Helical poly(phenylacetylene)s containing schiff-base and amino groups: Synthesis, secondary structures, and responsiveness to benzoic acid

Abstract

Novel acetylenic monomers containing Schiff-base and amino groups, (S)-N-(4-ethynylbenzylidene)-1-phenylethan-, and (R)-N-(4-ethynylbenzyl)-1-phenylethanamine (1e) were synthesized and polymerized with [(nbd)RhCl] 2 /Et 3 N catalyst to afford the corresponding polymers 2a-e with moderate molecular weights (M n 5 9000-60,000) in high yields (85-97%). All the polymers were soluble in common organic solvents including toluene, CHCl 3 , CH 2 Cl 2 , THF, and DMF. Large optical rotations and strong CD signals demonstrated that 2a, 2b, 2d, and 2e take helical structures with a predominantly one-handed screw sense. The effects of solvents and temperature revealed that these polymers took dynamic helical structure based on the steric effect of side groups. The CD patterns of 2d and 2e containing free amino moieties were completely inverted by the addition of benzoic acid. Upon further addition of NaOH, the CD pattern returned to the original one, indicating the reversible conformational change of these polymers according to pH.

Unexpectedly Facile Rh(I) Catalyzed Polymerization of Ethynylbenzaldehyde Type Monomers: Synthesis of Polyacetylenes Bearing Reactive and Easy Transformable Pendant Carbaldehyde Groups

“…It can be stated that p ‐toluidine completely transferred CHO groups of parent poly( I ), poly( II ), and poly( III ) under formation of soluble polymers with aromatic Schiff‐base‐type pendant groups containing either one or two CHN links per monomeric unit. It should be noted that poly(arylacetylene)s of poly( I )T and poly( III )T types possessing one CHN link per one pendant group have already been reported in the literature as the products of a direct Rh‐catalyzed polymerization of Schiff‐base‐type monomers mainly substituted N ‐(4‐ethynylbenzylidene)anilines and N ‐(4‐ethynylbenzylidene)benzylamines . The 1 H NMR signals of the modified polymers poly( I )T, poly( II )T, and poly( III )T were less sharp and resolved than the signals of parent poly( I ), most probably due to a partial cis ‐to‐ trans isomerization of polyacetylene chains that could accompany the modification .…”

“…2017, , 1600792 The very high [α] D values of poly(I)CA and poly(III)CA may indicate that both polymers adopted one-handed helical conformation upon the modification with CA. [36,39] A confirmation of this would, however, require further investigation. Non-photoluminescent insoluble poly(III) was quantitatively modified with 3-amino-9-ethylcarbazole fluorophore (FA) under formation of soluble poly(III)FA ( Figure 2) that exhibited photoluminescence (wavelength of emission maximum = 415 nm) after excitation by radiation of wavelength 289 nm.…”

“…These values were by far larger than that of ( R )‐1‐phenylpropan‐1‐amine ([α] D = +17.7°). The very high [α] D values of poly( I )CA and poly( III )CA may indicate that both polymers adopted one‐handed helical conformation upon the modification with CA . A confirmation of this would, however, require further investigation.…”

“…It should be noted that poly(arylacetylene)s of poly(I)T and poly(III)T types possessing one CHN link per one pendant group have already been reported in the literature as the products of a direct Rh-catalyzed polymerization of Schiff-base-type monomers mainly substituted N-(4-ethynylbenzylidene)anilines and N-(4-ethynylbenzylidene)benzylamines. [34][35][36] The 1 H NMR signals of the modified polymers poly(I)T, poly(II)T, and poly(III)T were less sharp and resolved than the signals of parent poly(I), most probably due to a partial cis-to-trans isomerization of polyacetylene chains that could accompany the modification. [37,38] The solubility of both parent poly(I) and modified poly(I)T enabled the comparison of this pair of polymers with respect to the molecular weight.…”

Synthetic Methodologies for Chelating Polymer Ligands: Recent Advances and Future Development

“…10 5 ) and high yields (75‐97%) . The same catalyst [(nbd)RhCl] 2 /Et 3 N is used for the polymerization of acetylene monomers containing Schiff base and the amino group, in particular, (S)‐N‐(4‐ethynylbenzylidene)‐1‐phenylethanamine, (R)‐N‐(4‐ethynylbenzylidene)‐1‐phenylethanamine, N‐(4‐ethynylbenzylidene)‐1‐phenylethanamine, (R)‐N‐(4‐ethynylbenzyl)‐1‐phenylethanamine and (R)‐N‐(4‐ethynylbenzyl)‐1‐phenylethanamine to form CPLs with a lower molecular weight (M n = 9,000‐60,000), but with the same high yield (85‐97%) . In these examples, CPLs have helical structures with predominantly one‐handed screw sense.…”