Influence of Fine Ligand Substitution Modification of the Isocyanidometal Bridge on Metal-to-Metal Charge Transfer Properties in Class II–III Mixed Valence Complexes

The synthesis and characterization of Class II–III mixed valence complexes have been an interesting topic due to their special intermediate behaviour between localized and delocalized mixed valence complexes. To investigate the influence of the isocyanidometal bridge on metal-to-metal charge transfer (MMCT) properties, a family of new isocyanidometal-bridged complexes and their one-electron oxidation products cis-[Cp(dppe)Fe−CN−Ru(L)₂-NC−Fe(dppe)Cp][PF₆]_n (n=2, 3) (Cp=1,3-cyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane, L=2,2’-bipyridine (bpy, 1[PF₆]_n ), 5,5’-dimethyl-2,2’-bipyridyl (5,5’-dmbpy, 2[PF₆]_n ) and 4,4’-dimethyl-2,2’-bipyridyl (4,4’-dmbpy, 3[PF₆]_n )) have been synthesized and fully characterized. The experimental results suggest that all the one-electron oxidation products may belong to Class II–III mixed valence complexes, supported by TDDFT calculations. With the change of the substituents of the bipyridyl ligand on the Ru centre from H, 5,5’-dimethyl to 4,4’-dimethyl, the energy of MMCT for the one-electron oxidation complexes changes in the order: 1³⁺ < 2³⁺ < 3³⁺ , and that for the two-electron oxidation complexes decreases in the order 1⁴⁺ > 3⁴⁺ > 2⁴⁺ . The potential splitting (ΔE_1/2(2)) between the two terminal Fe centres for N[PF₆]₂ are the largest potential splitting for the cyanido-bridged complexes reported so far. This work shows that the smaller potential difference between the bridging and the terminal metal centres would result in the more delocalized mixed valence complex.     

Formation and Photoelectrochemical Properties of Charge Transfer Complexes between Fullerene and Metallophthalocyanine

Fullerelleshavegeneratedarapidlygrowingandactiveresearchareabecauseoftheirunusualstructureandphysico-chemicalproperties.Fullerenes(C,.,.C,,)havehigherelectrollaffinity(2.75ev),soitiswellkllownthattheyareexcellentelectronacceptorsandhavealargenumberofcolljugatedrsbondswhichmayleadtolargenon-linearpolarizabilities'.C,,.,isreportedtoformchargetranstbrcomplexes(CTC)withappropriateelectrondonors,forexample,polymolecularPVK,y-cyclodextrin,aromaticandaliphaticammes'-3.Thecharge-transferinteraction…     

β-Diketiminato Rare-Earth Metal Complexes: The Influence of Monoatomic Substituents in the N-aryl Moieties on Structures and Properties

Treatment of β-diketiminate ligands bearing different N-aryl monoatomic substituents [HL^H = (C₆H₅)N = C(Me)CH=C(Me)NH(C₆H₅), HL^F = (2,6-F₂C₆H₃)N=C(Me)CH=C(Me)NH(2,6-F₂C₆H₃), and HL^Cl = (2,6-Cl₂C₆H₃)N=C(Me)CH=C(Me)NH(2,6-Cl₂C₆H₃)] with Ln(CH₂SiMe₃)₃(THF)₂ (Ln = Y and Lu) afforded a variety of β-diketiminato rare-earth metal complexes depending on substituents, namely, phenyl ring C–H bond activated complexes (L')(L^H)Lu(THF) ( 1b , L' = (C₆H₄)N = C(Me)CH=C(Me)N(C₆H₅)), six-coordinate homoleptic complexes (L^H)₃Ln [Ln = Y ( 1aa ), Lu ( 1bb )], five-coordinate monoalkyl complexes (L^F)₂Ln(CH₂SiMe₃) [Ln = Y ( 2a ), Lu ( 2b )], and four-coordinate dialkyl complexes (L^Cl)Ln(CH₂SiMe₃)₂ [Ln = Y ( 3a ), Lu ( 3b )]. All these complexes were characterized with NMR spectroscopy, and lutetium complexes 1b , 1bb and 3b were structurally validated by single-crystal X-ray diffraction analysis. Moreover, dialkyl complexes 3 promoted the polymerization of 2-vinylpyridine (2-VP) to produce atactic poly(2-vinylpyridine) (P2VP) with quantitative yield. On activation with an equimolar amount of [Ph₃C][B(C₆F₅)₄], complexes 3 afforded highly isotactic P2VP with an mm value up to 94 %. Both ¹H NMR spectrum and MALDI-TOF mass analysis of an oligomer indicate that the polymerization was initiated by coordination insertion of 2-VP into the Y-CH₂SiMe₃ bond.     

Theoretical Studies on the Excited-state Properties of Ru(Ⅱ) Polypyridyl Complexes

Using DFT/TDDFT methods,the excited-state lifetimes of Ru(Ⅱ) polypyridyl complexes were computed accurately and the reason of Ru(Ⅱ) polypyridyl complexes with long excited-state lifetimes was explained by the electron-transfer distances and HOMO-LUMO gaps.Finally,the photovoltaic conversion efficiencies of complexes were predicted using DFT and docking methods.This work has provided methods of predicting the excited-state lifetimes and photovoltaic conversion efficiencies of Ru(Ⅱ) polypyridyl complexes.     

Influence of Substituents in β-Cyclodextrin on the Interaction of Levofloxacin–β-Cyclodextrin Complexes with Liposomal Membrane

Colloid Journal - The effect of substituents (polar CH2CH(OH)CH3, hydrophobic CH3, and charged $${{\left( {{\text{C}}{{{\text{H}}}_{{\text{2}}}}} \right)}_{{\text{4}}}}{\text{SO}}_{3}^{ - }$$ ) in...     

Charge Transfer Complexes of Crown Ethers with Π-Acceptors. The Influence of NaCl and KCl on Their Stability

A spectrophotometric study was conducted on solutions of benzo-15-crown-5, dibenzo-18-crown-6 and dibenzo-24-crown-8 with the -acceptors, DDQ, and CHL in dichloromethane at room temperature. The stabilities of the resulting charge transfer complexes with the -acceptors DDQ were found to decrease in the order DB18C6>DB15C5>DB24C8 and with CHL it follows the order DB18C6>DB24C8. The addition of either NaCl or KCl affects the values of formation constants (K_c) and the order of stabilities of the charge transfer complexes. The formation constants in the absence and presence of NaCl and KCl salts were calculated and discussed.     

Substituents Effect on the Optical Properties of Benzonitrile and Oligobenzonitriles

During the past decades, the organic systems with good electronic and optical property,such as oligomer and polymers, have been attracted much attention because of theiroptical nonlinearity, fast response, relatively low cost, ease of fabrication and integrationinto devices. Generally to say, the common oligomers or polymers that we usually studyare all of carbon-carbon or heteroaromatic conjugated system. In previous work, thesynthesis of new linear -(C=N).- conjugated systems, polynitriles h…     

Investigation on Magnetic Properties of Exchange Coupled Transition Metal Complexes Ⅱ．Theoretical Model for Trinuclear Complexes

ＩｎｖｅｓｔｉｇａｔｉｏｎｏｎＭａｇｎｅｔｉｃＰｒｏｐｅｒｔｉｅｓｏｆＥｘｃｈａｎｇｅＣｏｕｐｌｅｄＴｒａｎｓｉｔｉｏｎＭｅｔａｌＣｏｍｐｌｅｘｅｓⅡ．ＴｈｅｏｒｅｔｉｃａｌＭｏｄｅｌｆｏｒＴｒｉｎｕｃｌｅａｒＣｏｍｐｌｅｘｅｓＸｉｅＸｉｕ－Ｌａｎ；...     

Influence of Substituents in the Aromatic Fragment of the Benzoate Anion on the Structures and Compositions of the Formed {Cd–Ln} Complexes

Russian Journal of Coordination Chemistry - The reactions of Cd(NO3)2 ? 4H2O and Eu(NO3)3 ? 6H2O with potassium salts of the benzoic acid derivatives and 2,2'-bipyridine (Bipy) in...     

Benzoylation and Properties of 14-π Nickel(II)-Tetraazaannulene Complexes with Substituents on the Phenyl Ring

The benzoylated asymmetrical nickel(II) complexes, 2,4,9,11-tetramethyl-3,10-dibenzoyl-1,5,8,12-([14]-Xbenzo)tetraazacyclotetradecinato(2-)nickel(II) ( A_1-4) and 2,4,10,12-tetramethyl-3,11-dibenzoyl-1,5,9,13-([15]-Xbenzo)tetraazacyclotetradecinato(2-)nickel(II) (B_1-4), wherein X = CH₃(A₁ and B₁), H ( A₂ and B₂), Cl (A₃ and B₃) and NO₂(A₄ and B₄), have been synthesized and characterized by analysis, IR, electronic, ¹H- and ¹³C-NMR spectra. An intense IR band due to C=O stretching is present in the range 1630-1650 cm^-1 upon benzoylation. Electronic spectra show bands at 375-390 nm with k_max = 10000-26000 M^-1cm^-1 due to π→π* transitions of macrocycles and at 500-550 nm with k_max = 1000-5000 M^-1cm^-1 attributable to LMCT for each of the complexes. The proton peaks of methine sites in the NMR spectra disappear on benzoylation. Results of the carbon-13 NMR spectra are compatible with those of the proton NMR. Cyclic voltammograms of the complexes in acetonitrile exhibit two successive and reversible (irreversible in DMSO) oxidation peaks for the macrocycle (Mc M Mc ^{” +} and Mc ^{” +} M Mc ²⁺) in the ranges +0.31 - +0.51 and +0.60 - +0.84 V, respectively. In the reduction area, a reversible wave is followed by reduction of metal {Ni(II) M Ni(I) at around m 2.32 V}. Unlike analogous complexes without the benzoyl group, those compounds are not electropolymerized by cyclic voltammetry.     

Effect of Amines on the Surface Charge Properties of Iron Oxides

Specific studies detailing the effects of amines, used as pH control agents for corrosion inhibition in power plants, on the surface charge of iron oxides provide data to assess the mechanism of how these amines impact deposition rate. The current study was undertaken in order to determine accurately the dissociation constants of the relevant amines at Pressurized Water Reactor (PWR) operating conditions and to investigate the effect of sorption of two of these amines (morpholine and dimethylamine) by magnetite. The acid-dissociation equilibria of morpholine (MOR), dimethylamine (DMA) and ethanolamine (ETA) were measured potentiometrically with a hydrogen-electrode concentration cell (HECC) from 0 to 290 °C in sodium trifluoromethanesulfonate (NaTr) solutions at ionic strengths up to 1 mol⋅kg⁻¹. Magnetite surface titrations were performed at an ionic strength of 0.03 mol⋅kg⁻¹ (NaTr medium) in the presence or absence of morpholine and dimethylamine buffers over a wide range of pH and total amine concentrations at 150–250 °C. D.A. Palmer is retired.     

Influence of Fe concentration on the properties of the electrodeposited Zn–Fe coatings

Electrodeposition of Zn–Fe alloys on a copper substrate from a sulfate bath with different Fe²⁺ concentration (0.05, 0.10 and 0.20 mol L^?1) at room temperature was investigated using cyclic voltammetry. The influence of the Fe²⁺ content in the plating bath on the surface morphology, structural and magnetic properties of the coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The results show that the morphology of Zn–Fe films changes with different Fe²⁺ concentration. The EDS analysis demonstrated that the Fe content of the coatings increased with increasing the Fe concentration in the bath. XRD measurements shows the presence of ?Zn (hcp), δ1ZnFe (hcp) and the ΓZnFe (bcc) phases with a (101) preferential orientation in all the electrodeposited films. The magnetic analysis of Zn–Fe films indicated that the saturation magnetization was largely enhanced in comparison to pure Zn, especially with 0.2 at. % Fe, while the coercivity decreased.     

Influence of the Substituents on Imino-aryl Ring of Mono(imino)pyrrole-Ni~(Ⅱ) Complexes to Their Ethylene Polymerization Catalytic Performance

In order to study the influence of substituents on imino-aryl rings of mono(imino)pyrrole-transition metal complexes to their ethylene polymerization performance, a series of mono(imine)pyrroles(L1-L3) were synthesized by microwave irradiation from 2-acetylpyrrole and a series of 2,6-position disubstituted anilines(substituent: H, Me, Et). A simplified synthetic method was introduced to prepare the corresponding nickel complexes NiL_2(1～3) with direct condensation of mono(imine)pyrrole ligands and nickel dichloride. All the compounds were fully characterized by 1 H NMR, IR, EA, MS, and X-ray crystal diffraction. Ligand L3(C_(16)H_(20)N_2, Mr = 240.34) belongs to the triclinic system, space group P1, with a = 7.9606(19), b = 9.028(2), c = 11.205(3) ?, the final R = 0.0606 and wR = 0.1875. Complex 3(C_(32)H_(38)N_4Ni, Mr = 537.37) belongs to the monoclinic system, space group C2/c with a = 19.811(3), b = 11.262(2), c = 26.004(4) ?, the final R = 0.0388 and wR = 0.1020. The crystal structures indicated that all the Ni~(Ⅱ) complexes have similar tetra-coordinated geometries, in which the ligand chelated to the center nickel with a 2:1 molar ratio. Catalytic properties of the Ni~(Ⅱ) complexes for ethylene polymerization were systematically investigated, and the results showed a regular increase of catalytic activities with steric hindrance of the substituents on the imino-aryl ring of Ni~(Ⅱ) complexes.     

UV-visible Absorption Studies of Tetrachloro-p-benzoquinone and Tertiary Amines Charge Transfer Complexes in Trichloromethane

TCBiswellknownasnacceptorwhichcanformCTcomplexeswithmanydonormolecules"',andalsocanbeusedintheanalysisandqualitycontrolofdrugsindifferentpharmaceuticaldosageforms3.AlthoughspectrophotometricalmethodisoftenusedtostudythecharacterofCTcomplexes,verylittleresearchonCTcomplexesformedbyTCBandsimpletertiaryaminehavebeenfound.Recently,weemploythespectrophotometricalmethodtoStudytheCTcomplexesusingtheTCBasnacceptorandtertiaryamineasdonors.Inthispaper,wereporttheaboveresultsandexplainsomephenomen…     

Trinuclear Organometallic Pt−Ir−Pt Complexes: Insights into Photophysical Properties,Amino Acid Binding and Protein Sensing

The rational synthesis of trinuclear emissive organometallic complexes with two equivalent platinum(II) centres appended to the ancillary substituted 2,2′-bipyridyl ligand of the cyclometalated iridium(III) centre is reported here. The alkynyl-platinum moiety and cyclometalated iridium(III) centres have been separated through a non-conjugated CH₂−O−CH₂ linkage. The emission titration with amino acids reveals that the complexes sense free amino acids. The luminescence sensing of BSA is thus attributed to the amino acid sensing ability of the complexes and confirmed by emission anisotropy and Far-UV CD spectral study. The decrease in α-helix in the CD spectra signifies the changes in the secondary structure of protein in presence of the complexes.     

Novel Roles of Metal Ions in Layered Self-assembled Films of Polynuclear Complexes on Their Photoinduced Electron Transfer Properties

Three metal ion bridged self-assembled(SA)films of cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium were fabricated and characterized by contact angle,UV spectra,cyclic voltammetry and XPS.Theirphotoinduced electron transfer properties(PETP)were examined.Among the titled systems,the highest steady an-odic photocurrent of 1773—1843 nA/cm~1 and the highest quantum yield of 3.2% were achieved.The effects of in-cident light intensity,bias voltage,and electron donor were also studied.The possible mechanism of electron trans-fer was proposed.The results reveal that different metal ion in SA films could affect significantly the photoinducedelectron transfer property.Our experimental results clearly show that bridging metal ions can play both functionaland structural roles in these self-assembled systems.This method of forming functional films can provide a new ap-proach to regulate the property of similar systems.     

Complexation of Monosulfonated Triphenylphosphine with Chemically Modified β-Cyclodextrins: Effect of Substituents on the Stability of Inclusion Complexes

Interactions between the meta-substituted monosulfonated triphenylphosphine and chemically modified β-cyclodextrins were investigated in aqueous solution by NMR and UV–vis spectroscopy. Titration and continuous variation plots obtained from ³¹P NMR data indicate that the monosulfonated triphenylphosphine forms 1:1 inclusion complexes with the 2-hydroxypropylated β-cyclodextrin, the methylated β-cyclodextrin and the (2-hydroxy-3-trimethylammoniopropyl)-β-cyclodextrin chloride. These inclusion complexes are more stable that those formed with native β-cyclodextrin, confirming that poisoning of the chemically modified β-cyclodextrins by the hydrosoluble phosphine occurs when modified cyclodextrins are used as mass transfer promoters in aqueous-phase organometallic catalysis.This revised version was published online in July 2005 with a corrected issue number.     

Determination of Some Pharmaceutically – Important Aminoquinoline Antimalarials,via Charge – Transfer Complexes

Abstract

A simple and rapid spectrophotometric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug with 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) as a π-electron acceptor, forming a highly coloured stable radical anion. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer bands have been studied. Beer's Law is obeyed over aminoquinoline antimalarials concentration range of 0.4–4.0 ug.ml^?1. The proposed procedure has been applied successfully to the analysis of antimalarials in their dosage forms and the results are in agreement with those of official methods.     

The Significant Influence of a Second Metal on the Antiproliferative Properties of the Complex [Ru(η6−C10H14)(Cl2)(dmoPTA)]

Complexes [Ru(η⁶−C₁₀H₁₄)(Cl₂)(HdmoPTA)](OSO₂CF₃) ( 1 ), [Ru(η⁶−C₁₀H₁₄)(Cl₂)(dmoPTA)] ( 2 ) and [Ru(η⁶−C₁₀H₁₄)(Cl₂)-μ-dmoPTA-1κP:2κ²N,N’-MCl₂] (M=Zn ( 3 ), Co ( 4 ), Ni ( 5 ), dmoPTA=3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) have been synthesized and characterized by elemental analysis and spectroscopic techniques. The crystal structures of 1 , 3 and 5 were obtained by single-crystal X-ray diffraction. The antiproliferative activity of the complexes was evaluated against colon cancer cell line Caco-2/TC7 by using the MTT protocol. The monometallic ruthenium complexes 1 and 2 were found to be inactive, but the bimetallic complexes 3 , 4 and 5 display an increased activity (IC₅₀ 3 : 9.07±0.27, 4 : 5.40±0.19, 5 : 7.15±0.30 μM) compared to cisplatin (IC₅₀=45.6±8.08 μM). Importantly, no reduction in normal cell viability was observed in the presence of the complexes. Experiments targeted to obtain information on the possible action mechanism of the complexes, such as cell cycle, ROS and gene expression studies, were performed. The results showed that the complexes display different properties and action mechanism depending on the nature of metal, M, bonded to the CH₃N_dmoPTA atoms.