Sensitive and selective detection of Cu(II) ion: A new effective 1,8-naphthalimide-based fluorescence 'turn off' sensor.

The present study reports the development of a new 1,8-naphthalimide-based fluorescent sensor V for monitoring Cu(II) ions. The sensor exhibited pH independence over a wide pH range 2.52-9.58, and indicated its possible use for monitoring Cu(II) ions in a competitive pH medium. The sensor also showed high selectivity and sensitivity towards the Cu(II) ions over other competitive metal ions in DMSO-HEPES buffer (v/v, 1:1; pH 7.4) with a fluorescence 'turn off' mode of 79.79% observed. A Job plot indicated the formation of a 1:1 binding mode of the sensor with Cu(II) ions. The association constant and detection limit were 1.14 × 106  M-1 and 4.67 × 10-8 M, respectively. The fluorescence spectrum of the sensor was quenched due to the powerful paramagnetic nature of the Cu(II) ions. Potential application of this sensor was also demonstrated when determining Cu(II) ion levels in two different water samples.

Characterization of a highly Al3+ -selective fluorescence probe based on naphthalimide-Schiff base and its application to practical water samples.

A new fluorescent Al3+ -probe, N-allyl-4-[3,3'-((2-aminoethyl)azanediyl)-bis(N´-(2-hydroxybenzylidene)propanehy-drazide)]-1,8-naphthalimide (L), was designed and synthesized based on 1,8-naphthalimide. The probe L contains 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X-ray. L emission at 526 nm increased on addition of Al3+ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al3+ in ethanol/Tris-HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R2 ) of 0.99 was observed in the concentration range 2-10 µM. The binding constant and the detection limit of L for Al3+ were calculated to 2.6 × 104  M-1 and 0.34 µM, respectively. The results of experiments that including Job plot, ultraviolet-visible (UV-Vis) light titration, fluorescence titration, ESI-MS and 1 H NMR titration, indicated a 1:1 stoichiometric complex between L and Al3+ . L was highly effective in monitoring Al3+ in real-life Yellow River and tap water samples.

A highly Selective Fluorescent Sensor for Monitoring Cu2+ Ion: Synthesis, Characterization and Photophysical Properties.

A new fluorescent sensor, 4-allylamine-N-(N-salicylidene)-1,8-naphthalimide (1), anchoring a naphthalimide moiety as fluorophore and a Schiff base group as receptor, was synthesized and characterized. The photophysical properties of sensor 1 were conducted in organic solvents of different polarities. Our study revealed that, depending on the solvent polarity, the fluorescence quantum yields varied from 0.59 to 0.89. The fluorescent activity of the sensor was monitored and the sensor was consequently applied for the detection of Cu2+ with high selectivity over various metal ions by fluorescence quenching in Tris-HCl (pH = 7.2) buffer/DMF (1:1, v/v) solution. From the binding stoichiometry, it was indicated that a 1:1 complex was formed between Cu2+ and the sensor 1. The fluorescence intensity was linear with Cu2+ in the concentration range 0.5-5 µM. Moreso, the detection limit was calculated to be 0.32 µM, which is sufficiently low for good sensitivity of Cu2+ ion. The binding mode was due to the intramolecular charge transfer (ICT) and the coordination of Cu2+ with C = N and hydroxyl oxygen groups of the sensor 1. The sensor proved effective for Cu2+ monitoring in real water samples with recovery rates of 95-112.6 % obtained.

A Highly Selective and Sensitive Fluorescent Turn-on Probe for Al3+ Based on Naphthalimide Schiff Base.

A simple and highly selective aluminium ion fluorescent probe (N-n-butyl-4-[3,3'-((2-aminoethyl)azanediyl)bis(N'-(2-hydroxy-3-methoxybenzylidene)-propanehydrazide)]-1,8-naphthalimide) (P-1) employing 1,8-naphthalimide as the fluorophore group and Schiff base as the recognition group has been successfully synthesized and systemically characterized. The structure of probe P-1 has been established by single crystal X-ray. The photophysical properties of probe P-1 revealed that the values of the fluorescence quantum yield are higher in non-polar solvents than in polar solvents. Compared with the free P-1, the fluorescence intensity of P-1 shows a significant fluorescence enhancement in the presence of Al3+ without any significant interference from other cations and anions. In addition, from the UV-vis titration, fluorescence titration,Job's plot and 1H NMR spectra analysis, we could primarily confirm that three important coordinative sites of P-1 for Al3+ were from imine nitrogen and tertiary amine nitrogen and formed a 1:1 complex. The fluorescence intensity for the (P-1) showed a good linearity with the concentration of Al3+ in the range of 3.0-10.0 µM, with a detection limit of 8.65 × 10-8 M and a binding constant (Kb) of 4.95 × 104 M-1. It is worthy of note that the probe P-1 was successfully applied in detection of Al3+ in Yellow River and tap water samples.

[1,1'-Dibenzyl-2,2'-(2-oxapropane-1,3-diyl)di(1H-benzimidazole)-κ³N³,O,N³']bis(2,4,6-trinitrophenolato-κO¹)manganese(II).

In the title complex, [Mn(C6H2N3O7)2(C30H26N4O)], the Mn(II) atom is coordinated by the tridentate bis-benzimidazole ligand and two atoms of the picrate anions, in a distorted square-pyramidal geometry (τ = 0.038). One nitro O atom of one picrate ion is disordered over two sites with occupancies of 0.54 (5) and 0.46 (5).

Bis[2,6-bis-(1-methyl-1H-benzimidazol-2-yl-κN(3))pyridine-κN]zinc dipicrate methanol disolvate.

In the title compound, [Zn(C(21)H(17)N(5))(2)](C(6)H(2)N(3)O(7))(2)·2CH(3)OH, the Zn(II) atom is coordinated by six N atoms from two tridentate 2,6-bis-(1-methyl-1H-benzimidazol-2-yl)pyridine ligands in a distorted octa-hedral environment. In the crystal, the picrate anions and methanol solvent mol-ecules are connected by O-H⋯O hydrogen bonds. Weak inter-molecular C-H⋯O hydrogen bonds are also observed.

Tris(1H-benzimidazol-3-ium-2-ylmeth-yl)amine tris-(2,4,6-trinitro-phenolate) acetonitrile disolvate.

In the cation of the title salt, C(24)H(24)N(7) (3+)·3C(6)H(2)N(3)O(7) (-)·2C(2)H(3)N, the three benzimidazolium ring systems are oriented to each other at dihedral angles of 10.42 (7), 23.98 (7) and 22.17 (7)°. In the crystal, the cation links to the adjacent picrate anions via N-H⋯O hydrogen bonds; one of independent acetonitrile solvent mol-ecules is also linked to the cation via an N-H⋯N hydrogen bond.

Synthesis, Crystal Structure, and DNA-Binding Studies of a Nickel(II) Complex with the Bis(2-benzimidazolymethyl)amine Ligand.

A V-shaped ligand Bis(2-benzimidazolymethyl)amine (bba) and its nickel(II) picrate (pic) complex, with composition [Ni(bba)(2)](pic)(2)·3MeOH, have been synthesized and characterized on the basis of elemental analyses, molar conductivities, IR spectra, and UV/vis measurements. In the complex, the Ni(II) ion is six-coordinated with a N(2)O(4) ligand set, resulting in a distorted octahedron coordination geometry. In addition, the DNA-binding properties of the Ni(II) complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The experimental results suggest that the nickel(II) complex binds to DNA by partial intercalation binding mode.

1-Methyl-2-({[(1-methyl-1H-benzimid-azol-2-yl)meth-yl](phen-yl)amino}-meth-yl)1H-benzimidazol-3-ium picrate.

In the title molecular salt, C(24)H(24)N(5) (+)·C(6)H(2)N(3)O(7) (-), the dihedral angle between the benzimidazole rings of the cation is 5.041 (2)°. In the anion, the three nitro groups make dihedral angles of 2.468 (3), 12.795 (3) and 24.958 (4)° with respect to the central ring. In the crystal, weak aromatic π-π stacking [centroid-centroid distance = 3.599 (15) Å] consolidates the packing. In addition, an intra-molecular N-H⋯N hydrogen bond is observed.

Bis[1,3-bis(1-propyl-1H-benzimidazol-2-yl)-2-oxapropane]-cadmium(II) dipicrate dimethyl-formamide monosolvate.

In the title compound, [Cd(C(22)H(26)N(4)O)(2)](C(6)H(2)N(3)O(7))(2)·C(3)H(7)NO, the Cd(II) ion is coordinated by four N atoms and two O atoms from two tridentate 1,3-bis-(1-propyl-1H-benzimidazol-2-yl)-2-oxopropane ligands in a distorted octa-hedral coordination environment. There are significant differences in the chemically equivalent Cd-O bond lengths [2.618 (2) Šand 2.561 (2) Å].

Bis[1,3-bis-(1-methyl-1H-benzimidazol-2-yl)-2-oxapropane]-cadmium dipicrate acetonitrile sesquisolvate 0.25-hydrate.

In the title compound, [Cd(C(18)H(18)N(4)O)(2)](C(6)H(2)N(3)O(7))(2)·1.5CH(3)CN·0.25H(2)O, the Cd(II) ion is coordinated by four N atoms and two O atoms from two tridentate 1,3-bis-(1-methyl-1H-benzimidazol-2-yl)-2-oxopropane ligands in a distorted octa-hedral coordination environment. The lengths of the chemically equivalent Cd-O bonds [2.4850 (16) and 2.5488 (16)Å] are signiificantly different. One of the picrate anions is disordered over two sets of sites, with refined occupancies of 0.504 (15) and 0.496 (15). A 0.5-occupancy acetonitrile solvent mol-ecule is disordered over two sites with equal occupancies. The H atoms of a 0.25-occupancy solvent water mol-ecule were neither located nor included in the refinement.

Bis[1,3-bis-(1-ethyl-1H-benzimidazol-2-yl)-2-oxapropane]-cadmium(II) dipicrate dimethyl-formamide disolvate.

In the title compound, [Cd(C(20)H(22)N(4)O)(2)](C(6)H(2)N(3)O(7))(2)·2C(3)H(7)NO, the Cd(II) ion is coordinated by four N atoms and two O atoms from two tridentate 1,3-bis-(1-ethyl-1H-benzimid-azol-2-yl)-2-oxapropane ligands in a distorted octa-hedral environment.

1,3-Bis(1-methyl-1H-benzimidazol-2-yl)-2-oxapropane.

In the title mol-ecule, C(18)H(18)N(4)O, the dihedral angle between the mean planes of the two benzimidazole ring systems is 61.5 (1)°.

Bis(nitrato-κO)(3-oxapentane-1,5-diamine-κN,O,N')zinc(II).

In the title compound, [Zn(NO(3))(2)(C(4)H(12)N(2)O)], the Zn(II) atom is N,O,N'-chelated by a 3-oxapentane-1,5-diamine ligand and is further coordinated by two nitrate anions in a distorted trigonal-bipyramidal geometry. Inter-molecular N-H⋯O hydrogen bonding is present in the crystal structure. A short O⋯O contact of 2.816 (8) Šis observed between the nitrate anions of adjacent mol-ecules.

Bis[N,N-bis-(1-allyl-1H-benzimidazol-2-ylmethyl-κN)benzyl-amine-κN]cadmium dipicrate.

The crystal structure of the title compound, [Cd(C(29)H(29)N(5))(2)](C(6)H(2)N(3)O(7))(2), consists of Cd(II) complex cations and picrate anions. In the complex cation, the Cd(II) ion is chelated by two bis-(1-allyl-benzimidazol-2-ylmeth-yl)benzyl-amine (babb) ligands in a distorted octa-hedral geometry. Extensive C-H⋯O hydrogen bonding occurs between cations and anions in the crystal structure.

Synthesis, Crystal Structure, and Spectra Properties of the Cadmium (II) Complex with Bis(N-allylbenzimidazol-2-ylmethyl)benzylamine.

A novel complex of cadmium (II) picrate (pic) with V-shaped ligand bis(N-allylbenzimidazol-2-ylmethyl)benzylamine (babb), with composition [Cd(babb)(2)](pic)(2), was synthesized and characterized by elemental analyses and electrical conductivity, IR, and UV/visible spectra. The crystal structure of the complex has been determined by the single-crystal X-ray diffraction. In the complex, the coordination sphere around Cd (II) is distorted octahedral, six nitrogen atoms involved in coordination afforded by two tridentate ligand babb. Moreover, The DNA-binding properties of the ligand babb and Cd (II) complex were investigated by spectrophotometric methods and viscosity measurements, and the results suggest that they bind to DNA via an intercalation binding mode, and the Cd (II) complex shows higher affinity than the ligand.

Synthesis and characterization of the ligand based on benzimidazole and its copper complex: DNA binding and antioxidant activity.

A new copper(II) complex with formulae of [Cu(buobb)(2)](pic)(2), where buobb stands for the ligand of 1,3-bis(1- butylbenzimidazol-2-yl)-2-oxopropane and pic represents 2,4,6-trinitrophenol, has been synthesized and characterized by elemental analyses, molar conductivity, IR, UV-Vis spectra measurements, and cyclic voltammetry. The crystal structure of the copper(II) complex has been determined by X-ray single-crystal diffraction. The coordination environment around each copper(II) atom can be described as a distorted octahedral geometry. The π-π stacking interactions link the copper(II) complex into a 1D infinite network. The interactions of the ligand and the copper(II) complex with calf thymus DNA (CT-DNA) are investigated by using electronic absorption titration, ethidium bromide-DNA displacement experiments, and viscosity measurements. Additionally, the copper(II) complex's antioxidant properties have been investigated in vitro.

(Dimethyl-formamide-κO)(2-hy-droxy-benzoato-κO,O)[tris-(1-methyl-1H-benzimidazol-2-ylmethyl-κN)amine-κN]manganese(II) perchlorate dimethyl-formamide monosolvate.

In the title complex, [Mn(C(7)H(5)O(3))(C(27)H(27)N(7))(C(3)H(7)NO)]ClO(4)·C(3)H(7)NO, the Mn(II) ion is coordinated in a slightly distorted monocapped trigonal-prismatic geometry. The tris-(1-methyl-1H-benzimidazol-2-ylmeth-yl)amine (Mentb) ligand coordinates in a tetra-dentate mode and the coordination is completed by a bis-chelating salicylate ligand and a dimethyl-formamide ligand. The hy-droxy group and the ortho H atoms of the salicylate ligand were refined as disordered over two sites with occupancies of 0.581 (8) and 0.419 (8). Both disorder components of the hy-droxy group form intra-molecular O-H⋯O hydrogen bonds.

(Dimethyl-formamide)(2-methyl-propen-oato)[tris-(1-methyl-1H-benzimidazol-2-ylmeth-yl)amine]-manganese(II) perchlorate dimethyl-formamide solvate.

In the title complex, [Mn(C(4)H(5)O(2))(C(27)H(27)N(7))(C(3)H(7)NO)]ClO(4)·C(3)H(7)NO, the Mn(II) ion is seven-coordinated in a distorted monocapped trigonal-prismatic geometry formed by a tetra-dentate tris-(1-methyl-1H-benzimidazol-2-ylmeth-yl)amine mol-ecule, a bidentate 2-methacrylate anion and a dimethyl-formamide mol-ecule. The methyl groups of the coordinated dimethyl-formamide mol-ecule and the perchlorate anions are disordered over two positions with occupancy factors of 0.640 (8) and 0.360 (8).

Aqua(dimethylformamide){tris[(1-methyl-1H-benzimidazol-2-yl)methyl]amine}nickel(II) dipicrate.

In the title complex, [Ni(C(27)H(27)N(7))(C(3)H(7)NO)(H(2)O)](C(6)H(2)N(3)O(7))(2), the Ni(II) ion is coordinated in a slightly distorted octa-hedral coordination evironment by an NiN(4)O(2) ligand set. The tris-(N-methyl-benzimidazol-2-ylmeth-yl)amine ligand is in a tetra-dentate mode while a coordinated water molecule and a dimethyl-formamide ligand complete the coordination. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link the cation and one of the pictrate anions into four-component centrosymmetric clusters.