12 research outputs found
Synthesis and Photoresponse of Helically Folded Poly(phenyleneethynylene)s Bearing Azobenzene Moieties in the Main Chains
Novel optically active polyÂ(phenyleneethynylene)Âs
bearing azobenzene moieties in the main chains [polyÂ(<b>1</b>–<b>2m)</b>, polyÂ(<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 [polyÂ(<b>1</b>–<b>2m</b>), polyÂ(<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 polyÂ(<b>1</b>–<b>2m</b>) and polyÂ(<b>1</b>–<b>2p</b>) formed predominantly one-handed
helically folded structures in CHCl<sub>3</sub>/THF mixtures. PolyÂ(<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, polyÂ(<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 polyÂ(phenyleneethynylene-aryleneethynylene)Âs
bearing hydroxy groups with various arylene units [polyÂ(<b>1</b>–<b>2</b>), polyÂ(<b>1</b>–<b>3a)</b>, polyÂ(<b>1</b>–<b>3b</b>), polyÂ(<b>1</b>–<b>4</b>)] were synthesized by the Sonogashira–Hagihara
coupling polymerization of (<i>S</i>)-3,5-diiodo-4-hydroxy-C<sub>6</sub>H<sub>4</sub>CONHCHÂ(CH<sub>3</sub>)ÂCOOC<sub>12</sub>H<sub>25</sub> (<b>1</b>) with HCî—¼C–Ar–Cî—¼CH
[<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><sub>n</sub>) 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<sub>max</sub>) of the polymers was polyÂ(<b>1</b>–<b>3a</b>) < polyÂ(<b>1</b>–<b>2</b>) < polyÂ(<b>1</b>–<b>3b</b>) < polyÂ(<b>1</b>–<b>4</b>). PolyÂ(<b>1</b>–<b>2</b>), polyÂ(<b>1</b>–<b>3a</b>), polyÂ(<b>1</b>–<b>3b</b>), and polyÂ(<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 [polyÂ(<b>1</b>)–polyÂ(<b>5</b>)] with <i>M</i><sub>n</sub> = 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
polyÂ(<b>1</b>), polyÂ(<b>3</b>), and polyÂ(<b>5</b>) formed chiral higher-order structures in THF/H<sub>2</sub>O mixtures,
while <i>m,m</i>′-phenyleneethynylene-linked polyÂ(<b>2</b>) and polyÂ(<b>4</b>) did not. The sign of CD signal
of polyÂ(<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%
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
Polymerization of Phenylacetylenes Using Rhodium Catalysts Coordinated by Norbornadiene Linked to a Phosphino or Amino Group
The novel rhodium (Rh) catalysts [{nbd-(CH<sub>2</sub>)<sub>4</sub>-X}ÂRhR] (<b>1</b>, X = PPh<sub>2</sub>, R = Cl; <b>2</b>, X = NPh<sub>2</sub>, R = Cl; <b>3</b>, X = PPh<sub>2</sub>, 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 (Et<sub>3</sub>N). Addition of Et<sub>3</sub>N 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 Et<sub>3</sub>N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA
Synthesis of Optically Active Poly(<i>m</i>‑phenyleneethynylene–aryleneethynylene)s Bearing Hydroxy Groups and Examination of the Higher Order Structures
Novel optically active polyÂ(<i>m</i>-phenyleneethynylene–aryleneethynylene)Âs
bearing hydroxy groups with various arylene units {polyÂ[(<i>S</i>)-/(<i>R</i>)-<b>1</b>–<b>3a</b>]–polyÂ[(<i>R</i>)-<b>1</b>–<b>3e</b>] and polyÂ[(<i>S</i>)-<b>2</b>–<b>3a</b>]} were synthesized
by the Sonogashira–Hagihara coupling polymerization of 3,5-diiodo-4-hydroxy-C<sub>6</sub>H<sub>4</sub>CONHCHÂ(CH<sub>3</sub>)ÂCOXC<sub>12</sub>H<sub>25</sub> [(<i>S</i>)-/(<i>R</i>)-<b>1</b> (X = O), (<i>S</i>)-<b>2</b> (X = NH)] with HCî—¼C–Ar–Cî—¼CH
[<b>3a</b> (Ar = 1,4-C<sub>6</sub>H<sub>4</sub>), <b>3b</b> (Ar = 1,4-C<sub>6</sub>H<sub>4</sub>-1,4-C<sub>6</sub>H<sub>4</sub>−), <b>3c</b> (Ar = 1,4-C<sub>6</sub>H<sub>4</sub>-1,4-C<sub>6</sub>H<sub>4</sub>-1,4-C<sub>6</sub>H<sub>4</sub>−), <b>3d</b> (Ar = 2,5-dihexyl-1,4-C<sub>6</sub>H<sub>2</sub>), <b>3e</b> (Ar = 2,5-didodecyl-1,4-C<sub>6</sub>H<sub>2</sub>)]. 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><sub>n</sub>. Circular
dichroism (CD), UV–vis, and fluorescence spectroscopic analyses
indicated that polyÂ[(<i>S</i>)-<b>1</b>–<b>3a</b>]–polyÂ[(<i>S</i>)-<b>1</b>–<b>3c</b>] and polyÂ[(<i>S</i>)-<b>2</b>–<b>3a</b>] formed predominantly one-handed helical structures in
THF, while polyÂ[(<i>S</i>)-<b>1</b>–<b>3d</b>] and polyÂ[(<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 polyÂ[(<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-(CH<sub>2</sub>)<sub>4</sub>-X}ÂRhR] (<b>1</b>, X = PPh<sub>2</sub>, R = Cl; <b>2</b>, X = NPh<sub>2</sub>, R = Cl; <b>3</b>, X = PPh<sub>2</sub>, 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 (Et<sub>3</sub>N). Addition of Et<sub>3</sub>N 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 Et<sub>3</sub>N to afford the polymer in good yields. Catalyst <b>3</b> achieved two-stage polymerization of PA
Characterization of the Polymerization Catalyst [(2,5-norbornadiene)Rh{C(Ph)î—»CPh<sub>2</sub>}(PPh<sub>3</sub>)] and Identification of the End Structures of Poly(phenylacetylenes) Obtained by Polymerization Using This Catalyst
The structures of [(2,5-norbornadiene)ÂRhÂ{CÂ(Ph)î—»CPh<sub>2</sub>}Â(PPh<sub>3</sub>)] (<b>1</b>) and its reaction product
with
CH<sub>3</sub>CO<sub>2</sub>H were elucidated by <sup>1</sup>H, <sup>13</sup>C, and <sup>31</sup>P NMR spectroscopy, mass spectrometry,
and single-crystal X-ray analysis. The presence of two conformational
isomers of <b>1</b> was verified by NMR spectroscopy, which
was well-supported by DFT calculations. Phenylacetylene was polymerized
using <b>1</b> as a catalyst with [M]<sub>0</sub>/[Rh] = 10
and quenched with CH<sub>3</sub>CO<sub>2</sub>H and CH<sub>3</sub>CO<sub>2</sub>D. The incorporation of H and D at the polymer ends
was confirmed by MALDI-TOF mass spectrometry and <sup>1</sup>H and <sup>1</sup>H–<sup>13</sup>C HSQC NMR spectroscopy. The polymerization
degree was calculated to be 11 by <sup>1</sup>H NMR spectroscopy,
which agreed well with the theoretical value
Characterization of the Polymerization Catalyst [(2,5-norbornadiene)Rh{C(Ph)î—»CPh<sub>2</sub>}(PPh<sub>3</sub>)] and Identification of the End Structures of Poly(phenylacetylenes) Obtained by Polymerization Using This Catalyst
The structures of [(2,5-norbornadiene)ÂRhÂ{CÂ(Ph)î—»CPh<sub>2</sub>}Â(PPh<sub>3</sub>)] (<b>1</b>) and its reaction product
with
CH<sub>3</sub>CO<sub>2</sub>H were elucidated by <sup>1</sup>H, <sup>13</sup>C, and <sup>31</sup>P NMR spectroscopy, mass spectrometry,
and single-crystal X-ray analysis. The presence of two conformational
isomers of <b>1</b> was verified by NMR spectroscopy, which
was well-supported by DFT calculations. Phenylacetylene was polymerized
using <b>1</b> as a catalyst with [M]<sub>0</sub>/[Rh] = 10
and quenched with CH<sub>3</sub>CO<sub>2</sub>H and CH<sub>3</sub>CO<sub>2</sub>D. The incorporation of H and D at the polymer ends
was confirmed by MALDI-TOF mass spectrometry and <sup>1</sup>H and <sup>1</sup>H–<sup>13</sup>C HSQC NMR spectroscopy. The polymerization
degree was calculated to be 11 by <sup>1</sup>H NMR spectroscopy,
which agreed well with the theoretical value