Sheng-ying Qin

Synthesis of Salicylaldimine Schiff Bases with Benzo‐10‐aza‐15‐crown‐5 Pendant

Abstract A series of azacrown ether substituted salicylaldimine Schiff bases 3a–c, 5a–c, and 6a–c have been synthesized by the condensation of salicylaldehyde with azacrown ether‐containing arylamine or amino‐compounds with azacrown ether‐containing salicylaldehyde from benzo‐10‐aza‐15‐crown‐5. The new structure was elucidated by spectral methods and confirmed by x‐ray crystallographic analysis.

Synthesis and Study of Unsymmetrical Schiff Base Mn(III) Complexes with Pendant Aza-crown or Morpholino Groups as Catalyst in Aerobic Oxidation for p-Xylene to p-Toluic Acid

A series of novel unsymmetrical Schiff base Mn(III) complexes with pendant aza-crown or morpholino groups have been synthesized and studied as catalysts in aerobic oxidation of `p-xylene to p-toluic acid (PTA). The oxidation of p-xylene to p-toluic acid with air at 120°C under normal atmospheric pressure occurred efficiently in the presence of aza-crown ether substituted unsymmetrical Schiff base Mn(III) complexes. Significant selectivity (up to ∼90%) and conversion levels (up to ∼40%) were obtained. The effect of the aza-crown ring appended in Mn(III) Schiff base complexes on the oxidation of p-xylene were also investigated by comparison with the morpholino group pendant analogues. The addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.

An Efficient Aerobic Oxidation for p-Xylene to p-Toluic Acid using Azacrown Ether-tethered Mn(III) Schiff Base Complexes as Catalysts

The oxidation of p-xylene to p-toluic acid with air at 110°C under normal atmospheric pressure occurs efficiently in the presence of crown Mn(III) Schiff base complexes [Formula: See Text] (n=1-4). Significant conversion levels (up to 75%) and selectivity (up to 92-96%) are obtained; the effect of the azacrown ether pendants in Mn(III) Schiff base complexes on the oxidation of p-xylene are also investigated by comparison with the crown-free analogues [Formula: See Text] Moreover, addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.

Synthesis of novel salicylaldimine Schiff bases with a pendant benzo-10-aza-15-crown

Novel salicylaldimine mono-Schiff bases with aza-crown pendant have been synthesised via condensation of 3-[(benzo-10-aza-15-crown-5)methyl] salicylaldehyde with substituted aniline and characterised by 1H NMR, IR, mass spectroscopy and elemental analysis. The crystal structure of N-(4-hydroxy-3- formylbenzyl)benzo-10-aza-15-crown-5 aldimine with 4-aminophenol (HL10) has been determined from X-ray diffraction data.

Dioxygen affinities and catalytic oxidation performance of cobalt (ii) hydroxamates

The dioxygen affinities and catalytic oxidation performance of cobalt (II) complexes with N-phenylhydroxamic acids were investigated. The effects of substituting groups in aromatic ring of ligands on these properties were examined, and some relativity between the dioxygen affinities and catalytic oxidation activity were also discussed in this paper.

Synthesis and Kinetic Studies of Mono-Schiff Base Manganese(III) and Cobalt(II) Complexes with Aza-Crown Ether or Morpholino Pendants as Synthetic Hydrolases for p -Nitrophenyl Picolinate

Two mono-Schiff base manganese(III) and cobalt(II) complexes with benzo-10-aza-crown ether pendants (MnL12Cl, CoL12), and the analogues with morpholino pendants (MnL22Cl, CoL22) have been synthesised and employed as models for hydrolase enzymes to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in buffer solution. A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of the structures of the complexes and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit high catalytic activity and the rate increases with pH. In comparison with the crown-free analogues MnL22Cl and CoL22, the crowned Schiff base complexes MnL12Cl and CoL12 exhibit higher catalytic activity for promoting PNPP hydrolysis.

Hydrolysis Kinetics of p-Nitrophenyl Picolinate Catalyzed by Mono-Schiff Base Complexes with Aza-Crown Ether or Morpholino Pendants in CTAB Surfactant Micellar Solution

Two mono-Schiff base manganese (III) and cobalt (II) complexes with benzo-10-aza-crown ether pendants ( ), and the analogy with morpholino pendants ( ) have been synthesized and employed as models for hydrolase enzymes to promote the hydrolysis of p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. The kinetic mathematical model and mechanism cleavage on PNPP hydrolysis catalyzed by these complexes was proposed. The effects of complexes structure and reactive temperature on the rate of catalytic PNPP hydrolysis have been also examined. The results showed that the reactive rate increases with pH of the buffered CTAB micellar solution; all four complexes exhibited high activity for the catalytic PNPP hydrolysis in the buffered CTAB micellar solution. In comparison with the crown-free analogy and , the crowned Schiff base complexes and exhibit higher catalytic activity for promoting PNPP hydrolysis.

Studies on p-Nitrophenyl Picolinate (PNPP) Cleavage by Mono-Schiff Base Complexes with Aza-Crown Ether or Morpholino Pendants in CTAB Micellar Solution

Two mono-Schiff base manganese (III) and cobalt (II) complexes with benzo-10-aza-crown ether pendants , and the analogous with morpholino pendants have been employed as models to mimic hydrolase in p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. The kinetics and the mechanism on PNPP hydrolysis catalyzed by these complexes were investigated. The kinetic mathematical model of PNPP cleavage catalyzed by these complexes was proposed. The relative kinetic and thermodynamic parameters were determined. The effects of complexes structure and reactive temperature on the rate of catalytic PNPP hydrolysis have been also examined. The results showed that the rate for the catalytic PNPP hydrolysis was increased following the increase of pH of the buffered CTAB micellar solution; four complexes can efficiently accelerate the catalytic cleavage of PNPP in the buffered CTAB micellar solution. Compared with the crown-free analogous and , the crowned Schiff base complexes exhibit more high catalytic activity for promoting PNPP hydrolysis. The pseudo-first-order-rate ( k obs ) for the PNPP hydrolysis catalyzed by the complex in the CTAB micellar solution is 2.02 × 104 times than that of PNPP spontaneous hydrolysis in water at pH = 7.00, 25°C, [S] = 2.0 × 10−4 mol dm−3.

Synthesis and studies of hydrolysis of p-nitrophenyl picolinate catalysed by Schiff base zinc (II) complexes with aza-crown ether or morpholino-pendants

Four Schiff base zinc (II) complexes with either benzo-10-aza-crown ether pendants or morpholino-pendants have been synthesised and employed as models for hydrolase enzymes by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP). A kinetic model of PNPP cleavage catalysed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of catalytic PNPP hydrolysis have been also examined. The rate increases with pH of the buffer solution; all four complexes exhibited high activity in the catalytic PNPP hydrolysis. Compared with their crown-free analogues, the crowned Schiff base complexes exhibit higher catalytic activity. The catalytic activity of a phenyl-bridged Schiff base complex is larger than that of an ethyl-bridged Schiff base complex under the same substitute groups and metal ion.

Catalytic hydrolysis of PNPP by cobalt (II) and manganese (III) complexes with (15-Crown-5) salicylidenephenylimine

Cobalt (II) and manganese (III) complexes with crowned salicylaldimine mono-Schiff base ligand have been employed as models to mimic hydrolase in catalytic hydrolysis of p-nitrophenyl picolinate(PNPP). The kinetics and the mechanism of PNPP hydrolysis have been investigated. The kinetic mathematical model of PNPP cleavage catalysed by these complexes has been proposed.