A Chromone-Derived Schiff-Base Ligand as Al(3+) "Turn on" Fluorescent Sensor: Synthesis and Spectroscopic Properties.

In this study, a novel chromone-derived Schiff-base ligand called 6-Hydroxy-3-formylchromone (2'-furan formyl) hydrazone (HCFH) has been designed and synthesized as a "turn on" fluorescent sensor for Al(3+). This sensor HCFH showed high selectivity and sensitivity towards Al(3+) over other metal ions investigated, and most metal ions had nearly no influences on the fluorescence response of HCFH to Al(3+). Additionally, the significant enhancement by about 171-fold in fluorescence emission intensity at 502 nm was observed in the presence of Al(3+) in ethanol, and it was due to the chelation-enhanced fluorescence (CHEF) effect upon complexation of HCFH with Al(3+) which inhibited the photoinduced electron transfer (PET) phenomenon from the Schiff-base nitrogen atom to chromone group. Moreover, this sensor formed a 1 : 1 complex with Al(3+) and the fluorescence response of HCFH to Al(3+) was nearly completed within 1 min. Thus, this sensor HCFH could be used to detect and recognize Al(3+) for real-time detection.

A highly selective turn-on fluorescent chemosensor for zinc ion in aqueous media.

In the paper, a novel rhodamine6G based fluorescent chemosensor bearing 3-carbaldehyde chromone was designed and synthesized. According to the fluorescence behavior toward several metal ions, it showed highly selectivity and sensitivity to Zn(II) over other commonly coexistent metal ions (Cu(II), Cd(II), Hg(II), Mg(II), K(I), Pb(II), Fe(III) and Cr(III)) in aqueous environment (pH = 7.4). Meanwhile the binding constant between Zn(II) and chemosensor achieved 6.21 × 10(11) M(-1) in aqueous media. Moreover, according to the Job plot, 1:1 stoichiometry between Zn(II) and sensor was deduced in aqueous media (pH = 7.4). The good selectivity and sensitivity in aqueous media effectively enhanced the application value of the fluorescent chemosensor for Zn(II).

Synthesis, characterization, DNA binding properties and antioxidant activity of Ln(III) complexes with Schiff base ligand derived from 3-carbaldehyde chromone and aminophenazone.

A novel Schiff base ligand, chromone-3-carbaldehyde-aminophenazone (L) and its Ln(III) (Ln = La, Yb) complexes were synthesized and characterized by physicochemical methods. The interaction between the ligand, Ln(III) complexes and calf thymus DNA in physiological buffer (pH=7.10) was investigated by using UV-vis spectroscopy, fluorescence spectra, ethidium bromide experiments and viscosity measurements, indicating that the studied compounds can all bind to DNA via an intercalation binding mode and the complexes have stronger binding affinity than the free ligand alone. Furthermore, antioxidant activity of the ligand and its complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro, suggesting that Ln(III) complexes inhibit stronger antioxidant activity than the ligand alone and some standard antioxidants, such as mannitol and vitamin C.

Synthesis, characterization and DNA-binding properties of Ln(III) complexes with 6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone.

A novel 6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone (L) and its Ln(III) complexes, [Ln = Sm (1), Eu (2), Gd (3), Tb (4)], have been synthesized and characterized. The fluorescence properties of the Eu(III) and Sm(III) complexes in solid state and Eu(III) complex in different solutions (DMF, DMSO, methanol and acetonitrile) were investigated. At the same time, the DNA-binding properties of the two complexes are investigated using UV-Vis absorption spectroscopy, fluorescence spectroscopy, viscosity measurement. All the experimental evidences indicate that the two complexes can bind to CT-DNA via an intercalation mechanism. Furthermore, antioxidant activity tests in vitro showed that the complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction.

Synthesis, characterization, antioxidant activity and DNA-binding studies of two rare earth(III) complexes with naringenin-2-hydroxy benzoyl hydrazone ligand.

Two novel rare earth complexes, Y(III) complex (1) and Eu(III) complex (2), with naringenin-2-hydroxy benzoyl hydrazone ligand were synthesized and characterized. The interaction of the two metal complexes and the free ligand with calf thymus DNA (CT DNA) was investigated by electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurement. All the experimental evidences indicate that these three compounds can strongly bind to CT DNA via an intercalation mechanism. The intrinsic binding constants of the Y(III) complex (1), Eu(III) complex (2) and the free ligand with CT DNA were 2.1 x 10(4), 8.5 x 10(4) and 1.6 x 10(4) M(-1), respectively. Furthermore, the antioxidant activity of the metal complexes was determined by hydroxyl radical scavenging method in vitro.

Synthesis, crystal structure and DNA-binding studies of the Ln(III) complex with 6-hydroxychromone-3-carbaldehyde benzoyl hydrazone.

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand (L) and its Ln(III) complexes, [Ln=La(1) and Sm(2)], have been prepared and characterized. The crystal and molecular structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Antioxidative activity tests in vitro showed that L and its complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction and also oxygen free radicals, and that the effect of the La(III) complex 1 is stronger than that of mannitol and the other compounds. The compounds were tested against tumor cell lines including HL-60 and A-549. The data shows that the suppression rate of complexes 1 and 2 against the tested tumor cells are superior to the free ligand (L). The interactions of complexes 1 and 2, and L, with calf thymus DNA were investigated by UV-visible (UV-vis), fluorescence, denaturation experiments and viscosity measurements. Experimental results indicated that complexes 1 and 2, and L can bind to DNA via the intercalation mode, and that the binding affinity of complex 1 is higher than that of complex 2 and of free ligand (L). The intrinsic binding constants of complexes 1 and 2, and L were (7.62+/-0.56)x10(6), (3.70+/-0.47)x10(6) and (2.41+/-0.46)x10(6)M(-1), respectively.

Infrared and DNA-binding on ultraviolet and fluorescence spectra of new copper and zinc complexes with a naringenin Schiff-base ligand.

A naringenin Schiff-base ligand (H(3)L) and its copper(II) and zinc(II) complexes have been synthesized and characterized by elemental analyses, molar conductivities, (1)H NMR, IR spectra, UV spectra and thermal analyses. The DNA-binding properties of the Cu(II) and Zn(II) complexes have been investigated by fluorescence spectroscopy, ultraviolet spectroscopy and by viscosity measurements. The results indicate that complexes and ligand may bind to DNA by intercalation modes, but the binding affinity of the complexes is much higher than that of the ligand.

Spectra and DNA-binding affinities of Copper(II), Nickel(II) complexes with a novel glycine Schiff base derived from chromone.

New [CuL.(H(2)O)(3)]NO(3).H(2)O and [NiL.H(2)O]NO(3).2H(2)O complexes with Schiff base (LNa) derived from 6-hydroxy-3-carbaldehyde chromone (CDC) and glycine are reported. Two complexes have been characterized by elemental analysis, IR data, TG/DTA and molar conductivity. The binding of these two complexes to calf thymus DNA (CT-DNA) has been investigated, respectively, with UV-vis spectroscopy, fluorescence spectroscopy and viscosity measurements. The experiment results indicate that the two complexes may bind to CT-DNA through an intercalative mode and [CuL.(H(2)O)(3)]NO(3).H(2)O intercalates into DNA more deeply than [NiL.H(2)O]NO(3).2H(2)O. Their intrinsic binding constants (K) with DNA are 6.08 x 10(5) and 2.76 x 10(5)M(-1).

Synthesis, structure, infrared and fluorescence spectra of new rare earth complexes with 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone.

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand and its four complexes, [LnL2(NO3)2]NO3 [Ln = Eu(1), Sm(2), Tb(3), Dy(4)], were synthesized. The complexes were characterized by the elemental analyses, molar conductivity and IR spectra. The crystal and molecular structure of Sm(III) complex was determined by single-crystal X-ray diffraction: crystallized in the triclinic system, space group P-1, Z = 1, a = 11.037(4) A, b = 14.770(5) A, c = 15.032(7) A, alpha = 60.583(4), beta = 75.528(7), gamma = 88.999(4), R1 = 0.0349. The fluorescence properties of complexes in the solid state and in the organic solvent were studied in detail, respectively. Under the excitation of ultraviolet light, strong red fluorescence of solid europium complex was observed. But the green fluorescence of solid terbium complex was not observed. These observations show that the ligand favor energy transfers to the emitting energy level of Eu3+. Some factors that influence the fluorescent intensity were also discussed.

ß-Hydroxy-α-naphthaldehyde [2-(quinolin-8'-yloxy) acetyl] hydrazone as an efficient fluorescent chemosensor for Mg2+.

An efficient fluorescent sensor based on ß-hydroxy-α-naphthaldehyde [2-(quinolin-8'-yloxy) acetyl] hydrazone (HL) for Mg2+ has been designed and synthesized. The receptor showed "off-on" fluorescent responses toward Mg2+ in acetonitrile. The reasons for this phenomenon is that the addition of Mg2+ to the solution of HL induce the formation of a 1:1 ligand-metal complex which inhibit excited-state intramolecular proton transfer (ESIPT).

Fluorescent sensor for selective detection of Al(3+) based on quinoline-coumarin conjugate.

A fluorescence probe, 8-formyl-7-hydroxyl-4-methyl coumarin - (2'-methylquinoline-4-formyl) hydrazone (L) has been synthesized. The chemosensor is found preferential binding to Al(3+) in presence of other competitive ions with associated changes in its optical and fluorescence spectra behavior. Upon addition of Al(3+) to a solution of L, it shows 200-fold enhancement of fluorescence intensity which might be attributed to form a 2:1 stoichiometry of the binding mode of LAl(III) and the chelation enhanced fluorescence (CHEF) process at 479nm in ethanol. The lowest detection limit for Al(3+) is determined as 8.2×10(-7)M.

A colorimetric and turn-on fluorescent chemosensor for Al(III) based on a chromone Schiff-base.

A simple Schiff-base receptor 7-methoxychromone-3-carbaldehyde-(pyridylformyl) hydrazone (MCNH) was prepared. It exhibits an "off-on-type" mode with high sensitivity in the presence of Al(3+). This compound could be used as Al(3+) probe in ethanol and it features visible light excitation (433 nm) and emission (503 nm) profiles. Upon binding of Al(3+), a significant fluorescence enhancement with a turn-on ratio over 800-fold was triggered. However, other metal ions had no such significant effect on the fluorescence. MCNH can also be used as a colorimetric chemosensor for Al(3+), which is easily observed from colorless to yellow-green by the naked-eye. The detection limit of MCNH for Al(3+) was as low as 1.9×10(-7) M.

A new cyclic supramolecular Zn(II) complex derived from a N2O2 oxime chelate ligand with luminescence mechanochromism.

A new Zn(II) complex was synthesized based on a new Salen-type tetradentate N2O2 bisoxime chelate ligand (H2L) derived from 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and 1,2-bis(aminooxy)ethane. Single-crystal X-ray diffraction analysis reveals that the structure of the Zn(II) complex features a three-dimensional (3D) cyclic supramolecular system via intermolecular hydrogen bonds. Moreover, the solid-state photoluminescent properties demonstrate that the Zn(II) complex exhibits unusual luminescence mechanochromism tuned by CH3OH.

A highly selective chemosensor for Al3+ based on 2-oxo-quinoline-3-carbaldehyde Schiff-base.

A new Schiff-base ligand (1) with good fluorescence response to Al(3+), derived from 2-oxo-quinoline-3-carbaldehyde and nicotinic hydrazide, had been synthesized and investigated in this paper. Spectroscopic investigation revealed that the compound 1 exhibited a high selectivity and sensitivity toward Al(III) ions over other commonly coexisting metal ions in ethanol, and the detection limit of Al(3+) ions is at the parts per billion level. The mass spectra and Job's plot confirmed the 1:1 stoichiometry between 1 and Al(3+). Potential utilization of 1 as intracellular sensors of Al(3+) ions in human cancer (HeLa) cells was also examined by confocal fluorescence microscopy.

An effective Cu(II) quenching fluorescence sensor in aqueous solution and 1D chain coordination polymer framework.

In the article, a novel fluorescent probe for the copper cation based on fluorescence quenching mechanism was designed. It exhibited high selectivity for Cu(II) over other common metal ions in aqueous media. Furthermore the coordination between Cu(II) and the organic molecule sensor fabricated an interesting 1D chain coordination polymer framework.

Crystal structures, DNA-binding and cytotoxic activities studies of Cu(II) complexes with 2-oxo-quinoline-3-carbaldehyde Schiff-bases.

Three novel 2-oxo-quinoline-3-carbaldehyde Schiff-bases and their Cu(II) complexes were synthesized. The molecular structures of Cu(II) complexes were determined by X-ray crystal diffraction. The DNA-binding modes of the complexes were also investigated by UV-vis absorption spectrum, fluorescence spectrum, viscosity measurement and EB-DNA displacement experiment. The experimental evidences indicated that the ligands and Cu(II) complexes could interact with CT-DNA (calf-thymus DNA) through intercalation, respectively. Comparative cytotoxic activities of ligands and Cu(II) complexes were also determined by MTT [3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide] and SRB (sulforhodamine B) methods. The results showed that the three Cu(II) complexes exhibited more effective cytotoxic activity against HL60 cells and HeLa cells than corresponding ligands. Also, CuL(3) showed higher cytotoxic activity than CuL(1) and CuL(2).

Synthesis, crystal structure, DNA interaction and antioxidant activities of two novel water-soluble Cu2+ complexes derivated from 2-oxo-quinoline-3-carbaldehyde Schiff-bases.

Two novel 2-oxo-quinoline-3-carbaldehyde (4'-hydroxybenzoyl) hydrazone, thiosemicarbazone ligands and its corresponding Cu(2+) complexes were synthesized, and the two complexes' structures were determined by X-ray single crystal diffraction. The interaction of the two Cu(2+) complexes with calf thymus DNA (CT-DNA) was investigated by electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurement. The experimental evidences indicated that the two water-soluble Cu(2+) complexes could strongly bind to CT-DNA via an intercalation mechanism. The intrinsic binding constants of complexes 1 and 2 with CT-DNA were 7.31 x 10(6) and 2.33 x 10(6)M(-1), respectively. Furthermore, the antioxidant activities (hydroxyl radical and superoxide) of the two water-soluble metal complexes were determined by hydroxyl radical and superoxide scavenging method in vitro.

Synthesis, characterization, DNA-binding properties of the Ln(III) complexes with 6-hydroxy chromone-3-carbaldehyde-(4'-hydroxy) benzoyl hydrazone.

6-Hydroxy chromone-3-carbaldehyde-(4'-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb] have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, (1)H NMR, thermogravimetry/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula of the complex is [Ln L.(NO(3))(2)].NO(3). Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA was 2.48 x 10(5) M(-1) through fluorescence titration data.

DNA-binding properties studies and spectra of a novel Cu(II) complex with a new coumarin derivative.

A new coumarin derivative (8-methylcoumaro-4a,10a-pyrone-3-carbaldehyde benzoyl hydrazone) ligand and its novel Cu(II) complex have been synthesized and characterized on the basis of elemental analyses, molar conductivities, (1)H-NMR, IR spectra, UV-visible spectroscopy and thermal analyses. In addition, the interactions of the Cu(II) complex and the ligand with calf-thymus DNA were investigated by spectrometric titrations, ethidium bromide displacement experiments and viscosity measurements. It was found that both the two compounds, specially the Cu(II) complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism.

Synthesis, characterization and antioxidant activity of naringenin Schiff base and its Cu(II), Ni(II), Zn(II) complexes.

A new ligand, naringenin-2-hydroxy benzoyl hydrazone (H(5)L), was prepared by condensation of naringenin with 2-hydroxy benzoyl hydrazine. Its Cu(II), Ni(II), Zn(II) complexes have also been synthesized and characterized on the basis of (1)H-NMR, IR, UV-Vis spectra, elemental analyses, molar conductivity and thermal analyses. The general formula of these complexes was M(H(3)L) [M=Cu(II), Ni(II) and Zn(II)]. In addition, the antioxidant activities (superoxide and hydroxyl radical) of the free ligand and its complexes were determined in vitro. These compounds were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. In particular, the Cu(II) complex displayed excellent activity on the superoxide radical.