Sudipta Dalai

Azido bridged two new ferromagnetic Cu(II) chains: synthesis, structure and magnetic behaviour

Two new polynuclear copper(II) complexes, derived from the end-to-end azido bridging ligand and two tridentate (NNN-donor) Schiff base ligands have been synthesised and their single crystal structures have been determined. They are single azido bridged chains, [Cu(L1)(μ-1,3-N 3 )] n (ClO 4 ) n ( 1 ) and [Cu(L2)(μ-1,3-N 3 )] n (ClO 4 ) n ( 2 ) where L1 and L2 are two different tridentate Schiff bases obtained from the condensation of pyridine-2-aldehyde with N, N, 2, 2-tetramethylpropane-1, 3-diamine and 1-dimethylamino-2-propylamine, respectively. Structural analyses reveal that each copper(II) centre in both the complexes are in square pyramidal geometry. The azido ligand is bridged in such a fashion that one of the nitrogens of the bridging azide is linked to equatorial of one copper(II) while the other in the axial of the neighbouring copper(II). Low temperature magnetic susceptibility data show weak intrachain ferromagnetic interaction through end-to-end azido pathway in both the complexes. The magnetic data are fitted to a high temperature series expansion for 1D system with S =1/2 local spin based on the Hamiltonian H =− J Σ S i S i+ 1 , giving the parameters J =2.69 cm −1 , g =2.10 for ( 1 ) and J =2.02 cm −1 , g =2.02 for ( 2 ).

A doubly end-to-end azido bridged 1D ferromagnetic chain

Abstract A doubly end-to-end (EE) azido bridged 1D ferromagnetic Cu(II) chain [Cu(L)2(N3)2] (1) [L=4-(dimethylamino)pyridine], representing the first observation of ferromagnetic interaction in doubly EE azido bridged chain has been synthesised and characterised by X-ray structure determination and low temperature magnetic susceptibility measurements.

Synthesis, crystal structure and magnetic properties of two new dicyanamide bridged 2D and 1D complexes of Mn(II)

Two new polymeric compounds, [Mn(dca)2(4CN-py)2]n (1) and [Mn(dca)2(bpe)]n (2) where dca = dicyanamide anion, 4CN-py = 4-cyanopyridine and bpe = 1,2-bis(4-pyridyl)ethane, have been synthesised and characterised by X-ray crystallography and low temperature magnetic study. Compound 1 consists of a two-dimensional network of octahedrally coordinated Mn(II) cations bridged by dicyanamide anions. In this compound, the Mn(II) cation is linked by four dca bridging ligands and two monodentate 4CN-py ligands. Compound 2 is an one-dimensional chain of Mn(II) bridged by dca as well as bpe. Each Mn(II) in the chain is octahedrally coordinated by four dca and two bpe ligands. Variable temperature magnetic susceptibility measurements in the temperature range 300–2 K reveal the existence of weak antiferromagnetic interactions in both complexes (J = −0.154 cm−1, g = 2.01 for 1 and J = −1.25 cm−1, g = 2.00 for 2).

The first metamagnetic one-dimensional molecular material with nickel(II) and end-to-end azido bridges

A novel single azido bridged one-dimensional Ni(II) chain, which represents the first metamagnetic one-dimensional metal–azido system with only end-to-end azido bridges, has been synthesised and characterised by a low temperature magnetic study.

Synthesis and X-ray structure of a new zinc(II) coordination polymer: interaction with DNA and double stranded RNA and elucidation of the molecular aspects of the binding to bovine serum albumin

A novel ligand bridged zinc(II) coordination polymer, [Zn(4-Me-5-CHOIm)2(HCOO)](ClO4) has been synthesized and characterized by single crystal X-ray diffraction studies. The structural analysis revealed that the complex exhibits two types of 2D network by weak and strong hydrogen bonds. Interestingly, an extended supramolecular layer network has been observed in the solid state structure through weak face-to-face π-stacking interactions. The interaction of the complex with calf thymus DNA (CT-DNA) and double stranded ribonucleic acid, polyinosinic·polycytidylic acid (poly(I)·poly(C)) has been explored by UV-Vis absorption, fluorescence displacement, circular dichroism (CD) spectral and isothermal titration calorimetric (ITC) methods. The spectral titration method revealed that the compound could interact with CT-DNA and RNA through partial intercalation with a binding affinity of an order of 105. ITC experiments indicate an exothermic reaction in both cases but RNA interaction is favored by positive entropy. On the other hand, the complex could quench the intrinsic fluorescence of BSA in a static quenching process with a quenching constant of the order of 104. A specific binding distance of 2.75 nm between Trp 212 (donor) and the complex (acceptor) was obtained from Forster resonance energy transfer studies (FRET). Competitive binding using site markers, warfarin and ibuprofen, having definite binding sites demonstrated that the complex binds to site I (subdomain IIA) on BSA. Circular dichroism (CD), synchronous fluorescence, and three-dimensional fluorescence spectroscopy experiments reveal that binding with the complex alters the BSA secondary structure by a reduction of the α-helical organization and increases the coiled structure and the ITC experiment indicates that the binding was enthalpy driven with a slight negative entropy effect.

Influences of amine‐terminated oligomers on glass fibre‐epoxy composite

Purpose – The purpose of this paper is to evaluate the mechanical properties of glass fibre reinforced epoxy composites modified with amine‐terminated poly (ethylene glycol) benzoate (ATPEGB) along with their thermal stability.Design/methodology/approach – ATPEGB prepared from poly (ethylene glycol) (PEG) of different molecular weights (200, 400, 600, 4,000 and 20,000) were used as modifiers for glass fibre epoxy composite here. For toughening, 12.5 parts per hundred grams (phr) of epoxy resin of each ATPEGB was added to epoxy and pre‐reacted with it. The impact, tensile and flexural strengths of modified and unmodified composite were characterised and compared for each ATPEGB.Findings – Modified resin displayed a significant improvement in fracture toughness with glass fibre over unmodified epoxy. The modification caused the formation of oligomer domains having relatively round shapes in the matrix. These oligomer domains led to improved strength and toughness due mainly to the “rubber toughening” effect...

Mechanical properties of modified epoxy: effect of chain length

Purpose – To evaluate the mechanical properties of cured epoxy modified with amine terminated poly (ethylene glycol) benzoate (ATPEGB) along with the comparison of results with change in chain length of ATPEGB.Design/methodology/approach – ATPEGB prepared from poly (ethylene glycol) (PEG) of different molecular weights (200, 400 and 600) were used as modifiers for epoxy resin here. For effective toughening, different compositions were made by adding various concentration of each ATPEGB to epoxy. The impact, adhesive, tensile and flexural strengths of modified and unmodified epoxy were characterised and compared for each ATPEGB.Findings – Modification of epoxy resin using each ATPEGB showed significant enhancement of mechanical strengths over unmodified epoxy. The modification caused a chemical linking between ATPEGB and resin which led not only to a phase separation but also to ensuring their intrinsically strong chemical bonds across the ATPEGB phase/resin matrix interface and this was the main cause to ...

A three component fully interlocked 3-D network: crystal structure and magnetic properties

A one-pot reaction of three different components [Cu(II), fumarate dianion and piperazine] leads to the self assembly of a magnetic molecular fully interlocked 3D structure with (4,4) nets formed by equal 2D sheets.

A novel class of interpenetrated 3-D network of a dimeric cupric-tetracarboxylate unit

The hydrothermal reaction of Cu(II), fumaric acid and 4,4′-bipyridine (bpy) in equimolar amounts at 160 °C resulted in a new type of two-fold interpenetrating 3-D coordination network composed of tetracarboxylate dicopper(II) units bridged by bipyridine spacers.

Three-Dimensional Silver(I)-Thiodiglycolate Coordination Polymer with Weak Ag–Ag Bond

Reaction of thiodiglycolic acid and silver nitrate under ultrasonic condition forms a 3D supramolecular framework of silver with composition [Ag2(tdga)]n (1). X-ray single crystal structure analysis reveals repetition of paddle wheel units in the network. A weak Ag–Ag bond is present in the complex. A new μ8-coordination mode of the thiodiglycolate ligand is identified. Photoluminescence and thermal characterization of the complex was examined.Graphical AbstractNovel 3D silver coordination polymer with Ag–Ag bond is synthesized using thiodiglycolic acid ligand and characterized by X-ray diffraction, IR, photoluminescence and TG analysis. The ligand displays a unique type of coordination.