A Molecular Cage Accessed by Threefold Click Reaction of a C3v-Symmetric Triazido-Functionalized Tribenzotriquinacene.

The hitherto unknown hexakis(halomethyl)-functionalized tribenzotriquinacenes (TBTQs) 9 and 10 were synthesized from the key 4b,8b,12b-tribromo-TBTQ derivative 6 by an improved route in 67% overall yield. Extension of the bowl-shaped framework of 9 or 10 by threefold condensation with propargylamine or 2-azidoethylamine afforded the corresponding TBTQ-trialkyne 11 and TBTQ-triazide 12, respectively. While attempts to construct bis-TBTQ cages, including homodimerization of 11 and heterocoupling of 11 with 12, were unsuccessful, triazide 12 was found to undergo threefold [3 + 2]-cycloaddition with 3-ethynylaniline and phloroglucinol tripropargyl ether under click chemistry conditions. The latter reaction enabled facile capping of the TBTQ bowl to give the novel cage compound 5 in 22% yield.

A Paternò-Büchi Reaction of Aromatics with Quinones under Visible Light Irradiation.

Reported herein is a Paternò-Büchi reaction of aromatic double bonds with quinones under visible light irradiation. The reactions of aromatics with quinones exposed to blue LED irradiation yielded oxetanes at -78 °C, which was attributed to both the activation of double bonds in aromatics and the stabilization of oxetanes by thiadiazole, oxadiazole, or selenadiazole groups. The addition of Cu(OTf)2 to the reaction system at room temperature resulted in the formation of diaryl ethers via the copper-catalyzed ring opening of oxetanes in situ. Notably, the substrate scope was extended to general aromatics.

Cobalt(II) Coordination Polymers Assembled from Unexplored Pyridine-Carboxylic Acids: Structural Diversity and Catalytic Oxidation of Alcohols.

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·2 nH2O (3), and [Co3(µ5-dppa)2(µ-4,4'-bipy)(H2O)2] n·4 nH2O (4), have been generated under hydrothermal conditions from CoCl2·6H2O, two different multifunctional pyridine-carboxylic acids {H2cpna: 5-(4-carboxyphenoxy)nicotinic acid; H3dppa: 5-(3,4-dicarboxylphenyl)picolinic acid}, and optional N, N-supporting ligands {phen: 1,10-phenanthroline; 4,4'-bipy: 4,4'-bipyridine} acting as mediators of crystallization. These Co(II) coordination polymers (CPs) have been obtained as stable crystalline materials and characterized by conventional solid-state techniques, including X-ray crystallography. The obtained products are 3D metal-organic frameworks (MOFs 1 and 4) or 2D coordination polymers (CPs 2 and 3). Analysis of the topologies of simplified nets has revealed the sra (1), fes (2), and 3,4L13 (3) networks, in addition to a very complex topologically unique framework in 4. An observed diversity of structures is driven by types of carboxylate building blocks and crystallization mediators. Thermal stability and magnetic and catalytic properties of 1-4 have also been studied. In fact, the Co(II) compounds act as heterogeneous catalysts for the oxidation of alcohols with tBuOOH ( tert-butylhydroperoxide) under mild conditions. Compound 2 features a good catalytic activity (up to 45% yield) in the oxidation of 1-indanol to 1-indanone. Finally, products 1-4 broaden a still very small number of CPs or MOFs driven by the present type of multifunctional pyridine-carboxylic acids (H2cpna, H2dppa).

Metal-Organic Architectures Assembled from Multifunctional Polycarboxylates: Hydrothermal Self-Assembly, Structures, and Catalytic Activity in Alkane Oxidation.

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 of a multicarboxylate building block has a considerable effect on the final structures of 1-4. The magnetic behavior and thermal stability of 1-4 were also investigated. Besides, these copper(II) derivatives efficiently catalyze the oxidation of cycloalkanes with hydrogen peroxide under mild conditions. The obtained products are the unique examples of copper derivatives that were assembled from H2cpna, H3btc, H3cpic, and H3cptc, thus opening up their use as multicarboxylate ligands toward the design of copper-organic architectures.

Construction of the tetracyclic core of (±)-cycloclavine and 4-amino Uhle's ketone.

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.

Total Synthesis of (-)-Chanoclavine I and an Oxygen-Substituted Ergoline Derivative.

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.

4,5,9,10-Pyrene Diimides: A Family of Aromatic Diimides Exhibiting High Electron Mobility and Two-Photon Excited Emission.

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.

Pentacenobis(thiadiazole)dione, an n-type semiconductor for field-effect transistors.

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.

Formal synthesis of (±)-cycloclavine.

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.

Single-wing extended tribenzotriquinacenes via bowl-shaped dehydrobenzene and isobenzofuran tribenzotriquinacene derivatives.

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.

A core-shell strategy for constructing a single-molecule junction.

Understanding the effects of intermolecular interactions on the charge-transport properties of metal/molecule/metal junctions is an important step towards using individual molecules 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) molecular wires. By using dendrimers of different generations as insulating "shells", the intermolecular π-π interactions between the OPE "cores" can be precisely controlled in single-component monolayers. Three techniques are used to evaluate the electron-transport properties of the Au/Gn-OPE/Au molecular junctions, including crossed-wire junction, scanning tunneling spectroscopy (STS), and scanning tunneling microscope (STM) break-junction techniques. The STM break-junction measurement reveals that the electron-transport pathways are strongly affected 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 between adjacent molecules formed by aromatic π-π coupling. The dendrimer shells effectively prohibit the π-π coupling effect, but at the same time, very large dendrimer side groups may hinder the formation of Au-S 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 homogenous monolayer without the influence of intermolecular π-π interactions.

Synthesis of Enantiopure Hydrocarbon Cages Based on an Optically Resolved C3-Symmetric Triaminotribenzotriquinacene.

The synthesis of the enantiomerically pure, D3-symmetric covalent hydrocarbon cages (+)-(M,M)-4 and (-)-(P,P)-4 bearing two C3-symmetrically functionalized tribenzobenzotriquinacene (TBTQ) vertices is reported. The enantiomerically pure TBTQ building blocks (+)-(M)-5 and (-)-(P)-5 were prepared via the diastereomeric TBTQ triamides obtained by use of both Boc-d- and Boc-l-phenylglycine as chiral auxiliaries.

High and balanced hole and electron mobilities from ambipolar thin-film transistors based on nitrogen-containing oligoacences.

We demonstrate a strategy for designing high-performance, ambipolar, acene-based field-effect transistor (FET) materials, which is based on the replacement of C-H moieties by nitrogen atoms in oligoacenes. By using this strategy, two organic semiconductors, 6,13-bis(triisopropylsilylethynyl)anthradipyridine (1) and 8,9,10,11-tetrafluoro-6,13-bis(triisopropylsilylethynyl)-1-azapentacene (3), were synthesized and their FET characteristics studied. Both materials exhibit high and balanced hole and electron mobilities, 1 having µ(h) and µ(e) of 0.11 and 0.15 cm(2)/V·s and 3 having µ(h) and µ(e) of 0.08 and 0.09 cm(2)/V·s, respectively. The successful demonstration of high and balanced ambipolar FET properties from nitrogen-containing oligoacenes opens up new opportunities for designing high-performance ambipolar organic semiconductors.

Triaqua-(1,10-phenanthroline-2,9-dicarboxyl-ato)cobalt(II) dihydrate.

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.

2-(Naphthalen-2-yl)azulene.

In the title compound, C(20)H(14), a naphthalene ring system is linked at the 2-position to the 2-C atom of the five-membered ring of an azulene unit. The compound crystallizes with two reasonably similar mol-ecules in the asymmetric unit. Neither mol-ecule is perfectly planar: the r.m.s. deviations from the best fit planes through all non-H atoms are 0.092 and 0.091 Šfor the two mol-ecules. The dihedral angle between the mol-ecular planes is 49.60 (4)°. The naphthalene and azulene ring systems are inclined at dihedral angles of 6.54 (12) and 5.68 (12)° in the two mol-ecules. The crystal structure exhibits two sets of parallel layers, a typical edge-to-face herringbone packing arrangement. The structure is stabilized by an extensive series of weak C-H⋯π inter-actions.

Enantioselective Formal Synthesis of (+)-Cycloclavine and Total Synthesis of (+)-5-epi-Cycloclavine.

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.

An improved asymmetric synthesis of malyngamide U and its 2'-epimer.

An accelerated and improved asymmetric synthesis of malyngamide U (1) and its 2'-epimer (2'-epi-1) was accomplished from readily available n-hexanal, ethanolamine and (R)-(-)-carvone. The key steps involved a Johnson-Claisen rearrangement in the synthesis of an unsaturated carboxylic acid 4 and an aldol reaction in the construction of the skeleton of 1 and 2'-epi-1. There are 13 steps in the synthesis, with a 2.7% overall yield for 1 and a 0.4% yield for 2'-epi-1.

A new series of Cd(ii) metal-organic architectures driven by soft ether-bridged tricarboxylate spacers: synthesis, structural and topological versatility, and photocatalytic properties.

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.

A new series of Co, Ni, Zn, and Cd metal-organic architectures driven by an unsymmetrical biphenyl-tricarboxylic acid: hydrothermal assembly, structural features and properties.

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.

Synthesis of oligo(phenylene ethynylene)s with dendrimer "shells" for molecular electronics.

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].