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 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 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

New Approach to the Polymerization of Disubstituted Acetylenes by Bulky Monophosphine-Ligated Palladium Catalysts

Bulky monophosphine-ligated Pd complexes served as unprecedented admirable catalysts for the polymerization of a disubstituted acetylene. The moderately high polymer yields and cis content of the formed polyacetylene contrasted with those observed for traditional Mo catalyst-based polymer. These Pd catalysts are strong tools to promote the understanding of the structure–property relationships of disubstituted acetylenes

New Approach to the Polymerization of Disubstituted Acetylenes by Bulky Monophosphine-Ligated Palladium Catalysts

Bulky monophosphine-ligated Pd complexes served as unprecedented admirable catalysts for the polymerization of a disubstituted acetylene. The moderately high polymer yields and cis content of the formed polyacetylene contrasted with those observed for traditional Mo catalyst-based polymer. These Pd catalysts are strong tools to promote the understanding of the structure–property relationships of disubstituted acetylenes

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)

Polymerization of Phenylacetylenes Using Rhodium Catalysts Coordinated by Norbornadiene Linked to a Phosphino or Amino Group

The novel rhodium (Rh) catalysts [{nbd-(CH₂)₄-X}­RhR] (<b>1</b>, X = PPh₂, R = Cl; <b>2</b>, X = NPh₂, R = Cl; <b>3</b>, X = PPh₂, R = triphenylvinyl; nbd = 2,5-norbornadiene) were synthesized, and their catalytic activities were examined for the polymerization of phenylacetylene (PA) and its derivatives. Rh-103 NMR spectroscopy together with DFT calculations (B3LYP/6-31G*-LANL2DZ) indicated that catalyst <b>1</b> exists in a mononuclear 16-electron state, while <b>2</b> exists in dinuclear states. Catalyst <b>1</b> converted PA less than 1% in the absence of triethylamine (Et₃N). Addition of Et₃N and extension of the polymerization time enhanced the monomer conversion. On the other hand, catalysts <b>2</b> and <b>3</b> quantitatively converted PA in the absence of Et₃N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA

Polymerization of Phenylacetylenes Using Rhodium Catalysts Coordinated by Norbornadiene Linked to a Phosphino or Amino Group

The novel rhodium (Rh) catalysts [{nbd-(CH₂)₄-X}­RhR] (<b>1</b>, X = PPh₂, R = Cl; <b>2</b>, X = NPh₂, R = Cl; <b>3</b>, X = PPh₂, R = triphenylvinyl; nbd = 2,5-norbornadiene) were synthesized, and their catalytic activities were examined for the polymerization of phenylacetylene (PA) and its derivatives. Rh-103 NMR spectroscopy together with DFT calculations (B3LYP/6-31G*-LANL2DZ) indicated that catalyst <b>1</b> exists in a mononuclear 16-electron state, while <b>2</b> exists in dinuclear states. Catalyst <b>1</b> converted PA less than 1% in the absence of triethylamine (Et₃N). Addition of Et₃N and extension of the polymerization time enhanced the monomer conversion. On the other hand, catalysts <b>2</b> and <b>3</b> quantitatively converted PA in the absence of Et₃N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA

Ligand Exchange Reaction for Controlling the Conformation of Platinum-Containing Polymers

Control of the conformation of polymers can be achieved by the <i>ligand exchange reaction</i> of optically active poly­(phenylene­ethynylene) <b>1′</b> containing −Pt­(PPh₃)₂– moieties in the main chain. Polymer <b>1′</b> was reacted with 1,2-bis­(diphenyl­phosphino)­ethane (dppe), 1,3-bis­(diphenyl­phosphino)­propane (dppp), and 1,4-bis­(diphenyl­phosphino)­butane (dppb) to give the corresponding polymers <b>2′</b>, <b>3′</b>, and <b>4′</b> containing −Pt­(dppe)–, −Pt­(dppp)– , and −Pt­(dppb)– moieties in the main chain, respectively. Polymers <b>1′</b> and <b>2′</b> exhibited negligibly small circular dichroism (CD) signals in THF, indicating the absence of regulated chiral structures, while polymers <b>3′</b> and <b>4′</b> exhibited strong CD signals in THF. The dynamic light scattering (DLS) analysis of the polymer solutions indicated that polymer <b>3′</b> formed a chirally regulated one-handed helix intramolecularly bridged with dppp, and polymer <b>4′</b> formed aggregates intramolecularly and/or intermolecularly bridged with dppb

Sonogashira–Hagihara and Mizoroki–Heck Coupling Polymerizations Catalyzed by Pd Nanoclusters

Sonogashira–Hagihara and Mizoroki–Heck Coupling Polymerizations Catalyzed by Pd Nanocluster