02972nas a2200253   4500008004100000022001400041245012000055210006900175260011000244300001400354490000600368520200200374100001602376700002202392700001802414700002102432700002202453700002002475700002002495700002102515700003202536700002202568856012802590       2012                        eng d  a1744-683X00aCompetition between gelation and crystallisation of a peculiar multicomponent liquid system based on ammonium salts0 aCompetition between gelation and crystallisation of a peculiar m  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a3446-34560 v83 a<p>An exemplar competition between gelation and crystallisation phenomena was examined with an unusual synergistic multicomponent (organo) gelator solution (MGS), which consists of a well-defined methanolic solution of (1R, 2R)-1,2-diaminocyclohexane L-tartrate containing 2.4 equiv. of concentrated hydrochloric acid. The optimal composition of the MGS was determined through meticulous solubility, gelation and structural studies, which support a transient gelation mechanism based on the kinetic self-assembly of the tartrate salt driven by hydrogen-bonding interactions, involving ammonium nitrogen donors and hydroxyl oxygen acceptors, and electrostatic interactions. The hydrochloric acid is involved in the solubilisation of the salt through an ionic dissociation-exchange process, which ends up with the formation-precipitation of (1R, 2R)-1,2-diaminocyclohexane dihydrochloride. As a consequence, an irreversible destruction of the gel takes place, which indicates the metastable nature of this phase that cannot be accessed from the thermodynamically equilibrated state. Gelation of a variety of oxygenated and nitrogenated solvents with moderate polarity occurred efficiently using extremely low MGS concentrations at low temperatures, and the gel phase was confirmed by dynamic rheological measurements. Several features make the described MGS unique: (1) it is a multicomponent solution where each component and its stoichiometry play a key role in the reproducible formation and stabilization of the gels; (2) it is formed by simple, small, and commercially available chiral building blocks (dissolved in a well-defined solvent system), which are easily amenable for further modifications; (3) the gelation phenomenon takes place efficiently at low temperature upon warming up the isotropic solution, conversely to the typical gel preparation protocol; and (4) the formed organogels are not thermoreversible despite the non-covalent interactions that characterize the 3D-network.</p>1 aKapoor, Iti1 aSchoen, Eva-Maria1 aBachl, Jurgen1 aKuehbeck, Dennis1 aCativiela, Carlos1 aSaha, Subhadeep1 aBanerjee, Rahul1 aRoelens, Stefano1 aMarrero-Tellado, Jose, Juan1 aDiaz, David, Diaz  uhttps://library.ncl.res.in/content/competition-between-gelation-and-crystallisation-peculiar-multicomponent-liquid-system-002716nas a2200217   4500008004100000022001400041245014200055210006900197260011000266300001400376490000600390520182000396100001802216700002602234700002402260700002202284700001702306700002102323700002202344856013202366       2013                        eng d  a2050-748800aOrganophotocatalysis in nanostructured soft gel materials as tunable reaction vessels: comparison with homogeneous and micellar solutions0 aOrganophotocatalysis in nanostructured soft gel materials as tun  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a4577-45880 v13 a<p>Riboflavin tetraacetate-catalyzed aerobic photooxidation of 1-(4-methoxyphenyl)ethanol was investigated as a model reaction under blue visible light in different soft gel materials, aiming to establish their potential as reaction vessels for photochemical transformations. Three strategies involving different degrees of organization of the catalyst within the gel network were explored, and the results compared to those obtained in homogeneous and micellar solutions. In general, physical entrapment of both the catalyst and the substrate under optimized concentrations into several hydrogel matrices (including low-molecular-weight and biopolymer-based gels) allowed the photooxidation with conversions between 55 and 100% within 120 min (TOF similar to 0.045-0.08 min(-1); k(obs) similar to 0.011-0.028 min(-1)), albeit with first-order rates ca. 1-3-fold lower than in solution under comparable non-stirred conditions. Remarkably, the organogel made of a cyclohexane-based bisamide gelator in CH3CN not only prevented the photodegradation of the catalyst but also afforded full conversion in less than 60 min (TOF similar to 0.167 min(-1); k(obs) similar to 0.073 min(-1)) without the need of additional proton transfer mediators (e. g., thiourea) as it occurs in CH3CN solutions. In general, the gelators could be recycled without detriment to their gelation ability and reaction rates. Moreover, kinetics could be fine-tuned according to the characteristics of the gel media. For instance, entangled fibrillar networks with relatively high mechanical strength were usually associated with lower reaction rates, whereas wrinkled laminated morphologies seemed to favor the reaction. In addition, the kinetics results showed in most cases a good correlation with the aeration efficiency of the gel media.</p>1 aBachl, Jurgen1 aHohenleutner, Andreas1 aDhar, Basab, Bijayi1 aCativiela, Carlos1 aMaitra, Uday1 aKoenig, Burkhard1 aDiaz, David, Diaz  uhttps://library.ncl.res.in/content/organophotocatalysis-nanostructured-soft-gel-materials-tunable-reaction-vessels-comparison-001084nas a2200193   4500008004100000022001400041245012600055210006900181260011000250300001400360490000700374520028500381100002000666700001800686700001700704700002200721700002000743856012700763       2014                        eng d  a1359-734500aAmino acid-based multiresponsive low-molecular weight metallohydrogels with load-bearing and rapid self-healing abilities0 aAmino acidbased multiresponsive lowmolecular weight metallohydro  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a3004-30060 v503 a<p>A multiresponsive metallohydrogel based on an amino acid-derived low molecular weight (LMW) ligand and a Zn(II) salt was prepared. This hydrogel showed remarkable shape-persistent, self-standing, load-bearing and self-healing properties, which is uncommon in LMW hydrogels.</p>1 aSaha, Subhadeep1 aBachl, Jurgen1 aKundu, Tanay1 aDiaz, David, Diaz1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/amino-acid-based-multiresponsive-low-molecular-weight-metallohydrogels-load-bearing-and01213nas a2200193   4500008004100000022001400041245011700055210006900172260011000241300001400351490000700365520041900372100002000791700001800811700001700829700002200846700002000868856013100888       2014                        eng d  a1359-734500aDissolvable metallohydrogels for controlled release: evidence of a kinetic supramolecular gel phase intermediate0 aDissolvable metallohydrogels for controlled release evidence of   aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAY  a7032-70350 v503 a<p>Two metallohydrogels based on an amino acid-based ligand and Zn(II) salts were synthesized. These hydrogels show an uncommon, reversible, time-dependent transformation from the opaque to transparent state. These hydrogels also exhibit gradual dissolution in water (pH &lt;= 7) over time. A water-soluble stimulant, caffeine, could be in situ loaded into the hydrogels and slowly released during dissolution.</p>1 aSaha, Subhadeep1 aBachl, Jurgen1 aKundu, Tanay1 aDiaz, David, Diaz1 aBanerjee, Rahul  uhttps://library.ncl.res.in/content/dissolvable-metallohydrogels-controlled-release-evidence-kinetic-supramolecular-gel-phase-0