Oxine derivatives

TABLE 2. Metal selectivity series for some basis polymers. PEI, poly(ethylenimine) (PEI) PTU, thiourea derivative of PEI PDA, diamino acetic acid derivative of PEI POX, oxine derivative of PEI. 

Data for several 8-hydroxyquinoline (oxin) derivatives were given in Table 14.11 for convenient comparison with other octahedral compounds. MejSn.oxinj is known from X-ray measurements to have a highly distorted... 

Complexes prepared from [Rh(CO)2Cl]2 include (a) five-coordinate [Rh(CO)2L2CI] (L = many imidazoles), (b) [Rh(CO)2(bid)), [Rh(CO) P(OPh)(bid)] and [Rh(CO)(PPh )(bid)] (bid = the anionic chelate ligands, 2-carboxyquinolinato, 1,1,1-trifluoro - 5,5,5-tri-methylpentanedionato, N-hydroxy-N-nitrosobenzenaminato, oxinate derivatives, and the Schiff bases derived from condensations of 3-diketones with N-methyl-S-methyldithiocarbazates),(c) [ Rh(CO)2)2 -L4] (L4 = tetradentate azine dianions e.g. 0CgH4CH=NN=CHCgH40 ),... 

S-hydroxyquinoline, oxine, C9H7ON. Light brown needles, m.p. 15-16 C. Forms insoluble complexes with metals. The solubilities of the derivatives vary with pH, etc. and hence oxine is widely used in analysis. Used for estimating Mg, Al, Zn and many other metals. Many oxinates are extracted and the metal is estimated spectrophotometrically. Derivatives, e.g. 2-meIhyl tend to be specific, for, e.g.. Copper derivatives are used as fungicides. 

Hence 1 mole of the oxinate of a double-charged metal corresponds to 4 moles of bromine, whilst that of a triple-charged metal corresponds to 6 moles. The bromine is derived by the addition of standard 0.02Af potassium bromate and excess of potassium bromide to the acid solution. 

There are many interesting derivatives of quinoline and acridine obtained by substitution. In particular, 8-hydroxyquinoline (oxine) is the second complexing agent in importance after EDTA. Sulfonation in position 5 leads to a compound which is soluble in water and that exhibits outstanding fluorogenic properties (i.e. fluorescence enhancement) on complexation with metal ions (e.g. aluminum). 

Such a fluorescence enhancement in these compounds 32-34 is similar to that observed in metal chelates with 8-hydroxyquinoline (oxine) and its derivatives but is not fully understood yet. 

The formation of complexes of various metal ions with oxine (5) and some of its derivatives, their extraction into CHCI3 and their Xmax and e values have been reviewed. Purpurin (LH3, 17) forms with Mg(II) colored complexes of varied composition. However, at pH 9.5 the complex MgLH is formed and can be measured at 540 nm (e =... 

The unavailability of suitable starting materials has hindered work in this area, but the reaction of cyclopentadienylindium(I) in Et20/benzene mixtures with 4,4,4-trifiuoro-l-(thien-2 -yl)butane-l,3-dionate (ttaH) gave the extremely hygroscopic In(tta), and similar derivatives of other bidentate ligands were obtained by this same process.14 The reactions of the analogous In(oxine) (oxine = 8-hydroxyquinoline anion) show that such InL species are easily oxidized to indium(III) complexes (see Section 25.2.4.8). The insolubility of the product in the reaction mixture is presumably an important factor in this method. 

The stereochemistry of molecular six-coordinated dimethyltin derivatives can vary substantially from the cis [SnQQj geometry (71), adopted by dimethyltin bis(oxinate)441 and... 

Early solid complexes include [VO(oxine)2], [VO(oxine)2py] and [VO(5,7-X2oxine)2] (X = Br, I).357 [VOX(oxine)] (X = Cl, Br, OH) were also prepared with magnetic moments dependent on temperature.823 On the contrary, for brown [VO(oxine)2], prepared from V0S04 in aqueous solution,387 /4fr is near the spin-only value and v(V=0) = 979 cm-1.595 These values indicate a monomeric structure and this was confirmed for its 2-methyl derivative by X-ray diffraction (Figure 36).824... 

Figure 4 Plots of log (fraction ionized) versus pH for oxine and two of its derivatives showing the need for a higher pH in the case of 2-methyloxine to attain the same fractional amount of coordinating ligand...

Virtually all chelate complexes of the type M(Ox)m derived from the cation Mm+ are extractable into chloroform and, being coloured, form the basis of spectrophotometric determinations. The extractions can be made more selective by controlling the pH (cf. Section 10.2.2.1) and/or by using suitable masking agents. Thus extraction of the yellow aluminum trisoxinate can be made almost specific at pH 8.5—9.0 if EDTA, cyanide ions and sulfite ions (to reduce FeI I to Fe11) are present. Since the range for extraction of individual metal oxinates extends from pH 1.6 to 14, separation of individual species is facilitated.52 59... 

R. Berg, Die analytische Verwendung von o-Oxychinolin (Oxin) und seiner Derivate , 2nd edn., Enke, Stuttgart, 1938. 

Complexes of pyridine-2-carboxylic acid (picolinic acid, picH) and its substituted derivatives commonly exhibit the N—O bidentate nature of this aromatic amino acid. From aqueous solutions chelates are obtained with the coordinated carboxylic group deprotonated, or neutral ligand forms may be isolated from non-aqueous media.26 Bis chelates are common in either case with bivalent metal ions. The tris chelates of trivalent cobalt27 and manganese28 have been structurally characterized recently. The latter is tetragonally distorted in a structure similar to Mnin(oxine)3. 

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