Browsing by Author "Arnab Biswas"

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A dual-responsive "turn-on" bifunctional receptor: A chemosensor for Fe3+ and chemodosimeter for Hg2+
(Royal Society of Chemistry, 2015) Sujay Mukhopadhyay; Rakesh Kumar Gupta; Arnab Biswas; Amit Kumar; Mrigendra Dubey; Maninder Singh Hundal; Daya Shankar Pandey
Synthesis of L1-L3, their thorough characterization by spectral as well as structural studies and use in selective photochemical detection of Fe3+ and Hg2+ at ppb level have been described. Notably, these exhibit bifunctional behaviour toward Fe3+ (CHEF) and Hg2+ (chemodosimetric) which has been unequivocally established by various studies. © The Royal Society of Chemistry 2015.
A highly selective and femto-molar sensitive fluorescence 'turn-on' chemodosimeter for Hg2+
(2014) Sujay Mukhopadhyay; Arnab Biswas; Rampal Pandey; Rakesh Kumar Gupta; Daya Shankar Pandey
A selective fluorescence 'turn-on' chemodosimeter N,N′-bis-(4- cyanobenzylidene)-2,4,6-trimethylbenzene-1,3-diamine (3) based on a Schiff base for femto-molar detection of the Hg2+ has been described. It presents the highest level of detection limit for Hg2+ through Schiff base hydrolysis. © 2014 Elsevier Ltd. All rights reserved.
Anion triggered metallogels: Demetalation and crystal growth inside the gel matrix and improvement in viscoelastic properties using Au-NPs
(Royal Society of Chemistry, 2016) Arnab Biswas; Mrigendra Dubey; Sujay Mukhopadhyay; Ashish Kumar; Daya Shankar Pandey
Progelator complex Zn-TRPA-2 undergoes Cl- triggered gelation to afford ZTP2G, while Zn-TRPA-2 capped Au-NPs under similar conditions gave another gel GNZTP2G which also represents a rare nano-composite metallogel. When Zn-TRPA-2 was triggered by Cl- and NO3- simultaneously, crystals of demetalated species NA-TRPA-2 grew inside the ZTP2G matrix. Interestingly, GNZTP2G exhibits superior viscoelastic properties over ZTP2G. © The Royal Society of Chemistry 2016.
Detection of copper(II) and aluminium(III) by a new bis-benzimidazole Schiff base in aqueous media via distinct routes
(Royal Society of Chemistry, 2015) Ashish Kumar; Amit Kumar; Mrigendra Dubey; Arnab Biswas; Daya Shankar Pandey
The synthesis is described of a new bis-benzimidazole appended Schiff base ligand [2-(3,5-bis(1H-benz-imidazol-2-yl)-phenyliminomethyl)phenol] (H3L) followed by its thorough characterization by elemental analyses, spectroscopic studies (FT-IR, 1H, 13C NMR, ESI-MS, UV/vis, fluorescence) and X-ray single crystal analyses. The excellent selectivity of H3L towards Cu2+ and Al3+via distinct responses in mixed aqueous conditions was established by spectroscopic studies. The selective detection of Cu2+ due to the creation of complex 1 in which Cu2+ occupied only the salen-type N2O2 coordination site and the strong binding with Al3+ through both benzimidazole and salen moieties to yield complex 2 was confirmed by various studies. The disparate detection of these cations by H3L was substantiated by comparative studies, performed under analogous conditions, of the precursor compound 3,5-bis(1H-benzimidazol-2-yl)-aniline (BBA). The distinct interaction of H3L with Cu2+ and Al3+ and the sensing mechanisms were investigated in detail by spectroscopic studies and were supported by theoretical studies (Density Functional Theory). It has been clearly shown that the use of appropriate substituents may facilitate the design and development of probes suitable for the real time detection of more than one analyte. © The Royal Society of Chemistry 2015.
Environmental impacts of contract farming in potato cultivation
(EM International, 2015) Arnab Biswas; Gunja Kumari; Baldeo Singh
The study was conducted in Burdwan district of West Bengal with randomly selected 50 potato contract growers as respondents to assess the environmental impact of contract farming. From the study it was found that the major environmental drawback of contract farming as perceived by the farmers was emergence of new pest and disease of potato in the study area. Among the respondents, 52 per cent indicated that the potato contract farming is sustainable for the short term only. © EM International.
Exquisite 1D Assemblies Arising from Rationally Designed Asymmetric Donor-Acceptor Architectures Exhibiting Aggregation-Induced Emission as a Function of Auxiliary Acceptor Strength
(Wiley-VCH Verlag, 2016) Roop Shikha Singh; Sujay Mukhopadhyay; Arnab Biswas; Daya Shankar Pandey
One-dimensional nanostructures with aggregation-induced emission (AIE) properties have been fabricated to keep the pace with growing demand from optoelectronics applications. The compounds 2-[4-(4-methylpiperazin-1-yl)benzylidene]malononitrile (PM1), 2-{4-[4-(pyridin-2-yl)piperazin-1-yl]-benzylidene}malononitrile (PM2), and 2-{4-[4-(pyrimidin-2-yl)piperazin-1-yl]benzylidene}malononitrile (PM3) have been designed and synthesized by melding piperazine and dicyanovinylene to investigate AIE in an asymmetric donor-acceptor (D-A) construct of A′-D-π-A- topology. The synthetic route has been simplified by using phenylpiperazine as a weak donor (D), dicyanovinylene as an acceptor (A), and pyridyl/pyrimidyl groups (PM2/PM3) as auxiliary acceptors (A′). It has been established that A′ plays a vital role in triggering AIE in these compounds because the same D-A construct led to aggregation-caused quenching upon replacing A′ with an electron-donating ethyl group (PM1). Moreover, the effect of restricted intramolecular rotation and twisted intramolecular charge transfer on the mechanism of AIE has also been investigated. Furthermore, it has been clearly shown that the optical disparities of these A′-D-π-A architectures are a direct consequence of comparative A′ strength. Single-crystal X-ray analyses provided justification for role of intermolecular interactions in aggregate morphology. Electrochemical and theoretical studies affirmed the effect of the A′ strength on the overall properties of the A′-D-π-A system. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Fine-Tuning of Saponification-Triggered Gelation by Strategic Modification of Peripheral Substituents: Gelation Regulators
(Wiley-VCH Verlag, 2016) Ashish Kumar; Roop Shikha Singh; Amit Kumar; Afsar Ali; Arnab Biswas; Daya Shankar Pandey
A pioneering approach towards controlling the efficiency of saponification assisted gelation in ethyl ester based ZnII-complexes have been described. Using four new ester containing bis-salen ZnIIcomplexes (C1–C4) involving different para-azo phenyl substituted ligands it has been clearly shown that gelation efficiency is greatly influenced by the electronic effects of the substituents (-H (C1), -CH3(C2), -NO2(C3), and -OCH3(C4)). Morphological, photophysical, and rheological investigations corroborated the experimental observations well and established that gelation efficiency was enhanced with electron-withdrawing characteristics of substituents (C4
Glycosyl based meso-substituted dipyrromethanes as fluorescent probes for Cd2+/Cu2+ ions
(2013) Arnab Biswas; Rampal Pandey; Divya Kushwaha; Mohammad Shahid; Vinod Kumar Tiwari; Arvind Misra; Daya Shankar Pandey
Synthesis of new glycosyl based meso-substituted dipyrromethanes 1-3 has been described. Crystal structure of the representative compound 1 has been determined by X-ray single crystal analysis. The compounds 1 and 3 exhibit fluorescent 'Turn-On' and 'Turn-Off' signaling for Cd2+ and Cu 2+ ions. Notably, meso-galactosyl dipyrromethane 2 remains silent toward tested metal ions. © 2013 Elsevier Ltd. All rights reserved.
Manipulating Metallogel Properties by Luminogens and Their Applications in Cell Imaging
(American Chemical Society, 2018) Arnab Biswas; Sujay Mukhopadhyay; Roop Shikha Singh; Ashish Kumar; Nishant Kumar Rana; Biplob Koch; Daya Shankar Pandey
Manipulating gelation properties of the isomeric zinc-terpyridine complexes C-1 (nongelator) and C-2 (gelator) using three different luminescent dyes, viz., acridine yellow (AY), ethidium bromide (EB), and azido-boron dipyrromethene, have been described. Hybrid gels created by the combination of C-1, C-2, and above-mentioned dyes have been termed complex-luminogen mixed gels (CLMGs). Ensuing CLMGs have been thoroughly characterized by spectral, morphological, and rheological studies. Cytotoxicity measurements and imaging against breast cancer cell line MDA-MB-231 unveiled that three out of the five CLMGs can be effectively used for cell imaging. Interestingly, direct use of the metal-containing hybrid gels for live cell imaging which is a distinctive approach, has been successfully achieved with significantly encouraging results. Copyright © 2018 American Chemical Society.
Molecular and Nanoaggregation in Cyclometalated Iridium(III) Complexes through Structural Modification
(Wiley-VCH Verlag, 2016) Sujay Mukhopadhyay; Roop Shikha Singh; Arnab Biswas; Biswajit Maiti; Daya Shankar Pandey
New terpyridyl ligands TP1, TP2 and cyclometalated iridium(III) complexes 1 and 2 based on these ligands have been synthesized. The ligands and complexes have been characterized by elemental analysis and spectroscopic studies (ESI-MS,1H and13C NMR, UV/Vis, fluorescence). The molecular structure of 1 has been verified by X-ray single-crystal analysis. It has been unambiguously established that variation of the substituents on 1 and 2 leads to molecular aggregation in 1, while 2 remains nonaggregated. Furthermore, complexes 1 and 2 have been successfully utilized as capping agents for the stabilization of gold nanoparticles (AuNPs). It is of note that 1 forms discretely, while 2 aggregates AuNPs through the assemblage of ultrasmall nanoparticles. It has been affirmed by1H NMR titration studies that –NH groups from 1 and 2 are involved in the capping of AuNPs. The role of simple structural variations in directing molecular and nanoaggregation has been clearly established for the first time by spectroscopic (UV/Vis, fluorescence,1H NMR titration) and morphological studies [SEM, TEM, EDX (energy-dispersive X-ray), DLS (dynamic light scattering)]. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Photochemical water oxidation by cyclometalated iridium(iii) complexes: A mechanistic insight
(Royal Society of Chemistry, 2016) Sujay Mukhopadhyay; Roop Shikha Singh; Arnab Biswas; Daya Shankar Pandey
The proficiency of the cyclometalated iridium complexes [(η5-C5Me5)IrCl(L1)] (1), [(η5-C5Me5)IrCl(L2)] (2) and [(η5-C5Me5)IrCl(L3)] (3) has been examined towards photochemical water oxidation. The involvement of Ir(iv/v) in the catalytic process has been explored via CV, UV/vis, XPS spectroscopic studies and appreciable TON relative to the theoretical value of 1 from GC. © The Royal Society of Chemistry 2016.
Small Organic Non–gelators Evincing Radical Control over Morphology and Rheology of a Weak Metallogel
(Wiley-Blackwell, 2016) Arnab Biswas; Sujay Mukhopadhyay; Roop S. Singh; Daya S. Pandey
Two arrays of “Inorganic-Organic Mixed Gels” (IOMGs) based on terpyridyl complexes have been synthesized combining progelator/non-gelators with easily available, inexpensive and non-reactive small organic non-gelators (SOnGs). This new class of multicomponent gels displays radical changes in morphological patterns and enormous enhancement in their viscoelastic properties relative to weak metallogel (ZTP2G) derived from the progelator only. It has been unequivocally shown that twisting or coiling in gels diminishes as well as their viscoelastic strengths with simple alteration of heteroatoms, their number and positions in SOnGs. Multicomponent gelation is quite complicated considering the susceptibility of anion triggered metallogels towards various external stimuli which has been profoundly outdone. The present approach may be extremely beneficial for negating limitations in the usage of weak metallogels with promising efficacy in specified areas. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim