1027657-14-2Relevant academic research and scientific papers
Synthesis of a variety of bichromophoric "ball-and-chain" systems based on buckminsterfullerene (C60) for the study of intramolecular electron and energy transfer processes
Lawson, James M.,Oliver, Anna M.,Rothenfluh, Daniel F.,An, Yi-Zhong,Ellis, George A.,Ranasinghe, Millagahamada G.,Khan, Saeed I.,Franz, Andreas G.,Ganapathi, Padma S.,Shephard, Michael J.,Paddon-Row, Michael N.,Rubin, Yves
, p. 5032 - 5054 (1996)
Diels-Alder reaction of C60 with the 1,3-dienes 7e-h, 8a, 8b, and 8d-h affords the "ball-and-chain" systems 2e-h, 3a, 3b, and 3d-h bearing two chromophores linked via a rigid, hybrid saturated polynorbornane-bicyclo[2.2.0]hexane ("norbornylogous") hydrocarbon bridge. Analogous reaction with the bis(diene) 9 affords the soluble dumbbell system 4 bearing two C60 chromophores. The norbomylogous bridge is a strong mediator of electron and energy transfer via a through-bond coupling mechanism. The norbomylogous donor-bridge-diene units 7d-h, 8a, 8b, and 8d-h were prepared in a straightforward manner from bicyclo[2.2.2]octane precursors by extending the bridges with linearly fused norbornane-bicyclo[2.2.0]hexane moieties through execution of the tandem Mitsudo-Smith series of reactions. The X-ray structure of the dimethoxybenzene-bridge-C60 system 3a reveals favorable self-complementarity manifested by the unusual packing structure of 3a in the crystal. Molecular mechanics, semiempirical, and ab initio conformational analyses of compounds 2e, 3a, 3b, 3e, 3f, 3h, 68, and 70 (MM2, Sybyl, CVFF, AM1, HF/3-21G) were performed to quantify their ability to adopt two nondegenerate boat conformations, i.e., extended and folded conformers, as well as their kinetic barrier of interconversion. A similar treatment of the C60-bridge - C60 system 4 revealed unusual preference for the folded-folded conformer (18.9 kcal/mol at CVFF level), which was not reproduced by the AM1 method (0.11 kcal/mol). The reduction potentials of the systems 2e, 3a, and 3e were about 0.1-0.5 V more negative than C60, and the third reduction potential (E3) of the 6-bond system 2e was 0.14 V more negative than the corresponding wave for the 10-bond system 3e. This shift was attributed to the closer proximity of the dimethylaniline donor group to the C60 surface for 2e vs 3e.
