J-Aggregates of Pseudoisocyanine with Long Alkyl Substituents in Thin Films: Synthesis, Spectral Properties, and Thermal Stability

摘要

The formation and properties of J-aggregates in thin solid films of pseudoisocyanines with long Nalkyl groups, obtained by centrifuging from solutions in organic solvents, were studied. It is shown for the first time that nonsymmetric cyanine dyes, containing a C_(2)H_(5) group at one nitrogen atom and a C_(10)H_(21), C_(15)H_(31), or C_(18)H_(37) group at another nitrogen atom, spontaneously form J-aggregates stable at room temperature and pressing a narrow absorption band with a half-width at half maximum of 200 cm~(-1). The thermal stability of J-aggregates in thin films of pseudoisocyanines with alkyl substituents decreases in the following order: C_(2)H_(5)-C_(2)H_(5)>C_(2)H_(5)-C_(6)H_(13)>C_(2)H_(5)-C_(18)H_(37)>C_(2)H_(5)-C_(10)H_(21)>C_(2)H_(5)-C_(15)H_(31). By introducing 1-octadecyl-2-methylquinolinium iodide in the film, it was found that the J-aggregates studied consist of a small number (2-4) of dye molecules.