Analysis of Oxygen–Pnictogen Bonding with Full Bond Path Topological Analysis of the Electron Density

Abstract

A variety of methods are available to investigate the bonding in inorganic compounds. In contrast to wavefunction-based analyses, topological analysis of the electron density affords the advantage of analyzing a physical observable: the electron density. Classical topological analyses of bonding interactions within the Atoms in Molecules framework typically involve location of a bond path between two atoms and evaluation of a range of real-space functions at the (3, -1) critical point in the electron density that exists on that bond path. We show here that counter-intuitive trends are obtained from the analysis of the electron density (ρ), the Laplacian (∇ 2 ρ), and ellipticity (ε) at the O-E (3, -1) critical points in the CCSD electron densities of a series of compounds featuring a range of oxygen-pnictogen bond types: EO + , HEO, H2EOH, H3EOH + and H3EO (where E = N, P, As, Sb, or Bi). If, instead, these real-space functions are evaluated along the length of the bond path, the discrepancies in the trends are resolved. We show that robust results are also obtained using electron densities from less computationally demanding DFT calculations. The increased computational efficiency allowed us to also investigate organic derivatives of these oxygen-pnictogen bonded compounds and observe that the trends hold in these instances as well. We anticipate that these results will be of use to inorganic chemists engaged in the synthesis and evaluation of novel bonding interactions, particularly those involving heavy main-group elements.

Tuning the Kinetic Inertness of Bi3+ Complexes: The Impact of Donor Atoms on Diaza-18-Crown-6 Ligands as Chelators for 213Bi Targeted Alpha Therapy

“…In the plot of ∇ 2 ρ(r), the single local minimum along the bond path is located near the oxygen atom (Figure 6b), a feature that is observed in other systems with interactions between second-period elements and third-and fourth-period elements. [99][100][101][102][103][104] It has been shown that the decrease in the magnitude of this local minimum can be attributed to a decrease in bond order. 99 As expected, the local minimum for [Bi(macroquin-SO 3 )] − is considerably more negative than for [Bi(macroposphi)] + , suggesting that the interaction between Bi and the O donor atoms of the quinoline pendent arms is more covalent in nature than those of the picolinate donors.…”

“…[99][100][101][102][103][104] It has been shown that the decrease in the magnitude of this local minimum can be attributed to a decrease in bond order. 99 As expected, the local minimum for [Bi(macroquin-SO 3 )] − is considerably more negative than for [Bi(macroposphi)] + , suggesting that the interaction between Bi and the O donor atoms of the quinoline pendent arms is more covalent in nature than those of the picolinate donors. Taken together, these results suggest that the enhanced kinetic inertness of [Bi(macroquin-SO 3 )] − compared to the other chelators described here may stem from the increased covalency between the metal center and the donor atoms of the pendent arms.…”

The Phosphorus Bond, or the Phosphorus-Centered Pnictogen Bond: The Covalently Bound Phosphorus Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

“…Noncovalent interactions show up in different flavors, including, for example, hydrogen bonding [ 23 ], halogen bonding [ 24 ], tetrel bonding [ 25 , 26 , 27 ], chalcogen bonding [ 28 ], pnictogen bonding [ 29 , 30 , 31 , 32 ], aerogen bonding [ 33 ], van der Waals interactions [ 34 ], and several others [ 35 ]. They are the result of attractive engagements between sites of unequal charge density and are often identified to be of Coulombic origin (a positive site attracting a negative one).…”

The Pnictogen Bond: The Covalently Bound Arsenic Atom in Molecular Entities in Crystals as a Pnictogen Bond Donor

“…Pnictogen bonding, unlike other noncovalent interactions, is among the least theoretically and computationally studied chemical interactions [ 1 , 2 , 3 , 4 , 5 , 6 ], yet has been featured in applications in many areas such as catalysis [ 7 , 8 , 9 , 10 ], coordination chemistry [ 3 , 11 , 12 , 13 , 14 , 15 ], photovoltaics [ 16 , 17 ], and supramolecular chemistry [ 4 , 5 ]. There are relatively few reviews [ 3 , 18 , 19 , 20 , 21 , 22 ], original papers (for example [ 1 , 5 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]), overviews [ 30 ], and comments on the strength [ 31 ], nature [ 32 , 33 ], and propensity of elements of the pnictogen family (Group 15) to engage in pnictogen bonding [ 34 , 35 , 36 ]. The reason for this is probably because recent work on noncovalent interactions has focused largely on exploring σ-hole and π-hole interactions [ 37 , 38 , 39 , 40 , 41 , 42 , …”