The heavier analogues of graphene,
namely silicene and germanene,
are known to be buckled. Such buckling leads to interesting properties
like direct band gap in hydrogenated germanene, known as germanane.
This article shows that the sequential replacement of C by Ge in benzene
leads to increasing buckling with the maximal buckling distance (d = 0.61 Å) in Ge6H6. The origin
of such buckling induced lowering of symmetry (D
6h
→ D
3d
) is traced to pseudo Jahn–Teller (PJT) distortion
along the b2g normal mode arising out of mixing of the
nondegenerate (A1g) ground state with low lying (Δ0 = 4.36 eV) excited state of B2g symmetry. Buckling
also leads to enhanced chemical reactivity of germanene toward hydrogen
to form germanane. The large affinity of germanene toward hydrogenation
explains the experimental synthesis of exfoliated layers of germanane
by Goldberger and co-workers [ACS Nano2013744144421]. Germanene → germanane
formation leads to the opening up of a large band gap making hydrogenation
a chemical route to control the electronic properties in these new
2D materials. The presence of buckling in germanene leads to higher
hole reorganization energies than polyaromatic hydrocarbons (PAH)
of the same nuclearity.
Design of an efficient new catalyst that can mimic the enzymatic pathway for catalytic dehydrogenation of liquid fuels like alcohols is described in this report. The catalyst is a nickel(II) complex of 2,6-bis(phenylazo)pyridine ligand (L), which possesses the above requisite with excellent catalytic efficiencies for controlled dehydrogenation of alcohols using ligand-based redox couple. Mechanistic studies supported by density functional theory calculations revealed that the catalytic cycle involves hydrogen atom transfer via quantum mechanical tunneling with significant k/k isotope effect of 12.2 ± 0.1 at 300 K. A hydrogenated intermediate compound, [NiCl(HL)], is isolated and characterized. The results are promising in the context of design of cheap and efficient earth-abundant metal catalyst for alcohol oxidation and hydrogen storage.
A complete transmetalation has been achieved on a barium metal-organic framework (MOF), leading to the isolation of a new Tb-MOF in a single-crystal (SC) to single-crystal (SC) fashion. It leads to the transformation of an anionic framework with cations in the pore to one that is neutral. The mechanistic studies proposed a core-shell metal exchange through dissociation of metal-ligand bonds. This Tb-MOF exhibits enhanced photoluminescence and acts as a selective sensor for phosphate anion in aqueous medium. Thus, this work not only provides a method to functionalize a MOF that can have potential application in sensing but also elucidates the formation mechanism of the resulting MOF.
Electroprotic storage materials, though invaluable in energy-related research, are scanty among non-natural compounds. Herein, we report a zinc(II) complex of the ligand 2,6-bis(phenylazo)pyridine (L), which acts as a multiple electron and proton reservoir during catalytic dehydrogenation of alcohols to aldehydes/ketones. The redox-inactive metal ion Zn(II) serves as an oxophilic Lewis acid, while the ligand behaves as efficient storage of electron and proton. Synthesis, X-ray structure, and spectral characterizations of the catalyst, ZnLCl (1a) along with the two hydrogenated complexes of 1a, ZnHLCl (1b), and ZnHLCl (1c) are reported. It has been argued that the reversible azo-hydrazo redox couple of 1a controls aerobic dehydrogenation of alcohols. Hydrogenated complexes are hyper-reactive and quantitatively reduce O and para-benzoquinone to HO and para-hydroquinone, respectively. Plausible mechanistic pathways for alcohol oxidation are discussed based on controlled experiments, isotope labeling, and spectral analysis of intermediates.
Blue, green, orange-red, red and NIR emitting gold quantum clusters have been prepared in aqueous media by using a bioactive peptide glutathione (reduced) at physiological pH. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analyses show that the core structure sizes of the five different gold clusters are Au7 (blue), Au16 (green), Au19 (orange-red), Au21 (red) and Au22 (NIR). The photo-stability and pH-stability of these quantum clusters have been measured, and these are photo-stable against continuous UV irradiation for a few hours. They also exhibit moderate to good pH-stability within the pH range of 5-12.5. A computational study reveals the organisation of gold atoms in the thiolate-protected blue quantum cluster and its several structural parameters, including the mode of interaction of ligand molecules with Au atoms in the Au7 cluster. Interestingly, it has been found that NIR emitting gold quantum cluster can easily be internalized into the adenocarcinomic human alveolar basal epithelial cell line (A549 cell line). Moreover, a MTT assay indicates that our NIR emitting gold quantum cluster show very low cytotoxicy to A549 cancer cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.