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Vierfach Guanidinyl-funktionalisierte Aromaten: Synthese, Eigenschaften und Anwendung als organische Elektronendonoren und redoxaktive Liganden

Vitske, Viktoriia

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This work focuses on the synthesis and characterization of the new guanidinyl-functionalized aromatic compounds (GFA-4) 1,4,5,8-tetrakis(N,N,N',N' - tetramethylguanidinyl)naphthalene (ttmgn) and 1,4,5,8-tetrakis(N,N,N',N'-dimethylethylenguanidinyl)naphthalene (tdmegn) as well as on the coordination chemistry of these ligands and the use of the new coordination compounds to stabilize monoanionic polyhalides. ttmgn and tdmegn represent strong electron-donors and redox-active ligands. Investigation of the redox behavior using cyclic voltammetry showed the existence of two reversible oxidation processes (oxida-tion to two and fourfold oxidized species) respectively, where tdmegn is a slightly better electron donor in CH3CN than ttmgn. Two and fourfold oxidized ligands were obtained fully characterized. Study of the basic properties showed ttmgn to be a double proton sponge. The protonation experiments on these "superbases" were supported by quantum chemical calculations. A general feature of the characterized coordination compounds was the displacement of the metals from the aromatic plane. The copper(I) complexes [ttmgn(CuI)2] and [ttmgn(CuBr)2] were synthesized and their redox chemistry analyzed. Magnetic superexchange through the ligand unit is studied for the binuclear Co(II) complexes trans-[ttmgn(CoCl2)2] and cis-[tdmegn(CoCl2)2]. SQUID measurements show an extremely weak antiferromagnetic coupling. The dynamic behavior of the metal centers was studied on the example of the Al(III) complex [ttmgn(AlMe2)2][BPh4]2 using NMR experiments. Furthermore, a number of new mono- and binuclear cationic boron complexes was prepared with the ligands ttmgn and btmgn (1,8-Bis(N,N,N',N'-tetramethylguanidinyl)naphthalene). The exchange process between the BF2 groups and BF4 anions in the salt [ttmgn(BF2)2][BF4]2 measured with 19F EXSY NMR spectroscopy points to a complexation equilibrium. It could be shown that the guanidine-boron bond is sufficiently weak to allow the presence of a small quantity of the redox-active ttmgn in solution. Finally, a strategy for the synthesis of polyhalide monoanions was introduced, in which the reducing agent ttmgn is in the cationic complex [ttmgn(BF2)2][BF4]2 "wrapped". Wrapped up in the cationic complex, the reduction power is evidently greatly reduced. Moreover, the relatively large size of the cationic complexes conduces to stabilize monoanionic polyhalides. So reaction of [ttmgn(BF2)2][BF4]2 with I2 and Br2 led respectively to the formation of [I7]‒ and [Br5]‒. This work provides the first complete characterization of the [Br5]‒ monoanion including X-Ray crystal structure.

Item Type: Dissertation
Supervisor: Himmel, Prof. Dr. Hans-Jörg
Date of thesis defense: 9 November 2012
Date Deposited: 16 Jan 2013 10:45
Date: 29 November 2012
Faculties / Institutes: Fakultät für Chemie und Geowissenschaften > Institute of Inorganic Chemistry
Subjects: 540 Chemistry and allied sciences
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