Conferencia: "Design and synthesis of organosilicon compounds for potential molecular electronics applications" Profesor Henrik Ottosson. Viernes 31 de enero

El viernes 31 de enero de 2014, a las 12 horas en la Sala de Grados de la Facultad de Ciencias, tendrá lugar la conferencia:"Design and synthesis of organosilicon compounds for potential molecular electronics applications", será impartida por el Profesor Henrik Ottosson del Department of Chemistry - BMC, Uppsala University. Breve curriculum del conferenciante: Henrik Ottosson is Associate Professor (Docent) in physical organic chemistry at the Department of Chemistry ? BMC at Uppsala University, Sweden. In 1996, he graduated with a PhD in Theoretical Chemistry from Gothenburg University, Sweden, on a thesis devoted to quantum chemical calculations of NMR chemical shifts supervised by Prof. Dieter Cremer. He carried out two postdocs; one during 1996-97 at Chalmers University of Technology (Gothenburg), and one during 1997-2000 at University of Colorado at Boulder (USA) where he worked for Prof. Josef Michl on experimental as well as theoretical/computational projects on -conjugated oligosilanes. Since autumn 2000 he is at Uppsala University where he was promoted to Associate Professor in 2003. His research concerns (i) aromaticity effects in electronically excited states (Baird?s rule), (ii) design of molecules that display unusual types of conjugation topologies for use in molecular electronics, and (iii) selective chemistry with unsaturated organosilicon compounds for applications in organic synthesis. Abstract: The dominant conjugation topology found in molecules explored in the field of single-molecule electronics is the -conjugation. However, a series of alternative conjugation topologies exists, such as ;-conjugation and hyperconjugation. We have now explored various organosilicon compounds and analogous heavier Group 14 element compounds in this context. Focus has been given to compounds that display cross-hyperconjugation. The electronic structure properties obtained from both experimental and computational studies, as well as their charge transport characteristics determined through the non-equilibrium Green?s function (NEGF) method, will be discussed. The most basic moiety in our molecules is the ER2 unit (E = C ? Pb, R = alkyl, silyl, germyl, stannyl or plumbyl) having a saturated tetrahedral E atom. With the proper choice of E atom and R groups this unit acts similar to a geminally connected C=C double bond which binds to two ;conjugated arms in a cross;-conjugated manner. Such an ER2 unit leads to a cross-hyperconjugated electronic structure which is manifested through spectroscopy, electrochemistry and quantum chemical computations. The 1,4-disilacyclohexa-2,5-dienes are a class of cyclic cross-hyperconjugated compounds which are valence isolobal with para-xylylene. These compounds manifest large substituent variations in the UV absorption and photoelectron spectra. Moreover, the oligomers display linearly hyperconjugated paths that stretch through the molecules and which show only modest conformational variation in shapes and energies of the frontier orbitals and in calculated zero-bias conductances. Indeed, their conformational conductance variations are several orders of magnitude smaller than that of an analogous linear oligosilane. The oligo(1,4-disilacyclohexa-2,5-diene)s thus have some properties of molecular ?electrical cords? with a conformer-independent conductance. Furthermore, we synthesized and explored the basic electronic structure properties of 1,4-disubstituted cyclohexasilanes. Configurational and conformational variations in the optical and electrochemical properties were found, and based on NEGF calculations we postulate that this unit may serve as a mechanically controllable single-molecule switch. Cartel
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