Diphenylacetylene Derivatives Research Articles

Fabrication of Fe3O4@AMNA-CuBr Nanocomposite as a Highly Efficient and Reusable Heterogenous Catalyst for Synthesis of Highly Substituted Oxazoles

Research on synthetic methods for the preparation of oxazoles is an important issue among synthetic chemists because oxazole derivatives are structural subunits of various natural active products and are valuable synthetic and pharmaceutical precursors. In this research work, we constructed CuBr supported on surface of magnetic Fe3O4 nanoparticles modified with 6-(aminomethyl)nicotinic acid [Fe3O4@AMNA-CuBr nanocomposite] and evaluated its catalytic activity for the preparation of highly substituted oxazoles through one-pot three-component reactions of diphenylacetylene derivatives with aryl nitriles and water in PEG as the solvent. The results shown that the Fe3O4@AMNA-CuBr catalyst was used 8 times without significant decrease in catalytic activity. XRD and TEM analysis confirmed that the structure and morphology that the Fe3O4@AMNA-CuBr catalyst did not change after 8 runs.

Effects of Two Electron-Donating and/or -Withdrawing Substituents on Two-Photon Absorption for Diphenylacetylene Derivatives.

Two-photon absorption for diphenylacetylene (DPA) derivatives with two substituents (-OMe and/or -NO2) at the 4,4'-position was investigated experimentally and theoretically. The two-photon absorption spectra and the two-photon absorption cross-sections σ(2) for DPA derivatives were obtained by optical-probing photoacoustic spectroscopy (OPPAS). The simulated two-photon absorption spectra of the DPA derivatives, obtained with the time-dependent density functional theory within the Tamm-Dancoff approximation, agreed well with the experimental ones. The mechanisms for enhancement of the σ(2) for centrosymmetric and non-centrosymmetric DPA derivatives were found to be different. The large σ(2) for centrosymmetric molecules (DPA-OMeOMe and DPA-NO2NO2) results from the magnitude of the transition dipole moment, while for non-centrosymmetric molecules (DPA-OMeNO2), it is enhanced by the smaller detuning energy. Information on two-photon absorption properties of DPA derivatives obtained in this study will be important for the molecular design of two-photon absorption materials.

Low-Valent Molybdenum PNP Pincer Complexes as Catalysts for the Semihydrogenation of Alkynes.

Low-valent molybdenum PNP pincer complexes were studied as catalysts for the semihydrogenation of alkynes. For that purpose, tBu-substituted PNP complexes PNPtBuMo(CO)2 (6a) and PNPtBuMo(CO)3 (6c) and the NNP complex NNPiPrMo(CO)2(PPh3) ((rac)-7) were synthesized and characterized. By utilizing the cyclohexyl-substituted complex PNPCyMo(CO)2(CH3CN) (5a), several diphenylacetylene derivatives are transformed to the corresponding (Z)-alkenes with good to very good diastereoselectivities (up to 91:9). Mechanistic experiments indicate an outer-sphere mechanism including metal–ligand cooperativity.

Long‐Range Charge Transportation Induced Organic Host–Guest Dual Color Long Persistent Luminescence

AbstractLong persistent luminescence (LPL) can store light energy in excited states and gradually release it as light. Organic host–guest systems provide a good platform for LPL, and single‐color LPL is often achieved while multicolor LPL is challengeable. Here host–guest supramolecular complexes are presented with dual LPL emissions: thermally activated delayed fluorescence (TADF) (≥100 ms) and room temperature phosphorescence (RTP). A space charge transfer from α‐cyclodextrin to diphenylacetylene (DPA) with long‐range transportation (2.32 mm) carrier along DPA strand in the supramolecular complexes is attributed to generate the TADF and RTP. Fortunately, these supramolecular complexes are readily fabricated from α‐cyclodextrin and DPA or DPA derivatives. The gradient color is observed after removing UV excitation. Furthermore, the hydrophobic property inside α‐cyclodextrin makes the LPL appear by water shedding and disappear by organic solvent infiltration, showing the character of a “switch.” This host–guest space charge transfer strategy paves a way to design LPL materials.

A Substituent Effect on Two-Photon Absorption of Diphenylacetylene Derivatives with an Electron-Donating/Withdrawing Group.

Two-photon absorption for diphenylacetylene derivatives with an electron-donating (ED) or electron-withdrawing (EW) group (DPA-Rs) was investigated by high-sensitivity optical-probing photoacoustic spectroscopy. Two-photon absorption spectra and two-photon absorption cross sections σ(2) for DPA-Rs were successfully obtained. Two-photon absorption spectra of DPA-Rs with stronger ED or EW groups display more significant red-shifts and larger σ(2) values. Simulated two-photon absorption spectra, using time-dependent density functional theory within the Tamm-Dancoff approximation, compared well with the experimental spectra. Based on the three-state model, the substituent effect on the two-photon absorption for DPA-Rs was expected to manifest in the transition dipole moments and detuning energies. Information obtained from investigating the monosubstituent effect on two-photon absorption of DPA is critical for an improved understanding of two-photon absorption.

Catalytic Dimerization of Alkynes via C–H Bond Cleavage by a Platinum–Silylene Complex

The cyclodimerization of diphenylacetylene derivatives catalyzed by a platinum–silylene complex is reported. The reaction proceeds via the cleavage of a carbon–hydrogen bond at the position ortho to an alkynyl group, and no additives are needed. Platinum complexes bearing other common ligands, such as phosphines and NHCs, failed to promote this reaction, highlighting the utility of the silylene ligand in this reaction.

Cellular internalization mechanism of novel Raman probes designed for plant cells.

Diphenylacetylene derivatives containing different polymeric components, poly(l-lysine) (pLys) or tetra(ethylene glycol) (TEG) were designed as novel Raman imaging probes with high Raman sensitivity and low cytotoxicity in living plant cells. The pLys-conjugated probe is internalized via an endocytosis-dependent pathway, whereas TEG-conjugated probe most likely induces direct penetration into the plant cells.

Determination of Hyperfine Coupling Constants of Fluorinated Diphenylacetylene Radical Anions by Magnetic Field-Affected Reaction Yield Spectroscopy.

Magnetic field-affected reaction yield (MARY) spectroscopy is a spin chemistry technique for detecting short-lived radical ions. Having sensitivity to transient species with lifetimes as short as nanoseconds, MARY spectroscopy usually does not provide detailed information on their magnetic resonance parameters, except for simple systems with equivalent magnetic nuclei. In this work, the radical anions of two fluorinated diphenylacetylene derivatives with nonequivalent magnetic nuclei and unknown hyperfine coupling constants ( AHF) were investigated by MARY spectroscopy. The MARY spectra were found to be resolved and have resonance lines in nonzero magnetic fields, which are determined by the AHF values. Simple relationships between the positions of resonance MARY lines and the AHF values were established from the analysis of the different Hamiltonian block contributions to the MARY spectrum. The obtained experimental AHF values are in agreement with the results of quantum chemical calculations at the density functional theory level.

NH4I/EtOCS2K promoted synthesis of substituted benzils from diphenylacetylene derivatives

A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH4I/EtOCS2K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH4I promoted EtOCS2K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.

Photophysical and theoretical studies of diphenylacetylene derivatives with restricted rotation

Diphenylacetylene derivatives containing electron-donor (amino) and electron-acceptor (ester) groups in 2,2′ or 3,2′ positions in phenyl rings were synthesized to study the effects of intramolecular charge transfer and stiffening of the conformation by intramolecular hydrogen bond on the photophysical properties. Additionally, the derivatives with and without a steric hindrance were studied to determine the effect of conformational freedom on photophysical properties. The persistence of the intramolecular hydrogen bond and the corresponding twisted conformations as well as the conformational flexibility were also established by DFT calculations.

Synthesis, Structure, and Reactivity of a Cylinder-Shaped Cyclo[12]orthophenylene[6]ethynylene: Toward the Synthesis of Zigzag Carbon Nanobelts.

Benzannulated cyclacenes (BCs) have been proposed as stable zigzag carbon nanobelts. Density functional theory (DFT) calculations revealed a closed-shell ground state for [12]BC, whereas an open-shell ground state was suggested for [12]cyclacene. The calculated strain energy and frontier molecular orbital energies of [12]BC also implied high stability. An unstrained macrocycle 1, consisting of orthophenylene and ethynylene moieties, was designed as a potential precursor for [12]BC and synthesized by sequential Suzuki-Miyaura cross-coupling of diphenylacetylene derivatives. While the conversion of 1 into [12]BC is still under investigation, an unexpected rearrangement of the triene moieties in 1, affording a tribenzo[f,k,m]tetraphene structure, was discovered during the screening of reaction conditions. An attempt was made to rationalize this result by proposing a plausible reaction mechanism that proceeds via intermediates containing cyclobutadiene or Dewar benzene moieties. The proposed mechanism is partially supported by DFT calculations.

Direct Observation of Cascade of Photoinduced Ultrafast Intramolecular Charge Transfer Dynamics in Diphenyl Acetylene Derivatives: Via Solvation and Intramolecular Relaxation.

Interaction of light with electron donor-acceptor π-conjugated systems leading to intramolecular charge transfer (ICT) plays an essential role in transformation of light energy. Here the cascade of photoinduced ICT processes is directly observed by investigating the excited state relaxation dynamics of cyano and mono/di methoxy substituted diphenyl acetylene derivatives using femtosecond pump-probe spectroscopy and nanosecond laser flash photolysis. The femtosecond transient absorption spectra of the chromophores upon ultrafast excitation reveal the dynamics of intermediates involved in transition from initially populated Frank-Condon state to local excited state (LE). It also provides the dynamic details of the transition from the LE to the charge transfer state yielding the formation of the radical ions. Finally, the charge transfer state decays to the triplet state by geminate charge recombination. The latter dynamics are observed in the nanosecond transient absorption spectra. It is found that excited state relaxation pathways are controlled by different stages of solvation and intramolecular relaxation depending on the solvent polarity. The twisted ICT state is more stabilized (978 ps) in acetonitrile than cyclohexane where major components of transient absorption originate from the S1 state.

Influence of an electron-acceptor substituent type on the photophysical properties of unsymmetrically substituted diphenylacetylene

Abstract Unsymmetrically substituted diphenylacetylene derivatives containing a different type of an electron-acceptor substituent were synthetized and studied using spectroscopic methods in order to establish the influence of electron affinity of substituent on the photo physics of donor-acceptor pairs. Spectral and photophysical properties were studied in 14 solvents (non-polar, polar aprotic and protic). Influence of solvent properties on spectral and photophysical properties of studied compounds was analyzed using Catalan multi-parameter solvent scale. The change of the excited state dipole moment was estimated based on Bilot-Kawski theory.

Experimental and theoretical studies of spectroscopic properties of simple symmetrically substituted diphenylbuta-1,3-diyne derivatives.

A series of symmetrically substituted diphenylbuta-1,3-diyne (DPB) derivatives possessing electron-donating (N,N-dimethylamino or methoxy) or electron-accepting (nitrile, ester or aldehyde) groups have been prepared and studied with emphasis on their spectral and photophysical properties. The photophysical characteristics of these compounds have been studied in relation to their structures and influence of solvents or temperature. The observed spectral and photophysical properties are explained with the help of potential energy maps in the ground and excited states obtained from density functional theory (DFT, B3LYP, def2TZVP basis set) calculations. The structure-property relationship of all of the compounds is discussed and compared with appropriate diphenylacetylene derivatives.

Crystallization-Induced Emission Enhancement of a Simple Tolane-Based Mesogenic Luminogen

The photophysical properties of a diphenylacetylene derivative (FOEB) were investigated. The fluorescence quantum efficiency (ΦF, %) of FOEB changes from moderate (49%) to low (9%) and to evidently enhanced (60%) in dilute solution, amorphous solid, and crystal state, respectively. This is a typical phenomenon of crystallization-induced emission enhancement (CIEE). The diphenylacetylene luminogen can be viewed as a propeller-like molecule with two blades (phenyl groups). In solution, the intramolecular rotations of the two blades around the ethynyl unit are activated and partially dissipate the energy in the photoexcited state, thereby leading to emission quenching. Consequently, FOEB exhibits moderate ΦF in solution. In amorphous solid, the intramolecular rotations are restricted, and a higher ΦF could be expected. But in fact, the strong π–π interactions between the luminogens cause heavier emission quenching, and the ΦF of the molecular aggregates is as low as 9%. In the single crystal, as the crystall...

Facile Synthesis and Phase Behaviors of Monofunctionalized Hexa-peri-hexabenzocoronenes

Five different kinds of monofunctionalized hexa-peri-hexabenzocoronenes (HBCs) are synthesized by loading dialkyl-diphenylacetylenes and asymmetric diphenylacetylene derivatives at the same time. This method shortens the synthetic route by half, with four fewer steps compared with the commonly used approach. In addition, this method is more economic and environmentally friendly. The self-assembling properties of the molecules are greatly influenced by the substituted alkyl side chains. From the short linear hexyl chain (C6) to the longer n-dodecyl (C12) chain and then to the branched alkyl chain (C10,6), the transition temperature from the crystalline phase to the liquid crystalline (LC) phase and that from the LC phase to the isotropic (Iso) state both decrease. Furthermore, the ester group far away from the aromatic core and its length are also important variables to control the phase behaviors of the molecules. The typical long-range ordered hexagonal lattice (Colh phase) is found for all the monofunctionalized molecules in their LC states.

Two-dimensional bricklayer arrangements of tolans using halogen bonding interactions.

Diphenylacetylene (tolan) derivatives with self-complementary aryl halides and halogen bond-accepting nitriles form 2D bricklayer packing motifs when halogen bonding occurs. When halogen bonding is absent, as occurred with fluorinated aryl bromides, the molecules adopt other packing motifs. These results suggest halogen bonding is potentially useful for producing rarely observed 2D bricklayer motifs in organic semiconductors.

Transformation of photophysical properties from solution to solid state in alkoxy-cyano-diphenylacetylene molecules.

Detailed photophysical properties of cyano and mono (MA)/bis alkoxy (DA) substituted diphenylacetylene moieties with different alkyl chain lengths (methyl (1), octyl (8) and dodecyl (12)) were investigated in solution and the solid state in an effort to determine the effect of self-aggregation on these properties. The solvated molecules showed a minimal bathochromic shift with an increase of solvent polarity in their absorption spectra, whereas a significant shift was observed in the emission spectra. This could be attributed to the relatively low change in dipole moment between ground and Franck-Condon excited states and luminescence arising from the intramolecular charge transfer state with a dipole moment significantly higher than that of the ground state. In solid state the emission quantum yields of these materials were significantly higher than in solution. For DA1, polymorphic materials with distinct photophysical properties were obtained. The DA1 materials obtained by fast precipitation (DA1) showed broad fluorescence with peaks at 398, 467 and 535 nm upon excitation at different wavelengths. Detailed analysis of absorption, emission and excitation spectra and lifetime experiments indicated that these peaks could be attributed to the monomer, J- and H-type aggregates respectively. Whereas the crystals obtained by slow crystallization (DA1C) showed only one emission peak at around 396 nm attributed to the monomer. This is supported by the single crystal X-ray structure which consists of a monomer molecule having minimal interaction with nearest neighbour molecules.

Experimental and theoretical studies of the spectroscopic properties of simple symmetrically substituted diphenylacetylene derivatives

A series of symmetrically substituted diphenylacetylene derivatives possessing electron-donating or electron-accepting character were prepared and studied with respect to their spectral and photophysical properties.

Synthesis, biological evaluation and molecular docking studies of benzyloxyacetohydroxamic acids as LpxC inhibitors

The inhibition of the UDP-3-O-[(R)-3-hydroxymyristoyl]-N-acetylglucosamine deacetylase (LpxC) represents a promising strategy to combat infections caused by multidrug-resistant Gram-negative bacteria. In order to elucidate the functional groups being important for the inhibition of LpxC, the structure of our previously reported hydroxamic acid 4 should be systematically varied. Therefore, a series of benzyloxyacetohydroxamic acids was prepared, of which the diphenylacetylene derivatives 28 (Ki=95nM) and 21 (Ki=66nM) were the most potent inhibitors of Escherichia coli LpxC. These compounds could be synthesized in a stereoselective manner employing a Sharpless asymmetric dihydroxylation and a Sonogashira coupling in the key steps. The obtained structure–activity relationships could be rationalized by molecular docking studies.