Design and synthesis of a new binucleating ligand via cobalt-promoted C-N bond fusion reaction. Ligand isolation and its coordination to nickel,palladium, and platinum

A new polydentate bridging ligand, NH(4)C(5)N=NC(6)H(4)N(H)C(5)H(4)N (HL(2)), is synthesized by the cobalt-mediated phenyl ring amination of coordinated NH(4)C(5)N=NC(6)H(5). The green cobalt complex intermediate [Co(L(2))(2)](ClO(4)), [1](ClO(4)), and the free ligand HL(2) were isolated and characterized. The X-ray structure of [H(2)L(2)](ClO(4)) is reported. The ligand, upon deprotonation, behaves as a bridging ligand. It reacts with NiCl(2).6H(2)O and Na(2)[PdCl(4)] to produce dimetallic complexes, [Ni(2)Cl(2)(L(2))(2)], 2, and [Pd(2)(L(2))(2)](ClO(4))(2), [3](ClO(4))(2), respectively. X-ray structures of these two dimetallic complexes are reported. The structure of the dinickel complex, in particular, is unique. In this complex, the two deprotonated secondary amine nitrogens of the two [L(2)](-) ligands bind to two nickel centers simultaneously forming a planar Ni(2)N(2) arrangement. The complex [3](ClO(4))(2) is diamagnetic while the complex 2 is paramagnetic. The results of magnetic measurements on the dinickel complex in the temperature range 1.8-300 K are reported. The system can be described as a single spin S = 2 in the low-temperature range T < J/k whereas at high temperatures, T > J/k, it behaves as two independent spins S = 1.The reaction of [L(2)](-) with K(2)[PtCl(4)], however, yielded a monometallic platinum complex, [PtCl(3)(L(2))], 5, where the pyridyl nitrogen of the aminopyridyl function remained unused. The X-ray structure of the complex 4a is reported. The bond lengths along the ligand backbones in all the complexes indicate extensive pi-delocalization. Spectral data of the complexes are reported and compared.     

Synthesis and characterization of high bio-based content unsaturated polyester resin for wood coating from itaconic acid: Effect of various reactive diluents as an alternative to styrene

The present work focuses on the ability of 2-hydroxyethyl methacrylate (HEMA), isobornyl methacrylate (IBOMA) and methyl methacrylate (MMA) as reactive diluents to replace styrene in unsaturated polyester resin based on itaconic acid, sebacic acid, 1,4-Butanediol, 1,6-Hexanediol and glycerol. The structural analysis confirmed the presence of itaconate linkages in the UPs. The synthesized resins were characterized by infrared spectroscopy and their physiochemical properties such as appearance, viscosity, acid value, %volatile content, curing characteristics like gel time, peak exotherm temperature and total cure time. Among all the resins formed; the resin based on 1,6-Hexanediol showed optimum molecular weight and viscosity needed for final application. The cured resins were investigated for their thermal stability by thermo-gravimetric analysis which revealed that all the diluted resins had good thermal stability. From the results it could be concluded that styrene-free bio-based unsaturated polyester resin can be synthesized having properties equivalent to the commercial styrene based resin.GRAPHICAL ABSTRACT     

Synthesis of homopolymers and copolymers containing an active ester of acrylic acid by RAFT: Scaffolds for controlling polyvalent ligand display

We describe the synthesis of activated homopolymers and copolymers of controlled molecular weight based on the controlled radical polymerization of N‐acryloyloxysuccinimide (NAS) by reversible addition fragmentation chain transfer (RAFT). We synthesized activated homopolymers in a range of molecular weights with polydispersities between 1 and 1.2. The attachment of an inhibitory peptide to the activated polymer backbone yielded a potent controlled molecular weight polyvalent inhibitor of anthrax toxin. To provide greater control over the placement of the peptides along the polymer backbone, we also used a semibatch copolymerization method to synthesize copolymers of NAS and acrylamide (AAm). This approach enabled the synthesis of copolymers with control over the placement of peptide‐reactive NAS monomers along an inert backbone; subsequent functionalization of NAS with peptide yielded well‐defined polyvalent anthrax toxin inhibitors that differed in their potencies. These strategies for controlling molecular weight, ligand density, and ligand placement will be broadly applicable for designing potent polyvalent inhibitors for a variety of pathogens and toxins and for elucidating structure–activity relationships in these systems. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7249–7257, 2008     

The HDAC/HSP90 Inhibitor G570 Attenuated Blue Light-Induced Cell Migration in RPE Cells and Neovascularization in Mice through Decreased VEGF Production

Age-related macular degeneration (AMD) occurs due to an abnormality of retinal pigment epithelium (RPE) cells that leads to gradual degeneration of the macula. Currently, AMD drug pipelines are endowed with limited options, and anti-VEGF agents stand as the dominantly employed therapy. Despite the proven efficacy of such agents, the evidenced side effects associated with their use underscore the need to elucidate other mechanisms involved and identify additional molecular targets for the sake of therapy improvement. The previous literature provided us with a solid rationale to preliminarily explore the potential of selective HDAC6 and HSP90 inhibitors to treat wet AMD. Rather than furnishing single-target agents (either HDAC6 or HSP90 inhibitor), this study recruited scaffolds endowed with the ability to concomitantly modulate both targets (HDAC6 and HSP90) for exploration. This plan was anticipated to accomplish the important goal of extracting amplified benefits via dual inhibition (HDAC6/HSP90) in wet AMD. As a result, G570 (indoline-based hydroxamate), a dual selective HDAC6-HSP90 inhibitor exerting its effects at micromolar concentrations, was pinpointed in the present endeavor to attenuate blue light-induced cell migration and retinal neovascularization by inhibiting VEGF production. In addition to the identification of a potential chemical tool (G570), the outcome of this study validates the candidate HDAC6-HSP90 as a compelling target for the development of futuristic therapeutics for wet AMD.     

Thermal–electrical–structural performances of hot heat exchanger with different internal fins of thermoelectric generator for low power generation application

Journal of Thermal Analysis and Calorimetry - In this study, an electro-thermo-structural coupled numerical analysis is conducted to evaluate the thermal, electrical, and structural performances of...