Circular dichroism spectra of 2-substituted propionatopentaaminocobalt(II) complexes

1971 ◽  
Vol 24 (11) ◽  
pp. 2275 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance
Keyword(s):  
Aqueous Solution ◽  
Circular Dichroism ◽  
Absorption Band ◽  
General Formula ◽  
Optically Active ◽  
Sign Pattern ◽  
Circular Dichroism Spectra ◽  
Cotton Effects ◽  
Circular Dichroïsm

The preparations of a series of optically active complexes with the general formula Co(NH3)5(OCOCH(X)CH3)2+ are reported for X = NH3+, OH, F, Cl, Br, C2H5, and C6H5. The circular dichroism spectra of the complexes have been measured in aqueous solution, in the presence of salts of polarizable anions, and in KBr disks. The spectra have been analysed in terms of three Cotton effects under the 1A1g → 1T1g cubic absorption band and found to be consistent with a +, -, - sign pattern for the L- isomer, corresponding to the two components of the 1A1g → 1Eg (D4h) and to the 1A1g → A2g (D4h) transition, respectively.

Circular dichroism spectra of amino acid complexes. II. Chelated amino acid complexes with the CoN5O chromophore

1970 ◽  
Vol 23 (9) ◽  
pp. 1735 ◽  
Author(s):  
CJ Hawkins ◽  
PJ Lawson
Keyword(s):  
Amino Acids ◽  
Circular Dichroism ◽  
Amino Acid ◽  
Visible Region ◽  
Optically Active ◽  
Circular Dichroism Spectra ◽  
Amino Acid Complexes ◽  
Similar Series ◽  
Cotton Effects ◽  
Circular Dichroïsm

The circular dichroism spectra of a series of optically active (α-aminocarboxylato)tetraamminecobalt(111) complexes have been measured in aqueous solution, and in the presence of salts of polarizable anions. The observed spectra in the visible region have been analysed to determine the signs of the Cotton effects of the three components of the 1A1g ↔ 1T1g cobalt(111) transition. For L-amino acids, the transition with A2g(D4h) parentage is negative, and the two transitions with Eg(D4h) parentage have opposite signs. Published circular dichroism spectra of complexes of the type [Co(en)2(L-am)]2+ were similarly interpreted in terms of a perturbed tetragonal chromophore, and it was shown that the vicinal effect of the L-amino acids imposed the same signs onto the component transitions as for the tetraammines and for a similar series of pentaamminecobalt(111) complexes.

Circular dichroism spectra of amino acid complexes. III. Copper(II) compounds

1970 ◽  
Vol 23 (11) ◽  
pp. 2237 ◽  
Author(s):  
CJ Hawkins ◽  
CL Wong
Keyword(s):  
Amino Acids ◽  
Circular Dichroism ◽  
Amino Acid ◽  
Sign Pattern ◽  
Circular Dichroism Spectra ◽  
Amino Acid Complexes ◽  
Rotational Strength ◽  
Conformational Effects ◽  
Cotton Effects ◽  
Circular Dichroïsm

The solution circular dichroism spectra of the 1 : 1 and 1 : 2 copper(II) complexes of a series of �-amino acids are reported for the region 12500-25000 cm-1. These spectra and spectra of the isolated 1 : 2 complexes dispersed in KBr disks have been interpreted as arising from three Cotton effects with a -,+,- sign pattern for the L configuration, except for the L-proline spectra, which were analysed in terms of a +,-,+ pattern. A tentative assignment is made for these Cotton effects, and the relative contributions of vicinal and conformational effects to the rotational strength are discussed.

Circular dichroism spectra of asymmetric unidentate amine complexes of cobalt(III)

1973 ◽  
Vol 26 (11) ◽  
pp. 2401 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance
Keyword(s):  
Circular Dichroism ◽  
Absorption Band ◽  
Aromatic Compounds ◽  
Visible Region ◽  
The Other ◽  
Circular Dichroism Spectra ◽  
Alkyl Derivatives ◽  
Cotton Effects ◽  
Circular Dichroïsm ◽  
Rotational Strengths

The preparations of pentaamminecobalt(III) complexes of a series of asymmetric unidentate amines are reported. The circular dichroism spectra for the (S)-amines show negative Cotton effects under the 1A1g → 1T1g absorption band, which are somewhat solvent dependent but independent of temperature down to -190�C. The vicinal effect from 1- cyclohexylethylamine was comparable to that from analogous aromatic compounds, but the simpler alkyl derivatives were found to impose smaller rotational strengths on the d-d transitions. The lack of measurable c.d. in the visible region for tetraammine((S)-butane-1,3- diamine)cobalt(III) is reported and discussed in the light of the other studies.

Circular dichroism spectra of tetraamminecobalt(III) complexes of amino alcohols

1978 ◽  
Vol 31 (11) ◽  
pp. 2399 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance ◽  
JA Palmer
Keyword(s):  
Circular Dichroism ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Amino Alcohols ◽  
Circular Dichroism Spectra ◽  
Chemical Shift Difference ◽  
Solvent Dependence ◽  
Cotton Effects ◽  
Circular Dichroïsm ◽  
Chiral Amino Alcohols

The circular dichroism spectra are reported for tetraamminecobalt(III) complexes with the chiral amino alcohols 2-aminopropan-1-ol, 2- aminobutan-1-ol, 1-aminopropan-2-ol, 2-amino-1-phenyl-ethanol, ψ- ephedrine and ephedrine with the alcohol groups protonated (OH) and deprotonated (O-). The solvent dependence of the chemical shifts of the NH protons was investigated to determine the effects of stereoselective solvation on the circular dichroism, but, in contrast to some other related systems, the chemical shift difference between the two NH2 protons was relatively insensitive to solvent. Consistent with this, the circular dichroism spectra of the tetraphenylborate salts of the deprotonated complexes were found not to be markedly dependent on solvent. Tetraammine-{(-)-ψ-ephedrine)cobalt(III) and tetraammine{(-)- ephedrine}cobalt(III) were found to have the same signs of Cotton effects for the various d-d transitions, whereas bis{(-)-ψ- ephedrine}copper(II) and bis{(-)-ephedrine}copper(II) had opposite signs. This has been explained in terms of different conformer populations in the cobalt(III) and copper(II) systems.

Circulardichroismusuntersuchungen von Polyalkohol- und Zucker-Vanadat(V)-Komplexen / Circular Dichroism Studies of Polyalcohol and Sugar Vanadate(V) Complexes

1989 ◽  
Vol 44 (11) ◽  
pp. 1464-1472 ◽  
Author(s):  
Hermann Bauer ◽  
Jeanine Brun ◽  
Alexius R. Hernanto ◽  
Wolfgang Voelter ◽  
Spyridon Paraskewas
Keyword(s):  
Circular Dichroism ◽  
Wavelength Range ◽  
Optically Active ◽  
Hydroxyl Groups ◽  
Pyranose Ring ◽  
Cotton Effects ◽  
Circular Dichroïsm

The complexes of tetravanadate ions with optically active polyols and carbohydrates with suitable steric properties show up to four separate cotton effects in the wavelength range of λ = 200-350 nm. Thus it is possible to classify pyranoses into four groups according to their circular dichroitic behaviour and determine the configuration and the conformation of the hydroxyl groups attached to the pyranose ring.

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