Cis and trans radicals generated in helical poly(propargyl acetate)s prepared using a [Rh(norbornadiene)Cl]2 catalyst

Abstract

The poly(propargyl acetate) (A) having a helical cis-transoid structure was stereospecifically prepared using the Rh complex catalyst, [Rh(norbornadiene)Cl] 2 , in MeOH or NEt 3 solvent at room temperature in moderated yield. Electron spin resonance (ESR) analysis of the polymer revealed the formation of the cis (B) and trans (C) *Manuscript Click here to view linked References radicals which were produced through the thermal rotational scission of the helical cis C=C bonds in the main-chain during the polymerization. The spatial and geometrical structure was successfully deduced using the two analogues polymers in which either methyl or methylene group is deuterated, by the aide of computer simulation of the observed ESR spectra together with the calculation of spin density of the two radicals.

Configuration and conformation of poly(3-carbazolylacetylene) including cis and trans radicals revealed by ESR spectroscopy

“…the ESR spectrum due to the cis and trans radicals generated in the HSPAs are observed as the sum of the odd line component due to the cis radical and the even line component due to the trans radical. 35 The spectral intensity due to the cis and trans radicals observed in the solid phase was comparable to that of the solution state. This indi-cates that the resulting cis and trans radicals are extremely stable even in the solution at room temperature.…”

“…Conformational analyses of the cis and trans radicals in CCl 4 solution were performed using DFT calculation with the UB3LYP/6-31G(d) and a model compound, i.e., a 4-mer of P(iBCzA), to determine their conformations with hyperfine coupling constants. 35,36 The calculated dihedral angles of the main chain, the spin densities of each proton in the main chain, and the coupling constants of the radicals are shown in Fig. 5.…”

“…33,34 In contrast, stereoregular SPAs prepared with the Rh catalyst have a precisely regular head-to-tail structure with highly stable cis and trans radicals. 35,36 The magnetic properties of organic radical spins have recently become very important because the behavior of these spins is related to the so-called organic devices and spintronic materials, e.g. spin glass 37,38 or spin ice.…”

Full Library of (Bis–allyl)‐deuterated Arachidonic Acids: Synthesis and Analytical Verification

“…As to versatile 1,1‐D 2 ‐ propargyl alcohol, the reported methods of its synthesis are based on the reduction of acetylenecarboxylic acid esters with LiAlD 4 , with the yields varying from 35 to 86 % . We used an alternative approach, adding magnesium acetylide 10 to deuterated paraformaldehyde (CD 2 O) n to obtain alcoholate 11 (Scheme ).…”

Proposed Mechanism for the High-Yield Polymerization of Oxyethyl Propiolates with Rh Complex Catalyst Using the Density Functional Theory Method

“…Moreover, an active monodentate Rh complex catalyst can be generated in situ from a Rh bidentate catalyst when amine, alcohol, or even water is used as the cocatalyst or solvent [13,14,15,16,17,18,19,20,21,22]. The [Rh(nbd)Cl] 2 /amine binary catalyst system has been reported to be a significantly effective catalyst for the polymerization of various phenyl acetylene derivatives and propargyl esters [23,24,25,26,27,28,29,30,31,32,33,34]. Propiolic esters, however, are sluggish when used as a monomer for the Rh catalyst system, due to their strong acidity.…”