No abstract

An iron(III)-catecholate complex [L(1)Fe(III)(DBC)] (2) and an iron(II)-o-aminophenolate complex [L(1)Fe(II)(HAP)] (3; where L(1) = tris(2-pyridylthio)methanido anion, DBC = dianionic 3,5-di-tert-butylcatecholate, and HAP = monoanionic 4,6-di-tert-butyl-2-aminophenolate) have been synthesised from an iron(II)-acetonitrile complex [L(1)Fe(II)(CH(3)CN)(2)](ClO(4)) (1). Complex 2 reacts with dioxygen to oxidatively cleave the aromatic C-C bond of DBC giving rise to selective extradiol cleavage products. Controlled chemical or electrochemical oxidation of 2, on the other hand, forms an iron(III)-semiquinone radical complex [L(1)Fe(III)(SQ)](PF(6)) (2(ox)-PF(6); SQ = 3,5-di-tert-butylsemiquinonate). The iron(II)-o-aminophenolate complex (3) reacts with dioxygen to afford an iron(III)-o-iminosemiquinonato radical complex [L(1)Fe(III)(ISQ)](ClO(4))(3(ox)-ClO(4); ISQ = 4,6-di-tert-butyl-o-iminobenzosemiquinonato radical) via an iron(III)-o-amidophenolate intermediate species. Structural characterisations of 1, 2, 2(ox) and 3(ox) reveal the presence of a strong iron-carbon bonding interaction in all the complexes. The bond parameters of 2(ox) and 3(ox) clearly establish the radical nature of catecholate- and o-aminophenolate-derived ligand, respectively. The effect of iron-carbon bonding interaction on the dioxygen reactivity of biomimetic iron-catecholate and iron-o-aminophenolate complexes is discussed.

Immobilization of transition-metal complexes by surface functionalization of gold nanoparticles (AuNPs) has recently attracted the attention for several applications.[1] Thiolprotected AuNPs [2] are stable and soluble in organic solvents. Therefore, immobilization of metal complexes on AuNPs permits reactions in common organic solvents and also induces properties of the metal complex to the NP.[3] AuNPs functionalized by thiol-appended transition metal complexes are expected to find applications as immobilized catalysts to bridge between homogeneous and heterogeneous catalysis. The high surface area of a nanocatalyst increases the contact between the reactant and catalyst dramatically. These catalysts are easy to synthesize through desired surface modification and can be characterized by different analytical and spectroscopic techniques. Moreover, the catalyst can easily be separated from the reaction mixture. Several reports are now available where immobilization of metal catalysts on AuNPs has been shown to increase the catalytic reactivity.

Biofouling, the unwanted growth of sessile microorganisms on submerged surfaces, presents a serious problem for underwater structures. While biofouling can be controlled to various degrees with different microstructure-based patterned surfaces, understanding of the underlying mechanism is still imprecise. Researchers have long speculated that microtopographies might influence near-surface microfluidic conditions, thus microhydrodynamically preventing the settlement of microorganisms. It is therefore very important to identify the microfluidic environment developed on patterned surfaces and its relation with the antifouling behaviour of those surfaces. This study considered the wall shear stress distribution pattern as a significant aspect of this microfluidic environment. In this study, patterned surfaces with microwell arrays were assessed experimentally with a real-time biofilm development monitoring system using a novel microchannel-based flow cell reactor. Finally, computational fluid dynamics simulations were carried out to show how the microfluidic conditions were affecting the initial settlement of microorganisms.

The synthesis and characterization of an iron-catecholate model complex of a tridentate 2-N-1-carboxylate ligand derived from L-proline are reported. The X-ray crystal structure of the complex [(L)(3)Fe(3)(DBC)(3)] (1) (where L is 1-(2-pyridylmethyl)pyrrolidine-2-carboxylate and DBC is the dianion of 3,5-di-tert-butyl catechol) reveals that the tridentate ligand binds to the iron center in a facial manner and mimics the 2-his-1-carboxylate facial triad motif observed in extradiol-cleaving catechol dioxygenases. The iron(III)-catecholate complex (1) reacts with dioxygen in acetonitrile in ambient conditions to cleave the C-C bond of catecholate. In the reaction, an equal amount of extra- and intradiol cleavage products are formed without any auto-oxidation product. The iron-catecholate complex is a potential functional model of extradiol-cleaving catechol dioxygenases.