A reported variation of the electronic absorption spectra of diaza-aromatics in non-polar solvents with temperature appears to be explicable in terms of three effects. Hydrogen bonding interactions occur in all but exhaustively dried non-polar solvents. Microcrystals form readily at low temperatures at even quite low concentrations (c. 10-5M). The solutions are sensitive to exposure to light. The diaza-aromatics undergo photochemical change forming, in some cases, photoadducts with the solvent.

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