Crowned polyacetylene. 2. cis form determination of poly(4′-ethynylbenzo-15-crown-5) by solid-state NMR method

The chain structure of cis-poly(4′-ethynylbenzo-15-crown-5) (PEB15C5), prepared using the rhodium complex catalyst, was studied at ?175°C using the solid-state NMR technique. The second moment of PEB15C5 was 7.0 G² for the main chain and 19.0 G² for the side chain. These values agreed well with the respective theoretical ones for the cis form in the rigid state rather than the trans one. This agreement between experiment and theory suggested that the plane of the side chain (i.e., the benzo-15-crown-5 group) is orthogonal to the main chain plane of the cis-transoidal form. It was verified that the strong dipoledipole interaction between the side chains plays an important role as a clue to theoretically determine the cis-transoidal form. NMR results in solid state confirmed theoretically that multipeaks in the ¹H and ¹³C NMR spectra in CDCl₃ solution are attributed to cis-transoidal form in the chain. © 1995 John Wiley & Sons, Inc.