Guest-Triggered Aggregation-Induced Emission in Silver Chalcogenolate Cluster Metal-Organic Frameworks

Utilizing aggregation-induced emission luminogens (AIEgens) as ligands has proven to be an effective strategy for constructing metal-organic frameworks (MOFs) with intense luminescent properties. However, highly luminescent AIEgen-based MOFs with adjustable emission properties are rarely achieved because of the rigid conformation of AIEgens in the crystalline state. Here, a dual-node 3D silver chalcogenolate cluster MOF (1) is designed and synthesized, where the AIE ligand shows relatively flexible and rotatable conformations. The conformations of AIE ligands in 1 are switchable by the absorption/desorption of guest molecules. As a result, 1 exhibited not only intense but also guest molecule switched luminescent properties. More importantly, the switching rate is tunable by using different guest molecules. 1 provides a unique visualized prototype to understand the mechanism of guest-triggered aggregation-induced emission in MOFs.

Tellurium-bridged manganese carbonyl clusters: synthesis and structural transformations of [Te4Mn3(CO10]-, [Te2Mn3(CO)9]2-, [Te2Mn3(CO)9]-, and [Te2Mn4(CO)12]2-

The reactions of appropriate ratios of K2TeO3 and [Mn2(CO)10)] in superheated methanol solutions lead to a series of novel cluster anions [Te4Mn3(CO)10] (1), [Te2Mn3(CO)9]2- (2), [Te2Mn3(CO)9]- (3), and [Te2Mn4(CO)12]2- (4). When cluster 1 is treated with [Mn2(CO)10]/KOH in methanol, paramagnetic cluster 2 is formed in moderate yield. Cluster 2 is oxidized by [Cu(MeCN)4]BF4 to give the closo-cluster [Te2Mn3(CO)9]- (3), while treatment of 2 with [Mn2(CO)10]/KOH affords the closo-cluster 4. IR spectroscopy showed that cluster 1 reacted with [Mn2(CO)10] to give cluster 4 via cluster 2. Clusters 1-4 were structurally characterized by spectroscopic methods or/and X-ray analyses. The core structure of 1 can be described as two [Mn(CO)3] groups doubly bridged by two Te2 fragments in a mu2-eta2 fashion. Both [Mn(CO)3] groups are further coordinated to one [Mn(CO)4] moiety. Cluster 2 is a 49 e- species with a square-pyramidal core geometry. While cluster 3 displays a trigonal-bipyramidal metal core, cluster 4 possesses an octahedral core geometry.

Structural rearrangements in triple-decker-like complexes with mixed group 15/16 ligands: synthesis and characterization of the redox couple

The reaction of As4Se4 with stoichiometric amounts of [Cp*Fe2(CO)4] (Cp* = C5Me5) in boiling toluene forms [Cp2*Fe2As2Se2] (1) in good yield. X-ray crystallography shows 1 to have a triple-decker structure which comprises a tetraatomic mu,eta4:4-As2Se2 ligand. Density functional theory (DFT) and extended Hückel molecular orbital (EHMO) calculations confirm that the As2Se2 ligand behaves as a four-electron pi donor. Oxidation of 1 with equimolar amounts of [(C5H5)2Fe]PF6, Br2 and I2, respectively, gave compounds 2-4. According to X-ray crystallographic investigations that were carried out on 2 and 4, the oxidation state has a considerable influence on the structure of the Fe2As2Se2 core: significant shortening of the Fe-Fe distance (deltad(Fe-Fe)> 0.3 A) and weakening of the As-As bond length ((deltad(As-As) > 0.3 A) suggests the formal presence of two diatomic AsSe ligands and a Fe-Fe bond. DFT and EHMO calculations confirm that an electron is removed from an occupied Fe-Fe orbital of antibonding character during oxidation. All molecular orbitals lower their energies upon oxidation, but the energy drop is relatively small for those involving the As-As bond. An additional structural feature in 4 consists of an electronic interaction of the iodide with both As atoms which suggests a formally neutral ion pair. Electrochemical studies confirm that the oxidation of 1 is a reversible one-electron process with E(1/2)= +0.07 V (in THF). These studies also reveal that 4 dissociates in polar solvents, such as THF, into [1]+ and I-, which is followed by transformation into 1 and I3.