AbstractsChemistry

In the present work the methods of relativistic quantum chemistry have been applied to a number of small systems containing heavy elements, for which relativistic effects are important. First, a thorough introduction of the methods used is presented. This includes some of the general methods of computational chemistry and a special section dealing with how to include the effects of relativity in quantum chemical calculations. Second, after this introduction the results obtained are presented. Investigations on high-valent mercury compounds are presented and new ways to synthesise such compounds are proposed. The methods described were applied to certain systems containing short Pt-Tl contacts. It was possible to explain the interesting bonding situation in these compounds. One of the most common actinide compounds, uranium hexafluoride was investigated and a new picture of the bonding was presented. Furthermore the rareness of uranium-cyanide compounds was discussed. In a foray into the chemistry of gold, well known for its strong relativistic effects, investigations on different gold systems were performed. Analogies between Au$^+$ and platinum on one hand and oxygen on the other were found. New systems with multiple bonds to gold were proposed to experimentalists. One of the proposed systems was spectroscopically observed shortly afterwards. A very interesting molecule, which was theoretically predicted a few years ago is WAu$_{12}$. Some of its properties were calculated and the bonding situation was discussed. In a further study on gold compounds it was possible to explain the substitution pattern in bis[phosphane-gold(I)] thiocyanate complexes. This is of some help to experimentalists as the systems could not be crystallised and the structure was therefore unknown. Finally, computations on one of the heaviest elements in the periodic table were performed. Calculation on compounds containing element 110, darmstadtium, showed that it behaves similarly as its lighter homologue platinum. The extreme importance of relativistic effects for these systems was also shown. I detta arbete har relativistiska kvantkemiska metoder tillämpats på ett antal system som innehåller tunga element, för vilka relativistiska effekter är av stor betydelse. I första delen diskuteras de använda metoderna noggrannt. Den teoretiska delen innehåller information om beräkningskemins generella metoder och ett speciellt stycke om hur relativistiska effekter kan inkluderas. Efter den teoretiska delen presenteras resultaten. I en undersökning av högvalenta kvicksilverföreningar föreslås nya möjligheter att syntetisera dem. De teoretiska metoderna tillämpades även på system med korta Pt-Tl bindningar. Den undersökningen förklarar den intressanta bindningen i dessa föreningar. En av de mest använda aktinidföreningarna, uranhexafluorid, studerades också. En ny modell för dess bindningar presenteras. Utöver detta ges en förklaring, varför uran(VI)cyanider är så sällsynta. Guld är välkänt för sina starka relativistiska effekter och…