Separations, interplanar

As the N knee can have — 1 inner concentric knees, all of them separated by approximately the graphite interplanar distance, is called the graphite layer order . In fact, the number of atoms of the torus is given by 10(24 -l-33 —5n) because 10 atoms are common for adjacent knees at the (5 ,5 )-(5m,5h) connection (see below. Section 2.5). 

Another type of interaction is the association of radical ions with the parent compounds. Recently (118), a theoretical study was reported on the interaction of butadiene ions with butadiene. Assuming a sandwich structure for the complex, the potential curve based on an extended Hiickel calculation for two approaching butadienes (B + B) revealed only repulsion, as expected, while the curves for B + and B + B" interactions exhibit shallow minima (.068 and. 048 eV) at an interplanar distance of about 3.4 A. From CNDO/2 calculations, adopting the parameter set of Wiberg (161), the dimer cation radical, BJ, appears to be. 132 eV more stable than the separate B and B species, whereas the separate B and B species are favored by. 116eV over the dimer anion radical, BJ. This finding is consistent with experimental results formation of the dimer cation radical was proved in a convincing manner (162) while the attempts to detect the dimer anion radical have been unsuccessful. With other hydrocarbons, the reported formation of benzene dimer anion radical (163) represents an exceptional case, while the dimeric cation radical was observed... 

Figure 16. Interaction energy for two benzyl radical molecules approaching in two parallei planes as a function of the interplanar separation. Calculations (113) were...

Further examples of emissive cyclometallated gold(III) complexes are [Au(L)Cl] (L = tridentate carbanion of 4 -(4-methoxyphenyl)-6 -phenyl-2,2 -bipyridine) [53], as well as mono- and binuclear bis-cyclometallated gold(III) complexes, namely [Au (C N C )L ]" (C N C = tridentate dicarbanion of 2,6-diphenylpyridine L = depro-tonated 2-mercaptopyridine (2-pyS ), n = 0 L = PPh3 or 1-methylimidazole, n = 1) and [Au2(C N C )2(P P)](C104)2 (P P = dppm, dppe) respectively [54]. The crystal structures of the binuclear derivatives show intramolecular interplanar separations of 3.4 A between the [Au(C N C)] moieties, implying the presence of weak n-n interactions. The mononuclear complexes show absorption with vibronic structure at 380-405 nm (e > 10 cm ), attributed to metal-perturbed intraligand transition. 

The adsorption628 and ion exchange629-631 reactions of chiral [Co(en)3]3+ with clays have been studied. When the [Co(en)3]3+ ion exchanges with lamellar clays such as fluorhectorites, it increases the interplanar separation of the lamellae and influences the selectivity for intercalation of small molecules and atoms (H2, D2, Ne, and 02) within the clay over larger ones such as isobutane and neopentane.631... 

A above and below the inner N4 plane, respectively (which is coplanar to within 0.03 A). The molecules pack to form stepped polar stacks with a mean interplanar separation of 4.05 A, the adjacent pz ring centroids being separated by 6.27 A (Fig. 37). 

The peak separation in the non-dispersive setting between the substrate and layer reflections is measured call this. This is related to the change of interplanar spacing normal to the substrate through the equation d/d=- cot (3.1)... 

The problem of the variation in the surface energies of various crystal facets can be attacked from several points of view. Bravais first noted that those planes of a crystal which were most densely packed and were also separated most distantly from the neighbouring parallel plane were those which appeared most frequently in crystals he noted also that a closely packed surface was usually associated with a wide interplanar distance and vice versa. Later Willard Gibbs indicated that the most stable planes on a growing crystal were those possessing the least interfacial surface energy. 

In the excimer configuration the excited molecular states lZ, and 1Lb are each split into nondegenerate exciton states as shown schematically in Figure 11. The first-order perturbation energy A,Eexc at the equilibrium interplanar separation R0 is given by66... 

Matrix elements resonance integrals yS are evaluated as a function of interplanar separation R to obtain the values of R0 given in Table XIV (column 5) consistent with the spectroscopic data. 

Type B lattice preferred by these molecules is predisposed to excimer formation, although the absence of pronounced changes in the long-wave absorption spectrum indicates that the interplanar separation is reduced by photoassociation from the value108 of 3.5 A in the unexcited configuration. 

With an interplanar separation of 3.73 A, 4,4 -paracyclophane is the lowest member of the series to exhibit an alkylbenzene absorption spectrum and the broad structureless fluorescence spectrum of this molecule with a peak intensity at 3400 A is by definition an excimer band further separation of the aromatic rings in 4,5 and 6,6 -paracyclophanes restores the fluorescence spectrum to that of the alkylbenzenes. These observations by Rice et al.115 illustrate the critical nature of the interplanar separation in determining the extent of interaction between -electron systems in the ground and excited configurations. 

The close correspondence of the DNA absorption spectrum with that of a mixture of mononucleotides of the same composition illustrates the weak nature of the interactions between neighboring purine and pyrimidine bases guanine (G), cytosine (C), adenine (A), and thymine (T) at an interplanar separation of 3.36 A in the unexcited double-helical configuration. On the other hand the structureless fluorescence band of (calf-thymus) DNA is red-shifted by 3500 cm-1 from the fluorescence spectral origin of the mononucleotides it closely resembles the fluorescence spectrum of the dinocleotide ApT (and of poly dAT) and is accordingly identified131 with the fluorescence... 

The variation of the tensile stress with interplanar separation can be approximated by a sine cnrve of wavelength k (see Fignre 5.37), mnch like we did in Figure 5.10 for an applied shear stress [cf. Eq. (5.15)] ... 

The quantity Oc is called the theoretical cleavage strength (we will use the terms fracture and cleavage interchangeably here) and it is the maximum stress required to separate, or cleave, the planes. Since cleavage occurs at an interplanar separation of X = k 12, the work per unit area required to separate planes, also known as the strain energy, is the area under the curve in Figure 5.37 up to that point,... 

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