Chromophores tetrahedral

Cobalt as a Colorant in Ceramics, Glasses, and Paints. Cobalt(II) ion displays a variety of colors in soHd form or solution ranging from pinks and reds to blues or greens. It has been used for hundreds of years to impart color to glasses and ceramics (qv) or as a pigment in paints and inks (see CoLORANTS FOR CERAMICS). The pink or red colors are generally associated with cobalt(II) ion in an octahedral environment and the chromophore is typically Co—O. The tetrahedral cobalt ion, Co—chromophore, is sometimes green, but usually blue in color. 

Reinen and Grefer (116) have measured the d—d spectra of distorted tetrahedral Cu04 chromophores in mixed oxides. This work concerns copper-doped lattices such... 

Bazan and co-workers [93] coupled four branches of stilbene chromophores to a central C atom, leading to tetrastilbenylmethane [C(STB)4, 46a] tetrakis (4-ferf-butylstyryIstiIbenyljmethane [C(f-BuSSB)4, 46b], and the higher homolo-gue tetrakis 4-[4 -(4"-terf-butyl-styryl)styryl]stilbenyl methane [C(4R—f-Bu)4, 46c]. For 46b, Tg is 190°C, and for 46c it is as high as 230°C. Tetrakis(4,4 -2,2-diphenyl-vinyl)-l,l -biphenyl]methane [C(DPVBi)4, 47a] and the cyano derivative 47b exhibit the glass transition at 142 and 174°C, respectively. Similar compounds to 46a and 46b have also been synthesized with silicon and adaman-tane as the tetrahedral center. 

Even lower temperatures have been used to study possible intermediate stages in the formation of the acyl enzyme. A tetrahedral intermediate (with a covalent bond between the substrate carbonyl carbon atom and the oxygen atom of the active site serine) (Fig. 2) had been suggested by analogy with nonenzymatic reactions. With rapid reaction techniques, spectrophotometric evidence has been obtained for an additional intermediate before the acyl enzyme in the case of chromophoric substrates. By using first the protein fluorescence emission (Fink and Wildi, 1974)... 

Klessinger M, Liittke W (1963) Theoretical and spectroscopi investigation of indigo dyes II. The chromophore system of the indigo dyes. Tetrahedr Lett 19 (suppl. 2) 315-335. 

The separation of the four possible isomers of [VO(acpn)] (67 R1 = R2 = R = Me, X = H) SX, Sd, RX, R6 (compare with Scheme 18) was claimed.743,744 The 02N2 chromophore is not planar but has a slight tetrahedral distortion and the CD spectra suggest that the corresponding chirality has A absolute configuration for diamines of S or S,S absolute configuration.725... 

Reaction of the five-coordinate [NiX(np3)]X complexes with MX2 salts (M = Fe, Co, Ni, Zn) affords mixed complexes NiM(np3)X4 containing a square planar NiNP2X chromophore and a tetrahedral MPX3 chromophore.1433... 

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