Geometry and Solvent Dependence of the Electronic Spectra of the Amide Group and Consequences for Peptide Circular Dichroism

2006 ◽  
Vol 110 (14) ◽  
pp. 4702-4711 ◽  
Author(s):  
Jiří Šebek ◽  
Zdeněk Kejík ◽  
Petr Bouř
Keyword(s):  
Circular Dichroism ◽  
Electronic Spectra ◽  
Amide Group ◽  
Solvent Dependence ◽  
Circular Dichroïsm

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.

Solvent-dependent circular dichroism of trans-disubstituted Bis(R-propane-1,2-diamine)cobalt(III) complexes

1977 ◽  
Vol 30 (10) ◽  
pp. 2115 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance ◽  
RM Peachey
Keyword(s):  
Circular Dichroism ◽  
Metal Ion ◽  
Ion Association ◽  
Positive Contribution ◽  
Circular Dichroism Spectra ◽  
Hydrogen Bond Formation ◽  
Rotational Strength ◽  
Solvent Dependence ◽  
Halide Salts ◽  
Circular Dichroïsm

The circular dichroism spectra of trans-disubstituted bis(R-propane- 1,2-diamine)cobalt(III) complexes are reported for an extended series of solvents. The observed variations in the spectra of the dichloro and dibromo complexes are analysed in terms of stereoselective solvation at the diamine N-H protons, and also the ion association between the complexes and their counter-ions. The solvation of these dihalo complexes, which was studied by p.m.r., showed a preference for hydrogen-bond formation with the equatorial N-H protons, rendering the donor nitrogens asymmetric and thus introducing a new source of dissymmetry close to the metal ion chromophore. This affected a decrease in the positive rotational strength of the 1A1g → 1Eg (D4h) transition, and a positive contribution to the rotational strength of the 1A1g → 1A2g (D4h) component. Ion association of the dihalo complexes was evaluated by a comparison of the circular dichroism of the tetraphenylborate and halide salts. ��� The tendency for ion association was much greater for the tripositive diammine complex. However, stereospecific solvation was of little importance and the circular dichroism spectra did not show any marked solvent dependence for the tetraphenylborate salt.

Tetraarylcyclobutadienecyclopentadienylcobalt Complexes: Synthesis, Electronic Spectra, Magnetic Circular Dichroism, Linear Dichroism, and TD DFT Calculations

2014 ◽  
Vol 33 (13) ◽  
pp. 3251-3264 ◽  
Author(s):  
Gregg S. Kottas ◽  
Thierry Brotin ◽  
Peter F. H. Schwab ◽  
Kamal Gala ◽  
Zdeněk Havlas ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Dft Calculations ◽  
Electronic Spectra ◽  
Magnetic Circular Dichroism ◽  
Linear Dichroism ◽  
Td Dft ◽  
Circular Dichroïsm
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