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.     

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.     

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.     

Synthesis and luminescent properties of Cu(II), Zn(II) polymeric complexes with electron- and hole-transporting groups

A novel ligand 3,6-bis(1,10-phenathroline-[5,6-d] imidazole-2-yl)carbazole (Bpic) containing hole- and electron-transporting groups was firstly designed. Its polymeric complexes of Bpic with Cu(∥), Zn(∥) were successfully synthesized. The UV-vis absorption, fluorescence spectra and thermal properties of these complexes were investigated. At room temperature, complexes 2, 3 emit blue luminescence from 445 to 485 nm in DMSO solution, and emit green/yellow and orange luminescence from 523 to 585 nm in solid state. In comparison with the free ligand, the polymeric complexes exhibit a bathochromic shift. It can be assigned to the extended π-conjugation of the complexes.     

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.     

Crystal Structures, Interactions with Biomacromolecules and Anticancer Activities of Mn(II), Ni(II), Cu(II) Complexes of Demethylcantharate and 2-Aminopyridine

Three novel transition metal complexes (Hapy)(2)[M(DCA)(2)]·6H(2)O (M?=?Mn(II) (1), Ni(II) (2), Cu(II) (3); DCA?=?demethylcantharate, 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylate, C(8)H(8)O(5); Hapy?=?2-aminopyridine acid, C(5)H(7)N(2)) were synthesized and characterized by elemental analysis, infrared spectra, thermogravimetric analysis and X-ray diffraction. DNA binding properties of the complexes were investigated by electronic absorption spectra, fluorescence spectra and viscosity measurements. Results indicated the complexes could bind to DNA through partial intercalation mode with binding constants K ( b )/(L·mol(-1)) of 1.91?×?10(4) (1), 5.13?×?10(4) (2) and 1.12?×?10(5) (3) at 298?K. Meanwhile, the interactions of the complexes with BSA were also studied by fluorescence spectra. The results suggested that the complexes could quench the fluorescence of BSA through static quenching with the binding constants K ( A )/(L·mol(-1)) of 1.44?×?10(6) (1), 1.14?×?10(7) (2) and 2.98?×?10(4) (3). And the main contribution was tryptophan residues of BSA. The antiproliferative activity test revealed that complexes showed more intense inhibition ratios against human hepatoma cells lines and human gastric cancer cells lines in vitro. Copper(II) complex (3) possesses the strongest inhibition ratio against human hepatoma cells.     

Spectral and luminescent properties of mixed-ligand complexes of palladium(II) and 7,8-benzoquinoline

Spectral and luminescent properties of mixed-ligand palladium(II) complexes—[PdBhq(μ-Cl)]₂, [PdBhqEn]ClO₄, and [PdBhqBpy]ClO₄, where Bhq stands for the 7,8-benzoquinoline ion—were studied. The absorption spectra of these complexes in the 25000–40000-cm^? range were found to have a number of spin-allowed transitions of the ₁(π-π*) type involving orbitals of the 7,8-benzoquinoline ligand. The luminescent characteristics of these compounds in a glass-forming matrix at 77 K are primarily determined by the participation of the ₃(π-π*) states of the 7,8-benzoquinoline ligand.     

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.     

On/off spin-crossover phenomenon and control of the transition temperature in assembled Iron(II) complexes

The present study reveals the on/off of spin-crossover (SCO) phenomenon in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand. Whether SCO phenomenon occurs or not in assembled Fe(II) complexes bridged by bis(pyridyl) type ligand is determined by local structure around iron atom. SCO phenomenon occurs when the coordinating pyridines facing to each other across the iron atom are propeller type, while the phenomenon does not occur when they are parallel type or distorted propeller type. DFT calculation explained that, in the shortening of Fe-pyridine bonds when changing from high-spin state to low-spin state, the pyridines of propeller type can approach the iron atom with smaller steric hindrance than those of parallel and distorted propeller type complexes. The local structure is controlled by introducing methyl substituent and introducing π-system, changing SCO phenomenon. And the transition temperature of SCO is also controlled in assembled complexes bridged by 1,2-bis(4-pyridyl)ethane by mixing anionic ligand.     

DNA Binding,Cleavage and Antibacterial Activity of Mononuclear Cu(II), Ni(II) and Co(II) Complexes Derived from Novel Benzothiazole Schiff Bases

A series of novel bivalent metal complexes M(L₁)₂ and M(L₂)₂ where M = Cu(II), Ni(II), Co(II) and L₁ = 2-((benzo [d] thiazol-6-ylimino)methyl)-4-bromophenol [BTEMBP], L₂ = 1-((benzo [d] thiazol-6-ylimino)methyl) naphthalen-2-ol [BTEMNAPP] were synthesized. All the compounds have been characterized by elemental analysis, SEM, Mass, ¹H NMR, ¹³C NMR, UV–Vis, IR, ESR, spectral data and magnetic susceptibility measurements. Based on the analytical and spectral data four-coordinated square planar geometry is assigned to all the complexes. DNA binding properties of these complexes have been investigated by electronic absorption spectroscopy, fluorescence and viscosity measurements. It is observed that these binary complexes strongly bind to calf thymus DNA by an intercalation mode. DNA cleavage efficacy of these complexes was tested in presence of H₂O₂ and UV light by gel electrophoresis and found that all the complexes showed better nuclease activity. Finally the compounds were screened for antibacterial activity against few pathogens and found that the complexes have potent biocidal activity than their free ligands.     

Synthesis,Characterization, DNA Binding Properties,Fluorescence Studies and Antioxidant Activity of Transition Metal Complexes with Hesperetin-2-hydroxy Benzoyl Hydrazone

A novel Schiff-base ligand (H₅L), hesperetin-2-hydroxy benzoyl hydrazone, and its copper (II), zinc (II) and nickel (II) complexes (M·H₃L) [M(II) = Cu, Zn, Ni], have been synthesized and characterized. The ligand and Zn (II) complex exhibit green and blue fluorescence under UV light and the fluorescent properties of the ligand and Zn (II) complex in solid state and different solutions were investigated. In addition, DNA binding properties of the ligand and its metal complexes have been investigated by electronic absorption spectroscopy, fluorescence spectra, ethidium bromide displacement experiments, iodide quenching experiments, salt effect and viscosity measurements. Results suggest that all the compounds bind to DNA via an intercalation binding mode. Furthermore, the antioxidant activity of the ligand and its metal complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro. The metal complexes were found to possess potent antioxidant activity and be better than the free ligand alone and some standard antioxidants like vitamin C and mannitol.     

Spectroscopic and electrochemical properties of dichlorobenzoquinoline complexes of Au(III), Pt(II), and Pd(II)

The dichloride complexes of Au(III), Pt(II), and Pd(II) with 2,2′-biquinoline are obtained and characterized by ¹H NMR spectroscopy, electronic spectroscopy, and cyclic voltammetry. It is shown that the low efficiency of the metal-ligand (2,2′-biquinoline) interaction leads to almost the same positions of the intraligand bands in the absorption and fluorescence spectra of the complexes and to the closeness of their reduction potentials.     

Spectral and luminescent specific features of phenylpyridine ethylenediamine complexes of Pt(II), Pd(II), and Au(III)

The orbital nature and basic photophysical parameters of phenylpyridine ethylenediamine complexes of Pt(II), Pd(II), and Au(III) are found from the comparative analysis of absorption and luminescence spectra and the luminescence decay kinetics. The orbital nature and properties of the lowest excited states responsible for luminescence are shown to depend on the type of metal and the energy of singlet-triplet splitting.     

Infrared Studies on the Complexes of Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) with 5-Benzylthio-1,2,4.-triazole

Zn(II), Cd(II), Hg(II), Pb(II), Cu(I) and Ag(I) complexes of 5-benzylthio-1,2,4-triazole (BTT) have been prepared and characterised on the basis of analytical and IR data. Hg(II), Cd(II), Zn(II), and Pb(II) complexes are assigned tetrahedral structure with polymeric intermolecular linkages through S and N atoms while Ag(I) and Cu(I) are proposed to have polymeric linear structure     

Studies on Cu(II), Zn(II), Ni(II) and Co(II) complexes derived from two dipeptide Schiff Bases

Some new metal complexes of two dipeptide Schiff bases derived from salicylaldehyde and dipeptides such as glycyl-DL-alanine and glycyl-DL-phenylalanine have been synthesized and characterized by elemental analysis, molar conductance, IR, UV spectra, TG and DTA studies. The COO stretching bands in IR spectra suggest that the carboxylate acts as a monodentate group when binding with metal. The ligands are coordinated to the central metal as tetradentate ligands. The bonding sites are the carboxylate oxygen, imino nitrogen, amide nitrogen and phenolic oxygen.     

Structural, vibrational, thermal and magnetic investigation of novel Co(II), Cu(II), Zn(II) and Hg(II) crystalline metal complexes with 2-amino-5-benzylmercapto-1,3,4-thiadiazole: a low weight model of protonated copolymer resin

The 2-amino-5-benzylmercapto-1,3,4-thiadiazole (C₉H₉N₃S₂) is a low weight model of a protonated copolymer resin used as a metal uptake agent. New monomeric crystalline metal complexes of C₉H₉N₃S₂ with Co(II), Cu(II), Zn(II) and Hg(II) were synthesized and investigated in order to facilitate the interpretation of the metal/resin binding mode. These materials have been studied by single crystal X-ray Diffraction and FTIR Spectroscopy at room temperature. Crystal data for these triclinic phases are reported. All frameworks consist of discrete monomeric units that provide crystalline stability through a network of hydrogen bond interactions. The Co(II), Zn(II) and Hg(II) ions are surrounded by a tetrahedral arrangement of two thioether monodentate ligands (each one coordinating by a N(1)_thiadiazole atom) and two chlorine atoms. The Cu(II) ion is coordinated by four thioether monodentate ligands (each one coordinating by a N(1)_thiadiazole atom) and one chlorine atom as nearest neighbor in a distorted square pyramidal polyhedron. The spectroscopic data are consistent with the structural model. FTIR spectra evidence changes in the H-bonds in the crystal packing when coordination with these divalent ions is present. Magnetic susceptibility at room temperature for Cu(II) and Co(II) complexes, EPR spectrum at room temperature for Cu(II) complex and thermal properties for all complexes were measured. These results could be useful for the interpretation of the binding mode of M(II)/1,3,4-thiadiazole-2-amino-5-thiol in protonated copolymer resin which are used as uptake agents of toxic metallic ions.     

Quantum yield and photometric parameters of some transition metal ion schiff base complexes

In the present studies, a series of transition metal Ni(II), Mn(II), Co(II) and Cu(II) complexes were synthesized using a Schiff base ligand formed by condensation reaction of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde. The prepared ligand and complexes were characterized by FTIR, HNMR, UV–Vis and fluorescence techniques. The peak in the HNMR spectra as well as important band in the FTIR spectra is discussed in relation to the molecular structure. Quantum yield of the prepared samples was calculated by taking quinine sulphate as a reference solvent. The quantum yield and fluorescence intensity of Ni(II), Mn(II) and Co(II) complexes were found to be more compared to Cu (II) complex and ligand. The photometric parameters were also calculated for ligand and complexes.     

Synthesis,Characterization and Antibacterial Activity of Some Transition Metal Complexes of 2-N-(isatinamino)-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene

Metal complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) with a Schiff base derived from isatin and 2-amino-3-carboxyethyl-4,5,6,7-tetrahydrobenzo[b]thiophene were synthesised and characterised by elemental analysis, conductance measurements, magnetic susceptibility, UV-Vis, IR, ¹H NMR and EPR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate, coordinating to the metal ion through the azomethine nitrogen, ester carbonyl and carbonyl oxygen of the isatin moiety. The EPR spectral data indicated that metal-ligand bonds have considerable covalent character. The copper(II) complex was subjected to X-ray diffraction and cyclic voltammetric studies. The ligand and the metal complexes were screened for their antibacterial activity and it has been observed that the metal complexes are more potent bactericides than the ligand.     

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.     

Dielectric studies of a bioactive tetramic acid and its complexes with Cu(II) and Co(II)

The 3-acyl tetramic acids constitute a growing class of natural products displaying a range of biological activities. The g , g ' tricarbonyl moiety present in the 3-acyl tetramic acid provides a suitable site for bidentate complexation to a metal, which increases the biological activity. For the dielectric study of N-acetyl-3-butanoyl tetramic acid and a series of its complexes with Cu(II) and Co(II) in symmetric and asymmetric forms, we used the Thermally Stimulated Depolarization Currents (TSDC) technique. The drastic decrease of the intensity of the TSDC peaks of the symmetric and asymmetric complexes, compared to the above mentioned ligand, suggested that the polarizability of the side groups is considerably reduced. This result enhances the proposed complexation mode of the ligand through oxygen next to carbons 3 and 4 of the 5-member ring.