P. Siemsen et al., Pt-tetraethynylethene molecular scaffolding: Synthesis and characterization of a novel class of organometallic molecular rods, CHEM-EUR J, 7(6), 2001, pp. 1333-1341
The series of monodisperse Pt-bridged TEE oligomers 3a-f was prepared by ox
idative Glaser-Hay oligomerization of monomer 7 under endcapping conditions
. These novel molecular rods extend in length from 3.3 nm (monomeric 3a) to
12.1 nm (hexameric 3f), Their isolation was achieved by high performance g
el permeation chromatography (GPC), and their purification was best monitor
ed by analytical GPC in combination with matrix-assisted laser-desorption-i
onization mass spectrometry (MALDI-TOF MS). The mass spectra of each oligom
er 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 drop CH to the oligomerization mixture affo
rded polymer 10 with an average of approximate to 32 repeat units and a rem
arkably narrow molecular weight distribution (M-w/M-n=1.06), which is indic
ative of a living polymerization process. UV/Vis spectral data as well as m
easurements of the second hyperpolarizability gamma by third harmonic gener
ation (THG) revealed a nearly complete lack of pi -electron delocalization
along the oligomeric backbone. The Pt atoms act as true insulating centers,
and the Pt-C(sp) bonds hardly possess any pi character. The synthesis of t
he molecular rods 3a-f provides another demonstration of the power of oxida
tive acetylenic homocouplings for the preparation of unusual nanoarchitectu
re.