@article { ISI:000273400300004, title = {Experimental and theoretical study on the remarkable influence of protecting groups on the selectivity of addition of amines to vinyl sulfone-modified hex-2-enopyranosides}, journal = {Journal of Organic Chemistry}, volume = {75}, number = {2}, year = {2010}, month = {JAN}, pages = {303-314}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Although phenylmethylene-protected vinyl sulfone-modified carbohydrate 2 alpha reacts with both primary and secondary amines in Michael fashion to afford aminated products, only primary amines react with the dibenzyl-protected 3 alpha, 6-O-trityl-protected 4 alpha, and unprotected 5 alpha, highlighting for the first time the remarkable influence of protecting, groups on the reaction patterns of vinyl sulfone-modified carbohydrates. The quantum chemical calculations suggest that the Michael addition of amines and proton transfer to vinyl sulfone-modified carbohydrates 2 alpha and 5 alpha are possible via relay process in a concerted mechanism. These calculations reveal that the addition of primary amines to vinyl sulfone-modified carbohydrate is preferential due to the low activation energy barriers, whereas the addition of secondary amines has relatively higher activation energy barriers. The theoretical conclusions are in line with the experimental observations.

}, issn = {0022-3263}, doi = {10.1021/jo902046g}, author = {Bhattacharya, Rahul and Kesharwani, Manoj K. and Manna, Chinmoy and Ganguly, Bishwajit and Suresh, Cheravakattu G. and Pathak, Tanmaya} } @article {42530, title = {Borazine as a sensor for fluoride ion: a computational and experimental study}, journal = {Tetrahedron Letters}, volume = {52}, year = {2011}, month = {MAY}, pages = {3636{\textendash}3639}, abstract = {

The computational and experimental studies have revealed that even simple molecule like borazine can act as a sensor for fluoride ions. This study further reported the various binding modes of analytes using quantum chemical calculations and the nature of such interactions have been examined using electron density surface analysis. Total charge transfer analysis (qCT) correlates well with the binding affinities of analytes with the borazine receptor.

}, doi = {10.1016/j.tetlet.2011.05.018}, author = {Kesharwani, Manoj K. and Suresh, Moorthy and Das, Amitava and Ganguly, Bishwajit} } @article {42523, title = {Folding and unfolding movements in a [2]pseudorotaxane}, journal = {Journal of Organic Chemistry}, volume = {76}, year = {2011}, month = {DEC}, pages = {138{\textendash}144}, abstract = {

A new dibenzo[24]crown-8 derivative (1) was synthesized and functionalized with aromatic moieties such as naphthalene and coumarin units. These two fluorophores are known to form an effective FRET (Forster resonance energy transfer) pair, and this formed the basis for the design of this host crown ether derivative. Results of the steady-state and time-resolved fluorescence studies confirmed the resonance energy transfer between the donor naphthalene moiety and acceptor coumarin fragment, while NMR spectra and computational studies support a folded conformation for the uncomplexed crown ether 1. This was found to form an inclusion complex, a [2]pseudorotaxane type with imidazolium ion derivatives as the guest molecules with varying alkyl chain lengths ([C4mim]+ or [C10mim]+). The host crown ether (1) tends to adopt an open conformation on formation of the interwoven inclusion complex (1{\textperiodcentered}[C4mim]+ or 1{\textperiodcentered}[C10mim]+). This change in conformation, from the folded to a open one, was predicted by computational as well as 1H NMR studies and was confirmed by single crystal X-ray structure for one (1{\textperiodcentered}[C4mim]+) of the two inclusion complexes. The increase in the effective distance between the naphthalene and coumarin moieties in the open conformation of these inclusion complexes was also supported by the decrease in the effective FRET process that was operational between naphthalene and coumarin moieties in the free molecule (1). Importantly, this inclusion complex formation was found to be reversible, and in the presence of a stronger base/polar solvent, such as triethyl amine/DMSO, the deprotonation/effective solvation of the cationic imidizolium ions ([C4mim]+ or [C10mim]+) resulted in decomplexation or dethreading with restoration of the original emission spectra for 1, which signifies the subsequent increase in the FRET process. Thus we could demonstrate that a molecular folding-unfolding type of movement in the crown ether derivative could be induced by chemical input as an imidazolium ion.

}, doi = {10.1021/jo101762k}, author = {Suresh, Moorthy and Mandal, Amal Kumar and Kesharwani, Manoj K. and Adarsh, N. N. and Ganguly, Bishwajit and Kanaparthi, Ravi Kumar and Samanta, Anunay and Das, Amitava} } @article {42536, title = {Receptor design and extraction of inorganic fluoride ion from aqueous medium}, journal = {Chemical Communications}, volume = {47}, year = {2011}, month = {MAY}, pages = {7398-7400}, abstract = {

A receptor with acidic methylene hydrogens is found to act as an efficient binding mode for F-. This reagent could as well be used for selective and quantitative extraction of F- from the aqueous solution of NaF and sea water.

}, doi = {10.1039/C1CC11458A}, author = {Das, Priyadip and Mandal, Amal Kumar and Kesharwani, Manoj K. and Suresh, Eringathodi and Ganguly, Bishwajit and Das, Amitava} } @article {42528, title = {ZnII-2,2?:6?,2?-terpyridine-based complex as fluorescent chemosensor for PPi, AMP and ADP}, journal = {Europian Journal of Inorganic Chemistry}, year = {2011}, month = {JUL}, pages = {3050{\textendash}3058}, abstract = {

A new ZnII{\textendash}2,2':6',2"-terpyridine complex, derivatized with a coumarin moiety (L1Zn), acts as a fluorescent chemosensor for different biologically important phosphates like PPi, AMP and ADP in mixed aqueous media. Depending on the proportion of the aqueous fraction present in the solvent mixture, L1Zn shows a preference for different phosphate moieties at physiological pH. In an aqueous acetonitrile (2:3, v/v) medium this reagent shows a preference for AMP as compared to ADP, ATP and PPi. The binding affinities of L1Zn with different phosphate ions and associated shifts in the electronic spectra were rationalized by DFT calculations. Such an example of a receptor that is selective for AMP under physiological conditions is rare in the literature.

}, doi = {10.1002/ejic.201100125}, author = {Das, Priyadip and Ghosh, Amrita and Kesharwani, Manoj K. and Ramu, Vadde and Ganguly, Bishwajit and Das, Amitava} } @article {42507, title = {Alternative approach: a highly selective dual responding fluoride sensor having active methylene group as binding site}, journal = {Org Biomol Chem.}, volume = {10}, year = {2012}, month = {JAN}, pages = {2263-2271}, abstract = {

A newly designed phosphonium derivative (L) having active methylene functionality, shows unusual preference towards F- over all other anions. The binding process through C{\textendash}H...F- hydrogen bond formation was probed by monitoring the changes in either electronic or luminescence spectra. Changes in both cases are significant enough to allow visual detection. The loss of molecular flexibility of L on forming L{\textperiodcentered}F- effectively interrupts the non-radiative deactivation pathway and accounts for the observed switch on fluorescence response. The results of the time-resolved emission studies for L and L{\textperiodcentered}F- using a time-correlated single photon counting technique further corroborate this presumption. The excellent preference of L towards F- is attributed to an efficient hydrogen bonding interaction between the strongly polarized methylene protons and F-, which delineates the subtle difference in the affinity among other competing anionic analytes like CN-, H2PO4-, CH3CO2-, etc. The relative affinities of various anions and the preferential binding of F- to reagent L are also rationalized using computational studies.

}, doi = {10.1039/C2OB06815J}, author = {Das, Priyadip and Kesharwani, Manoj K. and Mandal, Amal K. and Suresh, Eringathodi and Ganguly, Bishwajit and Das, Amitava} } @article {42504, title = {Ratiometric detection of Cr3+ and Hg2+ by a naphthalimide-rhodamine based fluorescent probe}, journal = {Inorganic Chemistry}, volume = {51}, year = {2012}, month = {JAN}, pages = {1769{\textendash}1777}, abstract = {

Newly synthesized rhodamine derivatives, L1 and L2, are found to bind specifically to Hg2+ or Cr3+ in presence of large excess of other competing ions with associated changes in their optical and fluorescence spectral behavior. These spectral changes are significant enough in the visible region of the spectrum and thus, allow the visual detection. For L1, the detection limit is even lower than the permissible [Cr3+] or [Hg2+] in drinking water as per standard U.S. EPA norms; while the receptor, L2 could be used as a ratiometric sensor for detection of Cr3+ and Hg2+ based on the resonance energy transfer (RET) process involving the donor naphthalimide and the acceptor Cr3+/Hg2+-bound xanthene fragment. Studies reveal that these two reagents could be used for recognition and sensing of Hg2+/Cr3+. Further, confocal laser microscopic studies confirmed that the reagent L2 could also be used as an imaging probe for detection of uptake of these ions in A431 cells.

}, doi = {10.1021/ic202073q}, author = {Mahato, Prasenjit and Saha, Sukdeb and Suresh, E. and Liddo, Rosa Di and Parnigotto, Pier Paolo and Conconi, Maria Teresa and Kesharwani, Manoj K. and Ganguly, Bishwajit and Das, Amitava} } @article { ISI:000330159500007, title = {Molecular interactions, proton exchange, and photoinduced processes prompted by an inclusion process and a [2]pseudorotaxane formation}, journal = {Journal of Organic Chemistry}, volume = {78}, number = {18}, year = {2013}, month = {AUG}, pages = {9004-9012}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Appropriate design of the host and guest components allows formation of a novel [2]pseudorotaxane complex with an interrupted photoinduced electron transfer (PET)-coupled fluorescence resonance energy transfer (FRET) response. This is the first example of an inclusion complex with NO6-based azacrown ether as the host unit (H). Different guest molecules (G1, G2, G3, and G4) with varying stopper size are used for the studies. Unlike G1, G2, and G3, G4 with a relatively bulkier stopper fails to form a [2]pseudorotaxane complex. Isothermal titration microcaloiimetry measurements reveal a systematic increase in the association constant for H.G1, H.G2, and H.G3 with a change in the stopper size. Thermodynamic data suggest that the formation of H.G1/H.G2/H.G3 is exclusively driven by a large positive entropic gain (T Delta S = 19.69/26.80/21.81 kJ.mol(-1)), while the enthalpy change is slightly negative for H.G1/H.G3 (-2.61/-1.97 kJ.mol(-1)) and slightly positive for H.G2 (Delta H = 5.98 kJ.mol(-1)). For these three inclusion complexes, an interrupted PET-coupled FRET response is observed with varying efficiency, which is attributed to the subtle differences in acidity of the NH2+ unit of the guest molecules and thus the proton exchange ability between the host and respective guest. This is substantiated by the results of the computational studies.

}, issn = {0022-3263}, doi = {10.1021/jo400752d}, author = {Mandal, Amal Kumar and Suresh, Moorthy and Kesharwani, Manoj K. and Gangopadhyay, Monalisa and Agrawal, Manoj and Boricha, Vinod P. and Ganguly, Bishwajit and Das, Amitava} } @article {42484, title = {Hydrogen bonding interaction between active methylene hydrogen atoms and an anion as a binding motif for anion recognition: experimental studies and theoretical rationalization}, journal = {Journal of Physical Chemistry A}, volume = {118}, year = {2014}, month = {MAR}, pages = {2656{\textendash}2666}, abstract = {

Two new reagents, having similar spatial arrangements for hydrogen atoms of the active methylene functionalities, were synthesized and interactions of such reagents with different anionic analytes were studied using electronic spectroscopy as well as by using 1H and 31P NMR spectroscopic methods. Experimental studies revealed that these two reagents showed preference for binding to F{\textendash} and OAc{\textendash}. Detailed theoretical studies along with the above-mentioned spectroscopic studies were carried out to understand the contribution of the positively charged phosphonium ion, along with methylene functionality, in achieving the observed preference of these two receptors for binding to F{\textendash} and OAc{\textendash}. Observed differences in the binding affinities of these two reagents toward fluoride and acetate ions also reflected the role of acidity of such methylene hydrogen atoms in controlling the efficiencies of the hydrogen bonding in anion{\textendash}Hmethylene interactions. Hydrogen bonding interactions at lower concentrations of these two anionic analytes and deprotonation equilibrium at higher concentration were observed with associated electronic spectral changes as well as visually detectable change in solution color, an observation that is generally common for other strong hydrogen bond donor functionalities like urea and thiourea. DFT calculations performed with the M06/6-31+G**//M05-2X/6-31G* level of theory showed that F{\textendash} binds more strongly than OAc{\textendash} with the reagent molecules. The deprotonation of methylene hydrogen atom of receptors with F{\textendash} ion was observed computationally. The metal complex as reagent showed even stronger binding energies with these analytes, which corroborated the experimental results.

}, doi = {10.1021/jp501769y}, author = {Agarwalla, Hridesh and Jana, Kalyanashis and Maity, Arunava and Kesharwani, Manoj K. and Ganguly, Bishwajit and Das, Amitava} }