CHARGE-TRANSFER COMPLEX-FORMATION IN MONOLAYERS AT THE AIR-WATER-INTERFACE

We have investigated charge-transfer (CT) interaction between an amphiphilic cyanine dye N,N'-dioctadecyl-oxacyanine perchlorate (S9) and octadecyl tetracyanoquinodimethane (C18TCNQ) in a mixed monolayer at the air-water interface. CT interaction manifests in the optical reflection spectrum of the mixed monolayer in the form of a new broad band centered at 490 nm. The CT band shows bathochromic shifts with increasing surface pressure. The stoichiometry of the complex was found to be 1:1. Upon direct excitation of the CT band at 480 nm or via excitation of S9 at 365 nm, a broad fluorescence band with a maximum of 560 nm is observed. The results are discussed in terms of the theoretical model of CT interactions developed by Mulliken.