Theoretical evidence of metal-induced structural distortions in a series of bipyrimidine-based ligands

Abstract

Herein, we report theoretical evidence of the geometric changes occurring upon complexation, for a series of octupolar bipyrimidine-based ligands incorporating the NPh₂ terminal donor group. It is shown that ligands 1 and 2 (4,4′,6,6′-tetrakis(N,N-diphenylaminostyryl)-[2,2′]bipyrimidine and 4,4′,6,6′-tetrakis((N,N-diphenyl)-9,9′-dioctyl-9H-fluorene-2-amine)-2,2′-bipyrimidine) exhibit a non-planar geometry with a torsion angle between both pyrimidine moieties of ∼25° and 50° respectively. 1a (complex of 1) becomes planar upon addition of ZnCl₂ to the bipyrimidine moiety whereas 2a remains distorted. Furthermore, an assignment of the absorption bands for all compounds is presented.