Dynamic and fluorescent nanoscale phenanthroline/terpyridine zinc(II) ladders. Self-recognition in unlike ligand/like metal coordination scenarios

A new coordination kit, the HETTAP approach, is described, which allows one to prepare supramolecular heteroleptic metal phenanthroline/terpyridine racks and ladders in basically quantitative yield. Due to the dynamic nature of the nanoladder structures, a two-step double-transmetalation and scenarios with like metal/unlike ligand recognition were realized.     

Aqueous dispersions of polyurethane cationomers: a new approach for hydrophobic modification and crosslinking

Polyurethanes (PUs) containing tertiary nitrogen atoms were synthesised from poly (tetramethylene oxide) glycol, toluene diisocyanate and N-methyl diethanolamine. These polymers were converted into cationomers by quarternising with alkyl bromides of different chain lengths and then dispersed in water. Finally the cationic PU dispersions were further crosslinked with dibromo compounds of different spacer lengths. The effect of percent ionisation, percent crosslinking, chain length of the ioniser and crosslinker on particle size, viscosity and interfacial tension of the dispersions and on the thermal, mechanical and surface tension properties of the dispersion cast films were studied. The hydrophilicity of the polymer is more in the dispersed state than when cast as a film, which exhibited low critical surface tension values. With increase in chain length of the ioniser and the crosslinker, the hydrophobicity of the dispersion cast film increases without appreciable change in the hydrophilicity of the polymer in the dispersed phase, as can be seen from the interfacial tension and critical surface tension values.     

Effect of high pressure processing on textural and microbiological quality of pink perch (Nemipterus japonicus) sausage during chilled storage

The non-thermal high pressure (HP) processing was studied on fish sausage to enhance the quality during chilled storage. Pink perch (Nemipterus japonicus) sausages, packed in poly amide casing under vacuum were subjected to 400, 500 and 600?MPa pressures (dwell time: 10?min and ramp rate: 300?MPa/min) and compared with heat-set samples for physico-chemical and microbial quality parameters. Pressurized samples formed softer and glossier gels with a slight reduction in water-holding capacity. HP made the texture of sausage softer, cohesive and less chewy and gummier than heat-treated ones. Folding test seen higher acceptance values in samples treated at 500 and 600?MPa, during storage. Maximum log reduction in microbial count was observed in 600?MPa immediately, and significant difference in cooked and pressurized sausages was seen only up to 7th day. This revealed the potential application of HP in replacing conventional heat treatment for sausages preparation with enhanced shelf-life.     

Diphenic acid as a general conformational lock in the design of bihelical structures

The bihelical (figure of "infinity") topology was examined from vantages of design, crystal structures, chirality, circular dichroism (CD) studies and molecular-orbital calculations. The minimalistic design envisaged the sequential linking of cystine to the anchor diphenic acid, which proved to be a general conformational lock. The bihelical compound 4 was obtained in two steps from diphenic anhydride 1 and cystine di-OMe. The chirality of 4 arises largely from the L-cystine. The bihelical compound 5 obtained from D-cystine di-OMe was found, by X-ray crystallography, CD studies, and optical rotation, to be the perfect mirror image of 4 prepared from L-cystine. The crystal structure of prototype 8, prepared by protocols used for 4 from the achiral cystine analogue cystamine, had a "U"-shaped conformation held together by intramolecular hydrogen bonds. Analysis of 4 and 5 show that the pairs of nine-membered beta-turn-like constructs made compact through hydrogen bonding with DMSO hold the key for the bihelical conformation. Another factor is the need for the presence of a ligand at the Calpha position. The absence of this, as in 8, allows major flexibility in the torsional angles around this critical region, promoting flexible alternatives. The CD analysis of 4, confirmed to be bihelical by X-ray crystallography, showed a typical negative band at about 210 A attributed to the beta-turn-like motif, and in the positive-band region a peak at about 227 A, generally related to the twist of the biphenyl unit. The cystamine analogue 8, which showed a "U"-type structure, presented a CD spectrum with no typical features. The total energy, derived from theoretical calculations by using the X-ray structure data, support the bihelical structure for 4 and a "U"-shaped one for 8. The limited utility of such calculations was tested with composite 9. Composite 9, in which the anchor diphenic acid is linked to cystamine on the one hand and to cystine on the other, showed a CD spectrum similar to that of 4, and this coupled with molecular-orbital calculations, using data from 4 and 8, predict a bihelical structure for this compound.     

Synthesis and Antimicrobial Evaluation of New Monocyclic β‐Lactams

A simple, practical, and efficient approach to synthesize new series of 2‐(3‐(2,4‐dichlorophenoxy)‐2‐(4‐(dimethylamino)phenyl)‐4‐oxoazetidin‐1‐ylamino)‐N‐arylacetamide by Staudinger [2 + 2] cycloaddition reaction. The titled compounds were evaluated for their antibacterial and antifungal activity against eight microorganisms. All the newly synthesized compounds are characterized by IR, ¹H‐NMR, and mass spectroscopic data.     

Conformational analysis of cinnamanilides

The conformational analysis of cinnamanilides has been carried out using IR spectroscopy. All the anilides studied were found to exist as equilibrium mixtures ofs-cis ands-trans forms in benzene. Thes-cis form was predominant over thes-trans in all the anilides except in thep-nitro anilide in which thes-trans form was predominant. The relative stabilities of the conformers were found to depend upon the electrostatic repulsions between the anilide nitrogen and the β-carbon atom in thes-trans form and those between the π-electrons of the C=O and C=C bonds in thes-cis form.     

A Multicomponent,Catalyst‐free,One‐Pot Synthesis of Functionalized 1,4‐Dihydroquinolines and Their Antimicrobial Studies

An atom‐efficient, catalyst‐free, and environmentally friendly approach towards the synthesis of substituted 1,4‐dihydroquinolines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j ) through a one‐pot multicomponent reaction involving resorcinol, aromatic aldehyde, acetoacetanilide, and ammonium acetate has been developed. The reactions were carried out under both conventional and microwave irradiation conditions. In general, improvement in rate and yield were observed when reactions were carried out under microwave irradiation compared with classical conditions. Most of the new compounds possessed moderate to significant antibacterial and antifungal activities.     

Peroxide/Potassium Iodide Redox Systems for in situ Oxyiodination of Organic Compounds under Liquid‐Phase and Solvent‐Free Conditions

Iodination of certain aromatic amines and phenols are triggered by the oxidation of KI by peroxy compounds such as tert‐butyl hydroperoxide (^tBuOOH) under liquid‐phase and solvent‐free conditions by grinding the reactants in a mortar with a pestle. The reactions afforded corresponding iodo derivatives in good yield with high regioselectivity (Table 1).     

Adsorption of Nitrogen, Oxygen and Argon on Na-CeX Zeolites

Commercial type X zeolites (Linde 13X) are nitrogen selective. Oxygen is the less abundant component in air; hence oxygen selective sorbents are desired for air separation. Mixed Na-Ce type X zeolites containing different ratios of Ce³⁺/Na⁺ ions are prepared by partial ion exchange of commercial X zeolite. The adsorption isotherms of nitrogen, oxygen and argon are measured and the pure-component selectivity ratios are compared and analyzed against commercial zeolites (13X) for air separation. Oxygen selectivity over nitrogen (1.5) and argon (4.0) are seen for mixed Na-Ce type X zeolite (Si/Al = 1.25; Ce³⁺/Na⁺ < 4.0) from Henry's constant determined from low pressure adsorption measurements. The oxygen and nitrogen isotherms cross over for mixed Na-Ce type X zeolite (Si/Al = 1.25; Ce³⁺/Na⁺ < 4.0), and the pressure at which cross they over increases as Ce³⁺/Na⁺ approaches 1. The oxygen selectivity as claimed in the patent by N.V. Choudary, R.V. Jasra, and S.G.T. Bhat (US Patent no. 6,087,289, 2000) is seen only at very low pressures in the volumetric adsorption measurement and the hydrogen treatment of the Ce-exchanged samples have no effect on the adsorption characteristics.     

Synthesis and self-assembly of a rigid exotopic bisphenanthroline macrocycle: surface patterning and a supramolecular nanobasket

The synthesis and characterisation of a rigid nanoscale macrocycle with two exotopic phenanthroline binding sites is reported. Scanning tunnelling microscopy (STM) at the solid-liquid interface reveals the formation of highly ordered monolayers of macrocycles with dimensions that are in good agreement with the calculated structure. Using the HETPHEN concept several bisheteroleptic coordination complexes with other phenanthrolines and a nanoscale basket assembly were prepared in presence of copper(I) ions. NMR spectroscopy, mass spectrometric data and elemental analysis point to three distinct isomers of the basket assembly in solution. A silver basket was prepared and readily converted to its copper analogue. Electrospray ionisation (ESI)-MS and spectrophotometric investigations provided additional mechanistic insight into the assembly process. Hence, the exotopic bisphenanthroline macrocycle in combination with HETPHEN concept proves to be very effective in controlling the compositional aspects of multicomponent self-assembly.