Synthesis and structural characterisation of luminescent di- and tri-nuclear palladium(II) acetylide complexes as building blocks for metallodendrimers

Abstract

The reaction of the starting complex trans-Pd(PEt₃)₂Cl₂ with branched alkynyl ligands, 1,3,5-triethynylbenzene (L1) and 1,3-diethynyl-5-triisopropylsilylethynylbenzene (L2), in the presence of HNEt₂ and copper(I) catalyst led to formation of the respective luminescent branched acetylide complexes, 1,3,5-[Cl(Et₃P)₂PdCC]₃C₆H₃1 and 1,3-[Cl(Et₃P)₂PdCC]₂-5-[(ⁱPr)₃SiCC]C₆H₃2, which can serve as building blocks for the construction of metallodendrimers either by a divergent or a convergent approach. Photophysical studies of these complexes showed the di- and tri-nuclear palladium complexes 1 and 2 are emissive in EtOH–MeOH (4 ∶ 1, v/v) glass at low temperature. Synthesis of the first generation metallodendrimers using 1 as a building block has also been attempted and shows promising results.