Pyridazine, electronic spectra

The association constant of pyridazine with ethanol was found to be 4.9 (from electronic absorption spectra) and 6.8 (infrared absorption spectra), and the corresponding values for the strength of the hydrogen bond are 4.2 and 4.6 kcal. The hydrogen-bonded form of P3n-idazine was considered to comprise one alcohol at one azine-nitrogen at small mole ratios of alcohol to azine and to involve the second nitrogen at high mole ratios (an additional shift in the electronic spectrum. The association constants (3.1-3.8) of pyridine, quinoline, and isoquinoline with methanol in carbon tetrachloride have been determined by infrared spectroscopy. 

Several new, low-lying electronic states of pyridazine were identified by comparison of its V/UV spectra and near-threshold electron-energy-loss spectra (91MI7) and (it, n) states of pyridazine were studied theoretically by ab initio CIS calculations of its electronic spectrum (95CP183). 

The photoelectron spectra of pyridazine have been interpreted on the basis of many-body Green s function calculations both for the outer and the inner valence region. The calculations confirm that ionization of the first n-electron occurs at lower energy than of the first TT-electron (79MI21201). A large number of bands in the photoelectron spectrum of 3,6-diphenylpyridazine in stretched polymer sheets have been assigned to transitions predicted... 

Solvent effects on the fluorescence spectrum and the effect of protonation on electron density and chemical shift in NMR spectrum of pyridazine were investigated. 

The spectra of pyrazine, pyrimidine, and pyridazine, all in cyclohexane, are compared by Albert (1462). They show two bands with associated fine structure, the peaks for pyrazine center around 260 and 328 nm. The near-ultraviolet spectrum of pyrazine has been measured in several solvents [and at various pH values (1463)] and the transitions assigned (1474, 1482). The diffuse system at 260 nm has been attributed to rr->-7r transitions whereas the sharp system at 328 nm has been ascribed to n rr transitions (1467, 1474). Semiempirical calculations have been made on the electronic structure of pyrazine with reference to its -> rr transition (1483-1486), calculations have been made of transition energies in N-... 

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. ... 

High-pressure mass spectrometry was used to measure the equilibration constants for the electron transfer between di- and polyalkylpyridazines and their cation radicals (88JA7945). Mass-resolved excitation spectrum was also used to determine the lifetime of the Rydberg state of pyridazine (95JCP4907). 

UV spectra of pyridazines and pyridazinones were recorded, and solvent effects on spectra were examined. 644-652 The absorption spectrum of the pyridazine radical was reported.653 Resonance fluorescence has been observed from pyridazine vapor.654 Electron transmission spectroscopy has... 

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