Diyne Monomers Research Articles

Cascade Cyclopolymerization of 5-Ethynyl-1,8-Nonadiyne Derivatives to Synthesize Low Band Gap Conjugated Polyacetylenes Containing a Fused Bicyclic Structure.

Cyclopolymerization is a powerful method for synthesizing polyacetylenes containing four- to seven-membered rings. However, the structure of the repeat unit only consists of mono-cycloalkene due to the single cyclization of diyne monomers. Herein, we demonstrate a novel cascade cyclopolymerization to synthesize polyacetylenes containing fused bicyclic rings from triyne monomers containing bulky dendrons via sequential cascade ring-closing metathesis. These dendrons provided solubility and stability to the rigid bicyclic polyacetylene backbone. In addition, we controlled the regioselectivity of the catalyst approach by altering its structure and synthesized polymers containing fused bicyclo[4,3,0] or [4,4,0] rings with high molecular weights of up to 120 kg mol-1 . Interestingly, the resulting polymers showed narrower band gaps (down to 1.6 eV) than polymers with mono-cycloalkene repeat units due to the planarization of the conjugated segment resulting from the fused bicyclic structure.

Cascade Cyclopolymerization of 5‐Ethynyl‐1,8‐Nonadiyne Derivatives to Synthesize Low Band Gap Conjugated Polyacetylenes Containing a Fused Bicyclic Structure

AbstractCyclopolymerization is a powerful method for synthesizing polyacetylenes containing four‐ to seven‐membered rings. However, the structure of the repeat unit only consists of mono‐cycloalkene due to the single cyclization of diyne monomers. Herein, we demonstrate a novel cascade cyclopolymerization to synthesize polyacetylenes containing fused bicyclic rings from triyne monomers containing bulky dendrons via sequential cascade ring‐closing metathesis. These dendrons provided solubility and stability to the rigid bicyclic polyacetylene backbone. In addition, we controlled the regioselectivity of the catalyst approach by altering its structure and synthesized polymers containing fused bicyclo[4,3,0] or [4,4,0] rings with high molecular weights of up to 120 kg mol−1. Interestingly, the resulting polymers showed narrower band gaps (down to 1.6 eV) than polymers with mono‐cycloalkene repeat units due to the planarization of the conjugated segment resulting from the fused bicyclic structure.

Cascade Alternating Metathesis Cyclopolymerization of Diynes and Dihydrofuran.

Ruthenium alkoxymethylidene complexes have recently come into view as competent species for metathesis copolymerization reactions when coupled with appropriate comonomer targets. Here, we explore the ability of Fischer-type carbenes to participate in cascade alternating metathesis cyclopolymerization (CAMC) through facile terminal alkyne addition. The combination of diyne monomers and an equal feed ratio of low-strain dihydrofuran leads to a controlled chain-growth copolymerization with high degrees of alternation (>97% alternating diads) and produces degradable polymer materials with low dispersities and targetable molecular weights. When combined with enyne monomers, this method is amenable to the synthesis of alternating diblock copolymers that can be fully degraded to short oligomer fragments under aqueous acidic conditions. This work furthers the potential for the generation of functional metathesis materials via Fischer-type ruthenium alkylidenes.

Nonstoichiometric hydroarylation polyaddition for synthesis of pyrrole-based poly(arylenevinylene)s

Nonstoichiometric polyaddition via the Co-catalyzed hydroarylation of diyne monomers with excess 1-(2-pyrimidinyl)pyrrole was demonstrated.

Room temperature synthesis of polythioamides from multicomponent polymerization of sulfur, pyridine-activated alkyne, and amines

Through the design of a pyridine-activated diyne monomer, the catalyst-free multicomponent polymerizations of sulfur, aromatic alkyne, and a group of commercially available primary and secondary diamines were realized at room temperature or 40 °C.

Synthesis of Pyrrole-Based Poly(arylenevinylene)s via Co-Catalyzed Hydroarylation of Alkynes.

Polyaddition via the Co-catalyzed hydroarylation of 1-(2-pyrimidinyl)pyrrole with aromatic diynes affords poly(arylenevinylene)s under mild conditions. This reaction avoids production of stoichiometric amounts of by-products. Although structural analysis of the obtained polymers reveals the presence of 1,1-vinylidene unit, switching the counter anion of the Co catalyst and steric hindrance of the diyne monomers improves the regioselectivity of the polymers. When a catalyst with bulky counter anions is used for the reaction of less hindered diyne monomers, 1,2-vinylene linkages are formed dominantly over 1,1-vinylidene linkages (93:7). The effect of the regioselectivity of the polymer on the optical and semiconducting properties is also evaluated.

Dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via Concurrent McMurry olefination and alkyne [2+2+2] cycloaddition trimerization reactions mediated by a low-valent titanium reagent

The application of a low-valent titanium reagent recently developed in our group, Ti(O-i-Pr)4/Me3SiCl/Mg, to the McMurry coupling polymerization of aryl dialdehyde monomers and [2 + 2 + 2] cycloaddition polymerization of aromatic diyne monomers is described. Furthermore, on the basis of these reactions, a low-valent titanium-mediated dual-mode coupling copolymerization of aryl dialdehyde and alkynylaldehyde monomers via concurrent McMurry olefination and alkyne cyclotrimerization reactions is proposed.

Synthesis of Functional Polyacetylenes via Cyclopolymerization of Diyne Monomers with Grubbs-type Catalysts.

Metathesis cyclopolymerization (CP) of α,ω-diynes is a powerful method to prepare functional polyacetylenes (PAs). PAs have long been studied due to their interesting electrical, optical, photonic, and magnetic properties which make them candidates for use in various advanced applications. Grubbs catalysts are widely used throughout synthetic chemistry, largely due to their accessibility, high reactivity, and tolerance to air, moisture, and many functional groups. Prior to our entrance into this field, only a few examples of CP using modified Grubbs catalysts existed. Inspired by these works, we saw an opportunity to expand the accessibility and utility of Grubbs-catalyzed CPs. We began by exploring CP with popular and commercially available Grubbs catalysts. We found Grubbs third-generation catalyst (G3) to be an excellent catalyst when we used strategies to stabilize the propagating Ru carbene, such as decreasing the polymerization temperature or using weakly coordinating solvent or ligands. Controlled living polymerizations were demonstrated using various 1,6-heptadiyne monomers and yielded polymers with exclusively 5-membered rings (via α-addition) in the polymer backbone. The strategy of stabilizing the Ru carbene was also critical to successful CP with Hoveyda-Grubbs second-generation (HG2) and Grubbs first-generation (G1) catalysts. We found that decomposed Ru species were catalyzing side reactions which could be completely shut down by decreasing the reaction temperature or using weakly coordinating ligands. While HG2 generally led to uncontrolled polymerizations, we found it to be an effective catalyst for monomers with very large side chains. G1 displayed broader functional group tolerance and thus broader monomer scope than G3. We next looked at our ability to change the regioselectivity of the polymerization by using Z-selective catalysts which favor β-addition and the formation of 6-membered rings in the polymer backbone. While modest β-selectivity could be obtained using Grubbs Z-selective catalyst at low temperatures, we found that by using one of Hoveyda and co-workers' catalysts with decreased carbene electrophilicity, we could achieve exclusive formation of 6-membered rings. We also pursued alternative routes to achieve 6+-membered rings in the polymer backbone by using diyne monomers with increased distance between alkynes. We found that optimizing the monomer structure for CP was an effective strategy to achieve controlled polymerizations. By using bulky substituents (maximizing the Thorpe-Ingold effect) and/or using heteroatoms (shorter bonds) to bring the alkynes closer together, controlled living CP could be achieved with various 1,7-octadiyne and 1,8-nonadiyne monomers. Finally, we took advantage of several inherent properties of controlled CP techniques to prepare polymers with advanced architectures and nanostructures. For instance, the living nature of the polymerization enabled production of block copolymers, the tolerance of very large substituents enabled production of dendronized and brush polymers, and the insolubility or crystallinity of some monomers was utilized for the spontaneous self-assembly of polymers into various one- and two-dimensional nanostructures. Overall, the strategies of stabilizing the propagating Ru carbene, modulating the selectivity and reactivity of the Ru carbene, and enhancing the inherent reactivity of monomers were key to improving the utility and performance of CP with Grubbs-type catalysts. The insight provided by these studies will be important for future developments of CP and other metathesis polymerizations utilizing ring-closing steps.

New 1,2,3-Triazole Containing PolyestersviaClick Step-Growth Polymerization and Nanoparticles Made of Them

High-molecular-weight AA-BB-type aliphatic polyesters were synthesizedviaCu(I)-catalyzed click step-growth polymerization (SGP) following a new synthetic strategy. The synthesis was performed between diyne and diazide monomers in an organic solvent as one pot process using three components and two stages. The dipropargyl esters of dicarboxylic acids (component 1) were used as diyne monomers, di-(bromoacetic acid)-alkylene diesters (component 2) were used as precursors of diazide monomers, and sodium azide (component 3) was used for generating diazide monomers. The SGP was carried out in two steps: at Step 1 dibromoacetates interacted with two moles of sodium azide resulting in diazide monomers which interacted in situ with diyne monomers at Step 2 in the presence of Cu(I) catalyst. A systematic study was done for optimizing the multiparameter click SGP in terms of the solvent, duration of both Step 1 and Step 2, solution concentration, catalyst concentration, catalyst and catalyst activator (ligand) nature, catalyst/ligand mole ratio, and temperature of both steps of the click SGP. As a result, high-molecular-weight (MWup to 74 kDa) elastic film-forming click polyesters were obtained. The new polymers were found suitable for fabricating biodegradable nanoparticles, which are promising as drug delivery containers in nanotherapy.

Homo- and Copolycyclotrimerization of Aromatic Internal Diynes Catalyzed with Co2 (CO)8 : A Facile Route to Microporous Photoluminescent Polyphenylenes with Hyperbranched or Crosslinked Architecture.

This study reports the first Co2 (CO)8 -catalyzed [2+2+2] polycyclotrimerization by the transformation of internal ethynyl groups of aromatic diyne monomers. The reaction yields polycyclotrimers of polyphenylene-type with either hyperbranched or partly crosslinked architecture. The homopolycyclotrimerization of the monomers with two ethynyl groups per one molecule, namely 1,4-bis(phenylethynyl)benzene, 4,4'-bis(phenylethynyl)biphenyl, and 4-(phenylethynyl)phenylacetylene, gives partly crosslinked, insoluble polyphenylenes. The soluble, hyperbranched polyphenylenes are generated via copolycyclotrimerization of 1,4-bis(phenylethynyl)benzene with 1,2-diphenylacetylene (average number of ethynyl groups per monomer molecule < 2). This one-step polycyclotrimerization path to hyperbranched or partly crosslinked polyphenylenes is an alternative to the synthesis of these polymers by Diels-Alder transformation of substituted cyclopentadienones. All polyphenylenes prepared exhibit photoluminescence with emission maxima ranging from 381 to 495 nm. Polyphenylenes with a less compact packing of segments are microporous (specific surface area up to 159 m2 g-1 ), which is particularly important in the case of soluble polyphenylenes because they can be potentially used to prepare microporous layers.

Efficient and Regioselectivity-Tunable Metal-Free Polycycloaddition of Activated Azide and Alkynes.

The transition-metal catalyzed and metal-free click polymerizations have been developed as powerful tools for the construction of functional polymers with linear and hyperbranched structures. The latter provides a thorough solution for the completely removing metallic residues from the products encountered in the former. Compared to the activated alkyne-azide metal-free click polymerization, the activated azide-alkyne one is rarely studied. In this Communication, a perfluorophenyl-activated azide of hexane-1,6-diyl-bis(4-azido-2,3,5,6-tetrafluorobenzoate) is rationally designed and facilely prepared. Through systematical optimization of the reaction conditions, an efficient metal-free perfluorophenylazide-alkyne polycycloaddition is established, and polytriazoles with high molecular weights (up to 166 000) and excellent solubility are obtained in excellent yields (up to 93%) under mild reaction conditions. Interestingly, the regioselectivity of the reaction could be fine-tuned by the solvents and diyne monomers. Therefore, this work provides not only a powerful tool for the preparation of functional polytriazoles, but also an attractive method for fine-tuning their regioregularity.

Synthesis of Cyclic Porphyrin Trimers through Alkyne Metathesis Cyclooligomerization and Their Host-Guest Binding Study.

Cyclic porphyrin trimers were synthesized through one-step cyclooligomerization via alkyne metathesis from diyne monomers. These macrocycles show interesting host-guest binding interactions with fullerenes, selectively binding C70 (6 × 10(3) M(-1)) over C60 and C84 (no binding observed). The fullerene-encapsulated host-guest complex can undergo guest or host exchange in the presence of another guest (2,4,6-tri(4-pyridyl)-1,3,5-triazine) or host (cage COP5) molecule with higher binding affinity.

Synthesis of Hyperbranched Polyphenylacetylene Resins and the Influence of their Molecular Architecture on their Properties

Hyperbranched polyphenylacetylene resins were obtained by the homo-and copolycyclotrimerizations of diynes and monoynes initiated by tantalum-based catalysts, with the aim of exploring new synthetic routes to hyperbranched polyphenylacetylene resins. A group of hyperbranched poly (alkylenephenylenes) (hb-PAPs) were synthesized by TaBr5-Ph4Sn catalyzed polycyclotrimerization of 1,7-octadiyne. To improve the solubility of the homopolymers,the diyne monomers were copolymerized with phenylacetylene. IR,and 1H NMR Spectrum confirmed that the target polymers had formed via a [2+2+2] cyclotrimerization mechanism. The influence of the architecture of homopolymer and copolymer obtained from different kinds of monomer on the thermal properties and solubility were investigated.

Direct Visualization of Surface-Assisted Two-Dimensional Diyne Polycyclotrimerization

Cyclotrimerization of alkynes to aromatics represents a promising approach to two-dimensional conjugated networks due to its single-reactant and atom-economy attributes, in comparison with other multicomponent coupling reactions. However, the reaction mechanism of alkyne cyclotrimerization has not yet been well understood due to characterization challenges. In this work, we take a surface reaction approach to study fundamental polymerization mechanism by using a diyne monomer named 4,4'-diethynyl-1,1'-biphenyl as a test bed. We have succeeded in directly characterizing reactants, intermediates, and their reaction products with the aid of scanning tunneling microscope, which allows us to gain mechanistic insights into the reaction pathways. By combining with density functional theory calculation, our result has revealed for the first time that the polycyclotrimerization is a two-step [2+2+2] cyclization reaction. This work provides an in-depth understanding of polycyclotrimerization process at the atomic level, offering a new avenue to design and construct of single-atom-thick conjugated networks.

A C84 selective porphyrin macrocycle with an adaptable cavity constructed through alkyne metathesis

A bisporphyrin macrocycle was constructed from a porphyrin-based diyne monomer in one step through alkyne metathesis. The fullerene binding studies (C(60), C(70) and C(84)) showed the highest binding affinity of the macrocycle for C(84), which is in great contrast to its bisporphyrin four-armed cage analogue that showed the strongest binding with C(70).

Chain-Growth Cycloaddition Polymerization via a Catalytic Alkyne [2 + 2 + 2] Cyclotrimerization Reaction and Its Application to One-Shot Spontaneous Block Copolymerization

A cobalt-catalyzed alkyne [2 + 2 + 2] cycloaddition reaction has been applied to polymerizations yielding linear polymers via selective cross-cyclotrimerization of yne-diyne monomers, which occurs in a chain-growth manner. Additionally, through control of the alkyne reactivity of the two monomers, this method was efficiently applied to the spontaneous block copolymerization of their mixture. Here we present the proposed mechanism of the catalyst transfer process of this cycloaddition polymerization.

Acetylenic Phenyldithiafulvene: A Versatile Synthon for TTFV-Based Macromolecules

An acetylenic phenyldithiafulvene was developed as a versatile synthon for diverse TTFV-based macromolecular scaffolds. Through different coupling reaction sequences, shape-persistent macrocycles and linear TTFV-embedded polymers have been obtained and thereafter characterized by spectroscopic and voltammetric analyses. The TTFV polymer thin films generated via electropolymerization of a dithiafulvenyl-end-capped diyne monomer showed promising prospects in electrochromic and redox switchable molecular devices.

Luminescent and Axially Chiral π-Conjugated Polymers Linked by Carboranes in the Main Chain

Sonogashira−Hagihara polycondensations of two bis(4-iodophenyl)carborane compounds with axially chiral diyne monomers having binaphthyl unit were carried out to obtain the corresponding chiral π-conjugated polymers having o- or m-carborane segment in the main chain. The polymer structures and their optical properties were characterized by 1H, 13C, and 11B NMR, FT-IR, UV−vis absorption, photoluminescence, and circular dichroism spectroscopies. Photoluminescence study revealed that the polymer having m-carborane exhibited intense blue emission in solution state, whereas polymers having o-carborane exhibited aggregation-induced emission (AIE). All polymers showed strong CD signals, indicating the construction of highly ordered conformation.

Chiral π-conjugated organoboron polymers

Abstract A novel π-conjugated organoboron polymer with a chiral side chain was prepared by way of hydroboration polymerization between an optically active diyne monomer and triisopropylphenylborane. The achiral analog of this organoboron polymer was also prepared as reference material. Optical properties and optical activity were investigated by UV-vis absorption, fluorescence emission, and circular dichroism (CD) spectroscopy. Concentration dependence and the influence of solvent effects upon chiroptical activity are described.

Highly Luminescent BODIPY-Based Organoboron Polymer Exhibiting Supramolecular Self-Assemble Structure

A novel class of rod-coil type-organoboron polymers with p-phenylene-ethynylene as the rod segment and long alkyl chain (decyl group) as coil segment has been prepared from a Sonogashira-Hagihara coupling reaction of a BODIPY-based monomer having bis-iodophenyl and decyl groups with diyne monomers, 1,4-diethynylbenzene (a), 1,4-diethynyl-2,5-bis(trifluoromethyl)benzene (b), and 2,7-diethynyl-9,9-dihexyl-9H-fluorene (c). The characterization by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the strong tendency of the obtained polymers, 2a, 2b, and 2c, to self-assemble into particles in solution and as-casted films on a micron-nm scale. Especially, 2a showed the presence of nm-sized particles and micron-sized fiber-like structures formed by aggregation of each particle. Further, in CHCl3, the gelation of 2a by three-dimensional aggregation of each fiber was observed at room temperature after 24 h. Their luminescent properties showed high energy transfer efficiency from pi-conjugated polymer linkers to BODIPY moieties (PhiF > 71%).