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Heavy-Core Staffanes :
Heavy-Core Staffanes : A Computational Study of Their Fundamental Properties of Interest for Molecular Electronics
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- Sandström, Niclas, 1973- (författare)
- Uppsala universitet,Institutionen för biokemi och organisk kemi
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- Ottosson, Henrik, Doc. (preses)
- Uppsala universitet,Institutionen för biokemi och organisk kemi
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- Hammarström, Leif, Prof. (preses)
- Uppsala universitet,Institutionen för fotokemi och molekylärvetenskap
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- Albinsson, Bo, Prof. (opponent)
- Institutionen för kemi och bioteknink, Fysikalisk kemi, Chalmers tekniska högskola, Göteborg
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(creator_code:org_t)
- ISBN 9789155467968
- Uppsala : Acta Universitatis Upsaliensis, 2007
- Engelska 80 s.
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Serie: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 271
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Abstract
Ämnesord
Stäng
- The basic building blocks in molecular electronics often correspond to conjugated molecules. A compound class consisting of rigid rod-like staffane molecules with the heavier Group 14 elements Si, Ge, Sn and Pb at their bridgehead positions has now been investigated. Herein these oligomers are called heavy-core or Si-, Ge-, Sn- or Pb-core staffanes. These compounds benefit from interaction through their bicyclo[1.1.1]pentane monomer units. Quantum chemical calculations were performed to probe their geometries, stabilities and electronic properties associated with conjugation. The stabilities of the bicyclo[n.n.n]alkane and [n.n.n]propellanes (1 ≤ n ≤ 3) with C, Si, Ge and Sn at the bridgehead positions were studied by calculation of homodesmotic ring strain energies. The bicyclic compounds with n = 1 and Si, Ge or Sn at bridgehead positions have lower strain than the all-carbon compound. A gradually higher polarizability exaltation is found as the bridgehead element is changed from C to Si, Ge, Sn or Pb. The ratio between longitudinal and average polarizability also increases gradually as Group 14 is descended, consistent with enhanced conjugation in the heavier oligomers. The localization of polarons in C-, Si- and Sn-core staffane radical cations was calculated along with internal reorganization energies. The polaron is less localized in Si- and Sn-core than in C-core staffane radical cation. The reorganization energies are also lower for the heavier staffanes, facilitating hole mobility when compared to the C-core staffanes. The effect of the bicyclic structure on the low valence excitations in the UV-spectra of compounds with two connected disilyl segments was also investigated. MS-CASPT2 calculations of 1,4-disilyl- and 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.2.1]heptanes and 1,4-disilyl- and 1,4-bis(trimethylsilyl)-1,4-disilabicyclo[2.1.1]hexanes revealed that although the bicyclic cage separates the two disilyl chromophores, there is a strong red-shift of the lowest valence excitations when compared to an isolated disilane.
Nyckelord
- Organic chemistry
- conjugation
- polarizability
- Group 14 elements
- cage compounds
- electronic excitations
- quantum chemistry
- molecular electronics
- Organisk kemi
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