Photophysical Properties of Imine Metal Complexes
thesisposted on 29.01.2019, 16:11 by Raissa Ibraimo Patia
A range of bis-cyclometallated Ir(III) complexes [Ir(C^N)2(N^O)] containing different cyclometallated (C^N) and ancillary (N^O) ligands with endo- and exocyclic imine bonds have been synthesised. Additionally, Ir(III), Rh(III) and Ru(II) half-sandwich complexes with exocyclic imine bonds were also synthesised. All new compounds were characterised by 1H and 13C NMR spectroscopy, mass spectrometry and some compounds have been structurally characterised by X-ray crystallography. The photophysical properties of the complexes were also studied. Chapter one introduces luminescent metal complexes particularly cyclometallated complexes of Ir(III) and some of their applications. Chapter two introduces the phenomenon of Aggregation Induced Emission (AIE) and Enhanced Phosphorescence in the Solid State (EPESS). Photophysical and computational studies of cyclometallated Ir(III) complexes [Ir(C^N)2(N^O)] show EPESS and it arises due to distortion of the N^O chelate ring in the triplet excited state; not π-stacking nor restricted rotation as proposed previously. Chapter three describes isomeric complexes containing a 5-membered chelate N^O ligand with an exocyclic imine. These do not show EPESS instead they undergo trans-cis photoisomerisation of the C=N bond. The isomerisation can be reversed thermally in some cases suggesting the complexes have potential applications as photoswitches. DFT studies suggest that the trans isomer is the most stable which agrees with the experimental data. Chapter four describes the synthesises of Ir(III), Rh(III) and Ru(II) half-sandwich complexes with 5-membered chelating anionic N^O or neutral N^N ligands which have exocyclic C=N bonds. The nature of the ligand, the imine substituent and the metal centre all affect the photoisomerisation.