Monolayer and spectroscopic studies of an amphiphilic (phenylethynyl)anthracene probe in pure and mixed films with charged and neutral lipids

The amphiphilic and morphological properties of a novel, amino-subsituted b is(phenylethynyl)anthracene derivative (APA) are investigated at the air/wa ter interface using a Langmuir film balance and fluorescence microscopy. Th e interfacial miscibility of APA and positively charged, negatively charged , and zwitterionic lipids in two-dimensional monolayer phases is characteri zed on the basis of surface pressure/area isotherms of binary monolayers re corded at different molar ratios of the lipid and dye components. "Excess" Gibbs free energies of mixing are calculated for the APA/lipid monolayers a t different surface pressures. Organized supramolecular film structures of the (phenylethynyl)anthracene amphiphile and its mixtures with octadecylami ne are deposited onto solid supports by using the Langmuir-Blodgett (LB) te chnique. Mono- and LB multilayers are characterized by means of W-visible s pectroscopy. Evidence is obtained for a J-type aggregation of APA in LB mon olayers. The aggregation is likely favored by stereochemical packing factor s and pi-pi and dipole-dipole intermolecular interactions of the extended, conjugated pi-electron systems of the APA chromophore moieties. The novel p robe is found to be highly fluorescent. The determined fluorescence quantum yield is 0.58. The strong fluorescence of the amphiphile and its thermal s tability at elevated temperatures are factors favoring its potential applic ation as an activator of chemiluminescence in ordered supramolecular system s.