Electrochemical synthesis, structural, spectral studies and DFT calculations of heteroleptic metal-chelates bearing N, N, S tridentate tosylamino functionalized pyrazole containing Schiff base and 1,10-phenathroline

The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review

Tridentate ligands are simple low-cost pincers, easy to synthetize, and able to guarantee stability to the derived complexes. On the other hand, due to its unique mix of structural and optical properties, zinc(II) ion is an excellent candidate to modulate the emission pattern as desired. The present work is an overview of selected articles about zinc(II) complexes showing a tuned fluorescence response with respect to their tridentate ligands. A classification of the tridentate pincers was carried out according to the binding donor atom groups, specifically nitrogen, oxygen, and sulfur donor atoms, and depending on the structure obtained upon coordination. Fluorescence properties of the ligands and the related complexes were compared and discussed both in solution and in the solid state, keeping an eye on possible applications.

A facile biomimetic catalytic activity through hydrogen atom abstraction by the secondary coordination sphere in manganese(III) complexes

This paper describes the synthesis and structural characterization of four new manganese(iii) complexes (1-4) derived from N3O donor Schiff base ligands and their biomimetic catalytic activities related to catechol oxidase and phenoxazinone synthase. X-ray crystallography reveals that the Schiff bases coordinate the metal centre in a tridentate fashion, leaving the pendant tertiary amine nitrogen atom either protonated or free to balance the charge of the system, and these pendant triamines participate in strong hydrogen bonding interactions in the solid state. The hydrogen bonding ability of the pendant triamines at the second coordination sphere plays a crucial role in the substrate recognition and the stability of the complex-substrate intermediates. The effect of substitution at the phenolate ring towards the redox potential of the metal centre and the catalytic activity of these complexes has been observed. Detailed kinetic studies further disclose the deuterium kinetic isotope effect in which the transfer of the proton along the hydrogen bond from the substrates to the pendant triamine group at the secondary coordination sphere occurs at the key step in the catalytic reaction. The present reactivity nicely resembles the biochemical reactivities in the natural system in which a concerted electron and proton transfer to different species is usually observed. Remarkably, although some sort of influence of the secondary coordination sphere on catalytic activity has been reported mimicking the function of these metalloenzymes, such a direct participation of the secondary coordination sphere, particularly in modelling phenoxazinone synthase, has not been observed to date.

New cobalt(ii) coordination designs and the influence of varying chelate characters, ligand charges and incorporated group I metal ions on enzyme-like oxidative coupling activity

In transition-metal-mediated catalysis, design of new, well defined coordination architectures and subjecting them to catalysis testing under the same reaction conditions is a necessity tool for improved understanding of desirable active site geometries and characteristics.

The first report of a tetra-azide bound mononuclear cobalt(iii) complex and its comparative biomimetic catalytic activity with tri-azide bound cobalt(iii) compounds

Three new azide-bound cobalt(iii) complexes derived from three different triamines with extensive hydrogen bonded supramolecular chain structures and the role of their structural factors in oxidative coupling of o-aminophenols have been reported.

Green electrochemical synthesis of silver sulfadiazine microcrystals

Electrochemical synthesis of silver sulfadiazine (AgSD) microcrystals was carried out galvanostatically in a special two-electrode cell equipped with a sacrificial silver rod anode and a stainless steel plate cathode. The cell used in this work consists of a small cylindrical chamber containing aqueous sulfadiazine/sodium nitrate as the anode compartment inside a larger cylindrical chamber containing nitric acid solution as the cathode compartment. The ionic connection of two chambers is carried out through a solvent surface layer. In this study, the effect of the experimental parameters such as applied current density and sodium nitrate concentration as well as nitric acid concentration on the yield and energy consumption of AgSD is discussed. The proposed method is fast and green and has unique features including synthesis in a single step, and no need for a metal salt.

The necessity of free and uncrowded coordination environments in biomimetic complex models: oxidative coupling by mixed-ligand cobalt(ii) complexes of diazene–disulfonamide

Importance of molecular access to Co(ii) site is shown by new tridentate disulfonamides, which stabilize uncommon 5-coordinate mixed-ligand vacant-octahedral geometries.