Homo‐ and Heteroleptic Bismuth(III/V) Thiolates from N‐Heterocyclic Thiones: Synthesis,Structure and Anti‐Microbial Activity

Homo‐ and heteroleptic bismuth thiolato complexes have been synthesised and characterised from biologically relevant tetrazole‐, imidazole‐, thiadiazole‐ and thiazole‐based heterocyclic thiones (thiols): 1‐methyl‐1H‐tetrazole‐5‐thiol (1‐MMTZ(H)); 4‐methyl‐4H‐1,2,4‐triazole‐3‐thiol (4‐MTT(H)); 1‐methyl‐1H‐imidazole‐2‐thiol (2‐MMI(H)); 5‐methyl‐1,3,4‐thiadiazole‐2‐thiol (5‐MMTD(H)); 1,3,4‐thiadiazole‐2‐dithiol (2,5‐DMTD(H)₂); and 4‐(4‐bromophenyl)thiazole‐2‐thiol (4‐BrMTD(H)). Reaction of BiPh₃ with 1‐MMTZ(H) produced the rare Bi^V thiolato complex [BiPh(1‐MMTZ)₄], which undergoes reduction in DMSO to give [BiPh(1‐MMTZ)₂{(1‐MMTZ(H)}₂]. Reactions with PhBiCl₂ or BiPh₃ generally produced monophenylbismuth thiolates, [BiPh(SR)₂]. The crystal structures of [BiPh(1‐MMTZ)₂{1‐MMTZ(H)}₂], [BiPh(5‐MMTD)₂], [BiPh{2,5‐DMTD(H)}₂(Me₂C?O)] and [Bi(4‐BrMTD)₃] were obtained. Evaluation of the bactericidal properties against M. smegmatis, S. aureus, MRSA, VRE, E. faecalis and E. coli showed complexes containing the anionic ligands 1‐ MMTZ, 4‐MTT and 4‐BrMTD to be most effective. The dithiolato dithione complexes [BiPh(4‐MTT)₂{4‐MTT(H)}₂] and [BiPh(1‐MMTZ)₂{1‐MMTZ(H)}₂] were most effective against all the bacteria: MICs 0.34 μM for [BiPh(4‐MTT)₂{4‐MTT(H)}₂] against VRE, and 1.33 μM for [BiPh(1‐MMTZ)₂{1‐MMTZ(H)}₂] against M. smegmatis and S. aureus. Tris‐thiolato Bi^III complexes were least effective overall. All complexes showed little or no toxicity towards mammalian COS‐7 cells at 20 μg mL^?1.     

Intramolecular ester enolate-imine cyclization reactions for the asymmetric synthesis of polycyclic β-lactams and cyclic β-amino acid derivatives

Enolates of chiral N-(α-methyl-p-methoxybenzyl)-ω-imino-esters undergo intramolecular cyclization reactions to afford (syn)-aza-anions of β-amino esters in high dr that cyclize to afford N-(α-methyl-p-methoxybenzyl)-β-lactams that can be readily deprotected to afford their corresponding cyclic NH-β-lactams, β-amino esters, or β-amino acids.     

Supramolecular main-chain liquid crystalline polymers and networks with competitive hydrogen bonding: networks and linear polymers created from tris- and bis-functionalised pyridyl networking agents

A series of supramolecular polymers and networks with variable liquid crystalline characteristics have been created. These species are formed through the benzoic acid/pyridine hydrogen bonding of a flexible bis-acid and a mixture of a rigid bis-pyridyl and non-mesogenic tris- and bis-pyridyl molecules. The tris networked systems displayed liquid crystalline characteristics up to and including 31.0% netpoint inclusion. Above this concentration, only crystalline and melting behaviours were observed. The bis-containing polymer system displayed liquid crystalline characteristics up to and including 22.5% inclusion. The phenomenon observed in the tris system would seem to be linked to a statistical correlation of hydrogen bond acceptors and donors. The elimination of liquid crystallinity at lower concentrations of the bis-pyridyl dopant could be attributed to the lower melting nature of that species. Smectic phases were found in both series of complexes in loadings up to 10% of the non-liquid crystalline component. There was also no observed phase segregation of the species after multiple heat/cool cycles and extended periods of time in the isotropic state. This would indicate that the thermodynamically more stable mesogenic phase cannot out-compete the non-liquid crystalline network.     

A Synthetic Loop Replacement Peptide That Blocks Canonical NF‐κB Signaling

Aberrant canonical NF‐κB signaling is implicated in diseases from autoimmune disorders to cancer. A major therapeutic challenge is the need for selective inhibition of the canonical pathway without impacting the many non‐canonical NF‐κB functions. Here we show that a selective peptide‐based inhibitor of canonical NF‐κB signaling, in which a hydrogen bond in the NBD peptide is synthetically replaced by a non‐labile bond, shows an about 10‐fold increased potency relative to the original inhibitor. Not only is this molecule, NBD2, a powerful tool for dissection of canonical NF‐κB signaling in disease models and healthy tissues, the success of the synthetic loop replacement suggests that the general strategy could be useful for discovering modulators of the many protein–protein interactions mediated by such structures.     

(Noble Gas)n-NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations

An investigation of pulsed-laser-ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co-deposition with laser-ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo-dissociation product. A new band at 1933.4 cm⁻¹ in the region of the CN and CN⁺ gas-phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar)_nCN⁺, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN⁺ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm⁻¹. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm⁻¹. H¹³CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for ¹³CN⁺ itself in the gas phase and in the argon matrix. The CN⁺ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)₂⁺+CN→Ar+CN⁺→(Ar)_nCN⁺.     

Harnack inequalities for evolving hypersurfaces

This work was carried out while the author was supported by an Australian Postgraduate Research Award and an ANUTECH scholarship     

ChemInform Abstract: U and P4 Reaction Products: A Quantum Chemical and Matrix Isolation Spectroscopic Investigation.

Reactions of laser‐ablated U atoms with P₄ molecules in excess Ar or Ne during condensation at 5 K are monitored by FTIR spectroscopy.     

ChemInform Abstract: Matrix Infrared Spectra and Electronic Structure Calculations of the First Actinide Borylene: FB=ThF2.

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