EXCIMER FLUORESCENCE FROM PHENANTHRENE-9-CARBOXYLATE DERIVATIVES

Phenanthrene and most of its known derivatives do not form stable, flu orescent excimers. Moderately intense, long-lived excimer fluorescence has been observed for lactone and lactam derivatives of phenanthrene. The solvatochromic shift of this excimer fluorescence is similar to t hat previously reported for the pyrene excimer. Stabilization of the e xcimer is attributed to the increased polarizability of phenanthrene b y a coplanar carbonyl substituent. Excimer formation is not observed f or a coplanar cyano substituent or an orthogonal carbonyl substituent.