Butadiyne Moieties Research Articles

Preparation and characterization of macrocyclic butadiyne derivatives for tubular polydiacetylenes

Ring monomers with one butadiyne moiety for solid-state polymerization, two amide groups for intermolecular hydrogen bonding, and two 3,4,5-trialkoxyphenyl groups for self-assembling and solubilization were synthesized. Depending on solvent and concentration, the monomers formed the gels. When the monomers solidified from the solutions, the structures of nanofiber aggregates were observed. The FT-IR and X-ray diffraction studies suggested that the ring monomers stacked to formed tubular nanofibers and they were bundled to form the aggregates. From the polymerization behavior monitored by visible diffuse reflectance spectra, regular 1,4-addition of butadiyne moieties was confirmed to be polydiacetylenes but its π-conjugated backbones were distorted. They did not show polymorphism in the solidification conditions performed.

High-Yield Formation of Graphdiyne Macrocycles through On-Surface Assembling and Coupling Reaction.

Rationally designed halogenated hydrocarbons are widely used building blocks to fabricate covalent-bonded carbon nanostructures on surfaces through a reaction pathway involving generation and dissociation of organometallic intermediates and irreversible covalent bond formation. Here, we provide a comprehensive picture of the on-surface-assisted homocoupling reaction of 1,3-bis(2-bromoethynyl)benzene on Au(111), aiming for the synthesis of graphdiyne nanostructures. Submolecular resolution scanning tunneling microscopy and noncontact atomic force microscopy observations identify the organometallic intermediates and their self-assemblies formed in the dehalogenation process. The demetallization of the organometallic intermediates at increased temperatures produces butadiyne moieties that spontaneously formed two different covalent structures ( i.e., graphdiyne zigzag chains and macrocycles), whose ratio was found to depend on the initial coverage of organometallic intermediates. At the optimal condition, the stepwise demetallization and cyclization led to a high-yield production of graphdiyne macrocycles up to 95%. Statistical analysis and theoretical calculations suggested that the favored formation of macrocycles resulted from the complex interplay between thermodynamic and kinetic processes involving the organometallic bonded intermediates and the covalently bonded butadiyne moieties.

Synthesis, Crystal Structures, and Solid-State Polymerization of 8-[4-(Dimethylamino)phenyl]octa-5,7-diynyl Carbamates

Six butadiyne monomers with (dimethylamino)phenyl and N-substituted urethane substituents were synthesized and their crystal structures and solid-state polymerization were investigated. In five of the six monomers, directions of the butadiyne stacking and the intermolecular hydrogen bonding between urethane groups coincided, and translational distance d between adjacent butadiyne moieties was around 5 Å. Among them, four monomers showed angle θ between the translation axis of the monomers and the butadiyne moiety of around 45°, which is appropriated for regular 1,4-addition polymerization. These geometries resulted in formation of polydiacetylenes with characteristic excitonic absorption and relatively high conversion. One monomer was found to have large θ, and the regular polymerization was not recognized to be quite low conversion. However, in the remaining one monomer among six, the directions of butadiyne stacking and intermolecular hydrogen bonding were different and d was much longer than 5 Å. However, distance between reacting carbons for 1,4-addition was short enough resulting in comparable conversion without regular polymerization. Although introduction of urethane group is effective to increase probability of the solid-state polymerization of butadiynes, hydrogen bonding direction, methylene chain conformation, and disorder of the aromatic rings were found to afford the variation from the appropriate conditions.

An Alkyne Rod to Constrain a Peptide Backbone in an Extended Conformation

An N,N′‐bound rod‐shaped diyne bridge was introduced into a peptide to constrain the peptide backbone in an extended conformation. Linear precursors were achieved via solid‐phase synthesis using simple commercially available building blocks. Subsequently, 13‐ to 15‐membered peptide macrocycles were obtained in excellent crude purity via in solution copper‐catalyzed cyclization. Density functional theory calculations of the lowest energy conformers suggested that the strain inside the macrocycle caused only slight deformation of the binding angles of the butadiyne moiety.

Synthesis of ordered carbonaceous frameworks from organic crystals

Despite recent advances in the carbonization of organic crystalline solids like metal-organic frameworks or supramolecular frameworks, it has been challenging to convert crystalline organic solids into ordered carbonaceous frameworks. Herein, we report a route to attaining such ordered frameworks via the carbonization of an organic crystal of a Ni-containing cyclic porphyrin dimer (Ni2-CPDPy). This dimer comprises two Ni–porphyrins linked by two butadiyne (diacetylene) moieties through phenyl groups. The Ni2-CPDPy crystal is thermally converted into a crystalline covalent-organic framework at 581 K and is further converted into ordered carbonaceous frameworks equipped with electrical conductivity by subsequent carbonization at 873–1073 K. In addition, the porphyrin’s Ni–N4 unit is also well retained and embedded in the final framework. The resulting ordered carbonaceous frameworks exhibit an intermediate structure, between organic-based frameworks and carbon materials, with advantageous electrocatalysis. This principle enables the chemical molecular-level structural design of three-dimensional carbonaceous frameworks.

Synthesis and Solid-State Polymerization of a Macrocyclic Compound with Two Butadiyne Units

Abstract A macrocyclic compound 1 with two butadiyne and four dodecyloxy-substituted benzamide moieties was successfully synthesized, and its ring structure was confirmed by the MALDI-TOF mass spectra and the 1H NMR spectra. Compound 1 showed two modifications depending on solvent for the solidification. Characteristic excitonic absorption bands of polydiacetylene were observed at around 500 nm for one of the modifications after UV irradiation. Quantitative conversion of butadiyne moieties to the corresponding polydiacetylene structure was confirmed by the Raman spectra.

Enhanced Charge Separation and FRET at Heterojunctions between Semiconductor Nanoparticles and Conducting Polymer Nanofibers for Efficient Solar Light Harvesting.

Energy harvesting from solar light employing nanostructured materials offer an economic way to resolve energy and environmental issues. We have developed an efficient light harvesting heterostructure based on poly(diphenylbutadiyne) (PDPB) nanofibers and ZnO nanoparticles (NPs) via a solution phase synthetic route. ZnO NPs (~20 nm) were homogeneously loaded onto the PDPB nanofibers as evident from several analytical and spectroscopic techniques. The photoinduced electron transfer from PDPB nanofibers to ZnO NPs has been confirmed by steady state and picosecond-resolved photoluminescence studies. The co-sensitization for multiple photon harvesting (with different energies) at the heterojunction has been achieved via a systematic extension of conjugation from monomeric to polymeric diphenyl butadiyne moiety in the proximity of the ZnO NPs. On the other hand, energy transfer from the surface defects of ZnO NPs (~5 nm) to PDPB nanofibers through Förster Resonance Energy Transfer (FRET) confirms the close proximity with molecular resolution. The manifestation of efficient charge separation has been realized with ~5 fold increase in photocatalytic degradation of organic pollutants in comparison to polymer nanofibers counterpart under visible light irradiation. Our results provide a novel approach for the development of nanoheterojunctions for efficient light harvesting which will be helpful in designing future solar devices.

Substituted diphenyl butadiynes: a computational study of geometries and electronic transitions using DFT/TD-DFT.

This work is aimed at theoretical understanding of electronic absorption and emission energies of a series of substituted diphenyl butadiynes through an assessment of several TDDFT functionals and a detailed study of solvent effects on their ground and excited state structures and properties. Out of a series of functionals examined, the coulomb attenuated DFT functional CAM-B3LYP is found to be most successful in predicting charge transfer absorption and emission energies of such derivatives. However, TDDFT potential energy surfaces obtained from hybrid functionals such as B3LYP and PBE0 are found to give a good description of the stability of locally excited (LE) and intramolecular charge transfer (ICT) states as a function of torsional angle, for the butadiynyl fluorophores. Interesting structural variations are observed in the ground and excited state optimized geometries of the fluorophores. The ICT emission of the butadiynyl fluorophores is observed to originate from the twisted state where the two phenyl rings in the diphenyl butadiyne get twisted around the butadiyne moiety. A bending of the butadiyne moiety is noted for some of the butadiynyl derivatives in the ICT emissive state. In addition, the direction of absorption and emission transition dipole moment vectors of the butadiynyl fluorophores is found to depend on the nature of substituents present at the periphery of the diphenyl butadiyne moiety.

Functionalization of Open Two-Dimensional Metal–Organic Templates through the Selective Incorporation of Metal Atoms

Surface-confined molecular networks can serve as templates to steer the adsorption and organization of secondary ligands, metal atoms, and clusters. Here, the incorporation of Ni atoms and clusters into open two-dimensional robust metal–organic templates self-assembled from butadiyne dibenzoic acid molecules and Fe atoms on Au(111) and Ag(100) surfaces is investigated by scanning tunneling microscopy. The metal substrate plays a crucial role in the interaction of Ni atoms with the metal–organic host networks. On Ag(100) the metal–organic template steers the growth of Ni clusters underneath the network pattern near the central butadiyne moiety. In contrast, on Au(111) Ni interacts preferentially with the benzene rings forming size-limited clusters inside the network cavities. Thereby, on both surfaces Ni clusters consisting of a few atoms with both high areal density and thermal stability up to 450 K are realized. The Ni-functionalized networks enable the coordination of additional molecules into the open structures demonstrating the utilization of selective interactions for the assembly of multicomponent architectures at different organizational stages.

Soluble Conjugated One-Dimensional Nanowires Prepared by Topochemical Polymerization of a Butadiynes-Containing Star-Shaped Molecule in the Xerogel State

A star-shaped molecule with three butadiyne moieties attached to a central phenyl core was self-assembled via organogel formation in different solvents and subjected to UV irradiation in its xerogels form to give a soluble conjugated 1D nanowire made of three connected polydiacetylene (PDA) chains. The resulting polymer has a slightly lower optical band gap than its linear counterpart and presents no chromism property, indicative of the rigid nature of the polymer thus obtained.

Hydrindacene-Based Acetylenic Macrocycles with Horizontally and Vertically Ordered Functionality Arrays

The macrocyclization of 2,6-diethynyl hydrindacenes (1) with functional groups at mutually perpendicular positions results in the formation of novel macrocycles which, as a result of the hindered rotation of the hydrindacene units, possess directionally persistent peripheral functionalities. The two hydrindacene units in the dimer macrocycle (2) have been shown to interact electronically through their respective butadiyne moieties, whereas the trimer macrocycle (3) demonstrates a moderate degree of geometrical flexibility as a result of the five-membered hydrindacene rings. In addition, these trimer macrocycles contain a central cavity suitably sized for the inclusion of various solvent molecules. These new macrocycles can be further modified by introducing π-conjugated side groups, such as styryl and thienyl groups, as well as by attaching a variety of peripheral ester groups.

Topochemical Polymerization of Phenylacetylene Macrocycles: A New Strategy for the Preparation of Organic Nanorods

Soluble organic nanorods were prepared from phenylacetylene macrocycles using the topochemical polymerization of butadiyne moieties placed both inside and outside the macrocycles' skeletons. Macrocycles containing amide groups were self-assembled in a columnar fashion through the formation of an organogel in ethyl acetate. Upon irradiation with UV light, the Raman signals associated with butadiyne units completely vanished, indicating the creation of covalently linked nanorods.

Novel Bis(4,4′-dipyridylamine) Ligand with a Flexible Butadiyne Linker: Syntheses, Structures, and Photoluminescence of d10 Metal Coordination Polymers

The design and syntheses of novel ligands are essential for developing coordination compounds with novel structures and interesting properties. In this work, we designed and synthesized a novel ligand bis(4,4′-dipyridylaminophenylene)butadiyne (L) by attaching two 4,4′-dipyridylamine moieties to a flexible butadiyne linker. Starting from this novel ligand, seven coordination polymers [Zn2L(HCOO)3(OH)]n (1), [Cd2L2Cl4]n·3nDMF·3nH2O (2), [CdLBr2]n (3), [Cd6L3(SO4)6]n·4nMeCN (4), [Hg2LBr4]n·3nCH2Cl2·nH2O (5), [Cu2LI2]n·0.5nCH2Cl2 (6), and [Ag2L(H2O)2]n(NO3)2n·2nH2O (7) were synthesized. Single-crystal X-ray diffraction analyses revealed that two forms of the ligand crystals, L and L·0.5DMF present straight and bent conformations, respectively, because of the flexibility of the butadiyne unit. A rich structural diversity was observed for its d10 metal complexes. Complexes 1 and 5 present ladder-like structures. In complexes 2 and 4, the ligand molecules are linked by metal atoms to afford 3D supramolecular structures. It is noteworthy that the 3D structure of complex 4 consists of interesting infinite {Cd6(SO4)6}∞ chains, whereas complexes 3, 6, and 7 exhibit 2D network structures. Interestingly, in the crystal of complex 7, each ligand links four metal ions and each Ag ion bridges two ligands, leading to the formation of undulated 2D sheets with large cavities composed of 66-membered metallomacrocycles, which are interpenetrated by three other such 2D sheets, affording a 4-fold interpenetrated structure. In summary, the complex structures are dependent on the metal ions and the anions. In addition, the flexibility of the butadiyne moiety provides additional means for modulating the structures. Solid state photoluminescence of the free ligand and the complexes shows emission maxima within the range of 420–515 nm, which can be modulated by the conformations of the ligand in addition to the variation of the metal ions and anions, and the introduction of the butadiyne unit has a bathochromic effect.

Supramolecular Structures and Photoelectronic Properties of the Inclusion Complex of a Cyclic Free‐Base Porphyrin Dimer and C60

A cyclic free-base porphyrin dimer H4-CPD(Py) (CPD = cyclic porphyrin dimer) linked by butadiyne moieties bearing 4-pyridyl groups self-assembles to form a novel porphyrin nanotube in the crystalline state. The cyclic molecules link together through nonclassical C-H⋅⋅⋅N hydrogen bonds and π–π interactions of the pyridyl groups along the crystallographic a axis. H4-CPD(Py) includes a C60 molecule in its cavity in solution. In the crystal structure of the inclusion complex (C60⊂H4-CPD(Py)), the dimer “bites” a C60 molecule by tilting the porphyrin rings with respect to each other, and there are strong π–π interactions between the porphyrin rings and C60. The included C60 molecules form a zigzag chain along the crystallographic b axis through van der Waals contacts with each other. Femtosecond laser flash photolysis of C60⊂H4-CPD(Py) in the solid state with photoexcitation at 420 nm shows the formation of a completely charge-separated state {H4-CPD(Py)·+ + C60·−}, which decays with a lifetime of 470 ps to the ground state. The charge-carrier mobility of the single crystal of C60⊂H4-CPD(Py) was determined by flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements. C60⊂H4-CPD(Py) has an anisotropic charge mobility (Σμ = 0.16 and 0.13 cm2 V(−1) s(−1)) along the zigzag chain of C60 (which runs at 45° and parallel to the crystallographic b axis). To construct a photoelectrochemical cell, C60⊂H4-CPD(Py) was deposited onto nanostructured SnO2 films on a transparent electrode. The solar cell exhibited photovoltaic activity with an incident photon to current conversion efficiency of 17%.

Anisotropic High Electron Mobility and Photodynamics of a Self-Assembled Porphyrin Nanotube Including C60 Molecules

A cyclic porphyrin dimer (Ni2−CPDPy) linked by butadiyne moieties bearing 4-pyridyl groups includes a C60 molecule inside its cavity in solution to give a 1:1 inclusion complex (C60⊂Ni2−CPDPy). The charge-transfer (CT) band is observed at 645 nm in the UV−vis absorption spectrum of the solution of C60⊂Ni2−CPDPy. In the cyclic voltammogram of C60⊂Ni2−CPDPy, a small anodic shift of the porphyrin oxidation potential and a small cathodic shift of the fullerene reduction potential compared with their original redox potentials are indicative of CT interaction from the porphyrin to C60. In the crystal structure of C60⊂Ni2−CPDPy, a porphyrin nanotube is formed by the self-assembly of Ni2−CPDPy. Ni2−CPDPy molecules link together through nonclassical C−H···N hydrogen bonds and π−π interactions of the pyridyl groups along the crystallographic b axis. The included C60 molecules are linearly arranged in the nanotube to afford a supramolecular peapod. The charge-carrier mobility of the single crystal of C60⊂Ni2−CPDPy w...

Synthesis and solid-state polymerization of a methylene-chain-modified butadiyne derivative

5,7-Dodecadiyn-1,12-diyl bis[ N-(butoxycarbonylmethyl)carbamate] abbreviated as 4BCMU is one of the typical monomers for solid-state polymerization to form polydiacetylene. In this study, we modified 4BCMU by substituting methylene groups to oxygen atoms. Namely, 3,10-dioxa-5,7-dodecadiyn-1,12-diyl bis[ N-(butoxycarbonylmethyl)carbamate] (DO-4BCMU) was synthesized and the replacement effects on the monomer properties were investigated. In powder X-ray diffraction experiments, spacings for the layered structure in 4BCMU and DO-4BCMU crystals were found to be 2.74 nm and 3.56 nm, respectively, and large crystal structural difference was confirmed. The polymer absorption maxima of 4BCMU and DO-4BCMU were observed at 630 nm and 580 nm, respectively. Since conversions of these monomers were similar, butadiyne moieties are aligned in polymerizable stacks and the different spacings seemed to be caused by folding structure differences in substituents. We also prepared mixed crystals of 4BCMU and DO-4BCMU with mixing ratio of 3:7 by melt crystal growth. In this crystal, the layered-structure spacing was 2.31 nm, and their similar molecular structures may be responsive for mixed crystal formation with a new phase. However, it was strangely observed that absorption spectrum of the polymer from the mixed crystals corresponded to summation of the spectra of original polymers from 4BCMU and DO-4BCMU.

Synthesis and Optical Properties of Chiral Polydiacetylenes

Chiral diacetylenes featuring ester and urethane groups are readily prepared from amino acids and diynediols. The ability of the butadiyne moiety to undergo topotactic polymerization is dependent on both the length of the chain to the urethane group and the size of the amino acid. In some cases, the polymerization proceeds as well as the well-studied achiral parent compound, 4BCMU. The polymers form yellow solutions in good solvents where the chains adopt a random-coil configuration. Addition of a nonsolvent changes the solution color to red as the chains adopt a helical conformation.

Molecular Wires Comprising π-Extended Ethynyl- and Butadiynyl-2,5-Diphenyl-1,3,4-Oxadiazole Derivatives: Synthesis, Redox, Structural, and Optoelectronic Properties

2,5-Diphenyl-1,3,4-oxadiazole (OXD) derivatives with terminal ethynyl- (4a,b) and butadiynyl- (8a,b) substituents have been synthesized in high yields. 2-Methyl-3,5-hexadiyn-2-ol has not been exploited previously in the synthesis of terminal butadiynes. Crystals of 8a and 8b are remarkably stable to long-term storage under ambient conditions. The X-ray crystal structure of 8a reveals that the butadiyne moieties are spatially isolated by the aromatic moieties, which explains the high stability. Two series of derived pi-conjugated molecules, Donor-(C[triple bond]C)(n)-OXD (n = 1, 2) and OXD-(C[triple bond]C)(n)-Donor-(C[triple bond]C)(n)-OXD (n = 1) [Donor = tetrathiafulvalene (TTF), bithiophene, 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene, and triphenylamine], have been synthesized using Sonogashira reactions and characterized by X-ray crystallography, cyclic voltammetry, and optical absorption/emission spectroscopy. The electron-withdrawing effect of the OXD units is manifested by a positive shift of the donor oxidation waves in these systems: the butadiynylene spacer (n = 2) further shifts the first oxidation waves by 40-80 mV compared to analogues n = 1. The absorption spectra of TTF-OXD hybrids 10d and 11 are blue-shifted by 80 nm compared to the bithienyl-bridged derivative 10f and are similar to the butadiynyl-OXD building-block 8a, demonstrating that conjugation is disrupted by a neutral TTF unit. Solutions of the TTF-OXD and 9-(4,5-dimethyl-1,3-dithiol-2-ylidene)fluorene-OXD hybrids, 10d, 10g, 11, and 13, are only very weakly fluorescent due to quenching from the electron-donor moieties. In contrast, the triphenylamine-OXD hybrids 12a, 12b, 14a, and 14b are fluorescent; the PLQYs of the butadiynylene derivatives 14a and 14b are lower than those of the ethynylene-bridged analogues 12a and 12b.

1H NMR Investigation of High-Spin and Low-Spin Iron(III) meso-Ethynylporphyrins

The 1H NMR spectra of iron(III) 5-ethynyl-10,15,20-tri(p-tolyl)porphyrin [(ETrTP)Fe(III)X(n)], iron(III) 5-(phenylethynyl)-10,15,20-tri(p-tolyl)porphyrin [(PETrTP)Fe(III)X(n)], iron(III) 5-(phenylbutadiynyl)-10,15,20-tri(p-tolyl)porphyrin [(PBTrTP)Fe(III)X(n)], iron(III) 5,10,15,20-tetra(phenylethynyl)porphyrin [(TPEP)Fe(III)X(n)], iron(III) 1,4-bis-[10,15,20-tri(p-tolyl)porphyrin-5-yl]-1,3-butadiyne {[(TrTP)Fe(III)X(n)]2 B}, and 5,10,15-triphenylporphyrin [(TrPP)Fe(III)X(n)] have been studied to elucidate the impact of meso-ethynyl substitution on the electronic structure and spin density distribution of high-spin (X = Cl-, n = 1) and low-spin (X = CN-, n = 2) derivatives. The meso substituents, i.e., ethynyl, phenylethynyl, and phenylbutadiynyl, provided insight into the efficiency of spin density delocalization along structural elements that are typically applied to transmit electronic effects along multipart polyporphyrinic systems. The positive spin density localized at the meso-carbon of high-spin iron(III) ethynylporphyrins is effectively delocalized along the ethyne or butadiyne fragment as illustrated by the comparison of isotropic shifts of C(meso)-H and -CC-H determined for (TrPP)Fe(III)Cl (-82.6 ppm, 293 K) and (ETrTP)Fe(III)Cl (-49.5 ppm, 298 K). The replacement of the ethynyl hydrogen by phenyl or phenylethynyl provided evidence for the pi spin density distribution around the introduced phenyl ring. An analysis of the isotropic shifts for the low-spin bis-cyanide iron(III) porphyrins series reveals the analogous mechanism of spin density transfer. Treatment of high-spin [(TrTP)Fe(III)Cl]2 B with a base resulted in formation of the cyclic [(TrTP)Fe(III)OFe(III)(TrTP)B]2 complex linked by two mu-oxo bridges. (TPEP)H2 has been characterized by X-ray crystallography as a porphyrin dication where two molecules of trifluoroacetic acid associate with two coordinated trifluoroacetate anions. The X-ray structure of bis-tetrahydrofuran 1,4-bis[10,15,20-tri(p-tolyl)porphyrinatozinc(II)-5-yl]-1,3-butadiyne complex {[(TrTP)Zn(II)(THF)]2 B} reveals two parallel, non-coplanar [(TrTP)Zn(THF)] subunits linked by the linear butadiyne moiety.

Ketene Formation in Benzdiyne Chemistry: Ring Cleavage versus Wolff Rearrangement

In the chemistry toward generating benzdiyne from five benzenetetracarboxylic dianhydride derivatives, ketene formation was exclusively observed in the photolysis of difluorobenzenetetracarboxylic dianhydride in a nitrogen matrix at 13 K. Two ketenes were formed concomitantly with difluorobenzdiyne. These ketenes were identified on the basis of good agreement between the observed and calculated (B3LYP/6-31G level) IR spectra. Neither ketene contained the five-membered-ring moiety as cyclopentadienylideneketene, which is formed by Wolff rearrangement in the benzyne chemistry. The first generated ketene was assigned to a ketene with a cyclopropene moiety, and the second, to a ketene with a butadiyne moiety. The first generated ketene was a major product in the photolysis and was formed by cleavage of the bond connecting the ketene group and the C-F carbon and not the bond connecting the ketene group and the carbene moiety. Thus the structures of these ketenes indicated that a unprecedented ring cleavage, rather than Wolff rearrangement, is the dominant process in the benzdiyne chemistry.