Synthesis and pH-sensitive redox properties of 1,10-phenanthroline-5,6-dione complexes

Synthesis and pH-sensitive electrochemical properties of three complexes, [Cu(PD)₃] · (ClO₄)₂ · 2.25CH₃CN · 6H₂O (1), [Cu(PD)(DMSO)Cl₂] · DMSO · H₂O (2) and [Co(PD)₃] · (ClO₄)₂ · CH₃CN · 2H₂O (3) (PD=1,10-phenanthroline-5,6-dione), are reported. Single-crystal X-ray diffraction of the complexes suggest that the structure of 1 is orthorhombic, 2 triclinic and 3 orthorhombic. The electrochemical properties of free PD and the three complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potentials of these compounds are strongly dependent on the proton concentration in the range ?0.3 V ～ 0.4 V versus SCE (saturated calomel reference electrode). The reduction behavior of PD can be described from quinone species to semiquinone anion then to the fully reduced dianion. At pH < 4, the reduction of PD proceeds via 2e^?/3H⁺ processes, while at pH > 4, the reduction of PD proceeds via 2e^?/2H⁺. For all complexes, the N–N chelate PD ligand is electrochemically active and underwent step reduction via 2e^?/2H⁺.     

Oxidative DNA cleavage by Cu(II) complexes of 1,10-phenanthroline-5,6-dione

A dimeric dichloro-bridged copper(II) complex [Cu₂(pdon)₂Cl₄] · 2DMF (1) and two mononuclear copper(II) complexes [Cu(pdon)(DMSO)Cl₂] · DMSO · H₂O (2) and [Cu(pdon)₃] · (ClO₄)₂ · 2.25CH₃CN · 6H₂O (3) (pdon = 1,10-phenanthroline-5,6-dione) have been synthesized and characterized. Variable-temperature magnetic susceptibility studies indicate the existence of weak anti-ferromagnetic coupling in the binuclear complex. The interaction of these complexes with CT-DNA (calf thymus DNA) has been studied using absorption and emission spectral methods. The apparent binding constants (K _app) for 1, 2 and 3 are 5.20 × 10⁵, 2.68 × 10⁵ and 7.05 × 10⁵ M^?1, respectively, showing moderate intercalative binding modes. All of these complexes cleave plasmid DNA to nicked DNA in a sequential manner as the concentration or reaction time is increased. The cleavage mechanism between the complex and plasmid DNA is likely to involve singlet oxygen ¹O₂ and ?OH as reactive oxygen species.     

Effect of the central metal on coordination of 1,10-phenanthroline-5,6-dione in Keggin-based hybrid compounds

Two new Keggin-based hybrid compounds, [Cu₂(pdon)₃][PMo^VI ₁₁Mo^VO₄₀]·3H₂O (1) and [Mn₂Cl(H₂O)₂(pdon)₄][PMo₁₂O₄₀]·2H₂O (2) (pdon = l, l0-phenanthroline-5,6-dione) (pdon), were synthesized under hydrothermal conditions. By using different metal ions and tuning the ratio of metal to ligand, pdon shows different coordination modes. In compound 1, pdon with three kinds of coordination modes link Cu^II ions to form a 1D wave chain and Keggin-type polyanions [PMo^VI ₁₁Mo^VO₄₀]^4? fringe this 1D chain; hydrogen bonding interactions extend these 1D chains into a 2D supramolecular network. Compound 2 exhibits a discrete structure, in which pdon shows a single chelating coordination. Electrochemical properties of the title compounds have been investigated.     

ESI-MS studies of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline and 1,10-phenanthroline-5,6-dione as ligands

In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione. Owing to the solvent-ligand hydrogen-bond formation, the solvent-ligand clusters were formed in the polar protic solvents. The number of protic solvent molecules per complex ion in cluster depended on the number of 1,10-phenanthroline-5,6-dione ligands in the complex ion. Unlike MeOH, EtOH, or water, ACN was not involved in the formation of the solvent clusters with the iron complexes containing 1,10-phenanthroline-5,6-dione as ligand. We also showed that the NCS- group under certain solvent conditions served as a bidentate ligand.     

Electrochemical biosensors based on redox carbon nanotubes prepared by noncovalent functionalization with 1,10-phenanthroline-5,6-dione

To improve the electrocatalytic activities of carbon nanotubes (CNT) towards the oxidation of nicotinamide adenine dinucleotide (NADH), we derive them with a redox mediator, 1,10-phenanthroline-5,6-dione (PD), by the noncovalent functionalization method. The redox carbon nanotubes (PD/CNT/GC) show excellent electrocatalytic activities towards the oxidation of NADH (catalytic reaction rate constant, k(h) = 7.26 × 10(3) M(-1) s(-1)), so the determination of NADH can be achieved with a high sensitivity of 8.77 μA mM(-1) under the potential of 0.0 V with minimal interference. We also develop an amperometric ethanol biosensor by integration of alcohol dehydrogenase (ADH) within the redox carbon nanotubes (PD/CNT/GC). The ethanol biosensor exhibits a wide linear range up to 7 mM with a lower detection limit of 0.30 mM as well as a high sensitivity of 10.85 nA mM(-1).     

Nuclease activity of copper(II) complex containing 1,10-phenanthroline-5,6-dione and L-phenylalanine ligands

The interaction between CT-DNA and a ternary copper (II) complex, [Cu(phendio)(L-Phe)(H₂O)](ClO₄)·H₂O (CuPP, phendio = 1,10-phenanthroline-5,6-dione, L-Phe = L-phenylalanine), has been conducted by electronic spectra, fluorescence spectroscopy and cyclic voltammetry. It has been found that the max. absorption peak from the electronic spectra is red shifted and the intensity is weakened and that the values of peak current from cyclic voltammetry are decreased significantly in the presence of DNA compared with that in the absence of DNA. At the same time, the complex can quench the emission intensity of EB-DNA system. The existence of the intercalation mode between the complex and DNA was proven. By submarine gel electrophoresis, we found that the copper(II) complex can cleave circular plasmid pBR322 DNA into nicked and linear forms in the presence of ascorbic acid and H₂O₂. __________ Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2007, 40(1): 32–36 [译自: 南开大学学报(自然科学版)]     

Acid-base equilibria of various oxidation states of aqua-ruthenium complexes with 1,10-phenanthroline-5,6-dione in aqueous media

Syntheses and pH dependent electrochemical properties of aqua-ruthenium(II) complexes, [Ru(trpy)(PDA-N,N')(OH2)](ClO4)2 ([1](ClO4)2) and [Ru(trpy)(PD-N,N')(OH2)](ClO4)2 ([2](ClO4)2) (trpy = 2,2':6',2'-terpyridine, PDA = 6-acetonyl-6-hydroxy-1,10-phenanthroline-5-one, PD = 1,10-phenanthroline-5,6-dione) are presented. Treatment of [Ru(trpy)(PD-N,N')Cl](PF6) with AgClO4 in a mixed solvent of acetone and H2O selectively produced the acetonyl-PD complex [1](ClO4)2, and the similar treatment in a mixed solvent of 2-methoxyethanol and H2O gave the PD complex [2](ClO4)2. The molecular structures of both complexes were determined by X-ray structural analysis. The proton dissociation constants of various oxidations state of [1]2+ and [2]2+ were evaluated by simulation of E(1/2) values of those redox potentials depending on pH. The simulation revealed that the acetonyl-PD complex [1]2+ underwent successive Ru(II)/Ru(III) and Ru(III)/Ru(IV) redox couples though the two redox reactions were not separated in the cyclic voltammograms. The redox behavior of [2]2+ in H2O is reasonably explained by not only the similar successive metal-centered redox reactions but also simultaneous two-electron quinone/catechol redox couple of the PD ligand including the contribution of hydration on a carbonyl carbon.     

Preparation and separation of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline-5,6-dione as ligand

The synthesis, separation, and characterization of mixed-ligand iron(II) complexes containing 1,10-phenanthroline (phen), 1,10-phenanthroline-5,6-dione (pdon), and NCS^? are reported. The mixed-ligand complexes [Fe(phen)(pdon)₂]²⁺ and [Fe(phen)₂(pdon)]²⁺ were prepared from iron(II) sulfate hepta hydrate and both ligands. The mixture of both complexes formed regardless the ratio of the ligands or the reaction time; therefore, the complexes were separated successfully on the reversed phase (RP) Develosil RP-Aqueous [C30] 5?µm, 150?×?4.6?mm column by two different methods. The first method was the ion paired RP chromatography performed under gradient elution with acetonitrile–water containing 0.001?mol?L^?1 KPF₆ aqueous as mobile phases. The second method was the RP chromatography performed under gradient elution with methanol and water as mobile phases. The gradient elution with water–methanol as eluents was preferred for the semi preparative separations allowing one to use the complexes without further purification upon separation, different than the first method and its variations so far. Three complexes (5, 6, and 7) were characterized by electrospray ionization mass spectrometry, NMR, UV-Vis, and IR.     

Synthesis and Crystal Structure of the Copper(Ⅱ) Complex with Tris- (1,10-phenanthroline-5,6-dione)

The title complex [ CuL3 ] (C1O4)2 · 2H2O· 2CH3CN (L = 1, 10-phenanthroline-5, 6-dione) has been synthesized and characterized by elemental analysis, conductivity, infrared and UV-Vis spectra. X-ray diffraction analysis at room temperature indicates that the complex (C40H28Cl2 CuNsO16, Mr = 1011.14) crystallizes in orthorhombic system, space group P21 21 21 with a = 13. 983(1), b = 14. 310 (1), c =20.890(2) (A。), V = 4179.7(6) (A。)3, Z = 4, Dc= 1.607g/cm3, F(000) = 2026,μ(MoKa) = 0.736 mm-1. The final R and w,R factors are 0.0446 and 0. 1212 respectively with 8545 independent reflections. The title complex is composed of a discrete [CuL3 ]2+ cation, uncoordinated ClO4- anions, H2O and CH3CN molecules. The central Cu(Ⅱ) atom is six-coordinated by six nitrogen donors of three ligands. The coordination geometry of Cu(Ⅱ) could be considered as an approximately ideal octahedral configuration with little static Jahn-Teller distortion (the longest and shortest Cu- N bonds are 2. 102 vs 2. 139 (A。) with the mean length of 2. 122 (A。) ), which is very rare for a six-coordinated Cu(Ⅱ) complex.     

Synthesis and Crystal Structure of the Copper(II) Complex with Tris-(1,10-phenanthroline-5,6-dione)

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Efficient Synthesis of 1,10-Phenantroline-5,6-dione

Russian Journal of General Chemistry - A method for the synthesis of 1,10-phenanthroline-5,6-dione via oxidation of 1,10-phenanthroline in the Br2-H2SO4-HNO3 system has been elaborated.     

Vibrational assignment of the spectral data and thermodynamic properties of 2-chloro-4-fluorobenzophenone using DFT quantum chemical calculations

The FT-Raman (3500-100 cm⁻¹) and FT-IR (4000-450 cm⁻¹) spectra of 2-chloro-4-fluorobenzophenone were recorded in the solid phase. Density functional theory calculations with B3LYP/6-31G (d, p) basis set was used to determine the ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities and Raman activities of this compound. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-31G (d, p) level, have also been obtained from force-field calculations. The wavenumbers found after scaling of the force field showed very good agreement with the experimentally determined values. A comparison of the theoretical spectra and experimental FT-IR and FT-Raman spectra of the title molecule has been made and full vibrational assignments of the observed spectra have been proposed. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.     

Vibrational study of tolazoline hydrochloride by using FTIR-Raman and DFT calculations

Quantum mechanical (QM) calculations have been carried out in order to study the tolazoline hydrochloride theoretical structure and vibrational properties. This compound was characterized by infrared and Raman spectroscopies in the solid phase. For a complete assignment of the IR and Raman spectra, the density functional theory (DFT) calculations were combined with Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology in order to fit the theoretical frequency values to the experimental ones. An agreement between theoretical and available experimental results was found. Three intense bands in the infrared spectrum characteristic of the protonated species of the compound were detected. Also, the possible charge-transfer and the topological properties for both benzyl and imidazoline rings were studied by means of Natural Bond Orbital (NBO) and Atoms in Molecules theory (AIM) investigation.     

Vibrational spectrum and assignment of 4-cyclopentene-1,3-dione

The IR and Raman spectra of 4-cyclopentene-1,3-dione have been studied. A complete assignment of the observed bands is proposed on the basis of the usual criteria (contours of the IR bands in the vapour phase and depolarization state of the Raman bands). For the planar species the assignment is confirmed by a normal-coordinate calculation.     

Synthesis, crystal structure, electrochemical and fluorescence studies of a novel Zn(II)-fluorophore, 1,10-phenanthroline-5,6-dione (phen-dione)

The crystal structure of 1,10-phenanthroline-5,6-dione ligand with Zn(II), tris(1,10-phenanthroline-5,6-dione)zinc(II) hexafluorophosphate, [Zn(phen-dione)₃](PF₆)₂, is reported. The complex was characterized by elemental analysis, IR, ¹H NMR, electronic absorption spectroscopies, cyclic voltammetry and X-ray crystallography. Yellow crystals of [Zn(phen-dione)₃](PF₆)₂ were formed by ether diffusion into an acetonitrile solution of the complex. The title complex crystallized in monoclinic crystal system (Z = 2) with space groups of P2 ₁, a = 12.0299(15) Å, b = 14.5306(19) Å, c = 13.1879(17) Å, β = 94.058(2)º and V = 2299.5(5) ų. The structure was refined by using 10048 independent reflections, with I > 2σ(I) to an R factor of 0.0490. Single-crystal structure showed that the coordination geometry around the Zn(II) was a distorted octahedron. The complex showed an intense fluorescence band at visible region (690 nm) in CH₃CN with an excitation wavelength of 310 nm at 25.0 ± 0.1 ºC. Cyclic voltammogram of the title complex showed two quasi-reversible reduction couples at negative potential, which were assigned to the consecutive reduction of phen-dione ligand to phen-semiquinonate and phen-diolate respectively by analogy to other phen-dione complexes at scan rate 200 mV s^-1.     

Ambidentate and redox-properties of 4,7-phenanthroline-5,6-dione in cobalt complexes: a quantum chemical study

Mono- and dinuclear adducts of cobalt diketonates with tetradentate 4,7-phenanthroline- 5,6-dione were modeled within the framework of DFT UB3LYP*/6-311++G(d,p) approximation. A competitive coordination of the metal ion to different donor centers of the redox-active ligand was studied. Variation of substituents in the diketone moieties allowed one to reveal compounds than can undergo thermally initiated one- and two-step valence tautomeric rearrangements. The calculated energy and magnetic characteristics of the dinuclear complexes give reasons to consider them as potential basis of molecular electronics and spintronics devices.     

1,10-邻菲咯啉-5,6-二酮制备反应中副产物的形成与控制

由1,10-邻菲咯啉合成1,10-邻菲咯啉-5,6-二酮反应的副产物的形成与控制研究表明,1,10-邻菲咯啉在5,6位二酮化反应中的副反应产物及主产物分离时产生的副产物均为4,5-二氮杂芴-9-酮,二酮化反应条件(包括作为氧化剂的强混合酸H2SO4/HNO3的加入量、时间和温度)和主产物分离时体系的酸度对副产物的形成有重要影响,优化了二酮化反应条件和产物分离时的体系pH控制范围。在此优化条件下,可有效控制副产物的形成,使主产物1,10-邻菲咯啉-5,6-二酮的收率达到92%以上。     

NADH Electrooxidation Using Bis(1,10-phenanthroline-5,6-dione) (2,2'-bipyridine)ruthenium(II)-Exchanged Zirconium Phosphate Modified Carbon Paste Electrodes

We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10‐phenanthroline‐5,6‐dione)(2,2′‐bipyridine)ruthenium(II) ([Ru(phend)₂bpy]²⁺) exchanged into the inorganic layered material zirconium phosphate (ZrP). X‐Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)₂bpy]²⁺ intercalation from 10.3 Å to 14.2 Å. The UV‐vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)₂bpy]²⁺. The UV‐vis spectrophotometric results indicate that the [Ru(phend)₂bpy]²⁺ concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)₂bpy]²⁺ exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°′=–38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis–Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers' yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.