77Se NMR

A number of zinc selenium complexes have now been characterized, with particular interest in the formation of zinc selenide semiconductors and quantum dots. In many cases analogous structures to those observed with thiol or thiolates are recorded. 77Se NMR is frequently used in characterization, and comparison with the sulfur equivalent is relevant. Zinc selenium compounds are of particular interest as precursors for metal/selenide materials and their relevance as models for selenocysteine-containing metalloproteins. 

A monomeric selenolato complex of zinc (65) was synthesized with a chelating oxazoline ligand.587 The complex was characterized by X-ray crystal structure, 1H, 13C, and 77Se NMR. These studies demonstrate that the compound is helically chiral and solution studies appear to show retention of chirality in solution. The zinc complex is tetrahedral with a Zn—Se average bond length of 2.378(1) A. 

Table 6 77Se NMR chemical shift of tetraphosphorylselenophene and related compounds...

Information about the surface and interface structures in hexadecylamine-capped CdSe NC of 2 nm size has been obtained by a variety of 1H, 13C, 113Cd, and 77Se NMR techniques [342]. The 77Se CP-MAS-NMR spectrum showed five partially resolved peaks from surface or near-surface Se environments. It was possible to obtain 2D heteronuclear correlation (HETCOR) spectra between 1H and the other three nuclei despite the inherent sensitivity limitations (the 77Se- 3I-I HETCOR experiment required 504 h ). The latter experiment indicated that the methylene protons of the hexadecylamine chain interact with the surface Se atoms via a tilt of the chain toward the surface. The surface Se atoms were not seen to interact with thiophenol present, and it was suggested that thiophenol binds to a selenium vacancy at the surface. 

The 77Se NMR spectra can be used to analyse the composition of a complex mixture of Se-N compounds. For example, 77Se NMR provides a convenient probe for analysing the decomposition of selenium(IV) diimides RN=Se=NR (e.g., R=tBu).30 An elegant application of 77Se NMR spectroscopy, in conjunction with 15N NMR spectroscopy, involved the detection of the thermally unstable eight-membered rings (RSeN)4.31... 

The 77Se NMR spectra provide an informative analysis of the components of the reaction mixtures in these syntheses of cyclic selenium imides. The five- and... 

Terminal selenido complexes 181 and 182156 with a tetracoordinate germanium atom displayed downfield shifted signals in 77Se NMR spectroscopy (S 77Se = 1023.8 and 1115.6 ppm vs Me2Se, respectively) comparable to... 

Se NMR of 2-phenylselenopropionates was introduced by Michelsen, Annby and Gronowitz1 More recently, Silks and co-workers developed the cyclic 2-oxazolidineselone as a far reaching... 

Figure 13.77Se-NMR spectra of a selected aliphatic long-chain carboxylic acid derived pair of diaslereomers and detection of optical purity in a deuterated phenylacetic acid derivative12.

The effects of 2- and 3-substituents on the 77Se NMR chemical shifts in selenophene and benzolb]selenophene have been investigated in detail (75CS(8)8, 8lOMR(l6)14). The 125Te shifts in 2-substituted tellurophenes exactly parallel the 77Se shifts in similarly substituted selenophenes (76CS(10)139>. 

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