Ion Aggregate Spectra and Solvent Polarity

Ab initio and hybrid DFT study on the electronic states of fluorenone–Na complexes

“…7 The absorption spectra of FL interacting with alkali metal atoms have been extensively measured in several media because the spectra of FL are significantly clear compared with those of other carbonyl compounds. 8,9 From these experiments, two bands are found at visible region. From their concentration dependence, the peaks appearing at 525 and 450 nm are assigned to be the electronic transition of FL-Na monomer and that of the dimer, respectively.…”

“…Absorption spectra of FL-Na have been measured by several groups. 8,9 In tetrahydrofurane solution, FL-Na shows the absorption bands appearing at 525 and 450 nm. From the concentration dependence, the former and latter bands are attributed to FL-Na monomer and dimer bands, respectively.…”

“…However, details for the electronic transitions are still not clear because there is no theoretical explanation. 8,9 The structures and electronic states of the carbonyl compounds interacting with alkali metal atoms have been investigated by means of ab initio calculations. [10][11][12] In our previous papers, acetone-sodium, formaldehyde-sodium and formaldehyde-lithium have been investigated by means of ab initio MO and multi-reference configuration interaction (MR-CI) methods.…”

Black Swan in Phase Transfer Catalysis: Influence of Mixing Mode on the Stereoselectivity of Glycosylation

“…[37] Analysis of electronic effects of substituents in benzene ring [38] suggests that para-alkoxy substituents (σ p = À 0.27 for OMe, σ p = À 0.24 for OEt) behave as electron-donating moieties outperforming methyl (σ p = À 0.17), bromo (σ p = 0.23) and nitro (σ p = 0.78) groups. Apparently, this would make para-alkoxysubstituted phenols 2 a-c less acidic [39] diminishing the content of the phenoxide in the reaction mixture and making the Bu 4 N + -phenoxide ion pair [40] more tight. However, acidities of 4methoxyphenol (2 c) and 4-methylphenol (2 d) are similar [39] suggesting that it is not acidity/basicity of a phenol that determines its reactivity/nucleophilicity under conditions of PTC sialylation.…”

The photoexcited states of organic anions

“…Since, in addition, the cis-trans isomerization of olefins is one of the most efficient of known photochemical reactions,186 the observations of cis-trans isomerization at low temperature might be anticipated as a similarly efficient anionic photoprocess. Accordingly, Boche and Bieberbach were the first to observe such a reaction, in which the potassium salt of the c/s,c/s,c/s,frans- [9]annulene anion in THF at 15 °C (reaction 28)187 is converted to its all-cis isomer.187 Although this reaction (28) does occur thermally as well, the activation parameters under these reaction conditions clearly establish that no significant thermal isomerization could have occurred under the irradiation conditions.…”