Structure polycarboxylates

Crisp, S., Lewis, B. G. Wilson, A. D. (1976a). Zinc polycarboxylate cements. A chemical study of erosion and its relationship to molecular structure. Journal of Dental Research, 55, 299-308. 

Some dyes contain a coordinated transition metal as an essential part of their chromogenic structure and this must be left undisturbed by any sequestrant used to complex extraneous metal ions in the system. Hence a balance of properties is needed, phosphates and hydroxycarboxylates being useful. It is claimed that polycarboxylates can be molecularly engineered to give the required balance of properties. 

There is an interesting technique which makes it possible to introduce carboxylic acid groups into a copper phthalocyanine structure by an economical route. Carrying out the phthalic anhydride/urea process in the presence of a small amount of trimellitic acid or another benzene polycarboxylic acid will afford a car-boxylated pigment. 

Table 2 Comparison of average C-0 structural parameters (A) for neutral and partially deprotonated polycarboxylic acids as extracted from the Cambridge Structural Database (CSD) ...

Structure-Property Relation of Polyhydroxyl and Polycarboxylic Xanthate... 

The influence of three kinds of polyhydroxyl xanthate and four kinds of polycarboxylic xanthate on arsenopyrite and pyrrhotite flotation are further examined in order to compare the effect of the depressant structure on their depressing action. The formulae of three polyhydroxyl xanthates are shown in Table 5.3 and their depression on arsenopyrite flotation is given in Fig. 5.34. It is obvious that the depressing ability of polyhydroxyl xanthates is in the order of GX3 > GX2 > GXl. The more the hydroxyl groups in the depressant polyhydroxyl... 

Fig. 3. Structure of an MIM with a tetracarboxylic core. C polycarboxylic core of MIM GI first layer of triiodinated rings. I3 triiodinated aromatic ring G2 second layer of triiodinated rings. L amido-acetyl bond G3 third layer of triiodinated rings. AA amino alcohol...

The unique seven-coordinate complex [TcO(EDTA)] is obtained by reaction of [TcOCy with H4EDTA in anhydrous dmso. The X-ray crystal structure confirmed pentagonal-bipyrami-dal geometry, with the 0x0 group and the two nitrogen donors bound in the equatorial plane. " All other structurally characterized technetium complexes with polyamino-polycarboxylates are in oxidation state IV. 

Poly[(a-carboxymethyl)ethyl isocyanide] may be saponified with sodium hydroxide in methanol at room temperature in 5 days or at reflux in 20hrs, attended by discoloration. Aqueous solutions of the isolated salt do not show viscosities expected of polyanions. Attempt to isolate the free polycarboxylic acid by acidification is accompanied by decarboxylation, which is to be expected on the basis of its chemical structure (55). 

Bouquet -shaped molecules based on either a polyether macrocycle [8.205] or a /3-cyclodextrin (/3-CD) [8.206] core, such as 114 and 115 respectively, have been synthesized and their polycarboxylate forms have been incorporated into vesicle bilayer membranes [8.207]. They present structural features suitable for studies of chundle-type molecular channels (1) the functionalized cyclic annulus possesses substrate selection properties (2) it bears axially oriented bundles of oxygen-containing chains, which provide binding sites for metal cations and are long enough for the molecule to span a typical lipid membrane (the overall length with the chains... 

The occurrence of polycarboxybenzenes in all oxidation reactions is of interest in studying lignin structure. These results do not indicate whether the basic structures were originally present in lignin or result from condensation. However, further improvement of the GLC technique to resolve all 11 polycarboxylic acids is desirable to determine which of the various isomers normally appear in the oxidations. 

Also, when benzene polycarboxylic acid compounds (31-35) were used, a 3 1 complex (39) of trimellitic acid (34) with 1, and a 2 1 complex (40) of pyromel-litic acid (35) with 1 were obtained (Table 4). Although the inclusion complexes were not obtained with the other similarly structured compounds (31-33), it was shown that as the number of carboxyl groups of the host increases, the inclusion complexation becomes easier. 

Aromatic polycarboxylates easily form 2D or 3D networks, for instance [Nd2(122)3(dmf)4]-H2O which present a 2D structure in which the 1,4-naphthalenedicarboxylate anions link Ndm ions of two adjacent double chains keeping them at a short distance of about 4.1 A (J. Yang et al., 2006). This allows up-conversion to take place, albeit with very low efficiency a blue emission is seen at 449.5 nm upon excitation at 580 nm (corresponding to the 4Gs/2 magnetic properties an energy-transfer up-conversion mechanism involving no excited state absorption is more likely. 

---