Zinc selection rules

Birman, J. L. (1962) Space group selection rules, diamond and zinc blende. Phys. Rev. 127, 1093-106. 

For CD transitions the selection rules are not as clearly defined. However, more complex CD spectra were anticipated for the Co(III) azophenols than for the Zn(II) azophenols due to the overlap of d-d and ligand transitions. Since Zn(II) has no d-d transitions a relatively simple CD spectrum is expected in the visible region as is observed for the zinc complex in AA-CPA-Zn, Figure 4 (pH 8.3 spectrum). 

Figure 4 Selection rules for the absorption of Icp and rep light based on a transition between an orbitally nondegenerate ground state and an orbitally degenerate excited state within a magnetic field applied parallel to the axis of light propagation (a). A derivative-shaped Faraday Ai term is observed due to the Zeeman splitting of states and the associated energy separation of bands based on the AMl = 1 selection rule (b). (Reprinted from Mack, Stillman and Kobayashi, Elsevier 2007.) We note that in this example, since 5 = 0 for closed shell atoms or molecules, J = L, and Mj = Ml. Absorption and MCD spectra of zinc octaethylporphyrin (ZnOEP) in CHCI3 (c). The MCD spectrum is dominated by derivative-shaped Ai terms. (Reproduced with permission from J. Mack, Y. Asano, N. Kobayashi, M. J. Stillman, J. Am. Chem. Soc., 2005,127, 17697-17711. 2005 American Chemical Society)...

The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism pla dng a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed. 

Use of the alternative methods whose selection rules admit of spectral activity of the LO modes. One such method is polarized Raman spectroscopy, which is applicable to substances with cubic zinc blend and hexagonal wurtzite structures such as ZnS, ZnSe, CdS, ZnO, ZnTe, and the III-V compounds (see Refs. [47-49] and literature cited therein). The most direct method to measure vlo is inelastic neutron scattering (INS) since there are no selection rules for INS spectroscopy and as a result all modes are allowed [50, 51]. 

J Birman. Theory of infrared and Raman processes in crystals selection rules in diamond and zinc blende. Phys Rev 127 1489, 1967. 

Figure 3.4 Band structure and selection rules for zinc blende and wurtzite structures. Crystal-field and spin-orbit splittings are indicated schematically. Transitions that are allowed for various polarizations of photon electric field vector with respect to the c-axis are indicated. (After Ref [40].)...

Although the rationalization of the reactivity and selectivity of this particular substrate is distinct from that for chiral ketals 92-95, it still agrees with the mechanistic conclusions gained throughout the study of Simmons-Smith cyclopropa-nations. StOl, the possibility of the existence of a bimetallic transition structure similar to v (see Fig. 3.5) has not been rigorously ruled out. No real changes in the stereochemical rationale of the reaction are required upon substitution of such a bimetallic transition structure. But as will be seen later, the effect of zinc iodide on catalytic cyclopropanations is a clue to the nature of highly selective reaction pathways. A similar but unexplained effect of zinc iodide on these cyclopro-panation may provide further information on the true reactive species. 

The specific heat capacities of the metals nickel, zinc, rhodium, tungsten, gold, and uranium at 25°C are 0.444, 0.388, 0.243, 0.132, 0.129, and 0.116 J K g respectively. Calculate the molar heat capacities of these six metals. Note how closely the molar heat capacities for these metals, which were selected at random, cluster about a value of 25 J K mol b The rule of Dulong and Petit states that the molar heat capacities of the metallic elements are approximately 25 J K moUb... 

An exception to this rule is galactose oxidase, also known to be a good F relaxation probe, but this enzyme is present only in certain fungi (Marwedel et al., 1975). Since manganese and copper/zinc superoxide dismutase can be discriminated in mixtures containing both enzymes by the selective inhibition of the latter one by cyanide, the relaxation can... 

The use of variable-valence metal compounds as catalysts, as a rule, is accompanied by a decrease in the selectivity of the oxidation of cumene to the hydroperoxide, mainly due to the formation of cumyl alcohol upon the decomposition of CH [35, 36], An increase in the reaction rate witii retention of high selectivity up to cumene conversion of 35-40% is observed at oxidation of cumene when zinc and cadmium complexes of N-heterocyclic bases are used as catalysts [37],... 

The influence of further counter-ions like ammonium, magnesium and zinc on the reversibility has been studied [65, 71]. Another influence comes from the stability of the enolate. As a rule, the rate of the retroaldol reaction correlates vith the stability of the enolate. In stereoselective aldol addition, the reversibility is, in general, rather considered as a complication than a tool to obtain high selectivity. In particular, thermodynamically controlled aldol additions are usually not suitable to obtain non-racemic aldols. 

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