Kun Zou

Polymorphism-dependent and piezochromic luminescence based on molecular packing of a conjugated molecule

Different luminescent single crystals of 2-(anthracen-9-yl)-4,5-diphenyl-1H-imidazole (ADPI) were obtained through the construction of different stacking modes with the aid of intermolecular interactions. Both the fluorescence and the stacking mode of the crystals can be reversibly tuned by mechanical and thermal forces to render ADPI piezochromic, which represents a unique example of reversibly controlled solid emission. The regulation of π–π stacking between the anthracene planes by mechanical and thermal forces is suggested to be the main driving force for the piezochromic character of ADPI.

Structural diversity and fluorescent properties of Zn(II)/Cd(II) coordination polymers with a versatile tecton 2-(carboxymethoxy)benzoic acid and N-donor co-ligands

Four novel Zn(II) and Cd(II) coordination polymers, {[Zn(cmb)(dpa)]·H2O}n (1), {[Zn(cmb)(bpp)]·2.5H2O}n (2), {[Zn(cmb)(bimb)]·3H2O}n (3), and {[Cd2(cmb)2(bimb)]·H2O}n (4) (H2cmb = 2-(carboxymethoxy)benzoic acid; dpa = 4,4′-dipyridylamine; bpp = 1,3-di(4-bipy)propane; bimb = 1,4-bis(imidazol)butane), have been synthesized and characterized by elemental analysis, IR spectra, and X-ray diffraction. Complex 1 exhibits a diamond (dia) framework of four-fold interpenetration (class IIIa). 2 features a rare 1D → 3D polycatenated architecture, which is built from the interlocking of two sets of 1D supramolecular loops running in different directions (almost perpendicular). The 3D crystalline lattice of 3 is constructed through the parallel packing of corrugated 2D 44 (sql) nets. Complex 4 shows a 2D network with the (3,4)-connected (43)2(4 × 104 × 12)(42 × 104) topology, which consists of 1D [Cd(cmb)]n arrays and helical pillars. The results clearly indicate the importance of linking modes of organic ligands and metal centers as well as the auxiliary ligands in the direction of the diverse structures for complexes 1–4. Thermal stabilities and luminescent properties of complexes 1–4 have also been investigated.

Unusual 3D ZnII coordination networks with mixed tetrahedral and square-planar building units: from 2-fold interpenetrating bbf architecture to self-penetrating 86 topological frameworks

Two unusual 4-connected ZnII coordination networks have been successfully constructed from tetrahedral ZnII and square-planar 3,3′,5,5′-azobenzenetetracarboxylate building units with the aid of comparable N-donor bridging spacers [1,3-bis(imidazol)propane and 1,3-bis(imidazol)butane], which direct the distinct 2-fold interpenetrating (64·82)(66)2 (bbf) structure with homochiral double-wall helical tubular motifs and the self-penetrating 86 network, respectively.

Iron-catalyzed C(sp3)–H functionalization of methyl azaarenes: a green approach to azaarene-substituted α- or β-hydroxy carboxylic derivatives and 2-alkenylazaarenes

Bioactive azaarene-substituted lactic acids, β-hydroxy esters, 3-hydroxy-2H-indol-2-ones, and 2-alkenylazaarenes were prepared in moderate-to-excellent yields via C(sp3)–H functionalization of methyl azaarenes with carbonyl compounds in the presence of iron(II) acetate as an inexpensive, nontoxic, efficient catalyst. The application of this atom-, step-economic, and environmentally friendly method was demonstrated by a gram-scale synthesis of 3-[(E)-2-(7-chloroquinolin-2-yl)vinyl]benzaldehyde, a key intermediate of leukotriene receptor antagonist (Montelukast).

Four Zn(II)/Cd(II) coordination polymers derived from isomeric benzenedicarboxylates and 1,6-bis(triazol)hexane ligand: synthesis, crystal structure, and luminescent properties

Four coordination polymers, [Zn(o-bdc)(bth)0.5(H2O)] n (1), [Cd(o-bdc)(bth)0.5(H2O)] n (2), [Zn(m-bdc)(bth)] n (3), and [Cd(p-bdc)(bth) · (H2O)2] n (4) (where o-bdc = 1,2-benzenedicarboxylate, m-bdc = 1,3-benzenedicarboxylate, p-bdc = 1,4-benzenedicarboxylate, and bth = 1,6-bis(triazol)hexane), have been hydrothermally synthesized and structurally characterized. Both 1 and 2 are isostructural, featuring two binodal architectures: (63)(65·8) topology in terms of o-bdc and ZnII/CdII as three- and four-connected nodes. Complex 3 shows a 2-D (4,4) network with the Zn ··· Zn ··· Zn angle of 57.84°, whereas 4 exhibits planar 2-D (4,4) network. These 2-D networks of 3 and 4 are extended by supramolecular interactions, such as CH ··· π/π–π stacking and hydrogen-bonding into 3-D architecture. A structural comparison of these complexes demonstrates that the dicarboxylate building blocks with different dispositions of the carboxyl site play a key role in governing the coordination motifs as well as 3-D supramolecular lattices. Solid-state properties such as photoluminescence and thermal stabilities of 1–4 have also been studied.

The H+K+-ATPase inhibitory activities of Trametenolic acid B from Trametes lactinea (Berk.) Pat, and its effects on gastric cancer cells

Trametenolic acid B (TAB), the bioactive component in the Trametes lactinea (Berk.) Pat, was reported to possess cytotoxic activities and thrombin inhibiting effects. This study was performed to investigate the effects of TAB on H(+)/K(+)-ATPase and gastric cancer. The H(+)/K(+)-ATPase inhibitory activity was determined by gastric parietal cells. Compared to the normal control group, TAB (10, 20, 40 and 80 μg/mL) inhibited the H(+)/K(+)-ATPase activity by 15.97, 16.96, 24.86 and 16.25%, respectively. In the study, 36 Kunming mice were randomly divided into six groups: control, model, TAB-L (TAB, 5 mg/kg/day, i.g.), TAB-M (TAB, 20 mg/kg/day, i.g.), TAB-H (TAB, 40 mg/kg/day, i.g.) and omeprazole (OL, 10 mg/kg/day, i.g.). All mice except the control group were administrated with anhydrous alcohol (5.0 mL/kg, i.g.) for induced gastric-ulcer 1h after the 5th day. At the same time, the control mice were given the same volume of physiological saline. After 4h, TAB was evaluated for H(+)/K(+)-ATPase inhibitory activities of ulcerative gaster, gastric ulcer index and ulcer inhibition. In vitro, the anti-proliferation effect of TAB to gastric cancer cell (HGC-27) in acid environment was detected by MTT, and the apoptosis morphological changes were also observed by Hoechst 33258 dye assay. The results indicated that TAB inhibited moderately H(+)/K(+)-ATPase activity in vitro. Compared to the model group, TAB showed anti-ulcer effects in gastric tissue with the dosages of 20 and 5 mg/kg in vivo. Apart from that, TAB could selectively inhibit gastric cancer cell viability and reduce cell apoptosis against HGC-27 cells at low doses in acid environment.

Synthesis, crystal structures, and photophysical properties of dibromo-2-(2′-pyridyl)imidazole and its corresponding boron–fluorine complex

2-(2′-Pyridyl)imidazole L1 and its corresponding boron–fluorine complex, 1, were synthesized and their crystal structures correlated with their photophysical properties. L1 forms a rigid supramolecular network through hydrogen bonds and halogen bond in the single crystal, which induces amplified spontaneous emission in crystals; it emits rather poor fluorescence in solution and powder states. Its boron chelate 1 emits intense fluorescence in solution since boron chelate is an excellent chromophore, and it exhibits large Stokes shift (136 nm in acetonitrile), due to the charge-transfer transition from the electron-donating π system to the electron-accepting boron moiety. Interestingly, 1 is also highly fluorescent in amorphous powder and crystal states; C–C rotation between pyridyl and imidazole groups is inhibited by the formation of a five-member ring containing BF2, and the formation of intermolecular non-covalent bonds is the key factor. Solid emission with large Stokes shift makes it a valuable chromophore for synthesis of functional materials.

Trametenolic Acid B Reverses Multidrug Resistance in Breast Cancer Cells Through Regulating the Expression Level of P‐Glycoprotein

Trametenolic acid B (TAB) is the main active composition of Trametes lactinea (Berk.) Pat which possesses anti‐tumor activities. There was no report its antitumor effect through regulating P‐glycoprotein (P‐gp) so far, due to P‐gp over expression is one of the most important mechanisms contributing to the multiple drug resistance phenotype. The present aim was to investigate the effects of TAB on P‐gp in multidrug‐resistant cells; Paclitaxel‐resistant cell line MDA‐MB‐231/Taxol was established by stepwise exposure for 10 months. MDA‐MB‐231 cells and MDA‐MB‐231/Taxol cells were treated with TAB, and their growth was evaluated using MTT assays. Paclitaxel accumulation in the cells was analyzed by high performance liquid chromatogram (HPLC). The activity of P‐gp was detected by intracellular accumulation of rhodamine123 (Rho123), and the protein expression of P‐gp was evaluated using western blot. Results indicated that the IC50 of MDA‐MB‐231/Taxol to paclitaxel (Taxol) was 33 times higher than that of nature MDA‐MB‐231. TAB increased the intracellular concentration of Taxol and inhibited the activity of P‐gp and suppressed the expression of P‐gp in MDA‐MB‐231/Taxol cells. Our present results showed that TAB could reverse Taxol resistance in MDA‐MB‐231/Taxol cells, mainly inhibiting the activity of P‐gp and down‐regulating the expression level of P‐gp, and then enhancing the accumulation of chemotherapy agents.

Solid-emissive rhodamine: hydrogen bonding-assisted efficient intermolecular fluorescence resonance energy transfer in the solid state

Solid-emissive rhodamine complexes are obtained by mixing commercial rhodamine B (RhB) with the recently developed solid-emissive boron 2-(2′-pyridyl)imidazole (BOPIM) derivatives. The formation of intermolecular hydrogen bonds between RhB and BOPIM dyes plays a key role in the emission of RhB in the solid state. The disappearance of emissions from BOPIM dyes indicates the occurrence of efficient intermolecular fluorescence resonance energy transfer (FRET). The hydrogen bond also helps prevent the intermolecular interaction between the carboxyl moieties on RhB to alleviate concentration-induced fluorescence quenching because the emission of the complexes can be directly lightened by excitation at the RhB absorption (510 nm). Our results indicate that intermolecular FRET assisted by non-covalent interactions can be an efficient tool for constructing red or near-infrared solid emitters.

Fluorescent labeling of oleanolic acid using ‘click’ chemistry

Abstract The natural product oleanolic acid (OA) was functionalized and labeled with the non-aggregated fluorescent dye BOPIM (boron 2-(2′-pyridyl)imidazole complex) using ‘click’ chemistry, yielding a highly fluorescent probe. The pharmacological activity of the probe is comparable to that of unmodified OA, making it suitable for studying the therapeutic mechanisms of OA derivatives in vitro.