1,3-diketone chelates

The photochemistry of transition metal 1,3-diketone chelate complexes has been known for some time [30,31], and their photophysical and photochemical properties and photocatalytic activity in different chemical reactions were reviewed in 1990 by Marciniak and Buono—Core [32]. Further discussion on the photochemistry of meta] chelate will not take place here since this subject is out of the scope of this chapter. 

The photochemistry of true organomagnesium compounds remains almost completely unexplored. A literature search in preparation of this work found only a few scattered examples of photochemical studies, mostly in relation to Grignard reactions and 1,3-diketonate chelates Similar to the situation with organozinc compounds magnesium tetrapyrrole chelates, i.e. magnesium porphyrins 1, 5,10,15,20-tetraazaporphyrins (por-phyrazines) 2 and phthalocyanines 3 have found more interest. This is primarily related... 

Geometrical isomerism is potentially possible among many of the lanthanide chelates. The 1,3-diketone chelates, the species derived from the aminepolycarboxylic acids, the tropolonates, and many other complex derivatives are asymmetric and, thus, potentially capable of exhibiting optical isomerism. That the only resolutions reported have been limited to some tris (diketone) compounds (35) may refiect more the tendency of these ionically-bonded species to racemize rapidly in polar environments than in the absence of asymmetry. The existence of more than a single modification of each of several tetrakis(di-keto)europium(III) compounds may refiect asymmetry also (1). 

P-Diketone Chelates. P-Diketones, reacting as enols, readily form chelates with titanium alkoxides, Hberating in the process one mole of an alcohol. TYZOR AA [17927-72-9] (6) is the product mixture from TYZOR TPT and two moles of acetylacetone (acac) reacting in the enol form. The isopropyl alcohol is left in the product (87). The dotted bonds of stmcture (6) indicate electron... 

Metal-centered emission is found in several rare-earth complexes, for example europium diketone chelates [29]. These compounds emit relatively narrow spectra associated with the d-f transitions of the metal ion. Relatively few comprehensive studies of this class have been carried out to date, but the available evidence [30] seems to indicate that the photoluminescent efficiencies are somewhat lower than the ligand-centered emitters. 

P-diketone chelates, 25 89-91 Beta distribution, 26 1020 P-eleostearic acid, physical properties,... 

Sato, S. Wada, M. Relations between intramolecular energy transfer efliciences and triplet energies in rare earth beta-diketone chelates. Bull. Chem. Soc. Japan 1970, 43,1955. 

The (3-diketonate chelate complexes are very stable and exhibit properties which are rather typical of aromatic systems. Many of their reactions such as halogenation, alkylation and acylation can be compared with those of the P-diketonate anions associated with alkali metal cations. However, complexes of transition and other metals add to the stability of the system, so that quite vigorous reaction conditions can be employed. In most of the work carried out on P-diketonate chelates, the modified ligand has not been removed from the metal ion, but this can usually be effected if desired. 

Mishin, V. I., Dobychin, S. L. Porous PTFE as adsorbent in gas chromatography of metal- -diketone chelates. Zh. Prikl. Khim, Leningr. 43, 1584 (1970). — Anal. Abstr. 

Sager, W.F., Filipescu, N., and Serafin, F.A. (1964) Substituent effects on intramolecular energy transfer. I. Absorption and phosphorescence spectra of rare earfli -diketone chelates. The Journal of Physical Chemistry, 69, 1092. 

Seradyn Inc., Indianapolis, IN) contain several thousands of different Eu -/ -diketone chelates inside a single polystyrene shelP. Also, particles dyed with Tb +, and... 

Separation of six -diketonate-metal chelates by HPLC was first carried out by liquid-liquid partition chromatography involving water-ethanol-2,2,4-trimethylpentane. Of the examined acetylacetonates of Be(II), Al(III), Cr(III), Fe(III), Co(III), Ni(II), Cu(II), Zn(II), Zr(IV) and Ru(III), they separated four-component mixmres within 25 minutes. Because of dissociation of the chelates on the column, acacH had to be included in the eluent Successful separation of S-diketonate chelates by normal phase chromatography was demonstrated also by other investigators ... 

Freeman, Crosby, Lawson (13), Kropp, and Windsor 17, 18) had reported that hydrated europium chloride crystals and aqueous solutions of europium salts, respectively, showed considerable enhancement of ion fluorescence and lifetimes upon substitution of H2O by D2O, the latter workers have reported (37) that wet hydrocarbon solutions of the thenoyltrifluoroacetone chelate of europium showed no enhancement of quantum yield and lifetime upon replacing the H2O present by D2O. They suggested that whereas deuteration enhanced the fluorescent properties of the free ions by inhibiting nonradiative deactivation of the Do level, the quantum efficiency of Do luminescence obtained upon direct excitation of this level (JO, 11) is already so high in the fluorinated diketone chelates e.g. thenoyltrifluoroacetone) that deuteration of the environment should have little further enhancing effect. 

Fontaine, R., SantonL B., Pommier, C., Guichon, G. Utilisation of U-diketone chelates for determination of uranium and thorium. Anal. Chim. Acta 62, 337 (1972)... 

P-Diketonates. /3-Diketones chelate with metal ions, including actinides, to form neutral species via the deprotonated enolate anions as illustrated in Figure 24. " A very wide array of homoleptic complexes of the general formula Au(R COCR COR )4 have been reported for... 

N Filipescu, WF Sager, FA Serafin. Substituent effects on intramolecular energy transfer, n. Fluorescence spectra of europium and terbium beta-diketone chelates. J Phys Chem 68 3324, 1964. 

Zinc.—Changes in the fluorescence and phosphorescence yields of / -diketone chelates of Zna+, Be2+, and Al3+ have been attributed to interligand interactions.137 Other authors have studied the luminescence properties of salicylalaniline chelates of Zn2+, Hg2+, Cd2+, and Be2+,138 and of a dinuclear complex of ZnCl2 with zinc salicylidene-toluidinate.139 The photolysis of Zn(N3)2 in the solid state has been reported.140... 

The lanthanide is dissociated from the labelling chelate into a highly fluorescent beta-diketone chelate micelle. The principle of dissociation-enhancement, the basis for assays with both reagent stability and intensive, stable fluorescence. 

Most of the work with these metals has involved j8-diketonate chelate complexes, particular interest being shown in the use of new jS-diketonate complexes of europium(iii) and praeseodymium(iii) [e.g. tris-(l,l,l,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionato)europium(iii) and the chiral tris(perfluoroacylcamphorato) complexes (O ] as n.m.r. shift reagents (sec Chapter 3, pp. 162 and 176). 

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