Optical properties and aggregation of novel azo-dyes bearing an end-capped oligo(ethylene glycol) side chain in solution,solid state and Langmuir-Blodgett films

摘要

Optical properties and aggregation of two novel azo-dyes N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(3,6,9-trioxadecas-l-yl)amine (RED-PEGM-3) and N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl] phenyl}-N-(3,6,9,12,15,18,21,24-octaox-apentaeicos-l-yl)amine (RED-PEGM-8) were studied by UV-vis spectroscopy in solution,solid state and Langmuir-Blodgett films.The results were compared to those obtained for their precursor l-amino-4'-nitroazobenzene (Disperse Orange 3,DO3) and 1-N-methylamino-4'-nitroazobenzene (RED-H).Increasing the polarity of methanol:water mixtures gave rise to the formation of H-aggregates for all dyes.Similar aggregates were also detected in cast films.NOESY,2D ~1H NMR experiments carried out in aqueous solutions of RED-PEGM-8 revealed the formation of atypical antiparallel H-aggregates.Only RED-PEGM-3 gave traces of J-aggregates in the solid state.RED-PEGM-3 and RED-PEGM-8 readily form J-aggregates in Y-type Langmuir-Blodgett films.