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Author Strohmeier, Mark ♦ Barich, Dewey H. ♦ Grant, David M. ♦ Miller, Joel S. ♦ Pugmire, Ronald J. ♦ Simons, Jack
Source CiteSeerX
Content type Text
File Format PDF
Subject Domain (in DDC) Computer science, information & general works ♦ Data processing & computer science
Subject Keyword Solid-state Nmr Spectrum ♦ Long Intradimer Bond ♦ Electronic Structure ♦ Central Cdc Bond ♦ Experimental Ethylenic Chemical-shielding Tensor ♦ Systematic Study ♦ Out-of-plane Component ♦ Nmr Chemical-shift Tensor Value ♦ Charge Density ♦ High Sensitivity ♦ Several Related Tcne-based Structure ♦ Determined Principal Chemical-shift Value ♦ Minimal Dependence Of-2 ♦ Approximately-43 Ppm ♦ Atypical Chemical Specie ♦ Shift Dependence ♦ Dimer Anion ♦ Principal Tensor Component ♦ Molecular Plane ♦ Chemical-shift Value ♦ Nuclear Shielding Tensor ♦ Tensor Magnitude ♦ C-c Bond Length ♦ Theoretical Method ♦ Several Oxidation State ♦ Molecular Frame ♦ Density Functional Theory ♦ Electronic Configuration ♦ About-111 Ppm ♦ Singlet State ♦ Monomeric Unit ♦ Monomer Unit ♦ Monomer Molecular Plane ♦ Electron Plane
Abstract The principal 13C chemical-shift values for the ð-[TCNE]22- dimer anion within an array of counterions have been measured to understand better the electronic structure of these atypical chemical species in several related TCNE-based structures. The structure of ð-[TCNE]22- is unusual as it contains two very long C-C bond lengths (ca. 2.9 Å) between the two monomeric units and has been found to exist as a singlet state, suggestive of a 1A1g (b2u2b1g0) electronic configuration. A systematic study of several oxidation states of [TCNE]n (n) 0, 1-, 2-) was conducted to determine how the NMR chemical-shift tensor values change as a function of electronic structure and to understand the interactions that lead to spin-pairing of the monomer units. The density functional theory (DFT) calculated nuclear shielding tensors are correlated with the experimentally determined principal chemical-shift values. Such theoretical methods provide information on the tensor magnitudes and orientations of their principal tensor components with respect to the molecular frame. Both theoretical and experimental ethylenic chemical-shielding tensors reveal high sensitivity in the component, ä⊥, lying in the monomer molecular plane and perpendicular to the ð-electron plane. This largest shift dependence on charge density is observed to be about-111 ppm/e- for ä⊥. The component in the molecular plane but parallel to the central CdC bond, ä , exhibits a sensitivity of approximately-43 ppm/ e-. However, the out-of-plane component ä′ ⊥ shows a minimal dependence of-2.6 ppm/e- on the oxidation
Educational Role Student ♦ Teacher
Age Range above 22 year
Educational Use Research
Education Level UG and PG ♦ Career/Technical Study
Publisher Date 2006-01-01