Browsing by Author "Sarkar, Madhushree"

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Amide-to-Amide Hydrogen Bonds in the Presence of a Pyridine Functionality: Crystal Structures of Bis(pyridinecarboxamido)alkanes
(ACS, 2005-09-09) Sarkar, Madhushree
Crystal structures of bis(4-pyridinecarboxamido)alkane and bis(3-pyridinecarboxamido)alkane derivatives were determined and analyzed in terms of hydrogen bond networks. Seven crystal structures out of the eight structures studied exhibited amide-to-amide hydrogen bonds. Out of these seven, five form the anticipated β-sheet network whereas two structures form a doubly interpenetrated (4,4)-network. In only one structure does the pyridyl group interfere in the amide-to-amide hydrogen bond, leading to the formation of an N−H···N hydrogen bond network. The analyses and rationalization of these structures and also related derivatives in the Cambridge Structural Database suggested that amide-to-amide hydrogen bond formation depends on the interplanar angle between amide and pyridine groups.
Assembling one-dimensional coordination polymers into three-dimensional architectures via hydrogen bonds
(Springer, 2010-10-16) Sarkar, Madhushree
The reactions of bis(pyridylcarboxamido)alkanes (amides) and bis(3-pyridyl)alkanediamides (reverse amides) with copper(II) and zinc(II) in the presence of various anions resulted in one-dimensional polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the one-dimensional networks observed here are of three types: simple linear chain, chains with wavy nature and chains containing cavities. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N-H…O hydrogen bonds.
Bis(2-pyridyl)diimine as a naked eye colorimetric fluorescence turn off probe selectively for Fe(II) ions as a consequence of energy changes in the electronic states upon complexation
(Elsevier, 2022-08) Sarkar, Madhushree
Bis(pyridyl)diimine, (1E,1′E)-N,N'-(ethane-1,2-diyl)bis(1-(pyridin-2-yl)methanimine) (L) has coordinating nitrogen atoms in effective positions to form stable chelates with metal ions and is capable of capturing a range of transition metal ions. However, the selective colorimetric response of Fe(II) by using L was observed. Colourless to purple coloured transition resulted on complexation of L with Fe(II) ions selectively and was not affected by the presence of other transition metal ions including Fe(III) ions. Photoluminescence studies have shown the quenching of emission maxima corresponding to L in the presence of Fe(II) ions along with appearance of new peaks at higher wavelength regions. Appearance of a specific color change, which can be visualized by naked eye and an added photophysical feature involving quenching of emission spectra, particularly for Fe(II) are associated with the changes in the electronic state energies of L upon complexation with Fe(II). Thermodynamic estimation of complex stability was done by determining the binding constant of the complex, which was found to be 7.2 × 1010 M−2 using Yoe Jones method. A binding ratio of 1:2 for L and Fe2+ was determined experimentally with help of mole ratio method, which hinted at the geometrical possibilities of the complex of L with Fe(II).). Limit of detection (LOD) for the identification of Fe(II) ions with L was determined using colorimetric naked eye method and was found to be 25 μM. Further L was also used to detect Fe(II) in real sample i.e. river water. NMR analysis supported the low spin state of Fe(II) in the Fe(II)-L complex. Anticipated geometry of the Fe(II)-L complex was optimized using Gaussian09 software through the B3LYP method, which upon investigation of the energies of frontier molecular orbitals, provided the details related to the electronic properties associated with the complexation of Fe(II) and L.
Bis(pyridyl)-disulfonamides: structural comparison with their carboxamidic analogues and the effect of molecular geometry and supramolecular assembly on their photophysical properties
(RSC, 2022) Sarkar, Madhushree
The presence of sulphur and carbon atoms, respectively, in the amidic functional group in sulphonamides and carboxamides resulted in differences in the molecular geometry and electronic effect associated with the compounds. Three new disulfonamides, N1,N3-di(pyridin-2-yl)benzene-1,3-disulfonamide (L1), N1,N3-di(pyridin-3-yl)benzene-1,3-disulfonamide (L2) and N1,N3-di(pyridin-4-yl)benzene-1,3-disulfonamide (L3), have been synthesized to analyse the structural features in order to obtain an understanding of the presence of hydrogen bond synthons in amidic functional groups in the presence of different atomic centres. Disulfonamides have been characterized by single crystal XRD and structural comparison with dicarboxamides made important revelations regarding the dependence of geometry and electronic factors on the formation of varied hydrogen bond synthons. Hirshfeld surface (HS) analysis has been performed on L1, L2, L2′ and L3′, where L2' and L3' are the carboxamidic analogues of L2 and L3, in order to determine the intermolecular interactions present in the crystal lattice. HS analysis is in good agreement with the single crystal XRD analysis of the hydrogen bonding interactions. Further the photophysical properties of the disulfonamides have been studied and rationalized in terms of their supramolecular assembly in the solid state. Among the three disulfonamide compounds, L1 and L3 have shown aggregation caused quenching (ACQ), while the interesting aggregation induced emission (AIE) phenomenon has been observed in L2
Bis-Pyridyl Diimines as Selective and Ratiometric Chemosensor for Ni(II) and Cd(II) Metal Ions
(Wiley, 2019-01) Sarkar, Madhushree
A pyridyl based Schiff base compound, (1E,1′E)-N,N′-(butane-1,4-diyl)bis(1-(pyridin-2-yl)methanimine) (2pdab) was observed to serve as a highly selective and sensitive ratiometric chemosensor for Ni2+ and Cd2+ ions. Mole ratio method and Yoe Jone's method showed a 1:1 binding mode of metal ions (Ni2+ and Cd2+) with 2pdab, while a binding constant of 26.88 ×106 L/mol and 4.29×106 L/mol, for Ni2+ and Cd2+, respectively, was determined. The limit of detection of 2pdab in sensing Ni2+ and Cd2+ was observed to be 3.08 μM and 1.4688 μM, respectively. The selectivity of 2pdab to detect Cd2+ and Ni2+ among various other competitive ions was also studied. The sensor, 2pdab, was applied in real time application for detection of nickel ion in river water sample
BODIPY(aryl)iodonium salts in the efficient synthesis of diversely functionalized BODIPYs and selective detection of serum albumin
(RSC, 2024-04) Kumar, Dalip; Sarkar, Madhushree
BODIPY(aryl)iodonium salts were readily accessible from the high-yielding reaction of BODIPY with iodoarenes or hydroxyl(tosyloxy)iodoarenes in the presence of m-CPBA. The prepared BODIPY(aryl)iodonium salts bearing substituents of varied electronic nature were utilized for the direct syntheses of thiocyanate, azide, amine and acrylate functionalized BODIPYs and β,β′-bis-BODIPYs. The regioselective syntheses of α-piperidinyl and β-piperidinyl substituted BODIPYs were achieved through the reaction of BODIPY(aryl)iodonium salts with piperidine in the absence and presence of copper(I). Expeditious and high yielding (79–82%) synthesis of β,β′-bis-BODIPYs was also developed through the palladium-catalyzed reductive coupling of the easily accessible BODIPY(aryl)iodonium salts. Some of the indole-appended BODIPYs and bis-BODIPYs displayed strong absorption in the visible region (∼610 nm). The BODIPY(aryl)iodonium salts also showed significant binding with serum albumin and were observed to be selective serum protein sensors with estimated limits of detection as low as 7 μg mL−1 in some cases.
Controlling light emitting properties in bis(pyrenyl)-di-imines by tuning the chemical functionality of the spacer group
(RSC, 2021) Sarkar, Madhushree
Aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) are dictated by the molecular aggregation which in turn is decided by the chemical features present in a molecule. The photophysical properties of bis(pyrenyl)-di-imines were investigated in solution as well as the solid state. It was observed that the light-emitting properties are dependent on the type of spacer group present in the compound. The presence of an alkylene spacer [ethylene (L3), butylene (L4), and hexylene (L5)] in bis(pyrenyl)-di-imines showed AIE at higher concentrations as well as in the solid state whereas the presence of a phenylene (L1) spacer and the absence of any alkyl/aryl spacer (L2) in the compound have resulted in ACQ in the solid state. Crystal structure analysis of L1 has explained its non-emissive nature in the solid state, while the AIE in the compounds, L3–L5, where flexible alkylene spacers are present, provided an idea about the solid-state arrangement of the molecules.
Cooperative effect of “flexible” interaction and “flexible” framework in reversible intake and removal of aromatic guest molecules
(RSC, 2013) Sarkar, Madhushree
The metal–organic frameworks of amide based “flexible” ligands has been explored. The reaction of bis-(3-pyridyl)ethanediamide with Cu(PF6)2 resulted in a 1D looped chain, where the PF6− anions interact with the amide groups of the chains. This resulted in unavailability of space for guest inclusion in the loops. The exchange of PF6− ion with ClO4− ion resulted in the intake of aromatic guest molecules, which were monitored by IR and UV-Vis spectroscopy. The capability of the flexible ethyl spacer of bis-(3-pyridyl)ethanediamide to adjust the conformation according to the requirements of the other components of the networks is observed in the present study. This resulted in reversible inclusion and removal of guest molecules triggered by the exchange of anions.
Coordination Polymers Comprised of an Exo Bifunctional Schiff Base Ligand and Succinate Dianion: Critical Analysis of Factors Affecting the Structures and Framework Dimensionality
(Wiley, 2017-12-18) Sarkar, Madhushree
The chemistry of Coordination Polymers (CPs) of an exo bidentate Schiff base ligand, L1b, 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene, where two pyridyl moieties are separated by imine groups, is discussed. The reaction of ligand L1b and disodium succinate with Cd(ClO4)2 resulted in CP1, which is a 2D bilayer structure. Previously, it was reported elsewhere that the reaction of L1b with Cd(NO3)2 followed by the addition of disodium succinate resulted in a 3D network, while the similar reaction with Cd(ClO4)2 resulted in a different 3D network. The result from the current study establishes that reaction conditions and the anion in the metal salt can be crucial in obtaining diversified networks for the same combination of metal center and ligand. The effect of reaction conditions on network geometry is critically analyzed by comparing their single crystal structures and various other parameters.
Coordination polymers of Ag(i) with di-Schiff base and diaminoalkanes: double helix, ladder, CdSO4 and zigzag-chain networks
(RSC, 2004) Sarkar, Madhushree
A new di-Schiff base ligand has been prepared from 3-acetylpyridine and 1,2-diaminoethane and its structure has also been characterized by single crystal X-ray diffraction. Furthermore, the ligand was found to form a 1 : 1 complex with Ag(NO3) in CH3CN. The crystal structure of the complex exhibits a 1D-double helix with the pitch length of 10 Å. In these reactions, the ligand was found to disintegrate into the individual components to form a crystal of a 3D-network which comprised of Ag(NO3) and 1,2-diamino ethane. Nitrate ions occupied the channels and form several N–H⋯O hydrogen bonds with the walls of the channels. Interestingly, the topology of the 3D-network was found to be similar to that of the CdSO4. This structure prompted us to study the reactions of Ag(NO3) with 1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane. The crystal structures of these complexes reveal that 1,2-diaminoethane forms the 3D-network similar to the above reaction, whereas 1,2-diaminopropane and 1,3-diaminopropane form a ladder and 1D-zigzag chain, respectively.
Crystal engineering of coordination polymers using 4,4'-bipyridine as a bond between transition metal atoms
(RSC, 2006) Sarkar, Madhushree
Coordination polymers have attracted an enormous interest among chemists due to their novel physical and chemical properties. This review describes the role of 4,4′-bipyridine in discovering various coordination polymers with novel topologies that range from one-dimensional to three dimensional. The geometries of coordination polymers of bipy include linear, zigzag, four-fold helices, molecular antenna, ladder, railroad, double, triple and quadruple chains, bilayer, square and rectangular grid, honeycomb layers, Lincoln Logs, 3D frames, diamondoid, 42·82 and cubic networks.
Crystal Engineering of Metal−Organic Frameworks Containing Amide Functionalities: Studies on Network Recognition, Transformations, and Exchange Dynamics of Guests and Anions
(ACS, 2007-06-07) Sarkar, Madhushree
The reactions of bis(pyridinecarboxamido)alkanes with copper(II) in the presence of various anions and solvent systems afforded several polymeric crystalline complexes with or without guest inclusion. The crystal structure analyses of these complexes reveal that the coordination networks observed here include open one-dimensional (1D) chains containing cavities and open (4,4)-networks with three types of packing modes, namely, mixed, offset−offset, and trigonal, doubly interpenetrated (4,4)-networks both in parallel and in perpendicular (diagonal/diagonal) modes and a three-dimensional pseudo-diamondoid (658-topology) network. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via N−H···O hydrogen bonds. The exchange of counteranions from the polymeric crystalline complexes was found to trigger the network transformations. The 1D chain, which has rectangular cavities, was transformed into a pseudo-diamondoid network upon exchange of ClO4- with PF6- anions. The exchange of anions from two-dimensional (2D) open (4,4)-networks resulted in 2D-interpenetrated networks. It was found that the reverse exchange that is expected to result in open networks from interpenetrated networks is not allowed. The guest molecules included in these networks range from small molecules such as H2O, EtOH, and CHCl3 to big aromatic molecules such as nitrobenzene, toluene, anisole, p-xylene, benzonitrile, and naphthalene. The exchange of guest molecules in crystal-to-crystal fashion was also found to trigger the transformations in the mode of packing of 2D layers.
Effects of non covalent interactions in light emitting properties of bis-pyridyl-alkyl-di-imines
(RSC, 2015) Sarkar, Madhushree
The crystal structures of three bis-pyridyl-alkyl-di-imines are studied. The non-covalent interactions lead to the packing of the crystals of the compounds in such a way that crystallization induced emission (CIE) is observed for bis-pyridyl-ethyl-di-imine and bis-pyridyl-butyl-di-imine, while for bis-pyridyl-di-imines, with no alkyl spacer, the luminescence is absent in the solid state. The enhanced emission in the solid state is attributed to the collective effects of planarization and the specific arrangement of molecules.
Entrapment of a Hexamer of Nitrobenzene Molecules between the Layers of (4,4)-Coordination Networks Containing Intra-β-Sheet Hydrogen Bonds
(Wiley, 2006-01-25) Sarkar, Madhushree
Two exo-bidentate pyridyl ligands containing diamides as spacers were shown to form non-interpenetrated 2D-coordination networks of (4,4)-geometry upon treatment with Cu(NO3)2 and NaSCN. The crystal structures reveal that both structures contain intralayer β-sheet hydrogen bonds. In one of these structures nitrobenzene occupies 60 % of the crystal volume included between the coordination networks. The nitrobenzene molecules form a layer which has the hexameric C–H···O hydrogen bonded aggregate as a basic building block
A facile and efficient synthesis of bodipy-based fluorescent probes for selective detection of hydrazine
(Wiley, 2024-11) Sarkar, Madhushree; Kumar, Dalip
A facile and ratiometric BODIPY-based fluorescent probe 4 was developed for the selective detection of hydrazine in solution phase. The BODIPY-based fluorophores 3 and 4 were easily prepared in high yields from the L-proline catalyzed reaction between α/β-formyl BODIPY 1 a/1 b and 3-cyanoacetylindole 2. Use of easily accessible substrates, benign solvent, catalytic amount of L-proline and high product yields are the advantageous features of the developed protocol. Prepared BODIPYs 3 (536 nm) and 4 (567 nm) showed bathochromic shifts (36–67 nm) in UV-Visible absorption maxima when compared to parent BODIPY (500 nm) in dichloromethane (DCM). The stable and economical BODIPY-based probe 4 exhibited rapid response and remarkable selectivity towards hydrazine when compared to other commonly occurring analytes. At low concentration, the BODIPY probe 4 (10 μΜ) is non-fluorescent, however, a significant enhancement in fluorescent (turn-on) was observed with the increasing concentration of hydrazine (0–100 μΜ). This change in fluorescent behaviour may be ascribed to intramolecular charge transfer (ICT) effect as supported by density functional theory (DFT) calculations. With a 4.3 μM detection limit, the BODIPY probe 4 was also found to be useful in detecting hydrazine in real environmental samples.
Increased Photocatalytic Activity of Post Synthetically Modified Coordination Polymer Derived from Bis-pyridyldiamide
(Wiley, 2020-07) Sarkar, Madhushree
A one-dimensional looped chain coordination polymer (CP1) is synthesized by the reaction of CoII with N1,N3-di(pyridine-4-yl)isophthalamide. Transmetalation reaction of CP1 with CuII showed single-crystal-to-single-crystal (SC-SC) transformation to form CP2, which is also a 1D looped chain. Both CP1 and CP2 showed the presence of DMF as guest molecules near the loops of the 1D chains. CP1 and CP2 were found to have bandgap of 2.41 eV and 1.30 eV, respectively, which were calculated by Tauc plot. The difference observed in the optical bandgap of CP1 and CP2 is reflected in photocatalytic dye degradation studies. It was observed that CP2 showed much greater efficiency in degrading the dyes (Methylene blue, Methyl orange and Rhodamine B) as compared to that of CP1. The polar nature of the loops of the chains in CP1 and CP2 due to the presence of DMF was exploited to study the adsorption and desorption of I2. Adsorption of I2 in CP1 and CP2 was found to follow first order kinetics with a rate constant of 8.32 × 10–5 s–1 for CP1 and 9.71 × 10–5 s–1 for CP2. Guest inclusion reaction was performed to incorporate benzotriazole in the CP1. Impedance measurements showed a higher conductivity in the benzotriazole incorporated CP1.
Interplay of Hydrogen Bonds in Assembling (4,4)-Coordination Networks: Transformations from Open to Interpenetrated Networks via Anion Exchange
(ACS, 2006) Sarkar, Madhushree
Open (4,4)-coordination networks were shown to assemble via N−H···O hydrogen bonds in two different ways: the usual offset packing via β-sheet hydrogen bonds and an unprecedented trigonal packing. Both of the structures have continuous channels that are occupied by guest molecules (nitrobenzene or EtOH and H2O) which account for 37% or 28% of the crystal volume. Interestingly, these complexes have shown an ability to exchange ClO4- with PF6- ions and transform into the doubly interpenetrated varieties.
Iodine(iii)-promoted regioselective and efficient synthesis of β-triazolyl BODIPYs for the selective recognition of nickel ions and bovine serum albumin
(RSC, 2022) Sarkar, Madhushree; Kumar, Dalip
Various β-triazolyl tethered BODIPYs were efficiently prepared in a sequential one-pot protocol involving the initial reaction of BODIPY with iodobenzene diacetate (IBD) and sodium azide to in situ generate BODIPY azides followed by a copper-catalyzed azide–alkyne cycloaddition reaction. Under the optimized reaction conditions, various β-triazolyl BODIPYs 5a–i were successfully prepared in good yields and adequately characterized by using UV, NMR, mass spectral data and XRD analyses. The UV-Visible spectra of the prepared β-triazolyl BODIPYs 5a–i showed intense absorption bands (514–545 nm) with a 13–44 nm red shift when compared with those of the parent BODIPY. The selective recognition of compound 5d towards Ni2+ ions (detection limit 0.26 nM) led to significant quenching in the fluorescence intensity over other selected bivalent metal ions. The complex formed between 5d and Ni2+ in a stoichiometry of 2 : 1 was found to have a binding constant of 7.5 × 105 M−1. The fluorescence of compound 5i gets enhanced gradually upon interaction with bovine serum albumin due to its selective and high binding affinity (1.25 × 105 M−1) with protein and a concomitant decrease in the total non-radiative decay rate.
Iodine(iii)-promoted regioselective and efficient synthesis of β-triazolyl BODIPYs for the selective recognition of nickel ions and bovine serum albumin
(RSC, 2022) Kumar, Dalip; Sarkar, Madhushree
Various β-triazolyl tethered BODIPYs were efficiently prepared in a sequential one-pot protocol involving the initial reaction of BODIPY with iodobenzene diacetate (IBD) and sodium azide to in situ generate BODIPY azides followed by a copper-catalyzed azide–alkyne cycloaddition reaction. Under the optimized reaction conditions, various β-triazolyl BODIPYs 5a–i were successfully prepared in good yields and adequately characterized by using UV, NMR, mass spectral data and XRD analyses. The UV-Visible spectra of the prepared β-triazolyl BODIPYs 5a–i showed intense absorption bands (514–545 nm) with a 13–44 nm red shift when compared with those of the parent BODIPY. The selective recognition of compound 5d towards Ni2+ ions (detection limit 0.26 nM) led to significant quenching in the fluorescence intensity over other selected bivalent metal ions. The complex formed between 5d and Ni2+ in a stoichiometry of 2 : 1 was found to have a binding constant of 7.5 × 105 M−1. The fluorescence of compound 5i gets enhanced gradually upon interaction with bovine serum albumin due to its selective and high binding affinity (1.25 × 105 M−1) with protein and a concomitant decrease in the total non-radiative decay rate
Is metal metathesis a framework-templating strategy to synthesize coordination polymers (CPs)? Transmetallation studies involving flexible ligands
(RSC, 2014) Sarkar, Madhushree
The coordination polymer (CP) of bis(3-pyridyl)butanediamide with Cu(ClO4)2 is a 2D network (CP-3-Cu), which showed two-fold parallel interpenetration, whereas with Cd(ClO4)2 it is a 1D network containing rectangular loops (CP-4-Cd). The metal metathesis of CP-4-Cd with Cu(II) resulted in the isomorphous replacement of the Cd(II) centre with Cu(II). Transmetallation reaction resulted in retaining the structural features of CP-4-Cd even in case of a flexible ligand. The CP formed via transmetallation couldn't be synthesized from a direct reaction of bis(3-pyridyl)butanediamide and Cu(ClO4)2. The transmetallation kinetic studies were performed with an atomic absorption spectrophotometer (AAS) and wavelength dispersive X-ray fluorescence (WDXRF).