Spectroscopic and Magnetic Resonance Elucidation of the Structure of the Polymer Derived from 1,2-Dihydro-4-(4-Hydroxyphenyl)-1-oxo-(2H)-Phthalazine and Bis(4-Fluorophenyl)Sulfone

Two model compounds 4,4′-[sulfonylbis(4′-phenyleneoxy-4-phenylene)]-bis[1,2-dihydro-1-oxo-2-phenyl-(2H)-phthalazine] (13)and 4-(4-methoxyphenyl)-1-(4-methylphenoxy)phthalazine (17) for the respective lactam and lactim forms of 1,2-dihydro-4-(4-hydroxyphenyl)-1-oxo-(2H)-phthalazine (5) were synthesized. They were used as guides in the structural analysis of polymer 9 resulting from the reaction of 5 with bis(4-fluorophenyl)sulfone (8) carried out in N-methyl-2-pyrrolidinone at 170°C for 6 hours utilizing K2CO3 as the basic catalyst. The interpretations were largely done by 1H and 13C NMR and, qualitatively, by FT-IR and UV spectroscopy. For the key model compounds 13 and 17 and polymer 9, all of the carbons were conclusively assigned aided by H-COSY, H-C HETCOR, HMQC, and HMBC NMR techniques. The results reveal that species 5 bonds with 8 at the 2-aza-nitrogen atom of the phthalazine moiety with its lactam tautomer as the only detectable form in polymer 9. The multiple lines shown by several carbons in the 13C-NMR spectrum of 9 and their similar geometrical shapes strongly indicate that there are perhaps four magnetically different environments of the repeat unit which are randomly arranged in the chain of polymer 9.