A study of zwitterionic adducts of TCNQ.

Chapter 1 gives a general introduction to the field of electroactive organic compounds. The historical development of the field is outlined and then the more specific areas are described in detail. The properties of picolinium and quinolinium TCNQ salts are introduced and the extension of this to the molecules studied in this work developed. Two current areas of interest - second harmonic generation and molecular rectification - are then reviewed and the potential applications of the materials studied in this work highlighted. Chapter 2 discusses the synthesis of the materials and contrasts the two methods used. A discussion of the reaction mechanisms is given, as well as techniques for monitoring the course of reaction. The characterisation of the materials by a range of spectroscopic techniques is described. The solvatochromic behaviour of the materials is shown to conform with theoretical predictions and the observed mass spectra are shown to have some diagnostic importance. Chapter 3 gives a general introduction to Langmuir-Blodgett (LB) films starting once again from a historical perspective. The molecular requirements of suitable materials together with pressure/area per molecule measurements and the deposition process are described. The various methods available for the characterisation of LB films are described, as well as the many potential applications proposed within the general field of molecular electronics. Chapter 4 describes the experimental methods employed when using the Joyce Loebl Langmuir Trough. The importance of parameters such as cleanliness, sample purity and instrument calibration is stressed. Chapter 5 discusses the behaviour of the materials on the subphase and their resultant fabrication as LB films. The structure of the films is shown to be dependent on the hydrophobic chain length with a definite change in film structure occurring at a 15 carbon chain. Reasons for this are proposed and calculations of chromophore/hydrocarbon chain tilt angles on the basis of the proposed structure are given. A time dependent change in film structure is also discussed, as well as suggestions for future work.