tided as ca. 99% unreacted 'H NMR (vide supra). The components of the aqueous phase were identified by 'H NMR as paraquat (S 4.35 (s, 3 H), 8.37 (d, J = 1,2 H), 8.90 (d, J = 1,2 H)) and 2-(ethylamino)-2-methylpropanol hydrochloride (spectrum identical to that described above). Integrals of the NMR signals for paraquat and the amino alcohol indicated a 2.5% conversion of DEM-3 dimer to the amino alcohol.B. Buffered Methanol Medium. The reaction was performed in pH 7, Tris-buffered methanol. This time the reaction mixture turned dark blue. Again, the residue from solvent evaporation was extracted into 1 mL of D20 and 1 mL of CDC13. The components of the organic phase were identified by 'H NMR as DEM-3 dimer and 2-(ethylamino)-2methylpropanol (6 1.06 (s, 6 H), 1.07 (t, J = 7.2, 3 H), 2.44 (q, J = 1.2, 2 H), 3.33 (s, 2 H)). The components of the aqueous phase were identified as paraquat and a small amount of 2-(ethylamino)-2-methylpropanol hydrochloride, also from the 'H NMR spectrum. Integrals of the NMR signals indicated a 41% conversion of DEM-3 dimer to amino alcohol.Attempted Reduction of Daunomycin with DEM-3 Dimer. The reaction vessel was a 9 mm X 20 cm Pyrex tube equipped with a 2.5-cm side arm. The side arm was charged with 2.65 X 10"* mol of DEM-3 dimer dissolved in methylene chloride, and the methylene chloride was evaporated with a stream of nitrogen. The main tube was charged with 2 mL of 2 X 10~3 M 1:1 Tris/Tris-HCl buffered methanol containing 2.66 X 10"6 mol of daunomycin. The methanol solution was freeze-thaw-degassed, and the tube was sealed with a torch. After mixing the reagents, the solution was heated at 36 °C for 18 h. C-18 reverse-phase HPLC analysis as described earlier35 showed no formation of 7-deoxydaunomycinone.

Stationary and time-resolved studies of 9,10,19,20-tetramethylporphycene and 9,10,19,20-tetra-n-propylporphycene in condensed phases reveal the coexistence of trans and cis tautomeric forms. Two cis configurations, cis-1 and cis-2, play a crucial role in understanding the excited-state deactivation and tautomer conversion dynamics. The trans-trans tautomerization, involving intramolecular transfer of two hydrogen atoms, is extremely rapid (k ≥ 10(13) s(-1)), both in the ground and lowest electronically excited states. The cis-1-trans conversion rate, even though the process is thermodynamically more favorable, is much slower and solvent-dependent. This is explained by the coupling of alkyl group rotation with the hydrogen motion. Excited-state deactivation is controlled by solvent viscosity: the S(1) depopulation rate decreases by more than 2 orders of magnitude when the chromophore is transferred from a low-viscosity solution to a polymer film. Such behavior confirms a model for excited state deactivation in porphycene, which postulates that a conical intersection exists along the single hydrogen transfer path leading from the trans to a high energy cis-2 tautomeric form. For this process, the tautomerization coordinate includes not only hydrogen translocation but also large-amplitude twisting of the two protonated pyrrole moieties attached to the opposite sides of the ethylene bridge.