Spin-state crossover in photo-catalyzed nitrile dihydroboration via Mn-thiolate cooperation.

The role of S-donors in ligand-assisted catalysis using first-row metals has not been broadly investigated. Herein is described a combined experimental and computational mechanistic study of the dihydroboration of nitriles with pinacolborane (HBpin) catalyzed by the Mn(i) complex, Mn(κ3-SMeNS)(CO)3, that features thioether, imine, and thiolate donors. Mechanistic studies revealed that catalysis requires the presence of UV light to enter and remain in the catalytic cycle and evidence is presented for loss of two CO ligands. Stoichiometric reactions showed that HBpin reduces the imine N[double bond, length as m-dash]C of the ligand backbone in the absence of nitrile, forming an inactive off-cycle by-product. DFT calculations showed that the bifunctional thiolate donor, coordinative flexibility of the SMeNS ligand, and access to an open-shell intermediate are all crucuial to accessing low-energy intermediates during catalysis.

The electronic structure of a ß-diketiminate manganese hydride dimer.

The electronic structure of a dimeric manganese hydride catalyst supported by ß-diketiminate ligands, [(2,6-iPr2PhBDI)Mn(µ-H)]2, was investigated with density functional theory. A triple bond between the manganese centres was anticipated from simple electron-counting rules; however, calculations revealed Mn-Mn Mayer bond orders of 0.21 and 0.27 for the ferromagnetically-coupled and antiferromagnetically-coupled extremes, respectively. In accordance with experimentally determined Heisenberg exchange coupling constants of -15 ± 0.1 cm-1 (SQUID) and -10.2 ± 0.7 cm-1 (EPR), the calculated J0 value of -10.9 cm-1 confirmed that the ground state involves antiferromagnetic coupling between high spin Mn(ii)-d5 centres. The effect of steric bulk on the bond order was examined via a model study with the least sterically-demanding version of the ß-diketiminate ligand and was found to be negligible. Mixing between metal- and ß-diketiminate-based orbitals was found to be responsible for the absence of a metal-metal multiple bond. The bridging hydrides give rise to a relatively close positioning of the metal centres, while bridging atoms possessing 2p orbitals result in longer Mn-Mn distances and more stable dimers. The synthesis and characterization of the bridging hydroxide variant, [(2,6-iPr2PhBDI)Mn(µ-OH)]2, provides experimental support for these assessments.

Scope and mechanism of nitrile dihydroboration mediated by a ß-diketiminate manganese hydride catalyst.

The manganese hydride dimer, [(2,6-iPr2PhBDI)Mn(µ-H)]2, was found to mediate nitrile dihydroboration, rendering it the first manganese catalyst for this transformation. Stoichiometric experiments revealed that benzonitrile insertion affords [(2,6-iPr2PhBDI)Mn(µ-NCHC6H5)]2 en route to N,N-diborylamine formation. Density functional theory calculations reveal the precise mechanism and demonstrate that catalysis is promoted by monomeric species.

High contrast thermal deflectometry using long-wave infrared time modulated integrating cavity source.

We introduce a scalable temporally modulated long-wave infrared source design. The design makes use of an array of resistive blackbody heating elements which radiate into a custom aluminum integrating cavity. The output of the box is a rectangular slit, built to match the traditional tungsten ribbon profile for an infrared deflectometry source. Temporal modulation allows for signal isolation and improved resilience to background fluctuations in an infrared deflectometry source. Infrared deflectometry measurements using the new source design and a traditional tungsten ribbon, both with similar radiant flux, were compared for a ground glass surface, an aluminum blank, and an aluminum blank under thermal load (150 °C). Signal-to-noise ratio was ∼4 times higher for the new design and demonstrated improved source temporal stability and geometry. Further, the new design successfully measured the previously untestable hot aluminum flat. The new design improves infrared deflectometry and allows for high contrast thermal deflectometry measurements of optics under thermal load.

Taraxerone enhances alcohol oxidation via increases of alcohol dehyderogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities and gene expressions.

The present study, taraxerone (d-friedoolean-14-en-3-one) was isolated from Sedum sarmentosum with purity 96.383%, and its enhancing effects on alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities were determined: EC(50) values were 512.42 ± 3.12 and 500.16 ± 3.23 µM for ADH and ALDH, respectively. In order to obtain more information on taraxerone related with the alcohol metabolism, 40% ethanol (5 mL/kg body weight) with 0.5-1mM of taraxerone were administered to mice. The plasma alcohol and acetaldehyde concentrations of taraxerone-treated groups were significantly lowered than those of the control group (p<0.01): approximately 20-67% and 7-57% lowered for plasma alcohol and acetaldehyde, respectively. Compare to the control group, the ADH and ALDH expressions in the liver tissues were abruptly increased in the taraxerone-treated groups after ethanol exposure. In addition, taraxerone prevented catalase, superoxide dismutase, and reduced glutathione concentrations from the decrease induced by ethanol administration with the concentration dependent manner.

Positive-/negative-, erasable-/immobilized-, mono-/multi-color fluorescence image patterning of molecular-scale porous polymer film via a microcontact printing method using various chemical inks.

Fluorescent image patterns of a substituted acetylene polymer film with a large FFV were successfully obtained by a µCP method using several kinds of chemical ink compounds. PO and SCA generated positive-type fluorescent image patterns. On the other hand, an ethanolic solution of DNT generated a negative-type fluorescent image pattern due to a significant quenching effect. An NMP solution of NR gave a two-color image pattern due to an intermolecular energy transfer from PTMSDPA to NR.

Substitution position effect on photoluminescence emission and chain conformation of poly(diphenylacetylene) derivatives.

The significant variation in photoluminescence emission of poly(diphenylacetylene) derivatives according to the substitution position is due to the differences in the intramolecular pi-stack structure and chain conformation.