The performance of carbon fiber-reinforced composites is dependent to a great extent on the properties of fiber-matrix interface. To improve the interfacial properties in carbon fiber/epoxy composites, we directly introduced graphene oxide (GO) sheets dispersed in the fiber sizing onto the surface of individual carbon fibers. The applied graphite oxide, which could be exfoliated to single-layer GO sheets, was verified by atomic force microscope (AFM). The surface topography of modified carbon fibers and the distribution of GO sheets in the interfacial region of carbon fibers were detected by scanning electron microscopy (SEM). The interfacial properties between carbon fiber and matrix were investigated by microbond test and three-point short beam shear test. The tensile properties of unidirectional (UD) composites were investigated in accordance with ASTM standards. The results of the tests reveal an improved interfacial and tensile properties in GO-modified carbon fiber composites. Furthermore, significant enhancement of interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and tensile properties was achieved in the composites when only 5 wt % of GO sheets introduced in the fiber sizing. This means that an alternative method for improving the interfacial and tensile properties of carbon fiber composites by controlling the fiber-matrix interface was developed. Such multiscale reinforced composites show great potential with their improved mechanical performance to be likely applied in the aerospace and automotive industries.

Inhibition of O-GlcNAcase (OGA) has emerged as a promising therapeutic approach to treat tau pathology in neurodegenerative diseases such as Alzheimer’s disease and progressive supranuclear palsy. Beginning with carbohydrate-based lead molecules, we pursued an optimization strategy of reducing polar surface area to align the desired drug-like properties of potency, selectivity, high central nervous system (CNS) exposure, metabolic stability, favorable pharmacokinetics, and robust in vivo pharmacodynamic response. Herein, we describe the medicinal chemistry and pharmacological studies that led to the identification of (3aR,5S,6S,7R,7aR)-5-(difluoromethyl)-2-(ethylamino)-3a,6,7,7a-tetrahydro-5H-pyrano­[3,2-d]­thiazole-6,7-diol 42 (MK-8719), a highly potent and selective OGA inhibitor with excellent CNS penetration that has been advanced to first-in-human phase I clinical trials.

The new complexes 1,1′-bis(5-(2,2′-bithienyl))ferrocene (2) and 1,1′-bis(5-(2,2′:5′,2′′-terthienyl))ferrocene (3) have been synthesized by coupling 1,1′-bis(2-thienyl)ferrocene (1) with 2-bromothiophene and 5-bromo-2,2′-bithiophene, respectively. The cyclic voltammograms of 1-3 contain a reversible Fe II/III wave with E 1/2 between 0.37 and 0.46 V vs SCE and irreversible thiophene-based oxidation waves at higher potentials. These compounds can be electrochemically oxidized to yield solutions of the monocations 1 + -3 + . The visible-near-IR spectra of these monocations all contain low-energy bands due to an oligothienyl group to Fe III charge-transfer transition. The absorption maxima and intensities of these bands correlate to the length of the conjugation in the oligothienyl group. Above the thiophene oxidation potential and by careful exclusion of water, 2 and 3 electropolymerize resulting in the deposition of electrochromic films on the electrode surface. The films are golden-red and stable when neutral and become black upon oxidation. The cyclic voltammetry of the film growth process and the formation of electroactive films indicate that the films are conductive. Spectroelectrochemical characterization of the films demonstrates that broad, low-energy absorptions appear upon oxidation of the ferrocenyl centers and that stronger and much broader bands appear upon full oxidation of the films.

The series of ruthenium(II) mono(oligothienylacetylide) complexes trans-Ru(dppm) 2 (Cl)-(CtCR) (dppm ) Ph 2 PCH 2 PPh 2 ; R ) 2-thienyl (1a), 5-(2,2′-bithienyl) (1b), and 5-(2,2′:5′,2′′-terthienyl) (1c)) and bis(oligothienylacetylide) complexes trans-Ru(dppm) 2 (CtCR) 2 (R ) 2-thienyl (2a), 5-(2,2′-bithienyl) (2b), and 5-(2,2′:5′,2′′-terthienyl) (2c)) were synthesized. Complex 2c was crystallographically characterized. The cyclic voltammograms of complexes 1a-c all contain two oxidation waves, a Ru(II/III) wave and a ligand-based oxidation wave. As the length of the conjugated oligothienyl ligand increases, the thiophene-based oxidation wave becomes more chemically reversible. Complexes 2a-c all have a Ru(II/III) wave in their cyclic voltammograms, as well as multiple ligand-based oxidation waves. Complexes 2b and 2c both form films on the electrode surfaces upon repeated cycling in the range 0-1.4 V vs SCE. The UV-vis spectra of complexes 1a-c and 2a-c all contain intense absorptions due to the π-π* transition in the oligothienyl ligand, and these appear at lower energy than the π-π* transitions in the corresponding oligothiophenes. The monocations 1c + and 2c + were synthesized in solution at -20°C and were characterized by visible and near-IR spectroscopy. The π-π* transitions of the terthienyl ligand in 1c + and 2c + shift to higher energy compared with the analogous transitions in 1c and 2c, and a series of LMCT absorption bands of high intensity appear between 500 and 700 nm and between 900 and 1700 nm, respectively. These results support the conclusion that the π system of the conjugated oligothienyl ligands interacts strongly with the Ru(III) center.

The synthesis and properties of [cis-Ru(dppm)2(C⋮CFc)2]CuI (dppm = Ph2PCH2PPh2, Fc = ferrocenyl) (1) and trans,trans,trans-Ru(PBu3)2(CO)(L)(C⋮CFc)2 (3, L = CO; 4, L = pyridine; 5, L = P(OMe)3) are reported. The ruthenium bisacetylide bridges in these complexes allow electronic interaction between the terminal ferrocenyl groups. The interaction is enhanced when the ancillary ligands on the ruthenium center are electron donors and lessened when the ligands are acceptors. Complex 1 was prepared in 70% yield by the coupling of FcC⋮CSn(n-Bu)3 and cis- or trans-RuCl2(dppm)2 in the presence of excess CuI and was crystallographically characterized. Removal of the coordinated CuI from 1 with excess P(OMe)3 yields trans-Ru(dppm)2(C⋮CFc)2 (2). Reaction of 2 with CuI yields 1. trans,trans,trans-Ru(PBu3)2(CO)2(C⋮CFc)2 (3) was synthesized from RuCl2(CO)2(PBu3)2 and FcC⋮CSn(n-Bu)3 using a CuI catalyst and was crystallographically characterized. Reaction of 3 with excess pyridine yields trans,trans,trans-Ru(PBu3)2(CO)(py)(C⋮CFc)2 (4). The reaction is reversible; 3 may be obtained by reacting 4 with excess carbon monoxide. Reaction of 4 with P(OMe)3 yields trans,trans,trans-Ru(PBu3)2(CO)(P(OMe)3)(C⋮CFc)2 (5). Dications of all the complexes were prepared by oxidation with 2 equiv of FcPF6, and monocations were prepared in solution by reaction of the neutral complexes with the dications. The difference between the first and second ferrocenyl oxidations (ΔE 1/2) in the cyclic voltammograms of 1, 3, 4, and 5 are 0.14, 0.09, 0.13, and 0.15 V, respectively. Characterization of the complexes by visible, IR, and near-IR spectroscopy supports the conclusion that the ligand environment of the ruthenium center affects the extent of electronic delocalization between the ferrocenyl groups.

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