Superparamagnetic Composites Based on Ionic Resin Beads/CaCO3/Magnetite

The preparation of superparamagnetic composites obtained by CaCO₃ mineralization from supersaturate aqueous solutions is presented. The preparation was conducted in the presence of oleic acid stabilized magnetite nanoparticles as a water‐based magnetic fluid and insoluble templates as gel‐like cross‐linked polymeric beads. The presence of the magnetic particles in the composites provides a facile way for external manipulation using a permanent magnet, thus allowing the separation and extraction of magnetically modified materials. Two ion exchangers based on divinylbenzene/ethyl acrylate/acrylonitrile cross‐linked copolymer—a cation ion exchanger (CIE) and an amphoteric ion exchanger (AIE)—were used, as well as different addition orders of magnetite and CaCO₃ crystals growth precursors. The morphology of the composites was investigated by SEM, the polymorphs content by X‐ray diffraction, and the thermal stability by thermogravimetric analysis. Polymer, CaCO₃, and magnetite in the composite particles were shown to be present by energy dispersive X‐ray (EDX), XPS, and TEM. The sorption capacity for Cu^II ions was tested, as compared to samples prepared without magnetite.     

Copper immobilized on biomimetic assembled calcium carbonate/carboxymethylcellulose hybrid: a highly active recoverable catalyst for CuAAC reactions

A novel copper immobilized on biomimetic assembled carboxymethylcellulose/calcium carbonate hybrid (Cu^II@CMC/CaCO₃) as an efficient heterogeneous catalyst for the synthesis of 1,2,3-triazoles has been described herein. The fabrication of Cu^II@CMC/CaCO₃ is accomplished through a bioinspired mineralization process using sodium carboxymethylcellulose (CMC-Na) as the template and ion exchange agent, while the metathesis, nucleation, assemble, hybridization, and immobilization of Cu(II) occurred by successful treatment with CaCl₂, Na₂CO₃, and CuSO₄ in water at room temperature. The resultant Cu^II@CMC/CaCO₃ hybrid was well characterized by various analyses such as FT-IR, XRD, SEM, EDX, EDX-mapping, TEM, and TGA techniques. In the presence of low copper loading of Cu^II@CMC/CaCO₃ hybrid, benzylic halides, azide, and alkynes proceeded smoothly to afford 1,4-disubstituted 1,2,3-triazoles in high yields. The catalyst can be conveniently recovered from the reaction mixture by filter and reused for at least 5 consecutive runs with a slight drop in its catalytic activity. The remarkable activity and stability of the catalyst may be attributed to the coordination of both carboxyl and hydroxyl groups of the hybrid of CMC/CaCO₃.

     

Synthesis,Spectral, Thermal Studies of Co(II), Ni(II), Cu(II) and Zn(II)‐arginato Complexes. Crystal Structure of Monoaquabis(arginato‐κO,κN)copper(II). [Cu(arg)2(H2O)].NaNO3

Transition metal complexes of arginine (using Co(II), Ni(II), Cu(II) and Zn(II) cations separately) were synthesized and characterized by FTIR, TG/DTA‐DrTG, UV‐Vis spectroscopy and elemental analysis methods. Cu(II)‐Arg complex crystals was found suitable for x‐ray diffraction studies. It was contained, one mole Cu^II and Na⁺ ions, two arginate ligands, one coordinated aqua ligand and one solvent NO₃^? group in the asymmetric unit. The principle coordination sites of metal atom have been occupied by two N atoms of arginate ligands, two carboxylate O atoms, while the apical site was occupied by one O atom for Cu^II cation and two O atoms for Co^II, Ni^II, Zn^II atoms of aqua ligands. Although Cu^II ion adopts a square pyramidal geometry of the structure. Co^II, Ni^II, Zn^II cations have octahedral due to coordination number of these metals. Neighbouring chains were linked together to form a three‐dimensional network via hydrogen‐bonding between coordinated water molecule, amino atoms and O atoms of the bridging carboxylate groups. Cu^II complex was crystallized in the monoclinic space group P2₁, a = 8.4407(5) Å, b = 12.0976(5) Å, c = 10.2448(6) Å, V = 1041.03(10) ų, Z = 2. Structures of the other metal complexes were similar to CuII complex, because of their spectroscopic studies have in agreement with each other. Copper complex has shown DNA like helix chain structure. Lastly, anti‐bacterial, anti‐microbial and anti‐fungal biological activities of complexes were investigated.     

Synthesis,Crystal Structure,and Characterization of Two Oxamido‐bridged NiIICuIINiII Heteronuclear Complexes

Two new trinuclear complexes [Cu^II(Ni^IIX₁)₂(C₂H₅OH)₂]· (ClO₄)₂·2(CH₃OH) ( 1 ) and [Cu^II(Ni^IIX₂)₂(H₂O)]·(ClO₄)₂· 0.75(H₂O) ( 2 ) (X₁ = dianion of 5,6;13,14‐dibenzo‐7,12‐bis(ethoxycarboxyl)‐9‐methyl‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca‐7,11‐diene. X₂ = dianion of 5,6;13,14‐dibenzo‐9,10‐cyclohexano‐7,12‐bis(ethoxycarboxyl)‐2,3‐dioxo‐1,4,8,11‐tetraazacyclotetradeca7,11‐diene.) have been synthesized and characterized by single crystal X‐ray analysis, elemental analysis, IR, UV and EPR spectroscopies. The complexes consist of Ni^IICu^IINi^II heteronuclear cationic entities. The central Cu^II atom of 1 lies in an octahedral coordination environment, while that of 2 resides in a square‐pyramidal coordination sphere. The adjacent trinuclear units of 1 are linked together through π‐π stacking interactions resulting in a 1D supramolecular chain, whereas the π‐π stacking interactions between the contiguous units of 2 lead to a 2D structure. The EPR spectra of the two complexes show a signal of an axially elongated octahedral Cu^II system in 1 and an axially elongated square‐pyramidal Cu^II system in 2 , respectively. The hyperfine splitting of the Cu^II atoms (I^Cu = 3/2) has also been observed in the EPR spectra.     

Air‐Free Synthesis of a Ferrous Metal‐Organic Framework Featuring HKUST‐1 Structure and its Mössbauer Spectrum

Single crystals of the Fe^II metal‐organic framework (MOF) with 1,3,5‐benzenetricarboxylate (BTC) as a linker were solvothermally obtained under air‐free conditions. X‐ray diffraction analysis of the crystals demonstrated a structure for Fe^II‐MOF analogous to that of [Cu₃(BTC)₂] (HKUST‐1). Unlike HKUST‐1, however, the Fe^II‐MOF did not retain permanent porosity after exchange of guest molecules. The Mössbauer spectrum of the Fe^II‐MOF was recorded at 80 K in zero field yielding an apparent quadrupole splitting of ΔE_Q = 2.43 mm · s^–1, and an isomer shift of δ = 1.20 mm · s^–1, consistent with high‐spin central iron(II) atoms. Air exposure of the Fe^II‐MOF was found to result in oxidation of the metal atoms to afford Fe^III. These results demonstrate that Fe^II‐based MOFs can be prepared in similar fashion to the [Cu₃(BTC)₂], but that they lack permanent porosity when degassed.     

Postsynthetic Improvement of the Physical Properties in a Metal–Organic Framework through a Single Crystal to Single Crystal Transmetallation

A single crystal to single crystal transmetallation process takes place in the three‐dimensional (3D) metal–organic framework (MOF) of formula Mg^II₂{Mg^II₄[Cu^II₂(Me₃mpba)₂]₃}?45 H₂O ( 1 ; Me₃mpba^4?=N,N′‐2,4,6‐trimethyl‐1,3‐phenylenebis(oxamate)). After complete replacement of the Mg^II ions within the coordination network and those hosted in the channels by either Co^II or Ni^II ions, 1 is transmetallated to yield two novel MOFs of formulae Co₂^II{Co^II₄[Cu^II₂(Me₃mpba)₂]₃}?56 H₂O ( 2 ) and Ni₂^II{Ni^II₄[Cu^II₂(Me₃mpba)₂]₃}? 54 H₂O ( 3 ). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.     

Huge dielectric response and molecular motions in paddle-wheel [Cu(II)2(adamantylcarboxylate)4(DMF)2]⋅(DMF)2

The temperature‐dependent dynamic properties of [Cu^II₂(ADCOO)₄(DMF)₂]?(DMF)₂ ( 1 ) and [Cu^II₂(ADCOO)₄(AcOEt)₂] ( 2 ) crystals were examined by X‐ray crystallography, ¹H NMR spectroscopy, and measurements of the dielectric constants and magnetic susceptibilities (ADCOO=adamantane carboxylate, DMF=N,N‐dimethylformamide, and AcOEt=ethyl acetate). In both crystals, four ADCOO groups bridged a binuclear Cu^II? Cu^II bond, forming a paddle‐wheel [Cu^II₂(ADCOO)₄] structure. The oxygen atoms of two DMF molecules in crystal 1 and two AcOEt molecules in crystal 2 were coordinated at axial positions of the [Cu^II₂(ADCOO)₄] moiety, forming [Cu^II₂(ADCOO)₄(DMF)₂] and [Cu^II₂(ADCOO)₄(AcOEt)₂], respectively. Two additional DMF molecules were included in the unit cell of crystal 1 , whereas AcOEt was not included in the unit cell of crystal 2 . The structural analyses of crystal 1 at 300 K showed three‐fold rotation of the adamantyl groups, whereas rotation of the adamantyl groups of crystal 2 at 300 K was not observed. Thermogravimetric measurements of crystal 1 indicated a gradual elimination of DMF upon increasing the temperature above 300 K. The dynamic behavior of the crystallized DMF yielded significant temperature‐dependent dielectric responses in crystal 1 , which showed a huge dielectric peak at 358 K in the heating process. In contrast, only small frequency‐dependent dielectric responses were observed in crystal 2 because of the freezing of the molecular rotation of the adamantyl groups. The magnetic behavior was dominated by the strong antiferromagnetic coupling between the two S=1/2 spins of the Cu^II? Cu^II site, with magnetic exchange energies (J) of ?265 K (crystal 1 ) and ?277 K (crystal 2 ).     

Construction of Mononuclear Copper(II) and Trinuclear Cobalt(II) Complexes Based on Asymmetric Salamo‐Type Ligands

Mononuclear copper(II) and trinuclear cobalt(II) complexes, namely [Cu(L¹)]₂ · CH₂Cl₂ and [{Co(L²)(EtOH)}₂Co(H₂O)] · EtOH {H₂L¹ = 4,6‐dichloro‐6′‐methyoxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol and H₃L² = 6‐ethyoxy‐6′‐hydroxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol}, were synthesized and characterized by elemental analyses, IR and UV/Vis spectroscopy, and single‐crystal X‐ray diffraction. In the Cu^II complex, the Cu^II atom is four‐coordinate, with a N₂O₂ coordination sphere, and has a slightly distorted square‐planar arrangement. Interestingly, the obtained trinuclear Co^II complex is different from the common reported 2:3 (L:Co^II) salamo‐type Co^II complexes. Infinite 2D layer supramolecular structures are formed via abundant intermolecular hydrogen bonding and π ··· π stacking interactions in the Cu^II and Co^II complexes.     

Protein‐Assisted Synthesis of Double‐Shelled CaCO3 Microcapsules and Their Mineralization with Heavy Metal Ions

Calcium carbonate (CaCO₃) is one of the most abundant and important biominerals in nature. Due to its biocompatibility, biodegradability and nontoxicity, CaCO₃ has been investigated extensively in recent years for various fundamental properties and technological applications. Inspired by basic wall structures of cells, we report a protein‐assisted approach to synthesize CaCO₃ into a double‐shelled structural configuration. Due to varying reactivities of outer and inner shells, the CaCO₃ microcapsules exhibit different sorption capacities and various resultant structures toward different kinds of heavy metal ions, analogical to biologically controlled mineralization (BCM) processes. Surprisingly, three mineralization modes resembling those found in BCM were found with these bacterium‐like “CaCO₃ cells”. Our investigation of the cytotoxicity (MTT assay protocol) also indicates that the CaCO₃ microcapsules have almost no cytotoxicity against HepG2 cells, and they might be useful for future application of detoxifying heavy metal ions after further study.     

Combined EXAFS and DFT Structure Calculations Provide Structural Insights into the 1:1 Multi‐Histidine Complexes of CuII,CuI, and ZnII with the Tandem Octarepeats of the Mammalian Prion Protein

The metal‐coordinating properties of the prion protein (PrP) have been the subject of intense focus and debate since the first reports of its interaction with copper just before the turn of the century. The picture of metal coordination to PrP has been improved and refined over the past decade, but structural details of the various metal coordination modes have not been fully elucidated in some cases. In the present study, we have employed X‐ray absorption near‐edge spectroscopy as well as extended X‐ray absorption fine structure (EXAFS) spectroscopy to structurally characterize the dominant 1:1 coordination modes for Cu^II, Cu^I, and Zn^II with an N‐terminal fragment of PrP. The PrP fragment corresponds to four tandem repeats representative of the mammalian octarepeat domain, designated as OR₄, which is also the most studied PrP fragment for metal interactions, making our findings applicable to a large body of previous work. Density functional theory (DFT) calculations have provided additional structural and thermodynamic data, and candidate structures have been used to inform EXAFS data analysis. The optimized geometries from DFT calculations have been used to identify potential coordination complexes for multi‐histidine coordination of Cu^II, Cu^I, and Zn^II in an aqueous medium, modelled using 4‐methylimidazole to represent the histidine side chain. Through a combination of in silico coordination chemistry as well as rigorous EXAFS curve‐fitting, using full multiple scattering on candidate structures derived from DFT calculations, we have characterized the predominant coordination modes for the 1:1 complexes of Cu^II, Cu^I, and Zn^II with the OR₄ peptide at pH 7.4 at atomic resolution, which are best represented as square‐planar [Cu^II(His)₄]²⁺, digonal [Cu^I(His)₂]⁺, and tetrahedral [Zn^II(His)₃(OH₂)]²⁺, respectively.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Protonation of a Biologically Relevant CuII μ‐Thiolate Complex: Ligand Dissociation or Formation of a Protonated CuI Disulfide Species?

The proton‐induced electron‐transfer reaction of a Cu^II μ‐thiolate complex to a Cu^I‐containing species has been investigated, both experimentally and computationally. The Cu^II μ‐thiolate complex [Cu^II₂( L^MeS )₂]²⁺ is isolated with the new pyridyl‐containing ligand L^MeSSL^Me , which can form both Cu^II thiolate and Cu^I disulfide complexes, depending on the solvent. Both the Cu^II and the Cu^I complexes show reactivity upon addition of protons. The multivalent tetranuclear complex [Cu^I₂Cu^II₂( LS )₂(CH₃CN)₆]⁴⁺ crystallizes after addition of two equivalents of strong acid to a solution containing the μ‐thiolate complex [Cu^II₂( LS )₂]²⁺ and is further analyzed in solution. This study shows that, upon addition of protons to the Cu^II thiolate compound, the ligand dissociates from the copper centers, in contrast to an earlier report describing redox isomerization to a Cu^I disulfide species that is protonated at the pyridyl moieties. Computational studies of the protonated Cu^II μ‐thiolate and Cu^I disulfide species with LSSL show that already upon addition of two equivalents of protons, ligand dissociation forming [Cu^I(CH₃CN)₄]⁺ and protonated ligand is energetically favored over conversion to a protonated Cu^I disulfide complex.     

New hybrid chelating sorbents with grafted 3-aminopropionate groups based on mixed silicon,aluminum, titanium,or zirconium oxides

A series of new hybrid organo-inorganic sorbents with the 3-aminopropionate chelating group was synthesized. The synthesis includes the copolycondensation (sol—gel method) of tetraethoxysilane, 3-aminopropyltriethoxysilane, and several modifiers (MeSi(OEt)₃, EtSi(OEt)₃, Ti(OEt)₄, AlONO₃, ZrOCl₂) followed by carboxyethylation with acrylic acid. The obtained chelating sorbents were characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy, and thermogravimetry. The N-carboxylated sorbents have a higher sorption capacity with respect to metal ions (0.5–0.9 mmol g⁻¹, pH 6.3, NH₄OAc, 20 °C) than the starting sorbents with the primary amino group (0.05–0.2 mmol g⁻¹) and manifest high selectivity for copper(II) ion extraction. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1783–1788, August, 2005.     

Dioxygen Activation of a Trinuclear CuICuICuI Cluster Capable of Mediating Facile Oxidation of Organic Substrates: Competition between O‐Atom Transfer and Abortive Intercomplex Reduction

The dioxygen activation of a series of Cu^ICu^ICu^I complexes based on the ligands ( L ) 3,3′‐(1,4‐diazepane‐ 1,4‐diyl)bis(1‐{[2‐(dimethylamino)ethyl](methyl)amino}propan‐2‐ol) ( 7‐Me ) or 3,3′‐(1,4‐diazepane‐1,4‐diyl)bis(1‐{[2‐(diethylamino)ethyl](ethyl)amino}propan‐2‐ol) ( 7‐Et ) forms an intermediate capable of mediating facile O‐atom transfer to simple organic substrates at room temperature. To elucidate the dioxygen chemistry, we have examined the reactions of 7‐Me , 7‐Et , and 3,3′‐(1,4‐diazepane‐1,4‐diyl)bis[1‐(4‐methylpiperazin‐1‐yl)propan‐2‐ol] ( 7‐N‐Meppz ) with dioxygen at ?80, ?55, and ?35 °C in propionitrile (EtCN) by UV‐visible, 77 K EPR, and X‐ray absorption spectroscopy, and 7‐N‐Meppz and 7‐Me with dioxygen at room temperature in acetonitrile (MeCN) by diode array spectrophotometry. At both ?80 and ?55 °C, the mixing of the starting [Cu^ICu^ICu^I( L )]¹⁺ complex ( 1 ) with O₂‐saturated propionitrile (EtCN) led to a bright green solution consisting of two paramagnetic species: the green dioxygen adduct [Cu^IICu^II(μ‐η²:η²‐peroxo)Cu^II( L )]²⁺ ( 2 ) and the blue [Cu^IICu^II(μ‐O)Cu^II( L )]²⁺ species ( 3 ). These observations are consistent with the initial formation of [Cu^IICu^II(μ‐O)₂Cu^III( L )]¹⁺ ( 4 ), followed by rapid abortion of this highly reactive species by intercluster electron transfer from a second molecule of complex 1 to give the blue species 3 and subsequent oxygenation of the partially oxidized [Cu^IICu^ICu^I( L )]²⁺ ( 5 ) to form the green dioxygen adduct 2 . Assignment of 2 to [Cu^IICu^II(μ‐η²:η²‐peroxo)Cu^II( L )]²⁺ is consistent with its reactivity with water to give H₂O₂ and the blue species 3 , as well as its propensity to be photoreduced in the X‐ray beam during X‐ray absorption experiments at room temperature. In light of these observations, the development of an oxidation catalyst based on the tricopper system requires consideration of the following design criteria: 1) rapid dioxygen chemistry; 2) facile O‐atom transfer from the activated cluster to substrate; and 3) a suitable reductant to rapidly regenerate complex 1 to accomplish efficient catalytic turnover.     

Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu‐SSZ‐13

Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged Cu^II ions evidence both Cu^II and Cu^I ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH₃ together are necessary for Cu^II reduction to Cu^I. DFT calculations show that NO‐assisted NH₃ dissociation is both energetically favorable and accounts for the observed Cu^II reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu^I upon reduction, which we quantify in separate titration experiments. Both NO and O₂ are necessary for oxidation of Cu^I to Cu^II, which DFT suggests to occur by a NO₂ intermediate. Reaction of Cu‐bound NO₂ with proximal NH₄⁺ completes the catalytic cycle. N₂ is produced in both reduction and oxidation half‐cycles.     

2D Compound Constructed by Cu3 Units with Mixed Azido and Tetrazole Double Bridges: Synthesis,Structure, and Theoretical Study on Magnetic Properties

The two‐dimensional (2D) layer Cu^II compound [Cu₃(L)₂(N₃)₄] ( 1 ) [L = 2‐amino‐3‐(5‐tetrazole)‐methyate‐N‐pyridine] was synthesized by in‐situ hydrothermal reaction of CuCl₂ · 2H₂O, NaN₃, and 3‐(5‐tetrazole)‐methyate‐N‐pyridine. The central Cu1 and Cu2 atoms are located in five‐coordinate and six‐coordinate arrangements, respectively. Three Cu^II ions are linked by mixed double EO (end‐on)‐azido‐tetrazole bridges to give trinuclear Cu^II clusters, which are further extended by EE (end‐to‐end) azido bridges to form 2D metal‐organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –849 cm^–1) revealed that the double EO‐azido‐tetrazole bridges transmit antiferromagnetic coupling between Cu^II ions.     

Postsynthetic Metal and Ligand Exchange in MFU‐4l: A Screening Approach toward Functional Metal–Organic Frameworks Comprising Single‐Site Active Centers

The isomorphous partial substitution of Zn²⁺ ions in the secondary building unit (SBU) of MFU‐4l leads to frameworks with the general formula [M_xZn_(5–x)Cl₄(BTDD)₃], in which x≈2, M=Mn^II, Fe^II, Co^II, Ni^II, or Cu^II, and BTDD=bis(1,2,3‐triazolato‐[4,5‐b],[4′,5′‐i])dibenzo‐[1,4]‐dioxin. Subsequent exchange of chloride ligands by nitrite, nitrate, triflate, azide, isocyanate, formate, acetate, or fluoride leads to a variety of MFU‐4l derivatives, which have been characterized by using XRPD, EDX, IR, UV/Vis‐NIR, TGA, and gas sorption measurements. Several MFU‐4l derivatives show high catalytic activity in a liquid‐phase oxidation of ethylbenzene to acetophenone with air under mild conditions, among which Co‐ and Cu derivatives with chloride side‐ligands are the most active catalysts. Upon thermal treatment, several side‐ligands can be transformed selectively into reactive intermediates without destroying the framework. Thus, at 300 °C, Co^II‐azide units in the SBU of Co‐MFU‐4l are converted into Co^II‐isocyanate under continuous CO gas flow, involving the formation of a nitrene intermediate. The reaction of Cu^II‐fluoride units with H₂ at 240 °C leads to Cu^I and proceeds through the heterolytic cleavage of the H₂ molecule.     

The Coordination Chemistry of the Versatile Ligand Bis(2‐pyridylthio)methane

Bis(2‐pyridylthio)methane [bpytm, (pyS)₂CH₂] and complexes of this ligand with Zn^II, Hg^II, Cu^I, and Ag^I have been prepared and characterised by elemental analysis, by IR, Raman and ¹H and ¹³C NMR spectroscopy, and by X‐ray diffractometry. The ligand is N, N′‐didentate in the Zn^II complexes; N‐monodentate in one Hg^II complex and N, N′‐bis(monodentate) in the other; N‐mono‐N′, S‐didentate in the Cu^I complex; and N, S′‐bis(mono)‐N′, S‐didentate in the Ag^I complex. The structural parameters of the ligand in each coordination mode are compared with those of the free ligand and those of the triiodide salt of the protonated ligand.     

Tuning the Stability of CaCO3 Crystals with Magnesium Ions for the Formation of Aragonite Thin Films on Organic Polymer Templates

Thin‐film growth of aragonite CaCO₃ on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg²⁺ into a supersaturated solution of CaCO₃. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg²⁺ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg²⁺. Molecular dynamics simulation of the CaCO₃ precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg²⁺. The role for ionic additives in the crystallization of CaCO₃ on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.     

A one‐dimensional coordination polymer based on a di‐Schiff base supported trinuclear CuII subunit

A novel one‐dimensional Cu^II coordination polymer, catena‐poly[bis(μ₄‐3‐{[2‐(3‐hydroxy‐2‐oxidobenzylidene)hydrazinylidene]methyl}benzene‐1,2‐diolato)dimethanoltricopper(II)], [Cu₃(C₁₄H₁₀N₂O₄)₂(CH₃OH)₂]_n, (I), was constructed with a di‐Schiff base supported centrosymmetric trinuclear Cu^II subunit. In the subunit, two peripheral symmetry‐related Cu^II cations have square‐pyramidal CuNO₄ geometry and the central third Cu^II cation lies on an inversion centre with octahedral CuN₂O₄ geometry. In (I), each partially deprotonated di‐Schiff base 3‐{[2‐(3‐hydroxy‐2‐oxidobenzylidene)hydrazinylidene]methyl}benzene‐1,2‐diolate ligand (Hbcaz³⁻) acts as a heptadentate ligand to bind the Cu^II centres into chains along the a axis. A centrosymmetric Cu₂O₂ unit containing an asymmetrically bridging O atom, being axial at one Cu atom and equatorial at the other Cu atom, links the trinuclear Cu^II subunit into a one‐dimensional chain, which is reinforced by intramolecular phenol–methanol O—H...O and methanol–phenolate O—H...O hydrogen bonds. Interchain π–π stacking interactions between pyrocatechol units, with a distance of 3.5251 (18) Å, contribute to the stability of the crystal packing.