Zinc coordination to the bapbpy ligand in homogeneous solutions and at liposomes: zinc detection via fluorescence enhancement

Influence of a series of pyridine ligands on the structure and photophysical properties of Cd(ii) complexes

Five Cd(ii) complexes based on α-acetamidocinnamic acid (HACA) and a set of N,N^N and N^N^N-pyridine (dPy) yield complexes with diverse nuclearities and enhanced quantum yields, benefiting from the chelation enhanced effect (CHEF) of dPy.

The crystal structure of N 6,N 6′-di(pyridin-2-yl)-[2,2′-bipyridine]-6,6′-diamine, C20H16N6

C20H16N6, monoclinic, P21/c (no. 14), a = 7.6623(4) Å, b = 11.8206(5) Å, c = 8.8960(4) Å, β = 91.825(2)°,V = 805.33(7) Å3, Z = 2, R gt (F) = 0.0577, wR ref(F 2) = 0.1588, T = 200(2) K.

Electrocatalytic Hydrogen Evolution with a Cobalt Complex Bearing Pendant Proton Relays: Acid Strength and Applied Potential Govern Mechanism and Stability

[Co(bapbpy)Cl]⁺ (bapbpy: 6,6'-bis(2-aminopyridyl)-2,2'-bipyridine) is a polypyridyl cobalt(II) complex bearing both a redox-active bipyridine ligand and pendant proton relays. This compound catalyzes electro-assisted H₂ evolution in DMF with distinct mechanisms depending on the strength of the acid used as the proton source (pK_a values ranging from 3.4 to 13.5 in DMF) and the applied potential. Electrochemical studies combining cyclic voltammetry and bulk electrolysis measurements enabled one to bring out four distinct catalytic processes. Where applicable, relevant kinetic information were obtained using either foot-of-the-wave analysis (FOWA) or analytical treatment of bulk electrolysis experiments. Among the different catalytic pathways identified in this study, a clear relationship between the catalyst performances and stability was evidenced. These results draw attention to a number of interesting considerations and may help in the development of future adequately designed catalysts.

2,2'-Dipyridylamines: more than just sister members of the bipyridine family. Applications and achievements in homogeneous catalysis and photoluminescent materials

2,2'-Dipyridylamines (dpa) and related compounds belong to the family of polydentate nitrogen ligands. More than a century has passed since their first report but new complexes and applications have been emerging in recent years owing to the versatility of dpa-based architectures. This review aims to present and highlight the main achievements attained with dpa-containing metal complexes in the domains of homogeneous catalysis and luminescent materials.

A cationic tetrahedral Zn(ii) cluster based on a new salicylamide imine multidentate ligand: synthesis, structure and fluorescence sensing study

We present here a monocationic Zn^II tetrahedral cluster which is extremely stable and exhibits highly sensitive and selective recognition of phosphates against other common anions in water containing media.

Zn2+ Induced Irreversible Aggregation, Stacking, and Leakage of Choline Phosphate Liposomes

The interaction between lipids and metal ions is important for metal sensing, cellular signal transduction, and oxidative lipid damage. While most previous work overlooked the phosphate group of lipids for metal binding, we herein highlight its importance. Phosphocholine (PC) and its headgroup inversed choline phosphate (CP) lipids were used to prepare liposomes. From dynamic light scattering (DLS), Zn²⁺ causes significant aggregation or fusion of the CP liposomes, but not PC liposomes. The size change induced by Zn²⁺ is not fully reversed by adding EDTA, implying liposome fusion induced by Zn²⁺. Isothermal titration calorimetry (ITC) shows that binding between Zn²⁺ and CP liposomes is endothermic with a K_d of 110 μM Zn²⁺, suggesting an entropy driven reaction likely due to the release of bound water. In comparison, no heat was detected by titrating Zn²⁺ into PC liposomes or Ca²⁺ into CP liposomes. Furthermore, Zn²⁺ causes a transient leakage of the CP liposomes, and further leakage is observed upon removing Zn²⁺ by EDTA. Transmission electron microscopy (TEM) with negative stained samples showed multilamellar CP lipid structures attributable to Zn²⁺ sandwiched between lipid bilayers, leading to a proposed reaction mechanism. This work provides an interesting system for studying metal interacting with terminal phosphate groups in liposomes, affecting the size, charge, and membrane integrity of the liposomes.

Binding of a ruthenium complex to a thioether ligand embedded in a negatively charged lipid bilayer: a two-step mechanism

The interaction between the ruthenium polypyridyl complex [Ru(terpy)(dcbpy)(H2O)](2+) (terpy = 2,2';6',2"-terpyridine, dcbpy = 6,6'-dichloro-2,2'-bipyridine) and phospholipid membranes containing either thioether ligands or cholesterol were investigated using UV-visible spectroscopy, Langmuir-Blodgett monolayer surface pressure measurements, and isothermal titration calorimety (ITC). When embedded in a membrane, the thioether ligand coordinated to the dicationic metal complex only when the phospholipids of the membrane were negatively charged, that is, in the presence of attractive electrostatic interaction. In such a case coordination is much faster than in homogeneous conditions. A two-step model for the coordination of the metal complex to the membrane-embedded sulfur ligand is proposed, in which adsorption of the complex to the negative surface of the monolayers or bilayers occurs within minutes, whereas formation of the coordination bond between the surface-bound metal complex and ligand takes hours. Finally, adsorption of the aqua complex to the membrane is driven by entropy. It does not involve insertion of the metal complex into the hydrophobic lipid layer, but rather simple electrostatic adsorption at the water-bilayer interface.