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Selective C-C bond cleavage under ambient conditions is a challenging chemical transformation that can be a valuable tool for organic syntheses and macromolecular disassembly. Herein, we show that base metal vanadium photocatalysts can harvest visible light to effect the chemoselective C-C bond cleavage of lignin model compounds under ambient conditions. Lignin, a major aromatic constituent of non-food biomass, is an inexpensive, accessible source of fine chemical feedstocks such as phenols and aryl ethers. However, existing lignin degradation technologies are harsh and indiscriminately degrade valuable functional groups to produce intractable mixtures. The selective, photocatalytic depolymerization of lignin remains underexplored. In the course of our studies on lignin model compounds, we have uncovered a new C-C activation reaction that takes place under exceptionally mild conditions with high conversions. We present our fundamental studies on representative lignin model compounds, with the aim of expanding and generalizing the substrate scope in the future. Visible light is employed in the presence of earth-abundant vanadium oxo catalysts under ambient conditions. Selective C-C bond cleavage leads to valuable and functionally rich fine chemicals such as substituted aryl aldehydes and formates. Isotope labeling experiments, product analyses, and intermediate radical trapping, together with density functional theory studies, suggest a unique pathway that involves a photogenerated T1 state during the C-C bond cleavage reactions. Our study demonstrates a sustainable approach to harvest sunlight for an unusual, selective bond activation, which can potentially be applied in organic transformations and biomass valorization. © 2015 The Royal Society of Chemistry.

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Chemical Science

Selective photocatalytic C-C bond cleavage under ambient conditions with earth abundant vanadium complexes

Reactions of the amidinate-stabilized silicon(II) bis(trimethylsilyl)amide [LSiN(SiMe3)2], {L = PhC(NtBu)2, 1} with a stiochiometric amount of elemental sulfur, selenium and tellurium afforded the first stable silanechalcogenones comprising an acyclic amido substituent [L{N(SiMe3)2}Si=E] {E = S (2), Se (3) or Te (4)}. All compounds were characterized by X-ray crystallography and multinuclear NMR spectroscopy. The results illustrate that these compounds possess some silicon-chalcogen double bond character. Reactions of the amidinate-stabilized silicon(II) bis(trimethylsilyl)amide [LSiN(SiMe3)2], {L = PhC(NtBu)2, 1} with a stiochiometric amount of elemental sulfur, selenium and tellurium afforded the first stable silanechalcogenones comprising an acyclic amido substituent, [L{N(SiMe3)2}Si=E] {E = S (2), Se (3) or Te (4)}. © 2015 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim.

European Journal of Inorganic Chemistry

Acyclic Amido-Containing Silanechalcogenones

A catalytically active aluminum-based system for Diels-Alder transformations is reported. The system was generated by mixing a β-diketiminate-stabilized aluminum bistriflate compound with Na[BArCl4] (ArCl=3,5-Cl2C6H3). Solid-state analysis of the catalytic system reveals a unique structure incorporating a two-dimensional coordination polymer. According to the experimental results obtained from several Diels-Alder transformations, the aluminum-based system appears to be a more practical and more robust alternative to the recently reported compounds based on carbon and silicon cations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemistry - A European Journal

A Well-Defined Aluminum-Based Lewis Acid as an Effective Catalyst for Diels-Alder Transformations

Reaction of 4-CN-PhOH with [ClP(μ-NtBu)]2 (1) (2:1 ratio) in the presence of Et3N produced the functionalized cyclodiphosph(III/III)azane [(4-CN-PhO)P(μ-NtBu)]2 (2). Oxidation of 2 produced cyclodiphosph(V/V)azanes [(4-CN-PhO)(E)P(μ-NtBu)]2 [E = O (3), S (4), and Se (5)]. This is the first example of a series of cyclodiphosph(V/V)azane derivatives obtained from a single cyclophosph(III/III)azane precursor where all the accessible chalcogen oxidized products are air-stable over prolonged periods of time. (Figure Presented). © 2015 American Chemical Society.

Inorganic Chemistry

Synthesis and Hydrolytic Studies on the Air-Stable [(4-CN-PhO)(E)P(μ-NtBu)]2 (E = O, S, and Se) Cyclodiphosphazanes

Journal of Physics B: Atomic, Molecular and Optical Physics

Erratum: Generating continuous variable entangled states for quantum teleportation using a superposition of number-conserving operations (2015 J. Phys. B: At. Mol. Opt. Phys. 48 185502)

Degradation of lignin model compounds through selective C-C bond cleavage using earth abundant vanadium catalysts driven by visible light

The coordination chemistry of the amidinate-stabilized silicon(I) dimer toward group 9 metal complexes is described. The reaction of [LSi:]2 (1, L = PhC(NtBu)2) with [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) in toluene at ambient temperature afforded the base-stabilized silicon(I) dimer-iridium complex [LSi{Ir(cod)-μ-Cl-Ir(cod)}SiL][(cod)IrCl2] (2). In contrast, the reaction of 1 with [Rh(cod)Cl]2 in toluene at ambient temperature afforded a mixture of the amidinate-stabilized silicon(I) dimer-rhodium complex [LSi{Rh(cod)-μ-Cl-Rh(cod)}SiL] (3) and the dimeric amidinate-stabilized rhodosilylene [(LSi)μ-{Rh(μ-Cl)2Rh(cod)}]2 (4). Moreover, the latter reacted with PPh3 to afford a mixture of the Wilkinsons catalyst [(PPh3)3RhCl] and the dimeric rhodosilylene complex [(LSi)μ-{RhCl(PPh3)}]2 (5), which underwent a rearrangement to form the rhodosilylene-phosphidorhodium dimer (LSi)[μ-{RhCl(PPh3)}μ-{RhCl(LSiPh)}](PPh2) (6). Compounds 2-6 were characterized by NMR spectroscopy and X-ray crystallography. In addition, DFT calculations of compound 4 were performed to understand its electronic structure. © 2015 American Chemical Society.

Amidinate-Stabilized Group 9 Metal-Silicon(I) Dimer and -Silylene Complexes

Reaction of equimolar trans-[Re(NPh)(PPh3)2Cl3] with H2L, a 1: 1 Schiff-base condensate of salicylaldehyde and ethanolamine, in chloroform gives trans-[Re(NPh)(HL)(PPh3)Cl2] (1a) in good yield. 1a has been characterized by C, H, and N microanalyses, FTIR and UV-vis spectra. The X-ray crystal structure of 1a reveals that it is an octahedral trans-Cl,Cl phenylimidorhenium(V) complex. The rhenium center has an N2OCl2P coordination sphere. 1a crystallizes in the monoclinic space group P21/c with a = 11.2391(5), b = 16.4848(7), c = 16.3761(8) Å, V = 3034.0(2) Å3 and Z = 4. The electrochemical aspects of 1a have been studied. Electrochemical studies of 1a in dichloromethane show a quasi-reversible Re(V) to Re(VI) oxidation at 1.128 V versus Ag/AgCl. This redox potential reasonably matches the calculated redox potential, 1.186 V versus Ag/AgCl. Geometry optimization of the trans-Cl,Cl 1a vis-à-vis its cis analog, cis-Cl,Cl 1b, have been performed at the level of density functional theory (DFT). It is revealed that 1a is more stable than 1b by 21.6 kcal per mole of energy in the gas phase. © 2015 Taylor & Francis.

Journal of Coordination Chemistry

A new phenylimidorhenium(V) compound containing the 2-[(2-hydroxyethylimino)methyl]phenol Schiff-base ligand: Experimental and theoretical aspects

Three osmium analogues 3a-3c of hydroxytamoxifen were prepared. The antiproliferative effects of these complexes were measured against two breast cancer cell lines (MCF-7 and MDA-MB-231) and compared with those of their homologues of ferrocene (1a-1c) and ruthenocene (2a-2c). The tamoxifen-like complexes 2c and 3c derived from osmium and ruthenium show good cytotoxicities against the two cell lines (IC50 values between 2 and 3 μM), albeit lower than those of ferrocifen 1c (IC50 between 0.5 and 0.8 μM). These complexes induce senescence of the cells at low concentration (0.5 μM). The mono- and diphenol complexes of osmium and ruthenium show little cytotoxicity against the two cell lines (2a, 2b, 3a, 3b; IC50 ≈ 30 μM), whereas the iron analogues show high cytotoxicity (1a and 1b; IC50 = 0.6-1.1 μM against MDA-MB-231). Further studies show that the cytotoxicity of the tamoxifen-like complexes of ruthenium and osmium is multifactorial and is partly due to the presence of the amino chain. Added to this is an effect of the metal center that could be due to a difference in the rate of formation, solubility, and stability of the corresponding quinone methides or to a difference in the acidity of the phenol protons. This work reveals the differences in the mechanisms of action that exist among the complexes of these three metallocenes. The uniqueness of the ferrocene complexes is underlined, but the cytotoxicity of the tamoxifen-like complexes of osmium and ruthenium is also demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, Characterization, and Biological Properties of Osmium-Based Tamoxifen Derivatives - Comparison with Their Homologues in the Iron and Ruthenium Series

In order to address the increasing demands for clean energy, it is highly desirable to explore new electrode materials to improve the efficiency of lithium ion batteries (LIBs). In this work, we report the successful synthesis of a crystalline (H3O)(2)(enH(2))Cu8Sn3S12 material via a surfactant-thermal strategy. The crystal structure analysis shows that the as-prepared chalcogenide has 3D interconnected channels occupied by disordered H(2)en(2+) and H3O+. Taking advantage of porous structures and H(2)en(2+) and H3O+ as stabilizers, (H3O)(2)(enH(2)) Cu8Sn3S12 has been explored as an anode material for lithium ion batteries. Our results exhibit a high capacity of 563 mA h g(-1) at a current density of 0.1 A g(-1) after 100 cycles. In addition, outstanding cycling properties are demonstrated with only 7.2\% capacity loss from the 5th to 100th cycle. Our research could provide insight into the exploration of crystalline ternary thiostannate for lithium ion batteries in the future.