<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers"^^ . "The main topic of this thesis is the comparative investigation of divalent selenium centers interactions in solids and solution. Therefore we decided to combine experimental and theoretical results in order to gather more insight into selenium – selenium interactions. The idea of using the chalcogen–chalcogen interactions as directional forces to obtain tubular structures was validated during recent experimental studies in which cyclic aliphatic diynes and dienes containing chalcogen atoms organized themselves in columnar structures. Moreover, theoretical investigations confirmed the description of divalent selenium interactions as a secondary interaction between an occupied p-type orbital of one chalcogen center (X) and the empty X-C sigma* orbital of the other, together with induction and dispersion forces. The first part of this work deals with the synthesis of three isomeric cyclophanes and their solid-state structures in comparison with previously synthesized similar cyclic compounds. The cycles investigated so far consisted of rigid units (e.g. X-CC-X, where X= S, Se, Te) and methylene chains as flexible parts. The inclusion of benzene rings into the methylene chains is expected to add more rigidity and also to open the possibility of pi-pi stacking. The synthesis of the three isomeric tetraselena-[6.6]cyclophanes 18(a-c) was achieved using a stepwise approach.Remarkable features of the solid-state structure of 18 a-c were analyzed and compared with other structural features of compounds that involved Se centers in Se•••Se interactions. The second part of this work investigates the presence and the strength of the Se•••Se interaction in solution. A series of model systems containing two selenium centers situated at a convenient distance, but also with significant internal motion ability, were synthesized. The NMR spectroscopy was the method of choice to investigate the interaction in solution. 77Se NMR chemical shifts are sensitive to the electronic environment around the Se atom, therefore their behaviour can be used as gauge for evaluating the strength of nonbonding interactions involving Se centers. Coupling constants (J coupling) and relaxation time determinations supported the findings from the investigations of 77Se NMR chemical shifts. Theoretical calculations at the MP2/6-311+g(d)//B98/6-311+g(d) level revealed the existence of four conformers for each of the investigated compounds, in which the Se•••Se interaction or the competing Se•••H bonding is the predominant force. Concluding, the investigation of the nature of the Se•••Se interactions show that the 77Se chemical shifts represent an useful tool in qualitatively assessing the strength of the interaction. The strength in the order MeSe•••SeMe < MeSe•••SeCCH < MeSe•••SeCN qualitatively revealed from the NMR chemical shifts is consistent with the nSe–sigma*Se-C orbital interaction model. It proves furthermore that electron correlation and dispersion forces play an intimately interconnected role in these interactions, that influence each other, therefore being difficult to analyze separately."^^ . "2008" . . . . . . . . "Alberth"^^ . "Lari"^^ . "Alberth Lari"^^ . . . . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (PDF)"^^ . . . "ALari_PHDthesis.pdf"^^ . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Inter and Intramolecular Interactions Between Divalent Selenium Centers (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #8833 \n\nInter and Intramolecular Interactions Between Divalent Selenium Centers\n\n" . "text/html" . . . "540 Chemie"@de . "540 Chemistry and allied sciences"@en . .