Haldia Government College

Purba, India

Haldia Government College

Purba, India

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Mondal M.,University of Calcutta | Mondal M.,Haldia Government College | Giri S.,University of Calcutta | Guha P.M.,University of Calcutta | And 2 more authors.
Dalton Transactions | Year: 2017

A nickel(ii) complex [Ni2LR 2(CH3CN)4](ClO4)2·2CH3CN (1) has been synthesized by using a tridentate reduced Schiff base ligand, HLR, 2-[(3-methylamino-propylamino)-methyl]-4-nitrophenol and Ni(ClO4)2·6H2O. Stoichiometrically controlled addition of NH4SCN to the acetonitrile-water solution of 1 produced two other complexes, [Ni2LR 2(μ1,1-NCS)(CH3CN)2](ClO4)·CH3CN (2) and [Ni2LR 2(NCS)2 (CH3CN)2] (3) by replacing one and two coordinated CH3CN by NCS−, respectively. The dinuclear NiII complexes 1 and 3 are structurally very similar containing a diphenoxido bridge between the NiII ions. Complex 2 also consists of a dinuclear entity, but a μ1,1-isothiocyanato bridge is present in addition to the diphenoxido bridge. The magnetic measurements indicate that antiferromagnetic interactions (J = −33.85 cm−1) for 1, (J = −23.43 cm−1) and 3 and ferromagnetic interaction (J = 5.01 cm−1) for 2 are mediated between the intra-dimer NiII ions. The nature of coupling (ferromagnetic for 2 and antiferromagnetic for 1 and 3) is understandable from the phenoxido bridging angles (91.27° (av. angle) for 2, 102.41° for 1 and 102.42° for 3) but it cannot explain the considerable difference of J values between 1 and 3. Other important factors such as Ni⋯O bond distances, the out-of-plane shift of phenyl rings and the hinge distortions are also of no use for a possible explanation. With the help of computational evidence, we have identified for the first time that magnetic coupling could be dramatically modified by the non-bridging axially coordinated ligands: antiferromagnetic coupling becomes considerably stronger for a neutral ligand in comparison to the negatively charged ligand. Moreover, for a negatively charged axially coordinated ligand, antiferromagnetic coupling decreases with increase in crystal field strength. © The Royal Society of Chemistry.

Ray S.,University of Calcutta | Konar S.,University of Calcutta | Jana A.,University of Calcutta | Das K.,Haldia Government College | And 3 more authors.
Polyhedron | Year: 2013

One binuclear Cu(II) complex, [Cu2(L1) 2(N3)2] (1), and a trinuclear Cu(II) complex, [Cu3(L2)3(μ1,1N3) 2](ClO4) (2), of two potentially tridentate NNO-donor Schiff base ligands, [2-(1-(2-(4,6-dimethylpyrimidin-2-yl)hydrazono)ethyl) phenol] (HL1) and [2-((2-(4,6-dimethyl pyrimidin-2-yl) hydrazono) methyl) phenol] (HL2), have been synthesized and characterized by elemental analyses, UV-Vis IR spectroscopy, DFT and single crystal X-ray crystallography. The ligands HL1 and HL2 are [1 + 1] condensation products of 2-hydrazino-4,6-dimethylpyrimidine with 2-hydroxy acetophenone and salicylaldehyde respectively. In 1, the two Cu(II) centers are bridged by μ-phenoxo groups. In 2, the three Cu(II) centers are held together by two μ1,1 bridging azide ions and a phenoxo oxygen atom which binds the three metal centers and behaves as a μ3-O atom. The geometries of the complexes have been optimized using the UB3LYP level of theory. The calculation confirms that all the copper centers are five coordinate with distorted square pyramidal geometries, which is consistent with the experimental data. © 2012 Elsevier Ltd. All rights reserved.

Konar S.,University of Calcutta | Jana A.,University of Calcutta | Das K.,Haldia Government College | Ray S.,University of Calcutta | And 2 more authors.
Inorganica Chimica Acta | Year: 2013

Three new zig-zag 1D coordination polymers and a binuclear complex of Cu(II) involving pyrazole based tri- and pentadentate schiff base ligands (Z)-2-(2-(5-methyl-1H-pyrazole-3-carbonyl)hydrazono)-2- phenylacetic acid (L'1) and (Z)-2-(2-(5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbonyl) hydrazono)-2- phenylacetic acid (L'2) are reported in this work. The ligand precursors L1 and L2 have been transformed into L1' and L2' during the course of reaction with metal ions in which the ester groups have been changed to carboxylate group. The 1D coordination polymers, namely, [Cu(L'1)(ClO4) 2(H2O)]n (1), [Cu(L'2)(- ClO 4)]n (3), [Cu(L'2)(NO3)]n (4) and a binuclear complex [Cu2(L'1)2Cl2] (2) have been synthesized. The complexes 1-3 are of distorted octahedral geometry and the complex 2 is distorted square pyramidal. Interestingly, these structural variations are dependent on counterions and substituent on the pyrazole ring. These have been characterized by elemental analyses, UV, IR, single crystal X-ray diffraction, electrochemical and photoluminescence studies. L'1 serves as tridentate NNO donor where pyrazole nitrogen, azomethine nitrogen and ligand carboxylate group are coordinatively active, leaving the carbonyl oxygen of carbohydrazide part inactive. The same situation (coordination modes) arises in another pentadentate NNNOO donor L'2 where extra pyridine nitrogen is coordinated. The complexes 3 and 4 have considerable fluorescence emission while the rest of the complexes and the ligand molecules are fluorescent silent. © 2012 Elsevier B.V. All rights reserved.

Dhara A.,University of Calcutta | Jana A.,University of Calcutta | Konar S.,University of Calcutta | Ghatak S.K.,University of Calcutta | And 5 more authors.
Tetrahedron Letters | Year: 2013

A novel rhodamine-based chemosensor, 3′,6′-bis(diethylamino)-2- ((2,7-dimethoxy-9H-fluoren-9-ylidene)amino)spiro[isoindoline-1,9′-xanthen] -3-one (1) for aluminum ion, was designed and synthesized. Compound 1 is an orange colored, weak fluorescent compound which was synthesized via one-step facile reaction of rhodamine B hydrazide with 2,7-dimethoxy-9H-fluoren-9-one in MeOH. When Al3+ salt was added in methanol:water (30:70, v/v) solution then spirolactum ring of 1 was opened. The absorbance and fluorescence of the mixed solution were increased dramatically because of the opening of the lactum ring. Thus, signal transduction occurred via reversible CHEF (chelation-enhanced fluorescence) mechanism in the range 580-584 nm. © 2013 Elsevier Ltd. All rights reserved.

Manna S.K.,Haldia Government College | Mondal S.K.,Haldia Government College | Ahmed A.,Indian Institute of Technology Kharagpur | Mandal A.,Haldia Government College | And 4 more authors.
RSC Advances | Year: 2014

An efficient one pot synthesis of polycyclic benzimidazole derivatives has been developed (up to 90% yield). The protocol is very mild, metal-free, and not restricted to anhydrous conditions. It also demonstrates an example of preferential electrocyclic reaction over Michael reaction. These new benzimidazole derivatives are highly fluorescent and show a dramatic change with pH; The characteristic bright bluish fluorescence was observed in MeOH (UV-light, 366 nm) but the intensity was totally diminished at pH = 2.5. © 2014 The Royal Society of Chemistry.

Das U.,Haldia Government College | Das U.,Jadavpur University | Chattopadhyay B.,Indian Association for The Cultivation of Science | Mukherjee M.,Indian Association for The Cultivation of Science | Mukherjee A.K.,Jadavpur University
Chemical Physics Letters | Year: 2011

Crystal structures of three derivatives of phenylpropionic acid, 2, 3 and 4 with hydroxyl, methyl and methoxy substitutions at the 2, 4 positions have been determined from X-ray powder diffraction data and their electronic structures were calculated at the DFT level. The optimized molecular geometries agree closely to that obtained from the crystallographic analysis. Intermolecular O-H...O hydrogen bonds generate R22(8) rings, which are further connected through O-H...O and C-H...O hydrogen bonds into two-dimensional framework in 2 and 4, and a step like architecture in 3. The HOMO-LUMO energy gap (>4.0 eV) indicates a high kinetic stability of the three compounds. © 2010 Elsevier B.V. All rights reserved.

Das U.,Haldia Government College | Das U.,Jadavpur University | Chattopadhyay B.,Indian Association for The Cultivation of Science | Mukherjee M.,Indian Association for The Cultivation of Science | Mukherjee A.K.,Jadavpur University
Crystal Growth and Design | Year: 2012

The structure determination of 3-phenylpropionic acid (1), 3-(3-methylphenyl) propionic acid (5), and 3-(3- methoxyphenyl) propionic acid (6), all three compounds crystallizing in the monoclinic space group P2 1/a (or P2 1/n) with Z′ = 2, has been accomplished from laboratory X-ray powder diffraction data following the direct space approach. The nature of intermolecular interactions in 1, 5, and 6 has been analyzed using the Hirshfeld surfaces and 2D fingerprint plots. While the two molecules (A and B) in the crystallographic asymmetric unit of 6 display almost identical conformation, those in 1 and 5 are significantly different due a rotation about the C-C bond linking the planar aromatic ring and propionic acid fragments. The presence of the COOH functional group in the compounds promotes the formation of cyclic R 2 2(8) synthons via intermolecular O-H•••O hydrogen bonds. Further linking of molecules through intermolecular C-H•••O and C-H•••π hydrogen bonds generates a three-dimensional supramolecular architecture in 1 and 5 and a two-dimensional molecular sheet in 6. Hirshfeld surface analyses of 1, 5, and 6 as well as a few substituted phenylpropionic acids retrieved from the Cambridge Structure Database (CSD) indicate that 94-99% of Hirshfeld surface areas in this class of compounds are due to H•••H, O•••H, and C•••H contacts. © 2011 American Chemical Society.

Pal P.J.,Dumkal Institute of Engineering and Technology | Saha T.,Haldia Government College | Sen M.,Indian Institute of Technology Kanpur | Banerjee M.,Indian Institute of Technology Kanpur
Nonlinear Dynamics | Year: 2012

In this paper, we consider a delayed predator-prey system with intraspecific competition among predator and a strong Allee effect in prey population growth. Using the delay as bifurcation parameter, we investigate the stability of coexisting equilibrium point and show that Hopf-bifurcation can occur when the discrete delay crosses some critical magnitude. The direction of the Hopf-bifurcating periodic solution and its stability are determined by applying the normal form method and the centre manifold theory. In addition, special attention is paid to the global continuation of local Hopf bifurcations. Using the global Hopf-bifurcation result of Wu ({Trans. Am. Math. Soc.} 350:4799-4838, 1998) for functional differential equations, we establish the global existence of periodic solutions. Numerical simulations are carried out to validate the analytical findings. © 2011 Springer Science+Business Media B.V.

Sahoo S.,Haldia Government College | Sengupta D.,Indian Statistical Institute
Statistics in Medicine | Year: 2016

In this paper, we present a class of graphical tests of the proportional hazards hypothesis for two-sample censored survival data. The proposed tests are improvements over some existing tests based on asymptotic confidence bands of certain functions of the estimated cumulative hazard functions. The new methods are based on the comparison of unrestricted estimates of the said functions and their restricted versions under the hypothesis. They combine the rigour of analytical tests with the descriptive value of plots. Monte Carlo simulations suggest that the proposed asymptotic procedures have reasonable small sample properties. The power is much higher than existing graphical tests and comparable with existing analytical tests. The method is then illustrated through the analysis of a data set on bone marrow transplantation for Leukemia patients. © 2016 John Wiley & Sons, Ltd.

Sources of sediments have been identified through study of mineral composition of sediments in the lower reach of the Rupnarayan River, West Bengal, India by X-ray diffraction (XRD) technique to understand the causes and mechanisms of sedimentation. Collected sediment samples are washed by hot and distilled water, dried and disaggregated manually with a mortar and pestle. Sediment samples are scanned at 7°–45°2θ interval by XPERT-PRO diffractometer. Diffractograms generated from XRD analysis reveals that the entire reach under study shows the dominance of minerals including quartz, illite, chlorite, chloritoid, anatase, goethite, oligoclase, sillimanite and corundum, having their origin in the upper and middle catchment with little contribution from lower catchment and river banks. Statistical test indicates that except tourmaline and anatase, all the minerals show steady trend in concentration in sediments. PCA reveals that five Eigen values account for 82.092% of the total variation of the distribution of minerals. There is no conspicuous trend in the spatial distribution of the minerals in the study area. The minerals drained from upper catchment are caught up in the estuary and again redistributed upstream by stronger flood tide. This leads to an unsystematic and irregular distribution of minerals in the study area. © 2016 Elsevier Ltd

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