Comparative study on the photophysical properties between carbene-based Fe (II) and Ru (II) complexes

The comparative study on the photophysical properties between cheap metal Fe (II) complexes and noble metal Ru (II) complexes with identical ligand coordination is performed by the combination of density functional theory (DFT) and time-dependent density functional theory (TDDFT) to evaluate the potential alternative applications of Fe (II) complexes. RuBIP (BIP = 2,6-bis (imidazol-2- ylidene)pyridine) is theoretically established that the radiative lifetime of the second lowest triplet state is more consistence with experimental value. However, FeBIP retains nonluminous because of low-lying ³MC originated from weak d orbital splitting. FeBIPC (FeBIP with carboxylic acid groups) has twice longer lifetime than its parent complex FeBIP due to the great decrease of the energy gap between ³MLCT and ³MC. What's more, the lifetimes of Fe (II) complexes detected in the experiments are more accessible to nonradiative decay lifetimes of ³MC. The carboxylic acid groups are beneficial for the improvement of luminescent possibility and controllability of Fe (II) complexes, while there is still a huge challenge for effective material replacement comparing with Ru (II) complexes.     

Synthesis, characterization and DNA-binding and DNA-photocleavage studies of two Ru(II) complexes containing two main ligands and one ancillary ligand

DNA-binding and DNA-photocleavage properties of two Ru(II) complexes, [Ru(L¹)(dppz)₂](PF₆)₄ (1) and [Ru(L²)(dppz)₂](PF₆)₄ (2) (L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine, have been investigated. Experimental results show that the DNA-binding affinity of complex 1 is greater than that of 2, both complexes emit luminescence in aqueous solution, either alone or in the presence of DNA, complex 1 can bind to DNA in an intercalative mode while 2 most likely interacts with DNA in a partial intercalation fashion, and complex 2 serves as a better candidate for enantioselective binding to CT-DNA compared with 1. Moreover, complex 1 reveals higher efficient DNA cleavage activity than 2, during which supercoiled DNA is converted to nicked DNA with both complexes. Theoretical calculations for the two complexes have been carried out applying the density functional theory (DFT) method at the level of the B3LYP/LanL2DZ basis set. The calculated results can reasonably explain the obtained experimental trends in the DNA-binding affinities and binding constants (K_b) of these complexes.     

The excited states of bipyridyl and phenanthroline complexes of Fe(III), Ru(II) and Ru(III): A molecular orbital study

The semiempirical zero-differential-overlap molecular orbital model which was shown in earlier papers in this series to give a good account of the charge transfer and -* spectra of Fe(II) complexes with conjugated ligands such as 2,2-bipyridyl and 1,10-phenanthroline is extended to complexes having openshell ground states, such as those of Fe(III), and to complexes of Ru(II) and Ru(III). The results are used to assign the observed charge transfer and intra-ligand absorption bands to specific orbital transitions. Observed and calculated intensities are in good agreement: reasons are advanced for the much lower intensity of the charge transfer bands in Ru(III) compared to Ru(II) complexes.     

New Ru(II)–dmso complexes with heterocyclic hydrazone ligands towards cancer chemotherapy

The synthesis and characterization of ruthenium(II) complexes, [RuCl₂(dmso)₂(bfmh)] (1; dmso = dimethyl sulfoxide, bfmh = benzoic acid furan-2-ylmethylene-hydrazide), [RuCl₂(dmso)₂(btmh)](2; btmh = benzoic acid thiophen-2-ylmethylene-hydrazide), [RuCl₂(dmso)₂(bfeh)](3; bfeh = benzoic acid (1-furan-2-yl-ethylidene)-hydrazide) and [RuCl₂(dmso)₂(bpeh)](4; bpeh = benzoic acid (1-pyridin-2-yl-ethylidene)-hydrazide) are described. The ligands, when treated with either cis-[RuCl₂(dmso)₄] or trans(Cl)–[RuCl₂(dmso)₂(bpy)], resulted in the same products. This has been confirmed by IR spectra and single crystal X-ray diffraction studies. The redox behaviors of the complexes have been found to be strongly dependent on the electronic nature of the moieties present in the hydrazone ligands. The binding of the complexes to Herring sperm DNA has been studied by absorption titration and cyclic voltammetry. But, due to the random change in the absorption on the addition of DNA, only a qualitative result rather than a quantitative result has been obtained. All the complexes have been found to bind DNA through different modes to different extents. The antibacterial properties of the ligands and the complexes have been studied against five pathogenic bacteria and also the minimum inhibitory concentrations (MIC) of all the ligands and complexes 2 and 4 have been evaluated.     

Ruthenium(II) complexes bearing pyridine‐based tridentate and bidentate ligands: catalytic activity for transfer hydrogenation of aryl ketones

Ru(II) complexes of the general formula [RuCl₂(′′)(L)] (1: ′N = N_b, L = MeOH; 2: ′N = N_b, L = CH₃CN; 3: ′N = N_d, L = CH₃CN; 4: ′N = N_p, L = CH₃CN), [Ru(p‐cymene)(_a–b)Cl]Cl (5a: N N_a = 2,2′‐bipyridine; 5b: N N_b = 4,4′‐dimethyl–2,2′‐bipyridine), [Ru(′′)(_a–b)Cl]Cl (6a: ′N = N_b, _a = 2,2′‐bipyridine; 6b: ′N = N_b, _b = 4,4′‐dimethyl‐2,2′‐bipyridine; 7a: ′N = N_d, _a = 2,2′‐bipyridine; 7b: ′N = N_d, _b = 4,4′‐dimethyl‐2,2′‐bipyridine; 8a: ′N = N_p, _a = 2,2′‐bipyridine; 8b: ′N = N_p, _b = 4,4′‐dimethyl‐2,2′‐bipyridine) and [Ru(′′)(_a)Cl]BF₄ (9a: ′N = N_b; _a = 2,2′‐bipyridine) were synthesized from the corresponding [RuCl₂(p‐cymene)]₂ dimer, ′′ and _a–b ligands. The compounds were characterized by elemental analysis, IR and NMR. Complex 9a was studied by X‐ray diffraction, confirming its cationic‐mononuclear [RuCl(_bb)(_a)]⁺ nature. The synthesized Ru(II) complexes (1–8) were employed as catalysts for the transfer hydrogenation of ketones to secondary alcohols in the presence of KOH using 2‐propanol as a hydrogen source at 82°C. The rates of the transfer hydrogenation reactions strongly depended on the type of and ancillary ligands. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,spectral and antibacterial activity of Co(II), Ni(II) and Zn(II) complexes with 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H‐naphthalen‐1‐ylidene)‐hydrazide

A bioactive Schiff base HL i.e. 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H ‐naphthalen‐1‐ylidene)‐hydrazide was synthesized by reacting equimolar amount of salicylic acid hydrazide and 1‐tetralone. Co(II), Ni(II) and Zn(II) complexes of ligand HL was synthesized in 1:1 and 1:2 molar ratio of metal to ligand. The structure of the synthesized ligand and metal complexes was established by elemental analysis, molar conductance, magnetic susceptibility measurements, electronic, IR and EPR spectral techniques. For determining the thermal stability the TGA has been done. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6–31 + g(d,p) basis set. Spectral data reveal that ligand behave uninegative tridentate in ML complexes and uninegative bidentate in ML₂ complexes. On the basis of characterization octahedral geometry has been assigned for Co(II) and Ni(II) complexes, while tetrahedral for Zn(II) complexes. Antibacterial activity of the synthesized compounds were evaluated against Staphylococcus aureus , Bacillus subtilis, Escherichia coli , Xanthomonas campestris and Pseudomonas aeruginosa and the results revealed that metal complexes show enhanced activity in comparison to free ligand.     

1H NMR assignment corrections and 1H, 13C, 15N NMR coordination shifts structural correlations in Fe(II), Ru(II) and Os(II) cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline

¹H, ¹³C and ¹⁵N NMR studies of iron(II), ruthenium(II) and osmium(II) tris‐chelated cationic complexes with 2,2′‐bipyridine and 1,10‐phenanthroline of the general formula [M(LL)₃]²⁺ (M = Fe, Ru, Os; LL = bpy, phen) were performed. Inconsistent literature ¹H signal assignments were corrected. Significant shielding of nitrogen‐adjacent protons [H(6) in bpy, H(2) in phen] and metal‐bonded nitrogens was observed, being enhanced in the series Ru(II) → Os(II) → Fe(II) for ¹H, Fe(II) → Ru(II) → Os(II) for ¹⁵N and bpy → phen for both nuclei. The carbons are deshielded, the effect increasing in the order Ru(II) → Os(II) → Fe(II). Copyright © 2010 John Wiley & Sons, Ltd.     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.     

Density functional computations of alkynylation of ethanimine catalyzed by chiral zinc(II)‐complexes

The alkynylation of ethanimine catalyzed by chiral zinc(II)‐complexes was studied by means of the density functional theory (DFT). All the intermediates and transition states were optimized completely at the B3LYP/6‐31G(d,p) level. Calculation results confirm that the alkynylation of ethanimine is exothermic and the total released energy is about ?13 kJ/mol. The formation of the catalyst–alkynyl complexes M4 is the rate‐determining step for this alkynylation, and the formation of the catalyst–amine complexes M5 is the chirality‐limiting step for this alkynylation. The transition states for the chirality‐limiting step have a H? O? Zn? C? C? N six‐membered ring. The dominant products predicted theoretically for this alkynylation are, respectively, S‐amine for ethanimine anti and R‐amine for ethanimine syn . © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis and Characterization of Poly(phenylacetylene)s with Ru(II) Bis‐Terpyridine Complexes in the Side‐Chain

An alkyne‐functionalized ruthenium(II) bis‐terpyridine complex is directly copolymerized with phenylacetylene by alkyne polymerization. The polymer is characterized by size‐exclusion chromatography (SEC), ¹H NMR spectroscopy, cyclic voltammetry (CV) measurements, and thermal analysis. The photophysical properties of the polymer are studied by UV–vis absorption spectroscopy. In addition, spectro‐electrochemical measurements are carried out. Time‐resolved luminescence lifetime decay curves show an enhanced lifetime of the metal complex attached to the conjugated polymer backbone compared with the Ru(tpy)₂²⁺ model complex.

     

Synthesis,characterization, antitumor,and cytotoxic activity of mononuclear Ru(II) complexes

In the search for antitumor active metal complexes several ruthenium complexes have been reported to be promising. A series of mononuclear Ru(II) complexes, [Ru(T)₂(S)]²⁺, where T?=?2,2′-bipyridine/1,10-phenanthroline and S?=?CH₃-bitsz, Cl-bitsz, Br-bitsz, tmtsz, dmtsz, have been prepared and characterized by UV-Vis, IR, ¹H-NMR, FAB-mass spectroscopy, and elemental analysis. The complexes were subjected to in vivo anticancer activity against a transplantable murine tumor cell line Ehrlich's ascitic carcinoma (EAC) and in vitro cytotoxic activity against human cancer cell line Molt 4/C₈, CEM, and murine tumor cell line L1210. Ruthenium complexes showed promising biological activity especially in decreasing tumor volume and viable ascitic cell counts. Treatment with these complexes prolonged the life span of EAC-tumor-bearing mice by 10–48%. In vitro evaluation of these ruthenium complexes revealed cytotoxic activity from 0.21 to 24?µmol?L^?1 against Molt 4/C₈, 0.16–19?µmol?L^?1 against CEM, and 0.75–32?µmol?L^?1 against L1210 cell proliferation, depending on the nature of the compound.     

Synthesis and Characterization of Heteroleptic Ru(II) Complexes Based on 4,4′‐Bis((E)‐styryl)‐2,2′‐bipyridine as Ancillary Ligand and Application for Dye‐Sensitized Solar Cells

Heteroleptic Ru(II) complexes were designed based on 4,4′‐bis((E)‐styryl)‐2,2′‐bipyridine (bsbpy) as an ancillary ligand for dye‐sensitized solar cells (DSSCs), and those Ru(II) sensitizers, [Ru(L)(bsbpy)(NCS)₂][TBA] (TBA; tetrabutylammonium), were synthesized according to a typical one‐pot reaction of [RuCl₂(p‐cymene)]₂ with the corresponding anchoring ligands (where L = 4,4′‐dicarboxy‐2,2′‐bipyridine (dcbpy), 4,4′‐bis((E)‐carboxyvinyl)‐2,2′‐bipyridine (dcvbpy), 4,7‐dicarboxy‐1,10‐phenanthroline (dcphen), or 4,7‐bis((E)‐carboxyvinyl)‐1,10‐phenanthroline (dcvphen)). The new Ru(II) dyes, [Ru(L)(bsbpy)(NCS)₂][TBA] that incorporated vinyl spacer(s) into ancillary and/or anchoring ligand displayed red‐shifted bands over the overall UV/VIS region relative to the absorption spectra of N719 . A combination of bsbpy ancillary and dcphen anchoring ligand showed the best result for the overall power conversion efficiency (η); i.e., a DSSC fabricated with [Ru(dcphen)(bsbpy)(NCS)₂][TBA] exhibited a power conversion efficiency (η) of 2.98% (compare to N719 , 4.82%).     

Synthesis,characterization and catalytic,cytotoxic and antimicrobial activities of two novel cyclotriphosphazene‐based multisite ligands and their Ru(II) complexes

Two novel cyclotriphosphazene ligands ( 2 and 3 ) bearing 3‐oxypyridine groups and their corresponding Ru(II) complexes ( 4 and 5 ) were synthesized and their structures were characterized using Fourier transform infrared, ¹H NMR and ³¹P NMR spectroscopic data and elemental analysis. The Ru(II) complexes were used as catalysts for catalytic transfer hydrogenation of p‐substituted acetophenone derivatives in the presence of KOH. Additionally, the cytotoxic activities of compounds 2 , 3 , 4 , 5 were evaluated against PC3 (human prostate cancer), DLD‐1 (human colorectal cancer), HeLa (human cervical cancer) and PNT1A (normal human prostate) cell lines. Finally the antimicrobial activities of compounds 2 , 3 , 4 , 5 were evaluated against a panel of Gram‐positive and Gram‐negative bacteria and yeast cultures. The complexes showed efficient catalytic activity towards transfer hydrogenation of acetophenone derivatives, especially those bearing electron‐withdrawing substituents on the para‐position of the aryl ring. The compounds were found to have moderate to high cytotoxic and antimicrobial activities, and Ru(II) complexation enhanced both cytotoxic and antimicrobial activities in comparison with the parent compounds. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,characterization and DNA-binding properties of Ru(II) complexes coordinated by ofloxacin as potential antitumor agents

Three Ru complexes coordinated by oxfloxacin, [Ru(L)₂(OFX)]Cl·2H₂O (L = bpy, 1; dmbpy, 2; phen, 3; and OFX = ofloxacin), were synthesized and characterized. These complexes can inhibit the growth of cervical cancer HeLa cells efficiently. Furthermore, these three complexes exhibited excellent binding affinities with DNA, as confirmed by spectroscopy methods and viscosity experiments. Therefore, the synthesized Ru(II) complexes have excellent DNA-binding abilities with potential applications in cancer chemotherapy.     

Synthesis and Characterization of New Mononuclear Ru (II) PolypyridylComplexes with Catalytic Activity

In this work, we report the synthesis and physicochemical characterization of new chloro and aqua mononuclear Ru (II) complexes of formula [Ru(LLL)(dpp)Cl]PF₆ and [Ru(LLL)(dpp)OH₂](PF₆)₂ (LLL=tpy =2,2’ : 6’,2’’-terpyridine; tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine and dpp=2,3-bis(2-pyridil)pyrazine). For the complex [Ru(tptz)(dpp)Cl]PF₆, the complete structure was determined by X-ray diffraction. Catalytic studies of aqua-complexes revealed that they are active for the water oxidation reaction at pH 1 using cerium ammonium nitrate (CAN) as a sacrificial oxidant. Also, we were able to establish the reaction mechanism and rate constants of each stage of the catalytic cycle, turnover frequencies (TOFs), and turnover numberes (TONs). The experimental TON values for the aqua complexes were very close to the theoretical value of 7.5, indicating a high degree of recovery. DFT and TD-DFT calculations of electronic states for all complexes were consistent with experimental results and allowed the complete assignment of their UV-Visible bands and redox states.     

DFT study of the structure and spectral behavior of new pt(II) complexes with 5‐methyl‐5(4‐pyridyl)hydantoin

Platinum complexes are a great interest of study, because of the antitumor activity and the clinical use of some of them in the recent anticancer chemotherapy. In many cases, computational studies can be very useful for predicting the structure and some physicochemical properties of metal complexes. Theoretical calculations can also be used for the rational design of new complexes with optimal ratio: antitumor activity/toxicity. The geometry of three new Pt(II) complexes with general formula cis‐[PtL₂X₂] (where L is 5‐methyl‐5(4‐pyridyl)hydantoin and X = Cl^?, Br^?, I^?) and of the free organic ligand were optimized using the hybrid DFT method B3LYP with LAN2DZ basis sets. The results were in very good correlation with the data of similar compounds from the literature. The same DFT method was used for the study of their spectral behavior, by reproducing their IR and Raman spectra and comparing them with experimental data. In addition, the distribution of charges by ESP analysis was calculated. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Effects of the substituting groups and proton abstraction on the nonlinear optical properties of heteroleptic bis-tridentate Ru(II) complexes

The second-order nonlinear optical (NLO) properties have been carried out on a series of Ru(II) complexes with different 4′-substituted terpyridine derivatives and the tridentate ligand 2,6-bis(benzimidazole-2-yl)pyridine by using density functional theory (DFT). The introduction of different substituents enhances the static first hyperpolarizabilities in various degrees. Time-dependent density functional theory (TD-DFT) calculations indicate that the additional metal-to-ligand charge transfer (MLCT) transition, which is vectorially opposite to the intraligand charge transfer (ILCT) transition, could contribute to the smaller β_vec in species with electron-withdrawing groups compared to ones with electron-donating groups. The stepwise deprotonation brings about a change in electron density of the benzimidazole moiety and finally makes the moiety turn to be as donor, which subsequently leads to an efficient second-order NLO switching. For the species 3 with electron-donating group, the β_vec value of the mono-deprotonated system is 49.9 and 11.1 times as small as that of its diprotonated and fully deprotonated ones.     

Synthesis and photophysical properties of novel amphiphilic ruthenium (II) complexes containing 4,4′‐dialkylaminomethyl‐2,2′‐bipyridyl ligands

The synthesis of a number of new 2,2′‐bipyridine ligands functionalized with bulky amino side groups is reported. Three homoleptic polypyridyl ruthenium (II) complexes, [Ru(L)₃]²⁺ 2(PF₆^?), where L is 4,4′‐dioctylaminomethyl‐2,2′‐bipyridine (Ru4a), 4,4′‐didodecylaminomethyl‐2,2′‐bipyridine (Ru4b) and 4,4′‐dioctadodecylaminomethyl‐2,2′‐bipyridine (Ru4c), have been synthesized. These compounds were characterized and their photophysical properties examined. The electronic spectra of three complexes show pyridyl π → π* transitions in the UV region and metal‐to‐ligand charge transfer bands in the visible region. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis,spectroscopic properties,density functional theory calculations and nonlinear optical properties of novel complexes of 5‐hydroxy‐4,7‐dimethyl‐6‐(phenylazo)coumarin with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions

5‐Hydroxy‐4,7‐dimethyl‐6‐(phenylazo)coumarin (L) has been synthesized and its novel complexes with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions have also been prepared and identified using various analytical tools. The complexes are octahedral binding via one/two oxygen, nitrogen atoms for 1:1 and 1:2 complexes and two/three coordinated water molecules. All the prepared solid complexes behave as neutral in dimethylformamide. The optimized structures of the studied complexes were theoretically investigated at the B3LYP/6‐311G** level. Molecular stability and bond strengths were investigated by applying natural bond orbital analysis. The geometries of the studied complexes are non‐planar as indicated from the values of dihedral angles. The global properties of hardness, global softness and electronegativity were computed. The calculated small energy gap between highest occupied and lowest unoccupied molecular orbital energies shows that charge transfer occurs within the complexes. The obtained total static dipole moment, mean polarizability, anisotropy of polarizability and mean first‐order hyperpolarizability (<β>) were compared with those of urea as a reference material. The results for <β> showed that the complexes are excellent candidates as nonlinear optical materials. The three‐dimensional plots of the molecular electrostatic potential for some selected complexes were investigated.