Qin-Juan Xu

Self-assembly, thermal stability and photoluminescence of two mixed-ligand silver(I) networks via 2D → 2D and 2D → 3D parallel interpenetration of (4,4) nets

Two mixed-ligand silver(I) coordination polymers (CPs) [Ag2(dmapym)2(suc)·H2O]n (1) and [Ag2(dmapym)2(bdc)·2H2O]n (2), (dmapym = 2-amino-4,6-dimethylpyrimidine, H2suc = succinic acid, H2bdc = 1,3-benzenedicarboxylic acid), were synthesized and characterized. The structure of 1 presents an argentophilic interaction enhanced 2-crossing [2]-catenane motif formed between pairs of parallel interpenetrating 2D 44-sql nets. For 2, as the dicarboxylate changes from flexible H2suc to rigid V-shaped H2bdc, each highly undulated 2D 44-sql net was penetrated in parallel by the two nearest neighbouring ones and thus the overall 2D → 3D network is formed. The geometries and flexibility of dicarboxylates influence the coordination environments of metal ions and arrangement of ligands and thus determine the structures of the CPs. The photoluminescent and thermal properties of 1 and 2 have also been investigated.

A New "Switch-On" Fluorescence Chemosensor for Anions via Modulation of Intraligand and Metal-to-Ligand Charge-Transfer Emission in a Pd(II)-based Receptor

In recent years there has been great interest in anion recognition and sensing due to the key roles played by anions during chemical, biological and environmental processes [1–13]. Fluorescence chemosensors are used to transduce binding events into a fluorescent signal, and many signaling mechanisms for the sensing of anions have been developed, such as photoinduced electron transfer (PET) [14–17], intramolecular charge transfer (ICT) [18, 19], excited-state proton transfer [20, 21], excimer/exciplex formation [22–24], competitive binding [25–27]and metalto-ligand charge-transfer (MLCT) [28, 29]. The development of simple and sensitive anion sensors continues to be an important field of research. When a fluorescent ligand is complexed to a metal ion, its fluorescence can be either quenched or enhanced by different metal ions [30]. In general, fluorescence quenching occurs with heavy metal ion complexation due to intramolecular energy transfer from the excited state of the ligand to the localized energy levels of the metal ion, or due to relaxation mechanisms of the heavy metal “paramagnetic effect” for intersystem crossing [31, 32]. Therefore, the fluorescence of intraligand (IL) transitions (between orbitals localized primarily on a coordinated ligand) is quenched by heavy metal ions and fluorescence due to metal-to-ligand charge-transfer (MLCT) transitions is not preferred. Here we describe a new fluorescence-enhanced anion sensor mechanism based on the modulation of IL and MLCT fluorescence emission from a fluorescent metal complex in the presence of certain anions. The syntheses of bis(1-benzylidene-4-phenylthiosemicarbazato)-palladium(II) (1) and bis(1-(4-(dimethylamino)benzylidene)-4-phenylthiosemicarbazato)palladium (II) (2, Scheme 1) are described, as well as their application as metal-based anion receptors. Complex 2 exhibits intraligand π–π* (IL) and MLCT dual fluorescence emissions in organic solvents at room temperature that can be modulated in the presence of anions. Complex 2 was found to act as an anion-triggered IL and MLCT emission enhanced chemosensor.

1-[4-(Di-methyl-amino)-benzyl-idene]-4-o-tolyl-thio-semicarbazide.

The asymmetric unit of the title compound, C17H20N4S, contains two independent molecules, the main difference between them being the dihedral angles between the benzene rings [19.99 (17) and 9.72 (17)°]. The molecules both have a trans conformation about the C=N double bond and intramolecular C—H⋯S and N—H⋯N hydrogen bonds are observed in both molecules. In the crystal, molecules are linked by weak N—H⋯S hydrogen bonds with graph-set motif R 2 2(8). In each molecule, all but one of the N atoms and both the S atoms are involved in hydrogen bonding.

Erratum: 1-[4-(Di-methyl-amino)-benzyl-idene]-4-o-tolyl-thio-semicarbazide. Corrigendum.

Corrigendum to Acta Cryst. (2013), E69, o906–o907.

Self-assembly of a Novel Three-dimensional Silver(I) Supramolecular Framework from Cationic Chains and Anionic Sheets

A new three-dimensional (3D) supramolecular framework, [Ag2(bipy)2(bdc)·4H2O]n 1, has been synthesized by the ultrasonic reaction of Ag2O, bipy and H2bdc (H2bdc = 1,4-benzenedicarboxylic acid; bipy = 4,4’-bipyridine) at room temperature. It exhibits a new 3D supramolecular framework which is built from cationic Ag-bipy chains and anionic bdc-H2O sheets through hydrogen bonds, π · · ·π stacking and C-H· · ·π interactions. Additionally, the photoluminescent and thermal properties of 1 were investigated. Graphical Abstract Self-assembly of a Novel Three-dimensional Silver(I) Supramolecular Framework from Cationic Chains and Anionic Sheets

Tetra­aqua­tetra­kis{μ3-3,3′-[(E,E)-ethane-1,2-diylbis(nitrilo­methyl­idyne)]benzene-1,2-diolato}octa­zinc(II) N,N-dimethyl­formamide hexa­solvate

The asymmetric unit of the title compound [Zn8(C16H12N2O4)4(H2O)4]·6C3H7NO, consists of eight ZnII cations, four tetravalent anionic ligands, L 4− (L 4− = 3,3′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dibenzene-1,2-bis(olate), four coordinated water molecules and six N,N-dimethylformamide solvate molecules. The coordination complex comprises an octanuclear ZnII unit with its ZnII centers coordinated in two discrete distorted square-pyramidal geometries. Four ZnII atoms each coordinate to two nitrogen atoms and two phenolate oxygen atoms from an individual L 4− ligand and one coordinated water molecule. The other four ZnII atoms each bind to five phenolate oxygen atoms from three different L 4− ligands. In the crystal structure, the ZnII complex unit, coordinated water molecules and dimethylformamide solvate molecules are linked via O—H⋯O and C—H⋯O hydrogen bonds. Molecules are connected by additional intermolecular O—H⋯O and C—H⋯O hydrogen bonds, forming an extensive three dimensional framework.