One-step synthesis of a carbon dot-based fluorescent probe for colorimetric and ratiometric sensing of tetracycline.

Carbon dots (CDs) with blue fluorescence were synthesized using indole-3-butyric acid and l-tryptophan using a one-step hydrothermal method. The CDs were further employed as a fluorescent sensor with high selectivity for colorimetric and ratiometric detection of tetracycline (TC) in water. The limit of detection (LOD) was found to be 0.33 µM for TC with R2 = 0.98387. Besides, the CDs could be applied in practical water samples and showed good recovery.

A novel fluorescent probe based on rhodamine hydrazone derivatives bearing a thiophene group for Al³âº.

In the present work, a novel 5-methyl-thiophene-carbaldehyde-functionalized rhodamine 6G Schiff base (RA) was designed and easily prepared as an Al(3+) fluorescent and colorimetric probe, which could selectively and sensitively detect Al(3+) by showing enhanced fluorescence emission. Meanwhile distinct color variation from colorless to pink also provided 'naked eye' detection of Al(3+), due to the ring spirolactam opening of the rhodamine derivative. Other metal ions (including K(+), Mg(2+), Na(+), Ba(2+), Mn(2+), Cd(2+), Fe(2+), Ni(2+), Pb(2+), Zn(2+), Hg(2+), Co(2+), Li(+), Sr(2+) and Cu(2+)) could only induce limited interference. The detection limit of the fluorescent probe was estimated to be 4.17 × 10(-6) M, the binding constant of the RA-Al(3+) complex was 1.4 × 10(6) M(-1). Moreover, this fluorescent probe RA possessed high reversibility. As aluminum is a ubiquitous metal in nature and plays vital roles in many biological processes, this chemosensor could be explored for biological study applications.

An amino-imino resonance study of 2-amino-4-methylpyridinium nitrate and 2-amino-5-methylpyridinium nitrate.

The contributions of the amino and imino resonance forms to the ground-state structures of 2-amino-4-methylpyridinium nitrate, C(6)H(9)N(2)(+)·NO(3)(-), and the previously reported 2-amino-5-methylpyridinium nitrate [Yan, Fan, Bi, Zuo & Zhang (2012). Acta Cryst. E68, o2084], were studied using a combination of IR spectroscopy, X-ray crystallography and density functional theory (DFT). The results show that the structures of 2-amino-4-methylpyridine and 2-amino-5-methylpyridine obtained upon protonation are best described as existing largely in the imino resonance forms.

(E)-3-(2-Hy-droxy-5-methyl-phenyl-imino)-indolin-2-one.

In the title compound, C(15)H(12)N(2)O(2), the dihedral angle between the two benzene rings is 83.55 (11)° In the crystal, the molecules are linked by O-H⋯O and N-H⋯O hydrogen bonds.

[Synthesis and characterization of CTMAB and PDMDAAC modified organobentonite].

The natural bentonite was purified and changed to sodium form by NaCl via exchange reaction. Their characteristics, such as swelling volume, swelling value, colloid valence, ethylene blue adsorbed and cation exchange capacity, were measured. The results indicate that the property of Na-bentonite is better than that of natural bentonite. Using cetyltrimethylammonium bromide (CTMAB) and homopolymer of dimethyldiallyammomium chloride (PDMDAAC) as organo-intercalating reagents, two organic modified bentonites were prepared and characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD) and BET surface area. The XRD results showed that the CTMAB-bentonite and PDMDAAC-bentonite had typical X-ray diffraction peaks, and the d001 values increased to 1.89 and 1.45 nm, respectively. Combined with the results of FTIR, the modified reagents had been intercalated to the layer of bentonite. The BET areas, pore volumes and average pore diameters of the two organo-bentonites were decreased as compared to that of Na-bentonite.

4-[(E)-(2-Methoxy-phen-yl)imino-meth-yl]-N,N-dimethyl-aniline.

In the title compound, C(16)H(18)N(2)O, the dihedral angle between the benzene rings is 38.5 (2)°. The crystal packing is stabilized by weak C-H⋯N and C-H⋯O inter-actions and aromatic π-π stacking [centroid-centroid separations = 3.620 (5) and 3.546 (4) Å].

1-[(Z)-(5-Methyl-2-pyrid-yl)iminiometh-yl]-2-naphtholate.

In the zwitterionic title compound, C(17)H(14)N(2)O, the dihedral angle between the naphthalene and pyridine ring systems is 3.56 (9)° and an intra-molecular N-H⋯O hydrogen bond generates an S(6) ring. In the crystal, mol-ecules are linked by C-H⋯O inter-actions.

1,5-Dimethyl-2-phenyl-4-{[(E)-3,4,5-trimethoxybenzylidene]amino}-1H-pyrazol-3(2H)-one.

In the title compound, C(21)H(23)N(3)O(4), the pyrazole ring forms dihedral angles of 21.58 (8) and 66.64 (7)° with the benzene and phenyl rings, respectively. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

2-Meth-oxy-6-[(Z)-[(5-methyl-2-pyrid-yl)imino-meth-yl]phenol.

The title compound, C(14)H(14)N(2)O(2), was obtained by a condensation reaction between o-vanillin and 5-methyl-pyridin-2-amine. In the mol-ecule, the dihedral angle between the pyridine and benzene rings is 9.08 (13)°. An intra-molecular hydrogen bond involving the imine N atom and the hydroxyl group may influence the conformation of the mol-ecule. The crystal structure is stabilized by weak C-H⋯O hydrogen bonds.

Dichlorido{N-[1-(2-pyrid-yl)ethyl-idene]ethane-1,2-diamine}copper(II).

The title complex, [CuCl(2)(C(9)H(13)N(3))], is mononuclear and contains a five-coordinate Cu(II) atom. The geometry of the Cu(II) atom can be described as tetra-gonal-pyramidal derived from the calculation of the value τ = 0.102. The three N atoms of the pyridine and ethane-1,2-diamine ligands and one Cl atom belong to the basal plane and the other Cl atom represents the axial position of the pyramid. The Cu atom is displaced by 0.2599 (2) Šfrom the basal plane towards the axial Cl atom. In the crystal, mol-ecules are linked into chains by inter-molecular N-H⋯Cl and C-H⋯Cl hydrogen bonds.

2-[(1,3-Benzothia-zol-2-yl)imino-meth-yl]phenol.

The title compound, C(14)H(10)N(2)OS, is nearly planar, with a maximum deviation of 0.0698 (13) Šfrom the mean plane, and exists in an E configuration with respect to the C=N bond. The dihedral angle between the two benzene rings is 2.81 (9)°. There is an intra-molecular O-H⋯N hydrogen bond and inter-molecular C-H⋯O and C-H⋯N hydrogen bonds.

Tetra-µ-acetato-κO:O'-bis-{[2-(2-fur-yl)-1-(2-furylmeth-yl)-1H-benzimidazole-κN]copper(II)}.

The title complex, [Cu(2)(CH(3)COO)(4)(C(16)H(12)N(2)O(2))(2)], forms a dimer of the paddle-wheel type located on a crystallographic inversion centre. The two Cu(II) atoms [Cu⋯Cu = 2.7254 (11) Å] are bridged by four acetate anions. The geometry of the polyhedron around the metal centre can be described as tetra-gonal-pyramidal derived from the calculation of the value τ = 0.0018. The apical positions of the tetra-gonal-pyramidal copper coordination polyhedra are occupied by the N atoms of 2-(2-fur-yl)-1-(2-furylmeth-yl)-1H-benzimidazole ligands. In the crystal structure, mol-ecules are linked into a chain by inter-molecular C-H⋯O hydrogen bonds parallel to [010]. Two furan rings are disordered over two positions in ratios of 0.55:0.45 and 0.69:0.31.

Poly[tris-(µ(3)-5-amino-isophthalato)diaqua-dicerium(III)].

In the title complex, [Ce(2)(C(8)H(5)NO(4))(3)(H(2)O)(2)](n), each Ce ion is in nine-coordinated environment. Eight O atoms from six ligands participate in coordination, in addition to one O atom from a water mol-ecule. Both carboxyl-ate groups from the ligands chelate the Ce atoms, forming two four-membered rings. The 5-amino-isophthalate ligands also bridge the Ce centers, forming a two-dimensional network, and O-H⋯O and N-H⋯O hydrogen bonds complete the structure.

1,1',5,5'-Tetra-methyl-2,2'-diphenyl-4,4'-[p-phenyl-enebis(methyl-idynenitrilo)]di-1H-pyrazol-3(2H)-one.

In the centrosymmetric title compound, C(30)H(28)N(6)O(2), the dihedral angles between the anti-pyrine ring and the terminal phenyl and central benzene rings are 50.55 (10) and 14.62 (9)°, respectively. Some short inter-molecular C-H⋯O inter-actions may help to establish the packing. An intramolecular C-H⋯O hydrogen bond is also present.

[Synthesis, characterization and fluorescence property of an unsymmetrical Schiff base and its copper complex].

An unsymmetrical tetradentate Schiff base ligand (H2L) was synthesized using 5-chloro-2-hydroxybenzophenone, o-phenylenediamine and salicylaldehyde. A solid complex of this ligand CuL was prepared and characterized by elemental analyses, IR spectra, UV spectra, TG-DTG and molar conductance. Possible structure of this complex was proposed. The fluorescence property of the ligand and complex was also studied. The result indicates that the Schiff base reagent exhibits a maximum of fluorescence emission spectrum at 385 nm. At pH 9.62, the copper complex of this reagent can cause fluorescence quenching of the reagent.

[Synthesis and characterization of La(III) binuclear complex with 2-hydroxy-l-naphthaldehyde-beta-alanine and its interaction with DNA].

The binuclear complex of Schiff base C14H12NO3K(KHL) derived from 2-hydroxy-l-naphthaldehyde and beta-alanine with lanthanide nitrate was synthesized and characterized by elemental analysis, IR, UV, TG-DTA, and molar conductance analysis. The composition of the complex was [La2(L)2 (NO3)2] x 2C2H5OH. The interaction of the complex and DNA was studied by fluorescence spectrum. The result indicates that the La(III) complex could cause a sharp decrease in the fluorescence intensity of EB-DNA system, and the complex could partly sustain the place of EB.