Angular overlap method

A simplification of this method is that put forward by Jergensen et al. and called the "angular overlap method (2, 6). This method has the advantages of simplicity and of the transferability of the parameters from one chromophore MXq to another MXp of different symmetry if all the M-X distances are the same. 

The application of the angular overlap method to MXg chromophores of trigonal bipyramidal and square p3u-amidal stereochemistry leads to the patterns of Fig. 2 for the energies of the antibonding "d molecular orbitals (dc). The crystal field model leads to a similar pattern. 

Table 70 Angular Overlap Method (AOM) d-Oribital a- and -Interaction Energies for Various Regular Copper(II)...

As regards the angular dependence of the splitting parameters, the crystal field and angular overlap methods give comparable results, though these are usually quite sensitive to the assumed values of the ratios and azjui. 

It must be admitted that any semi-empirical MO model which seeks to provide a basis for the interpretation of d—d spectra of non-cubic complexes must involve drastic approximations. It seems that we are faced with two alternatives either we stick to simpler empirical models (such as the crystal field or angular overlap methods) or we make a more serious attempt to solve the problem exactly. We therefore turn to non-empirical ab initio SCF calculations which are now becoming feasible for transition metal compounds. 

In addition, these diagrams of homoleptic complexes (with all the ligands identical) are simpler than those of heteroleptic complexes with variation within the Ugand set. The angular overlap method (Section 10.4) provides a strategy for predicting electronic structure information for heteroleptic complexes. 

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