Saddled Deformation

2 METHODOLOGY TO OBTAIN PURE INTERMEDIATE-SPIN COMPLEXES 

Five-coordinate iron(lll) porphyrins and porphyrin analogues discussed in this chapter together with their abbreviations. 

10 SPIN CROSSOVER IN IRON(III) PORPHYRINS INVOLVING THE INTERMEDIATE-SPIN STATE 

However, the contribution of the S = 3/2 in Fe(OETPP)l is difficult to estimate on the basis of the H NMRchemical shifts since the chemical shifts of the pure S = 3/2 complex are not known. In contrast, the EPR g values directly reflect the spin state pure high-spin complex should exhibit the gx signal at 6.0 while the pure intermediate-spin complex exhibits it at 4.0 [I 1,36]. Thus, the contributions of the 5 = 3/2 spin state, Int (%), in the mixed 5 = 5/2, 3/2 system estimated by Eq. (10.1) [36] are 5.0, 4.3, 89, 94, and 98% for the F, Cl, Br, I, and CIO4 complexes, respectively [34,37]. 

TABLE 10.1 HNMR and EPR Data of Five-Coordinate Fe(OETPP)X Carrying Anionic Axial Ligand(X)  

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Zo-Ao) 1 Transition state nucleus with saddle deformation S and (E - Ef) MeV of excitation, f Lifetime depends on E - Ef and is about 10"5 sec for thermal neutron capture... 

Fig. 5.16. Saddle deformation. The two principal curvature radii at point P, R and R2, are equal in absolute value but have opposite signs. The mean curvature ci +C2 is therefore zero, whilst the Gaussian curvature C1C2 is negative...

These results indicate that not only CIO4 but also the I and Br complexes adopt the nearly pure intermediate-spin state. The EPR data in Fe(OETPP)X are in sharp contrast to those in Fe(TPP)X since the latter complexes show the pure high-spin state regardless of the kind of the axial halides [26]. The results clearly demonstrate that the saddled deformation indeed stabilizes the intermediate-spin state as Cheng et al. pointed out [32]. 

The cavity in faujasite contains four tetrahedrally disposed windows. Molecular mechanics calculations [46,47] show that if the phthalocyanine ring system undergoes a saddle deformation then the four phenyl rings can poke through the tetrahedral holes and the host-guest complex exhibits no close van der Waals contacts. The resulting minimised structure is shown in Figure 5 [47]. This saddle distortion is compatible with the shift in the electronic spectra which indicates a distortion in the metal coordination sphere. 

Cq is the membrane intrinsic curvature, that is, the curvature of the membrane with zero deformation (e.g., a single layer of cylindrical molecules should have an intrinsic curvature of zero, but cone-shaped molecules will pack two dimensionally to have a curvature with no energy cost, k is the bending modulus, and is known as the saddle-splay modulus. As we can see in Figure 3.10, it is quite possible to have a curved membrane with a mean curvature of zero in the case of saddle-like deformations. Therefore, it becomes clear that to describe the energy cost of a saddle deformation the extra terms are necessary. 

At a critical length that depends on relative laminate thickness, the deformation solution trifurcates at point T, i.e., above the critical length, three possible room-temperature shapes exist (1) a saddle shape, (2) a cylindrical shape with Kj, = -i- k and Ky = 0, and (3) a cylindrical shape with k, = 0 and Ky = - k. For this 102/902)x laminate, the critical length is 35 mm. 

One of the two most common nonplanar deformations of the porphyrin ligand is the saddle conformation in which the pyrrole Cp—C bonds are displaced alternately above and below the mean 24-atom plane. The other is the ruffled conformation in which the Cmeso carbon atoms are displaced alternately above and below the mean 24-atom plane with concomitant twisting of the pyrrole rings. There are various measures for the extent of mffling for example, the C eso cross-ring distance decreases and the mean displacement of Cmeso from the mean 24-atom plane increases as the structures become more ruffled. The average M—N... 

Fig. 4. (a) Anticlastic deformation of a bimorph in a magnetic field (saddle form), (b) Fixation of a bimorph on its sample holder and measurement principle of the deformation of any magnetostrictive bimorph using the... 

Fig. 8A shows that the selectivity for ketone and alcohol formation is quite similar for both molecular sieves. Fig. 8B indicates that regioselectivity exists for both molecular sieves, possibly due to the encaged nature of the complex. However, lower values of the C2/C3 and C2/C4 ratios are obtained in VPI-5 compared to zeolite Y, pointing to the existence of shape selectivity. The molecular graphics analysis, which enabled quantification of the free pore apertures, shows that the difference in selectivity can hardly be caused by differences in the zeolitic environment. The enhanced constraint observed for FePcY should then be related to the saddle-type deformation of the complex. 

If c remarkably differs from zero then there are three equivalent minima and three equivalent saddle points on the trough of the deformed Mexican hat [see equation (3)], which are described by different signs in equation (3) for V. Therefore one can observe two ZPL, which corresponds to transitions into the vicinity of a minimum and into vicinity of a saddle point. The frequency difference of these lines is v2 c j(yv c2)- The lower frequency line corresponds to the optical transition into a minimum, which is dynamically stable. The higher frequency line corresponds to the optical transition into a saddle point, which is dynamically unstable. The temperature dependence of these lines at low temperatures are described by equations (15) and (16) with w= — (wj 9Id) (the sign + in the brackets corresponds to the line with higher frequency). The width of the line with lower frequency at T = 0 is equal to zero the width of the higher frequency line at T = 0 differs from zero it is described by equation (17) with wcr — w = 9 c. ... 

Shrinkage may also be anisotropic, namely when chain orientations are present. As discussed in Chapter 5, these orientations result from rubber-elastic deformations in the melt they are, therefore, found in parts where the melt has been rapidly cooled under conditions of a high rate of strain. Shrinkage is higher in the orientation direction than across, so that, for instance, a flat disk, injected from its centre, tends to deform into a saddle-like shape (warping). 

Here the index s runs over the relevant saddle points, those that are visited by an appropriate deformation of the real integration contour, which is the real five-dimensional (t,t, k) space, to complex values, and Sp(t,t, k) s denotes the five-dimensional matrix of the second derivatives of the action (4.5) with respect to t,t and fc, evaluated at the saddle points. The time dependence of the form factors (4.6) and (4.7) is considered as slow, unless stated otherwise (see Sect. 4.5 and [27]). 

The porphyrinic complexes are all essentially planar. However, the simple porphyrin and tbp macrocycles are somewhat flexible, and can adopt a ruffled, or saddle-shaped distortion through twisting at the methine carbon atoms. These deformations cause almost negligible changes in electronic structure, but the conformational mobility offers an added element of subunit variability. 

Intranasal use, a common method of cocaine abuse, can damage the sinonasal tract, causing acute and chronic inflammation, necrosis, and osteocartilaginous erosion (SEDA-17, 36). These conditions occur secondary to the combined effects of direct trauma from instrumentation, vasoconstriction of small blood vessels with resultant ischemic necrosis, and chemical irritation from adulterants. Intranasal cocaine users can develop septal perforation, saddle-nose deformities, and sinonasal structural damage. 

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