Diyne Units Research Articles

Light-induced transformation of a supramolecular gel to a stronger covalent polymeric gel.

A polymerizable diacetylene gelator, containing urea and urethane groups, that congeals various non-polar solvents was synthesized. The gelator molecules self-assemble forming non-covalent polymers through intermolecular hydrogen bonding, as evidenced from FT-IR and concentration-dependent 1H NMR spectroscopy. The self-assembly positions the diyne units of adjacent molecules at proximity and in a geometry suitable for their topochemical polymerization. UV irradiation of the gel resulted in topochemical polymerization, transforming the non-covalent polymer to a covalent polymer, in situ, in the gel state. The polymerization was confirmed by characterizing the polydiacetylene (PDA) using UV-Vis and Raman spectroscopy. Time-dependent rheological studies revealed gradual strengthening of the gel with the duration of irradiation, suggesting that the degree of polymerization increases with the duration of irradiation. The PDA formed is a semiconductor, which might be useful for various applications.

Tetracopper σ-Bound µ-Acetylide and -Diyne Units Stabilized by a Naphthyridine-based Dinucleating Ligand.

Reactions of a dicopper(I) tert-butoxide complex with alkynes possessing boryl or silyl capping groups resulted in formation of unprecedented tetracopper(I) µ-acetylide/diyne complexes that were characterized by NMR and UV-Vis spectroscopy, mass spectrometry and single-crystal X-ray diffraction. These compounds possess an unusual µ4-η1:η1:η1:η1 coordination mode for the bridging organic fragment, enforced by the rigid and dinucleating nature of the ligand utilized. Thus, the central π system remains unperturbed and accessible for subsequent reactivity and modification. This has been corroborated by addition of a fifth copper atom, giving rise to a pentacopper acetylide complex. This work may provide a new approach by which metal-metal cooperativity can be exploited in the transformation of acetylide and diyne groups to a variety of substrates, or as a starting point for the controlled synthesis of copper(I) alkyne-containing clusters.

Tetracopper σ‐Bound μ‐Acetylide and ‐Diyne Units Stabilized by a Naphthyridine‐based Dinucleating Ligand

AbstractReactions of a dicopper(I) tert‐butoxide complex with alkynes possessing boryl or silyl capping groups resulted in formation of unprecedented tetracopper(I) μ‐acetylide/diyne complexes that were characterized by NMR and UV/Vis spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction. These compounds possess an unusual μ4‐η1:η1:η1:η1 coordination mode for the bridging organic fragment, enforced by the rigid and dinucleating nature of the ligand utilized. Thus, the central π system remains unperturbed and accessible for subsequent reactivity and modification. This has been corroborated by addition of a fifth copper atom, giving rise to a pentacopper acetylide complex. This work may provide a new approach by which metal‐metal cooperativity can be exploited in the transformation of acetylide and diyne groups to a variety of substrates, or as a starting point for the controlled synthesis of copper(I) alkyne‐containing clusters.

Gold-Catalyzed Annulation of 1,8-Dialkynylnaphthalenes: Synthesis and Photoelectric Properties of Indenophenalene-Based Derivatives.

A simple gold‐catalyzed annulation of 1,8‐dialkynylnaphthalenes utilizing a cationic gold catalyst was developed. Such a peri‐position of two alkynyl substituents has not been studied in gold catalysis before. Dependent on the substrate, the reactions either follow a mechanism involving vinyl cation intermediates or involve a dual gold catalysis mechanism which in an initial 6‐endo‐dig‐cyclization generates gold(I) vinylidene intermediates that are able to insert into C−H bonds. Indenophenalene derivatives were obtained in moderate to high yields. In addition, the bidirectional gold‐catalyzed annulation of tetraynes provided even larger conjugated π‐systems. The optoelectronic properties of the products were also investigated.

Building Double Branch Dyes with Acetylenic Bonds: An Effective Strategy to Enhance the Efficiency of Dye‐Sensitized Solar Cells

Double branch (DB) dyes could reduce intermolecular interactions and realize good photovoltaic performances. Herein, symmetric DB dyes (FSDD‐1 and FSDD‐2) featuring with one and two acetylenic bonds as the isolation groups are reported. The corresponding single branch (SB) dye FSSD‐EH is synthesized for comparison. For the adsorption spectra, bathochromic shifts and higher ε are observed for DB dyes FSDD‐1 and FSDD‐2 compared with SB dye FSSD‐EH, which suggests better light‐harvesting capabilities for the DB dyes. Dye‐sensitized solar cells (DSSCs) sensitized by DB dyes FSDD‐1 and FSDD‐2 exhibit significant increases for the Jsc and Voc compared with SB dye FSSD‐EH, so much better η are achieved by the DB dyes (5.34, 7.14, and 2.46% for FSDD‐1, FSDD‐2, and FSSD‐EH, respectively). FSDD‐2 with a diyne unit exhibits higher η compared with FSDD‐1 with an yne unit as the isolation groups. The research shows that a much better photovoltaic performance of DSSCs can be achieved after connecting two dye molecules to be a DB dye by adopting acetylenic bonds as the isolation group. A longer distance between the two branches realized by a diyne unit is beneficial and effective to achieve better photovoltaic performance.

Site-selective [2 + 2 + n] cycloadditions for rapid, scalable access to alkynylated polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are attractive synthetic building blocks for more complex conjugated nanocarbons, but their use for this purpose requires appreciable quantities of a PAH with reactive functional groups. Despite tremendous recent advances, most synthetic methods cannot satisfy these demands. Here we present a general and scalable [2 + 2 + n] (n = 1 or 2) cycloaddition strategy to access PAHs that are decorated with synthetically versatile alkynyl groups and its application to seven structurally diverse PAH ring systems (thirteen new alkynylated PAHs in total). The critical discovery is the site-selectivity of an Ir-catalyzed [2 + 2 + 2] cycloaddition, which preferentially cyclizes tethered diyne units with preservation of other (peripheral) alkynyl groups. The potential for generalization of the site-selectivity to other [2 + 2 + n] reactions is demonstrated by identification of a Cp2Zr-mediated [2 + 2 + 1]/metallacycle transfer sequence for synthesis of an alkynylated, selenophene-annulated PAH. The new PAHs are excellent synthons for macrocyclic conjugated nanocarbons. As a proof of concept, four were subjected to alkyne metathesis catalysis to afford large, PAH-containing arylene ethylene macrocycles, which possess a range of cavity sizes reaching well into the nanometer regime. Notably, these high-yielding macrocyclizations establish that synthetically convenient pentynyl groups can be effective for metathesis since the 4-octyne byproduct is sequestered by 5 Å MS. Most importantly, this work is a demonstration of how site-selective reactions can be harnessed to rapidly build up structural complexity in a practical, scalable fashion.

Skeleton Engineering of Homocoupled Conjugated Microporous Polymers for Highly Efficient Uranium Capture via Synergistic Coordination.

Developing efficient adsorbents for uranium enrichment is of great significance for resource sustainability and environmental safety. This study presents a facile and adaptable post-synthetic strategy to prepare highly efficient uranium adsorbents via engineering the π-conjugated skeletons of homocoupled conjugated microporous polymers (HCMPs). Taking advantage of the diyne units in the π-conjugated skeletons, bis-amidoxime uranophiles, one of the state-of-the-art ligands of uranyl ions, were introduced to the frameworks of HCMPs. The functionalized HCMPs preserved the interconnected 3D microporous networks and rigid conjugated skeletons with abundant bis-amidoxime ligands uniformly distributed in the pore channels. Such structural advantages of the adsorbents afforded very fast adsorption kinetics within 15 min to reach the equilibrium and high capacity of uranium (450 mg/g). Moreover, DFT calculation suggests a synergistic coordination as the most energetically favored coordination mode of the uranyl/bis-amidoxime complexes. This study contributes new insights into the underlying mechanism responsible for the highly efficient adsorption ability of the bis-amidoxime-functionalized HCMPs toward uranium. Meanwhile, the synthetic methodology established here could be extended to task-specific design and skeleton engineering of more functional HCMPs for broadened applications.

From Noncovalent Chalcogen-Chalcogen Interactions to Supramolecular Aggregates: Experiments and Calculations.

This review considers noncovalent bonds between divalent chalcogen centers. In the first part we present X-ray data taken from the solid state structures of dimethyl- and diphenyl-dichalcogenides as well as oligoalkynes kept by alkyl-sulfur, -selenium, and -tellurium groups. Furthermore, we analyzed the solid state structures of medium sized (12-24 ring size) selenium coronands and medium to large rings with alkyne and alkene units between two chalcogen centers. The crystal structures of the cyclic structures revealed columnar stacks with close contacts between neighboring rings via noncovalent interactions between the chalcogen centers. To get larger space within the cavities, rings with diyne units between the chalcogen centers were used. These molecules showed channel-like structures in the solid state. The flexibility of the rings permits inclusion of guest molecules such as five-membered heterocycles and aromatic six-membered rings. In the second part we discuss the results of quantum chemical calculations. To treat properly the noncovalent bonding between chalcogens, we use diffuse augmented split valence basis sets in combination with electron correlation methods. Our model substances were 16 dimers consisting of two Me-X-Me (X = O, S, Se, Te) pairs and dimers of Me-X-Me/Me-X-CN (X = O, S, Se, Te) pairs. The calculations show the anticipated increase of the interaction energy from (Me-O-Me)2 (-2.15 kcal/mol) to (Me-O-Me/Me-Te-CN) (-6.59 kcal/mol). An analysis by the NBO method reveals that in the case of the chalcogen centers O and S the hydrogen bridges between the molecules dominate. However, in the case of Se and Te the major bonding between the pairs originates from dispersion forces between the chalcogen centers. It varies between -1.7 and -4.0 kcal/mol.

Expanded Helicenes: A General Synthetic Strategy and Remarkable Supramolecular and Solid-State Behavior.

A divergent synthetic strategy allowed access to several members of a new class of helicenes, the "expanded helicenes", which are composed of alternating linearly and angularly fused rings. The strategy is based on a three-fold, partially intermolecular [2+2+n] (n = 1 or 2) cycloaddition with substrates containing three diyne units. Investigation of aggregation behavior, both in solution and in the solid state, revealed that one of these compounds forms an unusual homochiral, π-stacked dimer via an equilibrium that is slow on the NMR time scale. The versatility of the method was harnessed to access a selenophene-annulated expanded helicene that, in contrast to its benzannulated analogue, exhibits long-range π-stacking in the solid state. The new helicenes possess low racemization barriers, as demonstrated by dynamic 1H NMR spectroscopy.

Molecular Engineering of Efficient Organic Sensitizers Containing Diyne-Bridge for Dye-Sensitized Solar Cells

Diyne unit containing organic dyes coded as FSD105 and FSD106 were designed and synthesized to investigate their light harvesting capabilities and the DSSC performances. Through tuning the geometrical structures of dye molecules by introducing an extra ethynylene, FSD105 and FSD106 showed an obviously improved coplanar geometry, and thus the significantly bathochromic shifted absorption spectra, IPCE spectra and larger Γ values, leading to the enhancement of Jsc which guaranteed the highest η (3.82%) for FSD106-based DSSC. In order to avoid the dye aggregation, CHCl3/EtOH was adopted as the sensitizing solvents instead of CHCl3 only or CDCA as coadsorbent was added to reduce the Γ value of FSD106-based DSSC. As a result, the Jsc and the η value increased significantly. Finally, FSD106/CDCA-based DSSC showed the highest η value (4.76%), which is 1.53-fold as the previous reported FSD101-based DSSC (3.12%) by introducing an extra ethynylene to improve the molecular coplanarity.

Novel diyne-bridged dyes for efficient dye-sensitized solar cells

Three new metal free organic dyes (FSD101-103) were synthesized to investigate the influence of diyne unit on dye molecules. FSD101 and FSD102 with diyne unit and FSD103 with monoyne unit were applied as sensitizers in the dye-sensitized solar cells (DSSCs). The optical and electrochemical properties, theoretical studies, and photovoltaic parameters of DSSCs sensitized by these dyes were systematically investigated. By replacing the monoyne unit with a diyne unit, FSD101 exhibited broader absorption spectrum, lower IP, higher EA, lower band gap energy, higher oscillator strength, more efficient electron injection ability, broader IPCE response range and higher τe in comparison with FSD103. Hence, DSSC sensitized by FSD101 showed higher Jsc and Voc values, and demonstrated a power conversion efficiency of 3.12%, about 2-fold as that of FSD103 (1.55%). FSD102 showed similar results as FSD101, with a power conversion efficiency of 2.98%, despite a stronger electron withdraw cyanoacrylic acid group was introduced. This may be due to the lower efficiency of the electron injection from dye to TiO2 and lower τe of FSD102 than that of FSD101. These results indicate that the performance of DSSCs can be significantly improved by introducing a diyne unit into this type of organic dyes.

Synthesis and Properties of Rhomboidal Macrocyclic Subunits of Graphdiyne-Like Nanoribbons.

Rhomboidal macrocyclic subunits of graphdiyne-like nanoribbon (GDNR) bearing both alkyne and diyne units, allowing for multichannel π-conjugation, were synthesized using an oxidative Glaser-type ring closing reaction. These subunits, called the "meshes" of the nanoribbon, possess phenyl groups with decyloxy solubilizing chains on each corner. The yields of the ring closing reaction highly depend on the metal (Cu or Pd) catalyst used for the macrocyclization step. Increasing the width of the meshes from one macrocycle to two fused macrocycles resulted in a decrease of the bandgap by 0.23 eV as shown by optical spectroscopy. The optimized geometries of the meshes alongside their HOMO and LUMO orbitals were calculated using DFT calculations at the B3LYP/6-31+G** level of theory. The results showed a nearly planar conformation for both meshes with HOMO and LUMO orbitals entirely delocalized over the molecules.

Synthesis of cryptands with di-yne units via acetylenic homocoupling reactions of C3 tripodands

Cryptands with di-yne units were obtained in good yields by the acetylenic homocoupling reaction of tripodands possesing terminal ethynyl units on the pendant arms. The coupling reactions also led to isomeric bismacrocylic compounds, and the shifting of the process toward the products of intramolecular or intermolecular coupling reactions was influenced by the structure of tripodands and by the coupling reaction conditions.

Supramolecular Construction of Optoelectronic Biomaterials

Peptide self-assembly is a powerful method to create functional nanoscale materials such as optoelectronically relevant organic nanostructures. The enormous potential that may come from bringing π-conjugated electronic function into biological environments is poised to impact cell and tissue engineering, biosensors, and related biomedical applications. However, very little synthetic guidance is available with respect to uniting these two different materials sets in a generally applicable manner. In this Account, I describe my group's work to synthesize and assemble peptidic nanostructures built around organic electronic elements. The Account begins with a very brief background to the area of supramolecular electronics, followed by a description of areas where these nanomaterials could be useful in biology. I then discuss the synthetic approaches that we utilized to embed a variety of π-electron units directly within peptide backbones. A key supramolecular challenge with respect to subsequent self-assembly of these new molecules is balancing electrostatic contributions within the resulting nanomaterials, because the suitable geometries for stabilizing peptide assemblies may not necessarily correspond to those suitable for maximizing intermolecular π-electron interactions. Regardless of the respective magnitudes of these two major influences, the assembly paradigm is fairly robust. Variation of the π-electron units and the peptide sequences that make up the "peptide-π-peptide" triblock molecules consistently leads to fairly uniform tape-like nanostructures that maintain strong electronic coupling among the component π-electron units. We explored a diverse range of π-electron units spanning fluorescent oligo(phenylene vinylene)s, electron-accepting rylene diimides, and hole-transporting oligothiophenes. I then describe the characterization of the nanomaterials that form after molecular self-assembly in order to understand their internal structures, electronic interactions, and morphologies as existing within self-supporting hydrogel matrices. I also describe how a facile shearing process provided globally aligned macroscopic collections of one-dimensional electronic fibrils in hydrogel matrices. These general assembly processes influence intermolecular π-stacking among the embedded chromophores, and the assemblies themselves can facilitate the covalent cross-linking and polymerization (for example, of reactive diyne units). The latter offers an exciting possibility to create peptidic nanostructures comprised of single polymer chains. Finally, I discuss electronic properties as manifested in the interactions of transition dipoles within the nanomaterials and electrical properties resulting from field-effect gating. The ability to tune the observable electrical properties of the nanostructures externally will allow for their transition to in vitro or in vivo platforms as a powerful new approach to regulating biological interactions at the nanoscale.

Target cum flexibility: synthesis of C(3 ′)-spiroannulated nucleosides

We report a simple strategy for the synthesis of a collection of C(3′)-spirodihydroisobenzo-furannulated nucleosides featuring a [2+2+2]-cyclotrimerization as the key reaction. The cyclotrimerization reactions are facile with the unprotected nucleosides having a diyne unit. When both alkynes of the diyne are terminal, the regioselectivity is poor. However, when one of the terminal alkynes is additionally substituted, the cyclotrimerizations are highly diastereoselective. Since the key bicycloannulation is the final step, this strategy provides flexibility in terms of the alkynes and is thus amenable for the synthesis of a focussed small molecule library.

Total synthesis of panaxytriol and panaxydiol

The enantioselective total synthesis of the diyne containing natural products panaxytriol and (3 S,10 R)-panaxydiol from l-tartaric acid is reported. Key steps in the synthesis include the elaboration of a γ-hydroxy amide derived from tartaric acid to the required alkyne and the formation of the desired diyne unit by a Cadiot–Chodkiewicz coupling.

Tetris in monolayers: patterned self-assembly using side chain shape

The "kinked" shapes of conjugated alkadiynes constrain chain packing in monolayers on HOPG. Centrally located diyne units permit assembly of 1,5-bis(alkadiyne)anthracene monolayers. Off-center diynes inhibit self-assembly. Shape matched pairs of off-center diyne chains direct self-assembly of compositionally patterned, two component monolayers.

Synthesis, structure, and optical properties of an alternating calix[4]arene‐based meta‐linked phenylene ethynylene copolymer

AbstractNovel alternating copolymers comprising bis‐ calix[4]arene‐p‐phenylene ethynylene and m‐phenylene ethynylene units (CALIX‐m‐PPE) were synthesized using the Sonogashira‐Hagihara cross‐coupling polymerization. Good isolated yields (60–80%) were achieved for the polymers that show Mn ranging from 1.4 × 104 to 5.1 × 104 gmol−1 (gel permeation chromatography analysis), depending on specific polymerization conditions. The structural analysis of CALIX‐m‐PPE was performed by 1H, 13C, 13C–1H heteronuclear single quantum correlation (HSQC), 13C–1H heteronuclear multiple bond correlation (HMBC), correlation spectroscopy (COSY), and nuclear overhauser effect spectroscopy (NOESY) in addition to Fourier transform‐Infrared spectroscopy and microanalysis allowing its full characterization. Depending on the reaction setup, variable amounts (16–45%) of diyne units were found in polymers although their photophysical properties are essentially the same. It is demonstrated that CALIX‐m‐PPE does not form ground‐ or excited‐state interchain interactions owing to the highly crowded environment of the main‐chain imparted by both calix[4]arene side units which behave as insulators inhibiting main‐chain π–π staking. It was also found that the luminescent properties of CALIX‐m‐PPE are markedly different from those of an all‐p‐linked phenylene ethynylene copolymer (CALIX‐p‐PPE) previously reported. The unexpected appearance of a low‐energy emission band at 426 nm, in addition to the locally excited‐state emission (365 nm), together with a quite low fluorescence quantum yield (ϕ = 0.02) and a double‐exponential decay dynamics led to the formulation of an intramolecular exciplex as the new emissive species. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Topological Polymerization of tert-Butylcalix[4]arenes Containing Diynes

The new 25,26,27,28-tetra(8-hydroxylocta-2,4-diynyl)-tert-butylcalix[4]arene was synthesized in good yield from copper-catalyzed coupling reaction of 25,26,27,28-tetra(2-propynyl)-tert-butylcalix[4]arene with 5-iodo-4-pentynol in pyrrolidine. The hydroxyl end groups were converted to urethane groups through addition to alkyl or phenyl isocyanate. Di- and trisubstituted tert-butylcalix[4]arene analogs were also synthesized through the same approach. The solid-state photopolymerization study revealed that only the calix[4]arene derivatives containing four diyne units with alkyl urethane groups were substantially polymerized upon exposure to UV or gamma irradiation to give polydiacetylenes containing calix[4]arene. The visible absorption band at 350−600 nm and the Raman signals around 1500 and 2100 cm-1 characterized the ene−yne conjugation formed through the topological 1,4-addition polymerization of the diyne units.

Facile Reductive Coupling Reaction of Bis(ruthenocenylethynyl)titanocene Complexes via Visible Light-Activation of the Ruthenocenyl Terminal

Abstract The irradiation of (η5-C5H4R)2Ti(C≡CRc)2 (R = Me, SiMe3 (= TMS); Rc = ruthenocenyl) at the band assignable to CT from Rc to Ti in the presence of equimolar amounts of RcC≡CH and MeO2CC≡CCO2Me smoothly gave titanacyclic complexes (η5-C5H4R)2Ti{–C(Rc)=C(C≡CRc)–CH=C(Rc)–} and (η5-C5H4TMS)2Ti{–C(C≡CRc)=C(Rc)–C(OMe)(C≡CCO2Me)–O–}, respectively, two of which were structurally characterized. The formation of these complexes has been explained by the extremely easy reductive coupling in (η5-C5H4R)2Ti(C≡CRc)2, brought about by photo-excitation at the Rc group, followed by metallacycle formation that involves the resulting diyne unit and the externally added alkynes.