Pyridazine ionization potential

The lone-pair peak separation of 1.04 eV, measured by means of photoelectron spectroscopy, was indicative of the presence of the rrans-fused conformation with an axial methyl group for l-methylperhydropyrido[l,2-fcjpyridazine (18) (79JA1874). Ionization potentials and the oxidation potential of l-methylperhydropyrido[l,2-h]pyridazine have been determined (79IJ45, 79JA1874 84JOC1891). 

In the photoelectron spectra of hydrazines, the separation between the two lone-pair-dominated ionization potentials is sensitive to the lone-pair-lone-pair dihedral angle (84JOC1891). In this connection, the photoelectron spectrum of perhydropyrazolo[l,2-a]pyridazine was consistent only with the presence of the trans-conformer (34) (74JA6982, 74JA6987 ... 

Studies on the tautomerism of pyridazines with potential tautomeric groups have continued. On the basis of recorded ionization constants and UV spectra of 3,4,5-trimercaptopyridazine and its derivatives, it is concluded that the compound exists as 3,4-dimercaptopyridazine-5(2f/)-thione. Tautomerism of hydroxy- and mercaptopyridazines was investigated with the aid of the corresponding anhydro bases as reference compounds. They exist predominantly in the -one or -thione forms. Similarly, the 3-mercapto-pyridazine-6(l/f)-thione structure in aqueous solution has been redeter-... 

The photoelectron spectrum of pyridazine is similar to those of pyrazine, pyrimidine, and triazine i.e., the lowest ionization potential corresponds to ionization of a lone-pair electron. The ionization potential is in agreement with the calculated value. These spectra were recorded also of pyridazine 1-oxide and 1,2-dioxide, and it was found that the perturbation of the t-system by the N—O group results in the separation of the lower excited states of the AT-oxide ions. ... 

Pyridazine and its derivatives have been extensively studied by a variety of computational methods to correlate the predicted values of their physical properties with the measured ones. As for other azines also for pyridazine several methods were used to calculate its thermodynamic stability, molecular geometry, electron density distribution, ionization potentials, and dipole moments (89KGS1587 91RRC399) and the significance of different criteria for assessing the 77-electron delocalization were also reviewed (92H1631). 

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