Bipy Complex Research Articles

Mechanochemical Activation of Superradiance in Paramagnetic Polymer Composites.

The review examines the effect of radio-frequency superradiance during pulsed mechanochemical activation of polymer composites under high pressure. Mechanochemical activation is implemented in three modes: (a) rheological explosion of polymer composite under rapid uniaxial compression, when an elastic wave pulse occurs in a polymer composite sample and implements the physico-chemical transformations leading to the occurrence of a superradiance pulse; (b) parametric mode, when an elastic wave pulse is introduced from the outside through a waveguide into a composite sample; (c) the mode of rapid pressure release, which also leads to the occurrence of a superradiance pulse. Paramagnetic polymer composites-namely polystyrene-binuclear clusters Co(QH)2-O-Co(QH)2 or Mn(QH)2-O-Mn(QH)2, where QH is a ligand based on QH2-3,6-di-tert-butylpyrocatechin)-are considered as objects implementing such processes. These binuclear clusters exhibit the Dzyaloshinskii-Moriya effect, and polymer composites based on them exhibit multiferroic properties. A composite of a molecular magnet in polystyrene matrix (Eu(III)(SQ)3·bipy complex with four unpaired electrons on Eu(III) and on SQ ligands; SQ is 3,6-di-tert-butylquinolate paramagnetic ligand) is also considered. The binuclear clusters and europium complexes form 2D nano-objects in the polymer matrix with a diameter of 50-100 nm and a thickness of ~ 1-2 nm. The review considers the formalisms of Dicke, Lorentz, Landau-Lifshitz-Blombergen and Havriliak-Negami equations, which make it possible to conduct a time-frequency analysis of these processes, to obtain data on the relaxation processes of spin and charge density in objects responsible for the process of radio-frequency superradiation. It is also shown that the analysis of electron spin resonance data allows us to provide a probable quantum chemical scheme for the implementation of the radio-frequency superradiance process. The phenomenon of superradiation has a great deal of potential in such areas as energy-saving technologies, wireless power transmission and storage devices. The technique of studying fast mechanochemical processes considered in the review allows us to investigate the mechanisms of interaction of magnetic and electrical subsystems in multiferroics and molecular magnets, which expands the scientific base for the creation of new functional materials and enables the solving of related problems of condensed matter physics.

Copper(II) complexes with 4-(diethylamino)salicylaldehyde and α-diimines: Anticancer, antioxidant, antigenotoxic effects and interaction with DNA and albumins

In this article, cytotoxicity, the mechanisms of cytotoxic activity, genotoxicity, and interaction with DNA and proteins, of two Cu(II) complexes with a salicylaldehyde derivative (4-(diethylamino)salicylaldehyde) and α-diimine (2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen)) are reported. Both Cu(II) complexes performed cytotoxic effects against all tested malignant cell lines. Complexes exerted highest cytotoxicity against HeLa and A375 malignant cell lines. The cytotoxic activity of Cu(II) complex with phen as a α-diimine co-ligand was significantly higher in comparison with cytotoxic activity of Cu(II) complex with bipy. Pretreatment with specific inhibitors of caspase-3, caspase-8 or caspase-9, in order to clear up the mode of cell death triggered by two Cu(II) complexes in HeLa cells, indicated the ability of these complexes to induce apoptosis through activation of target caspases. Cu(II)-phen complex exhibited significant antioxidant activity compared with Cu(II)-bipy complex, and showed a better effect on reducing intracellular ROS levels in HeLa cells. Tested complexes did not display genotoxic potential in human peripheral blood leucocytes, but exhibited an antigenotoxic effect in post-treatment, after H2O2 exposure. The study of the in vitro biological properties regarding their affinity towards CT (calf-thymus) DNA and serum albumins showed that the compounds can intercalate to CT DNA, and bind reversibly and tightly to the albumins. Molecular docking studies of the ability of compounds to bind to biomacromolecules are consistent with in vitro studies.

Syntheses, crystal structures, and optical properties of polymeric iodoargentates containing transition metal-complexes with aromatic ligands

Six new iodoargentates [Mn(2,2′-bipy)2(DMSO)2]Ag5I7 (1), [Mn(2,2′-bipy)2(DMF)2]Ag5I7 (2), [Zn(2,2′-bipy)2(DMF)2]Ag5I7 (3), [{Cd(2,2′-bipy)2}2(μ4-Ag2I6)] (4), [{Zn(DMF)2(H2O)2}(4,4′-bipy)1.5]Ag5I7·2DMF (5) and [Zn(4,4′-bipy)2(DMSO)2(H2O)2]Ag10I12·2DMSO·2H2O (6) (2,2′-bipy = 2,2′-bipyridine; 4,4′-bipy = 4,4′-bipyridine; DMF = N,N'-dimethylformamide; DMSO = dimethylsulfoxide) were prepared using transition metal complex cations as counter ions. The charge balance TM2+-2,2′-bipy (TM = Mn, Zn) complex cations modified by small ligands via solvating in different polar solvents lead to formation of γ-[Ag5I72−]n chains in compounds 1–3, while the [Cd(2,2′-bipy)2]2+ cation affords a binuclear neutral complex 4 which contains a novel tetradentate μ-Ag2I6 ligand. The solvated Zn2+-4,4′-bipy complex cation results β-[Ag5I72−]n and [Ag10I12]2– chain-like anions in 5 and 6, respectively. All the polymeric γ-[Ag5I72−]n, β-[Ag5I72−]n, μ-Ag2I6 and [Ag10I12]2– units are formed by the primary tetrahedral AgI4 units via corner- or edge-sharing. Compounds 1–6 show well-defined absorption edges with band gaps in the range of 2.68 to 2.86 eV at room temperature. Compounds 2 and 5 display higher catalytic activities than 4 in the photodegradation of organic dye CV. All ∙O2−, ·OH and h+ reactive species play an important role in the photodegradation of CV over compound 2, while ·OH are the main reactive species in the photocatalytic reaction using compound 5 as catalyst.

Synthesis and structural characterization of two novel copper(II) Schiff base complexes and their water-containing supramolecular structures

Two novel copper(II) complexes, Cu2L2(bipy) and Cu2L2(H2O)4·3H2O of Schiff base ligands derived from the condensation of L-tert-leucine and L-isoleucine with 2,4-dihydroxybenzal­dehyde, are synthesized and characterized by single crystal X-ray diffraction. Compounds crystallize in the orthorhombic crystal system. The Cu2L2(bipy) complex has a distorted square planar geometry with an N2O2 coordination environment. Water is contained in supra­molecular network pores. On the other hand, in the Cu2L2(H2O)4·3H2O complex, both copper atoms adopt a five-coordinated distorted square-pyramidal geometry with an NO4 coordination environment. and guest water molecules form a 1-dimensional water chain. Both complexes build a two-dimensional supramolecular network.

Lewis Acid Catalyzed Friedel–Crafts Alkylation of Indoles and Other­ Electron-Rich Aromatic Compounds with Ethyl 2-(Diethoxyphosphoryl)acrylate and Tetraethyl Ethene-1,1-diylbis(phosphonate)

Friedel–Crafts alkylation of indoles and other electron-rich aromatic compounds with ethyl 2-(diethoxyphosphoryl)acrylate and tetraethyl ethene-1,1-diylbis(phosphonate) was carried out in the presence of 5 mol% Cu(ClO4)2·6H2O/2,2′-Bipy complex as a catalyst in acetonitrile at room temperature to afford a broad series of heteroaryl- and aryl-substituted 2-(diethoxyphosphoryl)propionates and ethyl-1,1-diylbis(phosphonates) in 58–96% yield.

Highly efficient and recyclable magnetic nanoparticles-supported gold(III)-bipy catalyst for oxidative α-cyanation of tertiary amines

Oxidative α-cyanation of tertiary amines with trimethylsilyl cyanide was achieved by using a magnetic nanoparticles-supported gold(III)-bipy complex as catalyst to afford the corresponding α-aminonitriles in good to excellent yields in the presence of tert-butyl hydroperoxide under acid-free conditions. The new heterogeneous gold catalyst can easily be separated from the reaction mixture by using an external magnet and can be recycled for at least 10 times without any loss of activity.

Ruthenium-8-quinolinethiolate-phenylterpyridine versus ruthenium-bipyridine-phenyl-terpyridine complexes as homogeneous water and high temperature stable hydrogenation catalysts for biomass-derived substrates

[(4′-Ph-terpy)(bipy)Ru(L)](OTf)n and [(4′-Ph-terpy)(quS)Ru(L)](OTf)n (n=0 or 1 depending on the charge of L, L=labile ligand, e.g., H2O, CH3CN or OTf, bipy=2,2′-bipyridine, quS=quinoline-8-thiolate) have been evaluated as catalysts for the hydrogenation of the biomass-derivable C6-substrates 2,5-dimethylfuran (obtainable from 5-hydroxymethylfurfural) and 2,5-hexanedione (the hydrolysis product of 2,5-dimethylfuran). Operating in aqueous acidic medium at T=175–225°C the bipy complex is only marginally active, while the quinoline-8-thiolate complex realizes yields of hydrogenated products up to 97% starting from 2,5-hexanedione and up to 66% starting from 2,5-dimethylfuran. The catalyst can also convert the 5-HMF derived acetone 4-(5-methyl-2-furanyl)-3-buten-2-one into 2,5,8-nonatriol, a potentially valuable cross-linker for polymer formulations. On the basis of DFT calculations, the higher activity of the quinoline-8-thiolate complex is proposed to be rooted in a metal–ligand bifunctional mechanism for the heterolytic activation and transfer of dihydrogen to the carbonyl substrate with the hydride-thiol complex [(4′-Ph-terpy)(quSH)Ru(H)]+ as the active catalyst.

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Anion radicals of a series of aromatic compounds (C6H5CN, C6H5COOEt, anthracene, 9,10-dimethyl-, 9,10-diphenyl- and 9-phenylanthracene, pyrene and naphthalene) react with trialkyl chlorosilanes R1R2R3SiCl (R1-3=Me, Et; R1,2=Me, R3=t-Bu) in multiple ways, following classical bimolecular schemes. The ratio of one-electron transfer (ET) to a two-electron process (SN2-like nucleophilic attack of the reduced form of mediator on the chlorosilane, with k2≅102-108M−1s−1) is inversely related to the steric availability of Si for nucleophilic displacement reactions. The nucleophilic substitution pathway mainly results in mono- and disilylated aromatic products. Paralleling the electrochemical data with DFT calculations, the role of silicophilic solvent (DMF) in SN process was shown to be quite complex because of its involvement into coordination extension at silicon, dynamically modifying energetics of the process along the reaction coordinate. Although 2,2'-bipyridine also forms delocalized persistent anion radicals, they do not induce neither ET nor SN reactions in the same manner as aromatic mediators. Silicophilicity of 2,2'-bipyridine being superior to that of DMF, a R3SiCl·bipy complex of hypercoordinated silicon with electroactive ligand was formed instead, whose reduction requires about 1V less negative potentials than bipyridine itself.

Polyethylene Glycol-Mediated Kinetic Study of Nitrodecarboxylation of α,β-Unsaturated Acids by Blau's Fe(III) Bipy Complex

A kinetic and mechanistic study of nitro decarboxylation of α,β-unsaturated acids (USA) has been taken up by Blau's yellow complex [Fe(III) nitrate–Bipy] in polyethylene glycol (PEG)–acetonitrile media. Kinetics of the reactions indicated a rate law: rate = ab[Fe (III)][Bipy][USA]/(1 + b [Bipy]), that represents the Michaelis–Menten type mechanism. Reaction rates are significantly influenced by the structural variation and concentration of PEG. The mechanism of PEG-mediated reaction was explained through the formation of more active [PEG bound Fe(III) nitrate–Bipy species] than [Fe (III) nitrate–Bipy] itself. Formation of [PEG bound Fe(III) nitrate–Bipy species] could be due to the interaction of polyoxyethylene glycolate moiety with [Fe (III) nitrate–Bipy species] in the lines of nonionic micellar interactions.

Choice of suitable micellar catalyst for 2,2′-bipyridine-promoted chromic acid oxidation of glycerol to glyceraldehyde in aqueous media at room temperature

The micellar catalyzed 2,2′-bipyridine (bipy)-promoted oxidation of glycerol to glyceraldehyde by chromic acid is investigated under the criteria [glycerol]T ≫ [Cr(VI)]T at 30 °C. The critical micellar concentrations values of the three representative surfactants, N-cetylpyridinium chloride (CPC), sodium dodecyl sulphate (SDS), and TX-100, are determined by conductometric and spectrophotometric methods. The oxidized product glyceraldehyde is identified by 2,4-DNP test and FTIR spectral measurement. The pseudo-first-order rate constants (k obs, s−1) are calculated from the slope of plots of ln(A 450) versus time (t) which are linear. From these plots, the kinetic parameter k eff values are calculated and the k eff value of SDS-catalyzed bipy-promoted reaction path was found to be highest among all the combinations. In the bipy-promoted oxidation path, Cr(VI)–bipy complex is the main active oxidant which undergoes attack by the substrate to form the product. The active oxidant Cr(VI)–bipy complex reacts with glycerol to form a ternary complex which undergoes redox decomposition in a rate-limiting step. Here, the anionic surfactant SDS and the neutral surfactant TX-100 both catalyze the reaction in the presence of bipy, whereas the cationic surfactant CPC and neutral surfactant TX-100 inhibit the reaction in the absence of bipy. SDS is found to be the most suitable micellar catalyst for the bipy-promoted chromic acid oxidation of glycerol.

Insight into PdCl2(bipy) Complex as an Efficient Catalyst for Heck Reaction and Kinetic Investigations in Homogeneous Medium

Insight into PdCl₂(bipy) Complex as an Efficient Catalyst for Heck Reaction and Kinetic Investigations in Homogeneous Medium

Slow Self‐Assembly Favors Hysteresis above Room Temperature for an Iron(II) 1D‐Chain Spin‐Crossover Complex

AbstractThe X‐ray structures and magnetic properties of three new iron(II) coordination polymers with the general formula [FeL1(Lax)]n are presented. L1 is the tetradentate N2O22– Schiff‐base‐like ligand (E,E)‐{dimethyl‐2,2′‐[1,2‐phenylenebis(iminomethylidyne)]bis(3‐oxobutanato)(2–)‐N,N′,O3,O3′}. For the axial coordination, 4,4′‐bipyridine (bipy), 1,2‐bis(4‐pyridyl)ethane (bpea), and 1,2‐bis(4‐pyridyl)ethene (bpee) were used. Spin‐transition behavior was observed for the bpea and the bipy complexes. In both cases, two different polymorphs were isolated, showing different magnetic properties. In the case of the bipy complex 1, different preparation methods were tested to elucidate which conditions favor one polymorph over another. It appears that a slow precipitation of the coordination polymer favors a cooperative spin transition above room temperature, whereas a fast precipitation results in a gradual spin transition at lower temperatures. In the case of the bpea complex, an incomplete spin transition is observed, which can be explained by the crystal packing.

Mechanistic Studies on the Gas-Phase Dehydrogenation of Alkanes at Cyclometalated Platinum Complexes

In the ion/molecule reactions of the cyclometalated platinum complexes [Pt(L-H)](+) (L=2,2'-bipyridine (bipy), 2-phenylpyridine (phpy), and 7,8-benzoquinoline (bq)) with linear and branched alkanes C(n)H(2n+2) (n=2-4), the main reaction channels correspond to the eliminations of dihydrogen and the respective alkenes in varying ratios. For all three couples [Pt(L-H)](+)/C(2)H(6), loss of C(2)H(4) dominates clearly over H(2) elimination; however, the mechanisms significantly differs for the reactions of the "rollover"-cyclometalated bipy complex and the classically cyclometalated phpy and bq complexes. While double hydrogen-atom transfer from C(2)H(6) to [Pt(bipy-H)](+), followed by ring rotation, gives rise to the formation of [Pt(H)(bipy)](+), for the phpy and bq complexes [Pt(L-H)](+), the cyclometalated motif is conserved; rather, according to DFT calculations, formation of [Pt(L-H)(H(2))](+) as the ionic product accounts for C(2)H(4) liberation. In the latter process, [Pt(L-H)(H(2))(C(2)H(4))](+) (that carries H(2) trans to the nitrogen atom of the heterocyclic ligand) serves, according to DFT calculation, as a precursor from which, due to the electronic peculiarities of the cyclometalated ligand, C(2)H(4) rather than H(2) is ejected. For both product-ion types, [Pt(H)(bipy)](+) and [Pt(L-H)(H(2))](+) (L=phpy, bq), H(2) loss to close a catalytic dehydrogenation cycle is feasible. In the reactions of [Pt(bipy-H)](+) with the higher alkanes C(n)H(2n+2) (n=3, 4), H(2) elimination dominates over alkene formation; most probably, this observation is a consequence of the generation of allyl complexes, such as [Pt(C(3)H(5))(bipy)](+). In the reactions of [Pt(L-H)](+) (L=phpy, bq) with propane and n-butane, the losses of the alkenes and dihydrogen are of comparable intensities. While in the reactions of "rollover"-cyclometalated [Pt(bipy-H)](+) with C(n)H(2n+2) (n=2-4) less than 15 % of the generated product ions are formed by C-C bond-cleavage processes, this value is about 60 % for the reaction with neo-pentane. The result that C-C bond cleavage gains in importance for this substrate is a consequence of the fact that 1,2-elimination of two hydrogen atoms is no option; this observation may suggest that in the reactions with the smaller alkanes, 1,1- and 1,3-elimination pathways are only of minor importance.

Hydrogen-bond networks in the binary complexes of trigonal molecules with 4,4′-bipyridine

A 1:1 binary salt and a cocrystal of two chemically different trigonal symmetric donor molecules, 2,4,6-trimethyl-1,3,5-benzenetricarboxylic acid (MTAH3) and 2,4,6-tris(4-hydroxyphenoxy)-1,3,5-triazine (HPT) with 4,4′-bipyridine (bipy) have been synthesized and the crystal structures have been studied. The MTAH3·bipy salt shows an unprecedented parallel interpenetrated 3D bookshelf type of structure aided by C(8) type O–H⋯O and acid⋯pyridine O–H⋯N interactions. The HPT·bipy complex has a 2D → 3D parallel polycatenated pcu net aided by the usual hydroxy⋯pyridine synthon and supported by a C–H⋯O interaction. Both the complexes exhibit the formation of 3D structures from trigonal donors, contrary to the fact that trigonal species generally are being considered to be candidates for construction of 2D networks.

Kinetics and mechanism of 2,2′-bipyridine-catalyzed chromium(VI) oxidation of propan-2-ol in the presence and absence of surfactants

Under kinetic conditions, monomeric Cr(VI) has been found kinetically active in the absence of bipy while in the bipy-catalyzed path, Cr(VI)-bipy complex has been suggested as the active oxidant. The uncatalyzed path shows the second-order dependence on [H+] while the bipy-catalyzed path shows the first-order dependence on [H+]. Both the uncatalyzed and bipy-catalyzed paths show the first-order dependence on [propan-2-ol]T and [Cr(VI)]T. The bipy-catalyzed path is the first order in [bipy]T. Cetylpyridiniumchloride inhibits the reactions while sodium dodecyl sulfate catalyzes the reactions in the presence and in the absence of bipy.

Micellar catalysis of chromium(VI) oxidation of ethane-1,2-diol in the presence and absence of 2,2′-bipyridine in aqueous acid media

The kinetics and mechanism of the Cr(VI) oxidation of ethane-1,2-diol in the presence and absence of 2,2′-bipyridine (bipy) in aqueous acid media were studied under the conditions [ethane-1,2-diol]T ≫ [Cr(VI)]T. Under the kinetic conditions, monomeric Cr(VI) was found to be kinetically active in the absence of bipy, whereas in the bipy-catalyzed path the Cr(VI)-bipy complex was the active oxidant. In this path, the Cr(VI)-bipy complex undergoes nucleophilic attack by the substrate to form a ternary complex which subsequently undergoes redox decomposition (through 2e transfer) leading to hydroxyethanol and the Cr(IV)-bipy complex. The Cr(IV)-bipy complex then participates further in oxidation of organic substrate, ultimately converted into inert Cr(III)-bipy complex. The uncatalyzed path shows a second-order dependence on [H+], while the bipy-catalyzed path shows a first-order dependence on [H+]. Both the uncatalyzed and bipy-catalyzed paths show first-order dependence on [ethane-1,2-diol]T and on [Cr(VI)]T. The bipy-catalyzed path is first-order in [bipy]T. All these patterns remain unaltered in the presence of externally added surfactants. The effects of a cationic surfactant, N-cetylpyridinium chloride (CPC), and an anionic surfactant, sodium dodecyl sulfate (SDS), on both the uncatalyzed and bipy-catalyzed paths were studied. CPC inhibits both the uncatalyzed and bipy-catalyzed paths, whereas SDS catalyzes the reactions. The observed micellar effects are explained by considering a distribution pattern of the reactants between the micellar and aqueous phases.

Organic–inorganic hybrid chains and layers constructed from copper-amine cations and early transition metal (Nb, Mo) oxyfluoride anions

Under hydrothermal conditions in HF-containing media, the combination of early (Nb(5+), Mo(6+)) and late (Cu(2+)) transition metals with four different organic amine ligands yields eight novel hybrid compounds with chain and layer structures. The eight new compounds were synthesised from a systematic series of reactions and can be subdivided into four pairs, the topologies of which are essentially unique to each ligand, containing in each case a Cu-based cationic species, but alternately either [MoO(2)F(4)](2-) or [NbOF(5)](2-), in an isomorphous manner, as the anionic moiety. The overall structures of theses materials reflect the influences of the organo amine ligands. [Cu(C(2)H(4)N(4))(2)][MoO(2)F(4)].H(2)O () and [Cu(C(2)H(4)N(4))(2)][NbOF(5)].H(2)O () exhibit an infinite copper fluoride amine chain, while the anionic moieties act as 'decoration' to the chain. [Cu(C(3)H(4)N(2))(4)][MoO(2)F(4)] () and [Cu(C(3)H(4)N(2))(4)][NbOF(5)] () form infinite 1D chains with alternating cationic and anionic units. [Cu(2)F(2)(C(10)H(9)N(3))(2)][MoO(2)F(4)] () and [Cu(2)F(2)(C(10)H(9)N(3))(2)] [NbOF(5)] () contain a dimeric copper fluoride complex, bridged through anions to form a 1D infinite chain. [Cu(C(10)H(8)N(2))(2)(H(2)O)(2)][MoO(2)F(4)] () and [Cu(C(10)H(8)N(2))(2)(H(2)O)(2)][NbOF(5)] () contain a 2D interpenetrated network formed from the copper-4,4'-bipy complex, with open channels which accommodate the oxyfluoride anions via hydrogen bond interactions.

A Facile Copper-Catalyzed In Situ Reaction Generating a Novel Organic Ligand from Citrazinic Acid

Reaction of citrazinic acid with copper nitrate and 2,2′-bipy complex in alkaline aqueous solution gives a complex containing complicated organic ligand derived from the organic reactant. The experimental result demonstrates clearly that copperII plays an important role in this reaction.

Reactions of heteroaromatic chromophores with lanthanide complexes of p-sulfonatothiacalix[4]arene

The conditions for the formation of heteroleptic complexes of a lanthanide(iii) ion (Ln = La, Gd, and Tb) with p-sulfonatothiacalix[4]arene and a heteroaromatic chromophore in water were found using X-ray diffraction analysis, pH-metry, 1H NMR and UV—Vis spectroscopy, and nuclear magnetic relaxation. In the resulting complexes, the heteroaromatic chromophore is in the calix[4]arene cavity and the lanthanide ion is coordinated by the electron-donating groups of the upper or lower calix[4]arene rim. Emission spectroscopic studies revealed changed emission properties of TbIII ions in the terbium(iii)—p-sulfonatothiacalix[4]arene—bipy complex.

Cyclic voltammetric studies of oxovanadium(IV) complexes derived from 2,2'-bipyridine and 1,10-phenanthroline in nonaqueous media

The electrochemical behaviour of oxovanadium(iv) complexes, [VO(bipy) 1 ] 2+ and [VO(phen) 2 ] 2+ (where, bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline) have been examined in DMSO and DMF with 0.1 M TBAP using cyclic voltammetry at a Pt working electrode. It is found that [VO(bipy) 2 ] 2+ and [VO(phen) 2 ] 2+ complexes are irreversibly oxidized (V0 2+/3+ ) with anodic peak potential, E pa1 ≃ 1,10 V vs SCE at 200 mV s -1 . The initial reduction of these complexes in DMSO and DMF media revealed two irreversible cathodic peaks with E pc1 = -0.96 to -1.13 V and E pc2 = -1.17 to -1.30 V vs SCE. It should be mentioned that dependence of I pa1 or I pc1 on v 1/2 is linear without any intercept. This suggests that the redox processes a 1 and c 1 are diffusion controlled. It is also observed that the oxidation of bipy complex is easier while reduction is difficult in comparison to phen complex in a given medium.