Synthesis and Characterization of New Luminescent 1,10-Phenanthroline- and Pyridine-Containing π-Conjugated Polymers. Their Optical Response to Protic Acid, M<i>ⁿ</i>⁺, and Solvents

New π-conjugated polymers comprised of alternating 1,10-phenanthroline/1,4-didodecyloxybenzene, 1,10-phenanthroline/9,9-dioctylfluorene, or pyridine/1,4-dialkoxybenzene units were prepared by palladium(0)-catalyzed coupling reaction in 84−98% yields. The derived polymers gave Mn of 5400−8800 in GPC analysis, and they possessed good solubility in organic solvents and high thermal stability. Electrochemical reduction (or n-doping) of the polymers proceeded with peaks in the range −2.3 to −2.6 V vs Ag+/Ag. The polymers were highly photoluminescent, and strong blue emission with the peak in the range 412−434 nm was observed in solutions. The emission peak as well as the UV−vis absorption peak of the polymer was influenced by the solvent polarity, protonation, and formation of metal complexes. When the polymers were protonated with trifluoroacetic acid, a large red-shift (ca. 40−60 nm) of the absorption peak was observed. The photoluminescent properties of the polymers were tuned by coordination of the polymer with metal ions. Polymers with long side chains formed an ordered structure in the solid state as judged from their XRD patterns

Synthesis of <i>cis</i>-Bis(heteroaryl)nickel(II) Complexes and Reductive Elimination of Bis(heteroaryl) Products Induced by Protic Acid

Synthesis of cis-Bis(heteroaryl)nickel(II) Complexes and Reductive Elimination of Bis(heteroaryl) Products Induced by Protic Aci

New Alternative Copolymer Constituted of Fluorene and Triphenylamine Units with a Tunable −CHO Group in the Side Chain. Quantitative Transformation of the −CHO Group to −CHCHAr Groups and Optical and Electrochemical Properties of the Polymers

A new alternative functional copolymer, PFT, comprising of fluorene and triphenylamine units with a tunable −CHO group in the side chain was synthesized by the polycondensation of 4-[N,N-di(4-bromophenyl)amino]benzaldehyde with 9,9-dihexylfluorene-2,7-bis(trimethyleneborate) using Pd(PPh3)4 as the catalyst. The polymer was soluble in organic solvents and gave a number-average molecular weight, Mn, of 10 000 and a weight-average molecular weight, Mw, of 17 700. PFT had an intrinsic viscosity [η] of 0.24 dL g-1 in toluene and exhibited the photoluminescence (PL) peak strongly influenced by the kind of the solvents, e.g., at 462 nm in toluene and at 528 nm in NMP. The quantum yield of the PL of PFT also varied from 12% in toluene to less than 1% in NMP. A cast film of PFT showed the emission peak at 497 nm. By using the Wittig reaction, the −CHO group of PFT was quantitatively transformed into trans −CHCHAr groups. The modified products, MPa (Ar = −C6H6) and MPb (Ar = −C6H4OCH3-p), showed a UV−vis peak at 390 nm in solutions and in the solid. MPa and MPb showed PL peaks at 433 and 457 nm, respectively, in toluene. The quantum yields of MPa and MPb rose to 64% and 51%, respectively, from 12% of PFT. A cast film of MPa gave a quantum yield comparable to that of poly(9,9-dioctylfluorene-2,7-diyl). PFT, MPa, and MPb were electrochemically active and received electrochemical oxidation, which was followed by cyclic voltammetry and UV−vis spectroscopy

Synthesis of n-Type Poly(benzotriazole)s Having p-Conducting and Polymerizable Carbazole Pendants

Poly(benzotriazole)s, P(BTz)s, having an n-type benzotriazole-π-conjugated main chain and p-type and electrochemically polymerizable carbazole (CBz) pendant groups, −(CH2)m−CBz (m = 12 or 6) groups, were synthesized by Ni− (for homopolymers) and Pd-promoted (for a copolymer) organometallic polycondensations. The copolymer between benzotriazole with the −(CH2)12−CBz pendant and p-phenylene was soluble in organic solvents and showed a number-average molecular weight (Mn) of 27000 in the GPC analysis. The homopolymers (m = 12, 6) were less soluble, and about half of the polymer was soluble in CHCl3 in the case of m = 12; the soluble part gave an Mn value of 4700. The polymers were photoluminescent with quantum yields of 50−70%. Cyclic voltammograms of the polymers revealed that the polymers were active in electrochemical n-doping in accord with the electron-accepting nature of the benzotriazole main chain. Application of electrochemical oxidation potential to the polymer made the polymer insoluble due to occurrence of electrochemical polymerization of the CBz unit

Synthesis of <i>cis</i>-Bis(heteroaryl)nickel(II) Complexes and Reductive Elimination of Bis(heteroaryl) Products Induced by Protic Acid

Synthesis of cis-Bis(heteroaryl)nickel(II) Complexes and Reductive Elimination of Bis(heteroaryl) Products Induced by Protic Aci

Syntheses of New Alternating CT-Type Copolymers of Thiophene and Pyrido[3,4-<i>b</i>]pyrazine Units: Their Optical and Electrochemical Properties in Comparison with Similar CT Copolymers of Thiophene with Pyridine and Quinoxaline

Four kinds of new π-conjugated copolymers of electron-donating thiophene with highly electron-withdrawing pyrido[3,4-b]pyrazine derivatives have been prepared by using the Stille reaction and electrochemical oxidative polymerization in high yields, and their optical and electrochemical properties have been compared with those of previously reported CT-type π-conjugated polymers. Chemically prepared polymers show an [η] value of about 0.3 dL g-1. The π−π* absorption bands (λmax = ca. 633 nm) of the copolymers are observed at a longer wavelength by about 30 nm than those of similar CT-type copolymers of thiophene with pyridine and quinoxaline. These UV−vis data are considered to reflect a stronger CT interaction between thiophene and pyrido[3,4-b]pyrazine, which has a higher electron-withdrawing ability than pyridine and quinoxaline. The copolymers are electrochemically active in both oxidation and reduction regions. In the reduction (n-doping) region, the copolymers show normal three couples of n-doping and n-undoping between −1.55 and −2.25 V vs Ag/Ag+. On the other hand, they receive oxidation (p-doping) at Epa of 0.9 V vs Ag/Ag+. The electrochemical p- and n-doping of the film of the copolymers is accompanied by changes in its UV−vis spectra (electrochromism), and new absorption bands emerge in the range 900−1500 nm by the p- and n-doping. The X-ray diffraction pattern of the copolymer having a long alkyl side chain suggests self-assembling of the polymer assisted by side chain crystallization

Preparation of π-Conjugated Polymers Composed of Hydroquinone, <i>p</i>-Benzoquinone, and <i>p</i>-Diacetoxyphenylene Units. Optical and Redox Properties of the Polymers

π-Conjugated poly(hydroquinone)s and poly(p-benzoquinone)s have been prepared, and their optical and redox behaviors have been studied. Poly(hydroquinone-2,5-diyl), PPP-2,5-OH, with a weight-average molecular weight of 8500 (determined by the light scattering method) was soluble in DMF. The π−π* absorption peak of hydroquinone at 296 nm is shifted to 345 nm in PPP-2,5-OH. PPP-2,5-OH underwent electrochemical two-step oxidation at about 0.5 and 0.8 V versus Ag/Ag+. Another type of poly(p-hydroquinone)s in an acetylenic main chain was also prepared, and the polymer underwent oxidation with the first oxidation peak at about 1.0 V versus Ag/Ag+. Optical and X-ray diffraction data of the polymers and their precursor polymers suggest stacking of the polymer molecules

New Soluble Poly(aryleneethynylene)s Consisting of Electron-Accepting Benzothiadiazole Units and Electron-Donating Dialkoxybenzene Units. Synthesis, Molecular Assembly, Orientation on Substrates, and Electrochemical and Optical Properties

A new class of poly(aryleneethynylene)s containing an aryl heterocyclic structure were prepared in the yield of higher than 80% by polycondensation between 4,7-dibromo-2,1,3-benzothiadiazole and 2,5-dialkoxy-1,4-diethynylbenzenes with different long side chains using Pd(PPh3)4 and CuI as the catalysts in the presence of triethylamine. All these polymers had a number-average molecular weight, Mn, higher than 12 000 and showed good solubility in chloroform. The polymers were photoluminescent in chloroform and showed metallic luster in the solid state. X-ray diffraction patterns of the powder and cast film (on a platinum plate) of the polymers revealed that the polymers assumed a π-stacked structure in the solid state, and the polymer molecules in the film were ordered on the surface of the platinum plate

Intermolecular Alkynyl Ligand Transfer in Palladium(II) and Platinum(II) Complexes with −C⋮CCOOR and −C⋮CPh Ligands. Relative Stability of the Alkynyl Complexes and Conproportionation of Dialkynyl and Diiodo Complexes of These Metals

An equimolar reaction of trans-Pd(C⋮CCOOMe)2(PEt3)2 with trans-PdI2(PEt3)2 catalyzed by CuI causes conproportionation of the complexes at room temperature, producing trans-PdI(C⋮COOMe)(PEt3)2 in 88% yield, while the reaction without CuI catalyst gives the monoalkynylpalladium complex in approximately 2% yield after a prolonged period. Similar reactions of trans-Pd(C⋮CPh)2(PEt3)2 with trans-PdI2(PEt3)2 with and without CuI catalyst give the alkynyl ligand transfer reaction product trans-PdI(C⋮CPh)(PEt3)2 in 95% and 33% yields, respectively. CuI-catalyzed conproportionation of trans-Pt(C⋮CPh)2(PEt3)2 and trans-PtI2(PEt3)2 occurs more slowly than the corresponding reactions of the Pd complexes; trans-Pt(C⋮CCOOMe)2(PEt3)2 does not react with the diiodoplatinum complex even in the presence of CuI. The alkynyl ligand transfer reaction from trans-Pd(C⋮CCOOMe)2(PEt3)2 to trans-PtI2(PEt3)2 occurs in the presence of CuI catalyst, affording a mixture of several organopalladium and -platinum complexes. The main Pd complex in the reaction mixture is trans-PdI(C⋮CCOOMe)(PEt3)2, while the Pt-containing product is composed of trans-Pt (C⋮CCOOMe)2(PEt3)2, trans-PtI(C⋮CCOOMe)(PEt3)2, and trans-PtI2(PEt3)2 in an approximate 1:2:1 molar ratio. Mixing of trans-Pd(C⋮CCOOMe)2(PEt3)2, trans-PdI2(PEt3)2, and trans-PtI2(PEt3)2 results in the formation of trans-PdI(C⋮CCOOMe)(PEt3)2 in a high yield, while the alkynyl ligand transfer from Pd to Pt complexes is almost negligible. trans-PtI2(PEt3)2 catalyzes the alkynyl ligand transfer between the dialkynyl- and diiodopalladium(II) complexes and remains unchanged in the reaction mixture

Chemical and Electrochemical Oxidation of Thiophene−Pyridine and Thiophene−Pyrimidine Co-Oligomers in Solutions

Chemical and electrochemical oxidation (or p-doping) of three types of π-conjugated co-oligomers, Py−Th−(Th)n−Th−Py (Py = pyridine unit; Th = thiophene unit; 5a, n = 1; 6a, n = 2), Th−Py−(Th)n−Py−Th (5b:  n = 1; 6b:  n = 2), and Pym−Th−(Th)n−Th−Pym (Pym = pyrimidine unit; 5c:  n = 1; 6c:  n = 2), in solution systems has been studied. The chemical oxidation with NOBF4 proceeded with isosbestic points in the UV−vis spectrum. The UV−vis absorption peak of 5a at 418 nm in CH2Cl2 shifted to 456 nm after oxidation of 5a with NOBF4. The oxidized 5a was easily reduced by N2H4 to give the original UV−vis spectrum of 5a, and 5b, 6b, and 5c behaved similarly in the oxidation and reduction. In the oxidation by NOBF4, an (oxidized co-oligomer)/(original neutral co-oligomer) ratio of 1 was attained at [NOBF4] = 1.3 × 10-6, 4 × 10-6, 7 × 10-6, and 9 × 10-6 M for 5a, 6b, 5b, and 5c, respectively. The obtained data are considered to reflect the ease of oxidation of the co-oligomer, which is affected by the electron-accepting nature of the N-containing aromatic unit in the co-oligomer and effective π-conjugated length of the co-oligomer. The cyclic voltammogram of 5a showed three redox couples with anodic peak current potentials of Epa = 0.75, 1.10, and 1.34 V versus Ag+/Ag, respectively. The first oxidation peak was assigned to one-electron oxidation of 5a, and electronic current of the first anodic peak (i) of 5a and 5c was proportional to (scanning rate)1/2. From the i− (scanning rate)1/2 relationship, diffusion constants, D's, of 5a and 5c were estimated to be 9.6 × 10-6 and 1.7 × 10-5 cm2 s-1, respectively. CV data of 5b with the terminal thiophene units indicated occurrence of electrochemical oxidative polymerization of 5b