Excited state tautomerization of 7-azaindole in a 1:1 complex with δ-valerolactam: a comparative study with the homodimer.

A comparative analysis for relative stability between normal and tautomeric forms in the excited electronic states of 7-azaindole···δ-valerolactam 1:1 complex and 7-azaindole homodimer has been presented. The tautomeric configuration of the complex is estimated to be ~6 kcal/mol more stable than normal form, and the same for homodimer appears to be ~10 kcal/mol. Consistent with these estimates both the complex and homodimer undergo facile double proton transfer tautomerization upon UV excitation in hydrocarbon solutions (Chou; et al.

UV photolysis of α-cyclohexanedione in the gas phase.

Ultraviolet absorption spectrum of α-cyclohexanedione (α-CHD) vapor in the wavelength range of 220-320 nm has been recorded in a 1 m long path gas cell at room temperature. With the aid of theoretical calculation, the band has been assigned to the S(2) ← S(0) transition of largely ππ* type. The absorption cross section at the band maximum (∼258 nm) is nearly 3 orders of magnitude larger compared to that for the S(2) ← S(0) transition of a linear α-diketo prototype, 2,3-pentanedione.

Inhibition of light-induced tautomerization of 7-azaindole by phenol: indications of proton-coupled electron/energy transfer quenching.

The photophysical behavior of a 1:1 complex between phenol and 7-azaindole (7AI) has been investigated in methylcyclohexane solutions at temperatures in the range of 27 to -50 °C. A linear Benesi-Hildebrand plot associated with changes in absorbance of the complex with phenol concentration in the solutions ensures 1:1 stoichiometry of the produced complex. Our estimate for the value of the association constant (K(a)) of the complex is ~120 M⁻¹ at 27 °C, and it is nearly twice compared to that for 1:1 complex between 7AI and ethanol measured under the same condition.

Blue shifting C-H...O hydrogen bonded complexes between chloroform and small cyclic ketones: ring-size effects on stability and spectral shifts.

Blue-shifting C-H...