Reactions at the azomethine CN bonds in the nickel(<scp>ii</scp>) and copper(<scp>ii</scp>) complexes of pyridine-containing Schiff-base macrocyclic ligands

Herrera, Aida M.; Kalayda, Ganna V.; Disch, Jeremy S.; Wikstrom, Jeffrey P.; Korendovych, Ivan V.; Staples, Richard J.; Campana, Charles F.; Nazarenko, Alexander Y.; Haas, T. E.; Rybak‐Akimova, Elena V.

doi:10.1039/b308557k

Cited by 40 publications

(32 citation statements)

References 70 publications

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“…The dynamic covalent nature of imine linkages in Schiff bases results in a propensity for them exist in equilibrium in solution with their partially hydrolysed carbinolamine forms together with their corresponding free amine and aldehyde/ketone precursors [29][30][31][32][33][34][35][36].…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)

Fanna

Smith

Zhang

et al. 2015

J Incl Phenom Macrocycl Chem

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The in situ Schiff base condensation of 2-acetylpyrazine with tris(2-aminoethyl)amine in the presence of zinc(II) perchlorate was carried out in absolute ethanol and 95 % ethanol, respectively. Two new tripodal metalloligands, 1 and 2, were isolated. The formation of complexes 1 and 2 has been verified by NMR, mass spectral studies and X-ray (for 2), with the evidence indicating that a zinc ion is incorporated in the tripodal cavity defined by the tren backbone in each case. However the products differed in the number of Schiff base condensation reactions that had occurred. While the use of absolute ethanol resulted in condensation at all three primary amine sites of tris(2-aminoethyl)amine, employing 95 % ethanol yielded condensation at only one of the primary amine sites. These different outcomes can be ascribed, at least in part, to the effect of the different water contents in the respective reaction solvents resulting in a shift of the dynamic equilibrium involving imine formation towards the precursor amine and ketone reagents. In 1, steric considerations dictate that the three uncoordinated pyrazine nitrogen donors will have their coordination vectors oriented in a mutually divergent manner suitable for coordination to three different metal centres when acting as a metalloligand while for 2, the X-ray structure confirms that the single uncoordinated (pendent) pyrazine nitrogen is also oriented for ready coordination to a second metal centre.

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Section: Resultsmentioning

confidence: 99%

Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)

Fanna

Smith

Zhang

et al. 2015

J Incl Phenom Macrocycl Chem

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“…The absence of hyperfine lines in the spectrum of complexes may be due to strong dipolar and exchange interaction between Cu(II) ions in the unit cell. The trend g|| > g⊥ > 2.002 observed for the complex under study indicates that the unpaired electron is localized in the dx 2 -y 2 orbital of Cu(II) ion 27 . Thus, EPR spectral data are in accordance with distorted octahedral geometry around Cu(II) ion 28 .…”

Section: Mass Spectramentioning

confidence: 93%

Synthesis, Characterization and Antimicrobial Studies of Novel Binuclear Transition Metal Complexes of Schiff Base Derived from 1-Amino-5-methyl-2,6-pyrimidine-dione and 2,3-Butanedione

Singh¹,

Srivastava²

2013

Asian J. Chem.

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CH3COO-and L = ligand) of a Schiff base ligand derived from 1-amino-5-methyl-2,6-pyrimidine-dione and 2,3-butanedione have been synthesized and characterized by elemental analysis, molar conductance measurements, magnetic moment measurements, IR, UV-visible, 1 H NMR, EPR and mass spectral studies. Electronic spectral data and magnetic moment values indicate octahedral geometry for all the metal complexes. In vitro antimicrobial activity of ligand and its metal complexes were also studied against bacteria (Bacillus subtilis and Escherichia coli) and fungi (Aspergillus niger and Aspergillus flavus) which show antimicrobial activity of ligand and binuclear metal complexes.

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“…We suggest that deprotonation of the -CH 2 -group adjacent to the imine, which must be the step preceding attack on the aldehyde, is facilitated by coordination of the imine N atom to Cd(II) which will result in a substantial d+ on the imine N atom, able to Such a step has been proposed before for migration of imine bond in some coordinated Schiff-base macrocycles, and is dependent on the coordination requirements of the metal ion involved [16]. On the other hand, to our knowledge, the reaction of an aldehyde with such a (transient) carbanion, and binding a new group to a carbon adjacent to the imine bond (and not to the imine itself) through such a C-C bond formation has been never reported for Schiff base compounds (Scheme 1).…”

Section: Introductionmentioning

confidence: 92%

A novel chelate-assisted C−C bond formation on a Cd(II) complex of an asymmetric heptadentate(N7) tripodal Schiff base ligand

Salehzadeh¹,

Ward²,

Adams³

2009

Inorganic Chemistry Communications

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Reactions at the azomethine CN bonds in the nickel(ii) and copper(ii) complexes of pyridine-containing Schiff-base macrocyclic ligands

Cited by 40 publications

References 70 publications

Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)

Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)

Synthesis, Characterization and Antimicrobial Studies of Novel Binuclear Transition Metal Complexes of Schiff Base Derived from 1-Amino-5-methyl-2,6-pyrimidine-dione and 2,3-Butanedione

A novel chelate-assisted C−C bond formation on a Cd(II) complex of an asymmetric heptadentate(N7) tripodal Schiff base ligand

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