Langmuir layers and Langmuir-Blodgett films of bis-tetrathiafulvalene annelated macrocycle

The Langmuir layers of amphiphilic bis(tetrathiafulvalene) [bis(TTF)] annelated macrocycle (1) and those of the (1)[2,3,5,6-tetrafluoro-7,7,8,8- tetracyano-p-quinodimethane (F₄-TCNQ)₂ charge-transfer (CT) complex were evaluated. The neutral molecule of 1 recognized Cs⁺ ion at the air-water interface forming a domain structure. Contrastingly, (1)(F₄-TCNQ)₂ did not recognize Cs⁺ ion at the air-water interface. The Langmuir layers of 1 were deposited on a mica surface, resulting in the formation of fibrils. The highly oriented structure of the fibrils at the molecular level was confirmed by a large dicroism in the IR spectra. The (1)(F₄-TCNQ)₂ layer deposited on the mica surface consisted of nanowires oriented in specific directions. The UV-vis-NIR spectra revealed an intramolecular dimer structure of the donor 1 cation radical in the CT complex. An extended nanowire network structure was obtained when the K⁺ cation was introduced into the subphase. The stacking of intramolecular TTF dimers and intermolecular F₄-TCNQ dimers directed the formation of nanowires, which are oriented on mica by recognizing fully occupied hexagonal K⁺ sites at the surface. The nanowire orientation was readily disturbed by varying film deposition conditions such as subphase temperature, deposition speed, or surface pressure, indicating that the fluidity of Langmuir layer was important for obtaining nanowire structure.