Polymerization Of Diacetylenes Research Articles

Silver to Gold Metallic Luster Changes in Stimuli-Responsive Diacetylene Derivatives Uniquely Arranged within Crystals.

Eye-catching metallic luster materials, especially those whose colors can be controlled by external stimuli, have many potential applications. Here, we present a silver luster material that changes color to gold upon UV irradiation. Diacetylene (DA) derivatives with stilbenes introduced via linkers at both ends (DS-DAn (n = 1-6)) exhibited significantly different metallic luster and color change behaviors depending on the linker carbon number (n). The results revealed that the stacked structure of platelet crystals consisting of DS-DA1 with the shortest linker carbon chain exhibited a silver luster and changed its appearance to gold upon UV irradiation; this was an exceptional property of this material. More importantly, we found a unique crystal structure formed by DS-DA1, where the two assembled states coexisted. Partial topochemical polymerization of DA within this unique crystal structure dramatically changed its color from silver to gold. The findings of this study not only contribute to the development of the basic science of DA polymerization but also facilitate the development of new applications of metallic luster materials due to their attractive features that are adaptable to photomask patterning and UV laser lithography.

Sub-10 μm Soft Interlayers Integrating Patterned Multivalent Biomolecular Binding Environments.

Designing surfaces that enable controlled presentation of multivalent ligand clusters (e.g., for rapid screening of biomolecular binding constants or design of artificial extracellular matrices) is a cross-cutting challenge in materials and interfacial chemistry. Existing approaches frequently rely on complex building blocks or scaffolds and are often specific to individual substrate chemistries. Thus, an interlayer chemistry that enabled efficient nanometer-scale patterning on a transferrable layer and subsequent integration with other classes of materials could substantially broaden the scope of surfaces available for sensors and wearable electronics. Recently, we have shown that it is possible to assemble nanometer-resolution chemical patterns on substrates including graphite, use diacetylene polymerization to lock the molecular pattern together, and then covalently transfer the pattern to amorphous materials (e.g., polydimethylsiloxane, PDMS), which would not natively enable high degrees of control over ligand presentation. Here, we develop a low-viscosity PDMS formulation that generates very thin films (<10 μm) with dense cross-linking, enabling high-efficiency surface functionalization with polydiacetylene arrays displaying carbohydrates and other functional groups (up to 10-fold greater than other soft materials we have used previously) on very thin films that can be integrated with other materials (e.g., glass and soft materials) to enable a highly controlled multivalent ligand display. We use swelling and other characterization methods to relate surface functionalization efficiency to the average distance between cross-links in the PDMS, developing design principles that can be used to create even thinner transfer layers. In the context of this work, we apply this approach using precision glycopolymers presenting structured arrays of N-acetyl glucosamine ligands for lectin binding assays. More broadly, this interlayer approach lays groundwork for designing surface layers for the presentation of ligand clusters on soft materials for applications including wearable electronics and artificial extracellular matrix.

Kinetics and Mechanism of Liquid-State Polymerization of 2,4-Hexadiyne-1,6-diyl bis-(p-toluenesulfonate) as Studied by Thermal Analysis.

A detailed investigation of the liquid-state polymerization of diacetylenes by calorimetric (DSC) and spectroscopic (in situ EPR) thermal analysis techniques is performed. Isoconversional kinetic analysis of the calorimetric data reveals that liquid-state polymerization is governed by a well-defined rate-limiting step as evidenced by a nearly constant isoconversional activation energy. By comparison, solid-state polymerization demonstrates isoconversional activation energy that varies widely, signifying multistep kinetics behavior. Unlike the solid-state reaction that demonstrates an autocatalytic behavior, liquid-state polymerization follows a rather unusual zero-order reaction model as established by both DSC and EPR data. Both techniques have also determined strikingly similar Arrhenius parameters for liquid-state polymerization. Relative to the solid-state process, liquid-state polymerization results in quantitative elimination of the p-toluenesulfonate group and the formation of p-toluenesulfonic acid and a polymeric product of markedly different chemical and phase composition.

Biomimetic Sequence-Templating Approach toward a Multiscale Modulation of Chromogenic Polymer Properties.

Precision control via molecular structure over adaptive conjugated polymer properties in aqueous environments is critical for realizing their biomedical applications. Here, we unravel the dependence of amphiphilic peptide-polydiacetylene (PDA) conjugate properties on the characteristic steric and hydrophobic contributions within peptide segments that serve as a biomimetic template for diacetylene polymerization in water. We investigated the functional impacts of molecular volume and polarity changes brought by dipeptide substitution domains on the following peptide-PDA material properties at multiple length scales: supramolecular assembly behavior, chain conformation-dependent photophysical properties, cell-material interfacing, and for the first time, bulk electrical properties of their films processed in water. A library of peptide-PDAs with systematically varied sequences show that the contributions of steric effects predominantly influence the electronic structure and resulting trends in photophysical properties, while the interplay between size and hydrophobicity of individual residues becomes more significant for higher-order assemblies affecting bulk properties. This work demonstrates sequence-tunable molecular volume and polarity as synthetic handles to rationally modulate PDA material properties across length scales, providing insights into the programmability of biomimetic conjugated polymers with adaptive functionalities.

Polymerization of tetrazine-substituted diacetylenes as aggregates in suspension.

Polydiacetylenes (PDAs) are conjugated polymers that have been widely exploited for their chromogenic and fluorogenic transitions upon exposure to external stimuli and biomolecules of interest. Herein, we propose a comparative study of the polymerization dynamics of two diacetylene derivatives, TzDA1 and TzDA2, in the form of aggregates in suspension prepared by reprecipitation method from organic solvents in water, varying the diacetylene concentration and solvent proportions, and sonication in water, varying the time and temperature. Both derivatives bear a tetrazine fluorophore, which serves both to increase the fluorescence quantum yield of the system and to track the polymerization by fluorescence quenching exclusively by the blue-PDA, and differ by the chain termination. It was shown that adding a butyl ester function in TzDA2 to a simple urethane (TzDA1) influences the polymerizability and kinetics of polymerization of the aggregates in suspension. In addition, we showed that also the preparation method and preparation conditions do have an influence on the polymerization dynamics, suggesting that a careful study of these properties should be carried out before investigating the applications of such objects.

Nanometer-Scale Precision Polymer Patterning of PDMS: Multiscale Insights into Patterning Efficiency Using Alkyldiynamines.

Most high-resolution interfacial patterning approaches are restricted to crystalline inorganic interfaces. Recently, we have shown that it is possible to generate 1 nm resolution functional patterns on soft materials, such as polydimethylsiloxane (PDMS), by creating highly structured striped patterns of functional alkyldiacetylenes on a hard crystalline surface, photopolymerizing to set the molecular pattern as a striped-phase polydiacetylene (sPDA), and then covalently transferring the sPDAs to PDMS. Transfer depends on the diacetylene polymerization, making it important to understand design principles for efficient sPDA polymerization and cross-linking to PDMS. Here, we combine single-molecule and fluorescence-based metrics for sPDA polymerization and transfer, first to characterize sPDA polymerization of amine striped phases, and then to develop a probabilistic model that describes the transfer process in terms of sPDA-PDMS cross-linking reaction efficiency and number of reactions required for transfer. We illustrate that transferred patterns of alkylamines can be used to direct both adsorption of CdSe nanocrystals with alkyl ligand shells and covalent reactions with fluorescent dyes, highlighting the utility of functional patterning of the PDMS surface.

Polymerization of Self-Assembled Tetraazaporphyrins

Polymerization of self-assembled supramolecular structures considerably increases their often limiting thermal and chemical stability, which widens their potential application in commercial products. Particularly interesting for self-assembled materials is the topochemical polymerization of diacetylenes to polydiacetylenes because it can be initiated photochemically and thermally without the need for additives, it proceeds with minimal structural changes, and it generates new functionality since polydiacetylene is a 1-dimensional organic semiconductor and absorbs visible light. Polydiacetylenes have been generated in single crystals, gel phases, thin films, and membranes but their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials.Presented here are tetraazaporphyrins that contain eight alkyl chains with diacetylene groups to probe their mesomorphism and conversion into multifunctional polydiacetylene materials. While incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favour of nematic mesomorphism. Still, polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by GPC) than what has been obtained in gel phases of related compounds. Formation of polydiacetylene was confirmed by Raman spectroscopy and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both, its nematic structure and the incorporation of eight side-chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. AFM studies of films casted onto silicon wafers revealed a grid-like structure of connected nanofibers.Tahir et al. Langmuir 2019, 35, 15158

Intrinsically Porous Polydiacetylene from a Functionalized Bowl-Shaped Hexaphenoxycyclotriphosphazene Derivative

Intrinsic porosity in polymeric materials arises from the formation of a continuous network of interconnected voids and is a direct consequence of the shape and rigidity of the molecular building blocks. To obtain well-defined pores with narrow size distributions, the polymerization of rigid and sterically hindered monomers must not interfere with the pore formation and should avoid the use of additives that may occupy voids. Polydiacetylenes can be generated by the topochemical polymerization of diacetylene-bearing molecules favorably arranged in crystals, gels, thin films, or vesicles. Polydiacetylene formation in amorphous materials has been sparsely studied because higher-order self-assembled structures are assumed to be required for the topochemical polymerization of 1,3-butadiyne to occur. In this study, a bulky hexachlorocyclotriphosphazene core (N3P3Cl6) was functionalized with six diacetylene-containing alkyl chains and successfully converted to an intrinsically porous multifunctional polydiacetylene. The successful formation of the polydiacetylene was confirmed by Raman spectroscopy, and the porous structure of the resulting materials was verified by X-ray diffraction and Brunauer–Emmett–Teller surface area measurements. This investigation revealed a significant change in the porous structure after polymerization, leading to a 5-fold increase in specific surface area. Overall, the topochemical polymerization of diacetylenes is a promising strategy for the preparation of functional materials, which is shown to be compatible with rather amorphous phases of bulky molecules. The results obtained from this investigation give access to a range of porous polydiacetylene materials for potential applications in organic electronics, gas adsorption, and other related fields.

Polymerization of Self-Assembled Tetraazaporphyrins

Polymerization of self-assembled supramolecular structures considerably increases their often limiting thermal and chemical stability, which widens their potential application in commercial products. Particularly interesting for self-assembled materials is the topochemical polymerization of diacetylenes to polydiacetylenes because it can be initiated photochemically and thermally without the need for additives, it proceeds with minimal structural changes, and it generates new functionality since polydiacetylene is a 1-dimensional organic semiconductor and absorbs visible light. Polydiacetylenes have been generated in single crystals, gel phases, thin films, and membranes but their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. Presented here are tetraazaporphyrins that contain eight alkyl chains with diacetylene groups to probe their mesomorphism and conversion into multifunctional polydiacetylene materials. While incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favour of nematic mesomorphism. Still, polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by GPC) than what has been obtained in gel phases of related compounds. Formation of polydiacetylene was confirmed by Raman spectroscopy and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both, its nematic structure and the incorporation of eight side-chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. AFM studies of films casted onto silicon wafers revealed a grid-like structure of connected nanofibers.

Topochemical Polymerization of a Nematic Tetraazaporphyrin Derivative To Generate Soluble Polydiacetylene Nanowires.

Polydiacetylenes are well-established one-dimensional organic semiconductors that have been generated by photochemical and thermal polymerizations of diacetylenes in single crystals, gel phases, thin films, and membranes. Their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher-ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. The polymerization of diacetylenes in a mesophase may also increase the stability of the self-assembled supramolecular structure. Here, the dye and discotic mesogen tetraazaporphyrin was decorated with eight diacetylene-containing alkyl chains to probe its mesomorphism and conversion into multifunctional polydiacetylene materials. While the incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favor of nematic mesomorphism. Still, the polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by gel permeation chromatography) than what has been obtained in gel phases of related compounds. The formation of polydiacetylene was confirmed by Raman spectroscopy, and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both its nematic structure and the incorporation of eight side chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. Atomic force microscopy studies of films on silicon wafers revealed a grid-like structure of connected nanofibers. This study demonstrates the requirements for the formation of multifunctional mesomorphic polydiacetylene materials from mesomorphic precursors and their advantages. Optimization of the presented molecular design should give access to other mesophases and, consequently, functional polydiacetylene materials with tunable structures and optoelectronic properties.

Biphasic Formation of 2D Nanomembranes by Photopolymerization of Diacetylene Lipids as Revealed by Infrared Difference Spectroscopy.

Two-dimensional nanomembranes are promising materials for filtration or separation by providing the basis for controlled and rapid transport between two compartments. The polymerization by UV light of diacetylene-containing lipids at an interface produces free-standing 2D nanomembranes. Here, we analyzed in situ the nanomembrane formation of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC) and 1-palmitoyl-2-(10,12-tricosadiynoyl)-sn-glycero-3-phosphoethanolamine (PTPE) on germanium using light-induced infrared difference spectroscopy with attenuated total reflection to obtain insights into the kinetics and mechanism of the polymerization process. Our interpretation is supported by atomic force microscopy and density functional theory. Formation of the polymer network is evidenced by changes in the frequency of C═O stretches acting as infrared probes. However, spectral and kinetic analysis revealed a biphasic process in the monolayer. In both phases, losses in signal of CH2 stretches are observed which are not in agreement with the accepted mechanism of chain propagation for diacetylene polymerization. These signals are dominant in the second phase and are assigned to termination reactions with some contributions from intramolecular consecutive reactions. This finding now provides a spectroscopic measure for the identity and integrity of the nanomembrane complementary to microscopic analysis. We deduce that limited 2D mobility on the solid support promotes intramolecular termination, leading to smaller domains.

A triclinic polymorph of N-[5-(diphenylamino)penta-2,4-diyn-1-yl]benzamide

The title compound, C24H18N2O, was been described previously in the space group P21/c with Z = 4 [Kawashima &amp; Okuno (2017). IUCrData, 2, x170277]. The current P\overline{1} polymorph was obtained from a chloroform–ethanol solution. The molecular structure in this polymorph is slightly different from the previously reported structure, with different dihedral angles of the two N-phenyl groups to the ynamine plane; these are 79.99 (11) and 12.09 (11)° in the polymorph reported here. The molecules form dimers through four C—H...π interactions. Furthermore, in this polymorph, the molecules stack along the a axis to form a molecular arrangement that would be suitable to promote the solid-state polymerization of diacetylenes.

Colloidally Stable Monolayer Nanosheets with Colorimetric Responses.

Despite the discovery of chromogenic-layered materials for decades of years, fabrication of colloidally stable monolayer organic 2D nanosheets in aqueous media with colorimetric responses is still challenging. Herein reported is the first solution synthesis of chromic monolayer nanosheets via the topochemical polymerization of self-assembled amphiphilic diacetylenes in aqueous media. The polydiacetylene (PDA) nanosheets are ≈3-4 nm thick in solution and only ≈1.9 nm thick in the dried state, while the lateral size can reach several micrometers. Moreover, the aqueous stability endows PDA nanosheets with excellent processability, which can further assemble into films via vacuum filtration or act as an ink for high-resolution inkjet printing. The filtrated films and printed patterns exhibit fully reversible blue-to-red thermochromism, and the film also displays an interesting reversible colorimetric transition in response to near-infrared light, which is not reported for other PDA-only systems. The present colloidal PDA nanosheets should represent a new kind of chromic organic 2D nanomaterials that may be applied as novel building blocks for developing intelligent hybrid materials and may also find diverse sensing, display and/or anticounterfeiting applications.

Tuning of the Topochemical Polymerization of Diacetylenes Based on an Odd/Even Effect of the Peripheral Alkyl Chain: Thermochromic Reversibility in a Thin Film and a Single-Component Ink for a Fountain Pen.

The topochemical polymerization of diacetylenes (DAs) is closely related to the length of their alkyl chain. DA monomers have two types of alkyl chain side groups: the inner alkyl chain and the outer alkyl chain, that is, the peripheral alkyl chain. Herein, we designed and synthesized a series of DA monomers that possess bis-amide linkages with different peripheral alkyl chains ( n = 6-9; DA1-DA4). The peripheral alkyl chain length of these DA monomers exhibits an odd/even effect on topochemical polymerization. The polymerization of DAs was achieved only when n is an odd number, whereas no polymerization occurred when n is an even number. The odd/even effect on the topochemical polymerization was also investigated using ab initio density functional theory calculations. The thermochromic reversibility of polydiacetylenes (PDAs) was investigated using UV-vis absorption spectroscopy at temperatures ranging from 20 to 60 °C. Monomer DA2 was used as a single-component ink solution in a fountain pen that can be transformed into thermochromic letters on conventional paper. Furthermore, a PDA-embedded polyethylene oxide film was included to monitor the thermochromic reversibility and was found to exhibit excellent thermochromic reversibility between 20 and 100 °C and stability, enabling storage for a few months without deformation. Finally, a green-colored patterned polymer film is readily obtained by a subtractive color (blue and yellow) mixing method and exhibits high thermochromic reversibility at temperatures between 20 and 100 °C.

An emissive rigid tetraphenylethylene-based molecule and its thermal polymerization

Emissive molecules which not only emit at low concentrations, but also are fluorescent in aggregated state, have attracted considerable interests. Herein, we report an emissive molecule 1 based on tetraphenylethylene (TPE) in which two diacetylenes (DAs) are induced to restrict the rotation of phenyl rings in TPE, and consequently preserves the fluorescence in diluted solution, while it still shows aggregation-induced emission (AIE) effect in the solid state. Crystalline microfibers of 1 with DAs well-aligned are also constructed upon vapor diffusion method. Furthermore, the thermal induced polymerization of DAs in 1 could occur via heating the single crystals of 1 to afford a new porous polymer.

Chromogenic Tubular Polydiacetylenes from Topochemical Polymerization of Self-Assembled Macrocyclic Diacetylenes

Tubular materials formed by self-assembly of small organic molecules find great utility in chemical and material science. Conventional tubular structures often lack stability because noncovalent molecular interactions are responsible for their conformational integrities. Herein we report the development of covalently linked chromogenic organic nanotubes which are prepared by using topochemical polymerization of self-assembled macrocyclic diacetylenes (MCDAs). Crystal structures of five MCDAs having different diameters were elucidated, and four of these substances were transformed to tubular polydiacetylenes (PDA) by UV-induced polymerization. Surprisingly, MCDA-1 was found to self-assemble in stacks with a tilt angle of 62.1°, which significantly deviates from the optimal value for polymerization of 45°. This observation suggests that geometric parameters derived using linear diacetylene (DA) models might not be strictly applicable to polymerization of MCDA systems. Blue-phase PDAs obtained by polymerizat...

Diacetylene polymerization on a bulk insulator surface.

Molecular electronics has great potential to surpass known limitations in conventional silicon-based technologies. The development of molecular electronics devices requires reliable strategies for connecting functional molecules by wire-like structures. To this end, diacetylene polymerization has been discussed as a very promising approach for contacting single molecules with a conductive polymer chain. A major challenge for future device fabrication is transferring this method to bulk insulator surfaces, which are mandatory to decouple the electronic structure of the functional molecules from the support surface. Here, we provide experimental evidence for diacetylene polymerization of 3,3'-(1,3-butadiyne-1,4-diyl)bisbenzoic acid precursors on the (10.4) surface of calcite, a bulk insulator with a band gap of around 6 eV. When deposited on the surface held at room temperature, ordered islands with a (1 × 3) superstructure are observed using dynamic atomic force microscopy. A distinct change is revealed upon heating the substrate to 485 K. After heating, molecular stripes with a characteristic inner structure are formed that excellently match the expected diacetylene polymer chains in appearance and repeat distance. The corresponding density functional theory computations reveal molecular-level bonding patterns of both the (1 × 3) superstructure and the formed striped structure, confirming the assignment of on-surface diacetylene polymerization. Transferring the concept of using diacetylene polymerization for creating conductive connections to bulk insulator surfaces paves the way towards application-relevant systems for future molecular electronic devices.

Topochemical polymerization of diacetylenes

Since the discovery of conducting polymers, they have received considerable attention both from academic and industry due to their attractive advantages of light weight, low cost, and easy processing, which make them demonstrate a wide range of applications. Over the past decades, significant advances have been achieved in this field with the development of high performance polymeric semiconductors and device fabrication techniques. However, there are still many scientific questions existing in this field, such as the unclear charge transport physics in conjugated polymers due to disordered molecular structures in the widely investigated films. Compared to thin films, single crystals possess long-range molecular order, no grain boundaries and no defects, which are seen as the best candidates for revealing the intrinsic charge transport of materials. However, it has been a big challenge for the crystallization of polymers directly from solution, and even is elusive for the conjugated polymers due to their intrinsic electron-rich conjugated backbone structures. Topochemical polymerization where under a certain reaction condition, the preorganized monomer crystals could be directly changed to their corresponding polymer crystals with a minimum amount of atomic and molecular movement, that is realizing the single-crystal-to-single-crystal transformation would provide us a promising solution. Compared to traditional solution process, with this method, we can possibly realize two goals: (1) the controllable synthesis because the first crystal growth process is from the monomer molecules; (2) the possible obtainment of higher molecule-weight polymer chains because we do not need consider their solubility problem like that from solution synthesis.

Use of radiochromic film as a high-spatial resolution dosimeter by Raman spectroscopy.

Due to increasing demand for high-spatial resolution dosimetry, radiochromic films have been investigated as potential candidates but are often limited by the scanning system, e.g., flatbed optical scanner. In this study, Raman spectroscopy in conjunction with a microscope was selected as an alternative method for high-spatial resolution dosimetry of radiochromic film. Unlaminated Gafchromic™ EBT3 films were irradiated with doses between 0 and 50 Gy using 6 MV x-rays of a clinical linear accelerator. Depth profiling from the surface of unlaminated film was performed to acquire the maximum Raman intensity peaks of C≡C and C=C stretching bands of diacetylene polymer. The Raman mapping technique for a region of interest (200 × 200, 30 × 30 μm(2)) was developed to reduce a large variation in a Raman spectrum produced with a sampling resolution of a few μm. The preprocessing of Raman spectra was carried out to determine a dosimetric relationship with the amount of diacetylene polymerization. Due to partial diacetylene polymerization upon irradiation, two Raman peaks of C=C and C≡C stretching bands were observed around 1447 and 2060 cm(-1), respectively. The maximum intensities of the two peaks were obtained by positioning a focused laser spot on the surface of unlaminated film. For the dose range of 0-50 Gy, the band heights of both C≡C and C=C peaks increase asymptotically with increasing doses and can be fit with an exponential function of two components. The relative standard deviation in Raman mapping was found to be less than ±5%. By using this technique, dose uniformity was found to be within ±2%. The Raman intensity for C=C and C≡C peaks increases with an increase in the amount of diacetylene polymerization due to an increase in dose. This study shows the potential of Raman spectroscopy as an alternative for absolute dosimetry verifications with a high-spatial resolution of a few μm, but these findings need to be further validated for the purpose of microdosimetry.

Preparations, crystal structures and DFT calculation of diacetylene derivatives carrying nicotinic esters

Novel three diacetylene derivatives 1–3, which carry a pyridine ring as a pendant group, have been successfully prepared and crystallographically analyzed. In compound 1, the molecular stacks form a layered structure within the ac plane. In 2, the molecules make a columnar stack along the a axis. In 3, the molecules have a dimeric form and the dimers make a one-dimensional stack along the b axis.The all compounds make a columnar stack, but conformation at nicotinic ester part is found to have a crucial role for molecular arrangement. The gauche conformation at nicotinic ester part (1 and 2) makes an intermolecular p–p interaction between the pyridine groups. This interaction between the stacks prevents an independent molecular stack in 1, and the interaction within the stack in 2 makes larger inclination angles than the ideal one for solid-state polymerization of diacetylenes. The anti conformation in 3, caused by N-H···N hydrogen-bonded dimer, makes it enable to stack one-dimensionaly with a moderate inclination angle, which is favorable for the polymerization.