Protocovalent bond

Detailed analysis of a number and types of critical points (attractors) of the ELF field enables a characterisation of quantitative changes of ELF, as well as the electronic structure of the N-Ol bond, within the catastrophe theory. For F01N02, three catastrophes observed during dissociation of the N-Ol bond, one cusp and two fold catastrophes, are shown in Fig. 19.2. The V(N,01) attractor is annihilated in the cusp catastrophe and the protocovalent bond is created by two attractors, V(N) and V(01). Subsequently the V(N) and V(01) attractors are annihilated in the fold catastrophes. 

The results of the N-Ol bond electronic structure, studied in the real space using topological analysis of ELF, will vary depending on the computational method used. At the DFT(B2PLYP)/aug-cc-pVTZ computational level, the N-Ol bonds in both conformers are described by two monosynaptic attractors, V(01) and V(N). Such ELF-topology is characteristic for the protocovalent bond. The core and valence attractors in the syn and anti conformer of the nitrous acid are shown in Fig. 19.3. Similar analysis, carried out using the B3LYP hybrid electron density... 

The alkaline nitrites are examples of molecules with the nitrite group characterised by a single disynaptic V(N,01) and V(N,02) basins, typical for the normal covalent bonds. It is worth noting that the bond lengths are smaller than 1.32 A thus these bonds are essentially shorter than a formally single N-Ol bond in the nitrous acid molecule, where the protocovalent bond has been identified. 

The basin populations calculated at three computational levels for the syn and anti conformers of HONO are collected in Table 19.1. The V(N) and V(01) basin populations of the protocovalent N-Ol bond, obtained with the wave function... 

Table 4 Classification of bonding interaction accrading to ELF criteria core valence bifurcation index bond dissociation variations of the number of basins, A, and of the basin synaptie orders A

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