Modelling the Structure and Properties of Aluminophosphonates

Several aluminophosphonate materials have been investigated using both semi-empirical quantum mechanical and Density Functional Theory (DFT) methodologies. The optimised structures obtained are in excellent agreement with experimental results. Important information on the electronic distribution in these structures is obtained, allowing charge distributions to be determined and H2O-framework interactions to be probed. The barriers to rotation for the organic groups in three structures have been investigated. Results for -(CH3) groups in AlMePO-alpha and AlMePO-beta, yield barrier heights that are consistent with rapid rotation at ambient temperature, whereas the barrier height obtained for -(C6H5) in AlBzPO-I suggests that the framework will significantly hinder rotation. The use of modelling to help elucidate the structure of a novel compound, AlMePO-2, and to probe the structure and stability of a hypothetical aluminium ethyl phosphonate, AlEtPO, are also illustrated.