M-S vibrational study in three-coordinate thiolato compounds (NEt4)2[M(SC6H4-p-X)3] and (NEt4)

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

The research into adamantane-type compounds has gained momentum in recent years, yielding remarkable new applications for this class of materials. In particular, organic adamantane derivatives (AdR4) or inorganic adamantane-type compounds of the general formula [(RT)4E6] (R: organic substituent; T: group 14 atom C, Si, Ge, Sn; E: chalcogenide atom S, Se, Te, or CH2) were shown to exhibit strong nonlinear optical (NLO) properties, either second-harmonic generation (SHG) or an unprecedented type of highly-directed white-light generation (WLG) - depending on their respective crystalline or amorphous nature. The (missing) crystallinity, as well as the maximum wavelengths of the optical transitions, are controlled by the clusters' elemental composition and by the nature of the organic groups R. Very recently, it has been additionally shown that cluster cores with increased inhomogeneity, like the one in compounds [RSi{CH2Sn(E)R'}3], not only affect the chemical properties, such as increased robustness and reversible melting behaviour, but that such 'cluster glasses' form a conceptually new basis for their use in light conversion devices. These findings are likely only the tip of the iceberg, as beside elemental combinations including group 14 and group 16 elements, many more adamantane-type clusters (on the one hand) and related architectures representing extensions of adamantane-type clusters (on the other hand) are known, but have not yet been addressed in terms of their opto-electronic properties. In this review, we therefore present a survey of all known classes of adanmantane-type compounds and their respective synthetic access as well as their optical properties, if reported.

Ability of Azathiacyclen Ligands To Stop Cu(Aβ)-Induced Production of Reactive Oxygen Species: [3N1S] Is the Right Donor Set

Alzheimer's disease (AD) is an incurable neurodegenerative disease that leads to the progressive and irreversible loss of mental functions. The amyloid beta (Aβ) peptide involved in the disease is responsible for the production of damaging reactive oxygen species (ROS) when bound to Cu ions. A therapeutic approach that consists of removing Cu ions from Aβ to alter this deleterious interaction is currently being developed. In this context, we report the ability of five different 12-membered thiaazacyclen ligands to capture Cu from Aβ and to redox silence it. We propose that the presence of a sole sulfur atom in the ligand increases the rate of Cu capture and removal from Aβ, while the kinetic aspect of the chelation was an issue encountered with the 4N parent ligand. The best ligand for removing Cu from Aβ and inhibiting the associated ROS production is the 1-thia-4,7,10-triazacyclododecane [3N1S]. Indeed the replacement of more N by S atoms makes the corresponding Cu complexes easier to reduce and thus able to produce ROS on their own. In addition, the ligand with three sulfur atoms has a weaker affinity for Cu^II than Aβ, and is thus unable to remove Cu from CuAβ.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Difluorobis(pentafluoroethyl)phosphoranide: A Promising Building Block for Phosphoranidometal Complexes

Despite the fact that different metal tetrafluorophosphoranides, M[PF₄] (M = Cs, Ag, K), decompose readily, we successfully enhanced the stability of such species by the replacement of two fluorine atoms with electron withdrawing pentafluoroethyl groups. Thus, AgF adds to P(C₂F₅)₂F, yielding Ag[P(C₂F₅)₂F₂], which served as a starting material for the synthesis of mono-, bis-, and tris[difluorobis(pentafluoroethyl)phosphoranido]silver complexes. Addition of 2,2'-bipyridine allowed for the isolation of stable [Ag(bipy){P(C₂F₅)₂F₂}], whereas the reaction with the chlorides [NMe₄]Cl and CoCl₂ afforded the bis- and trisphosphoranidoargentates [NMe₄][Ag{P(C₂F₅)₂F₂}₂(OEt₂)] and [Co(NCMe)₆][Ag{P(C₂F₅)₂F₂}₃]·2MeCN, respectively. Altogether, the difluorobis(pentafluoroethyl)phosphoranido moiety serves as a novel, small, noncyclic phosphoranido ligand. It provided access to the first homoleptic phosphoranidometal complex, [Co(NCMe)₆][Ag{P(C₂F₅)₂F₂}₃]·2MeCN, which itself features the unusual structural motif of an [AgX₃]^2- ion.

Structural diversity in aroylthiourea copper complexes – formation and biological evaluation of [Cu(i)(μ-S)SCl]2, cis-Cu(ii)S2O2, trans-Cu(ii)S2O2 and Cu(i)S3 cores

Four different copper complexes containing aroylthiourea ligands displayed good interaction with CT DNA and BSA and cytotoxicity.

Influence of ligand environment on the structure and properties of silver(i) dithiocarbamate cluster-based coordination polymers and dimers

Four silver dithiocarbamate complexes have been synthesized and characterized by microanalysis.1and2are tetranuclear cluster-based coordination polymers whereas3and4are dinuclear. All complexes are strongly luminescent in solid phase.

The fictile coordination chemistry of cuprous-thiolate sites in copper chaperones

Copper plays vital roles in the active sites of cytochrome oxidase and in several other enzymes essential for human health. Copper is also highly toxic when dysregulated; because of this an elaborate array of accessory proteins have evolved which act as intracellular carriers or chaperones for the copper ions. In most cases chaperones transport cuprous copper. This review discusses some of the chemistry of these copper sites, with a view to some of the structural factors in copper coordination which are important in the biological function of these chaperones. The coordination chemistry and accessible geometries of the cuprous oxidation state are remarkably plastic and we discuss how this may relate to biological function. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.

Interplay between glutathione, Atx1 and copper: X-ray absorption spectroscopy determination of Cu(I) environment in an Atx1 dimer

X-ray absorption techniques have been used to characterise the primary coordination sphere of Cu(I) bound to glutathionate (GS-), to Atx1 and in Cu2I(GS-)2(Atx1)2, a complex recently proposed as the major form of Atx1 in the cytosol. In each complex, Cu(I) was shown to be triply coordinated. When only glutathione is provided, each Cu(I) is triply coordinated by sulphur atoms in the binuclear complex CuI2(GS-)5, involving bridging and terminal thiolates. In the presence of Atx1 and excess of glutathione, under conditions where CuI2(GS-)2(Atx1)2 is formed, each Cu(I) is triply coordinated by sulphur atoms. Given these constraints, there are two different ways for Cu(I) to bridge the Atx1 dimer: either both Cu(I) ions contribute to bridging the dimer, or only one Cu(I) ion is responsible for bridging, the other one being coordinated to two glutathione molecules. These two models are discussed as regards Cu(I) transfer to Ccc2a.