Pair Population Analysis within AIM Theory

Abstract

The pair population analysis developed some time ago as a straightforward link between quantum chemical and classical picture of bonding was generalized by incorporating its formalism into the framework of AIM theory. A detailed numerical comparison between the results derived from the original pair population analysis and those from AIM generalization is reported. On the basis of this comparison, the reliability of both approaches is evaluated. In addition to this a numerical test of the accuracy of the Lewis electron pair model is also reported.

On the Electronic Structure ofmer,trans‐[RuCl3(1H‐indazole)2(NO)], a Hypothetical Metabolite of the Antitumor Drug Candidate KP1019: An Experimental and DFT Study

“…[62] Nonetheless, the Laplacian eigenvalues for this bond are -0.0540, -0.0246, and 0.3937 e bohr -5 . The Ru-O1 negative BCP Laplacian eigenvalues are at least an order of magnitude smaller than the eigenvalues of usual covalent bonds for which the interpretation of bond ellipticity is straightforward (this also holds for the remaining Ru-ligand bonds [92][93][94] The above QTAIM data can conveniently be complemented by QTAIM bond indices [63,64] (see Table 3), which give a quantitative measure of the electron exchange between atomic domains (i.e., they can be considered as a bond-order analogue). The highest values for the two-center bond index are observed for the N3-O1 and Ru-N3 bonds.…”

Electron localization and delocalization in open‐shell molecules

“…The first of the two singly occupied orbitals in the HNC triplet is very similar to the singly occupied orbital in the CN doublet (see above), and it has partial bonding and nonbonding character. The second singly occupied orbital has bonding character between the N and H atoms, and antibonding between N and C. It is interesting to compare the singlet and triplet states of the HNC molecule in terms of orbital occupations and its effects on the bond length and interatomic delocalization between C and N. With respect to the singlet-ground state, in the triplet state there is an electron excited from an orbital with partial bonding and nonbonding character, aЈ (7) to an antibonding orbital aЈ (8) :…”

“…aЉ (6) (2)aЈ (7) (1)aЈ (8) (1) This is reflected, for instance, in the CON distance, which is larger in the triplet state (1.223 Å) than in the singlet (1.154 Å). Interestingly, the atomic overlaps of orbital aЈ (8) with the rest of the orbitals with aЈ symmetry are rather small, and the net effect of the excitation is an increase in ␦(C,N) (see Appendix A). In summary, the CON bond is stronger in the ground singlet state, but the electron delocalization between the C and N atoms is larger in the triplet state.…”

The role of ionic structures in the response of a non-polar molecule to an electric field

“…The investigation of the behavior of electron pairs (i.e. the simultaneous presence of two electrons) can be realized by means of population analysis of molecular orbital (MO) wave functions, providing new insights for chemical bonding [3][4][5][6]. Going beyond this type of analysis, the behavior of electron pairs in conjunction with the presence of two electron holes, can be investigated by means of poly-electron population analysis (PEPA) [7].…”