Hydrogen bonding and the n → p* blue shift in a,b-unsaturated ketones. II. Franck-Condon factors and estimates of the effects of hydrogen bonding on CO bond lengths

Beecham, A.F.; Hurley, AC; Johnson, Chj

doi:10.1071/ch9800699

Cited by 8 publications

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“…This is possibly due to blue shifting of the OTC aqueous phase spectrum upon adsorption to the interface, which has been shown to occur in hydrogen bonding interactions of n-π* systems induced by small changes in the bond lengths of the ground and excited states. 71 This effect has been shown in computational studies to be most significant for proton acceptors at moderately basic pH. 72 In this case, the detected SHG resonance centered around 307 nm would be due to a blue-shifted BCD transition.…”

Section: Resultsmentioning

confidence: 91%

“…The SHG spectrum for OTC, however, does not appear to match the respective bulk spectrum at pH 8, which shows peaks at approximately 275 and 360 nm (top trace in Figure ). This is possibly due to blue shifting of the OTC aqueous phase spectrum upon adsorption to the interface, which has been shown to occur in hydrogen bonding interactions of n −π* systems induced by small changes in the bond lengths of the ground and excited states . This effect has been shown in computational studies to be most significant for proton acceptors at moderately basic pH .…”

Section: Resultsmentioning

confidence: 98%

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Tracking Oxytetracyline Mobility Across Environmental Interfaces by Second Harmonic Generation

2006

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This work examines the binding behavior of the antibiotic oxytetracycline (OTC) to mineral oxide/water interfaces in the presence and absence of organic functional groups using the interface-specific technique second harmonic generation (SHG). Studies show that OTC binding to fused quartz, methyl ester, carboxylic acid, and alkyl interfaces is fully reversible and highly dependent on solution pH, with appreciable adsorption occurring only at pH 8. Relative surface coverage at pH 8 is highest for the polar organic-functionalized surfaces, and surface saturation occurs for the methyl ester-functionalized fused quartz/water interface at 2 x 10(-5) M. Adsorption isotherm measurements indicate that the binding process is controlled by hydrogen bonding and hydrophobic interactions, with free energies of adsorption on the order of -40 kJ/mol for all interfaces studied. The results indicate that OTC transport in the environment will depend heavily on soil pH and composition and have implications for the development of bacterial antibiotic resistance.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 98%

Tracking Oxytetracyline Mobility Across Environmental Interfaces by Second Harmonic Generation

2006

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“…The most striking difference between the ET spectra of the two isomers is that the energy of electron attachment into the b, orbital of the cis isomer is 0.55 eV lower than that of the corresponding au orbital of the trans isomer. 7 To aid in the interpretation of these results it is useful to refer to the ir* MO's of the cis isomer (Chart I). 8 Of the three ir* MO's, the b[(ir*2) orbital has the largest charge densities on the C2 and C5 atoms.…”

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“…These observations are incompatible with the traditional viewpoint outlined above: the absence of a shift in Tt implies that the excited state remains hydrogen bonded and a blue shift occurs because the geometries of the ground and excited states of the solute are affected differently by hydrogen bonding. A model calculation was used in ref 7 to predict an extension of the excited state carbonyl CO bond due to hydrogen bonding.…”

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Electron transmission spectroscopy of 1,3,5-hexatriene: isomeric differences in .pi. orbital energies

Burrow¹,

Jordan²

1982

J. Am. Chem. Soc.

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Moreover, the distance found between neighboring columns (d = 34 Á) is quite in accordance with the expected molecular parameters of the constituting molecules. In the large-angle region, X-ray diffraction measurements also show two broad and diffuse rings. The first one corresponds to a spacing of 5 Á, which is characteristic of paraffinic moieties in a disordered state. The second ring at 3.8 Á is presumably related to the stacking of the macrocyclic subunits within the columns. The density of the complex Ib has been measured by a flotation technique in binary mixtures water/dimethylformamide (p = 0.98 ± 0.01 g cm"3). Knowing the periodicity of the hexagonal lattic previously determined, it is possible to calculate the mean stacking distance of the molecules along the axis of the columns. The value of 3.7 Á which is found in that way is in good agreement with the distance obtained from the X-ray patterns. The structure of the mesophase seems to remain unchanged from about 60 to 300 °C. As far as we know no other discotic phase is stable over such an extended range of temperature.In conclusion, a new type of discotic mesophase has been prepared and characterized. Metallophalocyanine subunits are used to constitute their rigid core. Doped liquid crystals have been prepared by recrystallizing the substituted phthalocyanine from heptane containing small amounts of iodine. Preliminary electron spin resonance measurements indicate a good mobility of the charge carriers inside each column. Conductivity studies are under progress to further elucidate the electrical properties of these new mesophases.Acknowledgment. CNRS and PIRDES are acknowledged for their financial support. Mrs. Pouyet and Mr Schneider are thanked for their helpful assistance.

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Optical Activity of Oriented Molecules. 10.Analysis of the n‐π Transition of 4‐en‐3‐one Steroids and Comparison of the Order Parameters of Host and Guest in a Compensated Nematic Phase

Altschuh

Weiland

Kosack

et al. 1984

Ber Bunsenges Phys Chem

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Anisotropic sample / Liquid Crystals / Order parameters / Spectroscopy, CD-ORD / Spectroscopy, UltravioletWhile different substitution in the 17 p-position of 4-en-3-one steroids (testosterones, progesterones) does not influence the CD spectra, the CD of the anisotropic solutions (ACD) undergoes a drastic variation of the band shape connected with a change from negative to positive curves. From this variation and the wavelength dependence of the degree of polarization of the UV spectra results that at least two progressions of vibrations (iim + nii, and Vo0 + 1, + n 1 , ) are responsible for the band structure of the n-A* transition of the 4-en-3-one chromophore where the totally symmetric (Y1) and the non-totally symmetric vibration (V,) are about 1200 and 600 cm-', respectively. Furthermore, this variation of the ACD spectra for constant temperature and solute (guest) to solvent (host: cholesteryl chloride/cholesteryl laurate) ratio is a consequence of a change of the order parameter of the guest and the host which have been determined in the same solution by ACD and AORD, respectively. Most variation of the guest order can be understood by the proportionality to the anisotropy of the polarizability 2a33-a22-a,, or the length to width ratio 2/3-/2-/, if no hydroxy group is present. Here a very high order exists. For some compounds the high order of the guest is connected with a strong decrease of the host order. In general, the alteration of the host order is not a function of the order of the guest i.e. at least one molecular property responsible for the ordering of the guest should be different from those properties of the guest which alterate the order of the host.

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Hydrogen bonding and the n → p* blue shift in a,b-unsaturated ketones. II. Franck-Condon factors and estimates of the effects of hydrogen bonding on CO bond lengths

Cited by 8 publications

References 0 publications

Tracking Oxytetracyline Mobility Across Environmental Interfaces by Second Harmonic Generation

Tracking Oxytetracyline Mobility Across Environmental Interfaces by Second Harmonic Generation

Electron transmission spectroscopy of 1,3,5-hexatriene: isomeric differences in .pi. orbital energies

Optical Activity of Oriented Molecules. 10.Analysis of the n‐π Transition of 4‐en‐3‐one Steroids and Comparison of the Order Parameters of Host and Guest in a Compensated Nematic Phase

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