Synthesis and characterisation of N-1,10-phenanthrolin-5-ylalkylamides and their photosensitising heteroleptic Ru(II) complexes

In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands as functionalised photosensitisers for singlet molecular oxygen generation in heterogeneous phase, we describe the synthesis and spectroscopic characterisation of different amide-functionalised N-1,10-phenanthrolin-5-ylalkylamides. These chelators are used to obtain heteroleptic [Ru(phen)₂L]²⁺ complexes, where L stands for 2-iodo-N-1,10-phenanthrolin-5-ylacetamide (5-iap), 4-oxo-4-(1,10-phenanthrolin-5-ylamino)butanoic acid (5-suap), 5-oxo-5-(1,10-phenanthrolin-5-ylamino)pentanoic acid (5-glap) and tert-butyl 4-oxo-4-(1,10-phenanthrolin-5-ylamino)butylcarbamate (BOC-5-ngap). The spectroscopic data, excited state lifetimes and quenching rate constants with O₂ (ca. 3.7×10⁹ L mol⁻¹ s⁻¹) of these novel complexes are also reported.     

Synthesis and characterization of new D-π-D type Schiff base ligands and its complexes with Cobalt(II), Ruthenium(II)

A Schiff base ligands, N-{(1E,2E)-3-[4-(dimethylamino)phenyl]prop-2-en-1-ylidene}-1,10-phenanthrolin-5-amine(mpa) and (1E,2E)-3-[4-(dimethylamino)phenyl]acrylaldehyde9H-fluoren-9-ylidenehydrazone(mfh), have been synthesized from the reaction of 4,5-diazafluorenone-9-hydrazone and 5-amino-1,10-phenanthroline with 4-(dimethylamino)cinnamaldehyde. The Co(II) and Ru(II) complexes of the ligands were prepared and characterized. The metal-to-ligand ratio of the Co(II) complex was found to be 2: 1 and that of the Ru(II) complex was found to be 1: 1. The ligands and complexes have been characterized by FTIR, UV-visible, ¹H NMR and fluorescence spectra, as well as, elemental analyses, TGA-DSC-DTG and mass spectra.     

Synthesis and investigation of anti-inflammatory and anticonvulsant activities of novel coumarin-diacylated hydrazide derivatives

A number of novel coumarin derivatives synthesized by the reaction of 3-carbonyl chloride coumarin with some substituted aryl acid hydrazides to investigate their anti-inflammatory and anticonvulsant activities. Carrageenan (0.1 ml of 1%, w/v) was injected subplantarly in the right paw of rats to induce an acute model of inflammation. Anti-inflammatory efficacy was evaluated for 5 hours at 3 different dosages 5, 10, 25 mg/kg. After that, the changes in the level of paw edema volumes and percentage inhibition of all groups were observed and the most effective coumarin derivative was found as N'-(2-hyroxybenzoyl)-2-oxo-2H-chromene-3-carbohydrazide. In addition, N’-(2-oxo-2H-chromene-3-carbonyl)nicotinohydrazide, (E)-N’-(3-(4-hydroxyphenyl)acryloyl)-2-oxo-2H-chromene-3-carbohydrazide, and N’-(5-amino-2-hydroxybenzoyl)-2-oxo-2H-chromone-3-carbohydrazide showed their anti-inflammatory effects in a dose-dependent manner. On the other hand, pentylenetetrazole (PTZ, 80 mg/kg, i.p.)-induced seizure model was used to investigate the anticonvulsant activities of six newly synthesized coumarin derivatives in mice. Hybrid compound of salicylic acid hydrazide and 3-carbonyl chloride coumarin (8d) was found the most promising anticonvulsant agent among all treatment groups according to the onset of seizure and survival rate. Moreover, (E)-N'-cinnamoyl-2-oxo-2H-chromene-3-carbohyrazide (8b) and (E)-N'-(3-(4-hyroxyphenyl)acryloyl)-2-oxo-2H-chromene-3-carbohydrazide (8c) has potential anticonvulsant efficiency in low doses (30 mg/kg). The anticonvulsant effect of these coumarin derivatives may be through enhanced GABA-mediated inhibition in the brain.     

Terminal group effects on the fluorescence spectra of Eu(III) nitrate complexes with a family of amide-based 1,10-phenanthroline derivatives

Four ligands 1,10-phenanthroline-5,6-bis(N,N-dibenzyl-1′-oxopropylamide) (L^a) 1,10-phenanthroline-5,6-bis(N-methyl-N-benzyl-1′-oxopropylamide) (L^b) 1,10-phenanthroline-5,6-bis(N-benzyl-1′-oxopropylamide) (L^c) and 1,10-phenanthroline-5,6-bis(N,N-diethyl-1′-oxopropylamide) (L^d), and their lanthanide(III) (La and Eu) complexes were synthesized. The complexes were characterized by elemental analysis, IR, fluorescence spectroscopy and conductivity. The lanthanide atoms are coordinated by O atoms from C=O, Ar–O –C and N atoms from phen With the difference of the ligands, the fluorescent intensities of the Eu(III) complexes vary regularly in the THF solution. Some factors that influence the fluorescent intensity were discussed.     

Synthesis,photophysical, electrochemical,and ion-binding properties of Ru(II) polypyridyl complexes containing benzo-15-crown-5

Two polypyridyl ligands, 5-(4′-ethynylbenzo-15-crown-5)-2,2′-bipyridine (L¹) and 3-bromo-8-(4′-ethynylbenzo-15-crown-5)-1,10-phenanthroline (L²), and their Ru(II) complexes [(bpy)₂RuL](PF₆)₂ have been prepared and characterized. Both complexes exhibit metal-to-ligand charge transfer absorption at around 452 nm and emission at around 640 nm in MeCN solution. Electrochemical studies of the complexes reveal a Ru(II)-centered oxidation at around 1.31 V and three ligand-centered reductions. The binding ability of the complexes with Na⁺ has been investigated by UV/Vis absorption, emission, and electrochemical titrations. Addition of Na⁺ to MeCN solutions of both complexes results in a progressive enhancement of the emission, a red-shift of the UV/Vis absorption, and a progressive cathodic shift of the Ru(II)-centered E _1/2 couple. The stability constants for the 1:1 stoichiometry adducts of the complexes with Na⁺ have been obtained from the UV/Vis absorption titrations.     

Synthesis,spectral, electrochemical and magnetic properties of new symmetrical and unsymmetrical dinuclear copper(II) complexes derived from binucleating ligands with phenol and benzimidazole donors

New symmetrical 2,6-bis{N-[2-(2-benzimidazolyl)-phenyl]iminomethyl}-4-methylphenol (L¹) and unsymmetrical 2-N-[2-(2-benzimidazoyl)phenyl]iminomethyl-6-[(4-methylpiperazin-1-yl)-methyl]-4-methylphenol (L²) binucleating ligands have been synthesized. Complexation of these ligands with Cu(II) perchlorate and appropriate sodium salt offered the binuclear copper(II) complexes, [Cu₂L(X)](ClO₄)₂, (X=Cl, OH and OAc 1–6). Their spectral, electrochemical and magnetic properties have been studied. Two distinct reduction peaks were observed at negative potentials. The electrochemical data shows that the complexes of L² undergo reduction at less negative potential (E¹_pc=−0.15 to −0.25 V, E²_pc=−0.45 to −0.65 V) when compared to the complexes of L¹ (E¹_pc=−0.45 to −0.58 V, E²_pc=−1.07 to −1.103 V). A variable temperature magnetic study on the complexes of the ligand L¹ showed strong antiferromagnetic coupling between the copper atoms (−2J=285–295 cm⁻¹), in contrast, the complexes of the ligand L² showed weak antiferromagnetic interaction (−2J=60–85 cm⁻¹). Electron spin resonance (ESR) spectra (RT) of the complexes of ligand L¹ showed no signal and the complexes of ligand L² showed a broad feature.     

The Efficient Syntheses of Three Novel Bridging Phenanthroline Ligands and Their Binuclear Ruthenium(II) Complexes

Three bridging ligands (L) and their binuclear phenanthroline ruthenium(II) complexes {[Ru(1, 10-phenanthroline)₂]₂(L)}(PF₆)₄ were synthesized and characterized by IR, ¹H NMR, and elemental analysis, where L are 1,8-adipoylamido-bis(1,10-phenanthroline-5-yl) (L₁), 1,11-azelaoylamidobis(1,10-phenanthroline-5-yl) (L₂), and p-phthaloylamido-bis(1,10-phenanthroline-5-yl) (L₃).     

Synthesis and crystal structure of manganese(II) complexes with high-denticity ligands derived from azacrowns

The hepta- and octa-dentate ligands N,N′-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 (L¹) and N,N′-bis(2-aminobenzyl)-1,10-diaza-18-crown-6 (L²), respectively, form stable mononuclear Mn(II) complexes. Spectrophotometric titrations performed in acetonitrile solution indicate the formation of mononuclear Mn(II) complexes with both ligands, and no evidence for the formation of binuclear complexes was obtained. The optimal architecture of L¹ allows it to impose the less usual pentagonal bipyramidal geometry on the Mn(II) guest, and the X-ray crystal structure of [Mn(L¹)](ClO₄)₂ shows that the Mn(II) ion is deeply buried in the receptor cavity, coordinated to the seven available donor atoms, with the perchlorate anions remaining outside the metal coordination sphere. In spite of its higher denticity, the receptor L² is unable to form the expected binuclear complexes. The X-ray crystal structure of [Mn(L²)](NO₃)₂ consists of the [Mn(L²)]²⁺ cation and nitrate anions involved in hydrogen-bonding interactions with the aniline groups. In [Mn(L²)]²⁺ the metal ion is also placed in the crown hole, but as a result of the large size of the macrocyclic cavity only six of the eight available donor atoms of the receptor form part of the Mn(II) coordination sphere, with the Mn(II) ion found in a distorted octahedral coordination environment.     

Electrochemical analysis of the coordination sphere of ruthenium(ii) as electron transfer mediator in glucose oxidase catalysis in aqueous solutions

The redox potentials of the cis-[Ru(LL)₂XY]ⁿ⁺ complexes (LL = 2,2"-bipyridyl (bpy), 1,10-phenanthroline (phen), and 4,4"-dimethyl-2,2"-bipyridyl (Me₂bpy); X, Y = Cl^–, Br^–, CO₃ ^2–, NO₂ ^–, SCN^–, N₃ ^–, H₂O, and DMSO) in aqueous buffer solutions were measured and analyzed in the framework of the Lever theory on the additivity of contributions of ligands (E _L) to the apparent redox potential of the complex (E ^o"). The complexes manifest the properties of reversible or quasireversible redox systems, whose formal redox potentials lie in the 0.2—0.5 V range. The complexes are efficient electron transfer mediators between the active center of glucose oxidase (GO) from Aspergillus niger and an electrode.     

Two trinuclear Ru(II) complexes of hetero-tritopic bridging ligands: synthesis,characterization, theoretical calculations,photophysical and electrochemical properties

Two hetero-tritopic bridging ligands L¹ and L² based on 2,2′-bipyridine and 1,10-phenanthroline moieties, and their corresponding Ru(II) complexes [{Ru(bpy)₂}₃(µ₃?L¹)](PF₆)₆ and [{Ru(bpy)₂}₃(µ₃?L²)](PF₆)₆ (bpy = 2,2′-bipyridine), were synthesized. The molecular structures of both complexes were deduced by ¹H NMR, ESI-MS, ESI-HRMS, elemental analyses, and IR spectroscopy. Quantum calculations on the free bridging ligands and their complexes are also presented. Both complexes display MLCT absorptions at around 454 nm, and emissions at around 613 nm in CH₃CN solution at room temperature and at around 590 nm in EtOH–MeOH glassy matrix at 77 K. Cyclic and differential pulse voltammetry studies of both complexes reveal one reversible Ru(II)-centered oxidation and three reversible ligand-centered reductions, in each case.     

Lanthanum(III) Complexes with N-alk(en)yl-1,10-phenanthroline-2-methyleneamine and their DNA-binding Mode

Five new tridentate ligands and their corresponding La(III) complexes, [La(III)(L)₂(H₂O)_n](ClO₄)₃ where n = 2,3 and 4; L is N-methyl-1,10-phenanthroline-2-methyleneamine (L₁), N-ethyl-1,10-phenanthroline-2-methyleneamine (L₂), N-propyl-1,10-phenanthroline-2-methyleneamine (L₃), N-n-butyl-1,10-Phenanthroline-2-methyleneamine (L₄), and N-benzyl-1,10-phenanthroline-2-methyleneamine (L₅), have been synthesized, and characterized by elemental analysis, IR, far-IR, ¹H-NMR, thermal gravity analysis and conductance measurement. The interaction of the lanthanum(III) complexes with calf thymus DNA was studied by means of UV, fluorescence, CD and viscosity measurements. Using ethidium bromide as a fluorescence probe, the binding mode of the complexes with calf thymus DNA was studied spectroscopically. All the results suggest that the complexes perhaps interact with calf thymus DNA by intercalative and coordination binding mode.     

N-Phenanthroline glycosylamines: synthesis and copper(II) complexes

A series of novel N-(1,10-phenanthrolin-5-yl)-β-glycopyranosylamines was obtained with excellent stereoselectivity and synthetically useful yields by treatment of 5-amino-1,10-phenanthroline with different unprotected monosaccharides, using (NH₄)₂SO₄ as an efficient promoter. Copper(II) complexes having a 2:1 mole ratio of the bidentate ligand phenanthroline N-glycoside and the metal were also prepared.     

Synthesis, thermal stability, electronic features, and antimicrobial activity of phenolic azo dyes and their Ni(II) and Cu(II) complexes

Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L ¹), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L²), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L ³), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L ⁴), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L² and L⁴ were more stable than the other coordination compounds. Among the synthesized ligands, L² and the complexes Cu(L³)₂ and Ni(L⁴)₂ showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms.     

New lead(II) complexes with N,S-ligands,including a lead pyrazolonate with unusual packing flexibility

The reaction of lead(II) acetate in methanol with thiosemicarbazones derived from β-keto esters and β-keto amides (HTSCs) afforded two lead(II) thiosemicarbazonates and numerous homoleptic ([PbL₂]) and/or heteroleptic ([Pb(OAc)L]) complexes containing deprotonated pyrazolones L⁻ formed by metal-induced cyclization of the starting HTSC ligands. All the complexes isolated were characterized by IR spectroscopy in the solid state and by ¹H and ¹³C NMR spectroscopy in DMSO solution; in addition, crystals containing [Pb(L⁶)₂] and [Pb(L⁷)₂] were examined by X-ray crystallography. [Pb(L⁶)₂] · 0.5H₂O · 0.3MeOH (HL⁶ = 4-ethyl-2,5-dihydro-3-methyl-5-oxo-1H-pyrazole-1-carbothiamide) showed three types of molecule with significant structural differences that appear to be determined by packing interactions. In all three molecules the Pb?Pb distances are very short [3.6096(8)–3.7562(8) Å], but density-functional-theoretic calculations at the B3LYP level do not support the existence of Pb–Pb bonds. In [Pb(L⁷)₂] (HL⁷ = N-ethyl-2,5-dihydro-3-methyl-5-oxo-1H-pyrazole-1-carbothiamide) all the molecules are of a single type, and they are linked in a three-dimensional network by weak intermolecular Pb?O bonds.     

Preparation, photophysical, and electrochemical properties of two polynuclear Ru(II) polypyridyl complexes containing imidazole-based ligands

A tripodal ligand L¹ and dipodal ligand L² containing imidazole rings have been synthesized by the reaction of 1,10-phenanthroline-5,6-dione with 2,2??-bipyridine-4,4??-dicarbaldehyde and 4-methyl-2,2??-bipyridine-4??-carbaldehyde, respectively, in the presence of ammonium acetate. Both ligands have two kinds of nonequivalent coordinating sites: one involving the phenanthroline moiety and the other involving the 2,2??-bipyridine moiety. The Ru(II) complexes, [(bpy)₆Ru₃(L¹)](PF₆)₆ and [(bpy)₄Ru₂(L²)](PF₆)₄ (bpy?=?2,2??-bipyridine), have been obtained by refluxing Ru(bpy)₂Cl₂·2H₂O with each ligand in solution. The two complexes display MLCT absorptions at 465 and 480?nm, respectively, and emission at 665 and 675?nm, respectively, in CH₃CN solution. Electrochemical studies of both complexes show one Ru(II)-centered oxidation at around 1.29?V and three ligand-centered reductions.     

Synthesis,crystal structures,spectroscopic studies and antibacterial properties of a series of mononuclear cobalt(III) Schiff base complexes

New complexes of cobalt(III) with the tridentate and tetradentate Schiff base ligands: 3-methoxy-2-{(Z)[(2-hydroxyphenyl)imino]methyl}phenol (H₂L¹), 4-[(2-hydroxyphenyl)imino]-2-pentanone (H₂L²); and 2-((E)-1-(2-((E)-1-(2-hydroxy-4,5-dimethylphenyl)ethylideneamino)ethylimino)ethyl)-4,5 dimethylphenol (H₂L³), namely [Co^III(L¹)(N-MeIm)₃]PF₆ (1), [Co^III(L¹)(py)₃]ClO₄ (2), [Co(L¹)(py)₃][Co(L¹)₂] (3) and [Co^III(L²)(N-MeIm)₃]PF₆ (4) and [Co(L³)(N-MeIm)₂]PF₆ (5), were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of the complexes were determined by X-ray crystallography. In each of these complexes, the cobalt(III) centre has a slightly distorted octahedral environment, utilizing all available coordination centres of the ligands. The complexes were also screened for in vitro antibacterial activities against four human pathogenic bacteria, and their minimum inhibitory concentrations indicated good antibacterial activities.     

Di- and trinuclear Ru(II) complexes of 1,10-phenanthroline and 2,2′-bipyridine derivatives; synthesis,photophysical and electrochemical properties

Three heterotopic ligands L¹, L², and L³ based on 1,10-phenanthroline and 2,2′-bipyridine moieties have been synthesized and characterized. The Ru(II) complexes [{Ru(bpy)₂}₃(µ₃-L¹)](PF₆)₆, [{Ru(bpy)₂}₃(µ₃-L²)](PF₆)₆, and [{Ru(bpy)₂}₂(µ₂-L³)](PF₆)₄ (bpy = 2,2′-bipyridine) have been prepared by refluxing Ru(bpy)₂Cl₂·2H₂O with each ligand in ethanol. All three complexes display MLCT absorptions at around 455 nm and emissions at around 618 nm. Electrochemical studies of the complexes reveal one Ru(II)-centered quasi-reversible oxidation at around 1.32 V and three ligand-centered reductions in each case.     

Synthesis and properties of alkylruthenium complexes bearing primary and secondary amine ligands

A series of 18-electron alkylruthenium complexes, RuR[κ²(N,N′)-(S,S)-R′SO₂NCHPhCHPhNH₂](η⁶-arene) (Ph = C₆H₅, R′ = p-CH₃C₆H₄ and CH₃), bearing a N-sulfonylated diamine ligand was synthesized from the reaction of RuCl[κ²(N, N′)-(S,S)-R′SO₂NCHPhCHPhNH₂](η⁶-arene) with alkylzinc reagents, in which transmetalation proceeded smoothly to give the desired alkyl complexes in good yield and selectivity. Although the isolable amine Ru complexes bearing functionalized alkyl ligands were thermally stable, the simple methyl and ethyl Ru complexes underwent intramolecular deprotonation from NH protons to give the amido Ru complexes with release of the alkanes. The reactivity of the alkyl Ru complexes is highly affected by the structures of the arene ligands.     

Chemical and pharmacological aspects of novel hetero MLB complexes derived from NO2 type Schiff base and N2 type 1,10-phenanthroline ligands

A series of hetero ligand MLB complexes (1–5) were synthesised from tridentate NO₂ type Schiff base [H₂L: (E)-2-((2-hydroxy-4-methoxyphenyl)(phenyl)methyleneamino)benzoic acid; derived from 2-hydroxy-4-methoxybenzophenone and 2-aminobenzoic acid] and bidentate N₂ type 1,10-phenanthroline (B: phen) ligands. The structural characterization of the synthesised MLB complexes were carried out via analytical as well as various spectral studies. Additionally, the low molar conductance values (Λ_m = 14–22 Ω⁻¹ cm² mol⁻¹) imply that the complexes (1–5) are non-electrolytes. The obtained results reinforce that stoichiometry of the mononuclear hetero ligand complexes can be represented as [M(II)-Schiff base(L)-phen(B)·H₂O] and both H₂L and (B) ligands can act as tri and bidentates respectively. Moreover, both the ligands bind with metal(II) ions to build a stable six, six, five membered chelate rings with octahedral geometry. The existing solvent water molecule is confirmed from thermal as well as vibrational analysis. Their microcrystalline nature and uniform surface morphology were confirmed by both powder XRD and SEM studies. 3D molecular modeling and analysis of NiLB and CuLB complexes (3 and 4) were also studied. Mn(II), Ni(II) and Cu(II) complexes (1, 3 and 4) strongly interact with DNA through intercalation binding with strong binding constant values. The obtained K_app values were 5.23, 4.98, 6.36, 7.21 and 4.86 × 10⁵ mol⁻¹ for MLB complexes (1–5) respectively and the negative Δ³G values shown that all the complexes are strongly interact with DNA in a spontaneous manner. Further, remarkable biological, antioxidant and DNA activities were remarkably exhibited by MnLB, NiLB and CuLB complexes.     

Synthesis,Characterization, Electrochemical and Spectroscopic Properties of [Ru(dppt)(bpy)Cl]+ and [Ru(pta)(bpy)Cl]+

Two novel Ru^II complexes [Ru(dppt)(bpy)Cl]ClO₄ (1) and [Ru(pta)(bpy)Cl]ClO₄ (2)[dppt, pta and bpy = 3-(1,10-phenanthrolin-2-yl)-5,6-diphenyl-as-triazine, 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]acenaphthylene and 2,2-bipyridine, respectively] were synthesized and characterized by elemental analysis and electrospray mass spectrometry, ¹H-n.m.r., and u.v.–vis spectroscopy. The redox properties of the complexes were examined using cyclic voltammetry. Due to the strong -accepting character of asymmetric ligands, the MLCT bands of (1) and (2) are shifted significantly to lower energies by comparison with [Ru(tpy)(bpy)Cl]⁺.