Cyclometalated cinchophen ligands on iridium(iii): towards water-soluble complexes with visible luminescence?

Dalton Transactions Pub Date: 2013-06-06 DOI: 10.1039/C3DT51098K

Abstract

Eight cationic heteroleptic iridium(III) complexes, [Ir(epqc)2(N^N)]+, were prepared in high yield from a cyclometalated iridium bridged-chloride dimer bearing two ethyl-2-phenylquinoline-4-carboxylate (epqc) ligands. Two X-ray crystallographic studies were undertaken on selected complexes (where the ancillary ligand N^N = 4,4′-dimethyl-2,2′-bipyridine and 4,7-diphenyl-1,10-phenanthroline) each confirming the proposed formulations, showing an octahedral coordination at Ir(III). In general, the complexes are luminescent (620–630 nm) with moderately long lifetimes indicative of phosphorescence. Hydrolysis of the ethyl ester moieties of the epqc ligands gave the analogous cinchophen-based complexes, which were water-soluble and visibly luminescent (568–631 nm). The spectroscopic and redox characterisation of the complexes was complemented by DFT and TD-DFT calculations, supporting the assignment of dominant 3MLCT to the emissive character.

Graphical abstract: Cyclometalated cinchophen ligands on iridium(iii): towards water-soluble complexes with visible luminescence
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