In this work, we first found a surprising solvothermal reaction for direct dinitration of quinoline derivative. To explore the application in direct nitroquinoline synthesis, this reaction was subsequently modified as an equivalent reaction in a Schlenk tube. More significantly, after a constant attempt, nitrated derivative was obtained in optimized condition with a zinc(II) sulfate catalyst, where some substrates with strong electron-withdrawing group were first nitrated by a directly catalyzed condition. This new zinc(II)-catalyzed aromatic C–H activation reaction is the first example of direct dinitration by a single catalyst, which will be a new facile and environmentally friendly strategy to access synthetically useful nitroquinoline derivative.

•Benzothiadiazole-pyridine compounds were directly synthesized via a modified amination route.•They show the attracting modulation of optical and nonlinear optical (NLO) performances by molecular polarity feature.•Enhanced NLO molecular capability was connected with the quasi-D-A organic structure.•The switch-on of NLO refraction signaling from negative to positive, was triggered by the external Fe3+ ion.In this work, two new benzothiadiazole (BTD)-based compounds 1 and 2 were elaborately designed and synthesized, to explore the modulation on the interesting optical properties. Briefly, bipyridine-substituted compound 1 was synthesized via a modified Buchwald-Hartwig amination reaction with relatively high yield, and then derivative 2 was prepared by a following dehydrogenation reaction. The result in steady-state spectroscopic analysis and DFT/TDDFT calculation suggest the readily polarized nature of 1. In contrast, the readily polarized nature was declined in π-conjugated molecule 2, indicating the blue-shifted absorption and emission. Interestingly, negative cubic nonlinear refraction behavior in 1 is greater than that in π-conjugated system 2. Furthermore, in case 1 or 2, the photophycal property was considerably influenced by the external transition metal ion (M = Ag+, Cu2+ or Fe3+). Especially, because of the existence of external Fe3+ in case 1, initially negative nonlinear refraction signal became a positive one. Such exciting result is quietly useful for the design and synthesis of new functional BTD-based dye material.Bipyridine-substituted compound 1 was successfully synthesized via the modified Buchwald-Hartwig amination route with relatively high yield in relatively short reaction time. The relatively rigid derivative 2 was subsequently prepared by the simple dehydrogenation. Herein, two new BTD-pyridine compounds 1 and 2 show the attracting modulation of optical capability by the change of molecular polarity feature. In comparison with 1, polarized nature was declined in dehydrogenated 2, indicating the blue-shifted absorption and emission as well as weakened negative cubic nonlinear refraction.

•Two new benzothiadiazole-pyridine compounds were pH-sensitive in broad ranges (2–12).•In live cell imaging experiment, unique “turn-on” fluorescence response to increased pH was firstly observed.•The unique performance was dependent on mitochondrial function under different physiological pH conditions.•The first mitochondria-dependent benzothiadiazole-pyridine probe for cellular pH imaging in quantitative mode.In this work, we reported two new pH-sensitive benzothiadiazole-pyridine compounds 1 and 2, which distinctly showed the red-shifted absorption and “turn-off” fluorescence responses to increased pH in a broad range (pH = 2–12). Because of excllent mitochondria-immobilized preformance, suitable fluorescence detection window and linear response behavior in the range of pH = 5–8, compound 1 was suitable to explore as a imaging detector of intracelluar pH in live cell. More intereastingly, different from “turn-off” fluorescence response to increased pH in buffer solution, probe 1 displayed a “turn-on” fluorescence in live cell imaging experiment. This opposite performance between buffer solution and live cell are so unique that no such literature has been ever mentioned in our best knowledge. The further study revealed that this unique performance was dependent on the mitochondrial function under different physiological pH conditions. Herein, on the basis of special “turn-on” fluorescence response, intracellular pH was successfully imaged in a quantitatively ratiometric method by using 1 in conjunction with MitoTracker Red (MTR).In this paper, we reported the first example for quantitatively intracellular pH probe dependent on mitochondrial function under different physiological pH conditions.Download high-res image (287KB)Download full-size image

The first example of micro-adjustments of a metal organic framework (MOF) structure was observed in a new Zn(II) MOF (Zn-BTDC-M1) derived from a benzothiadiazole-4,7-dicarboxylic acid (H2BTDC) ligand using a light-driven decarboxylation process. Interestingly, such decarboxylation occurs at the non-chelated wing of the ligand, which induced a change in the capability of the MOF for physical N2 adsorption and chemical NH3 gas adsorption.

On the basis of the same benzothiadiazole (BTD) ligand 2,1,3-benzothiadiazole-4,7-dicarboxylic acid (H2L), two new isomers of three-dimensional (3D) BTD-derived Cd(II) metal–organic frameworks 1-2 {[S@Cd6L6]·xH2O}n were obtained by the different solvothermal reactions, which were structurally similar. Surprisingly, structural analyses reveal that in 1 or 2, one free sulfur atom was fixed in a Cd(II) cluster cage by strong intermolecular interaction to form the secondary building unit (SBU) S@Cd6. Each SBU S@Cd6 is connected by six L2– ligands and further extended into the 3D porous framework. In this work, the BTD antidimmer was evidenced by structural analysis and photophysical study. Furthermore, either 1 or 2 showed the uncommon dual emission, while only one emission was observed in the solution of ligand H2L. The dual-emission mechanism was also realized by the structural analysis and photophysical study. Interestingly, although there is slight difference in structure (regular octahedral cage in 1 and slightly distorted octahedral cage in 2), the changes in N2 adsorption capability and photophysical performance between 1 and 2 are obvious, where 2 shows smaller Brunauer–Emmett–Teller surface area, broader absorption of antidimmer, and longer dual-emission lifetimes. Interestingly, either 1 or 2, the dual emission was clearly red-shifted by increasing the solvent polarity or the acidity of ambience, respectively.

Several new isostructural lanthanide metal–organic frameworks {[Ln3(L)4(OH)(H2O)2]·DMAC}n (Ln = Tb (1), Gd (2), Eu (3), Gd0.81Tb0.10Eu0.09 (4) and Gd0.75Tb0.18Eu0.07 (5)) were designed and prepared. Excitingly, samples 1, 3, 4 and 5 showed reversible Al3+-induced chromaticity switching as well as reversible Fe3+-induced emission switching.

To explore new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-derived metal–organic frameworks (MOFs), we employed 2,6-dicarboxyl-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (H2L) as a ligand to successfully synthesize five coordination polymers, namely, {[Zn2(L)2(bpp)]·2H2O·2EtOH}n (1), {[Cd2(L)2(bpp)]·2H2O·EtOH}n (2), {[Cd2(L)(bpe)3(NO3)2]·2H2O·DMF·EtOH}n (3), {[Cd(L)(bpe)0.5(DMF)(H2O)]}n (4), and {[Cd(L)(bpe)0.5]·1.5H2O·DMF}n (5) (bpp = 1,3-bi(4-pyridyl)propane, bpe = 1,2-bi(4-pyridyl)ethane). Except for two 2D-layer coordination polymers 3 and 4, the rest samples exhibit 3D metal–organic frameworks with certain pore sizes, especially MOFs 1 and 5. Spectroscopic and crystallographic investigations demonstrate that the absorption and emission energies of the BODIPY chromophores are sensitive to the coordination modes. Moreover, in case 2, the transition metal centers coordinated with the dicarboxylate ligands L2– are capable of forming the two BODIPY units in coplanar arrangements (θ = 37.9°), simultaneously suppressing the uncommon J-dimer absorption band centered at 705 nm with a long tail into the near-infrared region at room temperature. On the other hand, in comparison with the ligand H2L, the emission of monomer-like BODIPY in case 3 is enhanced in the solid state by a considerably long distance between the parallel BODIPY planes (about 14.0 Å).

To search for effective photocatalysts in the field of cluster-based coordination complexes, we synthesized {[Cd2(dcpp)(beb)2 (H2O)]·H2O}n (1), [Cd2(dcpp)(bmb)(H2O)2]n (2), {[Cd2(dcpp)(2,2′-bipy)(H2O)2]·2H2O}n (3), and {[Cd2(dcpp)(4,4′-bipy)0.5(H2O)3]·H2O}n (4) by utilizing a butterfly-shaped multidentate carboxylic acid (4,5-di(4′-carboxylphenyl)phthalic acid) (H4dcpp)) and N-donor ligands (1,4-bis(2-ethylbenzimidazol-1-ylmethyl) benzene (beb), 1,4-bis(2-methylbenzimidazol-1-ylmethyl) benzene (bmb), 2,2′-bipyridine (2,2′-bipy), 4,4′-bipyridine (4,4′-bipy)). Complexes 1–4 are constructed based on different SBUs. Complexes 1 and 2 possess three-dimensional (3D) pillar-layered frameworks based on noncluster-type SBUs and dinuclear Cd2 clusters units, respectively. Complex 3 is a 3D porous structure building on Cd4 clusters SBUs. Complex 4 is constructed from rare infinite botryoid-like Cd cluster chains and exhibits a 3D complicated framework. The research on optical energy gaps of complexes 1–4 indicates that these complexes are potential semiconductive materials. Moreover, complexes 1–4 are applied to catalyze the reaction of photocatalytic degradation of methylene orange (MO) under high-pressure mercury lamp irradiation. Excitingly, they exhibit good photocatalytic properties in the presence of H2O2, and the degradation rates for 1–4 increase from 43% (without photocatalyst) to 97, 78, 85, and 67%, respectively, after 100 min of irradiation. The photoluminescent properties of complexes 1–4 were also studied.

To systematically explore the effect of polynuclear complexes on photocatalytic degradation of the organic dyes, a series of coordination complexes containing CdII clusters, formulated as {[Cd3L2(H2O)5]·H2O}n (1), {[Cd3L2(hbmb)(H2O)2]·2.5H2O}n (2), {[Cd3L2(btbb)(H2O)2]·2EtOH·1.5H2O}n (3), and {[Cd6L4(bipy)2(H2O)6]·3H2O}n (4) (H3L = 3,4-bi(4-carboxyphenyl)-benzoic acid, hbmb = 1,1′-(1,6-hexane)bis(2-methylbenzimidazole), btbb = 1,4-bis(2-(4-thiazolyl)benzimidazole-1-ylmethyl)benzene, 4,4′-bipy = 4,4′-bipyridine), have been designed and synthesized. Complex 1 based on trinuclear CdII clusters exhibits a new (3,3,6)-connected 3D framework. 2 belongs to a (3,3,8,8)-connected tfz-d topology net with pillar-layered frameworks assembled by two kinds of trinuclear CdII clusters. 3 is a 3D pillar-layered framework, which features a (3,8)-connected tfz-d net based upon one kind of trinuclear CdII cluster. 4 presents a new 3D (3,6,10)-connected framework with dinuclear and tetranuclear clusters. The photocatalytic properties of complexes 1–4 have been studied in detail. Remarkably, 1–4 all reveal good photocatalytic activity in MB/MO degradation. The optical energy gap calculated by the diffuse reflectivity spectra of 1–4 are consistent with their degradation rates. Moreover, the experimental results further demonstrate that the cluster complexes containing different kinds of nuclei may exert different impact on the decomposition of disparate organic dyes.

Tuned by different aromatic polycarboxylates, six fascinating coordination polymers (CPs), namely, [Cd(pbmb)(p-bdc)]n (1), {[Zn3(pbmb)2(1,3,5-btc)2]·6H2O}n (2), {[Cd3(pbmb)3(1,3,5-btc)2(H2O)]·3H2O}n (3), {[Zn2(pbmb)(1,2,3-btc)(μ2-OH)]·H2O}n (4), [Cd(pbmb)(1,2,4,5-btec)0.5]n (5), and {[Cd(pbmb)(sdba)]·2H2O}n (6) (pbmb = 1,1′-(1,3-propane)bis-(2-methylbenzimidazole), p-H2bdc = 1,4-benzenedicarboxylic acid, 1,3,5-H3btc = 1,3,5-benzenetricarboxylic acid, 1,2,3-H3btc = 1,2,3 benzenetricarboxylic acid, 1,2,4,5-H4btec = 1,2,4,5-benzenetetracarboxylic acid, H2sdba = 4,4′-sulfonyldibenzoic acid), have been ideated and synthesized by hydrothermal reaction methods. Structural analyses reveal that complexes 1–3 feature three-dimensional (3D) structures (1: 4-connected 66 topology, 2: (3,4,6)-connected (65·7)(4·62)2(42·66·85·102) topology and 3: (2,3,4)-connected (65·8)2(63)2 topology), and the remaining CPs 4–6 exhibit 2D networks. The thermal stability and powder X-ray diffraction for 1–6 have been investigated as further properties. The optical band gaps are analyzed by diffuse-reflectance UV-vis spectra. Moreover, all of the materials manifest good photocatalytic activities for the degradation of methylene blue (MB) (1: 74%, 2: 41%, 3: 37%, 4: 76%, 5: 46%, 6: 75%, respectively) in water under the irradiation of a high-pressure mercury lamp.

Several new isostructural lanthanide metal–organic frameworks {[Ln3(L)4(OH)(H2O)2]·DMAC}n (Ln = Tb (1), Gd (2), Eu (3), Gd0.81Tb0.10Eu0.09 (4) and Gd0.75Tb0.18Eu0.07 (5)) were designed and prepared. Excitingly, samples 1, 3, 4 and 5 showed reversible Al3+-induced chromaticity switching as well as reversible Fe3+-induced emission switching.