Copper(II) complexes of tridentate selenobisphenolate ligand in mixed ligand environments: Synthesis, crystal structure, EPR and electrochemical studies

Structures, properties and applications of Cu(II) complexes with tridentate donor ligands

Tridentate ligands offer theree donor atoms to coordinate to metal ions. The remaining vacant coordination sites on the metal ions provided opportunities to implement additional co-ligands to generate complexes with desired properties. Herein we discuss selected examples of Cu(ii) complexes with tridentate ligands utilizing combinations of N, O, S, and Se donors, focusing on effects of ligand flexibility/rigidity on their coordination modes, properties and applications.

Solvent-Dependent Facile Synthesis of Diaryl Selenides and Biphenols Employing Selenium Dioxide

Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so‐called “privileged ligands”. We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which could act as pincer‐like ligands with further applications in organic synthesis or as ligands in transition metal catalysis.

Stabilization of MIV = Ti, Zr, Hf, Ce, and Th using a selenium bis(phenolate) ligand

We report M(iv) M = Ti, Zr, Hf, Ce, and Th, complexes of a selenium bis(phenolate) ligand, 2,2'-selenobis(4,6-di-tert-butylphenol), (H(2)(Ar)OSeO), 1. Reaction of Ti(NEt(2))(4) with two equivalents of affords Ti((Ar)OSeO)(2), 2. Salt metathesis of ZrCl(4) and HfCl(4) with two equivalents of Na(2)(Ar)OSeO produces Zr((Ar)OSeO)(2)(THF), 3, and Hf((Ar)OSeO)(2)(THF), 4, respectively. Protonolysis of ThCl[N(SiMe(3))(2)](3) with two equivalents of yields Th((Ar)OSeO)(2)(THF)(2), 5. Salt metathesis of Ce(OTf)(3) and two equivalents of Na(2)(Ar)OSeO produces [Na(THF)(3)][Ce((Ar)OSeO)(2)], which was oxidized in situ using 0.5 equivalents of I(2) to yield the diamagnetic Ce(iv) product, Ce((Ar)OSeO)(2)(THF)(2), 6. Addition of 2,2'-bipyridyl to forms Ce((Ar)OSeO)(2)(bipy), 6a. Each diamagnetic complex was characterized using (1)H, (13)C, and (77)Se NMR and IR spectroscopy and the structures of 2-6a were established with X-ray crystallography. Electrochemical measurements using cyclic voltammetry on complexes 2, 5, and 6a re also reported.

Selective coordination ability of sulfamethazine Schiff-base ligand towards copper(II): molecular structures, spectral and SAR study

In the present work, a combined experimental and theoretical study of the N-(4,6-Dimethyl-pyrimidin-2-yl)-4-[(2-hydroxy-benzylidene)amino]benzenesulfonamide ligand (H2L) and its mononuclear and magnetically diluted binuclear Cu(II) complexes has been performed using IR, TG/DTA, magnetic, EPR, and conductivity measurements. Calculated g-tensor values showed best agreement with experimental values from EPR when carried out using the MPW1PW91 functional. Coordination of H2L to a Cu(II) center, regardless of the binding site and Cu:L stoichiometry, leads to a significant decrease in the antibacterial activity compared to the free ligand as well as reference drugs in the case of Staphylococcus aureus. Structural-activity relationship suggests that ELUMO, ΔE, dipole moment, polarizability and electrophilicity index were the most significant descriptors for the correlation with the antibacterial activity.