Molecular dipole delocalized

Specifically, for the calculation we choose a dimer model consisting of opposed molecular dipoles bound by a delocalized electronic charge, having a center of gravity lying between the positive ends of the original molecular dipoles. For example, the simplest case, (HF)2 , could be written diagramatically as ... 

Antibonding molecular Dipole moment (/u), p. 420 orbital, p. 440 Homonuclear diatomic Bond order, p. 444 molecule, p. 445 Bonding molecular Hybrid orbital, p. 428 orbital, p. 440 Hybridization, p. 428 Delocalized molecular Molecular orbital, p. 440 orbital, p. 449 Nonpolar molecule, p. 421 Pi bond (77 bond), p. 437 Valence-shell electron-pair Pi molecular orbital, p. 443 repulsion (VSEPR) Polar molecule, p. 421 model, p. 410 Sigma bond (cr bond), p. 437 Sigma molecular orbital, p. 441 Valence shell, p. 410... 

NBO analysis of the molecular dipole moment is requested by inclusion of the DIPOLE keyword in the NBO keylist. As a simple example, we consider the formamide molecule (Section 4.13), whose nonvanishing dipole components all lie in the x-y molecular plane. Results of DIPOLE analysis for formamide are shown in 1/0-6.3, slightly truncated (by inclusion of the DIPOLE = 0.05 keyword) to include only delocalization corrections exceeding 0.05 D (rather than default 0.02 D) ... 

Figure 6.8 Similar to Fig. 6.7, for the NBO bond dipole geometry of formamide. Each NBO bond dipole (light arrows) is shown with its delocalization correction (light dotted lines), resulting in the same total dipole moment (heavy solid arrow) as in Fig. 6.7. The resultant sum of NBO dipoles is own as the heavy dashed arrow and the resultant delocalization correction as the heavy dotted line. Note the large dipole reorientation due to resonance-type delocalizations, which twist the final molecular dipole significantly out of parallelism with the C=0 double bond.

The n values were high for all of the ionic liquids investigated (0.97-1.28) when compared to molecular solvents. The n values result from measuring the ability of the solvent to induce a dipole in a variety of solute species, and they will incorporate the Coulombic interactions from the ions as well as dipole-dipole and polarizability effects. This explains the consistently high values for all of the salts in the studies. The values for quaternary ammonium salts are lower than those for the monoalkylammonium salts. This probably arises from the ability of the charge center on the cation to approach the solute more closely for the monoalkylammonium salts. The values for the imidazolium salts are lower still, probably reflecting the delocalization of the charge in the cation. 

Figures 3a and 3a depict the weak bond of an O2 molecule with the lattice. It is formed by an electron being drawn from an ion of the lattice to an O2 molecule. Owing to the greater electron aflSnity of the O2 molecule, the electron may be considered completely transferred from the lattice to the molecule as a result, a molecular ion 02 is formed and a localized hole appears in the lattice attached to the ion Oi, The entire system (the adsorbed O2 molecule + adsorption center) acquires a noticeable dipole moment with negative pole directed outward, but remains electrically neutral as a whole. The bond is effected without the participation of a free lattice electron. The transition to a strong acceptor bond entails the localization of an electron, or, what amounts to the same thing, the delocalization of a hole. Such a strong acceptor bond is depicted in Figs. 3b and 3b. ...

Figures 6 and 7 show absorption and electroabsorption spectra of [ (NH3)5Ru 2(/A-pyz)]5+ and [ (NH3)5Ru 2(M,4 -bpy)]5+, respectively. The change in AA as a function of x is uniform for the bands, which indicates that the molecular properties that give rise to AA are identically oriented with respect to the transition dipole moment. The electroabsorption spectra in the near-IR region (MMCT bands) give the greatest differences between complexes when analyzed with Eq. (31) and these are shown in Fig. 8. For the Creutz-Taube ion (Fig. 8A), the spectrum does not satisfactorily reduce to a sum of derivatives but nevertheless shows that AA(p) line shape to be modeled primarily by a negative zeroth derivative (Ax) term, especially at energies below 6500 cm-1. The fit in this case yields a value for Ap. = 0.7 0.1 D, which when compared with the maximum permanent electric dipole moment ( A/u max = 32.7 D, assuming a metal-to-metal distance) is strong evidence for a delocalized ground state. Contrast this result with the analysis of the electroabsorption spectrum of [ (NH3)5Ru 2(ja-4,4 -bpy)]5+ shown in Fig. 8B.

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