Donor-bound

Ligands with S donors in addition to N and or O donors bound to Co11 are reasonably large in number. For example, the 4-amino-3-alkyl-l,2,4-triazole-5-thione can bind Co11 as a chelate employing the primary amine and thione substituents on the five-membered ring,510 whereas the trifluoromethyl ligand (afmt) forms [Co(afmt)2(H20)2](N03)2, defined as the A -irons isomer... 

H NMR studies of the zinc complex formed with the hexadentate aniline functionalized triazacyclononane ligand (70) showed C3 symmetry in solution. It is suggested a six-coordinate complex is formed with all A-donors bound.664 This compares with the benzyl amino derivative,... 

The introduction of electronic deep levels is demonstrated in Fig. 9 with low-temperature photoluminescence spectra for n-type (P doped, 8 Cl cm) silicon before (control) and after hydrogenation (Johnson et al., 1987a). The spectrum for the control sample is dominated by luminescence peaks that arise from the well-documented annihilation of donor-bound excitons (Dean et al., 1967). After hydrogenation with a remote hydrogen plasma, the spectrum contains several new transitions with the most prominent peaks at approximately 0.95, 0.98, and 1.03 eV. These transitions identify... 

Hole trapping by electron donors bound to the surfaces of the semiconductor particles competes with the e - h+b recombination, allowing e b to react with molecular 02 via Eq. (10.23). Fig. 10.10 shows that the quantum yield, peroxide formation increases with increasing concentration of the electron donor. 

Characterization of the donor bound polymers follows from their spectroscopic (ir and uv-vis KBr) properties in comparison with the starting donor monomers, and from elemental analyses. That the donors are covalently bound to the polymer and not present as unreacted monomers can be seen by the absence of the characteristic monomer functional group absorption (i.e. -OH, COzH) in the donor bound polymer. For example in Figure 1, the comparative ir spectra of p-hydroxyphenyl-TTF monomer and this donor covalently bound to linear and to cross-linked polysytrene are given. Except for the presence of the hydroxyl absorption in the monomer, all three spectra are essentially identical, indicating a rather clean polymer attachment reaction. 

Electroactive donors, such as TTF or triarylpyrazoline, can be bound in high yield to polymeric matrices. The TTF linear polymers show interesting cooperative properties (i.e., ion-radical cluster formation) that is not observed for the isolated monomers in solution or the low coverage polymers. Furthermore, thin solid films of these donors bound to cross-linked polymer backbones display remarkably facile charge transport through the film bulk which is accompanied by dramatic and reversible optical changes. 

The unique seven-coordinate complex [TcO(EDTA)] is obtained by reaction of [TcOCy with H4EDTA in anhydrous dmso. The X-ray crystal structure confirmed pentagonal-bipyrami-dal geometry, with the 0x0 group and the two nitrogen donors bound in the equatorial plane. " All other structurally characterized technetium complexes with polyamino-polycarboxylates are in oxidation state IV. 

Structure with erythrose 4-phosphate bound a) U. Nilsson, L. Meshalkina, Y. Lindqvist, G. Schneider, /. Biol. Chem. 1997, 272,1864-1869 b) C. Wikner, U. Nilsson, L. Meshalkina, C. Udekwu, Y. Lindqvist, G. Schneider, Biochemistry 1997, 36, 15 643-15 649. c) model of donor bound G. Schneider, Y. Lindqvist, Biochim. Biophys. Acta 1998, 1385, 387-398. 

Fig. 2. Donor-bound solid-phase carbohydrate synthesis.

FIGURE 7.1 Synthetic strategies for oligosaccharide assembly on solid support, (a) Donor-bound strategy, (b) Acceptor-bound strategy, (c) Bidirectional strategy. 

Fig. 7.19. Photoluminescence spectra (2K) of PLD ZnO thin films on a-plane, c-plane, and r-plane sapphire substrates [63]. All films were grown at about 650°C and at 1.6 x 10 2 mbar oxygen pressure. The FWHM of the most intense donor bound exciton peaks D°X of the ZnO films are 1.4 meV on a-plane sapphire, 1.7 meV on c-plane sapphire, and 2.6 meV on r-plane sapphire. The spectral resolution of the PL setup was 1 meV at 3.35 eV...

Another feature clearly observed in FIGURE 1 is the sharp transition on the low energy side of the I2 line and labelled I2 (n = 2). It is interpreted as a two electron satellite of the donor bound exciton line, i.e. due to a recombination where the donor is left in its n = 2 excited state [6,19], From the 22 0.5 meV separation from the I2 line, a donor binding energy of 29 1 meV can be deduced [6,19], The weak transitions in FIGURE 1 at 3.27 and 3.18 eV, attributed to donor-acceptor pair recombinations, are discussed below. 

State-of-the-art, RMBE grown GaN/sapphire exhibits photoluminescence at 2 K which is dominated by a free A exciton (FEA), with visible transitions of excited FEAs and two excited FEBs, and linewidths are as narrow as 3 meV [47], Using GaN substrates for homoepitaxial RMBE growth, two donor bound excitons with an energy spacing of 0.9 meV have been resolved for the first time in low temperature photoluminescence (see FIGURE 3) [48], Additionally, the free C exciton becomes visible at about 80 K. 

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