Cotton effects of the benzene chromophore in the 300-185-nm spectral region

Salvadori, Piero; Lardicci, L.; Menicagli, R.; Bertucci, Carlo

doi:10.1021/ja00779a062

Cited by 30 publications

(15 citation statements)

References 1 publication

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“…1d). 24 For 1 and 3, three minima with DFT energy within 2 kcal/mol were found (Table 1), the most stable one having C2 0 À ÀC1 0 À ÀC1À ÀH1 dihedral close to 08 (H1 eclipsed with the ring). For 2, five minima were found, the most stable one again with C2 0 À ÀC1 0 À ÀC1À ÀH1 dihedral close to 08 (Table 1).…”

Section: Geometry Optimizationsmentioning

confidence: 98%

“…It is noteworthy that, to the best of our knowledge, the CD spectrum of (S)-2,2-dimethyl-3-phenylbutane (4, see Chart) reported by one of us in 1972 still remains the only published CD spectrum belonging to the above category. 24 Here we report the CD spectra of the smaller homologues 25 (R)-1-3 (see Chart) based on a similar chiral pattern, i.e., the a-phenylethyl with an ethyl (1), n-propyl (2), isopropyl (3), and tert-butyl (4) group attached at the chiral center; we then check the consistency of 1 L a and 1 L b Cotton effects measured for 1-3 with the relative sector rules. Second, we test the performance of TDDFT method (without including vibronic structure calculations) 26,27 in the prediction of CD spectra of compounds 1-4.…”

Section: Introductionmentioning

confidence: 99%

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The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

2007

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The CD spectra of the series PhCH(Me)R, with R = Et (1), nPr (2), iPr (3), and tBu (4), are reported (1-3 for the first time) at room temperature in the 185-280 nm range and at 183 K. These purely hydrocarbon compounds represent the simplest chiral systems containing the phenyl chromophore and exhibit Cotton effects exclusively allied with the benzene transitions. The bands in 1La and 1Lb regions were checked against the available sector rules, with discordant outcomes. Time-dependent density-functional theory calculations, with various functionals and basis sets tested, correctly reproduced the prominent CD bands observed for 1-4.

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Section: Geometry Optimizationsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

2007

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“…CD spectroscopy did not provide conclusive results due to the strong absorption of the phenyl groups around 200 nm, [18] which partially covered the variation of the CD spectra and the reversal of the Cotton effect associated with the chain length increase ( Figure S7 in the Supporting Information).…”

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confidence: 99%

Nanofibers from Oxazolidi‐2‐one Containing Hybrid Foldamers: What is the Right Molecular Size?

Angelici

Falini

Hofmann

et al. 2009

Chemistry A European J

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A series of oligomers of the type Boc-(L-Phe-D-Oxd)(n)-OBn (Boc = tert-butoxycarbonyl; Oxd = 4-methyl-5-carboxy oxazolidin-2-one; Bn = benzyl) were prepared for n = 2-5. The shortest oligomer, Boc-(L-Phe-D-Oxd)(2)-OBn, aggregates and forms a fiber-like material with an anti-parallel beta-sheet structure in which the oligopeptide units are connected to each other by only one intermolecular hydrogen bond. The longer oligomers exhibit structural heterogeneity. They start to organize into secondary structures by the formation of intramolecular hydrogen bonds at the pentamer level. Microscopy and diffraction of the oligomers indicated a crystalline character for only the shorter ones.

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“…[69] In conclusion, in the higher oligomers, the tendency to form ordered secondary structures increases and seems to be fully manifested at the pentamer level. Information on the preferred conformations in solution was obtained by FTIR, 1 H NMR and CD techniques.…”

Section: Oligomers Of the Boc-(l-phe-d-oxd) N -Obn Seriesmentioning

confidence: 82%

Foldamers Based on Oxazolidin‐2‐ones

2011

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Foldamers are artificial molecules capable of organization into well defined secondary structures such as helixes, β sheets and turns. The essential requirement for an oligomer to qualify for inclusion in the foldamer family is to possess a well defined, repetitive secondary structure, imparted by conformational restrictions imposed by the monomeric unit. These compounds may be composed of subunits of any kind, but most of them contain unusual amino acids and/or aromatic units. We describe the synthesis, the conformation analysis and the physical properties (in the solid state) of pseudopeptide foldamers containing imido‐type functions, obtained by coupling the nitrogen of a 4‐carboxy oxazolidin‐2‐one unit with the carboxylic acid moiety of the next unit, which may be another 4‐carboxy oxazolidin‐2‐one or an amino acid. Such an imido‐type function is characterized by a nitrogen atom connected both to an endocyclic and to an exocyclic carbonyl group, and tends always to adopt the trans conformation. As a consequence of this remarkable property, which causes local constraint, these imido‐type oligomers are forced to fold in ordered conformations. In combination with interactions of other kinds (H bond, apolar interactions, etc.), these lead to the formation of supramolecular materials. The synthetic approach is highly tuneable with endless variations, so materials with required properties may be prepared “on demand”, simply by changing the design and the synthesis.

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Cotton effects of the benzene chromophore in the 300-185-nm spectral region

Cited by 30 publications

References 1 publication

The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

Nanofibers from Oxazolidi‐2‐one Containing Hybrid Foldamers: What is the Right Molecular Size?

Foldamers Based on Oxazolidin‐2‐ones

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