Articles written in Journal of Chemical Sciences

    • Ferroverdin: Cation variation and recognition of isomerictris chelate geometries by iron oxidation states

      Surajit Chattopadhyay Partha Basu Debashis Ray Samudranil Pal Animesh Chakravorty

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      Synthetic ferroverdins, NaFe11(RQ)3 afford trinuclear M[Fe(RQ)3]2 upon reaction with bivalent ions (M2+). A probable bonding mode is considered. Ferric ions oxidise ferroverdin to ferriverdin, FeIII(RQ)3. Bothfac andmer isomers can be observed for ferro- and ferriverdins but at equilibrium the preferred isomers arefac for ferro- andmer for ferriverdin. Mismatch in geometry with oxidation state gets spontaneously corrected by isomerisation. Equilibrium constants, isomerisation rates, redox potentials and EPR spectra are examined. A study on the pattern of isomer population as a function of oxidation for other 3d analogues of ferro- and ferriverdin is initiated.

    • Copper(II) activated transformation of azomethine to imidate

      Satyanarayan Pal Nimma Rajaiah Sangeetha Samudranil Pal

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    • Copper(II) complexes with aroylhydrazones

      Samudranil Pal

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      The coordination chemistry of copper(II) with tridentate aroylhydrazones is briefly discussed in this article. Two types of aroylhydrazones derived from aroylhydrazines and ortho-hydroxy aldehydes or 2-pyridine-carboxaldehyde have been used. The characterization of the complexes has been performed with the help of various physico-chemical techniques. Solid state structural patterns have been established by X-ray crystallography. In the solid state, structural varieties of these complexes are seen to range from monomeric, dimeric, polymeric and one-dimensional self-assembly via hydrogen bonds and π-π interactions. EPR spectroscopy and variable temperature magnetic susceptibility measurements have been used to reveal the nature of the coordination geometry and magnetic characteristics of these complexes.

    • Cyclometallated ruthenium(II) carbonyl complexes with 1-pyrenaldehyde 4-R-3-thiosemicarbazones: Regioselective ruthenation of the 1-pyrenyl group

      Rupesh Narayana Prabhu Samudranil Pal

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      A facile method for the synthesis of a series of cyclometallated ruthenium(II) carbonyl complexes with 1-pyrenaldehyde 4-R-3-thiosemicarbazones (H2Ln where the two H’s represent the dissociable thioamide and pyrenyl protons; R = H, Me and Ph) has been described. The characterization of the complexes having the general molecular formula trans-[Ru(Ln)(CO)(EPh33)2] (where E = P or As) were accomplished by elemental (CHN) analysis, magnetic susceptibility and spectroscopic (ESI-MS, IR, UV-Vis, emission and 1H-NMR) measurements. Electronic spectra of the complexes display multiple strong absorptions in the range 440–224 nm due to intraligand transitions. All the complexes exhibit emission bands that are characteristic of ligand centred emissive states. X-ray diffraction studies with representative complexes reveal a pincer-like 5,5-membered fused chelate rings forming CNS coordination mode of the thiosemicarbazonate ligand (Ln)2− via regioselective activation of 1-pyrenyl ortho C–H and formation of a distorted octahedral C2NSE2 coordination sphere around the ruthenium(II) centre.

    • Synthesis and characterization of dodecahedral cerium(IV) and gadolinium(III) complexes with a tetradentate Schiff Base

      Tulika Ghosh Samudranil Pal

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      Reactions of CeCl3·6H2O and Gd(NO3)3·5H2O with biacetyl bis(benzoylhydrazone) (H2babh) and KOH in 1:2:2 mole ratio in methanol afford the complexes [Ce(babh)2] (1) and [Gd(babh)(Hbabh)]·H2O (2·H2O), respectively in good yields. Characterization of the complexes has been performed with the help of elemental analysis, magnetic susceptibility, spectroscopic (IR, UV-Vis, EPR and NMR) and X-ray crystallo-graphic measurements. 1 is diamagnetic and NMR active, while 2·H2O is paramagnetic (𝜇eff = 8.03 𝜇B at 300 K) and EPR active. The complexes crystallize as 1·CH2Cl2 and 2·H2O. X-ray structures show that the metal centre in each of 1 and 2 is in a distorted dodecahedral N4O4 coordination sphere assembled by two meridionally spanning ONNO-donor ligands. Self-assembly of 1·CH2Cl2 via intermolecular C−H···N and C−H···Cl hydrogen bonds and 𝜋-𝜋 interactions provides one-dimensional ‘ladder’ type structure. On the other hand, 2·H2O assembles into a two-dimensional ‘sheet’ like network through intermolecular N−H···O and O−H···N hydrogen bonds.

    • N-(acyl)-N'-(ferrocenylidene)hydrazines and their nickel(II) complexes: Syntheses, structures and physical properties


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      The Schiff bases N-(acyl)-N’-(ferrocenylidene)hydrazines (HFcah (1) and HFcbh (2), where acyl = acetyl in 1 and benzoyl in 2 and H represents the dissociable amide proton) were synthesized in high yields (74 and 81%) by condensation reactions of equimolar amounts of ferrocene-carboxaldehyde and the corresponding acylhydrazines in presence of acetic acid in refluxing methanol.Reactions of Ni(OAc) ₂·4H ₂O, the Schiff bases (1 and 2) and NaOAc ·3H ₂O in 1:2:4 mole ratio in refluxing methanol afforded the diamagnetic iron(II)-nickel(II)- iron(II) species [Ni(Fcah) ₂] (3) and [Ni(Fcbh) ₂] (4) in 60 and 68% yields, respectively. Both Schiff bases and the two trinuclear complexes were characterized by elemental (CHN) analysis, mass spectrometric, various spectroscopic (IR, UV-Vis and 1H NMR) and cyclic voltammetric measurements. Molecular structures of 2, 3and 4 were determined by single crystal X-ray diffraction studies. The cyclopentadienide rings in the ferrocene moieties are essentially in eclipsed conformation in all three structures. Deprotonated Schiff base ligands in each complex (Fcah in 3 and Fcbh in 4) act as five-membered chelate ring forming azomethine-N and amidate-O donors and assemble a square-planar trans-N ₂O ₂ coordination environment around the nickel centre. The redox active 1–4 exhibit an iron centred redox couple in the potential range 0.23–0.50 V (vs. Ag/AgCl).

    • One-dimensional manganese(III) and iron(III) coordination polymers assembled by N2O2-donor Schiff bases and 4,4Ꞌ-bipyridine: syntheses, structures and properties


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      Reactions of Mn(ClO4)2.6H2O and Fe(ClO4)3.6H2O with the tetradentate N2O2-donor Schiffbases N,NꞋ-bis(salicylidene)-ortho-phenylenediamine and N,NꞋ-bis(salicylidene)ethylenediamine (H2salophenand H2salen, where 2 Hs represent the two dissociable phenolic protons), respectively and the bridging ligand4,4Ꞌ-bipyridine (bipy) in presence of triethyl amine in methanol under ambient conditions produce onedimensional coordination polymers {[Mn(salophen)(μ-bipy)]ClO4}n (1) and {[Fe(salen)(μ-bipy)]ClO4}n (2)in ~60% yields. Both complexes have been characterized by elemental analysis and spectroscopic (IR andDR) measurements. The linear polymeric structures of 1 and 2 have been confirmed by single-crystal X-raycrystallography. The metal centres in these polymers are in distorted octahedral N4O2 coordination spheres.Each of the two dibasic tetradentate ligands (salophen2- and salen2-) forms an ONNO square-plane aroundthe metal centre, while the two axial coordination sites are occupied by N-atoms of the two bridging bipyligands. Variable temperature magnetic susceptibility measurements reveal the high-spin configuration ofmanganese(III) and iron(III) and Curie paramagnetic behaviour of each of the two coordination polymers.

      Facile one-pot syntheses of two new one-dimensional coordination polymers {[Mn(salophen)(μ-bipy)]ClO4}n and {[Fe(salen)(μ-bipy)]ClO4}n have been described. Both polymers were characterised by elemental analyses and solid state spectroscopic and cryomagnetic measurements. Linear chain-like structures of the high-spin Mn(III) and Fe(III) containing Curie paramagnetic polymers were confirmed by single crystal X-ray crystallography.

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