Luminescent Platinum(II) Complexes with a Tridentate Caffeine-Based NHC-Pincer Ligand: Synthesis, Electrochemistry and Photophysics

A strategy of “greening up” Pt(II) luminophores is presented.For this purpose, caffeine, as a renewable alkaloid and precursorfor an N-heterocyclic carbene (NHC), is incorporated into atridentate, pincer-type ligand framework. A series of lumines-cent Pt(II) complexes, containing the tridentate bis-NHC ligandand an arylacetylide ligand is reported. The complexes’ electro-chemistry and photophysics strongly depend on the electronicnature of the substituent on arylacetylide ligand. The use ofbio-derived ligands represents one important approach tomake emitters or sensitizers eco-friendlier by coming back tocheap, abundant and non-harmful staring materials for theirsynthesis.