Natural spins detected during the solid-state polymerization of 1,3-butadiynes

1 Natural Spins Detected during the Solid-State Polymerization of 1,3-Butadiynes 

II Building Blocks for High-Spin Molecules and Molecular Assemblies 

1 A to form a one-dimensional chain in which the bond-forming carbons in the adjacent molecules are situated in proximity (s = 3.4-4.0 A). The molecular axis must be slanted by y = 45° from the direction of the one-dimensional chain. 

Takeda and Wegner suggested a carbene-like structure for the active species of the topochemical reaction [38]. A strong EPR spectrum with a conspicuous fine structure is observed for the partially polymerized samples. This fine structure is due to the magnetic dipole interaction of two or more unpaired electron spins. It is strongly dependent on the direction of the external magnetic field. By the analysis of this anisotropy, various triplet carbenes and quintet dicarbenes are unambiguously identified. 

Sixl classified the different series of intermediate products into three categories and found that the diradical and dicarbene series, DR2-DRJ, DCy-DCu. are genuine intermediates from the monomer to the polymer [39]. When the monomer crystal is irradiated with a UV flash, the dimer DR2 is formed from the monomer by a photoreaction which is followed by a series of thermally activated monomer addition reactions leading via higher DRs and DCs to the polymer (Fig. 11-4). 

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