Q-structure

These and many similar examples resulted in a highly successful general picture of transition-metal ions M coordinated by closed-shell ligands L (anionic or neutral) to form complex cluster ions [ML ]9 in solution. The characteristic coordination shell of each M corresponds to a specific number of sites, with idealized geometry that dictates the possible number of distinct [M(Li) (L2)m. .. ]q structural isomers. Each cluster ion is subject to equilibria with other cluster ions or dissociated ligands in solution,... 

Fig. 15 2D diffraction pattern from a quasi-single-crystal of Sc-II at 48 GPa. The relative spacing of the layers of reflections from the host (hkl) and guest (hld)Q structures (compare to Fig. 14), and the presence of the (OOl) guest reflection confirms the guest structure to be C-centred... 

Inorganic Chemistry Principles q/ Structure and Reactivity, Fourth Edition Copyright 1993 by HarpecCollins College Publishers... 

Boger DL, Patterson JE, Jin Q. Structural requirements for 5-HT2A and 5-HT1A serotonin receptor potentiation by the biologically active lipid oleamide. Proc Natl Acad Sci USA 1998 95 4102-4107. 

S(q) structure factor describing interaction between solute molecules... 

For the open-chain C2 structure (23) in Scheme 8 is the global minimum. It is favored by 36kJmol over the complex Q structure (25) and 45kJmol over the Cj ring structure (24). The activation energy for the decomposition was calculated to be SkJmor for the open-chain structure (23), which decomposes to the azide anion and two molecules of dinitrogen and to ISkJmol for the ring stracture (24). ... 

The halogen nitrates have planar Q structures (see Table 41). The dissociation to XO and NO2 gets easier from fluorine to iodine. 

Karpfen, A., and Yanovitskii, Q., Structure and vibrational spectra of neutral, protonated and deprotonated hydrogen bonded polymers an ah initio SCF study on chain-like hydrogen fluoride clusters, J. Mol. Struct. (Theochem) 307, 81-97 (1994). 

Theoretical calculations on a model system have predicted that the ground-state conformation of the anion is the pyramidal Q structure (Fig. 5) (62). It is noteworthy that the C, structure has unusually long C-Si bonds and a butadiene-like geometry of the carbon skeleton. The planar Qu form is the transition state for pyramidal inversion between equivalent Cj structures, the inversion barrier being 16.2 kcal/mol (6-31 G ). 

Kouns WC, Newman PJ, Puckett KJ, et al. Further diaracterizadon of the h>q> structure of platdet glycoprotdn Ilia partial mapping of functionally significant glycoprotein Hla epitopes. Blood 1991 78 3215-3233. 

As both samples have a f.c.c. structure of equal unit-cell dimensions, it is apparent that the K3C q structure is based on a f.c.c. lattice of C o molecules, with K atoms inserted into empty spaces. The possibility of incorporating alkali ions into these sites was noted previously by Haddon ei aC. The clearest difference between the Cf and the K.3C60 diffraction patterns occurs in the relative intensities of the strongest few peaks, most notably (220) and (311). It is therefore evident that the sites occupied by K interfere destructively and constructively with the C atoms, respectively, for these two reflections. This immediately suggests that the K. occupy sites such as (4,3, ) or (5,0,0), shown in Fig. 3. The fact that the stoichiometry... 

Most of the applications of Si NMR to glass studies to date have been used to provide information about the nature and relative numbers of the Q" structural units present. Another important structural detail is the way in which these units are connected together in the glass. Developments in two-dimensional Si NMR have allowed such... 

Evidence for M-Ng bonds is not confined to 16-electron species. The 17-electron complex, Mn(CO)s, exhibits a similar Q, structure to CrfCOjs. That it binds to noble gases can be demonstrated by hyperfine coupling to a single krypton nucleus ( Kr, I = 9/2) in its EPR spectrum in a krypton matrix. Similar effects were observed in the spectrum of isoelectronic [Fe(CO)s]. These species were generated by radiolysis of HMn(CO)5 and Fe(CO)s, respectively, not by photolysis. 

Q Structural Changes of Multiphase Food Systems Generated by Proteins... 

Reaction of [Fe" salen] with p-quinones gives, in contrast, the binuclear complexes [Fe2(salen)2Q]. It was shown by a variety of properties (magnetic measurements and IR, ESR and Mossbauer spectra) that the compounds consist of high-spin Fe" ions bridged by the dianion Q (structure 33) of the hydroquinone which transmits weak ( — J< 6cm ) antiferromagnetic interaction. This structure has been confirmed, for the case of Q = the dianion of hydroquinone, by a single crystal structure determination. ... 

Molecules like 02H take the nonplanar Q structure (twisted about the 0-0 bond by ca. 90"), whereas N2F2 and [N203] exist in two forms /mm-planar (C2/,) and cis-planar (C21.). Figure 11-7 shows the six normal modes of vibration for the C2, and C2 structures. The selection rules for these two structures are different only in the vibration, which is infrared inactive and Raman depolarized in the planar model but infrared active and Raman polarized in the nonplanar model. 

Q Structure and Property Modifications by Ion Implantation in Metal Oxide Thin Solid Films Suitable for Gas Sensing Applications... 

FIGURE 59.1 Representations of Q" structures in silicates. The oxygen atoms are shown without H atoms or charges. Each silicon center is at the center of a Si04 tetrahedron. Tetrahedra only form linkages at vertices to form oligomers and polymers. 

Silicone resins and rubbers ctre cross-linked polymers with branched polymer chains containing M (monofunctional), D (difunctional), T (trifunctional), and Q (tetrafunctional) units. Slightly branched polymers made from D, T, and Q structures have lower bulk viscosity and intrinsic viscosity than linear polymers of the same average molecular weight. 

The redox potentials ofQ are more negative than those of analogous Q. Structural and spectroelectrochemical investigation of [Ru(NO)(Qx) (terpy)] confirm the oxidation state assignment [Ru (NO )(Q5c ) (terpy)] for the isolated paramagnetic material (16). Variable frequency (9 and 285 GHz) EPR data and DFT calculations surest a rather small contribution by the NO" ligand form, while the iminosemiquinone-based reduction leads to the diamagnetic [Ru (NO )(Q , )(terpy)] (16) with a shift of Ai> = 70 cm. ... 

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