Pt‐Tetraethynylethene Molecular Scaffolding: Synthesis and Characterization of a Novel Class of Organometallic Molecular Rods

Abstract The series of monodisperse Pt‐bridged TEE oligomers 3 a – f was prepared by oxidative Glaser–Hay oligomerization of monomer 7 under end‐capping conditions. These novel molecular rods extend in length from 3.3 nm (monomeric 3 a ) to 12.1 nm (hexameric 3 f ). Their isolation was achieved by high performance gel permeation chromatography (GPC), and their purification was best monitored by analytical GPC in combination with matrix‐assisted laser‐desorption‐ionization mass spectrometry (MALDI‐TOF MS). The mass spectra of each oligomer revealed the molecular ion or its sodium complex as parent ion together with a clean, highly characteristic fragmentation pattern. Delayed addition of the end‐capping reagent PhC≡CH to the oligomerization mixture afforded polymer 10 with an average of ≈32 repeat units and a remarkably narrow molecular weight distribution ( M w / M n =1.06), which is indicative of a living polymerization process. UV/Vis spectral data as well as measurements of the second hyperpolarizability γ by third harmonic generation (THG) revealed a nearly complete lack of π‐electron delocalization along the oligomeric backbone. The Pt atoms act as true insulating centers, and the Pt−C(sp) bonds hardly possess any π character. The synthesis of the molecular rods 3 a – f provides another demonstration of the power of oxidative acetylenic homocouplings for the preparation of unusual nanoarchitecture.