Search

Tautomerism is an interesting phenomenon that allows different properties to coexist in the same molecule. However, the understanding of tautomerism of large antiaromatic skeletons is very limited. We report herein the intriguing tautomerism behaviors of a new hexazapentacene derivative, named DHHAP. In solution, DHHAP exists as a mixture of benzenoid and quinonoid tautomers in a rough ratio of 1 : 1. DFT calulations reveal that DHHAP is slightly more stable than its 4n + 2π hexazapentacene counterpart although it has 4n π electrons. DHHAP exhibits different halochromic behaviors upon addition of strong and mild acids. Despite multiple protonation possibilities, careful NMR investigation revealed that only one di-protonation process occurs at symmetrical sites on the quinonoid structure, which is attributed to electrostatic potential-induced protonation regioselectivity. Femtosecond transient absorption (fs-TA) spectroscopy revealed different excited state dynamics of DHHAP-related species. Deep understanding of the tautomerism and aromaticity of dihydrohexazapentacene may pave a new way for the design of stable 4n π heteroacenes towards novel organic semiconductors and sensing materials.

Starting from the commercially available 4-bromoindole, a concise and efficient enantioselective formal synthesis of (+)-cycloclavine (1) in 13 steps with 2.0% overall yield and a total synthesis of (+)-5-epi-cycloclavine (2) in 14 steps with 3.3% overall yield were achieved. Key features of the syntheses include the addition of a Grignard reagent to the C═N/Heck reaction sequence to construct the fused 6–5–6 ring systems, cyclopropanation, an ester aminolysis reaction, and the first example of the construction of a 3-azabicyclo[3,1,0]hexane through an intramolecular [3 + 2] cycloaddition/nitrogen extrusion.

Two piezochromic molecules, (2Z,4E)-2-(4-(Diphenylamino)phenyl)-5-phenylpenta-2,4-dienenitrile (1a) and (2Z,4E)-2-(4-(acridin-10(9H)-yl)phenyl)-5-phenylpenta-2,4-dienenitrile (1b), were synthesized by using Knoevenagel and Buchwald-Hartwig cross-coupling reactions. Their piezochromic fluorescence behavior was tuned by subtle structural change. The system indicates typical intramolecular charge-transfer properties. The luminescence intensity of 1a decreased with increasing pressure with the redshift of the emission wavelength when the hydrostatic pressure in a diamond anvil cell (DAC) was applied on its crystal. However, the emission wavelength of 1b which has a methylene unit more than 1a had no obvious shift and the intensity increased gradually at the pressure range from 0.66 GPa to 5.72 GPa.

New coordination polymers of cobalt(II), namely, [Co(μ4-cpna)(H2O)2]n (1), [Co(μ3-cpna)(phen)(H2O)]n·nH2O (2), [Co3(μ4-dppa)2(H2O)6]n·2nH2O (3), and [Co3(μ5-dppa)2(μ-4,4′-bipy)(H2O)2]n·4nH2O (4), h...

A rapid construction of the tetracyclic core (±)-2 of (±)-cycloclavine (1) was accomplished in seven steps and 24% overall yield from commercially available aldehyde 7. Key features include a domino Friedel-Crafts/nitro-Michael reaction to construct the C ring and an intramolecular ammonolysis of a diester to close the D ring. In addition, a versatile 4-amino Uhle's ketone (±)-3 was afforded rapidly in five steps and 43% overall yield.

5-(3,4-Dicarboxylphenyl)picolinic acid (H3dppa) was applied as a novel tricarboxylic acid block with phthalate and picolinate functionalities for the aqueous-medium assembly of seven new coordination compounds, namely, [Mn2(μ-Hdppa)2(phen)2(H2O)2] (1), {[Mn(μ-Hdppa)(2,2′-H2biim)(H2O)]·H2O}n (2), [Ni(Hdppa)(phen)2]·4H2O (3), {[Ni(μ-Hdppa)(μ-4,4′-bipy)(H2O)]·H2O}n (4), {[Cu3(μ3-dppa)(μ-Hdppa)(phen)4]2[Cu(μ-Hdppa)2]·10H2O}n (5), {[Ni3(μ-dppa)2(μ-1,4-bpb)2(H2O)6]·4H2O}n (6), and {[Zn3(μ4-dppa)2(phen)2(H2O)2]·4H2O}n (7). These products 1–7 represent the first structurally characterized examples of the coordination compounds derived from H3dppa. Compounds 1–7 were assembled in the presence of various N-donor supporting ligands acting as crystallization mediators, which were selected from 1,10-phenanthroline (phen), 2,2′-biimidazole (H2biim), 4,4′-bipyridine (4,4′-bipy), or 1,4-bis(pyrid-4-yl)benzene (1,4-bpb). Full characterization of 1–7 by IR spectroscopy, thermogravimetric (TGA), elemental, and topological analyses, as well as powder (PXRD) and single-crystal X-ray diffraction, was performed. The structural types range from the discrete 0D complexes (1 and 3) and 1D coordination polymers with a 2C1 topology (2, 5, and 6) to the 2D metal–organic layers with an sql topology (4 and 7). The structural diversity of 1–7 is driven by various factors, including the metal(II) node nature, deprotonation degree of H3dppa, or type of crystallization mediator. The magnetic properties of 1, 2, 4, and 6 were studied and modeled, revealing antiferromagnetic (in 1, 2, and 6) or ferromagnetic (in 4) interactions between adjacent metal(II) centers. The luminescence of 7 was also investigated. Moreover, the photocatalytic activity of 1–7 was studied for the degradation of methylene blue as a model dye pollutant, disclosing that the nickel(II) coordination polymer 4 is the most active catalyst. The observed catalytic activity of 1–7 correlates well with their band gap energies determined by the UV-diffuse reflectance method.

Hypochlorous acid (HOCl) is one of the typical reactive oxygen species (ROS), which plays a crucial role in the immune system, and is involved in many neurodegenerative disorders, such as ischemic stroke, Alzheimer's, and Parkinson's disease. A two-photon probe for sensing HOCl with high selectivity, fast response (within 30 s), good penetration depth and low cytotoxicity is reported. Under two-photon excitation, the probe exhibited a remarkable fluorescence ‘‘turn-on’’ response to HOCl. Furthermore, the probe was successfully applied to the monitoring of endogenous HOCl stimulated by lipopolysaccharide in living microglia BV-2 cells.

The design and synthesis of high-performance n-type organic semiconductors are important for the development of future organic optoelectronics. Facile synthetic routes to reach the K-region of pyrene and produce 4,5,9,10-pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm2 V−1 s−1. The tert-butyl-substituted compounds (t-PyDI) also showed good one- and two-photon excited fluorescence properties. The PyDI derivatives are a new family of aromatic diimides that may exhibit both high electron mobility and good light-emitting properties, thus making them excellent candidates for future optoelectronics.

An efficient and direct route to ergot alkaloid (-)-chanoclavine I (3) is described using the inexpensive compound (2R)-(+)-phenyloxirane (15) as a chiral pool in 13 steps with 17% overall yield. Key features of the synthesis include a palladium-catalyzed intramolecular aminoalkynylation of terminal olefin and a rhodium-catalyzed intramolecular [3 + 2] annulation. An oxygen-substituted ergoline derivative (-)-25 was also achieved by using the same strategy.

An enantioselective tandem Michael addition/ cyclization reaction between trisubstituted 2-nitro-1,3-enynes and cyclic 1,3-diketones catalyzed by a chiral organosquaramide catalyst in the presence of Ag2CO3 was developed. The chiral functionalized chromene products could be obtained in good yield and in 80-99% enantiomeric excess. The structures and absolute configurations of some of the products were confirmed by X-ray crystallographic analysis.

In this work, a trifunctional N,O-building block, 5-(4-carboxyphenoxy)nicotinic acid (H2cpna), that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether) was used for the hydrothermal assembly of thirteen new coordination compounds: [Co(μ3-Hcpna)2]n (1), [Mn(μ4-cpna)(H2O)]n (2), [Mn(μ4-cpna)(H2O)2]n (3), [Mn(μ-cpna)(2,2'-bipy)(H2O)2]n (4), {[Ni(μ3-cpna)(2,2'-bipy)(H2O)]2·H2O}n (5), {[Cd(μ3-cpna)(2,2'-bipy)]·2H2O}n (6), [Zn2(μ-cpna)2(2,2'-bipy)2] (7), [Cu(μ-cpna)(2,2'-bipy)(H2O)]n (8), {[Mn(μ-cpna)(phen)2]·6H2O}n (9), {[Ni(μ3-cpna)(phen)(H2O)]·H2O}n (10), [Zn2(μ-cpna)2(phen)2] (11), {[Pb(μ3-cpna)(phen)]·H2O}n (12), and [Ni(μ3-cpna)(4,4'-bipy)0.5(H2O)]n (13). These products were synthesized from the corresponding metal(ii) chlorides, H2cpna, NaOH, and optional N-donor supporting ligands or templates {bis(4-pyridyl)amine (bpa), 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), or 1,10-phenanthroline (phen)}. Products 1-13 were characterized in the solid state by standard methods, including elemental and thermogravimetric analysis (TGA), IR spectroscopy, and powder (PXRD) and single-crystal X-ray diffraction. The structures of 1-13 feature distinct structural types, namely the 3D metal-organic frameworks (MOFs 1-3), the 2D coordination polymers (5, 6, 10, 12, and 13), the 1D coordination polymers (4, 8, and 9), and the 0D discrete cyclic dimers (7 and 11). Such a wide structural diversity of 1-13 is driven by various factors, including the type of the metal(ii) node, the deprotonation degree of H2cpna, and/or the type of supporting ligand or template. Notably, an addition of bpa can tune the structure of MOF 3 by the template effect. Topological classification of underlying metal-organic networks was performed, leading to several distinct topological nets: rtl (in 1), hxg-d-4-C2/m (in 2), sra (in 3), 2C1 (in 4, 8 and 9), fes (in 5, 10, and 12), hcb (in 6), and 3,4L83 (in 13). The magnetic behavior of 1-5, 8-10, and 13 was studied and theoretically modeled, disclosing antiferromagnetic interactions. The luminescence behavior of 6, 7, 11, and 12 was also investigated.

Pyrazine-fused isoindigo (PzIIG) was designed and synthesized as a novel electron acceptor to construct two D–A conjugated polymers, PzIIG-BDT2TC8 and PzIIG-BTT2TC10. Both the polymers were successfully applied in polymer solar cells, and the PzIIG-BDT2TC8 based solar cell device exhibited a PCE of 5.26% with a high Voc over 1.0 V.

In this work, an ether-bridged aromatic carboxylic acid, 2-(2-carboxyphenoxy)terephthalic acid (H3cpta), was applied as an unexplored building block for the generation of a novel series of coordination compounds, which represent the first examples of structurally characterized products derived from H3cpta, thus opening up its use as a versatile building block in crystal engineering research. The obtained products were formulated as [Cd(μ-Hcpta)(phen)(H2O)]n (1), [Mn(μ-Hcpta)(phen)(H2O)]n (2), {[Cd3(μ3-Hcpta)(μ4-cpta)(μ-Cl)(H2O)4]·2H2O}n (3), {[Cd3(μ6-cpta)2(py)2]·5H2O}n (4), [Mn3(μ5-cpta)2(2,2′-bipy)2]n (5), [Mn3(μ4-cpta)2(phen)3(H2O)2]n (6), {[Zn3(μ3-cpta)2(phen)3]·3H2O} (7), [Cd2(μ4-cpta)(μ-Cl)(phen)2]n (8), [Cd3(μ5-cpta)2(phen)2(H2O)2]n (9), [Cd3(μ4-cpta)2(phen)3(H2O)2]n (10), [Cd3(μ5-cpta)2(H2biim)2]n (11), [Zn2(μ6-cpta)(μ-Hbiim)]n (12), and [Ni3(μ3-cpta)2(phen)3(py)3(H2O)3]n (13). These compounds were assembled in the presence of an optional N-donor ancillary ligand, which was selected from 1,10-phenanthroline (phen), pyridine (py), 2,2′-bipyridine (2,2′-bipy), or 2,2′-biimidazole (H2biim). The obtained compounds 1–13 were fully characterized, including by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder (PXRD) and single-crystal X-ray diffraction. The structures of 1–13 vary from a discrete 0D dimer (1) to the 1D (2, 3, 7, and 13) and 2D (5, 6, and 8–11) coordination polymers, as well as to the 3D metal–organic frameworks (MOFs 4 and 12). Such a wide structural diversity of 1–13 is guided by the following factors: a type of metal(II) node and counter anion, a deprotonation degree of the principal H3cpta block, and/or a type of an auxiliary ligand. Topological classification of H-bonded (in 1) and metal–organic (in 2–13) underlying networks was performed, disclosing the following topological types: sql (in 1), 2C1 (in 2 and 7), 3,4,5L45 (in 5, 9, and 11), 3,4L128 (in 6 and 10), 3,3,4L29 (in 8), and SP 1-periodic net (in 13), as well as some topologically unique nets (in 3, 4, and 12). Besides, magnetic properties of 2, 5, 6, and 13 were studied and modeled, revealing antiferromagnetic interactions between adjacent metal(II) centers. In addition, luminescence properties were investigated for 1, 3, 4, and 7–12; MOF 4 can be used as a sensitive material for the detection of Fe3+ ions in aqueous solution through the luminescence quenching effect.

A three-component aqueous reaction system comprising copper(II) acetate (metal node), poly(carboxylic acid) with a phenylpyridine or biphenyl core (main building block), and 1,10-phenanthroline (crystallization mediator) was investigated under hydrothermal conditions. As a result, four new coordination compounds were self-assembled, namely, {[Cu(μ3-cpna)(phen)]·H2O}n (1), {[Cu(μ-Hbtc)(phen)]·H2O}n (2), {[Cu(μ3-Hcpic)(phen)]·2H2O}n (3), and [Cu6(μ-Hcptc)6(phen)6]·6H2O (4), where H2cpna = 5-(2′-carboxylphenyl)nicotinic acid, H3btc = biphenyl-2,4,4′-tricarboxylic acid, H3cpic = 4-(5-carboxypyridin-2-yl)isophthalic acid, H3cptc = 2-(4-carboxypyridin-3-yl)terephthalic acid, and phen = 1,10-phenanthroline. Crystal structures of compounds 1–3 reveal that they are 1D coordination polymers with a ladder, linear, or double-chain structure, while product 4 is a 0D hexanuclear complex. All of the structures are extended further [1D → 2D (1 and 2), 1D → 3D (3), and 0D → 3D (4)] into hydrogen-bonded networks. The type ...

A series of triphenylethylene-based luminophoric molecules were efficiently synthesized. The substituent effect of the fluorophores on their photophysical properties was then investigated. Consequently, it was found that longer conjugated system and larger molecular dipole of the donor–π–acceptor fluorophores could result in bathochromic shifts of UV–vis absorption and emission bands, so do the Stokes shifts. Especially, full-color fluorescent emissions in both solution and solid states could be achieved by changing conjugation length and substituents with different electron-donating or accepting abilities in the triphenylethylene skeleton. The density functional theory calculations further demonstrated that with the increase of the electron-donating or accepting abilities of the substituents, the energy gaps of the fluorophores gradually decreased, which elucidated the substituent effect of the organic fluorophores on their photophysical properties.

A series of peripheral dendron-incorporating 1,4-bis[2,2-bis(4-alkoxyphenyl)vinyl] benzenes with aggregation-induced emission properties were synthesized. As the generation of the dendrons increased, there was an enhancement in the fluorescence emission of the corresponding fluorophore not only in the solid state but also in various solvent systems. The fluorescence quantum yields of the molecule with the largest dendons were up to 71% in the solid state and 66% in solution. The dendrons acted as a shell to the fluorophore core to prevent intermolecular pi-pi interactions and restrict the intramolecular rotations of the fluorophore, which improved the luminous intensity. This study shows that the incorporation of bulky dendrons is an effective way to increase the fluorescence emission efficiency of aggregation-induced emission fluorophores.

Zn has vital importance to the environment as well as human health. To regulate its dietary ingestion, it is important to monitor its presence in our food and environment, evoking more accurate and more sensitive ways to quantitatively determine its content in the environment. We herein present a squaraine-based chemosensor, namely DMPSQ, which has turn-on fluorescence response toward Zn2+ ion with good linearity, high selectivity and sensitivity down to 80 ppb. Theoretical calculations were also conducted to provide insight to the sensing mechanism and the spectroscopic properties of the compound.

Two multifunctional, ether-bridged tricarboxylic acids, 2-(4-carboxylphenoxy)terephthalic acid (H3cpta) and 2-(3,5-dicarboxylatobenzyloxy)benzoic acid (H3dbba), were used as unexplored and highly versatile building blocks for the hydrothermal generation of a novel series of cadmium(ii) metal-organic architectures. These were formulated as [Cd(μ-Hcpta)(phen)(py)]n (1), {[Cd3(μ5-cpta)2(phen)3]·8H2O}n (2), {[Cd3(μ5-cpta)2(2,2'-bipy)3]·6H2O}n (3), {[Cd(μ3-cpta)(Hbpa)]·2H2O}n (4), {[Cd6(μ4-cpta)2(μ6-cpta)2(H2biim)2(H2O)6]·5H2O}n (5), [Cd3(μ4-cpta)2(μ-prz)(H2O)4]n (6), {[Cd3(μ4-dbba)2(phen)3]·H2O}n (7), and {[Cd3(μ3-dbba)2(2,2'-bipy)3(H2O)3]·2H2O}n (8) on the basis of single-crystal X-ray diffraction, elemental analysis, FTIR, PXRD, and TGA data. Products 1-8 were assembled in the presence of N-donor crystallization mediators selected from pyridine (py), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy), bis(4-pyridyl)amine (bpa), 2,2'-biimidazole (H2biim), or piperazine (prz). The nature of the crystallization mediator and/or the type of principal tricarboxylate building block have a significant effect on the structural diversity, dimensionality, and topology of the resulting cadmium-organic architectures. These span from 1D (1, 8) and 2D (7) coordination polymers to 3D metal-organic frameworks (2-6) with intricate topologies (3,4,5T64 in 2 and 3, utp (103)-d in 4, 3,4,4T9 in 6) that also include unprecedented types in 5 and 7. Besides, MOF 6 features a 3D + 3D two-fold interpenetrated framework. Luminescent and photocatalytic properties of selected materials were investigated, showing that coordination polymer 7 is a promising photocatalyst for the UV-light-driven degradation of methylene blue as a model organic dye pollutant. Moreover, products 7 and 8 are the first examples of structurally characterized coordination compounds derived from H3dbba.

This study reports the hydrothermal synthesis of a novel series of twelve coordination compounds, namely, {[Cd(μ-Hnbtc)(H2O)4]·H2O}n (1), [Zn2(μ-Hnbtc)2(phen)2]·2H2O (2), [Zn(Hnbtc)(phen)2(H2O)]·4.5H2O (3), [Ni(Hnbtc)(phen)2(H2O)]·6H2O (4), [Zn2(μ-Hnbtc)2(2,2′-bipy)2]·2H2O (5), [Cd3(μ5-nbtc)(μ6-nbtc)(2,2′-bipy)2(H2O)]n (6), {[Zn3(μ3-nbtc)2(phen)3(H2O)2]·4H2O} (7), [Co(H2O)6][Co2(nbtc)2(μ-4,4′-bipy)(4,4′-bipy)2(H2O)6]·8H2O (8), {[Ni3(μ4-nbtc)2(μ-4,4′-bipy)2.5(μ-H2O)(H2O)3]·4H2O}n (9), {[Cd2(μ4-nbtc)(μ-OH)(2,2′-bipy)2]·H2O}n (10), [Cd2(μ4-nbtc)(μ-OH)(phen)2(H2O)]n (11), and {[Zn2(μ5-nbtc)(μ3-OH)(μ-4,4′-bipy)]·4,4′-bipy·H2O}n (12), which are derived from 3′-nitro-biphenyl-2,4,4′-tricarboxylic acid (H3nbtc) as a virtually unexplored building block. These compounds were generated in aqueous medium from the corresponding metal(II) chlorides as a metal source, H3nbtc as a principal building block, NaOH as a base, and simple N,N-donor aromatic ligands as crystallization mediators (i.e., 1,10-phenanthroline, phen; 2,2′-bipyridine, 2,2′-bipy; or 4,4′-bipyridine, 4,4′-bipy). All products 1–12 were completely characterized in the solid state by IR spectroscopy, elemental and thermogravimetric (TGA) analyses, powder (PXRD) and single-crystal X-ray diffraction. Structures of 1–12 range from discrete 0D dimers (2 and 5) or monomers (3, 4, and 8) to 1D coordination polymers (CPs, 1, 6, 7, 10, and 11) and 3D metal–organic frameworks (MOFs, 9 and 12). A broad structural diversity of 1–12 is guided by the type of the metal(II) node, the molar ratio between H3nbtc and sodium hydroxide, and the kind of crystallization mediator. Topological analysis and classification of metal–organic underlying nets was made, disclosing the following topological types: 2C1 (in 1 and 7), 1M2-1 (in 2 and 5), SP1-periodic net (in 10 and 11), tfz-d (in 12), and some topologically unique nets (in 6 and 9). Luminescence behavior of 1–3, 5–7, and 10–12 was studied in the solid state. Magnetic properties of a Ni(II) MOF 9 were also investigated and modeled. All obtained products 1–12 represent the first structurally characterized examples of coordination compounds derived from H3nbtc, thus opening up its application in coordination chemistry as a novel tricarboxylate building block.

Selected recent examples of coordination polymers (CPs) or metal-organic frameworks (MOFs) constructed from different multifunctional carboxylic acids with phenyl-pyridine or biphenyl cores have been discussed. Despite being still little explored in crystal engineering research, such types of semi-rigid, thermally stable, multifunctional and versatile carboxylic acid building blocks have become very promising toward the hydrothermal synthesis of metal-organic architectures possessing distinct structural features, topologies, and functional properties. Thus, the main aim of this mini-review has been to motivate further research toward the synthesis and application of coordination polymers assembled from polycarboxylic acids with phenyl-pyridine or biphenyl cores. The importance of different reaction parameters and hydrothermal conditions on the generation and structural types of CPs or MOFs has also been highlighted. The influence of the type of main di- or tricarboxylate ligand, nature of metal node, stoichiometry and molar ratio of reagents, temperature, and presence of auxiliary ligands or templates has been showcased. Selected examples of highly porous or luminescent CPs, compounds with unusual magnetic properties, and frameworks for selective sensing applications have been described.

The asymmetric synthesis of Szántay's amine (+)-2, the pivotal precursor for direct access to (+)-cycloclavine (1), is described for the first time in eleven steps with 19.7% overall yield from the commercially available 4-bromoindole. The strategy features an asymmetric induction by Ellman's sulfinimine and rhodium-catalysed isomerization of the C[double bond, length as m-dash]C bond.

An efficient Knoevenagel condensation reaction was used to construct a series of α-cyano-α,ω-diaryloligovinylenes, which show prominent fluorescence emission in the solid state. On investigating the effect of conjugation length on fluorescent properties, we found that the diene structure showed superior solid-state luminescence. Furthermore, the emission color could be adjusted by introducing donor or acceptor functional groups at the terminal aryl groups. Full-color emission in the visible region can be achieved by adding different functional groups to the α-cyano-α,ω-diaryldivinylene moiety. The structure-property relationships were elucidated and some observations such as the substitution position effects were discussed. These compounds have potential applications as full-color solid emissive candidates in material science and their simple structures allow them to be easily modified resulting in further interesting properties.

Daphenylline, a novel daphniphyllum alkaloid, boasts a fused and bridging ring system coupled with six stereogenic centers. Here we present a direct and short construction of the ACDE ring system of daphenylline from the known 3-(2-bromophenyl)propanal in 10 steps and 17 % overall yield. The synthesis features an iron(III)-catalyzed aza-Cope-Mannich reaction, a self-terminating 6-exo-trig aryl radical-alkene cyclization and an intramolecular Friedel-Crafts acylation.

Highly efficient organic reactions in water are important for designing environmental-friendly and low cost synthetic processes. Herein, we demonstrate an intermediate-in-water strategy for the heterogeneous synthesis of benzofurans in aqueous media. The cyclization reaction of 2-(phenylethynyl)phenol to 2-phenylbenzofuran cannot proceed in pure water. However, this reaction can be efficiently promoted by the formation of sparingly soluble intermediate in the presence of alkaline. Quantitative conversion of a variety of substrates to benzofuran derivatives has been achieved in the absence of noble metal catalyst. Other remarkable features including easy-isolation and purification of product, along with wide range of functional group tolerance render the methodology promising in the realm of green-synthesis.

Tributylphosphine-catalyzed regioselective [3+2] cycloadditions between ethyl 5,5-diarylpenta2,3,4-trienoate 1 and various aromatic aldehydes 2 to produce a wide variety of polysubstituted 2,5-dihydrofurans 3, and between 1 and beta-unsubstituted alpha,beta-unsaturated carbonyl compounds 5 to give polysubstituted cyclopentenes 6 with a quaternary carbon center, are reported. In both cases the reaction partners approach each other via the sterically less hindered orientation to afford the target products in excellent regioselectivity. The reaction mechanism involved first the generation of a zwitterionic intermediate between the butatriene 1 and PBu3. For the formation of 2,5-dihydrofurans 3, the preferred cyclization mode encompassed the nucleophilic attack of the a-position of butatriene to the aldehydic carbon of 2, followed by the ring closure between the aldehydic oxygen of 2 and the gamma-position of butatriene, which is the first report of a normal [3+2] cycloaddition between cumulenes and aldehydes. For the formation of cyclopentenes 6, the reaction involved attack of the gamma-position of the butatriene to the electron-deficient beta-position of the alpha,beta-unsaturated carbonyl compounds 5, followed by the ring closure between the alpha-position of 5 and the a-position of butatriene, which shows a different regioselectivity to the previously reported [3+2] cycloadditions between butatriene and olefins.

An efficient formal synthesis of (±)-cycloclavine is achieved in seven steps and 27% overall yield from the known 2-(4-bromo-1-tosyl-1H-indol-3-yl)acetaldehyde. Key features include an iron(III)-catalyzed aza-Cope-Mannich cyclization and an intramolecular Heck reaction or a self-terminating 6-exo-trig aryl radical-alkene cyclization.

We designed two cruciform-structured oligo(phenylenethynylene) (OPE) molecular wires for probing the intra- and inter-molecular exciton migration pathways, and constructed highly ordered molecular assembly using Langmuir–Blodgett (LB) technique. Minor structural variation turns out to influence significantly exciton migration routes. Though the molecular structures are similar, these two molecules exhibit distinct exciton migration behaviors. Intermolecular exciton migration is observed in unmodified molecular wire OPE1; while only intramolecular exciton migration is allowed in the side-chain modified molecular wire OPE2. This work presents a facile strategy for controlling exciton migration in solid state, and provides useful insights for designing active components for opto-electronic devices.

A new heteroacenequinone, pentaceno[2,3-c:9,10-c']bis([1,2,5]thiadiazole)-6,13-dione (PBTDQ), with two peripheral thiadiazole rings was synthesized, and its solid-state properties were characterized. The fused planar structure with a low-lying LUMO and low reorganization energy facilitates electron transport, affording μe values of up to 0.11 cm(2) V(-1) s(-1) in field-effect transistor devices.

The stereoselective synthesis of malyngamide M (1) was accomplished in nine steps from o-cresol in 12% overall yield. The key steps involved the Wittig reaction of an α-NHBoc aryl ketone 4 for the introduction of vinyl chloride functionality, an amidation of lyngbic acid 3 with a secondary amine 2 for the framework of target molecule, and an isomerization of a (Z)-vinyl chloride to the (E)-configuration using benzophenone as a photosensitizer. The isomalyngamide M (Z-1) was also synthesized.

A series of amphiphilic dendrons (G1-G4) have been designed and synthesized, which have a highly branched aliphatic hydrocarbon skeleton and a hydrophilic hydroxyl functionality to enable conjugation with other substrates. The higher generation dendrons (G3 and G4) were synthesized by a double-stage convergent method, which shortened the synthetic route significantly and provided the products in an efficient manner. The key branching step involved a double alkyl-metal addition to an ester functionality followed by deoxygenation of a resulting tertiary alcohol by triethylsilane.

Two series of oligo(phenylene ethynylene)s (OPEs) with different dendrimer side groups have been designed and synthesized. The molecules contain thiol groups at both ends to enable interconnection between nanoscale gapped metallic electrodes. The different dendrimer groups act as "shells", allowing tailoring to the nanoscopic environment surrounding the OPE "core". Meanwhile, the dendrimer shells also act as spacers for the precise control of the packing density and intermolecular interaction between the OPE cores. [structure: see text].

A series of methylidene substituted 2,5-dihydrofurans is prepared via the reaction of ethyl 5,5-diphenylpenta-2,3,4-trienoate (I) with aryl or hetaryl aldehydes.

The selective electroanalysis of dopamine (DA) using the self-assembled monolayers of an oligo(phenyleneethynylene)s (OPEs) type molecular wire have been studied for the first time. Cyclic voltammetry measurement showed the OPE modified electrodes preferentially inhibit the electrochemical reaction of ascorbic acid (AA). Using square-wave voltammetry technique, DA was quantitatively determined in the presence of high concentration AA. This work reveals that, besides molecular electronics, biosensor could be an attractive new field of application for the OPE type molecular wires. Keywords: Self-assembled monolayers (SAMs), Molecular wires, Dopamine, Modified electrodes, Oligo(phenylene ethynylene) (OPE)

Long chain branched dendrimers 1,2 and 3were easily prepared according to the convergent strategy based on the A2B type monomer from 5-hydroxyisophthalic acid. These dendrimers have a nucleophilic phenol focal group, which is useful to further chemistry.

A Lewis acid promoted tandem reaction of epoxide rearrangement and intramolecular [3+2] cycloaddition reaction of cyclopropanes with carbonyls formed by epoxide rearrangement in situ, which were obtained with difficulty by a general method, is reported. A wide variety of fused- and spiro-oxa-[n.2.1] skeletons could be efficiently constructed.

Photovoltaic cells are considered to be one of the most promising renewable energy sources of the 21st century. In particular, dye-sensitized solar cells (DSSCs) and organic photovoltaic devices (OPVs) are potentially the most economical and environmentally friendly ones. Squaraine (SQ) has intense absorption at 600–850 nm, exactly where sun flux is the most abundant. Furthermore, various substituents on SQ cores provide great possibilities for different molecular-design strategies. These characters make SQs ideal candidates for new DSSCs and OPVs. In response to the rapid development of SQ-based solar cells, a panorama of these ongoing studies is presented here, including the general synthetic routes of SQs and the various SQs used in DSSCs and OPVs. Our discussions are focused on the diverse molecular designs of SQs used in DSSCs and OPVs. The design strategies to acquire better light-harvesting abilities are also provided here, as well as the principles behind these strategies.

Alkyl chains are basic units in the design of organic semiconductors for purposes of enhancing solubility, tuning electronic energy levels, and tailoring molecular packing. This work demonstrates that the carrier mobilities of indeno[1,2-b]fluorene-6,12-dione (IFD)-based semiconductors can be dramatically enhanced by the incorporation of sulfur- or nitrogen-linked side chains. Three IFD derivatives possessing butyl, butylthio, and dibutylamino substituents are synthesized, and their organic field-effect transistors (OFET) are fabricated and characterized. The IFD possessing butyl substituents exhibits a very poor charge transport property with mobility lower than 10−7 cm2 V−1 s−1. In contrast, the hole mobility is dramatically increased to 1.03 cm2 V−1 s−1 by replacing the butyl units with dibutylamino groups (DBA-IFD), while the butylthio-modified IFD (BT-IFD) derivative exhibits a high and balanced ambipolar charge transport property with the maximum hole and electron mobilities up to 0.71 and 0.65 cm2 V−1 s−1, respectively. Moreover, the complementary metal–oxide–semiconductor-like inverters incorporated with the ambipolar OFETs shows sharp inversions with a maximum gain value up to 173. This work reveals that modification of the aromatic core with heteroatom-linked side chains, such as alkylthio or dialkylamino, can be an efficient strategy for the design of high-performance organic semiconductors.

The reactions can be performed without microwave irradiation providing the corresponding products after significantly longer reaction times in lower yields.

Monoaryne and monoisobenzofuran analogues of a C(3v)-symmetrical tribenzotriquinacene (TBTQ) were generated in situ and trapped with various dienes and dienophiles, respectively. In this way, a series of single-wing extended TBTQ derivatives bearing the bowl-shaped TBTQ unit in different topographical expositions have become accessible. This includes some novel tribenzotriquinacene "dimers", in which two TBTQ bowls are attached in syn- or anti-orientation at the terminal positions of rigid linker units. Several of these compounds have been characterized by both spectroscopy and X-ray structural analysis. The efficient access to the TBTQ "dimers" may lay a useful foundation for further studies of novel container compounds and supramolecular architectures.

The novel double-stage convergent synthesis of a new class of polyisoprene terpenoid (PIPTP) dendrons is described. PIPTP dendrons bear a highly branched aliphatic hydrocarbon skeleton and a hydrophilic hydroxy focal point functionality. These dendrons have the specific formula C((5×2)(G+1)(-5))H((5×2)(G+2)(-8))O, and each dendritic layer is constructed from an isoprene unit. The key branching steps involve a double alkyl-metal addition to an ester functionality, followed by deoxygenation of the resulting tertiary alcohol by triethylsilane and trifluoroacetic acid, then hydrogenation or hydrogenolysis. The dendrons were also attached to oligo(phenylene ethynylene)s (OPEs) so as to function as protective shells to allow fine tuning of the nanoscopic environment around the OPE moiety, and to exert precise control of the packing density and intermolecular interaction between the OPE cores. Fluorescence quantum yield data reveal that the OPE core is better encapsulated by the PIPTP dendrons than by Fréchet dendrons.

Understanding the effects of intermolecular interactions on the charge-transport properties of metal/ molecule/metal junctions is an impor- tant step towards using individual mol- ecules as building blocks for electronic devices. This work reports a systematic electron-transport investigation on a series of "core-shell"-structured oligo(- phenylene ethynylene) (Gn-OPE) mo- lecular wires. By using dendrimers of different generations as insulating "shells", the intermolecular p-p inter- actions between the OPE "cores" can be precisely controlled in single-com- ponent monolayers. Three techniques are used to evaluate the electron-trans- port properties of the Au/Gn-OPE/Au molecular junctions, including crossed- wire junction, scanning tunneling spec- troscopy (STS), and scanning tunneling microscope (STM) break-junction tech- niques. The STM break-junction mea- surement reveals that the electron- transport pathways are strongly affect- ed by the size of the side groups. When the side groups are small, electron transport could occur through three pathways, including through single- molecule junctions, double-molecule junctions, and molecular bridges be- tween adjacent molecules formed by aromatic p-p coupling. The dendrimer shells effectively prohibit the p-p cou- pling effect, but at the same time, very large dendrimer side groups may hinder the formation of AuS bonds. A first-generation dendrimer acts as an optimal shell that only allows electron transport through the single-molecule junction pathway, and forbids the other undesired pathways. It is demonstrated that the dendrimer-based core-shell strategy allows the single-molecule conductance to be probed in a homo- genous monolayer without the influ- ence of intermolecular p-p interac- tions.

A series of 1,4-bis[2,2-bis(4-alkoxyphenyl)vinyl]benzene molecules with aggregation-induced emission (AIE) activity were synthesized. The conformations and packing arrangements of these molecules in the solid state can be adjusted by changing the side chains, which subsequently modulates their solid-state emission. The fluorescence quantum yield of 1e with the n-C(6)H(13) side chain in the solid state could reach up to 60.3% in the solid state.

The title compound, [Co(C(14)H(6)N(2)O(4))(H(2)O)(3)]·2H(2)O, has two-fold crystallographic symmetry. The Co(II) atom is in a distorted penta-gonal-bipyramidal coordination environment with two N atoms and two O atoms from a tetradentate 1,10-phenanthroline-2,9-dicarboxyl-ate ligand and one O atom from a water mol-ecule forming the penta-gonal plane, and two O atoms from two water mol-ecules occupying axial positions. In the crystal, adjacent mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network.

Two series of new oligothiophene-pentacene hybrid compounds were successfully synthesized and characterized, which consist of pentacene and anthradithiophene skeletons modified by different oligothienyl groups at 6,13 sites or 5,11 sites, respectively. Their optical, thermal, and electrochemical properties show regular variations with the length change of the side groups. These materials exhibit much higher solubility and significantly improved thermal and photooxidation stabilities compared with unmodified pentacene and anthradithiophene.