Synthesis and characterization of tris(heteroleptic) diimine complexes of chromium(III)

A preparative procedure of potentially wide applicability is described for the synthesis of previously unreported tris(heteroleptic) [Cr(diimine)₃]³⁺ complexes. The synthetic scheme involves the sequential addition of three different diimine ligands, and employs CrCl₃ · 6H₂O as the initial Cr(III) reagent. The synthesis and characterization of the complexes [Cr(TMP)(phen)(diimine′)]³⁺ are reported (where TMP = 3,4,7,8-tetramethyl-1,10-phenanthroline, phen = 1,10-phenanthroline; and diimine′ is either bpy = 2,2′-bipyridine, Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine, 5-Clphen = 5-chloro-1,10-phenanthroline, or DPPZ = dipyridophenazine). Chiral capillary electrophoresis and electrospray mass spectrometry were essential aids in determining the presence or absence of diimine ligand scrambling. Utilizing emission and electrochemical data obtained on these compounds, the oxidizing power of the lowest lying excited state (²E_g(O_h)) was calculated, and was found to vary in a systematic fashion with diimine ligand type.     

Synthesis, spectroscopic and structural characterization of the reaction products of quaternary cationic 2,2′-bipyridylium ligand bromide salts with metal halides

The synthesis and spectroscopic characterization of quaternary salts containing 2,2,-bipyridine, 1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline and 3,4,7,8-tetramethyl-1,10-phenanthroline is reported. The coordinating behaviour of the bipyridylium salts toward palladium, copper and dimethyltin(IV)halides is investigated. The reaction of N-R,2,2′-bipyridylium (= L¹) bromide (R = 4-Cl-C₆H₄ · CO · CH₂) with palladium(II) chloride in acetonitrile solution yields a crystalline product, shown by a single crystal X-ray study to be L¹PdX₃, where X is a Cl/Br (1:1) composite.     

Ru(II) complexes of crowded delocalized diimine ligands

The ligands 3,3′-dimethylene-2,2′-bibenzo[g]quinoline and bisbenzo[2,3:9,8]-1,10-phenanthroline have been coordinated with Ru(II) to form both tris- and mixed ligand complexes. These species are highly congested about the metal center but can be formed through the use of microwave irradiation. Shielding and deshielding effects on the chemical shifts of the aryl as well as the bridge protons reveal important conformational effects. Bathochromic shifts are observed in the electronic absorption spectra, associated with increased delocalization of the ligand and lowering of the π*-energy level. Similar effects are observed for the reduction potentials while the oxidation potentials are much less sensitive to ligand structure.     

Metal-metal communication in diruthenium complexes of the bridging ligand bis(imidazo[4,5-f][1,10]phenanthroline)

A series of diruthenium complexes incorporating bis(imidazo[4,5-f][1,10]phenanthroline) bridging structures were synthesized and their electrochemical properties were investigated. Upon changing the ancillary ligands of one diruthenium complex from 2,2′-bipyridine (bpy) to 1,10-phenanthroline (phen), electrochemical experiments revealed behavior that suggested through-bridge, metal-to-metal communication. By changing the inductive properties of the bridging ligand, the degree of communication could be controlled. The results point toward a hole-type superexchange electron transport mechanism.     

The chemistry of peroxovanadium compounds relevant to insulin mimesis

The inorganic coordination chemistry of peroxovanadium compounds relevant to insulin mimesis is reviewed. The structure and kinetic reactivity of solutions of vanadate anion, vanadyl complexes and peroxovanadate complexes are briefly compared. Peroxovanadium compounds contain an oxo group, one or two peroxo ligands (O₂ ^2–) and an ancillary ligand which is usually bidentate. These compounds approximate a trigonal bipyramidal structure which can be divided conceptually into a polar oxo half and a relatively non-polar organic half. This presents a number of interesting design variations which are discussed with respect to the development of a rudimentary structure-activity correlation of insulin mimetic ability.Abbreviations phen 1,10-phenanthroline - 4,7-Me₂phen 4,7-dimethyl-1,10-phenanthroline - 3,4,7,8-Me₄phen 3,4,7,8-tetramethyl-1,10-phenanthroline - 5-CH₃phen 5-methyl-1,10-phenanthroline - 5-NO₂phen 5-nitro-1,10-phenanthroline - 5-NH₂phen 5-amino-1,10-phenanthroline - bipy 2,2-bipyridine - bipyH 2,2-bipyridinium - 4,4-Me₂bipy 4,4-dimethyl-2,2-bipyridine - bipy-4,4-(COO)2 2,2-bipyridine-4,4-dicarboxylato - pic pyridine-2-carboxylato - 3-OHpic 3-hydroxypyridine-2-carboxylato - 3-acetpic 3-acetatoxypyridine-2-carboxylato - m,n-pdc pyridine-m,n-dicarboxylato - ox oxalato - pzc pyrazine-2-carboxylato - 3-NH₂pzc 3-aminopyrazine-2-carboxylato - 4OH-2,6pdc 4-hydroxy-2,6-pyridinedicarboxylato - IDA iminodiacetato - cit citrato - EDTA ethylenediaminetetraacetato - HEDTA ethylene-diaminetetraacetic acid - isoquin isoquinoline-2-carboxylato - quin quinolato - NTA nitrilotriacetato - glyH glycine - cystH cysteine - nicH nicotinic acid - Hheida N-(2-hydroxyethyl)iminodiacetato     

Interaction of copper(II) with the non-steroidal anti-inflammatory drugs naproxen and diclofenac: synthesis, structure, DNA- and albumin-binding

Copper(II) complexes with the non-steroidal anti-inflammatory drugs (NSAIDs) naproxen and diclofenac have been synthesized and characterized in the presence of nitrogen donor heterocyclic ligands (2,2′-bipyridine, 1,10-phenanthroline or pyridine). Naproxen and diclofenac act as deprotonated ligands coordinated to Cu(II) ion through carboxylato oxygens. The crystal structures of (2,2′-bipyridine)bis(naproxenato)copper(II), , (1,10-phenanthroline)bis(naproxenato)copper(II), and bis(pyridine)bis(diclofenac)copper(II), have been determined by X-ray crystallography. The UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA with (2,2′-bipyridine)bis(naproxenato)copper(II) exhibiting the highest binding constant to CT DNA. Competitive study with ethidium bromide (EB) indicates that the complexes can displace the DNA-bound EB suggesting strong competition with EB. The cyclic voltammograms of the complexes recorded in the presence of CT DNA have shown that the complexes can bind to CT DNA by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. The NSAID ligands and their complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values. The biological properties of the previously reported complexes [Cu₂(naproxenato)₄(H₂O)₂], [Cu₂(diclofenac)₄(H₂O)₂] and [Cu(naproxenato)₂(pyridine)₂(H₂O)] have been also evaluated. The dinuclear complexes exhibit similar affinity for CT DNA as the 2,2′-bipyridine or 1,10-phenanthroline containing complexes. The pyridine containing complexes exhibit the lowest affinity for CT DNA and the lowest ability to displace EB from its EB-DNA complex.     

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

The neutral mononuclear zinc complexes with the quinolone antibacterial drug oxolinic acid in the absence or presence of a nitrogen donor heterocyclic ligand 2,2′-bipyridine or 1,10-phenanthroline have been synthesized and characterized. The experimental data suggest that oxolinic acid is on deprotonated mode acting as a bidentate ligand coordinated to the metal ion through the ketone and one carboxylato oxygen atoms. The crystal structures of (chloro)(oxolinato)(2,2′-bipyridine)zinc(II), 2, and bis(oxolinato)(1,10-phenanthroline)zinc(II), 3, have been determined with X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV and fluorescence spectroscopies. UV studies of the interaction of the complexes with DNA have shown that they can bind to CT DNA and the DNA-binding constants have been calculated. Competitive studies with ethidium bromide (EB) have shown that complex 3 exhibits the ability to displace the DNA-bound EB indicating that it binds to DNA in strong competition with EB.     

Ruthenium(II) mixed-ligand complexes containing 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline: Synthesis, DNA-binding and photocleavage studies

Two novel Ru(II) complexes [Ru(bpy)₂(MCMIP)]²⁺ (1) and [Ru(phen)₂(MCMIP)]²⁺ (2) (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline; MCMIP = 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline) have been synthesized and characterized by elemental analysis, mass spectra and ¹H NMR. The DNA-binding properties of the complexes were investigated by absorption, emission, melting temperature and viscosity measurements. Experimental results indicate that the two complexes can intercalate into DNA base pairs. Upon irradiation at 365 nm, two Ru(II) complexes were found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to nicked form II, and the mechanisms for DNA cleavage by the complexes were also investigated.     

Synthesis, characterization and properties of series coordination polymers constructed from a biphenyl dicarboxylate and nitrogen-containing mixed ligands

A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co₂(dpa)₂(4,4′-bpy)₂(H₂O)]_n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]_n (2) and discrete complexes [Co₂(dpa)₂(2,2′-bpy)₂(H₂O)₂] (3), [Co₃(dpa)₃(1,10′-phen)₆(H₂O)₂] (4), [Cd(dpa)(1,10′-phen)₂][(H₂dpa)₂(H₂O)₂] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.     

Stimulation of the activity of prolyl hydroxylase in 3T3 fibroblasts by 1,10-phenanthroline.

In confluent cultures of 3T3 fibroblasts, incubated for 24 h with 1,10-phenanthroline at 10(-5)--10(-9) M, the activity of prolyl hydroxylase was significantly increased. 1,10-Phenanthroline was inhibitory at concentrations greater than 10(-4) M. The stimulatory effect of 1,10-phenanthroline manifests itself after 6 h incubation and increased with time up to 48 h. 2,2'-dipyridyl and 5,6-dimethyl-1,10-phenanthroline were also stimulatory; a nonchelating analog, 1,7-phenanthroline had no effect. Cycloheximide did not modify the 1,10-phenanthroline effect. The stimulatory effect does not seem to depend on the shift of an inactive precursor of prolyl hydroxylase to an active form because 1,10-phenanthroline was shown to be ineffective in logarithmically growing cells. While dialysis of washed and homogenized cells significantly increased prolyl hydroxylase activity in cell extracts, undialyzed 1,10-phenanthroline treated samples exhibited higher prolyl hydroxylase activity than dialyzed controls. These data suggested to us that 1,10-phenanthroline and other chelating agents may be forming complexes with certain metal ions or protein-metal ions which are inhibitory towards prolyl hydroxylase.     

Synthesis, structure and antitumor activity of [RhCl3(N-N)(DMSO)] polypyridyl complexes

The [RhCl₃(N-N)(DMSO)] complexes, the N-N being 2,2′-bipyridine (1), 1,10-phenanthroline (2), 4,7-diphenyl-1,10-phenanthroline (3), 4,4′-dimethyl-2,2′-bipyridine (4) and 1,10-phenanthroline-5,6-dione (5), have been synthesized and characterized with spectroscopic methods. The compounds 2-5 adopt mer- and complex 1fac-structure. The molecular and electronic structure studies of mer- and fac-complexes with bpy and phen ligands at the DFT B3LYP level with 3-21G^∗∗ basis set showed that mer-isomers are more stable. The cytostatic activity of the [RhCl₃(N-N)(DMSO)] complexes against Caco-2 and A549 tumor cells have been studied. Their antibacterial activity have also been investigated. It has been found that the very promising biological activity show complexes 2, 3 and 4.     

Stimulation of the activity of prolyl hydroxylase in 3T3 fibroblasts by 1,10-phenanthroline

In confluent cultures of 3T3 fibroblasts, incubated for 24 h with 1,10-phenanthroline at 10^?5–10^?9 M, the activity of prolyl hydroxylase was significantly increased. 1,10-Phenanthroline was inhibitory at concentrations greater than 10^?4 M. The stimulatory effect of 1,10-phenanthroline manifets itself after 6 h inhubation and increased with time up to 48 h. 2,2′-dipyridyl and 5,6-dimethyl-1-1,10-phemamthroline were also stimulatory; a nonchelating analog, 1,7-phenanthroline had no effect.Cycloheximide did not modify the 1,10-phenanthroline effect. The stimulatory effect does not seem to depend on the shift of an inactive precursor of prolyl hydroxylase to an active form because 1,10-phenanthroline was shown to be ineffective in logarithmically growing cells.While dialysis of washed and homogenized cells significantly increased prolyl hydroxylase activity in cell extracts, undialyzed 1,10-phenanthroline treated samples exhibited higher prolyl hydroxylase activity than dialyxed controls.These data suggested to us that 1,10-phenanthroline and other chelating agents may be forming complexes with certain metal ions or protein-metal ions which are inhibitory towards prolyl hydroxylase.     

Luminescent ruthenium(II) amidodipyridoquinoxaline biotin complexes that display higher avidin-induced emission enhancement

A series of luminescent ruthenium(II) amidodipyridoquinoxaline biotin (dpq-B) complexes [Ru(N-N)₂(N-N′)](PF₆)₂ (N-N = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (Ph₂-phen); N-N′ = 2-((2-biotinamido)ethyl)amidodipyrido[3,2-f:2′,3′-h]quinoxaline (dpq-C2-B), 2-((6-biotinamido)hexyl)amidodipyrido[3,2-f:2′,3′-h]quinoxaline (dpq-C6-B)) has been designed as new luminescent probes for avidin. The electrochemical and photophysical properties of these complexes have been investigated. Upon irradiation, all the complexes exhibited metal-to-ligand charge-transfer (³MLCT) (dπ(Ru) → π^∗(diimine)) emission in fluid solutions at 298 K and in low-temperature glass. In aqueous buffer, the emission was extremely weak, probably a consequence of hydrogen-bonding interactions between the amide moiety of the dpq-B ligands and the water molecules. The avidin-binding properties of all the complexes have been studied by 4′-hydroxyazobenzene-2-carboxylic acid (HABA) assays, luminescence titrations, kinetics experiments and confocal microscopy using avidin-conjugated microspheres.     

Adducts of europium β-diketonates with nitrogen p,p′-disubstituted bipyridine and phenanthroline ligands: Synthesis, structural characterization, and luminescence studies

Europium complexes featuring fluorinated β-diketonate ligands [thenoyltrifluoroacetone (tta), 4,4,4-trifluoro-1-phenyl-1,3-butanedione (btfac), and 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate (hfac)] and nitrogen p,p′-disubstituted bipyridine and phenanthroline ligands [4,4′-dimethoxy-2,2′-bipyridine (dmbipy) and 4,7-dimethyl-1,10-phenanthroline (dmphen)] were synthesized. Their structures were determined by single crystal X-ray diffraction. Octacoordinate complexes were obtained using trifluorinated tta and btfac, while nonacoordinated complexes were produced using hexafluorinated hfac. The differences in coordination number and bond lengths of these complexes are rationalized in terms of the electronic and steric features of the ligands. UV excitation of the complexes led to red luminescence characteristic of trivalent europium ion. The high overall quantum yields observed for the europium complexes bearing hfac and dmbipy or dmphen ligands are rationalized in terms of the relatively high ligand-to-metal energy transfer efficiencies.     

Nickel-quinolones interaction: Part 3 — Nickel(II) complexes of the antibacterial drug flumequine

Nickel(II) complexes with the first-generation quinolone antibacterial agent flumequine in the presence or absence of nitrogen donor heterocyclic ligands (4-benzylpyridine, pyridine, 2,2′-bipyridine or 1,10-phenanthroline) have been structurally characterized by physicochemical and spectroscopic techniques. The experimental data suggest that flumequine acts as deprotonated bidentate ligand coordinated to Ni(II) through the carboxylato and ketone oxygen atoms. The crystal structures of bis(4-benzylpyridine)bis(flumequinato)nickel(II) 2, (2,2′-bipyridine)bis(flumequinato)nickel(II) 4 and (1,10-phenanthroline)bis(flumequinato)nickel(II) 5 have been determined by X-ray crystallography and are the first crystal structures of flumequinato complexes reported. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes bind to CT DNA and bis(aqua)bis(flumequinato)nickel(II) exhibits the highest binding constant to CT DNA. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. The cyclic voltammograms of the complexes recorded in DMSO solution and in 1/2 DMSO/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that in the presence of CT DNA they bind to CT DNA by the intercalative binding mode. The complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values.     

1,10-Phenanthroline-cuprous ion complex, a potent inhibitor of DNA and RNA polymerases.

The inhibition by 1,10-phenanthroline of $\text{E. coli}$ DNA polymerase I has recently been attributed to the formation in the assay mixtures of a unique and effective inhibitor, the 2:1 1,10-phenanthroline-cuprous ion complex (1). We have now found that this coordination complex is also an effective inhibitor of $\text{E. coli}$ DNA dependent RNA polymerase, Micrococcus luteus DNA dependent DNA polymerase, and T-4 DNA dependent DNA polymerase. This conclusion is based either on the requirement of a thiol for 1,10-phenanthroline inhibition or on the reversal of 1,10-phenanthroline inhibition by the non-inhibitory cuprous ion specific chelating agent 2,9-dimethyl-1,10-phenanthroline. 2,2′,2″-Terpyridine is also very effective at relieving 1,10-phenanthroline inhibition. The reversal of 1,10-phenanthroline inhibition should be attempted before it is claimed that 1,10-phenanthroline inhibits any polymerases by coordinating a zinc ion at the active site.     

Synthesis and near IR photoluminescence of Os(II) bis(2,2′-bipyridine) (3,8-diarylethynyl-1,10-phenanthroline) complexes: anomalous behavior in the 3,8-dinitrophenylethynyl-substituted homologue

A large bathochromic shift (?50 nm) and emission in the near infrared is observed by attaching arylethynyl groups at the 3,8-positions of the 1,10-phenanthroline ligand (phen) of [Os(bipy)₂(phen)]²⁺ (where bipy = 2,2′-bipyridine). Thus [Os(bipy)₂(3,8-di-4-methoxyphenylethynyl-1,10-phenathroline)]²⁺ emits at 795 nm, while [Os(bipy)₂(3,8-diphenylethynyl-1,10-phenanthroline)]²⁺ emits at 815 nm. According to this trend it would have been expected that [Os(bipy)₂(3,8-di-4-nitrophenylethynyl-1,10-phenathroline)]²⁺ emits farther in the near infrared. Nevertheless, this complex is not photoluminescent because of intramolecular electron transfer quenching of the MLCT excited state by the nitroaromatic group. These results set structural and redox potential standards in the design of near infrared emitters based on [Os(bipy)₂(phen)]²⁺ type complexes.     

Application of a luminescence-based pH optrode to monitoring of fermentation by Klebsiella pneumoniae

The application of an optical sensor based on immobilization of the ruthenium complex [Ru(bpy)2(dhphen)]2+ (bpy = 2,2'-bipyridine, dhphen = 4,7-dihydroxy-1,10-phenanthroline) in Nafion to pH monitoring of fermentation by Klebsiella pneumoniae is described. Interference from the culture medium can be eliminated by addition of a black microporous filter membrane (pore size: 0.45 microm) on top of the sensing film. The response of this pH optrode was found to show good correlation with the conventional pH electrode.     

Conformational stability of ferrocytochrome c. Electrostatic aspects of the oxidation by tris(1,10-phenanthroline)cobalt(III) at low ionic strength

At ionic strengths below 0.1 M the oxidation of horse ferrocytochrome c by tris(1,10-phenanthroline)cobalt (III) and tris(2,2'-bipyridine)cobalt(III) proceeds by a pathway which is independent of the transition metal complex concentration. Formation of an activated form of the protein appears to be rate limiting. The rate of oxidation decreases as the ionic strength increases. This dependence of the reaction rate on inert electrolyte concentration indicates that electrostatic association of anions under physiological ionic strength confers stability to the protein. The activated form of the protein, which reacts at least 10(4) times as fast as the predominant form, is thought to be a conformation of the reduced protein with an open heme crevice. Binding of the open form of ferrocytochrome c with the redox-inactive cationic transition metal complexes hexamminecobalt(III) and tris(1,10-phenanthroline)chromium(III) inhibits the oxidation by tris(1,10-phenanthroline)cobalt(III). Reactions of tris(1,10-phenanthroline)cobalt(III) with 4-carboxy-2,5-dinitrophenyllysine 13 and 72 ferrocytochromes c show no dependence on ionic strength. NMR studies at pH 7 demonstrate that ferricytochrome c is partly (15%) in the open conformation at low ionic strength. Furthermore, the interaction of redox-inert tris (1,10-phenanthroline)chromium(III) with ferricytochrome c under conditions identical to those of the kinetic studies demonstrates that the transition metal complex binds only to the open form of the protein. Titration with increasing amounts of tris(1,10-phenanthroline) chromium(III) shows changes in the NMR spectrum that are inconsistent with a single binding site.     

Effect of 1,10-phenanthroline on ultrastructure of pea leaves

Summary We have examined ultrastructural changes of mesophyll cells in pea leaves induced by the photodynamic herbicide 1,10-phenanthroline (Phe). Dark incubation of pea plants did not cause any damage in plants or changes in the ultrastructure of mesophyll cells. Two hours of illumination after pretreatment with Phe caused photooxidative damage in plant but was not sufficient to markedly change the ultrastructure, although dilation of endoplasmic reticulum (ER) cisternae occurred. Illumination for 12 h caused inhibition of grana formation in pretreated plants. These ultrastructural changes and the inhibition of chlorophyll (Chl) accumulation may be due to the inhibition of transport of certain proteins to the plastids, diminished accumulation of chlorophyll proteins (e.g., LHCP) and a decrease in activity of the chlorophyll synthetase.Abbreviations ALA 5-aminolevulinate - 2,2 2,2-bipyridyl - Chl chlorophyll - ER endoplasmic reticulum - 8H 8-hydroxyquinoline - LHCP light-harvesting chlorophyll a/b-binding proteins - PBs prolamellar bodies - Mg-Proto Mg-protoporphyrin - Mg-Proto-Me Mg-protoporphyrin monomethyl ester - Pchlide protochlorophyllide - Phe 1,10-phenanthroline - Proto protoporphyrin IX