LASER ACTIVE CYANOPYRROMETHENE-BF2 COMPLEXES

Treatment with a mixture of formic and hydrobromic acids converted ethyl 3,4-diethyl-5-methyl-pyrrole-2-carboxylate 7a to 3,3',4,4'-tetraerhyl-5,5'-dimethyl-pyrromethane hydrobromide 8a presumably via the condensation of alpha-unsubstituted and alpha-formylpyrrole intermediates 7c and 7e formed in situ. The corresponding 6-cyanohexaalkylpyrromethane 9a was obtained by the addition of hydrogen cyanide to the pyrromethene 8a and was oxidized with bromine to an unstable pyrromethene 10a, an intermediate converted to 1,2,6,7-tetraethyl-3,5-dimethyl-8-cyanopyrromethene-BF2 complex 3, (PM-TEDC), lambda(las) (plastic) 613-639 nm, in a reaction with boron trifluoride etherate. Ethyl 3,4,5-trimethylpyrrole-2-carboxylate 7b was similarly converted to 1,2,5,5,6,7-hexamethyl-8-cyanopyrromethene-BF2 complex 4, (PM-HMC), lambda(las) (plastic) 615-639 nm. Immediately after formation by a condensation between propionyl chloride and 2,4-dimethyl-3-cyanopyrrole 16, unstable 3,3',5,5'-tetramethyl-6-ethyl-4,4'-dicyanopyrromethene hydrochloride 17 was treated with boron trifluoride etherate to give 1,3,5,7-tetramethyl-2,6-dicyano-8-ethylpyrromethene-BF2 complex 18, lambda(las) (ethanol) 540-565 nm.