The Effects of Electrolytes on Circular Dichroism Curves of Cationic Complex Ions

Smith, Herbert L.; Douglas, Bodie E.

doi:10.1021/ic50039a020

Cited by 22 publications

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“…Our experimental and computational study of Co(en) 3 3+ agrees with previous X-ray, 11,29 NMR, 19 and electronic CD 20,21 studies, which have been used to identify the absolute configuration, assign solution conformations and study the effects of temperature and counterion concentration on the solution structure. However, these other methods cannot be used to identify the mode of chloride association with Co(en) 3 3+ in solution.…”

Section: Discussionsupporting

confidence: 86%

“…NMR studies indicate that 60−70% of the en rings are δ for complexes with a Λ-configuration. From their effect on NMR 19 and electronic CD spectra, , counterions have been deduced to influence the en ring conformation in tris-chelated Co(III) complexes in solution. However, the specific nature of this interaction cannot be determined from those measurements.…”

Section: Introductionmentioning

confidence: 99%

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Density Functional Theory Calculations of Vibrational Circular Dichroism in Transition Metal Complexes: Identification of Solution Conformations and Mode of Chloride Ion Association for (+)-Tris(ethylenediaminato)cobalt(III)

et al. 2002

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Density functional theory calculations of the vibrational circular dichroism (VCD) spectra of a transition metal complex, (+)-tris(ethylenediaminato)cobalt(III) as a free ion and with associated chloride ions, are reported. By comparison with experimental data obtained in our laboratory in 1986 (Young et al. J. Am. Chem. Soc. 1986, 108, 7255) and new measurements, this study identifies, for the first time, the geometry and absolute configuration of the association complex as Λ-δδδ-Co(en)3Cl2 +, in which two chloride ions each associate with three NH bonds along the C 3-axis of a D 3-symmetry complex. The DFT calculations, carried out with both the LanL2DZ and 6-31G(d)[C, H, N]/Stuttgart ECP [Co] basis sets, predict the energy order of ethylenediamine ring conformations as λλλ < λλδ < λδδ < δδδ for the free (gas phase) Λ-Co(en)3 3+ ion, an order opposite to that deduced from solution studies. The VCD studies identify the δ-conformation as the most prevalent in solution for halide and sulfate counterions, suggesting an interaction with solvent or weakly associated counterions that stabilizes this conformation.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Calculations of Vibrational Circular Dichroism in Transition Metal Complexes: Identification of Solution Conformations and Mode of Chloride Ion Association for (+)-Tris(ethylenediaminato)cobalt(III)

et al. 2002

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“…The tris(ethylenediaminato)cobalt(III) complex, [Co(en) 3 ] 3+ , is a prototype chiral transition metal complex. Over the years, its optical activity has been extensively studied using spectroscopic techniques like anomalous X-ray, 17,18 electronic circular dichroism, [19][20][21][22][23][24] NMR, [25][26][27] and VCD. 28,29 The configurations of the [Co(en) 3 ] 3+ complex can be classified as follows.…”

Section: Introductionmentioning

confidence: 99%