Photoluminescence of Ni(II), Pd(II), and Pt(II) Complexes [M(Me(2)dpb)Cl] Obtained from C-H Activation of 1,5-Di(2-pyridyl)-2,4-dimethylbenzene (Me(2)dpbH)

The three complexes [M(Me(2)dpb)Cl] (M = Ni, Pd, Pt) containing the tridentate N,C,N-cyclometalating 3,5-dimethyl-1,5-dipyridyl-phenide ligand (Me(2)dpb(-)) were synthesised using a base-assisted C-H activation method. Oxidation potentials from cyclic voltammetry increased along the series Pt = 3.18 eV), promoting rapid radiationless relaxation. For the Pd(II) and Pt(II) derivatives, the dark states are markedly higher in energy with >= 4.41 eV (Pd) and >= 4.86 eV (Pt), which is in perfect agreement with the similar photophysical behaviour of the two complexes at low temperatures