Synthesis And Chiroptical Properties Of Helical Substituted Polyacetylenes Carrying Urea Groups

The design and synthesis of anion receptors with high capable of selective binding andsensing has been received considerable attentions in recent years, due to the anions exhibitimportance roles in biology, pharmacy, chemistry, catalysis, and environmental sciences.The receptors based on urea has been received more and more attention, ascribed to theintramolecular hydrogen bond formed between urea and anions. On the other hand, helicalpolymers possess significant potential applications in many fields due to their uniqueelectronic, magnitic, molecular recognition, asymmetric catalytic, and optical properties.Helical substitute polyacetylenes as a kind of important helical polymer have attracted manyinterests in recent years due to their special properties, such as conductivity, luminescence,and liquid crystal, ect. The helical polyacetylene carrying urea groups would be hopfulpolymer anion receptors due to their hard main chains can improve the anion recognitionability of urea groups. A novel mono-substituted polyacetylenes carrying urea groups wassynthesised and their secondary structure, chiroptical properties and anion recognition abilitywere also studied.A novel chiral acetylene derivative containing a urea group was synthesized andpolymerized with a Rh catalyst to give the corresponding polymer [poly（1）] with moderatenumber-average molecular weights. The poly（1） was soluble in toluene, CHCl₃, CH₂Cl₂,THF, DMF, and DMSO, but insoluble in hexane, diethyl ether, and MeOH. The specificrotation and circular dichroism （CD） spectroscopic studies revealed that poly（1） tookpredominantly one-handed helical structures in THF and CHCl3. The presence ofintramolecular hydrogen bonding was confirmed by liquid-state IR spectroscopy. Thehelicity of poly（1） could be tuned by solvents, temperatures and anions. The helicalconformation of polymers was stable against to Br-, I-and Cl-but susceptible to F-and OH-.A novel achiral acetylene derivative2synthesized and co-polymerized with1in variousmilar ratios to give the corresponding copolymers with moderate number-average molecularweights. These polymers were soluble in toluene, CHCl₃, CH₂Cl₂, THF, DMF, and DMSO,but insoluble in hexane, diethyl ether, and MeOH. The specific rotation and circular dichroism （CD） spectroscopic studies revealed that copolymers could take predominantlyone-handed helical structures in THF when the molar cotent of1was up to10%. The CDspectraum showed that the copolymerization obeyed the “Sergeants-and-Soldiers principle”.The presence of intramolecular hydrogen bonding was confirmed by liquid-state IRspectroscopy. The helicity of copolymers could be tuned by solvent, temperature and anion.The helical conformation of polymers was stable against to Br-, I-and Cl-but susceptible to F-and OH-.