Quaterphenylterpyridine: Synthesis and Metal‐Ion Complexation

A quaterphenylterpyridine ligand (qptpy) with the rodlike quaterphenyl unit attached in the 4′‐position has been synthesised by a Pd‐catalysed Suzuki cross‐coupling reaction. A crystal structure determination on the complex [Zn(qptpy)Cl 2 ]·dmf (dmf = dimethylformamide) has shown the ligand to be bound in the expected N 3 ‐tridentate manner to the essentially trigonal‐bipyramidal dichloro metal ion, with the quaterphenyl substituents involving a twisted array of the separate phenyl groups and the shortest contacts between aromatic groups involving just the polar terpyridine head groups to give an infinite, offset face‐to‐face (OFF) π‐stacking array. A comparison is made with the structures of the bis(ligand) complexes of Zn(ClO 4 ) 2 and Cd(ClO 4 ) 2 with the bromobiphenylterpyridine ligand (Brbptpy) synthesised as an intermediate for the formation of qptpy. A study of the absorption and emission spectra of qptpy and a range of its metal‐ion complexes has shown that the ligand provides a ratiometric fluorescence response for both Zn II and Cd II .