Table 1.

Photophysical properties of 4,5‐dihydropyridazine products.

		λ abs/λ em [a]	Stokes	Φ fl [b]	Intensity
R1	R2	[nm]	shift	[%]	increase
			[nm]
		545/628	83	0.55	13‐fold
		295/–	–	–	–
		546/626	80	0.52	18‐fold
		546/626	80	0.45	10‐fold
		566/643	77	0.21	threefold
		549/626	77	0.47	12‐fold

[a] Absorption and emission maxima were measured in CH₃CN/H₂O 1:1. [b] Relative fluorescence quantum yields were determined by using Nile Red in methanol as standard.