Synthesis,electrolyte properties and solar cell performance of hyperbranched poly(aryl-ether-urea)s

Hyperbranched poly(aryl-ether-urea)s with phenyl, N,N-dimethylamino ethyl and polyethylene oxide end-groups linked through urethane group – HBPEU-1, HBPEU-2 and HBPEU-3 respectively – were synthesized from an AB₂-type blocked isocyanate monomer and characterized by FT-IR, ¹H-NMR, SEC-MALLS, TGA and DSC techniques. The molecular weight of the polymers were found to be ranged from 4.9 × 10³ ? 1.96 × 10⁴ g/mol. The TGA results showed that the polymers decompose between 175°C – 220°C. In the DSC curves, HBPEU-1 and HBPEU-3 showed T_g at 160°C and 53°C respectively, whereas HBPEU-2 did not showed clear T_g. All the three polymers were converted into polymer electrolytes by doping with LiI/I₂. The doped polymers showed remarkably high ionic conductivity, up to 222 – 277 times compared to the un-doped polymers and the highest conductivity was observed with doped HBPEU-2. The TiO₂ based dye-sensitized solar cells (DSSCs) were fabricated using the doped polymer electrolytes and their performance was tested; HBPEU-2 showed good performance by yielding energy conversion efficiency (η) of 4.5%.     

Synthesis and spectral studies on Ni(II) complexes involving N-furfuryl-N-substituted benzyldithiocarbamates and PPh3: Anagostic and C–H…π(chelate) interactions in (N-furfuryl-N-(4-fluorobenzyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Twelve new nickel(II) complexes of functionalized dithiocarabamates [Ni(S₂CNRR')₂](1-6) and [Ni(S₂CNRR')(NCS)(PPh₃)](7-12) [where R=furfuryl; R'=2-hydroxy benzyl (1,7), 3-hydroxy benzyl (2,8), 4-hydroxy benzyl (3,9), 4-methoxy benzyl (4,10), 4-fluoro benzyl (5,11), 4-chloro benzyl (6,12)] have been prepared and characterized by elemental analysis, IR, UV-Vis and NMR (¹H and ¹³C) spectroscopy. IR spectra of the complexes support the bidentate coordination of dithiocarbamate ligands. Electronic spectral studies on complexes 1-12 indicate square planar geometry around the nickel(II) central atom. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for heteroleptic complex (7-12) compared to homoleptic complexes (1-6) is due to the effect of PPh₃ on the mesomeric drift of electron density toward nickel through thioureide C-N bond. Single crystal X-ray structural analysis of complex 11 confirms that the coordination geometry about the Ni(II) is distorted square planar. A rare intramolecular anagostic interaction C–H^…Ni [Ni???H=2.804 Å] is observed. The packing of complex 11 is stabilized by non-conventional C–H^…S, C–H?F and C–H?π(chelate, NiS₂C) bonding interactions.     

Synthesis of oxalate doped polyaniline and its corrosion protection performance

It is known that dopants present in polyaniline (PANI) play an important role in corrosion protection of mild steel since the dopant ions form a secondary layer with iron. Since oxalate ions form a stable iron oxalate layer on mild steel, a study has been made on the corrosion protection performance of steel by vinyl coating containing oxalate doped PANI in acid and neutral media. Electrochemical impedance spectroscopy (EIS) studies have shown that the oxalate doped PANI is able to protect mild steel in sodium chloride solution since the impedance values are maintained at 10¹⁰ Ω cm² even after 100 days of exposure.     

Crystallographic and Computational Studies on N-Furfuryl-N-(3-Hydroxybenzyl)amine and N-Furfuryl-N-(4-Hydroxybenzyl)amine

Crystal structures of N-furfuryl-N-(3-hydroxybenzyl)amine (1) and N-furfuryl-N-(4-hydroxybenzyl)amine (2) are reported. The furyl ring is coplanar with the C–N–C plane in 1 and perpendicular to the C–N–C plane in 2. Intermolecular O–H ? N and C–H ? O hydrogen bonds stabilize the crystal structures and play a crucial role in crystal packing. In addition, the molecular geometry and molecular vibrations are calculated using the DFT/B3LYP method with the 6-31G(d,p) basis set and the calculated geometrical parameters are correlated with the corresponding experimental data. The obtained HOMO and LUMO energies are negative, indicating that the compounds are in the stable state. FT-IR spectra of compounds 1 and 2 are measured in order to elucidate the spectroscopic properties of the compounds in the spectral range 4000–500 cm^?1. The recorded FT-IR spectral measurements are further supported by spectral simulations.     

Influence of sol–gel derived lithium cobalt phosphate in alkaline rechargeable battery

A lithium cobalt phosphate (LiCoPO₄) cathode was synthesised by citric acid assisted sol?Cgel method and its electrochemical behaviour in alkaline secondary battery (using novel lithium hydroxide as the electrolyte) is reported. The sol?Cgel method using metal acetate precursors with citric acid as a chelating agent influenced the particle size and the homogeneity while yielding a single phase LiCoPO₄ at a considerably lower temperature and shortened heating time, compared to that of the conventional solid state reaction. The cyclic voltammogram of LiCoPO₄ showed a reversible redox process implying that de-intercalation and intercalation of lithium can occur in aqueous electrolyte. This was supported by X-ray diffraction (XRD) and Infra-red (IR) studies. The charge?Cdischarge performance of the Zn/LiCoPO₄ battery showed good capacity retention (after 25 cycles it delivered 90?% of its initial capacity). This enhanced capacity retention was attributed to the synergistic effect of particle homogeneity, reduced Li⁺ diffusion path and stability of the non-reactive aqueous electrolyte between the electrode and the electrolyte interface.     

Catalysis of cure reaction of ɛ-caprolactam-blocked polyisocyanate with diol using non-tin catalysts

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Catalysis of cure reaction of ?-caprolactam-blocked polyisocyanate with 1,4-butane diol in the presence of DABCO - a tertiary amine, tin(II) 2-ethylhexanoate and non-tin organometallics like bismuth neodecanoate, calcium(II) 2-ethylhexanoate and zinc(II) 2-ethylhexanoate was investigated. The activity of these catalysts was studied by the determination of cure-time (gel-time) and analysis of absolute molecular weight of cured polymers. Cure-time results indicated that all the non-tin organometallics act as catalysts; they were more active than DABCO and except bismuth neodecanoate, other two non-tin compounds were also found to be equally active or more active than tin(II) 2-ethylhexanoate. Within the three organometallics studied, zinc (II) 2-ethylhexanoate showed highest catalytic activity, it reduced the cure-time more than 50% compared to the uncatalysed reaction. In the case of bismuth neodecanoate catalysed reaction, it was found that the viscosity was build-up to a certain limit and then decreased; this catalyst assisted chain degradation was confirmed by the analysis of molecular weight of polymers as a function of time. Catalytically active new species was formed when mixing the solution of DABCO to the solution of zinc (II) 2-ethylhexanoate and this formation was confirmed using FT-IR and UV-visible spectroscopy, but this species not showed synergism.     

Radical‐Mediated Three‐Component Coupling of Alkenes

A tandem radical process involving conjugate addition to an activated alkene followed by allylation is reported. B‐Alkylcatecholboranes, easily available via hydroboration of the corresponding alkenes, were used to generate the initial radicals. These radicals add efficiently to electrophilic alkenes such as phenyl vinyl sulfone, N‐phenylmaleimide, and dialkyl fumarate. In the last step of this one‐pot process, the radical adducts react with the allylic sulfones. The whole process can be considered as a unique and selective coupling of three different alkenes.     

Piezoflurochromism and Aggregation Induced Emission Properties of 9, 10-bis (trisalkoxystyryl) Anthracene Derivatives

We report the synthesis of trisalkoxy substituted 9, 10-bis styrylanthracene derivatives (C8-ant and C12-ant) by Heck coupling with very good yield and their photophysical properties. Both C8-ant and C12-ant exhibit aggregation induced emission (AIE), mechnoflurochromism and thermochromism. Trisubstituted 9, 10-distyrylanthracene molecules having all the luminescent properties in a single molecule are first of its kind.     

Synthesis, DNA binding, antioxidant and cytotoxic activities of ruthenium(II) complexes of a Schiff base ligand

Three ruthenium(II) complexes, [Ru(CO)Cl(PPh₃)L], [Ru(CO)Cl(AsPh₃)L] and [Ru(CO)Cl(Py)L], were synthesized from the reactions of 2-(benzothiazol-2-yliminomethyl)-phenol (HL) with [RuHCl(CO)B(EPh₃)₂], where B = PPh₃, AsPh₃ or pyridine, and E = P or As. All the complexes have been characterized by physicochemical and spectroscopic methods. The structure of the free ligand HL was determined by single crystal X-ray diffraction. The binding of the free ligand and its complexes with CT-DNA was studied using electronic absorption spectroscopy. In addition, the free ligand and its complexes were subjected to antioxidant activity tests, which showed that they all possess significant scavenging effects against DPPH and OH radicals. The in vitro cytotoxicities of the compounds were assessed using tumor (HeLa and MCF-7) cell lines.