Synthesis and Photoresponse of Helically Folded Poly(phenyleneethynylene)s Bearing Azobenzene Moieties in the Main Chains

Novel optically active poly­(phenyleneethynylene)­s bearing azobenzene moieties in the main chains [poly­(<b>1</b>–<b>2m)</b>, poly­(<b>1</b>–<b>2p</b>)] were synthesized by the Sonogashira–Hagihara coupling polymerization of 3′,5′-diiodo-4′-hydroxy-<i>N</i>-α-<i>tert</i>-butoxycarbonyl-d-phenylglycine hexylamide (<b>1</b>) with 3,3′-diethynylazobenzene (<b>2m</b>) and 4,4′-diethynylazobenzene (<b>2p</b>). The corresponding polymers [poly­(<b>1</b>–<b>2m</b>), poly­(<b>1</b>–<b>2p</b>)], with number-average molecular weights of 10700 and 9400, were obtained in 70% and 86% yields, respectively. CD and UV–vis spectroscopic analyses revealed that poly­(<b>1</b>–<b>2m</b>) and poly­(<b>1</b>–<b>2p</b>) formed predominantly one-handed helically folded structures in CHCl₃/THF mixtures. Poly­(<b>1</b>–<b>2m</b>) underwent a reversible conformational change between folded and unfolded structures upon UV and visible irradiation, as a result of <i>trans</i>–<i>cis</i> isomerization of the azobenzene moieties. On the other hand, poly­(<b>1</b>–<b>2p</b>) showed very little conformational transformation or azobenzene isomerization. The formation of helical structures was supported by conformational analysis based on the molecular mechanics (MM), semiempirical molecular orbital (MO), and density functional theory (DFT) methods

Synthesis of Novel Optically Active Poly(phenyleneethynylene–aryleneethynylene)s Bearing Hydroxy Groups. Examination of the Chiroptical Properties and Conjugation Length

Novel optically active poly­(phenyleneethynylene-aryleneethynylene)­s bearing hydroxy groups with various arylene units [poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a)</b>, poly­(<b>1</b>–<b>3b</b>), poly­(<b>1</b>–<b>4</b>)] were synthesized by the Sonogashira–Hagihara coupling polymerization of (<i>S</i>)-3,5-diiodo-4-hydroxy-C₆H₄CONHCH­(CH₃)­COOC₁₂H₂₅ (<b>1</b>) with HCC–Ar–CCH [<b>2</b> (Ar = 1,4-phenylene), <b>3a</b> (Ar = 2,7-naphthylene), <b>3b</b> (Ar = 1,4-naphthylene) and <b>4</b> (Ar = 1,6-pyrenylene), and the optical properties were compared. Polymers with number-average molecular weights (<i>M</i>_n) of 5,300–11,300 were obtained in 88–94% yields. CD and UV–vis spectroscopic analysis revealed that all the polymers formed predominantly one-handed helical structures in THF. The order of absorption maxima (λ_max) of the polymers was poly­(<b>1</b>–<b>3a</b>) < poly­(<b>1</b>–<b>2</b>) < poly­(<b>1</b>–<b>3b</b>) < poly­(<b>1</b>–<b>4</b>). Poly­(<b>1</b>–<b>2</b>), poly­(<b>1</b>–<b>3a</b>), poly­(<b>1</b>–<b>3b</b>), and poly­(<b>1</b>–<b>4</b>) emitted blue, purplish blue, green and yellow fluorescence, respectively

Synthesis of Optically Active Conjugated Polymers Bearing <i>m</i>‑Terphenylene Moieties by Acetylenic Coupling Polymerization: Chiral Aggregation and Optical Properties of the Product Polymers

The acetylenic coupling polymerization of d-hydroxyphenylglycine-derived <i>m</i>-terphenylene diynes <b>1</b>–<b>5</b> using Pd/Cu catalyst gave the corresponding polymers [poly­(<b>1</b>)–poly­(<b>5</b>)] with <i>M</i>_n = 12 000–60 000 in 53–89% yields. The polymers were soluble in THF and DMF. CD and UV–vis spectroscopic analysis revealed that <i>p,p</i>′-phenyleneethynylene-linked poly­(<b>1</b>), poly­(<b>3</b>), and poly­(<b>5</b>) formed chiral higher-order structures in THF/H₂O mixtures, while <i>m,m</i>′-phenyleneethynylene-linked poly­(<b>2</b>) and poly­(<b>4</b>) did not. The sign of CD signal of poly­(<b>1</b>) was reasonably predicted by time-dependent density functional calculations of the model system. The polymers emitted fluorescence with quantum yields ranging from 0.2–14.8%

Synthesis of Optically Active Poly(<i>m</i>‑phenyleneethynylene–aryleneethynylene)s Bearing Hydroxy Groups and Examination of the Higher Order Structures

Novel optically active poly­(<i>m</i>-phenyleneethynylene–aryleneethynylene)­s bearing hydroxy groups with various arylene units {poly­[(<i>S</i>)-/(<i>R</i>)-<b>1</b>–<b>3a</b>]–poly­[(<i>R</i>)-<b>1</b>–<b>3e</b>] and poly­[(<i>S</i>)-<b>2</b>–<b>3a</b>]} were synthesized by the Sonogashira–Hagihara coupling polymerization of 3,5-diiodo-4-hydroxy-C₆H₄CONHCH­(CH₃)­COXC₁₂H₂₅ [(<i>S</i>)-/(<i>R</i>)-<b>1</b> (X = O), (<i>S</i>)-<b>2</b> (X = NH)] with HCC–Ar–CCH [<b>3a</b> (Ar = 1,4-C₆H₄), <b>3b</b> (Ar = 1,4-C₆H₄-1,4-C₆H₄−), <b>3c</b> (Ar = 1,4-C₆H₄-1,4-C₆H₄-1,4-C₆H₄−), <b>3d</b> (Ar = 2,5-dihexyl-1,4-C₆H₂), <b>3e</b> (Ar = 2,5-didodecyl-1,4-C₆H₂)]. The yields and number-average molecular weights of the polymers were in the ranges 60–94% and 7,000–29,500 with no correlation between the yield and the <i>M</i>_n. Circular dichroism (CD), UV–vis, and fluorescence spectroscopic analyses indicated that poly­[(<i>S</i>)-<b>1</b>–<b>3a</b>]–poly­[(<i>S</i>)-<b>1</b>–<b>3c</b>] and poly­[(<i>S</i>)-<b>2</b>–<b>3a</b>] formed predominantly one-handed helical structures in THF, while poly­[(<i>S</i>)-<b>1</b>–<b>3d</b>] and poly­[(<i>S</i>)-<b>1</b>–<b>3e</b>] showed no evidence for forming chirally ordered structures. All polymers emitted blue fluorescence. The solution state IR measurement revealed the presence of intramolecular hydrogen bonding between the amide groups at the side chains of poly­[(<i>S</i>)-<b>1</b>–<b>2a</b>]. The helical structures and helix-forming abilities of the polymers were analyzed by the molecular mechanics (MM), semiempirical molecular orbital (MO) and density functional theory (DFT) methods. Tube-like structures, presumably formed by perpendicular aggregation of the helical polymers, were observed by atomic force microscopy (AFM)

Synthesis and Cavity Size Effect of Pd-Containing Macrocycle Catalyst for Efficient Intramolecular Hydroamination of Allylurethane

Palladium-containing macrocycle catalysts (<b>PdMCs</b>) with different ring sizes ranging from 24 to 30 members were synthesized. The intramolecular hydroamination of an allylurethane (<b>AU</b>) catalyzed by <b>PdMCs</b> proceeded efficiently to afford the corresponding oxazolidinone (<b>OZ</b>) in 95% isolated yield. The dependence of the hydroamination of <b>AU</b> to <b>OZ</b> on the cavity size indicated that the reaction rate was clearly controlled by both substrate uptake and product release steps

Reversible Transformation of a One-Handed Helical Foldamer Utilizing a Planarity-Switchable Spacer and <i>C</i>₂‑Chiral Spirobifluorene Units

Polymeric quaterthiophenes containing optically active <i>C</i>₂-chiral spirobifluorene skeletons were synthesized as a new type of helical foldamers, and their higher-order structures were investigated. Oxidization of quaterthiophene moieties caused the spacer units to be in planar structure, leading the conformation of the polymer to be a coil-shaped, rigid helix. This transformation was reversibly performed