From zinc carboxylates

Figure 4.1 Representation of the structure of MOF-5 (a) six carboxylic acid groups from terephthalic acid are connected to four Zn" cations to form a metal-organic elementary zinc carboxylate cluster (only...

Zinc carboxylate interactions have been exploited as part of a fluorescent molecular sensor for uronic acids. The sensors feature two interactions coordination of the carboxylate to the zinc and a boronic acid diol interaction.389 Photoluminescent coordination polymers from hydrothermal syntheses containing Zn40 or Zn4(OH)2 cores with isophthalate or fumarate and 4,4 -bipyridine form two- and three-dimensional structures. Single X-ray diffraction of both dicarboxylates identified the network structure.373... 

As mentioned earlier, by far the largest number of zinc enzymes are involved in hydrolytic reactions, frequently associated with peptide bond cleavage. Carboxypeptidases and ther-molysins are, respectively, exopeptidases, which remove amino acids from the carboxyl terminus of proteins, and endopeptidases, which cleave peptide bonds in the interior of a polypeptide chain. However, they both have almost identical active sites (Figure 12.4) with two His and one Glu ligands to the Zn2+. It appears that the Glu residue can be bound in a mono- or bi-dentate manner. The two classes of enzymes are expected to follow similar reaction mechanisms. 

Maass and Eigen have shown for the zinc acetate system fos " 32 — 3.2 X 107 sec."1 The rate of loss of water from zinc equals the rate of loss of a carboxylate group from zinc. This means that the ion pair and inner sphere species of zinc acetate are present in solution in equal amounts. If we now examine the zinc oxalate system we see that we have similar rate steps. 

Electrical conductivity studies on molten zinc carboxylates of even-numbered chain length from C6 to C18 are consistent with a small concentration of relatively mobile Zn2+ ions.779... 

Most thermal stabilizers for poly (vinyl chloride) are metal salts of carboxylic acids or mercaptans. The commonly used metals are cadmium, barium, zinc, lead, calcium, and dibutyltin. Originally it was assumed the metal salts act as scavengers for hydrogen chloride. However, Frye and Horst (7, 8) found evidence for the introduction of ester groups in the polymer from metal carboxylate stabilizers, which led them to postulate that thermal stabilizers function by substituting the unstable chlorine atoms with the ligands of the stabilizer to yield derivatives which are more thermally stable than the original chloride. 

Double acetates of the composition M [M(OAc)4],xAc20 (M = Li, Na, K, NH4, or T1 M = Zn, Cd, or Hg x = 4,6) have been prepared, and possible structures are proposed. Electrical conductivity studies on molten zinc carboxylates of even-numbered chain length from to are consistent with a small concentration of relatively mobile Zn ions. ... 

Similar to the concept described for the Oj-Hj cell system, the reductive activation of oxygen can be expected at the cathode in the presence of a suitable catalyst. On the basis of this zinc-air battery model, we have designed a number of catalytic systems from mixtures of zinc powder, carboxylic acid and various metal chlorides for oxygenations of alkanes and alkenes. In these catalytic systems, zinc powder works as the reductant as well as the electron conducting medium. The carboxylic acid works as a proton-conducting medium. Oxygen is reductively activated on the metal cations by protons from the carboxylic acid and electrons from zinc powder. 

Fig. 4 The catalytic mechanism of CPA in the hydrolysis of peptides, taken from Ref [3]. (a) Upon anchorage of a substrate to the active site, the carboxylate of Glu-270 triggers the reaction by abstracting a proton from zinc-bound water, which in turn, undergoes nucleophilic attack on the scissile carbonyl, (b) A tetrahedral intermediate is generated its formation and collapse may be assisted by proton donation from Arg 127 or other residues.

To improve the efficiency of the vulcanization reaction, various accelerators were developed. Among them are zinc oxide combined with fatty acids, and/or amines. Zinc oxide forms zinc mercaptides like (XS)2ZnL2, where X is an electron-withdrawing substituent and L is a ligand from a carboxyl or an amine group. The function of the ligand is to render the complex soluble. The mercaptide complexes are believed to react with additional sulfur to form zinc perthiomeraptides. 

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