Polymetallic triplet emitters

Culham, Stacey (2013) Polymetallic triplet emitters. Doctoral thesis, Northumbria University.

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Abstract

This work is concerned with the synthesis and property investigation of a relatively new class of cyclometallated Ir(III) and Pt(II) complexes in which two metal centres are coordinated to a common heterocycle resulting in a rigid polymetallic assembly. Highly luminescent materials which can emit and absorb in a red region of the spectrum were targeted.

There are three main parts of the thesis. The first part investigates how luminescent properties of the diplatinum systems are affected by the bridging ligand. A series of novel mono- and dinuclear Pt(II) complexes has been prepared and their luminescent and redox properties investigated. The main observation is that the introduction of the second metal centre leads to a substantial red-shift in absorption and emission.

In the second part the role of changing the ligand substituents in a cyclometallated complex has been investigated to determine the extent to which luminescence is affected by the nature of the substituents. A series of mono- and dinuclear Pt(II) complexes have been prepared using substituted pyrazine bridging ligands. It was found that electron donating substituents such as –OMe in the benzene cyclometallating ring cause a red-shift, while electron withdrawing substituents such as –F cause a blue-shift in emission.

The final part of the work describes the synthesis of cyclometallated homometallic bis Ir(III) complexes. A series of bis- Ir(III) complexes have been prepared using a terdentate cyclometallating N^C^N coordinating 1,3-di(2-pyridyl)benzene derivative as an auxiliary ligand. It was found that the nature of the bridging ligand determines the overall stability of the complex. Pyrimidine-linked systems were found to be the most stable, while pyrazine analogues readily photodecompose/isomerise. Pyridazine-linked systems lead to ionic complexes where one chloride ligand is shared by two Iridium metal centres.

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