Dipicolinate complexes structures

The structure of the deep red diaquoperoxotitanium(IV) dipicolinate complex, [Ti02(C7H304N)(H20)2].2H20 was reported. The complex (see... 

We pass next to the Ln(III) bis-dipicolinate complexes, shown in Fig. 6. There is no crystal structure for the complexes. Flowever detailed examination of the proton NMR spectra at room temperature shows that the shift ratios are again constant throughout the series and that absolute shifts follow Bleaney s predicted values, Table 3. The complexes must be isostructural and must have axial symmetry. Again the use of relaxation data gives an independent assessment of the relative distances of meta and para protons. We can put all the data together and give a structure for the complex ion as in Fig. 6 leaving three water molecules in the inner sphere. To prove that this is so we must analyse the proportions of the water, both bound and outer sphere. 

We can turn finally to the mono dipicolinate complexes. The same analysis as above shows that in solution the M(dipic) complexes are isostructural. The exact structure has been determined using shift and relaxation data as above, see Refs. 34—36. Knowledge of the relaxation data for both ligand and water protons and the known relaxation of the contribution to water relaxation from the outer sphere then permits calculation of the number of water molecules in M(dipic)(H20)n. We have shown that n = 6 for all the lanthanides. 

Lanthanide coordination chemistry is still not completely understood, and many attempts are usually required to design specific Inminescent lanthanide complexes. As an alternative to rational design, a combinatorial approach shows promise for the development of specific luminescent lanthanide materials. Shinoda et al. built a combinatorial library to optimize luminescent lanthanide complexes structurally for the selective detection of amino acids. The lanthanide complex library included 196 combinations of 4 lanthanide centers, 7 pyridine ligands, and 7 amino acid substrates (Figure 16.16). The luminescence responses for amino acids depended on the nature of the ligand used. A series of Tb + complexes typically exhibited interesting luminescence responses. The TV+-picolinic acid complex and Tb -pyrazinecar-boxylic acid complex preferred zwitterionic Ala, Val, Phe, and Gin, whereas the Tb complex with dipicolinic acid favored anionic Gin and Asp. 

Inner-sphere 1 1 and 2 1 picolinate-bridged complexes have been detected " in the reduction of [Co(III)2], structure 2, R = dipicolinate, and structure 3 by... 

Figure 5.9 From left to right structure of water soluble tris-dipicolinate complexes (Ln = Tb or Eu), three photon excited (lex = S00nm) luminescence, variation of the luminescence intensity with the incident laser power for a two (right, top) or three (right, bottom) photon excitation (Zex = 532 or 800 nm respectively) In linear or log scale, respectively (between parenthesis is indicated the experimental determination of the multi-photon absorption)...

This chapter discusses the coordination chemistry of selected main group and transition metal complexes with dipicolinic acid, its analogues, and derivatives as ligands. Selected elements will be presented in terms of increasing atomic number. Out of all of the alkali metals, there has been a report of the crystal structure of sodium coordinated to dipicolinic acid. Calcium, magnesium, and strontium, three alkaline earth metals, are popular metal centers, which have been reported in the literature to be coordinated to dipicolinic acid or its analogues. ... 

Reaction of (C5H5)2Ti(CH3)2 or (CH3)4C2(C5H4)2Ti(CH3)2 with dipicolinic acid produced several titanoeene dipieolinate derivatives. Figure 5 shows the structure of one of those derivatives. As expected from structural studies on other transition metal dipieolinate complexes, the dipieolinate ligand is... 

Chemical crystallography is the study of the principles of chemistry behind crystals and their use in deseribing strueture-property relations in solids. The prineiples that govern the assembly of crystal and glass structures are deseribed, models of many of the teehnologically important erystal struetures are studied, and the effect of crystal structure on the various fundamental meehanisms responsible for many physical properties are discussed. This new book presents and reviews data on the coordination chemistry of several metal complexes with dipicolinic acid and the erystal structure of some antimalarial metal complexes. 

Analogous to the work on dipicolinic acid reported in Section 31.5.2, a range of titanium(IV) peroxo complexes (35) have been prepared which encompass an oxygen-nitrogen anionic chelating ligand and hexamethylphosphortriamide.171 The crystal structure of... 

A number of x-ray structures of monoperoxoheteroligand complexes of vanadate have been reported. The heteroligands have included picolinate, dipicolinate, dipeptides, and a number of a-hydroxycarboxylate. Solution NMR studies have been carried out for several of these systems, and various solution products described. Table 6.4 gives the 51V NMR chemical shifts for a number of products that have been studied. This table covers a variety of types of complexes, and the chemical shifts range over about 100 ppm, from about -580 to -680 ppm. 

Taking all the evidence together it is clear that we need a deeper insight into the structures of the complexes Ln(H20) (ligand). So far we have used the paramagnetic properties of Ln(III) to look at Ln(ligand). We can of course examine the water bound in the complexes by similar methods. We shall take the series of complexes Ln(dipicolinate)n(H20)m as examples below. Our results then throw light on the many problems of the nature of Ln(III) complexes in solution. 

It might be considered that the way in which to understand the water complex ion chemistry of the lanthanide ions in aqueous solution would be to start from their hydrates. In fact the hydrates prove to be most intransigent complexes. Their structures are still somewhat uncertain. I shall therefore start from a study of the tris-dipicolinates, i.e. tris 2,2 -carboxy-pyridine complexes, Ln(dipic)3, about which a great deal is known. 

Dipicolinates (pyridine-2,6-dicarboxylates) have been investigated in some detail with structures determined for several tris complexes such as Na3[Nd(dipic)3]-15H20 and Na3[Yb(dipic)3]13H20, typical of the early and later lanthanides, respectively. The lanthanides have essentially tricapped trigonal prismatic coordination geometries, isostruc-tural along the lanthanide series they have been the subject of important solution NMR studies. Mono and bis complexes can also be synthesized the mono complex [Nd(dipic)(H20)4] CIO4 has a polymeric structure in which each picolinate is bound to three different (nine-coordinate) neodymium ions. 

Interaction of Np(IV) with dipicolinic acid in solution was not investigated. On the other hand, the formation of solid compound with ratio Np to DPA equal to 1 3 is observed [117]. Crystal structure of the complex... 

FIGURE 17 Schematic formation of D3-symmetrical lanthanide triple-helical building blocks with (A) 2,6-dipicolinic acid and (B) 2,2 6, 2" terpyridine. Structures of the complexes [ 17(115 )3] and [Eu(L16%] + are redrawn from Harrowfield et al. (1995) and Semenova et al. (1999), respectively. 

Bacterial spores are the most resistant microbial structures toward extreme conditions. As a consequence, they find applications in the evaluation of the efficiency of sterilization processes. They are also present in the ominous Bacillus anthracis spores which have been the biological vectors in anthrax attacks. Dipicolinic acid is a remarkable constituent of these spores so that they may be detected through complexation with Tb ". In the proposed procedure. Cable et al. (2007) start from a macrocyclic complex, [Tb(D02A)]+ where D02A is 1,4,7,10-tetraazacyclododecane-... 

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