@article {42532, title = {Comparative study of porphyrin derivatives in monolayers at the air-water interface and in langmuir-blodgett films}, journal = {Thin Solid Films}, volume = {519}, year = {2011}, month = {MAR}, pages = {8066{\textendash}8073}, abstract = {

The orientation and aggregation of various porphyrin derivatives at the air{\textendash}water interface and in Langmuir{\textendash}Blodgett films were investigated. Monolayer properties of these molecules, where long alkyl chain(s) were covalently bound through different functionality of varying hydrophilicity were studied by measuring surface pressure area isotherms. Such derivatives, where ether functionality (functionalities) was (were) used for linking long alkyl chain(s), did not form uniform monolayer; instead they were found to form multilayer clusters or aggregates on the water surface. On the other hand, porphyrin derivative functionalized at the four peripheral phenyl rings with eight hexadecyl ether chains formed stable spherical vesicles when deposited on mica. Tetra N-alkyl pyridinium porphyrins with long alkyl chain were found to form various phases on the water surface. Evidence of transition from horizontal orientation to vertical orientation of porphyrin rings of porphyrin molecules having C14 chains was observed. This type of transition was lost with the porphyrin molecule with a relatively smaller chain (C8).

}, doi = {10.1016/j.tsf.2011.02.082}, author = {Ghosh, Amrita and Mahato, Prasenjit and Choudhury, Sipra and Das, Amitava} } @article {42542, title = {Solvent-dependent aggregation behavior of a new Ru(ii)-polypyridyl based metallosurfactant}, journal = {Chemical Communications}, volume = {47}, year = {2011}, month = {SEP}, pages = {11074-11076}, abstract = {

Variation of the solvent polarity leads to the formation of vesicles and reverse vesicles of a newly synthesized amphiphilic Ru(II)-polypyridyl complex.

}, doi = {10.1039/C1CC13957F}, author = {Mahato, Prasenjit and Saha, Sukdeb and Choudhury, Sipra and Das, Amitava} } @article {42522, title = {Urea/thiourea derivatives and Zn(II)-DPA complex as receptors for anionic recognition-a brief account}, journal = {Journal of Chemical Sciences}, volume = {123}, year = {2011}, month = {OCT}, pages = {175{\textendash}186}, abstract = {

This review covers few examples of anion complexation chemistry, with a special focus on urea/thiourea-based receptors and Zn(II)-dipicolyl amine-based receptors. This article specially focuses on structural aspects of the receptors and the anions for obtaining the desire specificity along with an efficient receptor{\textendash}anion interaction. Two types of receptors have been described in this brief account; first one being the strong hydrogen bond donor urea/thiourea derivatives, which binds the anionic analytes through hydrogen bonded interactions; while, the second type of receptors are coordination complexes, where the coordination of the anion to the metal centre. In both the cases the anion binding modulate the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and thereby the spectroscopic response. Appropriate choice of the signalling unit may allow probing the anion binding phenomena through visual detection.

}, doi = {10.1007/s12039-011-0151-y}, author = {Das, Priyadip and Mahato, Prasenjit and Ghosh, Amrita and Mandal, Amal Kumar and Banerjee, Tanmay and Saha, Sukdeb and Das, Amitava} } @article {42525, title = {Zn(II)-cyclam based chromogenic sensors for recognition of atp in aqueous solution under physiological conditions and their application as viable staining agents for microorganism}, journal = {Inorganic Chemistry}, volume = {50}, year = {2011}, month = {MAR}, pages = {4162{\textendash}4170}, abstract = {

Two chromogenic complexes, L.Zn (where L is (E)-4-((4-(1,4,8,11-tetraazacyclotetradecan-1-ylsulfonyl)phenyl)diazenyl)-N,N-dimethylaniline) and its [2]pseudorotaxane form (α-CD.L.Zn), were found to bind preferentially to adenosine triphosphate (ATP), among all other common anions and biologically important phosphate (AMP, ADP, pyrophosphate, and phosphate) ions in aqueous HEPES buffer medium of pH 7.2. Studies with live cell cultures of prokaryotic microbes revealed that binding of these two reagents to intercellular ATP, produced in situ, could be used in delineating the Gram-positive and the Gram-negative bacteria. More importantly, these dyes were found to be nontoxic to living microbes (eukaryotes and prokaryotes) and could be used for studying the cell growth dynamics. Binding to these two viable staining agents to intercellular ATP was also confirmed by spectroscopic studies on cell growth in the presence of different respiratory inhibitors that influence the intercellular ATP generation.

}, doi = {10.1021/ic200223g}, author = {Mahato, Prasenjit and Ghosh, Amrita and Mishra, Sanjiv K. and Shrivastav, Anupama and Mishra, Sandhya and Das, Amitava} } @article {42519, title = {Interfacial and film formation behavior of photoactive Ru(ii)bipyridyl based metallosurfactants and a rare example of a monolayer based logic gate approach}, journal = {Chempluschem}, volume = {77}, year = {2012}, month = {DEC}, pages = {1096{\textendash}1105}, abstract = {

Three derivatives of tris(bipyridyl){\textendash}ruthenium(II) complexes with different alkyl-chain lengths (nC18H37 (1), nC14H29 (2) and nC10H21 (3)) were synthesised. All these complexes behaved as an amphiphile and their surface properties were studied at the air{\textendash}water interface by measuring surface pressure{\textendash}area (Π{\textendash}A) isotherms. The surface morphology of the resulting films at the air{\textendash}water interface was also studied by using Brewster angle microscopy. Mean molecular areas of these complexes were measured from the Π{\textendash}A isotherms, which were approximately 200 {\r A}2, thereby indicating a parallel arrangement of the Ru{\textendash}bipyridyl moiety of the complexes. Mono- and multilayer Langmuir{\textendash}Blodgett (LB) films were formed on different solid surfaces with transfer ratios close to one. Similarities in the absorption and fluorescence spectra of these amphiphiles in solution as well as in LB films deposited on a quartz surface confirmed the successful transfer of these films onto the substrates. The latter provided information about the arrangements of metallosurfactant molecules within the LB films. The two-dimensional concentrations of these films were calculated from the Lambert{\textendash}Beer law as well as from the Π{\textendash}A isotherm, which confirmed regular and reproducible transfer of the complex monolayers from the air{\textendash}water interface onto the quartz surface. The surface morphology of these films on various substrates was characterised by atomic force microscopy. Furthermore, by oxidising the monolayer of complex 3, a one-input sequential logic gate was constructed.

}, doi = {10.1002/cplu.201200207}, author = {Mahato, Prasenjit and Saha, Sukdeb and Choudhury, Sipra and Das, Amitava} } @article {42499, title = {Interrupted PET coupled TBET process for the design of a specific receptor for Hg2+ and its intracellular detection in MCF7 cells}, journal = {Chemical Communications}, volume = {48}, year = {2012}, month = {JUL}, pages = {9293-9295}, abstract = {

A new coumarin{\textendash}rhodamine conjugate constitutes a unique example of the interrupted PET coupled TBET response for developing an imaging reagent for determining the intracellular distribution of Hg2+ in MCF7 cells exposed to [Hg2+] as low as 2 ppb.

}, doi = {10.1039/C2CC34490D}, author = {Saha, Sukdeb and Mahato, Prasenjit and Baidya, Mithu and Ghosh, Sudip K. and Das, Amitava} } @article {42511, title = {Rare example of TICT based optical responses for the specific recognition of Cr3+ by a 2,2?:6?,2?-terpyridine derivative and demonstration of multiple logic operations}, journal = {Journal of Physical Chemistry C}, volume = {116}, year = {2012}, month = {JUL}, pages = {17448{\textendash}17457}, abstract = {

Chemosensor L showed a nonlinear fluorescence response on specific binding to Cr3+ ion in the presence of various alkali, alkaline-earth, transition, and lanthanide metal ions. A luminescence band with maxima at 512 nm for L was observed (λext = 330 nm) for a twisted intramolecular charge transfer (TICT) transition following antienergy gap law behavior. However, normal energy gap law behavior prevailed on formation of a new nonluminescent charge transfer complex, Mn+{\textperiodcentered}L. For paramagnetic metal ions, paramagnetism induced luminescence quenching could have also contributed to this. A new switched on fluorescence response at λems of 356 nm (λext of 330 nm) was observed due to Franck{\textendash}Condon charge transfer (FC-CT) transition only on the formation of a complex, (Cr3+)2{\textperiodcentered}L. Spectral studies revealed a unique dynamic coordination behavior and migration of Cr3+ from the terpyridyl fragment to the NNMe2 center of L as a function of the varying concentration of another ion (Zn2+) and the subtle difference in the binding affinities of the terpyridyl moiety toward Cr3+ and Zn2+. Further, spectral responses of L toward Zn2+, different concentration of Cr3+, H+ and on subsequent addition of F{\textendash} as different ionic inputs could be correlated well for demonstrating various basic and combinatorial circuits.

}, doi = {10.1021/jp305780y}, author = {Mahato, Prasenjit and Saha, Sukdeb 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 {42501, title = {Recognition of Hg 2+ and Cr 3+ in physiological conditions by a rhodamine derivative and its application as a reagent for cell-imaging studies}, journal = {Inorganic Chemistry}, volume = {51}, year = {2012}, month = {DEC}, pages = {336{\textendash}345}, abstract = {

A new rhodamine-based receptor, derivatized with an additional fluorophore (quinoline), was synthesized for selective recognition of Hg2+ and Cr3+ in an acetonitrile/HEPES buffer medium of pH 7.3. This reagent could be used as a dual probe and allowed detection of these two ions by monitoring changes in absorption and the fluorescence spectral pattern. In both instances, the extent of the changes was significant enough to allow visual detection. More importantly, the receptor molecule could be used as an imaging reagent for detection of Hg2+ and Cr3+ uptake in live human cancer cells (MCF7) using laser confocal microscopic studies. Unlike Hg(ClO4)2 or Hg(NO3)2 salts, HgCl2 or HgI2 failed to induce any visually detectable change in color or fluorescence upon interaction with L1 under identical experimental conditions. Presumably, the higher covalent nature of HgII in HgCl2 or HgI2 accounts for its lower acidity and its inability to open up the spirolactam ring of the reagent L1. The issue has been addressed on the basis of the single-crystal X-ray structures of L1{\textperiodcentered}HgX2 (X{\textendash} = Cl{\textendash} or I{\textendash}) and results from other spectral studies.

}, doi = {10.1021/ic2017243}, author = {Saha, Sukdeb and Mahato, Prasenjit and Reddy, Upendar G. and Suresh, E. and Chakrabarty, Arindam and Baidya, Mithu and Ghosh, Sudip K. and Das, Amitava} } @article {42503, title = {Rhodamine-alginate conjugate as self-indicating gel beads for efficient detection and scavenging of Hg 2+ and Cr 3+ in aqueous media}, journal = {Chemical Communications}, volume = {48}, year = {2012}, month = {NOV}, pages = {1659-1661}, abstract = {

Effective extraction of Hg2+ and Cr3+ ions from aqueous media by novel rhodamine{\textendash}alginate polymer-based highly fluorogenic, as well as colorimetric, chemosensor beads.

}, doi = {10.1039/C1CC16554B}, author = {Saha, Sukdeb and Chhatbar, Mahesh U. and Mahato, Prasenjit and Praveen, L. and Siddhanta, A. K. and Das, Amitava} } @article {42513, title = {Taco complex derived from a bis-crown ether capable of executing molecular logic operation through reversible complexation}, journal = {Journal of Organic Chemistry}, volume = {77}, year = {2012}, month = {JUL}, pages = {6789{\textendash}6800}, abstract = {

As learned from natural systems, self-assembly and self-sorting help in interconnecting different molecular logic gates and thus achieve high-level logic functions. In this context, demonstration of important logic operations using changes in optical responses due to the formation of molecular assemblies is even more desirable for the construction of a molecular computer. Synthesis of an appropriate divalent as well as a luminescent crown ether based host 1 and paraquat derivatives, 2(PF6)2 and 3(PF6)2, as guests helped in demonstrating a reversible [3](taco complex) (1{\textperiodcentered}{2(PF6)2}2 or 1{\textperiodcentered}{3(PF6)2}2) formation in nonpolar solvent. Detailed 1H NMR studies revealed that two paraquat units were bound cooperatively by the two crown units in 1. Because of preorganization, the flexible host molecule 1 adopts a folded conformation, where each of two paraquat units remain sandwiched between the two aromatic units of each folded crown ether moiety in 1. Disassembly of the {\textquotedblleft}taco{\textquotedblright} complex in the presence of KPF6 and reassembly on subsequent addition of DB18C6 was initially demonstrated by 1H NMR spectral studies, which were subsequently corroborated through luminescence spectral studies. Further, luminescence spectral responses as output signals with appropriate and two independent molecular inputs could be correlated to demonstrate basic logic operation like OR and YES gates, while the results of the three molecular inputs could be utilized to demonstrate important logic operation like an INHIBIT gate.

}, doi = {10.1021/jo300622b}, author = {Mandal, Amal Kumar and Das, Priyadip and Mahato, Prasenjit and Acharya, Suhash and Das, Amitava} } @article { ISI:000341288500041, title = {Overview of the recent developments on Hg2+ recognition}, journal = {RSC Advances}, volume = {4}, number = {68}, year = {2014}, month = {JUN}, pages = {36140-36174}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Adverse influences of mercury on living organisms are well known. Despite efforts from various regulatory agencies, the build-up of Hg2+ concentration in the environment is of serious concern. This necessitates the search for new and efficient reagents for recognition and detection of Hg2+ in environmental samples as well as for application in diagnostics. Among various detection processes adopted for designing such reagents, generally methodologies that allow associated changes in spectra properties are preferred for the obvious ease in the detection process. Significant changes in the electronic spectral pattern in the visible region of the spectrum also induce detectable changes in solution colour for naked-eye detection and are useful for developing reagents for in-field sample analysis with yes-no type binary responses. However, reagents that allow detection of Hg2+ with associated fluorescence on response are useful for detection of Hg2+ in environmental samples, as well as for use as an imaging reagent, for detection of cellular uptake. High spin-orbit coupling constant for Hg2+ along with its high solvation energy in aqueous medium poses a challenge in developing efficient reagents with fluorescence on response that work in aqueous medium/physiological condition. To get around this problem, several methodologies, like conversion of rhodamine derivative spirolactam to strongly fluorescent xanthenes that form on binding to Hg2+, chemodosimetric reaction for generation of a new luminescent derivative, have been adopted. Apart from these, modified charge transfer processes on binding to Hg2+ have also been utilized for designing reagents for optical detection of Hg2+. Immobilization of such reagents on solid surfaces also led to the development of self-indicating Hg2+ ion scavengers. All such examples are discussed in the present review.

}, issn = {2046-2069}, doi = {10.1039/c4ra03594a}, author = {Mahato, Prasenjit and Saha, Sukdeb and Das, Priyadip and Agarwalla, Hridesh and Das, Amitava} }