Highly controlled side-chain chromophore orientation in poly[N5-1-(1-pyrenyl)ethyl-l-glutamines].

Poly[ N 5 -( R and S )-1-(1-pyrenyl)ethyl- l -glutamines] ( 1 and 2 ) were prepared by condensation of poly( l -glutamic acid) with optically resolved amines. In solution, these polymers, 2 in particular, gave large circular dichroism (CD) indicative of exciton coupling among the side-chain pyrene chromophores. When compared with the corresponding polymer with achiral side groups, i.e. poly(1-pyrenylmethyl- l -glutamine) ( 3 ), 1 and 2 not only gave much stronger CD, but also gave much reduced excimer emission with a significant hypsochromic shift of emission maximum. The highly controlled orientation of the side-chain chromophores is apparently brought about by the specific steric interactions among the bulky chiral side chains along the helical main chain. [ABSTRACT FROM AUTHOR]