Spin-Canting Magnetization in an Unusual Co₄ Cluster-Based Layer Compound from a 2,3-Dihydroxyquinoxaline Ligand

The self-assembly of Co­(O₂CPh)₂ with a 2,3-dihydroxyquinoxaline (H₂dhq) linker has revealed a new two-dimensional cluster-based compound, [Co₄(OMe)₂(O₂CPh)₂(dhq)₂(MeOH)₂]_<i>n</i>, which shows spin-canted magnetization and a definite magnetic hysteresis loop

Direct Guest Exchange Induced Single-Crystal to Single-Crystal Transformation Accompanying Irreversible Crystal Expansion in Soft Porous Coordination Polymers

Two flexible porous coordination materials, [Mn­(pybimc)₂]­·2H₂O·G (G = toluene, <b>1</b>_<b>tol</b>; THF, <b>1</b>_<b>thf</b>), where pybimc = 2-(2′-pyridyl)-benzimidazole-5-carboxylate, featuring identical one-dimensional chain structure have been characterized. Guest exchange studies have exhibited that <b>1</b>_<b>tol</b> cannot be converted to <b>1</b>_<b>thf</b> through direct replacement of guest toluene molecules by THF molecules, but, of particular interest, <b>1</b>_<b>thf</b> is actually converted to <b>1</b>_<b>tol</b> and <b>1</b>_{<b>aromatic</b>} (where aromatic = <i>o</i>-, <i>m</i>-, <i>p</i>-xylene) upon the exchange of THF to toluene and other aromatic molecules, respectively. This signifies a single-crystal to single-crystal transformation accompanied irreversible crystal expansion. In-depth analyses reveal that the nature of the weak yet sufficiently strong framework–guest C–H···π interactions, rather than the guest size, observed in this system plays a key role in guiding the adsorption of liquid-phase aromatics in the soft crystalline materials

Aggregation-Induced Emission Enhancement in Alkoxy-Bridged Binuclear Rhenium(I) Complexes: Application as Sensor for Explosives and Interaction with Microheterogeneous Media

The aggregation-induced emission enhancement (AIEE) characteristics of the two alkoxy-bridged binuclear Re­(I) complexes [{Re­(CO)₃(1,4-NVP)}₂(μ₂-OR)₂] (<b>1</b>, R = C₄H₉; <b>2</b>, C₁₀H₂₁) bearing a long alkyl chain with 4-(1-naphthylvinyl)­pyridine (1,4-NVP) ligand are illustrated. These complexes in CH₂Cl₂ (good solvent) are weakly luminescent, but their intensity increased enormously by almost 500 times by the addition of poor solvent (CH₃CN) due to aggregation. By tracking this process via UV–vis absorption and emission spectral and TEM techniques, the enhanced emission is attributed to the formation of nanoaggregates. The nanoaggregate of complex <b>2</b> is used as a sensor for nitroaromatic compounds. Furthermore, the study of the photophysical properties of these binuclear Re­(I) complexes in cationic, cetyltrimethylammonium bromide (CTAB), anionic, sodium dodecyl sulfate (SDS), and nonionic, <i>p-tert</i>-octylphenoxypolyoxyethanol (TritonX-100, TX-100), micelles as well as in CTAB–hexane–water and AOT–isooctane–water reverse micelles using steady-state and time-resolved spectroscopy and TEM analysis reveals that the nanoaggregates became small and compact size

Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light-emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting due to its low-power consumption and longer lifetime. Nowadays, the practical white LEDs (WLED) are contingent on the photon down-conversion of phosphors containing rare-earth elements, which limits its utility, energy, and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal–organic framework (MOF), {[Sr­(ntca)­(H₂O)₂]·H₂O}_<i>n</i> (<b>1</b>), graphene, and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid-state lighting

Electrically Driven White Light Emission from Intrinsic Metal–Organic Framework

Light-emitting diodes (LEDs) have drawn tremendous potential as a replacement of traditional lighting due to its low-power consumption and longer lifetime. Nowadays, the practical white LEDs (WLED) are contingent on the photon down-conversion of phosphors containing rare-earth elements, which limits its utility, energy, and cost efficiency. In order to resolve the energy crisis and to address the environmental concerns, designing a direct WLED is highly desirable and remains a challenging issue. To circumvent the existing difficulties, in this report, we have designed and demonstrated a direct WLED consisting of a strontium-based metal–organic framework (MOF), {[Sr­(ntca)­(H₂O)₂]·H₂O}_<i>n</i> (<b>1</b>), graphene, and inorganic semiconductors, which can generate a bright white light emission. In addition to the suitable design of a MOF structure, the demonstration of electrically driven white light emission based on a MOF is made possible by the combination of several factors including the unique properties of graphene and the appropriate band alignment between the MOF and semiconductor layer. Because electroluminescence using a MOF as an active material is very rare and intriguing and a direct WLED is also not commonly seen, our work here therefore represents a major discovery which should be very useful and timely for the development of solid-state lighting

Rhenium-Based Molecular Trap as an Evanescent Wave Infrared Chemical Sensing Medium for the Selective Determination of Amines in Air

An evanescent wave infrared chemical sensor was developed to selectively detect volatile amines with heterocyclic or phenyl ring. To achieve this goal, a rhenium-based metallacycle with a “molecular-trap” structure was designed and synthesized as host molecules to selectively trap amines with heterocyclic or phenyl ring through Re–amine and π–π interactions. To explore the trapping properties of the material, a synthesized Re-based molecular trap was treated on an IR sensing element, and wide varieties of volatile organic compounds (VOCs) were examined to establish the selectivity for detection of amines. Based on the observed IR intensities, the Re-based molecular trap favors interaction with amines as evidenced by the variation of absorption bands of the Re molecular trap. With extra π–π interaction force, molecules, such as pyridine and benzylamine, could be detected. After optimization of the parameters for IR sensing, a rapid response in the detection of pyridine was observed, and the linear ranges were generally up to 10 mg/L with a detection limit around 5.7 μg/L. In the presence of other VOCs, the recoveries in detection of pyridine were all close to 100%

Presynthesized and In-Situ Generated Tetrazolate Ligand in the Design of Chiral Cadmium Coordination Polymer

In contrast to the in-situ generated 5-(4-pyridyl)­tetrazolate (4-ptz) ligand, the use of presynthesized 4-ptz led to the formation of a chiral cadmium coordination polymer with a rare μ₅-bridging mode of the tetrazolate ligand. This type of tuning in the design of chiral coordination polymers is reported for the first time

Presynthesized and In-Situ Generated Tetrazolate Ligand in the Design of Chiral Cadmium Coordination Polymer

In contrast to the in-situ generated 5-(4-pyridyl)­tetrazolate (4-ptz) ligand, the use of presynthesized 4-ptz led to the formation of a chiral cadmium coordination polymer with a rare μ₅-bridging mode of the tetrazolate ligand. This type of tuning in the design of chiral coordination polymers is reported for the first time

Porous Metal–Organic Frameworks with Multiple Cages Based on Tetrazolate Ligands: Synthesis, Structures, Photoluminescence, and Gas Adsorption Properties

Three tetrazolate-based coordination polymers [Mn­(TzA)­(H₂O)₂]_<i>n</i> (<b>1</b>, H₂TzA = 1<i>H</i>-tetrazole-5-acetic acid), {[Cd₅(MTz)₉]<b>·</b>OH}_<i>n</i> (<b>2</b>, MTz = 5-methyltetrazolate), and [Cd₃(MTz)₃Cl₃]_<i>n</i> (<b>3</b>) were synthesized via the reactions of a tetrazole ligand H₂TzA with metal ions under hydrothermal conditions. During the formation of <b>2</b> and <b>3</b>, Cd­(II) ions were coordinated by MTz^–, which was generated as the result of the in situ decarboxylation of the H₂TzA ligand. Single-crystal X-ray diffraction analyses revealed that <b>1</b> possessed an infinite 2D layer structure with a μ₃-TzA^2– moiety, forming a 4⁴-<b>sql</b> topology, and the 2D sheets were further hydrogen-bonded to form a 3D framework. Compound <b>2</b> had a 3D porous framework with a 4⁹_<b>·</b>6⁶-<b>acs</b> topology. Compound <b>3</b> adopted a 3D porous framework with a body-centered cubic (<b>bcu</b>) topology, which was comprised of 48-membered (Cd₂₄Cl₂₄) rings, and it demonstrated a moderate adsorption of H₂ over N₂ as a result of its limited window size. The solid-state luminescent properties of complexes <b>2</b> and <b>3</b> and the corresponding HMTz molecule were also investigated

Correlation of Mesh Size of Metal–Carboxylate Layer with Degree of Interpenetration in Pillared-Layer Frameworks

Two porous cobal–organic frameworks showing threefold interpenetration of pillared-layer structures, constructed from two-dimensional (2D) neutral metal–carboxylate layers and neutral bis-pyridyl-bis-amide pillars, were hydro­(solvo)­thermally synthesized and structurally characterized by single-crystal X-ray diffraction. Compound {[Co₂(thdc)₂(bpda)₂(DMF)]·2DMF}_<i>n</i> (<b>1</b>, thdc = 2,5-thiophenedicarboxylate; bpda = <i>N,N</i>′-bis­(4-pyridinyl)-1,4-benzenedicarboxamide) adopts a uninodal 6-connected three-dimensional (3D) framework with a {4¹²·6³}-<b>pcu</b> topology in which 2D rhomboid-like 4⁴-<b>sql</b> Co–thdc layers are pillared by bpda ligands. While compound {[Co₃(btc)₂(bpda)₃]·2DMF·9H₂O}_<i>n</i> (<b>2</b>, btc = 1,3,5-benzenetricarboxylate) is composed of a binodal (3,4)-connected 3D framework with a (6³)₂(6⁴·8·10)₃ topology that can be described in terms of two building subunitsa 2D porous honeycomb-like 6³-<b>hcb</b> Co–btc layer and a bpda pillar. An in-depth analysis showed that the mesh size of the metal–carboxylate layer, in addition to the pillar length, is highly correlated with the degree of interpenetration in the pillared-layer framework. The structural characteristics of frameworks <b>1</b> and <b>2</b> fully support this relationship