STRUCTURAL-PROPERTIES OF LANGMUIR-BLODGETT-FILMS OF A LONG-CHAIN TETRATHIAFULVALENE DERIVATIVE

An investigation into the molecular arrangements in Langmuir-Blodgett films of hexadecanoyltetrathiafulvalene is reported. Low-angle X-ray diffraction shows that, as deposited, the layers are organised in a simple head-to-head and tail-to-tail configuration (i.e. Y-type deposition). However, on doping with either iodine or bromine, the X-ray d-spacing is significantly reduced, implying that the molecules become interdigitated, tilted or both. The formation of a charge-transfer band for the iodine-doped multilayers is confirmed by IR spectroscopy. Experiments using X-ray photoelectron spectroscopy and UV-Vis absorption spectroscopy reveal that the semiconducting properties of these samples are probably the result of the formation of a mixed-valence charge-transfer complex. © 1990.