Visible absorption spectra of metal–catecholate and metal–tironate complexes

Abstract

Interactions between metals and catechol (1,2-dihydroxybenzene) or other ortho-dihydroxy moieties are being found in an increasing number of biological systems with functions ranging from metal ion internalization to biomaterial synthesis. Although metal-catecholate interactions have been studied in the past, we present the first systematic study of an array of these compounds, all prepared under identical conditions. We report the ultraviolet-visible absorption (UV-vis) spectra for catecholate and tironate complexes of the first row transition elements. Generation and identification of these species were accomplished by preparing aqueous solutions with varied ligand:metal ratios and subsequently titrating with base (NaOH). Controlled ligand deprotonation and metal binding resulted in sequential formation of complexes with one, two, and sometimes three catecholate or tironate ligands bound to a metal ion. We prepared the mono-, bis- and tris-catecholates and -tironates of Fe(3+), V(3+), V(4+)and Mn(3+), the mono- and bis-catecholates and -tironates of Cu(2+), Co(2+), Ni(2+), Zn(2+), Cr(2+) and Mn(2+), and several Ti(4+) and Cr(3+) species. The UV-vis spectra of each complex are described, some of which have not been reported previously. These data can now be applied to characterization of biological metal-catecholate systems.

Silicate Covering Layer on Pyrite Surface in the Presence of Silicon–Catechol Complex for Acid Mine Drainage Prevention

“…23,24) Based on those reports, silicate covering layer was not created completely and the suppression effect was lower than that of Si-Cat treated pyrite initially pH 9.5. These data also supported by Ultraviolet-visible (UV) absorption spectra studies conducted by Sever and Wilker 25) that showed that at low pH (<7), catechol is reduced and coordination complexes are dissolved instead of cross linked. Figure 5 show SEM-EDX images of 6 h Si-Cat treated pyrite samples initially pH 3, 7, and 9.5 compared with untreated pyrite.…”

Mechanical homeostasis of a DOPA-enriched biological coating from mussels in response to metal variation

“…Thus, a key determinant of the 'mechanical homeostasis' exhibited by the cuticle may be the ability to fix the number of DOPA binding sites because it limits the number of cross-links to an acceptable range and prevents over-stiffening under high metal concentration conditions. At the same time, employing DOPA as a ligand likely facilitates the formation of very stable complexes with a broad range of metal ions [38], increasing the likelihood of filling all cross-linking sites under low metal concentration conditions. Variations in hardness, as exhibited in Al-recovery threads, are more difficult to interpret-especially because this is a viscoelastic material.…”

Adhesive strength and curing rate of marine mussel protein extracts on porcine small intestinal submucosa

“…Based on prior research [49][50][51], the authors of this paper hypothesized that transition metal ions that are also strongly oxidative may cause the MAP protein chains to cross-link among themselves. Those investigations demonstrated that metal-induced cross-linking is a combination of both chelation of the metal ions by the protein and oxidation of the protein by the metal [50], and that increasing concentration of oxidative transition metals increased cross-linking of MAP protein chains [51,52].…”

“…Although several recent studies have increased the scientific community's understanding of how blue mussels cure their adhesive precursors [26][27][28][29][30][42][43][44][45][46][47][48][49][50][51], the mechanism is not yet completely understood. It appears that the precursor proteins are cross-linked by a complex interaction of dihydroxyphenylalanine (DOPA) motifs in the protein, facilitated by enzymes and oxidative reagents such as metal ions.…”