"pnicogen bonds" or "chalcogen bonds": Exploiting the effect of substitution on the formation of P⋯Se noncovalent bonds

In this article, we have analyzed the nature and characteristics of P⋯Se noncovalent interactions by studying the effect of substitution on XH₂P⋯SeH₂, H₃P⋯SeHX and XH₂P⋯SeHX (X= -H, -F, -CH₃, -CF₃, -Cl, -OH, -OCH₃, -NH₂, -NHCH₃, and -CN) as our systems of interest at MP2/aug-cc-pVDZ level of theory. Binding energy calculations depict that binding energy increases in the order XH₂P⋯SeH₂ < H₃P⋯SeHX < XH₂P⋯SeHX with the nature of the substituent having a direct effect on the strength of the interactions. P⋯Se contacts as short as 2.52 Å were observed and analyzed in our study. The energy values for P⋯Se contacts were found to exist in the range of -1.20 kcal mol^-1 to -7.89 kcal mol^-1. The topological analysis confirms the presence of P⋯Se contacts in all the complexes with characteristics similar to hydrogen bonds. NBO analysis helped in categorizing these interactions into pnicogen and chalcogen bonds, depending on the strength of P(lp) to σ∗(Se-X) orbitals or Se(lp) to σ∗(P-X) orbitals.