Rotational couplings analysis

Restriction equations, molecular systems, component amplitude analysis, reciprocal relations, 215-217 Robb, Bemardi, and Olivucci (RBO) method, conical intersection location, 489—490 Rotational couplings ... 

The molecular motion of redox couples within polymer-coated electrodes has recently been investigated by making use of both nitroxide spin probes and various cationic spin probes [94-97]. Spin probes, such as the nitroxide probe TEMPO (see Sect. 2.1.2) and its derivatives, have well-defined electrochemistry and their ESR spectra in viscous media exhibit effects due to incomplete rotational averaging of the g and hyperfine coupling constant tensors. Analysis of the spectra [98] allows deductions to be made concerning the molecular rotation. Such analysis has been performed for spin probes incorporated into various polymer films. 

The interactions here describe molecular rotation, coupling of the spin and orbital angular momentum of any unpaired electrons, and hyperfine splittings, which result from the nuclei having spin. A more detailed discussion of these interactions can be found in (J). It should be recognized that analysis of molecular spectra can be very involved because of additional splittings in rotational levels due to electron and nuclear spins, i.e. relativistic effects. 

INDO calculations of coupling constants. ) Assignment may be reversed. ) Determination of barrier to internal rotation by analysis of linewidth effects between 373 and 610 K. ... 

Also, rotational state resolution of cross-sections can be obtained by employing a coherent state analysis [51] for the situation of weak coupling between rotational and vibrational degrees of freedom. A suitable rotational coherent state can be expressed as... 

If return occurs during the bromination of cw-stilbenes and rotation around the C-C bond is faster than collapse of the intermediates to dibromides, this process will lead to fra j-stilbene (Scheme 9). We used this test to check the possibility of return in the bromination of unsubstimted, 4-methyl, 4-trifluoromethyl-, and 4,4 -bis(trifluoromethyl)-stilbenes in DCE (ref. 24). All these olefins gave clean third-order rate constants spanning 7 powers of 10. For each cis-trans couple the cis olefin was brominated 3.5 to 5.5 times faster than the trans isomer. Reactions for products analysis were performed at initial molar ratios of Br2 to olefin of 1 to 2, so that products arose only from the cis olefin, the trans isomer being accumulated in the reaction medium. 

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