In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photo...In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photoresponsive beha-vior of the green, environment friendly product was investigated. The end hydroxyl group of lignin was modified with the chromophoric systems by DCC coupling. The chromophoric systems as well as the chromophore-bound biopolymer core systems were purified by column chromatography. The products were characterized by UV-visible, fluorescence, FT-IR and NMR spectroscopic methods. The results of the studies show that incorporation of the chromophoric system on to the lignin core enhanced the light absorption, emission and light stabilization properties of the chromophoric system. The light fastening properties of chromophoric system and the modified product were compared. It shows that stability of the chromophoric system greatly enhanced on attaching to the polymeric system. The trans-cis photoisomerisation and the reverse cis-trans thermal conversions were also assisted by the lignin core. The remarkable stability on irradiation shows that this is a novel photoresponsive system with excellent light fastening properties which would find application in coating materials, dyes, paints, inks, therapeutic agents and many more.展开更多
The cis→trans isomerisation of homologous 2-hydroxycycloalkanecarboxylic acids in strongly basic aqueous solution was studied starting from the cis isomers. It was found that the cyclopentane, cyclohexane and cyclohe...The cis→trans isomerisation of homologous 2-hydroxycycloalkanecarboxylic acids in strongly basic aqueous solution was studied starting from the cis isomers. It was found that the cyclopentane, cyclohexane and cycloheptane homologues afforded synthetically useful amounts of the trans acids and the procedure resulted in relatively small quantities of the corresponding olefinic acids. In contrast, the isomerisation of the cis-2-hydroxycyclooctanecarboxylic acid produced roughly equal amounts of the cis and trans isomers and the 1-cyclooctenecarboxylic acid at equilibrium. Molecular modelling with the PM3 semiempirical method of the reactants, products and the intermediates applying explicit water molecules as reaction medium gave a fair estimate for the rate sequence of the idealised （dehydration-free） isomerisation reactions in aqueous base solution.展开更多
Chemosensors are prepared through condensation reactions between polymeric amines and three different aldehydes;the activities of the three products were evaluated in DMF-H_(2)O(7:3,v/v)solvent system.Chemosensor 2c d...Chemosensors are prepared through condensation reactions between polymeric amines and three different aldehydes;the activities of the three products were evaluated in DMF-H_(2)O(7:3,v/v)solvent system.Chemosensor 2c demonstrated selectivity for Zn^(2+)enhancement of the fluorescence intensity at 420 nm.Upon binding of 2c with Zn^(2+),an approximately 9 fold enhancement in fluorescence intensity was observed due to the combined effect of ESIPT,CvN isomerisation and the two-channel quenching of PET.The investigation of the photophysical properties of 2c revealed that the sensor at low pH led to a shift in the emission profile because of the presence of two types of nitrogen i.e.sp^(2) and sp^(3) nitrogens and the pH dependent fluorescence profile is due to the protonation at sp^(3) hybridised nitrogen that influences the charge transfer transitions of 2c.However,the salt effect has not much influence on the photophysical properties of 2c;and 2c was found to form organic nano-particles(ONP)in a DMF-H_(2)O(1:99,v/v)solvent system and this material was found to detect a minimum of 40 nM concentration of Zn^(2+).The receptor 2c was found to be biocompatible through MTT assay and potent to detect Zn^(2+)in real biological conditions of microbial cells.The compounds 2a,2b and 2c while immobilized in PVC based membrane,exhibited their selectivity for zinc ions as ion selective electrodes.These electrodes responded linearly in a wide concentration range with a lower detection limit of 10μM.The electrodes have been successfully used as indicator electrodes in potentiometric titration of zinc ions with EDTA.展开更多
文摘In the present study, a photoresponsive chromophoric system such as 4-[(E)-2-(3-hydro xynaphthalen-2-yl)diazen-1-yl] benzoic acid was incorporated on to lignin core by functional transformation reactions and the photoresponsive beha-vior of the green, environment friendly product was investigated. The end hydroxyl group of lignin was modified with the chromophoric systems by DCC coupling. The chromophoric systems as well as the chromophore-bound biopolymer core systems were purified by column chromatography. The products were characterized by UV-visible, fluorescence, FT-IR and NMR spectroscopic methods. The results of the studies show that incorporation of the chromophoric system on to the lignin core enhanced the light absorption, emission and light stabilization properties of the chromophoric system. The light fastening properties of chromophoric system and the modified product were compared. It shows that stability of the chromophoric system greatly enhanced on attaching to the polymeric system. The trans-cis photoisomerisation and the reverse cis-trans thermal conversions were also assisted by the lignin core. The remarkable stability on irradiation shows that this is a novel photoresponsive system with excellent light fastening properties which would find application in coating materials, dyes, paints, inks, therapeutic agents and many more.
文摘The cis→trans isomerisation of homologous 2-hydroxycycloalkanecarboxylic acids in strongly basic aqueous solution was studied starting from the cis isomers. It was found that the cyclopentane, cyclohexane and cycloheptane homologues afforded synthetically useful amounts of the trans acids and the procedure resulted in relatively small quantities of the corresponding olefinic acids. In contrast, the isomerisation of the cis-2-hydroxycyclooctanecarboxylic acid produced roughly equal amounts of the cis and trans isomers and the 1-cyclooctenecarboxylic acid at equilibrium. Molecular modelling with the PM3 semiempirical method of the reactants, products and the intermediates applying explicit water molecules as reaction medium gave a fair estimate for the rate sequence of the idealised （dehydration-free） isomerisation reactions in aqueous base solution.
基金supported with research grant(SR/FT/CS-97/2010(G)from Department of Science and Technology(DST),Government of India.
文摘Chemosensors are prepared through condensation reactions between polymeric amines and three different aldehydes;the activities of the three products were evaluated in DMF-H_(2)O(7:3,v/v)solvent system.Chemosensor 2c demonstrated selectivity for Zn^(2+)enhancement of the fluorescence intensity at 420 nm.Upon binding of 2c with Zn^(2+),an approximately 9 fold enhancement in fluorescence intensity was observed due to the combined effect of ESIPT,CvN isomerisation and the two-channel quenching of PET.The investigation of the photophysical properties of 2c revealed that the sensor at low pH led to a shift in the emission profile because of the presence of two types of nitrogen i.e.sp^(2) and sp^(3) nitrogens and the pH dependent fluorescence profile is due to the protonation at sp^(3) hybridised nitrogen that influences the charge transfer transitions of 2c.However,the salt effect has not much influence on the photophysical properties of 2c;and 2c was found to form organic nano-particles(ONP)in a DMF-H_(2)O(1:99,v/v)solvent system and this material was found to detect a minimum of 40 nM concentration of Zn^(2+).The receptor 2c was found to be biocompatible through MTT assay and potent to detect Zn^(2+)in real biological conditions of microbial cells.The compounds 2a,2b and 2c while immobilized in PVC based membrane,exhibited their selectivity for zinc ions as ion selective electrodes.These electrodes responded linearly in a wide concentration range with a lower detection limit of 10μM.The electrodes have been successfully used as indicator electrodes in potentiometric titration of zinc ions with EDTA.
