Incorporation of stable organic radicals into cyclotriphosphazene: preparation and characterization of mono- and diradical adducts.

Stable cyclotriphosphazenes 4 and 5, incorporating one and two carbon radical centers, respectively, have been easily prepared and characterized. EPR spectroscopic studies in fluid solution at room temperature were carried out for both compounds and also for diradical 5 in frozen solvent matrixes. Spectral results are consistent with a triplet or degenerate singlet triplet ground state for 5. Reductive cyclic voltammetry shows a redox couple, being monoelectronic for 4 and bielectronic for 5.

Structural features and molecular assembly of amorphous phosphazenic materials in the bulk--combined theoretical and experimental techniques: Tris-(2,2'-dioxy-1,1'-binaphthyl)cyclotriphosphazen.

The structure and the assembly of tris-(2,2'-dioxy-binaphthyl)cyclotriphosphazene [(+)-[NP3(O2C20H12)3], DBNP, in the solid amorphous state was studied using molecular dynamics (MD) including ad hoc quantum mechanically derived force field (FF) parameters, in combination with the energy dispersive X-ray diffraction (EDXD) technique. The atom-atom radial distribution function (RDF) curve obtained through the EDXD experiment revealed low intensity peaks not attributable to the intramolecular distances of the single molecule, but clearly featuring a low energy state of long-distance three-dimensional assembly. The radial distribution functions (RDF) were calculated for various models of DBNP submitted to theoretical MD simulations. Based on the comparison of theoretically calculated RDFs and those obtained from the EDXD experiment, the predominant structural motif of the material in the bulk was found to have DBNP molecules laid one upon the other to form tubular nanostructures. These contain eight DBNP units each (length ca. 46 A) with two and three of these units aligned in parallel and held together. The material can be represented as a bulk of tubular snake-like chains undergoing distortions with a step of eight DBNP units. The bending angles, that vary randomly, attain limited values sufficient to induce disorder and thus nonperiodic structure. The present application of MD simulations combined with EDXD data appear to be a general approach to solve for the first time otherwise intractable issues concerning structural features and assembly of molecular materials in the bulk.