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Abstract
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In the present study a predictive model aimed at the selection of organic ligands for the successful synthesis of Cobalt sandwich-type polyoxometalate (Co-STPs) organic–inorganic hybrid compounds in aqueous solution, has been introduced. The computations were performed using Gaussian09 and the results have been evaluated by the graphic interface program, GaussView05. Geometry optimization and frequency calculations have been performed at B3LYP level with 6-311G basis set. Dipole moment was recalled from optimization results and reactivity descriptors were calculated via Fukui function using atomic charges and frontier orbitals energies. Firstly the organic molecules with dipole moments more than water are filtered.
Then, ligands with less electronegativity, hardness, global electrophilicity and energy bond gap and more softness, global softness and chemical potential found to be promoters for substitution reaction on the cobalt atoms. From the local reactivity descriptors, it is concluded when the fk , Sk , ?k > fk-, Sk-, ?k- and ?k is greater than Sk , the ligand will undergo substitution reaction.
2-Aminobenzimidazole (ABI), 4-nitroaniline (PNA), imidazole and pyridine were evolved in synthesis reaction to test the predicted results for a major product. Applying obtained rules from local Fukui descriptors has predicted ABI and PNA will engage in a substitution reaction, which indeed occurred and resulted in two new thermodynamic controlled and purple colored organic–inorganic hybrid sandwich type polyoxometalates, (PNA)2Na12[Co4(PW9O34)2] and (ABI)2Na12[Co4(PW9O34)2]. These hybrids were characterized by infrared spectroscopy, ICP-MS, TGA-DSC and EDX. Imidazole and pyridine were failed to perform substitution reaction and led to yellow disfavored kinetic controlled products.
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