The synthesis, structures and photophysical properties of the charge-neutral Pt(ii) complexes (1-6) and their Pd(ii) (7) and Ni(ii) (8) congeners supported by tetradentate dianionic bis[phenolate-(N-heterocyclic carbene)] ligands are described. The X-ray crystal structures of two solvatomorphs of 2, which has p-F substituents on the tetradentate ligand, have been determined. The photophysical properties of all the complexes were examined. In THF solutions, 1-4 display deep blue phosphorescence (λmax = ∼440-460 nm, Φe = 3-18% and τ = 0.5-3.5 μs). In solutions at room temperature, 5-8 show profoundly different luminescence properties from being virtually non-emissive (Φe