Oligo(1,5-dialkoxynaphthalene-2,6-diyl)s were synthesized by Ni(cod)₂ (cod = 1,5-cyclooctadiene)-promoted condensation reactions of 1,5-dialkoxy-2,6-dibromonaphthalenes. The UV–Vis, photoluminescence (PL), and powder X-ray diffraction (XRD) measurements suggested that the oligomers have a self-assembling ordered structure in the solid state. The oligomers underwent electrochemical oxidation (p-doping), which occurred at lower potentials for films than for acetonitrile solutions containing [Et₄N]BF₄. This effect is caused by the longer π-conjugation lengths of the oligomers in films, which was attributed to molecular self-assembly leading to ordered structures in the solid state. The electrochemical reaction of the oligomers was accompanied by electrochromism. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41840.

A soluble n-type π-conjugated polymer (polymer 1) composed of a 1,2,4-triazole ring substituted by a 4-n-octylphenyl subunit at the 4-position of the 1,2,4-triazole ring and pyridine-2,5-diyl rings was synthesized by Ni(cod)₂ (cod = 1,5-cyclooctadiene) promoted dehalogenation polycondensation of 3,5-bis(2-bromopyridyl)-4-n-octylphenyl-1,2,4-triazole (monomer 1). A polymer complex (polymer-BiCl₃) was synthesized by the reaction of polymer 1 with BiCl₃. The UV–vis spectrum of polymer 1 exhibited an absorption maximum (λ_max value) at a longer wavelength than that exhibited by monomer 1 revealing that its π-conjugation system was expanded along the polymer chain. Polymer 1 was electrochemically active in film, and the electrochemical reaction was accompanied with electrochromism. Thermoelectoric properties of polymer 1 and polymer-BiCl₃ were investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39928.

Investigation of the solvatochromic behavior in branched oligophenylenes (OPs) will lead to a better understanding of intramolecular charge transfer behavior in the aromatic compounds and toward the development of new functional materials. However, there is no report on solvatochromism of branched OP. In this study, branched OPs with phenolic hydroxy groups were synthesized by using reactions with transition metal complexes. The treatment of these compounds with a base produced corresponding deprotonated species, whose absorption and photoluminescence peak positions in solution shifted towards longer wavelengths with an increase in the donor numbers of the solvents. These results will be useful in providing information for the development of new solvatochromic and energy trapping materials based on branched aromatic compounds. Copyright © 2014 John Wiley & Sons, Ltd.

Polythiophenes with reactive Zincke salt structure, P4ThPy⁺DNP(Cl⁻)-a and P5ThPy⁺DNP(Cl⁻)-a, were synthesized by the oxidation polymerization of oligothiophenes, such as 3'-(4-N-(2,4-dinitrophenyl)pyridinium chloride)−2,2':5',2'';5'',2'''-quarterthiophene (4ThPy⁺DNP(Cl⁻)) and 4''-(4-N-(2,4-dinitrophenyl)pyridinium chloride)−2,2';5',2'';5'',2''';5''',2''''-quinquethiophene (5ThPy⁺DNP(Cl⁻)), with iron(III) chloride. The reaction of P5ThPy⁺DNP(Cl⁻)-a with R-NH₂ [R = n-hexyl (Hex) and phenyl (Ph)] substituted the 2,4-dinitrophenyl group into the R group with the elimination of 2,4-dinitroaniline to yield P5ThPy⁺R(Cl⁻). Similarly, model compounds, 4ThPy⁺R(Cl⁻) and 5ThPy⁺R(Cl⁻) (R = Hex and Ph), were also synthesized. In contrast to the photoluminescent 4ThPy and 5ThPy, the compounds P4ThPy⁺DNP(Cl⁻)-a, P5ThPy⁺DNP(Cl⁻)-a, and P5ThPy⁺R(Cl⁻) showed no photoluminescence because their internal pyridinium rings acted as quenchers. Cyclic voltammetry measurements suggested that P4ThPy⁺DNP(Cl⁻)-a, P5ThPy⁺DNP(Cl⁻)-a, and P5ThPy⁺R(Cl⁻) received an electrochemical reduction of the pyridinium and 2,4-dinitrophenyl groups and oxidation of the polymer backbone. P4ThPy⁺DNP(Cl⁻)-a and P5ThPy⁺DNP(Cl⁻)-a were electrically conductive (ρ = 3.0 × 10⁻⁶ S cm⁻¹ and 2.1 × 10⁻⁶ S cm⁻¹, respectively) in the nondoped state. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 481–492

n-Type π-conjugated polymers comprising a 1,2,4-triazole ring substituted by a benzo-15-crown 5-ether (benzo15C5) subunit at the 4-position of the 1,2,4-triazole ring and n-type aromatic rings such as pyridine-2,5-diyl and 2,1,3-benzothiadiazole-4,7-diyl rings were synthesized by organometallic polycondensation. The UV-visible spectra of the polymers exhibited absorption maxima (λ_max values) at a longer wavelength than that exhibited by 3,5-bis(2-bromopyridyl)-4-benzo15C5-1,2,4-triazole, revealing that their π-conjugation system was expanded along the polymer chain. The polymers with the benzo15C5 subunit underwent an electrochemical reduction (n-doping), and the corresponding oxidation (n-dedoping) occurred at an unusually high potential in an acetonitrile solution of NaClO₄; the factor responsible for the unusually high oxidation potential was the stabilized n-doping state that was attributed to the inclusion of Na⁺ in the 15C5 ring. The polymers with the benzo15C5 subunit exhibited a considerably higher stability of the n-doping state in air than did those without this subunit. Copyright © 2012 Society of Chemical Industry

Polyphenylene (PP) with NH₂ side groups, namely, PFluNH₂, was synthesized by the Pd-catalyzed reaction of 2,5-dibromoaniline with 9,9-dihexylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester. The reaction of PFluNH₂ with 1-hexyl-1′-(2,4-dinitrophenyl)-4,4′-bipyridinium diiodide (SaltBPy(I⁻)) eliminated 2,4-dinitroaniline to yield PPs with viologen (1,1′-disubstituted 4,4′-bipyridinium dications), PFluBPy(I⁻). The reaction of PFluBPy(I⁻) with Li⁺TCNQ⁻ resulted in anion exchange between Cl⁻ and TCNQ⁻, and yielded PFluBPy(TCNQ⁻). The reaction of PFluBPy(TCNQ⁻) with the neutral TCNQ⁰ resulted in an interaction between TCNQ⁻ and TCNQ⁰, and yielded PFluBPy(TCNQ⁻-TCNQ⁰). Cyclic voltammetry measurements suggested that an electrochemical reduction of the viologen moiety and oxidation of the polymer backbone within PFluBPy(TCNQ⁻) and PFluBPy(TCNQ⁻-TCNQ⁰). Furthermore, this reaction was accompanied by electrochromism. The electric conductivities (σ) of the pellets molded from PFluBPy(TCNQ⁻) to PFluBPy(TCNQ⁻-TCNQ⁰) were 2.7 × 10⁻⁴ and 4.2 × 10⁻⁴ Scm⁻¹, respectively; these σ values were higher than that observed for PFluNH₂ (σ < 10⁻⁸ Scm⁻¹) due to the self-doping in the polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The reaction of N-(2,4-dinitrophenyl)pyridinium chloride (1), diaza-18-crown 6-ether (DA18C6) and 2,5-bis(aminophenyl)-1,3,4-oxadiazole (2) caused the opening of the pyridinium ring and yielded an ionic oligomer (oligomer-1) comprising a 5-DA18C6-penta-2,4-dienylideneammonium chloride main chain and 2-(4-aminophenyl)-5-phenyl-1,3,4-oxadiazole or 2-(4-N-phenylpyridinium)-5-phenyl-1,3,4-oxadiazole end groups. Accordingly, the reaction of 1, DA18C6 and 2,7-diaminofluorene (3) yielded oligomer-2. The structures of oligomer-1 and oligomer-2 were determined by comparing their ¹H NMR spectra with those of model compounds, which were synthesized by the 1:1 reaction of 1 with 2 or 3. Oligomer-1 and oligomer-2 exhibited weak bluish-green photoluminescence (PL) before the inclusion of Ag⁺ in the DA18C6 receptor, after which they exhibited strong bluish-green PL. These observations can be explained by the occurrence of photoinduced electron transfer in the oligomers. Copyright © 2011 Society of Chemical Industry

Polythiophenes with reactive Zincke salt structure, such as PThThPy⁺DNP(Cl⁻)Th, were synthesized by the oxidation polymerization of 3′-(4-N-(2,4-dinitrophenyl)pyridinium chloride)-2,2′:5′,2″-terthiophene (ThThPy⁺DNP(Cl⁻)Th) with iron(III) chloride or copper(II) trifluoromethanesulfonate. The reaction of PThThPy⁺DNP(Cl⁻)Th with R-NH₂ (R = n-hexyl (Hex) and phenyl (Ph)) substituted the 2,4-dinitrophenyl group into the R group with the elimination of 2,4-dinitroaniline to yield PThThPy⁺R(Cl⁻)Th. Similarly, model compounds, ThThPy⁺R(Cl⁻)Th (R = Hex and Ph), were also synthesized. In contrast to the photoluminescent ThThPyTh and PThThPyTh, the compounds PThThPy⁺DNP(Cl⁻)Th, PThThPy⁺R(Cl⁻)Th, and ThThPy⁺R(Cl⁻)Th showed no photoluminescence because their internal pyridinium rings acted as quenchers. Cyclic voltammetry measurements suggested that PThThPy⁺DNP(Cl⁻)Th received an electrochemical reduction of the pyridinium and 2,4-dinitrophenyl groups and oxidation of the polymer backbone. PThThPy⁺DNP(Cl⁻)Th was electrically conductive (ρ = 2.0 × 10⁻⁶ S cm⁻¹) in the non-doped state. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Reactions of N-(2,4-dinitrophenyl)-4-arylpyridinium chlorides (aryl (Ar) = phenyl and 4-biphenyl) with piperazine or homopiperazine caused opening of the pyridinium ring and yielded polymers that consisted of 5-piperazinium-3-arylpenta-2,4-dienylideneammonium chloride (N(CH₂CH₂)₂N⁺ (Cl⁻)CHCHC(Ar)CHCH) or 5-homopiperazinium-3-arylpenta-2,4-dienylideneammonium chloride (N(CH₂CH₂CH₂)(CH₂CH₂)N⁺ (Cl⁻)CHCHC(Ar)CHCH) units. ¹H NMR spectral analysis suggested that the π-electrons of the penta-2,4-dienylideneammonium group of the polymers were delocalized. UV-visible spectral measurements revealed that the π-conjugation system expanded along the polymer chains because of the orbital interaction between electrons of the two nitrogen atoms of the piperazinium and homopiperazinium rings. However, the π-conjugation length depended on the distance between the two nitrogen atoms; that is, the polymers containing the piperazinium ring had a longer π-conjugation length than those containing the homopiperazinium ring. Conversion of the piperazinium and homopiperazinium rings from the boat to the chair form led to a decrease in the π-conjugation length. The surface of pellets that were molded from the polymers exhibited metallic luster, and these polymers underwent electrochemical oxidation in solution. Copyright © 2010 Society of Chemical Industry

Diacetylenes (DAs) having a dipolar D-π-A structure (D=donor: amino group; π=π-conjugation core; A=acceptor: pyridinium (Py) and bipyridinium (BPy) groups), i.e., 4 (APBPyDA) and 5 (APPyPyDA), or an A-π-A structure, i.e., 7 (DBPyDA) and 8 (PyDA(Cl)), were obtained by 1 : 1 and 1 : 2 reactions of 4,4′-(buta-1,3-diyne-1,4-diyl)bis[benzenamine] (APDA; 3) with 1-(2,4-dinitrophenyl)-1′-hexyl-4,4′-bipyridinium bromide chloride (1 : 1 : 1) (1), 1-(2,4-dinitrophenyl)-4-(pyridin-4-yl)pyridinium chloride (2), or 1-(2,4-dinitrophenyl)pyridinium chloride (6) (Schemes 1 and 2). The anion-exchange reactions of 8 with NaI and Li(TCNQ) (TCNQ⁻=2,2′-(cyclohexa-2,5-diene-1,4-diylidene)bis[propanedinitrile] radical ion (1−)) yielded the corresponding I⁻ and TCNQ⁻ salts 9 (PyDA(I)) and 10 (PyDA(TCNQ)). Compounds 10 and 4 exhibited a UV/VIS absorption due to a charge transfer between the TCNQ⁻ and the pyridinium groups and a strong solute–solvent interaction of a dipolar solute molecule in the polar environment, respectively. Compounds 8–10 exhibited photoluminescence in solution, whereas 4 and 7 did not because of the presence of the 4,4′-bipyridinium quenching groups. Differential-scanning-calorimetry (DSC) measurements suggested that the DAs obtained in this study can be converted into poly(diacetylenes) by thermal polymerization.

BACKGROUND: Rigid-rod oligomers and polymers comprising a recurring benzodiazaborole unit show high thermal stability and intriguing optical and electrochemical properties due to the expanded electron system through the BC and BN bonds in the main chain by the use of the p_z orbital on boron. However, the conventional method for the preparation of these oligomers and polymers often requires polycondensation under severe conditions. In this study, we report the synthesis of oligomers comprising a recurring benzodiazaborole unit using the Stille reaction under mild conditions. In addition, we describe their chemical properties and solid-state structures.

RESULTS: The reaction of 3,3′-diaminobenzidine with 4-bromophenylboronic acid and benzeneboronic acid yielded 2,2′-bis(4-bromophenyl)-2,3,2′,3′-tetrahydro-1H,1′H-[5,5′]bi(benzo[1,3,2]diazaborolyl) (1) and 2,2′-biphenyl-2,3,2′,3′-tetrahydro-1H,1′H-[5,5′]bi(benzo[1,3,2]diazaborolyl), respectively. Pd-complex-catalyzed polycondensation of 1 with bis(tributyltin) and bis(tributylstannyl)acetylene in N,N-dimethylformamide provided oligomers comprising a recurring benzodiazaborole unit in 98 and 97% yields, respectively.

CONCLUSION: The oligomers comprising a recurring benzodiazaborole unit were obtained under mild reaction conditions in high yields. The expansion of the electron system through the BC and BN bonds of the oligomers was confirmed by UV-visible spectroscopy. The oligomers were photoluminescent in solution and electrochemically active in a film, and they assumed self-assembled stacked structures in the solid state. Copyright © 2008 Society of Chemical Industry