Synthesis and characterizations of 3,3′-bis(diphenylphosphinoamine)-2,2′-bipyridine and 3,3′-bis(diphenylphosphinite)-2,2′-bipyridine and their chalcogenides

New bis(phosphinoamine) and bis(phosphinite) derivatives of 2,2′-bipyridine were prepared through a single step reaction of 3,3′-diamino-2,2′-bipyridine or 3,3′-dihydroxy-2,2′-bipyridine with diphenylchlorophosphine, respectively. Their P = E chalcogenides (E = O, S, Se) were also prepared. All the new compounds were characterized by elemental analysis, IR and NMR spectroscopies. The molecular structure of 3,3′-bis(diphenylthiophosphinite)-2,2′-bipyridine was elucidated by single-crystal X-ray crystallography.     

Effect of a carboxyl group on the chemiluminescent reaction of tris(2,2′-bipyridine)ruthenium(III) with aliphatic amines

The effect of a carboxyl group beside nitrogen of aliphatic amines on the tris(2,2′-bipyridine)ruthenium(III), Ru(bpy)₃³⁺, chemiluminescent reaction was examined. It has been shown that a carboxylate anion promotes the chemiluminescent reaction at a lower pH and then the aliphatic amines with this substituent can be sensitively detected compared with corresponding aliphatic amines without this substituent. Based on this finding, preliminary studies on simultaneous determination of 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid in human serum have been performed using isocratic reversed-phase ion-pair high-performance liquid chromatography (HPLC) with electrogenerated Ru(bpy)₃³⁺ chemiluminescent detection. The detection limits (signal-to-noise ratio of 3) with the proposed method were 3.0, 12, 2.7, 4.6, and 10 nM for 4-hydroxyproline, N-methylglycine, N-methylalanine, proline, and pipecolic acid, respectively.     

Facile design of poly(3,4-ethylenedioxythiophene)-tris(2,2′-bipyridine)ruthenium (II) composite film suitable for a three-dimensional light-harvesting system

It has been confirmed that octasulfonatocalix[8]arene (Calx-S8) and tris(2,2′-bipyridine)ruthenium (II) (Ru(bpy)₃²⁺) can form a stable host-guest complex in aqueous solution. The binding constant for 1:1 [Calx-S8⁸⁻·Ru(bpy)₃²⁺]⁶⁻ complex formation was estimated to be (2.4±0.8)×10⁴ dm³ mol⁻¹ by fluorescence titration, which indicates that the [Calx-S8⁸⁻·Ru(bpy)₃²⁺]⁶⁻ complex is the main species in 1:1 molar ratio aqueous solution of Calx-S8 and Ru(bpy)₃²⁺. In situ UV-Vis spectroscopic measurements indicated that Ru(bpy)₃²⁺ complexes can be readily deposited onto ITO electrode through electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) using [Calx-S8⁸⁻·Ru(bpy)₃²⁺]⁶⁻ host-guest complex as a dopant anion owing to the electrostatic interaction between the cationic conductive polymer and the anionic host-guest complex. The loading degree of the composite film with Ru(bpy)₃²⁺ can be determined by Lambert-Beer law modified for the two-dimensional concentration. The obtained composite film showed good photoelectric conversion properties in response to visible light irradiation. This is a novel photocurrent generation system in which the photoexcited state energy is efficiently collected by the conductive polymeric layer.     

Preparation,crystal structures and spectroscopic characterization of oxalate copper(II) complexes containing the nitrogen ligands 4,4′-dimethyl-2,2′-bipyridine and di(2-pyridyl)sulfide

The preparation, crystal structures and spectroscopic characterization of four oxalate copper(II) complexes containing the 4,4′-dimethyl-2,2′-bipyridine (Mebpy) or di(2-pyridyl)sulfide (DPS) nitrogen ligands namely [μ-(ox){Cu(Mebpy)(NO₃)(H₂O)}₂] (1), [μ-(ox){Cu(Mebpy)(ClO₄)(H₂O)}₂] (2), [μ-(ox){Cu(DPS)(H₂O)}₂](ClO₄)₂ (3) and [Cu(DPS)(ox)(H₂O)] · 2H₂O (4) are described. X-ray diffraction measurements have shown that complexes 1–3 are binuclear, in which the oxalate anion bridges two Cu(II) centers, while the complex (4) is mononuclear and the oxalate anion adopts the terminal bidentate chelating coordination mode. In 1 and 2 the Cu(II) sites display a distorted octahedral geometry (4+2 environment) and in compounds 3 and 4 the Cu(II) centers exhibit a slightly distorted square pyramidal geometry. In addition, complexes 1 and 2 present a 2D supramolecular arrangement through hydrogen bonds between coordination water molecules and nitrate or perchlorate anions and π-stacking interaction between the pyridyl rings of Mebpy nitrogen ligands.     

A novel tris(2,2′-bipyridine)ruthenium(II)/tripropylamine cathodic electrochemiluminescence in acetonitrile for the indirect determination of hydrogen peroxide

A novel tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) cathodic electrochemiluminescence (ECL) was generated at −0.78 V at the Pt electrode in acetonitrile (ACN), which suggested that the cathodic ECL differed from conventional cathodic ECL. It was found that tripropylamine (TPrA) could enhance this cathodic ECL and the linear range (log-log plot) was 0.2 μM-0.2 mM. In addition, hydrogen peroxide (H₂O₂) could inhibit the cathodic ECL and was indirectly detected with the linear range of 27-540 μM. The RSD (n = 12) of the ECL intensity in the presence of 135 μM H₂O₂ was 0.87%. This method was also demonstrated for the fast determination of H₂O₂ in disinfectant sample and satisfactory results were obtained.     

Determination of sophoridine and related lupin alkaloids using tris(2,2′-bipyridine)ruthenium electrogenerated chemiluminescence

Electrogenerated chemiluminescences (ECLs) based on tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) and lupin alkaloids, for instance, sophoridine (SRI), matrine (MT), sophoranol (SR) and sophocarpine (SC) in an aqueous alkaline buffer solution (pH 9.0) are studied. The light emission is mainly caused by an electro-oxidation reaction between tertiary amino group on the alkaloid compounds and Ru(bpy)₃²⁺ in a thin layer flow cell equipped with a glassy carbon disc electrode (22.1 mm²) at the potential of +1.50 V (versus Ag/AgCl). The luminescence wavelength of 610 nm confirmed that ECL is caused by Ru(bpy)₃^2+∗ to its ground state. ECL intensities of these lupin alkaloids are affected by the substituent character, three-dimensional conformation of hydrogen on β-carbon atom. Ionization potentials taken from calculation data further confirm the experimental results. In addition, the factors affecting the determination and HPLC separation of the four alkaloids are also investigated.     

Effect of oxygen plasma treatment on the surface properties of tin-doped indium oxide substrates for polymer LEDs

The effect of oxygen plasma treatment on the surface properties of tin-doped indium oxide (ITO) substrates and the changes in surface properties of treated ITO substrates with ageing time were investigated by X-ray photoelectron spectroscopy (XPS), contact angle and surface free energy measurements. Experimental results show that oxygen plasma treatment increases the oxygen concentration, decreases the carbon concentration, and enhances the surface free energy and polarity, and thereby improves the surface properties of ITO substrates. However, the improved ITO surface properties tended to decay and the surface free energy decreased, with ageing time. In addition, the ageing effect of treated ITO substrates on the performance of polymer light-emitting diodes (LEDs) was studied with respect to the driving voltage, electroluminescent luminance and efficiency. We observe that the ITO substrates aged for various times result in significant differences in optical and electrical characteristics which become worse as the ageing time increases. The optical and electrical performance of polymer LEDs is closely related to the surface properties of ITO substrate and the interface characteristics of ITO/polymer.     

A pyrazolyl-terminated 2,2′:6′,2″-terpyridine ligand: Iron(II), ruthenium(II) and palladium(II) complexes of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine

The preparation of 4′-(3,5-dimethylpyrazol-1-yl)-2,2′:6′,2″-terpyridine (2) under acidic conditions results in the formation of the salts [H₂2][MeOSO₃]₂ and [H₂2][EtOSO₃]₂, treatment of which with base leads to neutral 2. The structure of [H₂2][EtOSO₃]₂ · H₂O has been established by single crystal X-ray diffraction. The complexes [Fe(2)₂][PF₆]₂ and [Ru(2)₂][PF₆]₂ have been prepared and characterized, and the single crystal structure determination of [Ru(2)₂][PF₆]₂ is reported; [Fe(2)₂][PF₆]₂ is isostructural with [Ru(2)₂][PF₆]₂. Treatment of [Fe(2)₂]²⁺ with PdCl₂ produces [Pd(2)Cl]⁺, isolated and structurally characterized as the hexafluoridophosphate salt, illustrating that metal exchange within the tpy-binding domain occurs in preference to palladium(II) coordination by the N-donor atom of the pendant 3,5-dimethylpyrazol-1-yl unit in 2. [Pd(2)Cl]²⁺ can also be prepared from PdCl₂ and [H₂2][MeOSO₃]₂ in refluxing methanol.     

The intercalation reaction of 2,2′-bipyridine with layered compound MnPS3

The intercalation process of 2,2′-bipyridine into layered MnPS₃ is studied with powder X-ray powder diffraction (XRD) technology as the monitoring tool. From the XRD results, it is found that the absence or presence of acid greatly influences the existing form and the arranged orientation of the guest. Two series of the reactions are carried out. In Series A, only MnPS₃ and 2,2′-bipyridine are present. While in Series B, a variety of acetic acid is added. During the intercalation of Series A, there coexist four phases: the 00l phase (with lattice spacing of 6.47 Å) is pristine MnPS₃; the 00l′ phase (with lattice spacing of 9.81 Å), indicating the parallel orientation of the 2,2′-bipyridine molecular ring to the layer; the 00l″ phase (with lattice spacing of 12.20 Å), indicating the perpendicular orientation of the 2,2′-bipyridine molecular ring to the layer of the host, which is only an intermediate phase for the formation of the 00l′′′ phase; the 00l′′′ phase (with the lattice spacing of 15.33 Å), indicating the existence of the complex cation [Mn(bipy)₃]²⁺ coming from the in situ coordination of the inserted guest with intralayered Mn²⁺ ions between the interlayer space of host. As the intercalation proceeds, the 00l, 00l′ and 00l″ phases finally disappear, and 00l′′′ phase is intensified and a complete intercalate is obtained. In Series B, due to the presence of the acid, the formation of the complex cation [Mn(bipy)₃]²⁺ is inhibited, and the amount of the acid in the intercalation plays a key role in the formation of the guest. With the increase of the acid, the protonated bipyridine becomes the main existing form of the guest, which is arranged in the perpendicular orientation of molecular ring to the layer. From the experimental evidences, the possible intercalation mechanisms are proposed and the novel intercalation phenomenon of in situ coordination of the inserted 2,2′-bipyridine with Mn²⁺ of the host is elucidated.     

A new series of potentially hexadentate ligands derived from 2,2′-bipyridine

Reaction of 2,2′-bipyridine-6-carboxaldehyde with the appropriate aliphatic diamine in MeOH and subsequent reduction with NaBH₄ gives the new, potentially hexadentate, ligands N,N′-bis(2,2′-bipyridin-6-ylmethyl)ethane-1,2-diamine (bmet), N,N′-bis(2,2′-bipyridin-6-ylmethyl)propane-1,3-diamine (bmpp) and N,N′-bis(2,2′-bipyridin-6-ylmethyl)hexane-1,6-diamine (bmhx). The syntheses and characterisation of these ligands are reported; the ligands are isolated as the hydrochloride salts, with purification effected by either recrystallisation or cation exchange chromatography. [Co(bmet)](ClO₄)₃ · H₂O is obtained on reaction of bmet · 4.25HCl · 2.5H₂O with Na₃[Co(O₂CO)₃] · 3H₂O, and X-ray structural analysis shows this to have a pair of very short Co–N bonds. The synthesis and characterisation of the first coordination complex containing 6-(aminomethyl)-2,2′-bipyridine (amb) is also described.     

Synthesis and spectral properties of ruthenium(II) complexes based on 2,2′-bipyridines modified by a perylene chromophore

Five new 2,2′-bipyridines functionalized with a perylene or a perylenediimide moiety were synthesized and the corresponding heteroleptic ruthenium(II) complexes ([Ru(bpy)₂(L)](PF₆)₂; bpy = 2,2′-bipyridyl, L = perylene-substituted bpy ligand) were prepared. The UV–vis spectra of the ruthenium(II) complexes showed red-shifted and intense absorption bands derived from the conjugated structure of the new ligands.     

Determination of sodium oxalate in Bayer liquor using flow-analysis incorporating an anion exchange column and tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection

Semi-automated flow injection instrumentation, incorporating a small anion exchange column coupled with tris(2,2′-bipyridyl)ruthenium(II) (Ru(bipy)₃²⁺) chemiluminescence detection, was configured and utilised to develop rapid methodology for the determination of sodium oxalate in Bayer liquors. The elimination of both negative and positive interferences from aluminium(III) and, as yet, unknown concomitant organic species, respectively are discussed. The robustness of the methodology was considerably enhanced by using the temporally stable form of the chemiluminescence reagent, tris(2,2′-bipyridyl)ruthenium(III) perchlorate in dry acetonitrile. Real Bayer process samples were analysed and the results obtained compared well with those performed using standard methods within industrial laboratories.     

A simple one-pot synthesis of functionalised 6-(indol-3-yl)-2,2′-bipyridine derivatives via multi-component reaction under neat condition

A series of 4-aryl-6-(1H-indol-3-yl)-2,2-bipyridine-5-carbonitrile derivatives were synthesized via a one-pot multi-component reaction of aromatic aldehydes, 3-(cyanoacetyl)indole and 2-acetyl pyridine in ammonium acetate by conventional heating and microwave irradiation under solvent-free condition. Also a series of 6,6′-di(1H-indol-3-yl)-4,4′-diaryl-2,2′-bipyridine-5,5′-dicarbonitrile derivatives were synthesized using cinnamils, 3-(cyanoacetyl)indole and ammonium acetate. The methodology affords high yields of product at short reaction time.     

Bis(saccharinato)palladium(II) and platinum(II) complexes with 2,2′-bipyridine: Syntheses,structures, spectroscopic,fluorescent and thermal properties

New palladium(II) and platinum(II) complexes, cis-[Pd(bpy)(sac)₂] (1) and cis-[Pt(bpy)(sac)₂] (2), where sac = saccharinate, bpy = 2,2′-bipyridine, have been synthesized and characterized by elemental analysis, UV–Vis, IR, ¹H NMR and ¹³C NMR. The structures of the DMSO solvated complexes are determined by X-ray diffraction. Both complexes are isomorphous and the metal ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of pyridyl groups of bpy in a cis fashion. The mononuclear species interact each other through weak intermolecular C–H?O hydrogen bonds, C–H?π and π?π interactions leading to three-dimensional supramolecular networks. All complexes exhibit a high thermal stability in the solid state, and are fluorescent in the solution.     

Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH  7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5 mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<1 μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.     

Luminescence quenching of tris(2,2′-bipyridine)ruthenium(II) by phenol and dichlorophenols in sol-gel-processed spin-coated thin films

The luminescence spectral behaviour of the ruthenium(II)-tris-1,2-bipyridine ion (Ru(bpy)₃²⁺) included in organically modified silicate gel matrixes, and the luminescence quenching by phenol and dichlorophenols were investigated. The chloro-derivatives were 2,4-, 2,5- and 2,6-dichlorophenol. Sol-gel technology was used to prepare the “sol” with the precursor methyltriethoxysilane. Coating thin films were obtained from the “sol” by spin coating on glass slide. The Ru(bpy)₃²⁺ luminescence quenching experiments were carried out with the quencher in aerated aqueous solution at pH 12 in contact with the film. It was possible to observe an important blue shift in the Ru(bpy)₃²⁺ emission spectrum included in the films with respect to the aqueous solution. The quenching plots obtained showed a downward curvature. These plots could be fitted satisfactorily by a sum of two terms of Stern-Volmer with quenching constants K_SV1 and K_SV2 associated to two different binding sites of the ruthenium complex, which indicates the presence of a matrix microheterogeneity in the films. The K_SV1 and K_SV2 values and the corresponding fractions of the total emission f₀₁ and f₀₂ for both sites in the films suggest that only a low percentage of the probe is accessible to the quencher and that the probe is efficiently quenched in one of the sites. This site of the probe was assigned to the Site 1 in the results analysis. The value of its respective constant, K_SV1, was higher than the value of the constant K_SV in homogeneous aqueous solution for the studied quenchers, phenol and dichlorophenols.     

Spectroscopic, thermal and structural studies of cocrystal of 2,2′-diamino-4,4′-bis(1,3-thiazole) with 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene and 1,3-bis(4-pyridyl)propane

Three new cocrystals based upon 2,2′-diamino-4,4′-bis(1,3-thiazole) (DABTZ) with 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethylene (bpe) and 1,3-bis(4-pyridyl)propane (bpp): [(DABTZ) (4,4′-bipy)], [(DABTZ) (bpe)] and [(DABTZ) (bpp)] have been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and studied by thermal and X-ray crystallography. Self-assembly of these compounds in the solid state is likely caused by both hydrogen bonding, and π-π stacking.     

Effect of oxidant type on the chemiluminescence intensity from the reaction of tris(2,2′-bipyridyl)ruthenium(III) with various organic acids

An investigation into the chemiluminescence of fourteen organic acids and tris(2,2′-bipyridyl)ruthenium(II) was undertaken. Particular emphasis was placed upon the method of production of the reagent, tris(2,2′-bipyridyl)ruthenium(III), with cerium(IV) sulfate, potassium permanganate, lead dioxide and electrochemical generation. Analytically useful chemiluminescence was observed when Ce(IV) or potassium permanganate were employed as oxidants. The kinetics of analyte oxidation was related to the intensity of the chemiluminescence emission, which increased by three orders of magnitude for tartaric acid after 40 h of oxidation.