RhIII-Catalyzed Direct Heteroarylation of Unactivated C(sp3)-H with N-Heteroaryl Boronates.

Disclosed herein is a rhodium(III)-catalyzed direct heteroarylation reaction between unactivated aliphatic C(sp3)-H bonds in 2-alkylpyridines and heteroaryl organoboron reagents. This catalytic protocol is compatible with various heterocyclic boronates containing ortho- and meta-pyridine, pyrazoles, furan, and quinoline with strong coordination capability. The achievement of this methodology provides an efficient route to build new C(sp3)-heteroaryl bonds.

A Porous Carbazolic Al-MOF for Efficient Aerobic Photo-Oxidation of Sulfides into Sulfoxides under Air.

A robust, microporous, and photoactive aluminum-based metal-organic framework (Al-MOF, LCU-600) has been assembled by an in situ-formed [Al3O(CO2)6] trinuclear building unit and a tritopic carbazole ligand. LCU-600 shows a high water stability and permanent porosity for N2 and CO2 adsorption. Notably, the incorporation of photoresponsive carbazole moieties into LCU-600 makes it a highly efficient and recyclable photocatalyst for aerobic photo-oxidation of sulfides into sulfoxides under an air atmosphere at room temperature. Mechanism investigations unveil that photogenerated holes (h+), superoxide radical anion (O2•-), and singlet oxygen (1O2) are critical active spices for the photo-oxidation reaction performed in an air atmosphere.

Mesoporous MOF Based on a Hexagonal Bipyramid Co8-Cluster: High Catalytic Efficiency on the Cycloaddition Reaction of CO2 with Bulky Epoxides.

A mesoporous cobalt-based metal-organic framework (LCU-606) was synthesized based on a hexagonal bipyramid Co8(µ4-O)3 cluster and an N,N,N',N'-tetrakis-(4-benzoic acid)-1,4-phenylenediamine ligand (H4TBAP). LCU-606 featuring large pore diameters of 21.7 Å and exposed Lewis-acid metal sites could serve as an excellent heterogeneous catalyst for CO2 cycloaddition reaction with various epoxide substrates under mild conditions (1 atm CO2, 60 °C, and solvent free). In particular, when extending the substrates to bulkier ones, LCU-606 still shows high catalytic efficiency on account of the large pore aperture. Also, LCU-606 demonstrates high recyclability and stability in consecutive catalytic runs. Therefore, the high efficiency, recyclability, and generality on CO2 catalytic cycloaddition make LCU-606 a very promising heterogeneous catalyst for CO2 chemical fixation.

Recent Progress in Research on [2.2]Paracyclophane-Based Dyes.

In recent years, the [2.2]paracyclophane (PCP) ring has attracted extensive attention due to its features of providing not only chirality and electron-donating ability but also steric hindrance, which reduces intermolecular π-π stacking interactions and thereby improves the fluorescence properties of dyes. To date, some circularly polarized luminescence (CPL)-active small organic molecules based on the PCP skeleton have been reviewed; however, the application of the PCP ring in improving the photophysical properties of fluorescent dyes is still limited, and new molecular design strategies are still required. This review summarizes and promotes the application of PCP in fluorescent dye design, fluorescence detection, and CPL modulation. We expect that this review will provide readers with a comprehensive understanding of the PCP skeleton and lead to further improvement in fluorescent dye design.

3D Boranil Complexes with Aggregation-Amplified Circularly Polarized Luminescence.

The development of small organic CPL-active molecules with large luminescent dissymmetry factors is highly demanded due to their promising applications in chiroptical devices and sensors. This work describes the design and synthesis of a new family of CPL-active BF2 complexes, (Rp)/(Sp)-3a-3e, which were constructed by fusing a N̂O-chelated BF2 complex with [2.2]paracyclophane. These complexes display aggregation-amplified CPL with moderate dissymmetry factors values and moderate quantum yields both in solution and in the solid state. In addition, these photophysical properties were rationalized via X-ray diffraction and TD-DFT calculations.

AIE-active boron complexes based on benzothiazole-hydrazone chelates.

A new family of aggregation-induced emission (AIE)-active monoboron and bisboron complexes based on benzothiazole-hydrazone chelates was synthesized. These complexes showed very weak fluorescence in fluid solution due to active intramolecular rotation and were emissive in high-viscosity solvents or in the aggregation state. Single crystal X-ray diffraction analyses and theoretical calculations were carried out to explain AIE behavior. The large Stokes shifts (3590-7400 cm-1) and relatively highly efficient solid-state emission make these complexes valuable AIE luminophores for further potential applications.

Synthesis and application of a dual chiral [2.2]paracyclophane-based N-heterocyclic carbene in enantioselective ß-boration of acyclic enones.

An enantioselective conjugate addition of boron to α,ß-unsaturated ketones catalysed by either a N-heterocyclic carbene or a copper-carbene complex generated in situ from a new chiral bicyclic triazolium based on [2.2]paracyclophane is presented. The dual chiral carbene-copper catalyst has significant advantages over its carbene counterpart as an organocatalyst in asymmetric ß-boration of acyclic enones, giving a variety of chiral ß-boryl ketones in good yields and enantioselectivities. This is a successful example of employing the same N-heterocyclic carbene in one catalytic reaction as both an organocatalyst and a ligand for transition metal catalysis.

4-Amino-12-methyl-sulfon-yloxy-[2.2]para-cyclo-phane.

The title compound, C17H19NO3S, was synthesized from 4-benzhydryl-idene-amino-12-hy-droxy-[2.2]para-cyclo-phane and methane-sulfonyl chloride. In the mol-ecule, the distance between the centroids of two aromatic rings is 2.960 (5) Å. In the crystal, weak N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into layers parallel to the ac plane.

AIEE-active dichlorobenzene and chlorobenzene ratiometric fluorescent probe based on [2.2]paracyclophane.

Two AIEE-active [2.2]paracyclophanyl-based diester and monoester (1a and 1b) were facilely synthesized by one-pot method and applied as ratiometric fluorescent probe to detect dichlorobenzene (DCB) and chlorobenzene (CB). Compared with compound 1b, 1a exhibits high sensitivity and low detection limits for DCB and CB in dichloromethane (DCM), particularly, the detection sensitivities for ortho-dichlorobenzene (o-DCB), meta-dichlorobenzene (m-DCB) and chlorobenzene can be modulated by AIEE behavior with lower detection limits of 23.64, 56.27, and 5.92 ppm, respectively in THF/H2O mixed solutions with water fraction (fw) of 70 % due to the formation of aggregation-state. The X-ray structure analysis, theoretical calculations and photophysical properties in different solvents were investigated to reveal the distinctive photophysical behaviors of 1a and 1b. The facile synthesis, X-ray structure, AIEE modulated sensing properties for o-DCB, m-DCB, and CB in DCM and THF/H2O mixed solutions make 1a potential application as fluorescent probe for trace DCB and CB detection in drinking water.

Enantioselective ß-boration of acyclic enones by a [2.2]paracyclophane-based N-heterocyclic carbene copper(I) catalyst.

A new planar and centrally chiral bicyclic 1,2,4-triazolium salt has been synthesized from [2.2]paracyclophane and phenylglycinol. The N-heterocyclic carbene (NHC) copper(I) complex generated in situ by the reaction of the triazolium salt and Cu(2)O was an efficient catalyst for the asymmetric ß-boration of acyclic enones, producing ß-boryl ketones in high yields and enantioselectivities.

Solid-state fluorescence emission and second-order nonlinear optical properties of coumarin-based fluorophores.

Some coumarin-based fluorophores were synthesized and characterized by elemental analysis, (1)H NMR, (13)C NMR and MS. The solid-state photoluminescence properties were studied. The benzocoumarins display interesting solid-state emission properties with an emission at wavelengths ranging from 532 to 645 nm, when excited by a 325 nm helium-cadmium laser at room temperature. The results demonstrated that the luminescent colors can be tuned from green to red by simply varying molecular structure. The benzocoumarin-phenyl boronic acid hybrid, 4-(3-oxo-3-(2 -oxo-2H-1-naphtho[2,1-b]pyran-3-yl)-prop-1-enyl)phenyl boronic acid, showed obvious fluorescence response to water. Whereas the free compound was very weakly fluorescent in tetrahydrofuran (THF), the addition of water leads to an appearance of strong blue-green fluorescence and a dramatic increase of emission intensity. Besides, 3-(3-(3,4,5-trimethoxyphenyl)-prop-2-enoyl)-2H-1-benzopyran-2-one exhibited second order nonlinear optical response to laser pulses. A noticeable second harmonic generation (SHG) under pulsed excitation at 1064 nm was observed. Preliminary nonlinear measurements on powder samples showed that the second harmonic generation efficiency is roughly 5.8 times that of potassium dihydrogen phosphate (KDP).

A robust and porous titanium metal-organic framework for gas adsorption, CO2 capture and conversion.

A robust and porous titanium metal-organic framework (Ti-MOF; LCU-402) has been hydrothermally synthesized through combining a tetranuclear Ti2Ca2(µ3-O)2(µ2-H2O)1.3(H2O)4(O2C-)8 cluster and a tritopic 1,3,5-benzene(tris)benzoic (BTB) ligand. LCU-402 shows remarkable stability and permanent porosity for CO2, CH4, C2H2, C2H4, and C2H6 gas adsorption. Moreover, LCU-402 as a heterogeneous catalyst can smoothly convert CO2 under a simulated flue atmosphere into organic carbonate molecules by cycloaddition reactions of CO2 and epoxides, indicating that LCU-402 might be a promising catalyst candidate in practical applications. We are confident that the identification of a persistent titanium-oxo building unit would accelerate the development of new porous Ti-MOF materials.

5-Benzoyl-13-bromo-4-hy-droxy[2.2]paracyclo-phane.

The title compound, C(23)H(19)BrO(2), was synthesized from 13-bromo-4-hy-droxy[2.2]paracyclo-phane and benzoyl chloride. The hy-droxy and carbonyl groups are involved in intra-molecular O-H⋯O hydrogen bonding. The crystal packing exhibits weak C-H⋯O inter-actions, which link the mol-ecules into sheets parallel to the bc plane.

AIE-active aurones for circularly polarized luminescence and trace water detection.

AIE-active phenyl- and [2.2]paracyclophanyl-based aurones (2-Ph and 2-PCP) were synthesized and investigated with different structures and photophysical properties. The results illustrated that the PCP ring can provide chirality, electron-donating ability and steric hindrance. Accordingly, (Rp)/(Sp)-2-PCP exhibit high sensitivity in trace water detection and aggregation-induced CPL with enhanced quantum yields and luminescence dissymmetry factors.

One-Pot Construction of Heteroarylation/Esterification Products of Acrylic Acids via Iridium(III)-Catalyzed C-H Activation.

A carboxylate-assisted iridium(III)-catalyzed regioselective C(sp2)-H heteroarylation/esterification reaction of acrylic acid is disclosed herein for the first time. This catalytic protocol tolerates various α-substituted, ß-substituted, and α, ß-disubstituted acrylic acids as well as heteroaromatic boronates well. The resulting 3,4-dihydro-2H-pyran-6-carboxylic acid derivative 3r highlighted the AIE-active luminophore with multiple emission signal properties and a high quantum yield of 28%, exhibiting the potential application of this methodology for the synthesis of nitrogen-containing organic functional materials.

Robust acid-base Ln-MOFs: searching for efficient catalysts in cycloaddition of CO2 with epoxides and cascade deacetalization-Knoevenagel reactions.

A family of microporous and robust Ln(iii)-based metal-organic frameworks (1-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) have been obtained using 4,4',4''-nitrilotribenzoic acid (H3NTB) in NMP-HCl solvent. Both single-crystal and powder X-ray diffraction analyses demonstrate that 1-Ln are isostructural and possess 3D frameworks with permanent porosity for Ar and CO2 adsorption. Strikingly, the incorporation of both Lewis acidic lanthanide ions and the basic triphenylamine group into 1-Ln makes them efficient acid-base catalysts for both cycloaddition of epoxides with CO2 and one-pot cascade deacetalization-Knoevenagel reactions. The systematic catalytic studies show that 1-Tb and 1-Yb possess the best catalytic activities for both reactions, indicating the catalytic activities of these Ln-MOFs are strongly dependent on metal Lewis acid sites embedded in the frameworks.

Synthesis of cyclophanes with planar and helical chirality.

Novel helical macrocyclic imines derived from planar chiral [2.2]paracyclophane were synthesized. The chiroptical properties of the enantiopure compounds were investigated and their absolute configurations were assigned.

12,12'-[2,2'-Oxybis(ethane-2,1-di-yl)bis-(-oxy)]bis-[(R(p))-4-bromo-[2.2]paracyclo-phane].

The title compound, C(36)H(36)Br(2)O(3), was synthesized from (R(p))-4-bromo-12-hy-droxy[2.2]paracyclo-phane and oxydiethane-2,1-diyl bis-(4-methyl-benzene-sulfonate). The crystal packing exhibits a short O⋯Br inter-action [Br⋯O = 3.185 (3) Å] and a weak inter-molecular C-H⋯O contact.

Silylative aromatization of p-quinone methides under metal and solvent free conditions.

A base-mediated silylation reaction leading to benzyl silanes has been developed. Under transition-metal and solvent free conditions, the silylation of a wide array of p-quinone methides is achieved using a Cs2CO3 catalyst in yields up to 96%. Carboxylation of the as-obtained organosilane with gaseous CO2 provides a new synthetic protocol for the preparation of carboxylic acid.

Planar chiral [2.2]paracyclophanyl-based boron fluoride complexes: synthesis, crystal structure and photophysical properties.

Planar chiral [2.2]paracyclophanyl-based boron fluoride complexes (3a-3d) were designed and facilely synthesized. The X-ray structure study, theoretical calculations and CD spectra reveal the intense emission and planar chiral structures of these complexes. In particular, 3a-3d show moderate quantum yields and large Stokes shifts both in solution and solid state. Furthermore, the blue-shifted mechanochromic properties of 3a and 3b were both investigated in the solid state. This work is the first study on planar chiral boron monofluoride complexes within the boron fluoride complex field.