Pb2BO3Cl: A Tailor‐Made Polar Lead Borate Chloride with Very Strong Second Harmonic Generation

A meticulously designed, polar, non‐centrosymmetric lead borate chloride, Pb₂BO₃Cl, was synthesized using KBe₂BO₃F₂ (KBBF) as a model. Single‐crystal X‐ray diffraction revealed that the structure of Pb₂BO₃Cl consists of cationic [Pb₂(BO₃)]⁺ honeycomb layers and Cl^? anions. Powder second harmonic generation (SHG) measurements on graded polycrystalline Pb₂BO₃Cl indicated that the title compound is phase‐matchable (type I) and exhibits a remarkably strong SHG response, which is approximately nine times stronger than that of potassium dihydrogen phosphate, and the largest efficiency observed in materials with structures similar to KBBF. Further characterization suggested that the compound melts congruently at high temperature and has a wide transparency window from the near‐UV to the mid‐IR region.     

Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand

New compounds [Ru(pap)₂(L)](ClO₄), [Ru(pap)(L)₂], and [Ru(acac)₂(L)] (pap=2‐phenylazopyridine, L^?=9‐oxidophenalenone, acac^?=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)₂(L)](ClO₄) and [Ru(acac)₂(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the Ru^III/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac^? ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L^? into L^. could be deduced from the near‐IR absorption of [Ru^III(pap)(L^.)(L^?)]²⁺. Other intense long‐wavelength transitions, including LMCT (L^?→Ru^III) and LL/CT (pap^.?→L^?) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [Ru^III(pap⁰)₂(L^?)]²⁺?[Ru^II(pap⁰)₂(L^.)]²⁺ and [Ru^III(pap⁰)(L^?)₂]⁺?[Ru^II(pap⁰)(L^?)(L^?)]⁺. Calculations of electrogenerated complex [Ru^II(pap^.?)(pap⁰)(L^?)] displayed considerable negative spin density (?0.188) at the bridging metal.     

A one‐dimensional mixed‐anion lead(II) coordination polymer: catena‐poly[[(1,10‐phenanthroline)lead(II)]‐μ‐benzoato‐μ‐nitrato‐[(1,10‐phenanthroline)lead(II)]‐di‐μ‐benzoato]

In the title polymeric compound, [Pb₂(C₇H₅O₂)₃(NO₃)(C₁₂H₈N₂)₂]_n, both independent Pb atoms adopt an eight‐coordinate geometry formed by one nitrate, three benzoate and one 1,10‐phenanthroline ligand. The one‐dimensional polymer consists of dimeric [Pb₂(C₇H₅O₂)₃(NO₃)(C₁₂H₈N₂)₂] units, in which all nitrate and benzoate ligands act in a bridging–chelating coordination mode.     

μ‐Acetato‐μ‐aqua‐μ‐hydroxido‐bis[(1,10‐phenanthroline)copper(II)] dinitrate monohydrate

The triply bridged title dinuclear copper(II) compound, [Cu₂(C₂H₃O₂)(OH)(C₁₂H₈N₂)₂(H₂O)](NO₃)₂·H₂O, (I), consists of a [Cu₂(μ₂‐CH₃COO)(μ₂‐OH)(phen)₂(μ₂‐OH₂)]²⁺ cation (phen is 1,10‐phenanthroline), two uncoordinated nitrate anions and one water molecule. The title cation contains a distorted square‐pyramidal arrangement around each metal centre with a CuN₂O₃ chromophore. In the dinuclear unit, both Cu^II ions are linked through a hydroxide bridge and a triatomic bridging carboxylate group, and at the axial positions through a water molecule. The phenanthroline groups in neighbouring dinuclear units interdigitate along the [010] direction, generating several π–π contacts which give rise to planar arrays parallel to (001). These are in turn connected by hydrogen bonds involving the aqua and hydroxide groups as donors with the nitrate anions as acceptors. Comparisons are made with isostructural compounds having similar cationic units but different counter‐ions; the role of hydrogen bonding in the overall three‐dimensional structure and its ultimate effect on the cell dimensions are discussed.     

A Novel 1D Coordination Polymer [Pb(phen)(μ‐N3)(μ‐NO3)]n with the First Pb2‐(μ‐N3)2 Unit (phen = 1,10‐phenanthroline)

A novel 1D polymeric lead(II) complex containing the first Pb₂‐(μ‐N₃)₂ motif, [Pb(phen)(μ‐N₃)(μ‐NO₃)]_n (phen = 1,10‐phenanthroline), has been synthesized and characterized. The single‐crystal X‐ray data showed the coordination number of Pb²⁺ ions to be eight (PbN₄O₄) with the Pb²⁺ ions having “stereo‐chemically active” electron lone pairs; the coordination sphere is hemidirected. The chains interact with each other via π‐π interactions to create a 3D framework.     

Anion‐directed Silver(I) Coordination Assemblies Based on 1‐(2‐Pyridyl)‐2‐(4‐pyridyl)‐1,2,4‐triazolewith Diverse Supramolecular Networks and Dichromate Removal Capabilities

A series of silver(I) supramolecular complexes, namely, {[Ag(L²⁴)](NO₃)}_n ( 1 ), [Ag₂(L²⁴)(NO₂)₂]_n ( 2 ), and {[Ag_1.25(L²⁴)(DMF)](PF₆)_1.25}_n ( 3 ) were prepared by the reactions of 1‐(2‐pyridyl)‐2‐(4‐pyridyl)‐1,2,4‐triazole (L²⁴) and silver(I) salts with different anions (AgNO₃, AgNO₂, AgPF₆). Single‐crystal X‐ray diffraction indicates that 1 – 3 display diverse supramolecular networks. The structure of dinuclear complex 1 is composed of a six‐membered Ag₂N₄ ring with the Ag ··· Ag distance of 4.4137(3) Å. In complex 2 , the adjacent Ag^I centers are interlinked by L²⁴ ligands into a 1D chain, the adjacent of which are further extended by the bridged nitrites to construct a 2D coordination architecture. Complex 3 shows a 3D (3,4)‐connected framework, which is generated by the linkage of L²⁴ ligands. All complexes were characterized by IR spectra, elemental analysis, and powder X‐ray diffraction. Notably, a structural comparison of the complexes demonstrates that their structures are predominated by the nature of anions. Additionally, 1 and 2 show efficient dichromate (Cr₂O₇^2–) capture in water system, which can be ascribed to the anion‐exchange.     

Triaqua(2,2′‐bipyridine‐κ2N,N′)(nitrato‐κO)manganese(II) nitrate

The crystal structure of the title compound, [Mn(NO₃)(C₁₀H₈N₂)(H₂O)₃]NO₃, contains a monomeric [Mn(NO₃)(bpy)(H₂O)₃]⁺ cation (bpy is 2,2′‐bi­pyridine) and a nitrate anion. The Mn^II ion is coordinated by one chelating bpy [Mn—N 2.241 (3) and 2.259 (3) Å], three water mol­ecules [Mn—O 2.120 (3)–2.188 (3) Å] and a nitrate ligand [Mn—O 2.228 (2) Å] in a distorted octahedral geometry. There are O?H—O hydrogen‐bonding interactions between the ligated water mol­ecules and the ligated and unligated nitrate anions, resulting in double columns of stacked cations and anions.     

New silicate-germanate Cs2Pb2[(Si0.6Ge0.4)2O7] from the series A2Pb2[B2O7], A = K,Cs, B = Si,Ge with the umbrella-like [PbO3]4- group

New silicate-germanate Cs₂Pb₂[(Si_0.6Ge_0.4)₂O₇] was synthesized in multi-components hydrothermal solution with 20 w.% concentration of Cs₂CO₃ mineralizer, pH = 10. Novel mixed compound belongs to the structure type A₂Pb₂[B₂O₇] previously indicated for powders with A = K, B=Si or Ge. Singe crystal structure determination of Cs₂Pb₂[(Si_0.6Ge_0.4)₂O₇] revealed the need for the correction of the space group of the earlier suggested structural model from P-3 to P-3m1, as well as for the splitting of the Pb-atom position. Umbrella-like groups [PbO₃]^4- are located between [(Si,Ge)O₄]^4- tetrahedra in mica-like honeycomb layers and play the role of tetrahedra with the Pb-lone-pair as the forth apex. Crystal chemical comparison revealed similarities and differences with the classical structure type of α-celsian Ba[Al₂Si₂O₈] with the tetrahedral double layer. Recently investigated nonlinear optical acentric borates Pb₂(BO₃)(NO₃) and Pb₂(BO₃)Cl are both related to this structural type, possessing umbrella-like groups [PbO₃]^4- and honeycomb layers [Pb₂(BO₃)]⁺ with the BO₃-triangles on the tetrahedral positions.     

{μ‐PbSe}: A Heavy CO Homologue as an Unexpected Ligand

Reactions of [K(18‐crown‐6)]₂[Pb₂Se₃] and [K([2.2.2]crypt)]₂[Pb₂Se₃] with [Rh(PPh₃)₃Cl] in en (ethane‐1,2‐diamine) afforded ionic compounds with [Rh₃(PPh₃)₆(μ₃‐Se)₂]^? and [Rh₃(CN)₂(PPh₃)₄(μ₃‐Se)₂(μ‐PbSe)]^3? anions, respectively. The latter contains a PbSe ligand, a rather uncommon homologue of CO that acts as a μ‐bridge between two Rh atoms. Quantum chemical calculations yield a significantly higher bond energy for PbSe than for CO, since the size of the ligand orbitals better matches the comparably rigid Rh‐Se‐Rh angles and the resulting Rh???Rh distance. To rationalize the bent coordination of the ligand, orbitals with significant ligand contributions and their dependence on the bonding angle were investigated in detail.     

Two‐dimensional π‐conjugated metal‐organic framework with high electrical conductivity for electrochemical sensing

A two‐dimensional π‐conjugated metal‐organic framework (MOF) with long‐range delocalized electrons has been prepared and applied as modified electrode material without further post‐modification. The MOF (Cu₃(HHTP)₂) is composed of Cu(II) centers and a redox‐active linker (2,3,6,7,10,11‐hexahydroxytriphenylene, HHTP). Compared to most MOFs, Cu₃(HHTP)₂ displays higher electrical conductivity and charge storage capacity owing to the collective effect of metal ions and aromatic ligands with π–π conjugation. In order to confirm the superior properties of this material, the electrochemical detection of dopamine (DA) was conducted and the satisfactory results were obtained. The currents increase linearly with the concentration of DA in the range 5.0 × 10^?8 to 2.0 × 10^?4 M with a detection limit of 5.1 nM. Furthermore, Cu₃(HHTP)₂ presents high selectivity and applicability in serum samples for electrochemical DA sensing. Overall, this material has excellent potential as a promising platform for establishing an MOF‐based electrochemical sensor.     

Water‐Stable Coordination Polymers as Dual Fluorescent Sensors for Highly Oxidizing Anions Cr2O72− and MnO4−

Due to their striking optical properties, luminescent coordination polymers as sensors for the detection of hazardous species have drawn interest of researchers in consideration of the control of environmental pollution. In this work, the organic ligand 2‐(4‐((E)‐2‐(pyridine‐2‐yl)vinyl)styryl)pyridine (2‐bpeb), which possesses a large π‐conjugated system, was employed to react with d¹⁰ metal ions to obtain novel luminescent coordination polymers. Three complexes [Cd(2‐bpeb)_0.5(CNA)(H₂O)] ( CP1 ), [Cd(2‐bpeb)_0.5(NDC)] ( CP2 ) and [Zn(2‐bpeb)(BDC)] ( CP3 ) were synthesized successfully by introducing carboxylic acids of 4‐carboxycinnamic acid (H₂CNA), 2,6‐naphthalene dicarboxylic acid (H₂NDC) and 1,4‐benzenedicarboxylic acid (H₂BDC) as auxiliary ligands. Because of the existence of the large π‐conjugated system and d¹⁰ metal ions, all of these coordination polymers exhibit striking fluorescence properties. Impressively, all of them can function as sensors for the detection of highly oxidizing anions MnO₄^? and Cr₂O₇^2?, with an increased sensitivity for MnO₄^?.     

A three‐dimensional PbII coordination framework: poly[[μ4‐(E)‐2,2′‐(diazene‐1,2‐diyl)dibenzoato]dimethanollead(II)]

In the title coordination polymer, [Pb(C₁₄H₈N₂O₄)(CH₃OH)₂]_n, the asymmetric unit contains half of a Pb^II cation, half of a 2,2′‐(diazene‐1,2‐diyl)dibenzoate dianionic ligand (denoted L²⁻) and one methanol ligand. Each Pb^II centre is eight‐coordinated by six O atoms of chelating/bridging carboxylate groups from four L²⁻ ligands and two O atoms from two terminal methanol ligands, forming a distorted dodecahedron. The [PbL₂(MeOH)₂] subunits are interlinked via the sharing of two carboxylate O atoms to form a one‐dimensional [PbL₂(MeOH)₂]_n chain. Adjacent chains are further connected by L²⁻ ligands, giving rise to a two‐dimensional layer, and these layers are bridged by L²⁻ linkers to afford a three‐dimensional framework with a 4¹²6³ topology.     

trans‐Diaqua­{5,5′‐[(E,E)‐pyridine‐2,6‐diylbis(methyl­idynenitrilo)]bis­[pyrimi­dine‐2,4(1H,3H)‐dione]}zinc(II) nitrate hexa­fluorophosphate trihydrate

The title compound, [Zn(C₁₅H₁₁N₇O₄)(H₂O)₂](NO₃)(PF₆)·3H₂O, contains a mononuclear zinc(II) complex. The Zn²⁺ centre is seven‐coordinated in a slightly distorted penta­gonal–bipyramidal geometry, with the two water O atoms located in the apical positions, and the pyridine N atom, the two imine N atoms and two carbonyl O atoms of the uracil groups located in the equatorial plane. The charge is balanced by PF₆⁻ and NO₃⁻ anions.     

Electrochemical Sensing of Mercury over Cadmium and Lead Cations by the Redox-Active Polyazacycloalkane Ligand 1,1″: 1′,1′′′-Bis[ethane-1,2-diylbis(iminomethylene)]bis[ferrocene]

The coordination behaviour of the redox-active polyazacycloalkane L¹ against the toxic heavy-metal ions Cd²⁺, Pb²⁺, and Hg²⁺ was studied in THF/H₂O 70 : 30 (containing 0.1 mol⋅dm⁻³ of (Bu₄N)ClO₄). The crystal and molecular structure of the cadmium complex [Cd(L¹)(NO₃)₂] ( 1 ) was determined by X-ray single-crystal analysis. The cadmium ion is in a 4+2 surrounding with the ligand L¹ acting as tetradentate and the apical positions occupied by the O-atoms of the nitrate anions. An electrochemical study reveals that L¹ shows a selective electrochemical response against Hg²⁺ over Cd²⁺ and Pb²⁺.     

Nitridorhenium(V) Complexes with 1,3,4‐Triphenyl‐1,2,4‐triazol‐5‐ylidene

[ReNCl₂(PPh₃)₂] and [ReNCl₂(PMe₂Ph)₃] react with the N‐heterocyclic carbene (NHC) 1,3,4‐triphenyl‐1,2,4‐triazol‐5‐ylidene (HL^Ph) under formation of the stable rhenium(V) nitrido complex [ReNCl(HL^Ph)(L^Ph)], which contains one of the two NHC ligands with an additional orthometallation. The rhenium atom in the product is five‐coordinate with a distorted square‐pyramidal coordination sphere. The position trans to the nitrido ligand is blocked by one phenyl ring of the monodentate HL^Ph ligand. The Re–C(carbene) bond lengths of 2.072(6) and 2.074(6) Å are comparably long and indicate mainly σ‐bonding between the NHC ligand and the electron deficient d² metal atom. The chloro ligand in [ReNCl(HL^Ph)(L^Ph)] is labile and can be replaced by ligands such as pseudohalides or monoanionic thiolates such as diphenyldithiophosphinate (Ph₂PS₂^?) or pyridine‐2‐thiolate (pyS^?). X‐ray structure analyses of [ReN(CN)(HL^Ph)(L^Ph)] and [ReN(pyS)(HL^Ph)(L^Ph)] show that the bonding situation of the NHC ligands (Re–C(carbene) distances between 2.086(3) and 2.130(3) Å) in the product is not significantly influenced by the ligand exchange. The potentially bidentate pyS^? ligand is solely coordinated via its thiolato functionality. Hydrogen atoms of each one of the phenyl rings come close to the unoccupied sixth coordination positions of the rhenium atoms in the solid state structures of all complexes. Re–H distances between 2.620 and 2.712Å do not allow to discuss bonding, but with respect to the strong trans labilising influence of “N^3?”, weak interactions are indicated.     

Tetra‐μ‐α‐alanine‐bis­[tetra­aqua­gadolinium(III)] hexaperchlorate

The title complex, [Gd₂(C₃H₇NO₂)₄(H₂O)₈](ClO₄)₆, contains centrosymmetric dimeric [Gd₂(Ala)₄(H₂O)₈]⁶⁺ cations (Ala is α‐alanine) and perchlorate anions. The four alanine mol­ecules act as bridging ligands linking two Gd³⁺ ions through their carboxylate O atoms. Each Gd³⁺ ion is also coordinated by four water mol­ecules, which complete an eightfold coordination in a square‐antiprism fashion. The perchlorate anions and the methyl groups of the alanine ligands are disordered.     

ZnII and CuII complexes generated from 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione

A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn₂(NO₃)₄(C₁₄H₁₂N₄OS)₂], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO₃)(C₁₄H₁₂N₄OS)₂]NO₃·1.5CH₃CN·1.5CH₂Cl₂}_n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn₂L₂ ring (dimensions 9.56 × 7.06 Å), where each Zn^II centre lies in a {ZnN₂O₄} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu^II centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu^II centres adopt a distorted square‐pyramidal CuN₄O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.     

Direct Synthesis of a Dimeric Mixed-Anions Bismuth(III) Complex: Synthesis and Structural Characterization of [Bi2(Phen)4(No3)4.4I0.6]I3 (A New Dimeric Compound)

A direct synthetic method of mixing Bi(NO₃)₃ and NaI with 1,10-phenanthroline yielded red crystals of [Bi₂(phen)₄(NO₃)_4.4I_0.6]I₃. In this complex the cationic part is in fact binuclear and contains two [Bi(phen)(NO₃)_1.7I_0.3] groups linked via a bridging NO^? ₃ anion. The I^? ₃ anion was not coordinated to bismuth(III) and the lone pair of valence electrons of the bismuth(III) ions appears to be stereochemically inactive. There are two independent NO^? ₃ anions, one coordinated to bismuth but another shares a position with I^? anion. The final results of crystallography show that 40% of these positions are occupied by NO^? ₃ anions and 60% by I^? anions that are coordinated to bismuth atom in bidentate fashion (NO^? ₃) and in unidentate fashion (I^?). An interesting point is that the I^? ₃ anion was produced by direct synthetic method (Branched tube method). There is a π-π stacking interaction between the parallel aromatic rings around the Bi(III) ion.     

Synthese und Kristallstruktur von Blei(II)‐oxidhalogenid‐Alkoholaten mit unterschiedlichen Verknüpfungsvarianten von Pb4O4‐Heterokubaneinheiten

Synthesis and Crystal Structure Determination of Lead(II) Oxide Halide Alcoholates with Different Connectivity of Pb₄O₄ Heterocubane‐like Subunits The reaction of red lead(II) oxide (Litharge) and lead(II) halide (Cl^? and Br^?) with diethylene glycole at a temperature of 180 °C leads to the isotypic compounds [Pb₆(C₄H₈O₃)O₂Cl₆] (1) and [Pb₆(C₄H₈O₃)O₂Br₆] (2) . In a similar synthesis with PbI₂ as educt at temperature of 160 °C the two modifications β‐[Pb₆(C₄H₈O₃)O₂I₆] (3) and α‐[Pb₆(C₄H₈O₃)O₂I₆] (4) were found, whereas at a reaction temperature of 180 °C [Pb₉(C₂H₄O₂)(C₄H₈O₃)O₃I₈] (5) was surprisingly obtained as product. The X‐ray diffraction data show that at a temperature of 180 °C a splitting of the ether took place. The cited compounds show cubane like subunits built by lead and oxygen atoms. These fragments are connected by alkoholate molecules. In 5 additionally an I₆ octahedra centered by lead is observed.     

Pseudohalide‐directed Assembly of Two Zinc(II) Coordination Polymers with a 3,4‐Bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole Tecton

The zinc(II) pseudohalide complexes {[Zn(L³³⁴)(SCN)₂(H₂O)](H₂O)₂}_n ( 1 ) and [Zn(L³³⁴)(dca)₂]_n ( 2 ) were synthesized and characterized using the ligand 3,4‐bis(3‐pyridyl)‐5‐(4‐pyridyl)‐1,2,4‐triazole (L³³⁴) and ZnCl₂ in presence of thiocyanate (SCN^–) and dicynamide [dca, N(CN)₂^–] respectively. Single‐crystal X‐ray structural analysis revealed that the central Zn^II atoms in both complexes have similar octahedral arrangement. Compound 1 has a 2D sheet structure bridged by bidentate L³³⁴ and double μ_N,S‐thiocyanate anions, whereas complex 2 , incorporating with two monodentate dicynamide anions, displays a two‐dimensional coordination framework bridged by tetradentate L³³⁴ ligand. Structural analysis demonstrated that the influence of pseudohalide anions plays an important role in determining the resultant structure. Both complexes were characterized by IR spectroscopy, microanalysis, and powder X‐ray diffraction techniques. In addition, the solid fluorescence and thermal stability properties of both complexes were investigated.