Complexes [(C2H2X2)2M]n with ligating atoms X = O, S and central atoms M = Li (n = 0, ± 1) and Be (n = 0, ± 2) have been studied by quantum chemical ab initio calculations. Total energies, relative binding energies and orbital energies of mainly planar complexes of standard geometry have been studied. The effect of variation of geometry including non‐planarity has also been considered. The primary binding region is found to contain appreciable interactions not only within pairs MX but for the sulfur case also of the type XX'. The chelate form of the ligands is shown to be essential to the properties of the complexes.
Semiempirical molecular orbital calculations within a modified PPP method, the Peel method, have been performed in order to study the electronic structure and properties of porphyrins and phthalcxyanines. It is found that the calculations can reproduce the results from more sophisticated ab initio calculations. It is found that the electronic reactions may take place at the metal atom and in the axial direction. The role of the porphine plane seems to be that of an electron buffer, keeping the electronic population in the porphyrin plane constant. A mechanism is suggested where electron transfer reactions can take place by changes in the molecular geometry, as for example by vibrations.
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