Electronic spectra acids

Dibenzothiophene acts as a 7r-electron donor and readily forms complexes with known electron acceptors. In such cases the electronic spectrum of a solution of the two compounds shows a new absorption band, usually in the visible region. The order of donor strengths of several o,o -bridged biphenyls has been estimated from their respective charge-transfer spectra and found to be carbazole > fluorene > dibenzothiophene >dibenzofuran. Dibenzothiophene forms complexes with tetracy-anoethylene, various polynitro derivatives of fluorenone, > naphthalene-1,4,5,8-tetracarboxylic acid dianhydride, and tetra-methylmic acid. ... 

N-Do/Jor Ligands. The full account of the preparation and properties of V[N(SiMc3)2]3 has been published. (Et4N)3[V(NCSe)e] has been prepared and its electronic spectrum reported in several solvents. The electronic spectra of fVL lfNCSij complexes (L = py, 3-picoline, 3,4-lutidine, or 3,5-lutidine) are consistent with tetrahedral microsymmetry about the V " atom, and the magnetic properties of V complexes with the thiosemicarbazones of salicylaldehyde and pyruvic acid have been interpreted in terms of a tetragonal environment about the metal. ... 

The complexes [Ru(bpy)2L]+ (HL = acetylacetone, trifluoroacetylacetone, hexafluoroacetylace-tone, tropolone or dibenzoylmethane) have been prepared and characterized they act as catalysts for the oxidation of alcohols, 3,5-di-tert-butylcatechol and alkanes in the presence of appropriate co-oxidants." Perchlorate salts of [Os(bpy)2L] in which HL = salicylaldehyde, 2-hydroxyaceto-phenone or 2-hydroxynaphthaldehyde, are formed from reactions of [Os(bpy)2Br2] with HL. The structure of the salicylaldehyde derivative has been determined. Chemical and electrochemical oxidations of [Os(bpy)2L]" yield the corresponding low-spin Os species from which [Os(bpy)2L]+ can be regenerated." " [Ru(bpy)2L]" (HL = salicylic acid) has been prepared and structurally characterized as the tetrahydrate. Absorptions at 590 nm, 400 nm, and 290 nm in the electronic spectrum have been assigned to Ru bpy CT transitions electrochemical oxidations of the complex have been investigated." ... 

The meso-tetraphenylporphyrin complex [Zr(TPP)Cl2] has been prepared by reaction of H2TPP with ZrCl4 in boiling benzonitrile. The electronic spectrum of [Zr(TPP)Cl2] and the facile kinetics of TPP dissociation in acidic media suggest that the zirconium atom lies considerably out of the plane of the TPP ligand with both chlorine atoms being located on the same side of the TPP plane.708... 

The electronic spectrum of vanadium(III) ions in concentrated sulfuric acid with Amai at... 

The synthesis of the isomers of [Cr(CN)2(en)2]+ is discussed in Section 35.4.2.3. Like the previously mentioned cyanoammine complexes, ay-[Cr(CN)2(en)2]+ is quite labile in acid solution.327,328 This behaviour contrasts markedly with that of cij-[Co(CN)2(en)2],+ which undergoes no apparent decomposition over a period of five days at 80 °C in aqueous acid.327 The addition of Ag+ to an aqueous solution of cis-[Cr(CN)2(en)2]+ results in ligand isomerization, equation (28), and formation of adduct (86) which has an electronic spectrum... 

Malonic acid CH2(C02H)2 (H2mal) (209) has a coordination chemistry with chrommm(III) closely resembling that of oxalate. Malonic acid is a slightly weaker acid than oxalic acid and slightly more labile complexes are formed. The tris complex is the most extensively studied, prepared by the reduction of chromate solutions or the reaction of chromium(III) hydroxide with malonate.917,918 919 The cis and trans diaqua complexes may be prepared by the reduction of chromate with malonate the isomers are separated by fractional crystallization. The electronic spectrum of the tris complex is similar to that of the tris oxalate and a detailed analysis of these spectra has appeared.889... 

Two unusual rubredoxins are known at present, from D. gigas and Pseudomonas oleovorans. Both have two iron centres but differ from each other. The rubredoxin from D. gigas (desul-foredoxin) has a molecular weight of 7900, with no acid labile sulfide and eight cysteine residues.744 The electronic spectrum is different from that of the two-iron rubredoxin from P. oleovorans in that it is not simply the addition of two spectra of one-iron rubredoxins. These additional features have led to the suggestion that the two iron centres interact. 

Four different synthetic procedures have been examined for the preparation of the triphenyl derivative, the fourth one suggested by the synthetic conditions developed to obtain the diphenyl derivatives. In the first three procedures it has been impossible to isolate the triphenyl-dihydrobilin. Its formation has been demonstrated, however, by monitoring the electronic spectrum of the reaction mixture and the cyclization to corrole has been carried out in situ. The synthesis that gave the highest yield (20%) and that avoids tedious purification procedures is outlined in Fig. 10. It involved the acidic condensation of benzaldehyde with two equivalents of 3,3, 4,4 -tetramethyl-meso-phenyl-dipyrromethane-5,5 ... 

However, the electronic spectrum of dark green bi(cyclohepta)pyr-role 262 dissolved in tetrafluoboric acid shifts hypsochromically to become, ultimately, identical with the spectrum of tropylium salt 263 (75TL1849). A strong shift in the same direction is observed with acidified... 

The enzyme contains six identical subunits (M = 96600) arranged in the form of an octahedron. Each subunit contains two tightly bound nickel ions (% nickel = 0.12). After the electronic spectrum of the enzyme has been corrected for light scattering the d-d bands associated with nickel(II) at 407, 747 and 1060 nm are consistent with nickel in an octahedral environment. In the presence of acetohydroxamic acid the... 

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