Ferrocenyl- and octamethylferrocenyl-substituted phenylenevinylene-, thienylenevinylene-, and 1,1′-ferrocenylenevinylene spaced ethynes: Synthesis, metathesis polymerization, and polymer properties

The preparation of five different conjugatively spaced ferrocenyl- and octamethylferrocenyl-substituted terminal alkynes as well as their metathesis polymerization using the well-defined Schrock-type catalyst of general formula Mo(N-2,6-Me-2-C6H3) (CHCMe2Ph)(OCMe(CF3))(2) is described. Besides their progenitors, the novel target ethynes [2-(2-ethynylphenyl)ethenyl]-1',2,2', 3,3',4,4',5-octamethylferrocene (3), [2-[(5-ethynyl)thien-2-yl]ethenyl]ferrocene (6), [2-[(5-ethynyl) thien-2-yl]ethenyl]-1',2,2',3,3',4,4',5-octamethylferrocene (10), [2-[4-(ethynyl)phenyl]ethenyl]-1', 2,2',3,3',4,4',5-octamethylferrocene (14), and (E)-[2-(ethynylferrocenyl)ethenyl]-1',2,2',3,3',4,4',5-octamethylferrocene (17) have been prepared. All the monomers undergo beta-addition with the initiator. Based on the NMR data of the first insertion products of 3, 6, and 10, a cis configuration is assigned to the double bond in the corresponding first insertion products, while the double bonds in the corresponding polymers are virtually all trans, indicating a fast cis-trans isomerization. The extent of conjugated domains in the corresponding polymers that may be prepared in a living manner up to a degree of polymerization (DP) of 40-50 was determined by UV-Visible spectroscopy. While the use of p-substituted phenylene- and 1,3-disubstituted thiophene spacers resulted in polymers with an effective conjugation length (N-eff) <= 10, o-phenylene spacers allowed the preparation of polymers with N-eff values up to 30. Finally, differential scanning calorimetry (DSC) was utilized to identify and characterize phase transitions. These data provide further evidence for the stiff and rigid character of both the conjugated backbone and the ferrocene-substituted side-chains.