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A series of Fe(III) complexes [Fe(5-F-sal-N-1,4,7,10)]Y (Y = PF6- for 1, Y = ClO4- for 2, Y = I- for 3 and Y = NO3- for 4) have been prepared. Single-crystal X-ray crystallographic studies show that complex 1 crystallizes in the orthorhombic Pna21 space group and complexes 2-4 have an isomorphous structure and crystallize in the same monoclinic space group, P21/n. Complexes 2-4 have two independent molecules (Fe1 and Fe2) in the unit cell. Magnetic susceptibility measurements demonstrated that complexes 1 and 3 showed a gradual one-step SCO behavior (T1/2 for 1 = 177 K and for 3 = 227 K) without thermal hysteresis. The magnetic behavior of 2 shows an incomplete two-step SCO process at T1/2 = 114 K and 170 K, respectively, while 4 is in a high-spin state at all measured temperatures. A careful evaluation of the supramolecular structures of these complexes revealed correlation between the supramolecular packing forces and their SCO behavior. The crystal structure of 1 consists of a three-dimensional (3D) extended network constructed from N-H⋯F and C-H⋯F hydrogen bonds, and C-H⋯π and C⋯C short contacts. In compounds 2-4, the crystal packing is governed by C⋯C, C-H⋯π and p-π interactions for the Fe1 centers and by C-H⋯π/O interactions for the Fe2 centers, which form 1D chains. Additional interactions (C-H⋯F and N-H⋯O/I) connect the neighboring chains and planes to form a complex supramolecular network. The anion⋯π interactions in 4 provide a means for preventing SCO occurring at low temperatures. This suggests that the supramolecular connectivity of the anions influences the magnetic properties.

We use a two-stage hierarchical growth method to encapsulate the blue KSN and yellow RhB molecules into a MOF crystal. By aligning these two conjugate plane-structured molecules in the MOF channel, a polarised white-light emission is obtained, with CIE coordinates of (0.3285, 0.3204) and a polarization ratio of 2.98.

Nine coordination polymers (CPs) [Mn(H3L)(H2L)0.5(phen)]n (1), [Ni2L(phen)2(μ2-H2O)]n (2), {[Mn2L(phen)2]·(DMA)(H2O)}n (3), {[Co2L(μ2-H2O)(μ2-DMA)]·DMF}n (4), [CoL0.5(H2O)(phen)]n (5), {[Ni2L(μ2-H2O)(μ2-DMA)]·DMA}n (6), {[Co2L(μ2-H2O)(μ2-DMA)]·DMA}n (7), {[Ni2L(μ2-H2O)(H2O)2(DMF)2]·(H2O)2(DMF)}n (8), and {[Ni4L2(μ2-H2O)4(H2O)2]·(H2O)2(NMP)}n (9) (H4L = 1,1′:4′,1′′-terphenyl-2′,4,4′′,5′-tetracarboxylic acid, DMA = N,N-dimethylacetamine, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone, phen = 1,10-phenanthroline) have been synthesized and structurally characterized. Crystal structural analyses reveal that 1 features the uninodal 2D (4,4) network with the dinuclear Mn2(COO)2 units as 4-connected nodes. 3 and 5 possess the binodal 2D (4,4) network with dinuclear Mn2(COO)4/Co2O2 units and L4− ligands as 4-connected nodes, respectively. In 2 and 8, each dinuclear Ni2(COO)2(μ2-H2O) unit links to four L4− ligands and each L4− ligand bridges four dinuclear Ni2(COO)2(μ2-H2O) units to generate the 3D framework, which can also be rationalized as a binodal 4,4-connected (42·84)(42·84) topological network by considering the dinuclear Ni2(COO)2(μ2-H2O) units as non-planar 4-connected nodes and L4− ligands as planar 4-connected nodes, respectively. In 4, 6–7 and 9, there exist a series of parallel-aligned metal-carboxylate chains, which are linked along two directions by para-terphenyl moieties of L4− ligands to generate the 3D frameworks. Moreover, direct current magnetic susceptibility measurements were carried out to study their magnetic properties. In complexes 2 and 9, weak ferromagnetic interactions between the magnetic centers were observed. In addition, the other compounds show weak antiferromagnetic exchange interactions between the adjacent metal ions.

Fast and selective detection of heavy metal ions in the aqueous phase plays a key role in meeting human health and environmental concerns. Herein we report a series of fluorene-based lanthanide metal–organic frameworks ([Ln2(FDC)3DMA(H2O)3]·DMA·4.5H2O, Ln = Sm (1), Eu (2), Gd (3) and Tb (4), H2FDC = 9,9-dimethyl-2,7-fluorenedicarboxylic acid, DMA = dimethylacetamide). Single crystal X-ray diffraction reveals that 1–4 are isostructural and display a 3D neutral framework. 2 exhibits intense characteristic red emission of Eu3+ ions in the solid state and high selectivity for Pb2+ and Fe3+ ions through fluorescence enhancement and the quenching effect in aqueous solutions, respectively. Interestingly, the fluorescence intensity of 2 shows a good linear relationship with Pb2+ concentration in the range of 0.02–0.1 mM. Furthermore, the dynamic and static quenching constants are calculated to be 320 M−1 and 10 680 M−1 by the fluorescence lifetime and titration experiments in low concentration of Fe3+. In addition, 4 exhibits different fluorescence response behaviors in the presence of Sm3+ or Eu3+ in aqueous solution.

A surfactant and substrate synergetic chemical solution technique was promoted to synthesize uniformly shaped MOF nanodisks. The hexaprismatic nanodisks of {[Eu2(MFDA)2(HCOO)2(H2O)6]·H2O}n (Eu-MFDA_HND, H2MFDA = 9,9-dimethyl fluorene-2,7-dicarboxylic acid) were obtained on a supported substrate in the presence of sodium dodecyl sulfate. The surfactant and substrate worked together to produce the uniform hexaprismatic shaped products, but in contrast, mixed products of defected hexaprisms and irregular nanoparticles were obtained without the substrate. Also, the dehydrated Eu-MFDA_HND crystals showed a much higher fluorescence quenching efficiency towards 2,4-DNT as compared to their corresponding bulk crystals. This effective morphology-scissoring technique may help the shape control of other functional MOF materials and benefit their application in the fields of catalysis, sensing, optoelectronic microdevices, micromechanical devices, etc.

Silicon-containing ultrahigh-energy gap hosts (UGHs) have emerged as important candidates of high-performance host materials with high thermal stability and triplet energy for blue phosphorescent organic light-emitting diodes (PhOLEDs). However, the highest occupied molecular orbital (HOMO) of these UGHs are generally too deep to support balanced hole injection and transportation in devices. Here, we propose a new design strategy of UGHs by multiple introduction of strong electron-donating and high-triplet-energy units of carbazoles into the electron-accepting arylsilanes in the N–Si–N structure. The facilely synthesized carbazole-arylsilanes in one-step show high thermal stability, triplet energy and charge mobilities with high-lying HOMOs due to enhanced σ–π conjugation in the N–Si–N structure as revealed by combined experimental and theoretical investigations. Impressively, blue PhOLEDs hosted by these novel N–Si–N bonded UGHs exhibit an improved maximum current efficiency up to 39.5 cd A−1, a power efficiency of 27.4 lm W−1, and an external quantum efficiency of 24.2%, demonstrating significant advances in the design of UGHs by adjusting the d-orbital participation of π-conjugation to enhance the σ–π conjugation in donor (D)–acceptor (A) molecular architectures.

In this study, we developed two new strong orange-emission and thermally stable iridium complexes, IrCzPPya {tris[9-(6-phenylpyridazin-3-yl)-9H-carbazole]iridium(III)} and IrNPPya [tris(N,N,6-triphenylpyridazin-3-amine)iridium(III)] by introducing a hole transporting moiety to the C∧NN type ligand, i.e. carbazole and diphenylamine. Based on experimental results plus quantum chemistry calculations, the link between molecular structures and material properties was demonstrated. Using IrNPPya as the dopant emitter, the organic light-emitting device (OLED) showed extremely high efficiency of 70.8 cd A−1 (75.4 lm W−1, 30.8%) with wavelength up to 560 nm. More importantly, the efficiency was still as high as 63.3 cd A−1 (43.5 lm W−1, 21.8%) at a brightness of 1000 cd m−2, showing very low efficiency roll-off. By combining IrNPPya with the blue emitter FIrpic [bis(4,6-difluorophenyl-pyridinato-N,C2′)(picolinate)iridium(III)], a single emissive-layer white OLED (WOLED) with high efficiency and good Commission Internationale de l'Eclairage (CIE) coordinates was successfully constructed. The device achieved maximum efficiencies of 55.9 lm W−1, 49.9 cd A−1, and 23.9% with CIE coordinates of (0.33, 046), which are among the best with similar CIE coordinates. The strategies for obtaining high efficiency WOLED with simple three organic layers were highlighted.

We report a flexible metal-organic framework (MOF), (Me2NH2)(3)[ Eu-3(MHFDA)(4)(NO3)(4)(DMF)(2)]center dot 4H(2)O center dot 2MeCN (1) (H(2)MHFDA = 9-methyl-9-hydroxy-fluorene-2,7-dicarboxylic acid), which was synthesized by a hydrothermal method and structurally characterized. This MOF has a three-dimensional framework structure with one-dimensional rhombic channels and the framework can be reversibly transformed between two phases upon release/uptake of the guest molecules. The vacuum drying process is accompanied by the loss of luminescence of the MOF, while the luminescence is recovered upon resoaking in DMF. The potential of the material for PA sensing was studied in DMF through the luminescence quenching experiments, which elucidate that this material is a potential turn-off luminescent sensory material for the selective detection of PA.

A series of ternary asymmetric triazines with tunable singlet and triplet excited states were successfully synthesized on the basis of σ-spacer methodology and a facile synthetic route. The optoelectronic properties are dominated by the conjugated donor–acceptor (D–A) backbone of peripheral carbazoles (D) and triazine core (A), and can be further modulated via the partially interrupted conjugation between the core and the third substituents by the σ spacers of N–CH3, NH, O, S and OSO, which offers new opportunities to fine tune the electronic structures and properties of triazines.

A metal-organic framework (MOF) {[Eu2(MFDA)2(HCOO)2(H2O)6]·H2O}n (1) (H2MFDA = 9,9-dimethylfluorene-2,7-dicarboxylic acid) has been solvothermally synthesized and structurally characterized. 1 possesses the three-dimensional pcu type rod-packing structure with one-dimensional rhombic channels. The framework of 1 can reversibly shrink/swell along the c axis upon partial/full release of the water molecules. Correspondingly, the rhombic channels become narrow/large and 1 transforms to narrow-pore 1a/large-pore 1b. 1, 1a and 1b have almost the same excitation and emission spectra with the strong characteristic red-light-emission of Eu(III). A high photoluminescence quantum yield of 77% and long luminescence lifetime of around 1.1 ms was observed for 1. The potential of 1b for Fe(3+) ions and PA sensing was studied in DMF through the luminescence quenching experiments, which show 1b is a potential turn-off luminescent sensory material for the selective detection of Fe(3+) ions and PA with detection limits of around 10(-7) M for both of them. The fluorescence quenching mechanism for Fe(3+) ions and PA was also investigated.

An anthracene carboxamide derivative of the excited-state intramolecular proton-transfer compound of 2-(2'-hydroxyphenyl)benzothiazole has been newly developed to produce the prominent characteristics of aggregation-induced enhanced emission (AIEE) with a high solid-state fluorescence quantum efficiency of 78.1%. Compared with our previously reported phenyl carboxamide derivatives, a small tailoring of the molecular structure was found to result in a big difference in the dominant factor of the AIEE mechanism. In the phenyl carboxamide derivatives, the dominant factor of the AIEE mechanism is the restriction of the twisted intramolecular charge transfer (TICT) of the enol excited state, regardless of their different aggregation modes. In the anthracene carboxamide derivative, N-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl) anthracene-9-carboxamide, the AIEE characteristics are not dependent on the restriction of TICT, but mainly attributed to the cooperative effects of J-aggregation and the restriction of the cis-trans tautomerization in the keto excited state. A specific N···π interaction was found to be the main driving force for this J-aggregation, as revealed by the single crystal analysis. The AIEE mechanism of this anthracene carboxamide derivative was studied in detail through photophysical investigations and theoretical calculations. On the basis of its AIEE characteristics, a stable non-doped organic light-emitting diode was achieved, with high color purity and a remarkably low efficiency roll-off.

A series of Pt(II) complexes with different N⁁O ligands have been synthesized and characterized by NMR, mass spectroscopy, and X-ray diffraction studies. All complexes are non-emissive in dilute solution. Interestingly, they exhibit aggregation-induced phosphorescent emission (AIPE) with an absolute quantum efficiency of up to 38% in the crystal state. In addition, their AIPE properties can be tuned significantly by changing the chemical structures of N⁁O ligands. Furthermore, an AIPE mechanism of “restricted distortion of excited-state structure (RDES)” was proposed through experimental and theoretical investigations, which provided a rational design strategy for metallophosphors with tunable aggregation-induced phosphorescent emission. Considering their excellent emissive properties in aggregation state, the promising applications of these AIPE-active Pt(II) complexes in time-resolved luminescence assay utilizing the long emission lifetime of phosphorescent signal and targeted luminescence imaging of cancer cells have been demonstrated.

A series of square-planar Pt(II) complexes [Pt(C^N)(O^O)] (1–5) (C^N = 2-phenylpyridine, O^O denotes a series of β-diketonate ligands) is reported. Detailed studies of theoretical calculations, electrochemical and photophysical properties have shown that their excited states can be attributed to the mixing of 3MLCT, 3LLCT and 3LC/3ILCT transitions. For 1, the excited state is dominated by the C^N ligand. The excited states of complexes 2–5, however, are dominated by O^O ligands. Through variation of the β-diketonate ligands, the emission colors of 1–5 can be tuned from blue-green to yellow. Further investigations have revealed that the emission of 4 in the solid state can be attributed to the 3MLCT and 3LLL'CT transitions, which has been confirmed by X-ray diffraction studies as well as theoretical calculations. Moreover, exclusive staining of cytoplasm and low cytotoxicity have been observed for 1–4, which makes them promising candidates as phosphorescent probes for bioimaging.

Three new coordination polymers with 1,2,3-triazolate ligands, [Cd3(ta)3Cl3]n (1), {[Cd3(ta)6]·6H2O}n (2) and [Cu6(ta)3I3]n (3) (Hta = 1,2,3-triazole), have been hydrothermally synthesized and structurally characterized. In complex 1, the Cd2+ and Cl− ions form a 3D [(Cd3Cl3)3+]n inorganic framework with (82.12)(4.8.10) topology while the Cd2+ ions and ta− ligands give a {[Cd3(ta)3]3+}n double helical chain. The two moieties are fused with each other by sharing “hinge” Cd2+ ions leading to a 3D organic–inorganic hybrid structure. The 3D porous metal–organic framework of complex 2 shows the topology of the diamond net with the Cd-centered CdCd4 tetrahedron units as the connecting nodes. The desolvated structure of 2 has 48% solvent accessible space of the total volume. Complex 3 is an undulating 1D organic–inorganic hybrid complex consisting of interesting discrete five-capped [Cu6I5]− triangular prism clusters and arched metallacycle [Cu6(ta)6I]+ moieties.

Three N,N-bidentate ligands, 5,5'-dibromo-2,2-bipyridine (L1) and two carbazole containing ligands of 5-bromo-5'-carbazolyl-2,2-bipyridine (L2), 5,5'-dicarbazolyl-2,2'-bipyridine (L3), and their corresponding rhenium Re(CO)3Cl(L) complexes (ReL1-ReL3) have been successfully synthesized and characterized by elemental analysis, 1H NMR and IR spectra. Their photophysical properties and thermal analysis, along with the X-ray crystal structure analysis of L3 and complexes ReL1 and ReL3 are also described. In CH2Cl2 solution at room temperature, all complexes display intense absorption bands at ca. 220-350 nm, which can be assigned to spin-allowed intraligand (pi-->pi*) transitions, and the low energy broad bands in the 360-480 nm region are attributed to the metal to ligand charge-transfer d(Re)-->pi* (diimine) (MLCT). The introduction of carbazole moieties improves the MLCT absorption and molar extinction coefficient of these complexes. Upon excitation at the peak maxima, all complexes show strong emissions around 620 nm, which are assigned to d(Re)-->pi* (diimine) MLCT phosphorescence. The photoluminescence lifetime decay of Re(I) complexes were measured and the quantum efficiencies of the rhenium(I) complexes were calculated by using air-equilibrated [Ru(bpy)3]2+ x 2 Cl- aqueous solution as standard (phi(std) = 0.028). The complexes with appended carbazole moieties exhibit enhanced luminescence performances relative to ReL1.

Six three-dimensional nanoporous lanthanide coordination polymers, [Ln2(bpdc)3(HCOOH)2]n [Ln = Eu (1), Sm (2), La (3), Ce (4), Gd (5) and Nd (6)], were prepared by the solvothermal reactions of the LnIII ions with 4,4′-biphenyldicarboxylate (H2bpdc) in DMF solution. Crystallographic data show that compounds 1–6 are isomorphous and crystallize in monoclinic, space groupC2. Each LnIII is eight-coordinated to seven O atoms from six bpdc2− ligands and one O atom from HCOOH molecule in distorted bisdisphenoid coordination geometry. The adjacent LnIII ions are intraconnected by the carboxylate groups of the bpdc2− ligands to form a 1D inorganic rod-shaped chain [Ln(CO2)3]n. The inorganic chains are interconnected by the biphenyl groups, giving rise to a 3D framework that consists in two types of 1D open channels, with 15.11 × 27.05 A rhombic channels along the b axis and 8.66 × 15.91 A quadrate channels along the c axis without interpenetration. Compounds 1 and 6 are strong luminescent materials which exhibit characteristic EuIII emission bands in the visible region for 1 and NdIII emission bands in the near IR region for 6 upon excitation at 360 nm. The absence of the ligand emission can be ascribed to the energy transfer from the bpdc2− ligand to the LnIII ion during photoluminescence. The magnetic properties of compounds 1, 4, 5 and 6 have been investigated through the measurement of their magnetic susceptibilities over the temperature range of 1.8–300 K.