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Müller-Rösing, Hans-Christian (2005): Vom Molekül zum Polymer: Eine quantenmechanische Studie an anorganischen Metall- und Nichtmetallverbindungen. Dissertation, LMU München: Fakultät für Chemie und Pharmazie



The molecular structures of all silver halide monomers, Ag2X, AgX, AgX2 and AgX3, (X = F, Cl, Br, I), have been calculated at the B3LYP, MP2 and CCSD(T) levels of theory by using quasirelativistic pseudopotentials for all atoms except fluorine and chlorine. All silver monohalides are stable molecules, while the relative stabilities of the subhalides, dihalides and trihalides considerably decrease toward the larger halogens. The ground-state structure of all Ag2X silver subhalides has C2v symmetry, and the molecules can be best described as [Ag2]+X-. Silver dihalides are linear molecules; AgF2 has a 2Sg ground state, while all of the other silver dihalides have a ground state of 2Pg symmetry. The potential energy surface (PES) of all silver trihalides has been investigated. Neither of these molecules has a D3h symmetric trigonal planar geometry, due to their Jahn-Teller distortion. The minimum energy structure of AgF3 is a T-shaped structure with C2v symmetry. For AgCl3, AgBr3 and AgI3, the global minimum is an L-shaped structure, which lies outside the Jahn-Teller PES. This structure can be considered as a donor-acceptor system, with X2 acting as donor and AgX as acceptor. Thus, except for AgF3, in the other three silver trihalides, silver is not present in the formal oxidation state 3. Hybrid density functional theory methods have been used to examine the reactivity of hexafluoro- and hexachlorocyclotriphosphazene with respect to single, multiple and complete substitution with water, ammonia, phosphoric and sulfuric acid. Geometries of both educts and all substitution products habe been optimized and their thermodynamic properties are discussed. Based on these results the thermodynamically most favorable reaction pathways have been determined. Starting from a basic unit, which consists of two phosphazene rings that are geminally linked by two hydrazine bridges, several possibilities to form double-stranded chains or helices containing cyclotriphosphazenes were examined by PM3 calculations.