Cinnoline energy calculations

Energy Calculations. Because cinnoline is insufficiently stable for experimental study, the total and bond separation energies for cinnoline have been calculated for comparison with those of related heterocycles. Highest occupied molecular orbital (HOMO) energies have been used to calculate pXa values for cinnoline and other benzodiazines. ... 

AMI calculations have been performed on pyrazino[2.3-c]pyridazine and its N-protonated species.2 Energy levels and charge densities were calculated by Hiickel MO calculations.3 MNDO calculations have also been performed on a benzo-annulated pyrazino[2,3-c]pyridazine (quinoxalino[2,3-c]cinnoline).69... 

The polarographic reduction of quinoxaline and its derivatives has been studied by a number of workers. Half-wave electrode potentials are pH dependent and over the pH range of 1 to 10, Ei has been reported to vary from —0.254 to -0.863 The half-wave electrode potential in anhydrous dimethylformamide is — l.bOV for quinoxaline, —1.06 V for cinnoline, —1.41V for phthalazine, and —1.22 V for quinazoline. The benzodiazines are more easily reduced than the corresponding diazines, thus pyrazine has a half-wave electrode potential of -1.57V. Pyridine with a half-wave potential of —2.15 V is still more difficult to reduce. The reversible reduction potential of quinoxaline as determined by cyclic voltammetry is -1.097 V. The observed energy differences between azine and radical anion are well correlated with the results of CNDO and SCF iT-electron calculations. 

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