl, Br, I) increase with the order of Y = Cl, Br, and I. When the halogen donor ICF3 is fixed, the halogen bonding interactions decrease along the sequence of X = CH3, H, Cl, CN, NO2. Therefore, the halogen bond of the CH3C5H4N···ICF3 complex is the strongest. [ABSTRACT FROM AUTHOR]