Absorption and fluorescence spectroscopy of 3-hydroxy-3-phenyl-1-o-carboxyphenyltriazene and its copper (II), nickel (II) and zinc (II) complexes: a novel fluorescence sensor

Absorption and fluorescence spectroscopic properties of 3-hydroxy-3-phenyl-1-o-carboxyphenyltriazene (HT) are studied. The mechanism of photo-induced electron transfer (PET) followed by energy transfer process of the ligand and the Cu (II), Ni (II) and Zn (II) metal complexes have been investigated. The excited state photo induced intramolecular hydrogen transfer from N-OH to triazene 1-nitrogen atom is explained. The effect of pH, solvent and concentration on the absorption and fluorescence of the ligand is studied and it has been found that the absorption and fluorescence of HT is highly pH, solvent and concentration dependent. Participation of the N-OH proton of HT in the solvent assisted O to N-proton transfer has also been proposed. The fluorescence band shift and changes in intensity is modulated by protonation and complexation with metal ions. This fluorophore can thus be used as a pH dependent and M⁽ⁿ⁺¹⁾⁺/Mⁿ⁺ redox on/off switchable molecular sensor.     

THE SYNTHESIS AND SPECTRAL CHARACTERIZATION OF NEW Cu(II), Ni(II), Co(III), AND Zn(II) COMPLEXES WITH SCHIFF BASE

ABSTRACT

Cu(II), Ni(II), Co(III) and Zn(II) complexes with Schiff base have been prepared. Ligand is derived from condensation of 1,2-bis(p>-aminophenoxy)ethane and 2- hydroxynaphthalin-1-carbaldehyde. The complexes have been characterized by elemental analyses, Λ_M, IR, UV-VIS, ¹H NMR, ¹³C NMR and magnetic measurements. The ligand is coordinated to the central metal as a tetradentade ONNO ligand. The four bonding sites are the azomethine nitrogen and aldehydic -OH groups.     

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: Syntheses,characterization and fluorescence studies

A tetranucleating compartmental Schiff base ligand system has been derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-aminomethylbenzimidazole. Phenoxide bridged later first row transition metal(II) complexes of this ligand have been prepared by conventional sequential route. Ligand and complexes were characterized by routine physicochemical characterizations. The mutual influence of metal centers in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff-bases exhibit fluorescence originating from intraligand (π→π?) transitions. Metal mediated fluorescence enhancement is observed on complexation with Zn(II), whereas metal mediated fluorescence quenching occurs in all other complexes.     

IR- and UV-Spectral Study on the Mechanism of 2-Aminopyridine Complexation with Palladium (II)

Abstract

The IR-spectra of Pd (II) complexes with 2-aminopyridine, obtained both in sulphuric acid and alkaline solution are studied in the region 1700- 1400 cm^?1. The structural conclusions are based on comparison with the IR- and UV-spectra of the free ligand and aminopyridinium sulphate, as well as of trans-dichloro-di-2-aminopyridine-palladium and deuterated at the amino group analogues of the investigated compounds.     

Synthesis,Spectral Characterization,DNA Binding Studies and Antimicrobial Activity of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) Complexes with 4-Aminoantipyrine Schiff Base of Ortho-Vanillin

A series of transition metal complexes of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) have been synthesized involving the Schiff base, 2,3-dimethyl-1-phenyl-4-(2-hydroxy-3-methoxy benzylideneamino)-pyrazol-5-one(L), obtained by condensation of 4-aminoantipyrine with 3-methoxy salicylaldehyde. Structural features were obtained from their FT-IR, UV–vis, NMR, ESI Mass, elemental analysis, magnetic moments, molar conductivity and thermal analysis studies. The Schiff base acts as a monovalent bidentate ligand, coordinating through the azomethine nitrogen and phenolic oxygen atom. Based on elemental and spectral studies six coordinated geometry is assigned to Co(II), Ni(II), Fe(III) and VO(IV) complexes and four coordinated geometry is assigned to Zn(II) complex. The interaction of metal complexes with Calf thymus DNA were carried out by UV–VIS titrations, fluorescence spectroscopy and viscosity measurements. The binding constants (K_b) of the complexes were determined as 5?×?10⁵ M^?1 for Co(II) complex, 1.33?×?10⁴ M^?1 for Ni(II) complex, 3.33?×?10⁵ M^?1 for Zn(II) complex, 1.25?×?10⁵ M^?1 for Fe(III) complex and 8?×?10⁵ M^?1 for VO(IV) complex. Quenching studies of the complexes indicate that these complexes strongly bind to DNA. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. The ligand and it’s metal complexes were screened for their antimicrobial activity against bacteria. The results showed the metal complexes to be biologically active, while the ligand to be inactive.     

Novel Bioactive Co(II), Cu(II), Ni(II) and Zn(II) Complexes with Schiff Base Ligand Derived from Histidine and 1,3-Indandione: Synthesis,Structural Elucidation,Biological Investigation and Docking Analysis

Novel bioactive complexes of Co(II), Cu(II), Ni(II) and Zn(II) metal ions with Schiff base ligand derived from histidine and 1,3-indandione were synthesized and thoroughly characterized by various analytical and spectral techniques. The biological investigations were carried out to examine the efficiency of the binding interaction of all the complexes with calf thymus DNA (CT-DNA). The binding properties were studied and evaluated quantitatively by K_b and K_sq values using UV-visible, fluorescence spectroscopy and voltammetric techniques. The experimental results revealed that the mode of binding of all the complexes with CT-DNA is via intercalation. It is further verified by viscosity measurements and thermal denaturation experiments. From the results of the cleavage study with pUC19 DNA it is inferred that all the complexes possess excellent cleaving ability. The present investigation proved that the binding interaction of all the complexes are significantly strong and the order of binding strength of the complexes is [Ni(L)₂] (K_b = 3.11 × 10⁶ M^?1) > [Co(L)₂] (K_b = 2.89 × 10⁶ M^?1) > [Cu(L)₂] (K_b = 2.64 × 10⁶ M^?1) > [Zn(L)₂] (K_b = 2.41 × 10⁵ M^?1). The complexes were also screened for antibacterial and anticandidal activity. The in vitro cytotoxicity of the ligand and complexes on the NIH/3 T3 mouse fibroblast cell lines were examined using CellTiter-Blue® (CTB) Cell viability assay, which unveiled that all the complexes exhibit more potent activities against NIH/3 T3 cells. Among all the complexes [Zn(L)₂] complex showed the maximum efficiency.     

Two Mn(II) and Zn(II) Coordination Polymers: Aqueous-Phase Detection of Nitroaromatic Explosives and Protective Effect on Atherosclerosis

Via the solvothermal reaction between Zn(II) or Mn(II) salts and 5-(3,4-dicarboxylphenoxy)nicotinic acid (H₃L) ligand, a trifunctional N,O-building block having three diverse kinds of functional groups (O-ether, N-pyridyl and COOH), two new coordination polymers (CPs) could be generated, and their chemical formulae respectively are {[Mn₃(L)₂(H₂O)₂]·4H₂O} (1) and {[Zn(HL)]·NMP} (2). The complex 2 based on Zn(II) possesses high efficiency of fluorescence quenching for the nitrophenol (2,4,6-trinitrophenol, TNP; 4-nitrophenol, 4-NP; 3-nitrophenol, 3-NP; 2-nitrophenol, 2-NP) in the aqueous solution. Furthermore, the treatment activity of compounds on the atherosclerosis was assessed, and relevant mechanism was investigated. First of all, the ELISA assay was used to measure the content of the inflammatory cytokines released into the plasma. Besides, the levels of the NF-κb signaling pathway in the vascular endothelial cells were measured with real time RT-PCR. The hemolysis test was conducted in this research to measure the biocompatibility of the new compound.

     

Calix Receptor Edifice; Scrupulous Turn Off Fluorescent Sensor for Fe(III), Co(II) and Cu(II)

Novel Supramolecular fluorescence receptor derived from calix-system i.e. calix[4]resorcinarene bearing dansylchloride as fluorophore was designed and synthesized. The compound was purified by column chromatography and characterized by elemental analysis, NMR and Mass spectroscopy. Tetradansylated calix[4] resorcinarene (TDCR) shows a boat conformation with C₂v symmetry. The complexation behaviour of metal cations [Ag(I), Cd(II), Co(II), Fe(III), Hg(II), Cu(II), Pb(II), Zn(II), U(VI) (1?×?10^-4?M)] with tetra dansylated calix[4]resorcinarene (1?×?10^-6?M) was studied by spectophotometry and spectrofluorometry. Red shift in the absorption spectra led us to conclude that there is strong complexation Fe(III), Co(II) and Cu(II) with TDCR. These metal cations also produce quenching with red shifts in the emission spectra. The maximum quenching in emission intensity was observed in the case of Fe(III) and its binding constant was also found to be significantly higher than that of Co(II) and Cu(II). Quantum yield of metal complexes of Fe(III) was found to be lower in comparison with Co(II) and Cu(II) complexes. Stern Volmer analysis indicates that the mechanism of fluorescence quenching is either purely dynamic, or purely static.     

Infrared and Raman Spectra of Sulfur-Nitride Complexes of Nickel(II) and Palladium(II)

Abstract

The infrared and Raman spectra of trans-Ni(S₂N₂CH₃)₂ and Pd(S₃N)₂ were measured from 4000-200 cm^?1. The absorption bands were assigned by comparison to the sulfur nitride complexes of nickel(II), palladium(II) and platinum(II). Normal coordinate analyses on these complexes were carried on these data using molecular parameters taken from X-ray data. To aid in band assignments, isotope shift data on trans-⁶²Ni(S₂N₂CH₃)₂ have also been carried out.     

Synthesis,Characterization Luminiscence Studies and Microbial Activity of Ethylenediamine Ruthenium (II) Complexes with Dipyridophenazine Ligands

Three symmetric ligands 7-methyl dipyrido-[3,2-a;2′,3′-c]phenazine (dppz-CH₃), 7-nitro dipyrido-[3,2-a;2′,3′-c]phenazine (dppz-NO₂) and benzo[i]dipyrido-[3,2-a;2′,3′-c]phenazine (dppn) and their ruthenium(II) complexes [Ru(en)₂(L)][ClO₄]₂ (en= ethylenediamine), L= dppz-CH₃, dppz-NO₂ and dppn have been synthesized and characterized by IR, ¹H, ¹³C NMR and Mass spectra. The interactions of these complexes with calf thymus DNA have been investigated by spectrophotometric, spectrofluorimetric, circular dichroism, viscosity and thermal denaturation studies. As the planar extension of the intercalative ligand increases, the interaction of the complex with DNA increases, indicating that the size and shape of the intercalalative ligand has a marked effect on the strength of interaction. The plot of log K versus log [Na⁺] yield a slope of -1.26, -1.53, -1.60 for the complexes 1, 2 and 3 respectively. These three complexes have been found to promote the cleavage of plasmid pBR 322 DNA upon irradiation.     

Infrared Spectra of the Copper(II), Nickel(II) and Palladium(II) Complexes of 4-amino-3-pentene-2-one

Abstract

The infrared spectra of the metal complexes of 4-amino-3-pentene-2-one were measured from 4000 - 20 cm^?1. The absorption bands were assigned by comparison to other similar molecules: The Cu(II) complex of 4-methylamino-3-pentene-2-one, and complexes of acetylacetone. Force constants for the molecules were calculated using the A_xsm matrix method. The spectra were measured at 298^oK and 77^oK.     

Synthesis and Characterization of New Cationic Fe(III),Co(II) and Ni(II) Complexes Containing Isatin/Triphenylphosphine Mixed Ligands

New cationic Fe(III),Co(II) and Ni(II) mixed ligand complexes containing both triphenylphosphine and isatin ligands were prepared and characterized using conventional physical and chemical methods of analysis

(I.R., UV-Vis., and ¹H NMR). Microanalytical data of the investigated complexes are consistent with the formulations. [Fe(Isa)₂ {P(Ph)₃}₂]³⁺, [Co(Isa)₂ {P(Ph)₃}₂]²⁺ and [Ni(Isa)₂ {P(Ph)₃}₂]²⁺, (Where Isa = Isatin and P(Ph)₃ = Triphenylphosphine).

The prepared complexes are soluble in polar solvents and could be of potential use in bio-inorganic applications.     

A Co-Crystallised Cobalt(II) Cluster of Pyridinedicarboxylic Acid (PDC) as a Luminescent Material for Selective Sensing of Methanol

A luminescent Cobalt(II) co-crystal [Co₁₃(PDC)₁₆(H₂O)₂₄.7H₂O] 1 (where H₂PDC?=?2,6-pyridinedicarboxylic acid) have been prepared by oven-heating and slow evaporation of solvent. Single crystal X-ray diffraction (SCXRD) analysis revealed that 1 is a mixture of complexes that crystallizes in the triclinic space group P-1 and the geometry around the Co(II) ions is octahedral. The structure is extensively imbued with hydrogen bonding that helps in stabilizing the complex. Thermogravimetric analysis indicates that 1 is thermally stable up to 364 ^οC. The luminescence properties of 1 revealed a strong emission centered at 437 nm (λex?=?345 nm) assigned to ligand to metal charge transfer (LMCT). The luminescence sensing of 1 towards volatile organic molecules were also examined. However, 1 displayed a turn off towards methanol compared to other molecules with high quenching efficiency and low limit of detection (3.5?×?10^?4 vol%). The results show excellent selectively and high sensitivity. Powder X-ray diffraction studies revealed that the structural integrity of the complex was maintained after exposure to methanol vapour. Theoretical studies also revealed small binding energy (?413.2 au) and low energy gap (1.19) for 1-CH₃OH adduct.

     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Toxic Activity of Cobalt(III) and Ruthenium(II) Polypyridyl Complexes

The new ligand 4-(isopropylbenzaldehyde)imidazo[4,5-f ][1,10]phenanthroline (ippip) and its complexes [Ru(phen)₂(ippip)]²⁺(1),[Co(phen)₂(ippip)]³⁺(2),[Ru(bpy)₂(ippip)]²⁺(3),[Co(bpy)₂(ippip)]³⁺(4)(bpy=2,2-bipyridine) and (phen=1,10-phenanthroline) were synthesized and characterized by ES⁺-MS, ¹H and ¹³C NMR. The DNA binding properties of the four complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that complexes bind to calf thymus DNA (CT-DNA) through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than 2, 3, 4 complexes under comparable experimental conditions. Furthermore, photocleavage studies reveal that singlet oxygen (¹O₂) plays a significant role in the photocleavage.     

The Smart 2-(2-Fluorobenzoyl)-N-(2-Methoxyphenyl)Hydrazinecarbothioamide Functionalized as Ni(II) Sensor in Micromolar Concentration Level and its Application in Live Cell Imaging

In recent years, fluorescent probes for the detection of environmentally and biologically important metal cations have received extensive attention for designing and development of fluorescent chemosensors. Herein, we report the photophysical results of 2-(2-fluorobenzoyl)-N-(2-methoxyphenyl) hydrazinecarbothioamide (4) functionalized as Ni (II) sensor in micromolar concentration level. Through fluorescence titration at 488 nm, we were confirmed that ligand 4 showed the remarkable emission by complexation between 4 and Ni (II) while it appeared no emission in case of the competitive ions (Cr³⁺, Fe²⁺, Co²⁺, Ba²⁺, Cu²⁺, Ca²⁺, Na⁺, K⁺, Cu⁺, Cs⁺). Furthermore, ligand 4 exhibited no toxicity with precise cell permeability toward normal living cells using L929 cell lines in bio imaging experiment investigated through confocal fluorescence microscope. The non-toxic behavior of ligand 4 (assessed by MTT assay) and its ability to track the Ni²⁺ in living cells suggest its possibility to use in biological system as nickel sensor.

Vibrational Parameters of Some Mixed Tetracoordinate Halogenomercurate(II) Complexes

Abstract

The normal coordinate analysis has been performed for the mercury(II) halogeno complexes HgX₃Y²? (X≠Y=C1, Br, I) using latest Raman spectral data for the first time. The general quadratic valence force field has been used in this study. The results in turn are utilized to investigate the useful vibrational parameters such as compliance constants and mean amplitudes of vibration. The trends among the vibrational parameters are discussed and the bond properties of the mercury(II) and related complexes are examined.     

New Bio-Based Cu(II) Complexes and Study of their Anti-Cancer Activities

Two new Cu(II) complexes with Picolinic acid and Tryptophan [Cu(II)(DPTR)(H₂O)₂](1:1) (1) and [Cu(II)(DPTR)(Phen)] (1:1:1) (2) were synthesized, characterized and studied their DNA binding, cleavage, docking and anti-cancer properties. The molecular modeling studies were carried out with energy minimized structures of metal complexes. CT-DNA binding studies revealed that the complexes bind through an intercalative mode and show good binding propensity. The docking study also confirms the intercalative mode of binding. The hydrolytic DNA cleavage activity of these complexes has been studied using gel electrophoresis. Complex 2 shows better efficiency than 1. Cell viability experiments indicated that the ligand, complexes show significant dose dependent cytotoxicity in selected cell lines.

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Graphical Abstract Two new Cu(II) complexes with Picolinic acid and Tryptophan, [Cu(II)(DPTR)(H₂O)₂](1:1) (1) and [Cu(II)(DPTR)(Phen)] (1:1:1) (2) were synthesized, characterized and studied their DNA binding, cleavage, docking and anti-cancer properties.

     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Spectral and luminescent investigations of ammonia cyclometalated Pt(II) complexes

A method of synthesis of ammonia cyclometalated Pt(II) complexes [Pt(NH₃)₂C∧N]ClO₄, where C∧N is 2-phenylpyridinate or 2-phenylbenzothiazole ion, is developed. The electronic absorption and emission properties of the complexes are studied. It is found that the state responsible for intense long-lived luminescence is the excited charge-transfer state of the ³(d-π*) type, the π* orbital being localized at the corresponding cyclometalating ligand. Formation of platinum blue is observed in air-saturated aqueous solutions of ammonia cyclometalated complexes.     

Synthesis and Antitumor,Antioxidant Effects Studies of N-Ethylpiperazine Substitute Thiourea Ligands and Their Copper(II) Complexes

A series of N-ethylpiperazine substitute thioureas [C₆N₂H₁₃NHCSNHR], where R = -C₃H₅ (L ₁ ), -C₁₀H₇ (L ₂ ), and -C₇H₇ (L ₃ ), and their copper (II) complexes have been synthesized. These ligands and complexes have been characterized by elemental analyses, IR, ¹H and ¹³C-NMR spectra, UV-Vis, magnetic susceptibility, thermogravimetrical analyses, and MALDI-TOF MS. In vitro antitumor activity of ligands and their complexes has been screened toward several tumor cell lines. The effects on these complexes of the growth of L1210 and MCF7 were studied comparatively with that of free ligands. Antioxidant and radical scavenging activities of synthesized compounds were determined by various in vitro assays including 1,1-diphenyl-2-picryl-hydrazyl free radicals (DPPH), 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radicals (ABTS+), and ferrous ion (Fe²⁺) chelating activities. Moreover, these activities were compared to synthetic and standard antioxidant trolox. The results showed that the synthesized compounds had effective antioxidant power.