Synthesis and characterization of chiral nickel(II) Schiff base complexes and their CD spectra-absolute configuration correlations

Fang, Wang; Zhang, Hui; Li, Li; Hao, Hong-Qing; Wang, Xian-Ying; Jian-gu, Chen

doi:10.1016/j.tetasy.2006.07.021

Cited by 24 publications

(15 citation statements)

References 18 publications

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“…The split of the d-d transition in the CD spectrum is due to the asymmetric coordination environment of the Cu(II) ion. 30,31,33 As expected, compound 2b displays Cotton effects of the opposite sign at the same wavelengths. 20 The high CD intensity of the d-d transitions can be ascribed to metal-ligand (antibonding) orbital interactions that result in (out-of-phase) mixing of ligand p and/or s orbitals with the d orbitals.…”

Section: Uv-visible Spectra Circular Dichroism Spectra and The Excisupporting

confidence: 79%

“…The intense negative band at 213 nm is primarily a p-p* transition. 30,31,33 As expected, compound 2b displays Cotton effects of the opposite sign at the same wavelengths.…”

Section: Uv-visible Spectra Circular Dichroism Spectra and The Excisupporting

confidence: 79%

“…20 The high CD intensity of the d-d transitions can be ascribed to metal-ligand (antibonding) orbital interactions that result in (out-of-phase) mixing of ligand p and/or s orbitals with the d orbitals. 33,34 The band at 373 nm (negative Cotton effect) can be assigned as the ligand-metal charge transfer band at 370 nm. The intense negative band at 213 nm is primarily a p-p* transition.…”

Section: Uv-visible Spectra Circular Dichroism Spectra and The Excimentioning

confidence: 99%

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Vibrational and electronic circular dichroism monitoring of copper(II) coordination with a chiral ligand

Zhang

et al. 2012

Chirality

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Novel copper(II) coordination compounds with chiral macrocyclic imine ligands derived from R-/S-camphor were asymmetrically synthesized and characterized with the aid of chiroptical spectroscopies. Crystal structures of both enantiomers were determined by single crystal X-ray diffraction analysis. Circular dichroism (CD) spectra were analyzed using a simplified exciton model as well as quantum chemical computations. The absolute configuration of the copper(II) coordination compounds determined from CD was found consistent with the crystal data. The copper(II) complexes were further investigated by vibrational CD (VCD) measurement combined with density functional theory calculation. The complex formation was evidenced by spectral shifts of the characteristic bands in the CD and VCD spectra.

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Section: Uv-visible Spectra Circular Dichroism Spectra and The Excisupporting

confidence: 79%

“…The intense negative band at 213 nm is primarily a p-p* transition. 30,31,33 As expected, compound 2b displays Cotton effects of the opposite sign at the same wavelengths.…”

Section: Uv-visible Spectra Circular Dichroism Spectra and The Excisupporting

confidence: 79%

Section: Uv-visible Spectra Circular Dichroism Spectra and The Excimentioning

confidence: 99%

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Vibrational and electronic circular dichroism monitoring of copper(II) coordination with a chiral ligand

Zhang

et al. 2012

Chirality

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“…However, the reported examples of induced diastereoselection in Ni II chiral‐ N , O ‐chelate complexes are limited to mononuclear four‐coordinate tetrahedral to distorted square‐planar geometries 7c,8,13. Although two examples of six‐coordinate dinuclear μ‐aqua‐bis[ N ‐(Ar)‐5‐nitrosalicylaldiminato]dinickel(II)19 complexes are available, no such diastereoselection in octahedral mono‐ or dinuclear Ni II ( R or S )‐ N , O ‐chelate complexes has been reported in either the solid state or in solution.…”

Section: Introductionmentioning

confidence: 99%

Syntheses, Spectroscopy, and Structural Analyses of Dinuclear Chiral‐at‐Metal μ‐Aqua‐tetrakis[(R or S)‐N‐1‐(Ar)ethylsalicylaldiminato]di‐Λ‐ or ‐Δ‐nickel(II) Complexes

et al. 2015

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Enantiopure dinuclear μ‐aqua‐tetrakis[(R or S)‐N‐1‐(Ar)ethylsalicylaldiminato]di‐Λ‐ or ‐Δ‐nickel(II) [Ar = C6H5 (R‐1/S‐1), p‐MeOC6H4 (R‐2/S‐2), p‐ClC6H4 (R‐3/S‐3), p‐BrC6H4 (R‐4)] complexes have been synthesized from the reaction between (R or S)‐N‐1‐(Ar)ethylsalicylaldimine and nickel(II) acetate. Their CD spectra demonstrate chirality transfer from the ligands to the metal ions and a mirror‐image relationship for the enantiomeric pair R‐3/S‐3 in thf. DSC analyses show that the complexes exhibit an irreversible dissociation to the mononuclear species, which in turn undergo decomposition. The 1H NMR spectra reveal the presence of four salicylaldiminates, one aqua ligand, and two molecules of methanol in each dinuclear complex. They also confirm the existence of a dinuclear‐bridged aqua bis‐octahedral NiII complex in solution. The IR spectra in CH2Cl2 show a very strong band at around 2306 cm–1 due to the νO–H of the bridged aqua ligand. The X‐ray structures of R‐2, S‐2, R‐3, and S‐3 confirm the formation of dinuclear compounds comprising two nickel ions, four salicylaldiminates, and one aqua ligand with two molecules of methanol (or water in S‐2). Each nickel ion is surrounded by two N,O‐chelating salicylaldiminates, a bridging salicyl‐O atom from the neighboring nickel ion, and a bridging aqua ligand in a distorted octahedral polyhedron. Analyses of the absolute structures reveal a diastereomeric induction of the R or S ligand giving a Λ or Δ configuration at the nickel atoms in R‐2/3 or S‐2/3 that is independent of the ligand substituents.

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“…The work of Hoss and Elias has revealed that square planar Ni(N–alkyl Sal) 2 complexes are co‐ordinatively unsaturated and add on nitrogen donor ligands to produce six‐coordinate complexes . Metal complexes containing Schiff base ligands have gained significance in view of varied range of applications, structural chemistry, catalysis, chemical and photochemical reactions, magnetism, gas storage, chemically modified electrodes, etc. Imines play important roles in biological processes.…”

Section: Introductionmentioning

confidence: 99%

Activation of – N=CH – bond in a Schiff base by divalent nickel monitored by NMR evidence

Chandrakala

Gowda²,

Murthy³

et al. 2012

Magnetic Reson in Chemistry

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The Schiff base, 2-salicylidene-4-aminophenyl benzimidazole in ethanol undergoes activation of -N=CH- bond by Ni(2+) in the presence of ammonia or primary alkyl amine to produce nickel complexes of the formula Ni{o-C(6)H(4)(O)CH NR}(2) . n H(2)O [R = H, Me; n = 0; R = Et, n = 0.5] and 4-aminophenyl benzimidazole. The products have been identified by elemental analysis, magnetic susceptibility measurements and IR, ESR, mass and extensive NMR spectral studies. The possible mechanism for the activation of -N=CH- bond has also been proposed.

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Synthesis and characterization of chiral nickel(II) Schiff base complexes and their CD spectra-absolute configuration correlations

Cited by 24 publications

References 18 publications

Vibrational and electronic circular dichroism monitoring of copper(II) coordination with a chiral ligand

Vibrational and electronic circular dichroism monitoring of copper(II) coordination with a chiral ligand

Syntheses, Spectroscopy, and Structural Analyses of Dinuclear Chiral‐at‐Metal μ‐Aqua‐tetrakis[(R or S)‐N‐1‐(Ar)ethylsalicylaldiminato]di‐Λ‐ or ‐Δ‐nickel(II) Complexes

Activation of – N=CH – bond in a Schiff base by divalent nickel monitored by NMR evidence

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