Synthesis and characterisation of some solvatochromic betaine systems.

This thesis is concerned with the synthesis and characterisation of five new types of solvatochromic systems and preliminary investigations into the synthesis of some new systems involving several such chromophoric units. Confirmation of the structure of these systems was carried out by NMR ([31]P and [1]H), and mass spectral analysis, together with the results of microanalysis. The solvatochromic behaviour was investigated in detail, by dissolution in a range of solvents and measurement of their longest-wavelength absorption bands using UV/Visible spectroscopy.A range of long chain phosphoniophenyl-imidazolide betaine systems and long chain 4-N-(o-phosphoniobenzylidene) iminophenolate betaines has been prepared and their properties compared to the respective triphenylphosphonio analogues already reported in the literature. The formation of Langmuir Blodgett (LB) films by three of the amphiphilic betaines has been studied in collaboration with the University of Cranfield.The effects of annelation of a benzene ring in the triphenylphosphoniophenyl-imidazolide and -benzylidene iminophenolate systems has been investigated and the effects on the solvatochromism of the resulting compounds has been explored. As part of this study two N-hexadecylquinolinium iminophenolate betaines have been prepared and their solvatochromism compared to that of the pyridinium counterparts. LB film formation of one of the quinolinium betaines has been studied, and nonlinear optical properties observed, together with other properties that may form the basis of sensor techniques.The first solvatochromic arsonium and stibonium iminophenolate betaines have been prepared by a new synthetic procedure, and compared to their phosphonium counterparts.All of the betaines studied display negative solvatochromism as the solvent polarity increases and their absorption maxima are linearly related with the standard E NT values for the Reichardt betaine dye, which suggests a possible application of these betaines as indicators of solvent polarity.A new family of triphenylphosphonium salts employing different donor groups has been synthesised and converted into related phosphine oxides. The compounds were found not to be greatly solvatochromic.Attempts to synthesise a range of "3-D" multi-chromophoric iminophenolate betaines have been carried out. However, at the present time the level of chromophore substitution is unknown, and the insolubility of the precursor salts has made isolation of the betaines very difficult. In situ formation of the betaines in the UV cell in a few solvents has shown the systems to be solvatochromic. A quinolinium iminophenolate betaine has been covalently attached to a soluble polystyrene support. An LB film of the polymer bound betaine was formed at Cranfield University; however subsequent Surface Plasmon Resonance (SPR) studies were unsuccessful.