Directionality of P●●●O pnicogen bonding in light of geometry corrected statistical analysis
Though it is now known that categorically and bond strength wise the pnicogen bonds are similar to chalcogen and halogen bonds, and even sometimes stronger than the conventional hydrogen bonds, until recently this important supramolecular interaction did not draw much attention from the scientific community. Nevertheless there are some discrete experimental studies, theoretical studies have been dominating to understand the nature of these interactions. Statistical analyses, after proper geometry correction, on experimental crystal structures, of supramolecular interactions, such as hydrogen bonds, π...π and metal...π interactions, halogen and chalcogen bonds have been proven very useful to understand the nature and preferred geometries of these interactions. To the best of our knowledge there is no such geometry corrected statistical analysis on pnicogen bonding reported in the literature. Moreover, even though there is relatively a large number of crystal structures in which P...O pnicogen bonds are present and very few crystal structures in which P...N pnicogen bonds are present on CSD, interestingly, maximum of the studies on pnicogen bonding are based on trivalent P as the Lewis acid and N as the Lewis base and very few studies of pnicogen bonding involving O and higher coordinated P are reported. Here we have reported geometry corrected statistical analysis on P...O pnicogen bonding involving tri and tetra-coordinated P to understand its preferred geometry in the solid state which is probably the first report of geometry corrected statistical analysis on pnicogen bonding. Cone corrected population distribution with respect to XPO angle suggests that X-P...O angle prefers linearity and this preference is more prominent in the case of X3P...O compared to X4P...O pnicogen bonds. This analysis also suggests that the preference for linearity increases with increase in electronegativity of X too.