01787nas a2200205   4500008004100000022001400041245012000055210006900175260000900244300001600253490000800269520105100277100001901328700002701347700001701374700001601391700003001407700001701437856012701454       2016                        eng d  a0002-786300aCounteranion driven homochiral assembly of a cationic C-3-symmetric gelator through ion-pair assisted hydrogen bond0 aCounteranion driven homochiral assembly of a cationic C3symmetri  cSEP   a11113-111160 v1383 a<p>The helical handedness in achiral self-assemblies is mostly complex due to spontaneous symmetry breaking or kinetically controlled random assembly formation. Here an attempt has been made to address this issue through chiral anion exchange. A new class of cationic achiral C-3-symmetric gelator devoid of any conventional gelation assisting functional units is found to form both right-and left-handed helical structures. A chiral counteranion exchange-assisted approach is successfully introduced to control the chirality sign and thereby to obtain preferred homochiral assemblies. Formation of anion-assisted chiral assembly was confirmed by circular dichroism (CD) spectroscopy, microscopic images, and crystal structure. The X-ray crystal structure reveals the construction of helical assemblies with opposite handedness for (+)- and (-)-chiral anion reformed gelators. The appropriate counteranion driven ion-pair-assisted hydrogen-bonding interactions are found responsible for the helical bias control in this C-3-symmetric gelator.</p>1 aMaity, Arunava1 aGangopadhyay, Monalisa1 aBasu, Arghya1 aAute, Sunil1 aBabu, Sukumaran, Santhosh1 aDas, Amitava  uhttps://library.ncl.res.in/content/counteranion-driven-homochiral-assembly-cationic-c-3-symmetric-gelator-through-ion-pair02566nas a2200193   4500008004100000245013000041210006900171260000800240300001600248490000700264520184300271100002702114700001902141700001602160700002402176700002602200700001702226856012902243       2017                        eng d00aChiral discrimination through h-1 nmr and luminescence spectroscopy: dynamic processes and solid strip for chiral recognition0 aChiral discrimination through h1 nmr and luminescence spectrosco  cDEC  a18303-183130 v233 aThe appropriate choice of the host molecules with well-defined optical activity (S-H/R-H) helps in the differentiation between two secondary ammonium ion-derivative guest molecules with different optical activities (R-G/S-G) based on the fluorescence resonance energy transfer (FRET)based luminescence responses. Crown ether-based host molecules with opposite chiral configurations (R-H, S-H) have been derived from 1,1'-bi-2-naphthol (BINOL) derivatives that have axially chiral biaryl centers. These chiral crown ethers form host-guest complexes (i.e., [2] pseudoro-taxanes) with chiral secondary ammonium ion derivatives (R-G, S-G). NMR spectroscopic studies show that the complexes are in a dynamic equilibrium in solution. Results of the H-1 NMR and fluorescence spectroscopic studies indicate a head-on orientation of the host and guest in the [2] pseudorotaxanes. The difference in the efficiency in the FRET-based responses between anthracene and the BINOL derivatives allow efficient chiral discrimination of the guests. Isothermal titration calorimetry and NMR investigations reveal that inclusion complexes between hosts and guests of the same chirality (R-H center dot R-G, S-H center dot S-G) are more stable relative to those of opposite chirality (R-H center dot S-G, S-H center dot R-G). However, FRET-based energy-transfer efficiency is higher for R-H center dot S-G and S-H center dot R-G complexes. NMR spectroscopic studies show that the relative orientation of the guest in the host cavity is significantly different when the host binds a guest of the same or opposite chirality; furthermore, the latter is more favorable for FRET, thus enabling discrimination between enantiomers. Interestingly, chiral discrimination of guest ions could also be achieved by using silica surfaces modified with chiral host molecules.1 aGangopadhyay, Monalisa1 aMaity, Arunava1 aDey, Ananta1 aRajamohanan, P., R.1 aRavindranathan, Sapna1 aDas, Amitava  uhttps://library.ncl.res.in/content/chiral-discrimination-through-h-1-nmr-and-luminescence-spectroscopy-dynamic-processes-and01921nas a2200193   4500008004100000245008100041210006900122260000800191300001600199490000700215520124900222100002101471700001901492700002701511700002601538700003501564700001701599856011101616       2017                        eng d00aCucurbit[7]uril induced formation of fret-enabled unilamellar lipid vesicles0 aCucurbit7uril induced formation of fretenabled unilamellar lipid  cOCT  a10989-109990 v333 aA unique fluorescence resonance energy transfer (FRET) process is found to be operational in a unilamellar lipid self-assembly in the aqueous phase. A newly synthesized naphthyl based long chain lipid derivative [N-(naphthalene-1-ylmethyl)tetradecane-1-ammonium chloride, 14NA(+)] forms various self-assembled architectures in the aqueous phase. Controlled changes in lipid concentration lead to a transition of the self-assemblies from micelles to vesicles to rods. In the presence of cucurbit[7]uril (CB7), 14NA(+) forms a host-guest [2]pseudorotaxane complex (CB7(sic)14NA(+)) and secondary interactions lead to the formation of a lipid bilayer with hydrophobic pockets situated in between the layers. The change in the structure of 14NA(+) assemblies, interaction with CB7 and formation of supramolecular assemblies of CB7(sic)14NA(+) were examined using light scattering, spectroscopic, and microscopic techniques. Entrapment of a luminescent dye, anthracene within the hydrophobic bilayer of the supramolecular assembly CB7(sic)14NA(+) favors a modified luminescent response due to an efficient FRET process. Further, the FRET process could be controlled by thermal and chemical stimuli that induce transformation of unilamellar vesicles.1 aKushwaha, Shilpi1 aMaity, Arunava1 aGangopadhyay, Monalisa1 aRavindranathan, Sapna1 aRajamohanan, Pattuparambil, R.1 aDas, Amitava  uhttps://library.ncl.res.in/content/cucurbit7uril-induced-formation-fret-enabled-unilamellar-lipid-vesicles