Controlling emission energy in metal–organic frameworks featuring cyclometalated iridium(III) linkers

Efficient solid-state luminescent materials are critical components in varied optoelectronic devices. Here, we report three metal–organic frameworks combining calcium(II) with heteroleptic iridium(III) metalloligands containing the same 1,2-diimine ancillary ligand but different cyclometalating ligands. The synthesised frameworks exhibit similar supramolecular structure but different emission properties depending on the cyclometalating ligand. Binding calcium(II) to the metalloligands further affects framework emission depending on the relative contribution of triplet charge transfer (3MLLCT) or ligand-centred (3LC) transitions to the emissive excited state.