Pyrrolopyridazine derivatives as blue organic luminophores: synthesis and properties. Part 2

Two environmentally friendly methods, one in liquid and other in solid phase, for preparation of highly fluorescent pyrrolopyridazine (PP) derivatives under microwave (MW) irradiation is presented. The first synthesis in solid phase of fluorescent PP derivatives using activated alkynes under MW and conventional heating is also reported. Under MW irradiation the yields are higher, the amount of used solvent in liquid phase is at least five-fold less while solid phase does not use solvents, so these reactions may be considered as environmentally friendly. Eight new blue fluorescent 2-aryl-pyrrolopyridazine derivatives were synthesised. A certain influence of the PP substituents concerning absorption and fluorescent properties was observed. Introduction of a π-conjugated system in the second position of PP moiety increase the fluorescent properties. In the absorption spectra were observed a gradual decrease of wavelengths simultaneously with an increasing of molar extinction coefficient, due to increased number of ester groups from pyrrolic ring.