Electronically varied manganese tris-arylacetamide tripodal complexes

Abstract

This report details the synthesis and characterization of six new Mn(II) complexes coordinated to systematically varied 2,2',2''-nitrilotris(N-arylacetamidate) ligands (L^R; R?=?NO₂, Cl, Br, H, Me, and OMe). The complexes are synthesized as the di-tetramethylammonium salts [Me₄N]₂[MnL^R(OAc)]. The nitro variant Mn^NO2 afforded crystals suitable for X-ray diffraction and its molecular structure is reported. We previously reported the crystal structures of Fe^NO2 and Zn^NO2 and additionally report herein the synthesis and characterization of Co^NO2. Using these four molecules, we conduct a brief comparison of the bond metrics to demonstrate that the primary difference governing structural changes is likely due to ionic crystal radii changes rather than electronic properties. The electrochemical properties of the Mn^R complexes were additionally explored with cyclic voltammetry, which revealed that the series is modulated by the various electronic substituents on the aryl groups of the ligands. The electrochemical studies also revealed, consistent with our previous report, that the acetate ligand on the Mn^R complexes is labile. Finally, a Hammett plot was constructed using the potentials obtained from cyclic voltammetry, which is compared with a few other similar transition metal complexes.     

Facile synthesis of unusual glycosyl carbamates and amino acid glycosides from propargyl 1,2-orthoesters as glycosyl donors

Propargyl 1,2-O-orthoesters are exploited for the synthesis of 1,2-trans O-glycosides of protected amino acids. N-Fmoc- and N-Cbz protected serine/threonine - benzyl/methyl esters reacted well with glucosyl-, galactosyl-, mannosyl- and lactosyl- derived propargyl 1,2-orthoesters affording respective 1,2-trans glycosides in good yields under AuBr(3)/4 ? MS Powder/CH(2)Cl(2)/rt. t-Boc serine derivative gave serine 1,2-orthoester and glycosyl carbamate. Optimized conditions enabled preparation of new glycosyl carbamates from N-Boc protected amines in a single step using gold catalysts and propargyl 1,2-orthoesters in excellent yields.     

Conducting LB films based on metal complexes of sulphur donor ligands

Preliminary studies are reported on the film forming characteristics of compounds such as dialkyldimethylammonium-M (dmit)₂ and dialkyldimethylammonium-M (mnt)₂ where M = Ni, Pt or Pd. All materials investigated show good monolayer behaviour and deposit readily onto evaporated aluminium or gold films. This is confirmed by surface potential and FTIR measurements. The lateral conductivity of deposited films increases by many orders of magnitude when exposed to bromine vapour.     

Benzyne cyclisation with carbanion activated aromatic rings1

Attempts to cyclise o-chlorophenyl benzyl ether, sulphide, sulphoxide and sulphone by treatment with KNH₂/NH₃ were unsuccessful. Similar reaction of 1-(o-chlorophenyl)-2,2-diphenylethane led to amination whereas α-(o-chlorobenzyl)phenylacetic acid gave a dihydrocoumarin. Reaction of 4- and 2-(o-chlorophenethyl)-pyridines, however, afforded products comprising benzisoquinolines and 1-pyridylbenzocyclobutenes.     

Localized vibrations of H−Na+H− impurity in KCl crystal

Localized modes due to H^?Na⁺H^? complex impurity in KCl crystal have been computed by a Green function method and compared with experimental data.     

A highly selective chemodosimeter for the rapid detection of Hg2+ ions in aqueous media

A novel S,S′-diallyl carbohydrazonodithioate derivative 3 of rhodamine B hydrazone was developed as a chemodosimeter for selective detection of mercury ions based on Hg²⁺ promoted cyclization. The allyl groups of 3 play a key role in the binding and selection of Hg²⁺ ions. The probe responds selectively to Hg²⁺ over various other competitive cations with marked chromo- and fluorogenic changes. The formation of stable oxadiazole derivative 8 was a strong driving force for this high selectivity. Practically, this probe is more promising because of the remarkable high selectivity, faster response, low detection limit, and aqueous solubility of 3.     

Shape-controlled synthesis of semiconducting CuFeS2 nanocrystals

Nanocrystals of the semiconducting chalcopyrite CuFeS₂ have been synthesized utilizing a facile solution-based method. Depending on the choice of precursors and synthesis conditions, the nanocrystals exhibit either a spherical (～12 nm) or pyramidal morphology (～30 nm), with a narrow size distribution. The band gap of the pyramidal nanocrystals is very close to the bulk value, but a larger band gap is obtained for the spherical nanocrystals likely because of size confinement effect.