"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 center dot center dot center dot Se noncovalent interactions by studying the effect of substitution on XH2P center dot center dot center dot SeH2, H3P center dot center dot center dot SeHX and XH2P center dot center dot center dot 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 center dot center dot center dot SeH2 < H3P center dot center dot center dot SeHX < XH2P center dot center dot center dot SeHX with the nature of the substituent having a direct effect on the strength of the interactions. P center dot center dot center dot Se contacts as short as 2.52 angstrom were observed and analyzed in our study. The energy values for P center dot center dot center dot 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 center dot center dot center dot 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 sigma(star)(Se-X) orbitals or Se(lp) to sigma(star)(P-X) orbitals.