ABSTRACT
MXenes and MXene-based composite materials have potential applications in a wide range of areas due to their unique physical and chemical characteristics. At present, it is still a major challenge to develop a simple, safe, and efficient route to prepare MXenes without using fluorinated etchants. Herein, we design a facile method to prepare Ti3C2Tx MXene sheets by selectively etching Ti3AlC2 powders in an aqueous diluted H2SO4 solution with H2O2 as an oxidant. In a system of H2SO4 and H2O2, an aqueous H2SO4 solution with a concentration of 6 mol/L is a strongly acidic medium with no volatility, and 30% H2O2 acts as a strong green oxidizer without harmful by-products. The experimental process is safe and convenient to conduct in a beaker under a water bath of 40°C. The etching process can be completed in 1 h under the air atmosphere conditions. The experimental results confirmed that the etched Ti3AlC2 powders can be successfully separated into Ti3C2Tx nanosheets under ultrasound treatment without using any intercalation agent. The relevant etching mechanism is may be attributed to the synergy effect of H2SO4 and H2O2, which triggers sequential selective etching of Al layers from the Ti3AlC2 phase. It may provide a new green way to prepare MXene-based materials without using toxic HF or HF-containing etchants.
ABSTRACT
The asymmetric unit of the title compound, {[Cu(C(13)H(15)NO(3))(C(5)H(8)N(2))]·CH(3)OH}(n), contains two complex mol-ecules and two solvent mol-ecules. Each Cu(II) ion is in a distorted square-pyramidal coordination with one N and two O atoms from the Schiff base ligand and one N atom from the heterocycle in the basal positions and one carboxyl-ate O atom from a neighbouring ligand in the apical position. The apical Cu-O bonds are much longer than the basal Cu-O and Cu-N bonds. The carboxyl-ate groups of the Schiff base ligands bridge the Cu(II) ions, forming helical chains along [100]. The crystal packing is stabilized by inter-molecular O-Hâ¯O and N-Hâ¯O hydrogen bonds.
ABSTRACT
In either of the two independent mol-ecules within the asymmetric unit of the title compound, [Ni(C(16)H(15)NO(3))(C(3)H(4)N(2))], the Ni(II) atom is coordinated by the two N atoms and two O atoms in a distorted square-planar geometry. The crystal packing is stabilized by strong and weak inter-molecular C-Hâ¯O hydrogen bonds, as well as weak centroid-centroid π-stacking inter-actions [centroid-centroid separation = 3.526â (3)â Å].
ABSTRACT
In the title complex, [Cu(NCS)(2)(C(12)H(19)N(3))], the Cu(II) atom is five-coordinated in a square-pyramidal geometry defined by one pyridine N, one imine N, and one amine N atom of the tridentate Schiff base ligand and two N-bonded thio-cyanate ions (one of the latter occupying the apical site). The three bridging C atoms and the two terminal C atoms of the Schiff base are disordered over two sets of sites, with occupancies of 0.465â (2) and 0.535â (2).
ABSTRACT
The asymmetric unit of the title complex, [Ni(NCS)(2)(C(13)H(20)N(2)O(2))(2)], consists of two half-mol-ecules, both of which are completed by crystallographic inversion symmetry (Ni(2+) site symmetry = in both cases). Both metal ions are six-coordinated in distorted trans-NiO(2)N(4) geometries arising from two N,O-bidentate Schiff base ligands and two N-bonded thio-cyanate ions. The mol-ecular conformations are reinforced by two intra-molecular N-Hâ¯O hydrogen bonds.
ABSTRACT
In the title compound, [Cu(C(13)H(9)NO(3))(C(5)H(5)N)], the Cu(II) atom is coordinated in a distorted square-pyramidal geometry, with two N and two O atoms in the basal positions and one O atom in the apical position. The apical Cu-O bond [2.3520â (16)â Å] is much longer than the basal Cu-O and Cu-N bonds [1.9139â (14)-2.0136â (17)â Å]. The carboxyl-ate group bridges Cu(II) atoms, forming a zigzag chain along the a axis.
ABSTRACT
In the title compound, [Cu(C(8)H(7)O(2))(NO(3))(C(10)H(8)N(2))], the Cu(II) ion is five-coordinate in a distorted square-pyramidal geometry. The basal positions are occupied by two N atoms from a 2,2'-bipyridine ligand and two O atoms from the 2-acetyl-phenolate anion. The axial position is occupied by one O atom of a nitrate anion. In the bipyridine ligand, the two pyridine rings are slightly twisted by an angle of 3.5â (1)°. The crystal structure is stabilized by C-Hâ¯O hydrogen bonds.
ABSTRACT
In the title compound, [Cu(C(11)H(11)NO(4))(H(2)O)]·H(2)O, each Cu(II) ion is four-coordinated by one N and two O atoms from the tridentate Schiff base ligand, and by one O atom from the coordinated water mol-ecule in a distorted square-planar geometry. Inter-molecular O-Hâ¯O hydrogen bonds link complex mol-ecules and solvent water mol-ecules into flattened columns propagated in [100].
ABSTRACT
A new mononuclear dioxomolybdenum(VI) complex, [MoO2L1], and a new linear trinuclear nickel(II) complex, [NiNiL2(?1-?1:?0-OAc)(?2-?1:?1-OAc)2]·H2O, where L1 is the dianionic form of N,N'-bis(5-fluorosalicylidene)-1,3-propanediamine (H2L1), L2 is the dianionic form of N,N'-bis(5-fluoro-2-hydroxybenzylidene)-2-hydroxy-1,3-propanediamine (H2L2), have been synthesized and characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray determination. The Mo atom in the molybdenum complex is coordinated by four donor atoms of the Schiff base ligand, and two oxo groups, forming an octahedral coordination. In the nickel complex, there are three bridges across the Ni-Ni atom pairs, involving two phenolate O atoms of a Schiff base ligand, and an O-C-O moiety of a ?2-?1:?1-OAc group. The central Ni atom is located on an inversion center and has octahedral coordination involving four bridging O atoms from two Schiff base ligands in the equatorial plane and two O atoms from two ?2-?1:?1-OAc ligands in the axial positions. The coordination around the terminal Ni atoms is also octahedral, with two imino N and two phenolate O atoms from a Schiff base ligand defining the equatorial plane, and with two O atoms respectively from a ?1-?1:?0-OAc and a ?2-?1:?1-OAc ligands occupying the axial positions. The molybdenum complex has excellent catalytic property for sulfoxidation reactions.
ABSTRACT
Two oxidovanadium(V) complexes, [VOLLa] (1) and [VOLLb] (2), where L is the dianionic form of the Schiff base ligand 2-(((2-hydroxyethyl)imino)methyl)-6-methylphenol (H2L), La and Lb are the deprotonated forms of 3-hydroxy-2-methyl-4H-pyran-4-one (HLa) and 2-ethyl-3-hydroxy-4H-pyran-4-one (HLb), respectively, have been prepared and characterized by elemental analyses, IR, UV-Vis, 1H NMR and single-crystal X-ray crystallographic determination. The V atoms in the complexes are in octahedral coordination, with the Schiff base ligand mer-coordinated to the metal atoms through the phenolate O, imino N and hydroxyl O atoms, and with the pyrone ligands coordinated to the metal atoms through the two O atoms. The effect of the compounds on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans was studied.
ABSTRACT
Seven kinds of Chinese traditional medicines, including laoniankechuan tablet, fufangbanxia tablet, weitongning tablet, quanshen tablet, shengshijiangtang capsule, xiasangju particle, and American yangshen tablet, were digested with HNO3-HClO4 mixed acid. The fourteen trace elements, including calcium, magnesium, iron, zinc, potassium, sodium, manganese, copper, chromium, cobalt, strontium, nickel, cadmium and lead in the drugs were determined by atomic absorption spectrometry. The effects of the type of mixed acid, the ratio of HNO3 to HClO4 in mixed acid, the volume of digesting solution, and the digesting time were also investigated in detail. The results obtained show that the concentrations of Ca, Mg, Fe, K and Na in seven kinds of Chinese traditional medicines are higher than those of other elements. Moreover, shengshijiangtang capsule for the treatment of diabetes contains plenty of Mn, and weitongning tablet for the treatment of stomach disease contains plenty of Sr, Mn and Cu.