Effect of the directionality of the ester group on the formation of hairpins in polyesters containing naphthalene and a flexible spacer

✍ Scribed by Olga Martin; Ana Sanchez-Camacho; Francisco Mendicuti; Wayne L. Mattice

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 225 KB
• Volume: 35
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199705)35:7<1127::aid-polb11>3.0.co;2-b

✦ Synopsis

Steady-state fluorescence measurements and molecular dynamics simulations have been used to study the intramolecular formation of excimers in five model compounds for polyesters containing naphthalene groups separated by flexible spacers. The model compounds are derived from 2-hydroxynaphthalene and HOOC{(CH 2 ) n {COOH, n Å 2-6. The ratio of the intensity of excimer and monomer emissions, I D / I M , is nearly independent of the viscosity of the medium, h, over the range covered in dilute solution. Although I D /I M is always very small, it shows an odd-even effect for the first four members of the series, with maxima when n is odd. Molecular dynamics simulations provide an explanation for the small values of I D /I M , their weak dependence on h, and the trend of I D /I M with n. The results for the present series of model compounds are compared with previous work, which reported larger values of I D /I M , and a stronger dependence of I D /I M on h, for bichromophoric compounds derived from 2naphthoic acid and aliphatic glycols, where the direction of the ester groups is reversed. The origin of the difference in the behavior of I D / I M in the two series is identified.