Zinc(II) and cadmium(II) complexes of a tridentate oximate ligand cleave 4-nitrophenyl acetate with rate constants surpassing by two orders of magnitude those reported as the maximum possible level for highly basic free oximate anions as a result of removal of the "solvational imbalance" of the nucleophile by metal coordination.
Interactions of anthracene appended ortho-aminomethylphenylboronic acid 1 with 20 organic and inorganic anions have been studied by fluorescence, 1H and 11B NMR titrations in DMSO. Carboxylate, phosphate and sulphate anions...
The application of polymers as medical devices has steadily increased in almost all medical fields because of the versatility of these materials. Thus, research has focused both on the development of more appropriate materials for specific situations and on the modification of already useful materials for the improvement of their intrinsic properties. Modifications on this kind of materials have increased their potential uses by adapting their mechanical properties to specific needs. Moreover, biocompatibility of the polymeric materials has been improved by the inclusion of certain functional groups, providing responses to physical and chemical stimuli present in physiological conditions.Until recently, one of the most worrying problems in hospitals has been infections derived from medical devices usage. Typically, this kind of infections was handled with the use of prophylactic and therapeutic treatments with 'classic' (low-molecular weight) antimicrobial agents. This strategy has been effective in most patients suffering from nosocomial infections. However, it has the disadvantage of substantially increasing the probability of antimicrobial-resistant pathogens appearance, which continue to be especially dangerous in hospital environments (Cohen et al., 2017; World Health Organization, n.d.;Zegers et al., 2017). Additionally, due to
Deprotonated zinc(II) and cadmium(II) complexes of a tridentate oxime nucleophile (1, OxH) show a very high reactivity, breaking by 2-3 orders of magnitude the previously established limiting reactivity of oximate nucleophiles in the cleavage of substituted phenyl acetates and phosphate triesters, but are unreactive with p-nitrophenyl phosphate di- and monoesters. With reactive substrates, these complexes operate as true catalysts through an acylation-deacylation mechanism. Detailed speciation and kinetic studies in a wide pH interval allowed us to establish as catalytically active forms [Cd(Ox)], [Zn(Ox)(OH)], and [Zn(Ox)(OH)] complexes. The formation of an unusual and most reactive zinc(II) oximatodihydroxo complex was confirmed by electrospray ionization mass spectrometry data and supported by density functional theory calculations, which also supported the previously noticed fact that the coordinated water in [Zn(OxH)(HO)] deprotonates before the oxime. Analysis of the leaving group effect on the cleavage of phenyl acetates shows that the rate-determining step in the reaction with the free oximate anion is the nucleophilic attack, while with both zinc(II) and cadmium(II) oximate complexes, it changes to the expulsion of the leaving phenolate anion. The major new features of these complexes are (1) a very high esterolytic activity surpassing that of enzyme hydrolysis of aryl acetate esters and (2) an increased reactivity of coordinated oxime compared to free oxime in phosphate triester cleavage, contrary to the previously observed inhibitory effect of oxime coordination with these substrates.
A family of oximate complexes of Zn(ii) and Cd(ii) with esterolytic reactivity surpassing the limiting reactivity of highly basic free oximates has been developed and mechanistically characterized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.