Design of tetrathiafulvalene-based phosphazenes combining a good electron-donor capacity and possible inclusion adduct formation (part II)

Physical properties of intercalated porous material can be modulated by intercalation of small molecules, as this was demonstrated through the iodine (I-2) intercalation into tris(o-phenylenedioxy)cyclotriphosphazene (TPP) crystals. This work describes in depth theoretical considerations of TPP derivatives. The core ring [(NP)(3)] substitution by [(CO)(3)], [(CNH)(3)], and [(CS)(3)], as well as the side group modification in size and composition (containing tetrathiafulvalene-like fragments), is well described from the most important aspects as their geometry optimization, their highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) consideration together with ionization potentials (IP), and their charged forms. On the basis of PBE0/6-31G(d,p) calculations, the neutral forms of the [(CO)(3)], [(CNH)(3)], and [(CS)(3)] containing derivatives are predicted in a distorted caplike conformation. In the first two series, planar (or nearly planar) conformations are predicted upon oxidation, while IP and HOMO energy calculation revealed an electron-donor strength better or comparable to that of the known tetrathiafulvalene (TTF)-like superconductors. Within the [(NP)(3)] based derivatives, the results show that the geometry of the central part may be influenced by the structure of the side fragment. Among the most interesting results, a number of derivatives are predicted to show a good electron-donor strength compared to the commonly used TTF-like donors. More interestingly, a larger number of [(NP)(3)] containing derivatives, especially the O/NH-substituted series, are found to combine the good electron-donor capacity and the paddle wheel molecular shape, making them good candidates for organic superconductors with the ease of modulating their conducting properties by intercalation of suitable acceptors.