Molecular complexes.

This thesis is concerned with the study of both ground and excited state complexes. The introductory chapter gives a brief historical account of the theoretical nature of charge transfer complexes that led up to the definitive theory due to Mulliken which is also described. In Chapter 2, ground state complexes of the type I2X- (where X- is a halide or chalcogenide ion) are studied by ultra-violet, infra-red and Raman spectroscopy. The nature of contact complexes is discussed in Chapter 3 and a report is presented on the contact complexes of oxygen with two organic solvents, benzene and N.N dimethylaniline. A simple treatment of the amount of contact complexing occurring with changing viscosity of the solvent is given and, also noted, is the effect of solvent viscosity change on a conventional charge transfer complex. The remaining Chapters, 4,5 and 6 are concerned with excited state complexes. The system used throughout is the complexing of excited state anthracene as the acceptor with various ground state inorganic anions as donors. A general introduction for the three chapters, comprising a theoretical treatment of excited state complex (exciplex) formation and various practical details, precedes Chapter 4. Correlation of the quenching constants of various inorganic anions with the energy of their charge transfer to solvent absorption band is examined in Chapter 4, the data are suggested to support an electron transfer mechanism for the exciplex formation. Chapter 5 is concerned with the effects of solvent changes on the quenching constants of iodide and bromide. The correlation of these quenching constants with the solvent parameter, ET, again gives support for an electron transfer mechanism in the formation of the exciplex. In Chapter 6 aqueous binary solvent mixtures are considered. Here, the various quenching constants of iodide and bromide are noted in several alcohol/water and pyridine/water mixtures. Effects of temperature variation are measured and conclusions drawn concerning the structure of the solvent mixtures, together with the possible observation of a 'Lumry Temperature' effect. In conclusion the appendices contain a report of the attempted observation of complex fluorescence of an exciplex.