Crystal engineering of coordination polymers using 4,4′-bipyridine as a bond between transition metal atoms

Three new pseudohalide bridged dinuclear Zn(II) Schiff base complexes: Synthesis, crystal structures and fluorescence studies

Zinc complexes of the antibacterial drug oxolinic acid: structure and DNA-binding properties.

The stability of hydrocarbon ion exchange membranes is one of the critical issues for a flow battery. However, the degradation mechanism of ion exchange membranes has been rarely investigated especially for anion exchange membranes. Here, the degradation mechanism of polysulfone based anion exchange membranes, carrying pyridine ion exchange groups, under vanadium flow battery (VFB) medium was investigated in detail. We find that sp(2) hybrid orbital interactions between pyridinic-nitrogen in 4,4'-bipyridine and benzylic carbon disrupt the charge state balance of pristine chloromethylated polysulfone. This difference in electronegativity inversely induces an electrophilic carbon center in the benzene ring, which can be attacked by the lone pair electron on the vanadium(V) oxygen species, further leading to the degradation of polymer backbone, while leaving the 4,4'-bipyridine ion exchange groups stable. This work represents a step toward design and construction of alternative type of chemically stable hydrocarbon ion exchange membranes for VFB.

Mechanism of Polysulfone-Based Anion Exchange Membranes Degradation in Vanadium Flow Battery

Anion exchange membranes (AEMs) with excellent stability and high ion conductivity are fabricated via the formation of internal cross linking networks. The internal crosslinking networks are constructed by reacting 4,4'-bipyridine with chloromethylated polysulfone. The bipyridine group simultaneously functions as ionic conductor and cross linker in this system. The performance of the membrane is tuned via controlling the 4,4'-bipyridine content in the casting solution. The prepared membranes demonstrate excellent chemical stability and high ion conductivity under acidic conditions. As a consequence, the membranes show very promising performance for vanadium flow battery application, exhibiting a Coulombic efficiency of 99.2% and an energy efficiency of 81.8% at a current density of 140 mA cm(-2). The battery that is assembled with the prepared membrane shows a stable battery performance over more than 1600 cycles, which is by far the longest cycle life reported. These results indicate that the AEMs with internal crosslinking structures are promising candidates for battery systems and even for fuel cells.

Highly Stable Anion Exchange Membranes with Internal Cross-Linking Networks

Synthesis, characterization and structural studies of mono- and polynuclear complexes of zinc(II) with 1,10-phenanthroline, 2,2′-bipyridine and 4,4′-bipyridine

Thermally induced electron-transfer reactions of heterometallic dinuclear complexes in the solid state

Double complex salts containing cationic CuII having cyclic ligand piperazine (pipz), N-methylpiperazine (mpipz) and N,N′-dimethylpiperazine (dmpipz) and hexacyanoferrate(III) ion have been synthesized and characterized by elemental analyses, i.r. and electronic spectra, and magnetic moment measurements. Mossbauer spectra at room temperature and at 80 K, were recorded in order to evaluate the metal-metal charge transfer and the impact of the cyclic ligand present in cationic moiety of the double complex salt upon the Mossbauer spectra of the hexacyanoferrate(III) ion. Evidence for metal-metal charge transfer is supported by electronic spectra and magnetic susceptibilities. Variable temperature e.p.r. spectra were recorded in order to determine the distortion of crystal system. Thermally induced stereochemical studies have been carried out with the help of i.r. spectral data. Kinetics of thermochemical reactions have also been studied. Activation energies (Einfasup*) and inception temperatures for the thermochemical reactions show the order of stability of the double complex salts follows the trend: dmpipz > mpipz > pipz, which indicates that the + I effect is more pronounced than steric effect.

Solid state Mössbauer, e.p.r., magnetic properties and thermally induced stereochemical studies on double complex salts of cyclic diamine containing cationic copper(II) complexes and a hexacyanoferrate(III) anion

[LCu{μ-(OH)2(C2O2)}CuL](ClO4)2, (HL = N,N-dimethyl N-propylsalicylald-imine) was synthesised and its crystal structure was determined. C26H36CI2Cu2N4O14, triclinic space group P1̅ with a = 9.288(9), b = 10.016(11), c = 10.09(2) Å and a = 101.05(11), β = 108.22(10), γ = 110.22(10)°, V = 787(2) Å3, Z = 2. Two copper(II) ions in a distorted square-planar coordination are bridged by an oxalic acid molecule to form dinuclear units. The copper(II) centres are separated by 5.2 Å and antiferromagnetically coupled (J = -478 cm-1), which follows from temperature-dependent magnetic susceptibility measurements in the range 12 to 300 K.

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Parimal Kundu

Papers

Synthesis, characterization and structural studies of mono- and polynuclear complexes of zinc(II) with 1,10-phenanthroline, 2,2′-bipyridine and 4,4′-bipyridine

Thermally induced electron-transfer reactions of heterometallic dinuclear complexes in the solid state

Solid state Mössbauer, e.p.r., magnetic properties and thermally induced stereochemical studies on double complex salts of cyclic diamine containing cationic copper(II) complexes and a hexacyanoferrate(III) anion

Structure and magnetic properties of an oxalic acid bridged dinuclear copper(ii) complex

Thermally induced electron transfer reaction of heterometallic dinuclear complex in the solid state