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The photophysics and photochemistry of indoaniline dyes have been investigated. Absorption and fluorescence characteristics have been studied at room and liquid nitrogen temperatures. Extinction coefficients for the dyes at room temperature were found to be between 2 - 3 x 10<SUP>4</SUP> mol<SUP>-1</SUP> dm<SUP>3</SUP> cm<SUP>-1</SUP> increasing to 5 - 6 x 10<SUP>4</SUP> mol<SUP>-1</SUP> dm<SUP>3</SUP> cm<SUP>-1</SUP> at 77K. Fluorescence quantum yields of ~ 4 x 10<SUP>-5</SUP> have been found at room temperature, but these increase by at least a factor of one hundred at 77 K. The first excited triplet state energies have been obtained using flash photolysis energy transfer methods and values of 87 to 94 kJ mol<SUP>-1</SUP> determined. Nanosecond flash photolysis gives rate constants for singlet oxygen quenching by the dyes which are close to the diffusion controlled limit. Flash excitation of benzophenone has been used to photo-reduce the dyes. The reduced forms have extinction coefficients around half the value of the parent dye, and maxima to the red of the dyes. NMR and UV/vis spectrophotometry have been used to investigate the effect of acid on the dyes. This was found to be a simple protonation reaction for which pKa values of between 2.8 and 4.4 have been determined. Using the nuclear Overhauser Effect it has been found that all of the dyes studied exist in the anti configuration in their ground state. The rate of alkaline hydrolysis of the dyes has been investigated using UV/vis spectrophotometry and HPLC. The reaction is composed of two consecutive reactions. LC-MS has identified the products of the first reaction as replacement of amide groups by simple amines. The photodegradation after intense visible light irradiation was investigated and product patterns obtained using HPLC. Identification of some of the products has been possible using LC-MS. Under nitrogen the main product is the reduced form of the dye, whereas, under oxygen, products which involve the dealkylation of the tertiary amine group dominate.

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The luminescent DNA probe [Ru(phen)2dppz]2+, ruthenium (bis-1,10-phenanthroline di-pyrido-[3,2-a:2',3'-c]phenazine), was the first tris-bidentate ruthenium complex to be shown unequivocally to intercalate DNA, which it achieves via insertion of the extended dipyridophenazine (dppz) ligand. The complex is non-luminescent in aqueous solution but emits strongly in organic solvents, micelles and DNA, with a quantum yield that depends on polarity, H-bonding, and protic ability of the medium. Studies of complexes with methylated dppz derivatives in a range of solvents have shown that a number of solvent factors influence the luminescent switching behaviour, the most intriguing of which is the implication of hydrogen bond formation between the dppz ligand and solvent molecules.

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