In search of strong light-harvesting and long-lived Ru (II) and Ir(III) triplet photosensitisers

The Ph.D. thesis begins with a general introduction of triplet photosensitisers and their role in Triplet-Triplet Annihilation Upconversion (TTA-UC). It gives a short literature review of the photophysical properties of different families of triplet photosensitisers, including Ru(II), Ir(III), Pt(II) and Pd(II) transition metal complexes, and compares their TTA-UC quantum yields and singlet oxygen photosensitisation capabilities. The aims of the research are explained along with the rationale behind the proposed new material designs. The work has three parts based on systematic molecular variants. Each part details the synthetic steps taken and gives a full structural and spectroscopic characterisation of the materials generated. i) Dinclear polyimine complexes of Ru(II) and Ir(III). These triplet photosensitsers showed stronger visible and near infrared absorption, and longer excited triplet lifetime than traditional mononuclear complexes. ii) Multi-chromophoric heteroleptic Ir(III) complexes. Here the choice of novel linker position on 2-phenylpyridine improved the properties of the triplet photosensitisers. iii) Preliminary exploration of practical applications of the materials. This includes a demonstration of their use in industrially relevant photopolymerisation processes. The thesis ends by summarising the over-riding conclusions based on the structure/property relationships established, puts the findings in context and sets out possible future directions for research in this field