Luminescent lanthanide complexes based on 4,5-di(3,5-dicarboxylphenoxy)phthalic acid as enhanced fluorescence probes for highly selective detection of lead(II) ions in water.

Six novel lanthanide complexes ([Nd2(L)(H2O)6]n·4.58n(H2O) (1), [Ln(H3L)(H2O)]n·0.5n(H2O), Ln = Sm (2), Eu (3), Gd (4), Tb (5), Eu0.18Gd0.62Tb0.20 (6)) have been hydrothermally synthesized based on the ligand 4,5-di(3,5-dicarboxylphenoxy)phthalic acid (H6L). Single crystal X-ray diffraction reveals that complexes 1-6 are 2D structures, where 2-6 are isomorphic. Complexes 3 and 5 exhibit the characteristic fluorescence of Eu(III) and Tb(III) ions respectively, while complex 4 shows blue-green light emission based on the ligand. In particular, the ternary Eu/Gd/Tb complex 6 shows white light emission with a CIE (Commission International del'Eclairage) chromaticity coordinate of (0.330, 0.339) and hence close to pure white light emission. Moreover, complexes 3 and 5 display specific fluorescence-enhanced detection performance for Pb2+ ions: The interaction between Pb2+ ions and the ligand enhances the charge transfer efficiency between the ligand and the Eu(III) and Tb(III) ions and thus leads to fluorescence enhancement of complexes 3 and 5. More importantly, complex 3 exhibits the lowest detection limit of 4.72 nM for Pb2+ ions among the existing complex fluorescent probes. In addition, both complexes 3 and 5 show good performance for recycling and for the detection of Pb2+ in real water samples.

Metal halide coordination compounds with quinazolin-4(3H)-one.

Three coordination compounds of quinazolin-4(3H)-one (quinoz; C8H6N2O) with divalent group 12 halides are reported. In all complexes, coordination occurs via the nitro-gen atom ortho to the quinazolinone carbonyl group. In the two chain polymers with composition [MX 2(quinoz)], viz. (M = Cd, X = Br), catena-poly[[[quinazolin-4(3H)-one-κN 3]cadmium(II)]-di-µ-bromido], [CdBr2(C8H6N2O)]n (I), and M = Hg, X = Cl, catena-poly[[[quinazolin-4(3H)-one-κN 3]mercury(II)]-di-µ-chlorido], [HgCl2(C8H6N2O)]n (II), the divalent cations are five-coordinate, with four bridging halide and one terminal quinoz ligand. The CdII atom in (I) has an almost trigonal-bipyramidal coordination environment, whereas the HgII atom in (II) has a more distorted coordination environment. Likewise, the halide bridges in (II) are significantly more asymmetric than in (I). In both (I) and (II), quinoz ligands at adjacent cations along each strand are oriented in opposite directions, and the organic ligands of neighboring strands inter-digitate with resulting π-π inter-actions. In contrast to the halide-bridged chain polymers (I) and (II), the adduct of quinoz with CdI2 is the tetra-hedral complex [CdI2(quinoz)2], di-iodido-bis-[quinazolin-4(3H)-one-κN 3]cadmium(II), [CdI2(C16H12N4O2)], (III). The CdII atom in this discrete complex is located on a twofold rotation axis. Disorder in (III) is reflected in an alternative minority orientation of the mol-ecules for which the iodine sites closely match the position of the majority orientation. In view of the low site occupancy of only 0.0318 (8) Å, only the CdII position for this alternative orientation was taken into account during refinement. In all three compounds, classical N-H⋯O hydrogen bonds with donor-acceptor distances of ca 2.9 Šoccur; they link the polymer chains in (I) and (II) into di-periodic networks and connect adjacent discrete complexes in (III) to mono-periodic strands.

Gauging the Strength of the Molecular Halogen Bond via Experimental Electron Density and Spectroscopy.

Strong and weak halogen bonds (XBs) in discrete aggregates involving the same acceptor are addressed by experiments in solution and in the solid state. Unsubstituted and perfluorinated iodobenzenes act as halogen donors of tunable strength; in all cases, quinuclidine represents the acceptor. NMR titrations reliably identify the strong intermolecular interactions in solution, with experimental binding energies of approx. 7 kJ/mol. Interaction of the σ hole at the halogen donor iodine leads to a redshift in the symmetric C-I stretching vibration; this shift reflects the interaction energy in the halogen-bonded adducts and may be assessed by Raman spectroscopy in condensed phase even for weak XBs. An experimental picture of the electronic density for the XBs is achieved by high-resolution X-ray diffraction on suitable crystals. Quantum theory of atoms in molecules (QTAIM) analysis affords the electron densities and energy densities in the bond critical points of the halogen bonds and confirms stronger interaction for the shorter contacts. For the first time, the experimental electron density shows a significant effect on the atomic volumes and Bader charges of the quinuclidine N atoms, the halogen-bond acceptor: strong and weak XBs are reflected in the nature of their acceptor atom. Our experimental findings at the acceptor atom match the discussed effects of halogen bonding and thus the proposed concepts in XB activated organocatalysis.

A Zn-coordination polymer for the quantitative and selective colorimetric detection of residual tetracycline in aqueous solution and urine.

A one-step solvothermal synthesis provides a functional crystalline one-dimensional Zn-coordination polymer (Zn-CP) with excellent stability in aqueous solution over a wide range of temperature and pH. Zn-CP is a rapid, highly sensitive and selective sensor for detecting tetracycline (TC). Quantitative TC detection is based on the ratio of fluorescence intensities I530/I420, with a limit of detection (LOD) of 5.51 nM in aqueous solution and 47.17 nM in human urine. The characteristics of colorimetric TC sensing by Zn-CP are highly favorable for application because the color of Zn-CP changes in the visible part of the spectrum from blue-purple to yellow-green upon addition of TC. Conversion of these colors into an RGB signal is simply achieved with an app for the smart phone and provides LODs of 8.04 nM and 0.13 µM TC in water and urine, respectively. Our suggested sensing mechanisms assume that the fluorescence intensity of Zn-CP@TC at 530 nm is enhanced by energy transfer of Zn-CP to TC, while the fluorescence of Zn-CP at 420 nm is quenched by photoinduced electron transfer (PET) from TC to the organic ligand in Zn-CP. These fluorescence properties make Zn-CP a convenient, low-cost, rapid and green detection device for monitoring TC under physiological conditions and in aqueous media.

The heterometallic one-dimensional solvated coordination polymer [NiPt2Cl6(TRIP-Py)4]n.

The ditopic ligand 10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene (TRIP-Py, C29H20NPSi) binds as a pyridine donor to NiII and as a phosphatriptycene donor towards PtII. The selectivity relies entirely on the Pearson character of the donor sites and the matching hardness of the respective metal cations. The product is the one-dimensional coordination polymer catena-poly[[[dichloridonickel(II)]-bis{µ-10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene}-bis[dichloridoplatinum(II)]-bis{µ-10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene}] dichloromethane pentasolvate ethanol icosasolvate], {[NiPt2Cl6(TRIP-Py)4]·5CH2Cl2·20EtOH}n (1), which retains large pores due to the inherent rigidity of the ligand. This is enabled by the caged triptycene scaffold which fixes the direction of the phosphorus donor with respect to the remaining molecule and especially the pyridyl moiety. In its crystal structure, which was determined from synchrotron data, the pores of the polymer are filled with dichloromethane and ethanol molecules. Finding a suitable model for the pore content is complicated as it is too disordered to give a reasonable atomic model but too ordered to be described by an electron gas solvent mask. This article presents an in-depth description of this polymer, as well as a discussion on the use of the bypass algorithm for solvent masks.

A Rigid Linker for Site-Selective Coordination of Transition Metal Cations: Combining an Acetylacetone with a Caged Phosphine.

The combination of a soft phosphorus and a hard oxygen donor in the new ligand HacacTRIP leads to excellent site selectivity for the coordination of two different metal cations of matching Pearson character. The deprotonation step required for coordinating the acetylacetone oxygen donor further increases the selectivity. In contrast to most phosphines, the use of the caged phosphatriptycene motif enables a rigid and directional orientation of the phosphorus binding site which is required to form stable coordination network structures. In addition to the synthesis of HacacTRIP, we present its selective coordination. The deprotonated acetylacetone was selectively bound to CuII and FeIII. The solid state structure of the former displays a rare axial coordination of chloroform molecules. The phosphorus donor was selectively coordinated to the monovalent coinage metal cations CuI, AgI, and AuI. The CuI and AgI complexes represent the first examples in which a phosphatriptycene is bound to these metal cations. Heterometallic coordination compounds were characterized with combinations of these two groups. They comprise an oligonuclear CuI/CuII mixed-valence compound in which iodide binds to both CuI and CuII cations and a complex in which acacTRIP- bridges CuII and AuI. In addition to these discrete aggregates, the ligand has been used to link FeIII and AgI into a 2D coordination polymer with unprecedented trigonal planar coordination of three bulky phosphatriptycenes to a cation and resulting honeycomb topology. Its almost regular hexagons underline the desired rigidity of the ditopic acacTRIP- ligand.

Three for the Price of One: Concomitant I⋯N, I⋯O, and I⋯π Halogen Bonds in the Same Crystal Structure.

The ditopic molecule 3-(1,3,5-trimethyl-1H-4-pyrazolyl)pentane-2,4-dione (HacacMePz) combines two different Lewis basic sites. It forms a crystalline adduct with the popular halogen bond (XB) donor 2,3,5,6-tetrafluoro-1,4-diiodobenzene (TFDIB) with a HacacMePz:TFDIB ratio of 2:3. In a simplified picture, the topology of the adduct corresponds to a hcb net. In addition to the expected acetylacetone keto O and pyrazole N acceptor sites, a third and less common short contact to a TFDIB iodine is observed: The acceptor site is again the most electron-rich site of the pyrazole π-system. This iminic N atom is thus engaged as the acceptor in two orthogonal halogen bonds. Evaluation of the geometric results and of a single-point calculation agree with respect to the strength of the intermolecular contacts: The conventional N⋯I XB is the shortest (2.909(4) Å) and associated with the highest electron density (0.150 eÅ-3) in the bond critical point (BCP), followed by the O⋯I contact (2.929(3) Å, 0.109 eÅ-3), and the π contact (3.2157(3) Å, 0.075 eÅ-3). If one accepts the idea of deducing interaction energies from energy densities at the BCP, the short contacts also follow this sequence. Two more criteria identify the short N⋯I contact as the most relevant: The associated C-I bond is significantly longer than the database average, and it is the only intermolecular interaction with a negative total energy density in the BCP.

Tri-methyl-pyrazole: a simple heterocycle reflecting Kitaigorodskii's packing principle.

The five-membered heterocycle 1,3,5-trimethyl-1H-pyrazole, C6H10N2 (1) crystallizes in space group Pnma with all non-hydrogen atoms of the mol-ecule on the crystallographic mirror plane. This arrangement has been recognized as favorable with respect to space filling by Kitaigorodskii and Wilson, pioneers in the field of crystal packing; Pnma represents a particularly rare space group for residues exclusively in a general position. Neighboring mol-ecules in 1 inter-act via non-classical C-H⋯N bonds in the plane and C-H⋯π contacts between adjacent layers. In Pnma, crystallographic inversion relates dipolar mol-ecules located on successive mirror planes and results in their head-to-tail arrangement. The inter-layer distance in the [010] direction is closely related to the van der Waals radii of C and N.

Weaving a 2D net of hydrogen and halogen bonds: cocrystal of a pyrazolium bromide with tetrafluorodiiodobenzene.

Hydrohalides of Lewis bases may act as halogen bond (XB) acceptors and combine two directional interactions, namely, hydrogen bonds (HB) and XBs in the same solid. 3-(1,3,5-Trimethyl-1H-pyrazol-4-yl)acetylacetone (C11H16N2O2, HacacMePz) was protonated with HX (X = Cl or Br) to afford the hydrohalides, C11H17N2O2+·X- or H2acacMePz+·X- (1, X = Cl; 2, X = Br). Hydrohalides 1 and 2 are isomorphous and adopt a classical dipole packing. Consistent with the observation for most ß-diketones, the enol form with an intramolecular HB is observed. Additional noteworthy interactions are HBs of the protonated pyrazolium towards the X- anion at donor-acceptor distances of 2.9671 (17) Šfor 1 and 3.159 (4) Šfor 2. Cocrystallization of hydrobromide 2 with the XB donor tetrafluorodiiodobenzene (TFDIB) leads to the adduct C11H17N2O2+·Br-·0.5C6F4I2·H2O or (H2acacMePz+·Br-)2·(H2O)2·TFDIB (3), in which the XB donor TFDIB is situated on a crystallographic centre of inversion. Classical HBs link organic cations, water molecules and Br- anions into chains along [010]. Almost orthogonal to this interaction, XBs with Br...I = 3.2956 (4) Šconnect neighbouring chains along [102] into two-dimensional sheets in the (10-2) plane. Assisted by their negative charge, halide anions represent particularly good nucleophiles towards XB donors.

Phosphorus or nitrogen - the first phosphatriptycene in coordination polymer chemistry.

Phosphasilatriptycene, a phenylene spacer and a pyridyl moiety represent the building blocks of TRIP-Py, the first heteroditopic ligand featuring a phoshatriptycene scaffold. The P and N donor sites located at opposite ends of the prolate TRIP-Py molecule selectively coordinate metal cations matching their Pearson character. The harder pyridyl donor binds to ZnII, the softer phosphorus donor to PtII, HgII and AuI. The remarkably short Au-P bond in the latter underlines the good π acceptor character of the phoshatriptycene moiety. When both the chloride salts of hard ZnII and soft AuI cations are available for coordination, TRIP-Py acts as selective ditopic linker in the discrete trinuclear mixed-metal complex [ZnCl2(TRIP-PyAuCl)2]. For CdII, a cation with intermediate Pearson character, selectivity withers, and a monometallic coordination polymer is obtained. Its significantly elongated Cd-P coordinative bonds underline, however, the preference of CdII for the harder N donor. When ZnII and HgII halides are combined, their preference for the matching donor sites in TRIP-Py and for tetrahedral coordination afford 1D and 2D heterobimetallic polymers with and without solvent-accessible voids. TRIP-Py enables the use of two important analytical tools: its rigidity facilitates crystallization and allowed to investigate 14 crystalline solids, and its P donor provides a powerful NMR probe for coordination.

Structure, magnetic properties and spin density of two alternative Mn(II) coordination polymers based on 1,4-bis(2'-carboxyphenoxy)benzene.

Two novel manganese coordination polymers [Mn2(µ2-bcpb)(µ4-bcpb)(2,2'-bipy)2]n (1) and [Mn2(µ3-bcpb)2(2,2'-bipy)2(H2O)]n (2) (H2bcpb = 1,4-bis(2'-carboxylato phenoxy)-benzene; 2,2'-bipy = 2,2'-bipyridine), have been synthesized successfully from the same reactants. This unusual selectivity was corroborated by X-ray powder diffraction. Single crystal X-ray diffraction analysis of complex 1 reveals that neighboring Mn(II) ions are linked via two bcpb2- anions to form a dinuclear Mn(II) subunit [Mn2(µ1,1-COO)2]2+ with a Mn⋯Mn distance of 3.3758 (6) Å. And π⋯π interactions between aromatic rings of the bcpb2- and 2,2'-bipy ligands stabilize the two-dimensional extended coordination network with the unprecedented Schläfli symbols {4·62}2{42·62·82}. In the [Mn2(µ1,3-COO)2]2+ subunit of 2, two linking bcpb2- ligands subtend an interaction distance of 4.4048(6) Å. Intermolecular O-H⋯O hydrogen bonds involving oxygen atoms of carboxylic acid and coordinated water molecules connect adjacent 1D chain molecules into a 2D network. Experimental temperature-dependent magnetic susceptibility measurements and spin density analyses by DFT disclose that compounds 1 and 2 display different magnetic properties.

Formation and Reactivity of a Hexahydridosilicate [SiH6 ]2- Coordinated by a Macrocycle-Supported Strontium Cation.

The cationic benzyl complex [(Me4 TACD)Sr(CH2 Ph)][A] (Me4 TACD=1,4,7,10-tetramethyltetraazacyclododecane; A=B(C6 H3 -3,5-Me2 )4 ) reacted with two equivalents of phenylsilane to give the bridging hexahydridosilicate complex [(Me4 TACD)2 Sr2 (thf)4 (µ-κ3 : κ3 -SiH6 )][A]2 (3 a). Rapid phenyl exchange between phenylsilane molecules is assumed to generate monosilane SiH4 that is trapped by two strontium hydride cations [(Me4 TACD)SrH(thf)x ]+ . Complex 3 a decomposed in THF at room temperature to give the terminal silanide complex [(Me4 TACD)Sr(SiH3 )(thf)2 ][A], with release of H2 . Upon reaction with a weak Brønsted acid, CO2 , and 1,3,5,7-cyclooctatetraene SiH4 was released. The reaction of a 1 : 2 mixture of cationic benzyl and neutral dibenzyl complex with phenylsilane gave the trinuclear silanide complex [(Me4 TACD)3 Sr3 (µ2 -H)3 (µ3 -SiH3 )2 ][A], while n OctSiH3 led to the trinuclear (n-octyl)pentahydridosilicate complex [(Me4 TACD)3 Sr3 (µ2 -H)3 (µ3 -SiH5 n Oct)][A].

Sterically Crowded Tris(2-(trimethylsilyl)phenyl)phosphine - Is it Still a Ligand?

Tris(2-(trimethylsilyl)phenyl)phosphine, P(o-TMSC6 H4 )3 , was synthesised and characterised in solution and in the solid state. The large steric bulk prevents most reactions of the phosphorus donor and makes the compound air stable both in the solid state as well as in solution. This shielded phosphine can still undergo three reactions, namely protonation, oxidation to the phosphine oxide under harsh conditions and complexation to AuI , thus forming a complex with linear coordination. Unexpectedly, complexation was unsuccessful with a range of other metal cations. Neither PdII , PtII , ZnII nor HgII reacted and even the remaining coinage metal cations CuI and AgI could not be coordinated. Both the parent molecule as well as the reaction products were structurally characterised by single crystal X-ray diffraction, and the conformational change of geometry required to accommodate the additional atoms was analysed in detail. Apart from chemical oxidation with H2 O2 , P(o-TMSC6 H4 )3 displays reversible electrochemical oxidation with a potential not unlike the one of sterically unencumbered phosphines for which the oxidation is usually not reversible. P(o-TMSC6 H4 )3 can thus be considered a model compound for the investigation of the electronic properties of sterically unencumbered phosphines.

Synthesis, crystal structure and magnetic properties of a one-dimensional Mn2+ complex constructed from (+)-dibenzoyltartaric acid and 2,2'-bipyridine.

The self-assembly reaction of (+)-dibenzoyltartaric acid (D-H2DBTA) with 2,2'-bipyridine (bpy) and Mn(CH3CO2)2·4H2O yielded a new coordination polymer, namely, catena-poly[[[diaqua(2,2'-bipyridine-κ2N,N')manganese(II)]-µ-2,3-bis(benzoyloxy)butanedioato-κ2O2:O3] dihydrate], {[Mn(C18H12O8)(C10H8N2)(H2O)2]·2H2O}n or {[Mn(DBTA)(bpy)(H2O)2]·2H2O}n, (I). Complex (I) has been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA) and single-crystal and powder X-ray diffraction. It crystallizes in the orthorhombic space group P212121. In the complex, the Mn2+ cation displays a distorted octahedral {MnO4N2} geometry, formed from two carboxylate O atoms of two DBTA2- ligands, two cis-oriented N atoms from one chelating 2,2'-bipyridine ligand and two trans-oriented O atoms from coordinated water molecules. The polymer displays a 1D chain with an Mn...Mn distance of 9.428 (1) Å. Due to the presence of flexible polycarboxylate and rigid bipyridyl ligands in the molecular structure, a high thermal stability of the complex is attained. The magnetic properties of (I) were analyzed based on the mononuclear Mn2+ model due to the long intramolecular Mn...Mn distance. The zero field splitting (ZFS) contribution in the high-spin Mn2+ cation is almost negligible and there are weak antiferromagnetic couplings between 1D chains [zJ' = -0.062 (5) cm-1], corresponding to an intermolecular Mn...Mn distance of 7.860 (2) Å.

Synthesis, structure and magnetocaloric properties of a new two-dimensional gadolinium(III) coordination polymer based on azobenzene-2,2',3,3'-tetracarboxylic acid.

A new Gd3+ coordination polymer (CP), namely, poly[diaqua[µ4-1'-carboxy-3,3'-(diazene-1,2-diyl)dibenzene-1,2,2'-tricarboxylato]gadolinium(III)], [Gd(C16H7N2O8)(H2O)2]n, (I), has been synthesized hydrothermally from Gd(NO3)3·6H2O and azobenzene-2,2',3,3'-tetracarboxylic acid (H4abtc). The target solid has been characterized by single-crystal and powder X-ray diffraction, elemental analysis, IR spectroscopy and susceptibility measurements. CP (I) crystallizes in the monoclinic space group C2/c. The structure features a 4-connected topology in which Gd3+ ions are connected by carboxylate groups into a linear chain along the monoclinic symmetry direction. Adjacent one-dimensional aggregates are bridged by Habtc3- ligands to form a two-dimensional CP in the (10-1) plane. A very short hydrogen bond [O...O = 2.4393 (4) Å] links neighbouring layers into a three-dimensional network. A magnetic study revealed antiferromagnetic Gd...Gd coupling within the chain direction. CP (I) displays a significant magnetocaloric effect (MCE), with a maximum -ΔSm of 27.26 J kg-1 K-1 for ΔH = 7 T at 3.0 K. As the MCE in (I) exceeds that of the commercial magnetic refrigerant GGG (Gd3Ga5O12, -ΔSm = 24 J kg-1 K-1, ΔH = 30 kG), CP (I) can be regarded as a potential cryogenic material for low-temperature magnetic refrigeration.

Synthesis, structure and in vitro biological properties of a new copper(II) complex with 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid.

The new copper(II) complex dichloridobis(4-{[3-(pyridin-2-yl-κN)-1H-pyrazol-1-yl-κN2]methyl}benzoic acid)copper(II) methanol sesquisolvate hemihydrate, [CuCl2L2]·1.5CH3OH·0.5H2O, (1), has been synthesized from CuCl2·2H2O and the ligand 4-{[3-(pyridin-2-yl)-1H-pyrazol-1-yl]methyl}benzoic acid (L, C15H11N3O2). The complex was characterized by elemental analysis, Fourier transform IR spectroscopy, electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Two chloride ligands and two bidentate L ligands coordinate the CuII centre in 1 in a Jahn-Teller-distorted octahedral geometry of rather unusual configuration: a chloride substituent and a pyrazole N atom of an N,N'-chelating ligand occupy the more distant axial positions. Classical O-H...O hydrogen bonds and O-H...Cl interactions link neighbouring complex molecules and cocrystallized methanol molecules into chains that propagate parallel to the b direction. The title compound shows intriguing bioactivity: the effects of 1 on the enzymatic activity of protein tyrosine phosphatase 1B (PTP1B) and on the viability of human breast cancer cells of cell line MCF7 were evaluated. Complex 1, with an IC50 value of 0.51 µM, can efficiently inhibit PTP1B activity. An enzyme kinetic assay suggests that 1 inhibits PTP1B in a noncompetitive manner. A fluorescence titration assay indicates that 1 has a strong affinity for PTP1B, with a binding constant of 4.39 × 106 M-1. Complex 1 may also effectively decrease the viability of MCF7 cells in an extent comparable to that of cisplatin (IC50 = 6.3 µM). The new copper complex therefore represents a promising PTP1B inhibitor and an efficient antiproliferation reagent against MCF7 cells.

A new organic-inorganic compound, ethyl-enedi-ammonium hexa-chlorido-stannate(IV) p-anisaldehyde disolvate.

The asymmetric unit of the title organic-inorganic hybrid complex [systematic name: ethane-1,2-diaminium hexa-chlorido-stannate(IV)-4-meth-oxy-benz-alde-hyde (1/2)], (C2H10N2)[SnCl6]·2C8H8O2, contains one half of an ethyl-enedi-ammonium cation, one half of an [SnCl6]2- anion and one p-anisaldehyde mol-ecule. Both the organic cation and the quasi-regular octa-hedral inorganic anion are located about inversion centres. The organic cations and [SnCl6]2- anions lie in layers parallel to the ac plane with p-anisaldehyde mol-ecules occupying the space between the layers. A network of classical N-H⋯Cl and N-H⋯O hydrogen bonds exists between the ethyl-enedi-ammonium cations and the [SnCl6]2- anions and p-anisaldehyde mol-ecules. These inter-actions, together with non-classical C-H⋯O inter-actions between the ethyl-enedi-ammonium cations and the p-anisaldehyde mol-ecules, serve to hold the structure together. The crystal studied was refined as a two-component twin.

Design and synthesis of three new copper coordination polymers: efficient degradation of an organic dye at alkaline pH.

Three new coordination polymers (CPs) based on Cu(II), namely {[Cu6(H2L)4(4,4'-bpy)6(H2O)2]·16H2O}n(1), {[Cu(H3L)(1,4-bib)]·3H2O}n(2), and {[Cu2(H2L)2(1,4-bib)2][Cu(1,4-bib)(H2O)2]}n·4nH2O(3) (H5L = 6-(3',4'-dicarboxyphenoxy)-2,3,5-benzene tricarboxylic acid, 4,4'-bpy = 4,4'-bipyridine and 1,4-bib = 1,4-bis(1H-imidazol-1-yl)benzene) were synthesized under hydrothermal conditions and characterized. 1 adopts a three-dimensional structure and can be described with the point symbol {4·52}2{42·54·64·83·92}{5·104·12} whereas 2 shows a layered structure. 3 can be perceived as a complex salt of two coordination polymers: the cationic component [Cu(1,4-bib)(H2O)2]n2+ (3a) represents a chain polymer and the second anionic moiety [Cu2(H2L)2(1,4-bib)2]n2- (3b) corresponds to a 2D sub-structure. In the presence of H2O2, all complexes 1-3 act as efficient photocatalysts for the degradation of the dye methylene blue (MB). The effects of properties such as initial MB concentration, catalyst dosage, pH value, and H2O2 concentration on MB degradation were also investigated and analyzed in detail. Compounds 1-3 exhibit excellent structural stability during the catalytic process and can be reused at least three times. The hydroxyl radical (OH˙) and holes (h+) were confirmed as the main active species in the degradation process.

Hydrogen-Bonded and Halogen-Bonded: Orthogonal Interactions for the Chloride Anion of a Pyrazolium Salt.

In the hydrochloride of a pyrazolyl-substituted acetylacetone, the chloride anion is hydrogen-bonded to the protonated pyrazolyl moiety. Equimolar co-crystallization with tetrafluorodiiodobenzene (TFDIB) leads to a supramolecular aggregate in which TFDIB is situated on a crystallographic center of inversion. The iodine atom in the asymmetric unit acts as halogen bond donor, and the chloride acceptor approaches the σ-hole of this TFDIB iodine subtending an almost linear halogen bond, with Cl···I = 3.1653(11) Å and Cl···I-C = 179.32(6)°. This contact is roughly orthogonal to the N-H···Cl hydrogen bond. An analysis of the electron density according to Bader's Quantum Theory of Atoms in Molecules confirms bond critical points (bcps) for both short contacts, with ρbcp = 0.129 for the halogen and 0.321eÅ-3 for the hydrogen bond. Our halogen-bonded adduct represents the prototype for a future class of co-crystals with tunable electron density distribution about the σ-hole contact.

Crystal structure and Hirshfeld surface analysis of bis-(6,7,8,9-tetra-hydro-11H-pyrido[2,1-b]quinazolin-5-ium) tetra-chlorido-zincate.

The title compound, (C12H15N2)2[ZnCl4], is a salt with two symmetrically independent, essentially planar heterocyclic cations and a slightly distorted tetra-hedral chloro-zincate dianion. N-H⋯Cl hydrogen bonds link these ionic constituents into a discrete aggregate, which comprises one formula unit. The effect of hydrogen bonding is reflected in the minor distortions of the [ZnCl4]2- moiety: distances between the cation and chlorido ligands engaged in classical hydrogen bonds are significantly longer than the others. Secondary inter-actions comprise C-H⋯π hydrogen bonding and weak π-π stacking. A Hirshfeld surface analysis indicates that the most abundant contacts in packing stem from H⋯H (47.8%) and Cl⋯H/H⋯Cl (29.3%) inter-actions.