Developing Intense Blue and Magenta Colors in α‐LiZnBO3: The Role of 3d‐Metal Substitution and Coordination

We describe the synthesis, crystal structures, and optical absorption spectra/colors of 3d‐transition‐metal‐substituted α‐LiZnBO₃ derivatives: α‐LiZn_1?xM^II_xBO₃ (M^II=Co^II (0<x<0.50), Ni^II (0<x≤0.05), Cu^II (0<x≤0.10)) and α‐Li_1+xZn_1?2xM^III_xBO₃ (M^III=Mn^III (0<x≤0.10), Fe^III (0<x≤0.25)). The crystal structure of the host α‐LiZnBO₃, which is both disordered and distorted with respect to Li and Zn occupancies and coordination geometries, is largely retained in the derivatives, which gives rise to unique colors (blue for Co^II, magenta for Ni^II, violet for Cu^II) that could be of significance for the development of new, inexpensive, and environmentally friendly pigment materials, particularly in the case of the blue pigments. Accordingly, this work identifies distorted tetrahedral MO₄ (M=Co, Ni, Cu) structural units, with a long M?O bond that results in trigonal bipyramidal geometry, as new chromophores for blue, magenta, and violet colors in a α‐LiZnBO₃ host. From the L*a*b* color coordinates, we found that Co‐substituted compounds have an intense blue color that is stronger than that of CoAl₂O₄ and YIn_0.90Mn_0.10O₃. The near‐infrared (NIR) reflectance spectral studies indicate that these compounds exhibit a moderate IR reflectivity that could be significant for applications as “cool pigments”.     

Synthese,Struktur und EPR‐Untersuchungen von binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))‐Komplexen des CuII,NiII, ZnII,CdII und PdII

Synthesis, Structure and EPR Investigations of binuclear Bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato)) Complexes of Cu^II, Ni^II, Zn^II, Cd^II and Pd^II The synthesis of binuclear Cu^II‐, Ni^II‐, Zn^II‐, Cd^II‐ and Pd^II‐complexes of the quadridentate ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and the crystal structures of the Cu^II‐ and Ni^II‐complexes are reported. The Cu^II‐complex crystallizes in two polymorphic modifications: triclinic, (Z = 1) and monoclinic, P2₁/c (Z = 2). The Ni^II‐complex was found to be isostructural with the triclinic modification of the copper complex. The also prepared Pd^II‐, Zn^II‐ and Cd^II‐complexes could not be characterized by X‐ray analysis. However, EPR studies of diamagnetically diluted Cu^II/Pd^II‐ and Cu^II/Zn^II‐powders show axially‐symmetric g and A ^Cu tensors suggesting a nearly planar co‐ordination within the binuclear host complexes. Diamagnetically diluted Cu^II/Cd^II powder samples could not be prepared. In the EPR spectra of the pure binuclear Cu^II‐complex exchange‐coupled Cu^II‐Cu^II pairs were observed. According to the large Cu^II‐Cu^II distance of about 7,50Å a small fine structure parameter D = 26·10^?4 cm^?1 is observed; T‐dependent EPR measurements down to 5 K reveal small antiferromagnetic interactions for the Cu^II‐Cu^II dimer. Besides of the dimer in the EPR spectra the signals of a mononuclear Cu^II species are observed whose concentration is T‐dependent. This observation can be explained assuming an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions.     

Synthese,Strukturen, NMR‐ und EPR‐Untersuchungen der binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato))‐Komplexe des NiII und CuII

Synthesis, Structures, NMR and EPR Investigations of Binuclear Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenoureato)) Complexes of Ni^II and Cu^II The synthesis of binuclear Cu^II and Ni^II complexes of the quadridentate ligand N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(selenourea) and their crystal structures are reported. The complexes crystallize monoclinic, P2₁/c (Z = 2). In the EPR spectra of the binuclear Cu^II complex exchange‐coupled Cu^II‐Cu^II pairs were observed. In addition the signals of a mononuclear Cu^II species are observed what will be explained with the assumption of an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions. Detailed ¹³C and ⁷⁷Se NMR investigations on the ligand and the Ni^II complex allow an exact assignment of all signals of the heteroatoms.     

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.     

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.     

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.     

Synthese,Strukturen und X‐/Q‐Band‐EPR‐Untersuchungen von N,N‐Diethyl‐N′‐3,5‐di(trifluormethyl)benzoylthioureato‐Komplexen des CuII,NiII und PdII sowie EPR‐spektroskopische Charakterisierung eines CuII‐CuII‐Dimers

The synthesis and the structures of (i) the ligand N,N‐Diethyl‐N′‐3,5‐di(trifluoromethyl)benzoylthiourea HEt₂dtfmbtu and (ii) the Ni^II and Pd^II complexes of HEt₂dtfmbtu are reported. The ligand coordinates bidendate forming bis chelates. The Ni^II and the Pd^II complexes are isostructural. The also prepared Cu^II complex could not be characterized by X‐ray analysis. However, the preparation of diamagnetically diluted powders Cu/Ni(Et₂dtfmbtu)₂ and Cu/Pd(Et₂dtfmbtu)₂ suitable for EPR studies was successful. The EPR spectra of the Cu/Ni and Cu/Pd systems show noticeable differences for the symmetry of the CuS₂O₂ unit in both complexes: the Cu/Pd system is characterized by axially‐symmetric g< and A ^cu tensors; for the Cu/Ni system g and A ^Cu have rhombic symmetry. EPR studies on frozen solutions of the Cu^II complex show the presence of a Cu^II‐Cu^II dimer which is the first observed for Cu^II acylthioureato complexes up to now. The parameters of the fine structure tensor were used for the estimation of the Cu^II‐Cu^II distance.     

5,20‐Bis(ethoxycarbonyl)‐Substituted Antiaromatic [28]Hexaphyrin and Its Bis‐NiII and Bis‐CuII Complexes

5,20‐Bis(ethoxycarbonyl)‐[28]hexaphyrin was synthesized by acid catalyzed cross‐condensation of meso‐diaryl‐substituted tripyrrane and ethyl 2‐oxoacetate followed by subsequent oxidation. This hexaphyrin was found to be a stable 28π‐antiaromatic compound with a dumbbell‐like conformation. Upon oxidization with PbO₂, this [28]hexaphyrin was converted into an aromatic [26]hexaphyrin with a rectangular shape bearing two ester groups at the edge side. The [28]hexaphyrin can incorporate two Ni^II or Cu^II metals by using the ester carbonyl groups and three pyrrolic nitrogen atoms to give bis‐Ni^II and bis‐Cu^II complexes with essentially the same dumbbell‐like structure. The antiaromatic properties of the [28]hexaphyrin and its metal complexes have been well characterized.     

Transition metal complexes with ­thiosemicarbazide‐based ligands. XLIII.

In the title compound, [ZnCl(C₂H₇N₃S)₂]Cl, the Zn^II ion is five‐coordinated in a distorted trigonal–bipyramidal arrangement, with the hydrazine N atoms located in the apical positions. The structure is stabilized by N—H?Cl hydrogen bonds, which involve both the Cl atoms and all the hydrogen donors, except for one of the two thio­amide N atoms. A comparison of the geometry of thio­semicarbazide and S‐­methyl­iso­thio­semicarbazide complexes with Zn^II, Cu^II and Ni^II shows the pronounced influence of the hydrogen‐bond network on the coordination geometry of Zn^II compounds.     

(Croconato‐κ2O,O′)bis­(1,10‐phenanthroline‐κ2N,N′)cobalt(II), and the nickel(II) and copper(II) analogues

The title complexes, [M(C₅O₅)(C₁₂H₈N₂)₂], with M = Co^II, Ni^II and Cu^II, all lie across twofold rotation axes, around which two 1,10‐phenanthroline ligands are arranged in a chiral propeller manner. The Co^II and Ni^II complexes are isostructural, with octa­hedral coordination geometry, while the local geometry of the Cu^II complex is severely distorted from octa­hedral.     

Metallkomplexe naphthyl‐substituierter Thioharnstoffderivate

Metal Complexes of Naphthyl‐substituted Thiourea Derivatives The thiourea derivative N, N‐diethyl‐N′‐2‐naphthoylthiourea ( 1 ) and three N‐(dialkylaminothiocarbonyl)‐N′‐(1‐naphthyl)‐arylamidines ( 2 ‐ 4 ) have been synthesized and Cu^II‐, Ni^II‐ and Pd^II‐complexes of them have been prepared. According to the X‐ray structure analyses 1 with Cu^II and Ni^II under deprotonation forms neutral bis‐chelates of nearly square‐planar coordination with a cis arrangement of the O and S ligator atoms. Using their N and S atoms in 1, 3 position as ligators, 2 ‐ 4 in deprotonated form coordinate to Cu^II and Pd^II as neutral bis‐chelates, in the case of Cu^II with a distorted tetrahedral coordination. Pd^II is coordinated square planar and has, probably due to the spatial influence of the 1‐naphthyl groups, a trans arrangement of the N and S ligator atoms.     

Cyano‐Bridged ‘Oximato’ Complexes: Synthesis,Structure, and Catalase‐Like Activities

The reaction of the ‘oximato’‐ligand precursor A (Fig. 1) and metal salts with KCN gave two mononuclear complexes [ML(CN)(H₂O)_n](ClO₄) ( 1 and 2 ; L={N‐(hydroxy‐κO)‐α‐oxo‐N′‐[(pyridin‐2‐yl‐κN)methyl[1,1′‐biphenyl]‐4‐ethanimidamidato‐κN′}; M=Co^II ( 1 ), Cu^II ( 2 ); n=2 for Co^II, n=0 for Cu^II; Figs. 2 and 3). The new cyano‐bridged pentanuclear ‘oximato’ complexes [{ML(H₂O)_n(NC)}₄M¹(H₂O)_x](ClO₄)₂ ( 3 – 6 ) and trinuclear complexes [{ML(H₂O)_n(NC)}₂M¹L](ClO₄) ( 7 – 10 ) ([M¹=Mn^II, Cu^II; x=2 for Mn^II, x=0 for Cu^II] were synthesized from mononuclear complexes and characterized by elemental analyses, magnetic susceptibility, molar conductance, and IR and thermal analysis. The four [ML(CN)(H₂O)_n]⁺ moieties are connected by a metal(II) ion in the pentanuclear complexe 3 – 6 , each one involving four cyano bridging ligands (Fig. 4). The central metal ion displays a square‐planar or octahedral geometry, with the cyano bridging ligands forming the equatorial plane. The axial positions are occupied by two aqua ligands in the case of the central Mn‐atom. The two [ML(CN)(H₂O)_n]⁺ moieties and an ‘oximato’ ligand are connected by a metal(II) ion in the trinuclear complexes 7 – 10 , each one involving two cyano bridging ligands (Fig. 5). The central metal ions display a distorted square‐pyramidal geometry, with two cyano bridging ligands and the donor atoms of the tridentate ‘oximato’ ligand. Moreover catalytic activities of the complexes for the disproportionation of hydrogen peroxide (H₂O₂) were also investigated in the presence of 1H‐imidazole. The synthesized homopolynuclear Cu^II complexes 6 and 10 displayed eficiency in disproportion reactions of H₂O₂ producing H₂O and dioxygen thus showing catalase‐like activity.     

The synthesis,spectroscopic and thermal study of oxamic acid compounds of some metal(II) ions

Summary The preparation of oxamic acid complexes of general formula M(H₂NCOCOO)₂·xH₂O (M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; x = 1 for Cu^II, x = 2 for the other metals) is reported. The i.r. and Raman spectra are discussed considering a trans-octahedral structure, formed by five-membered chelate rings with the amide oxygen and one carboxylic oxygen as donor atoms. The apical positions are occupied by water molecules. The thermal degradation process is very similar for the different complexes, first losing H₂O in one or different steps, then the fragments of the organic ligand to give the metal oxide as residue. The thermal degradation of the Cu^II and Zn^II compounds results in the formation of a new polymeric compound by deprotonation of the primary amide function in an endothermic process, the polymer further decomposes to form the metal oxide.     

Copper(II) and nickel(II) complexes of the pendant arm ligand benzimidazole-2-yl-methyl-functionalized 1,4,7-triazacyclononane

Two novel complexes [ML]·(ClO₄)₂·EtOH·xH₂O M = Cu^II, x = 3; M = Ni^II, x = 2; L = 1-R-4,7-bis(benzimidazole-2-yl-methyl)-1,4,7-triazacyclononane, [R = 1-(benzimidazole-2-yl-methyl)benzimidazole-2-yl-methy], were prepared by a one-pot method using the 1,4,7-triazacyclononane ligand (tacn) and 2-chloromethylbenzimidazole as starting materials. The ES-MS and u.v. spectra of the complexes indicate that they are very stable thermodynamically and kinetically in aqueous solution. The crystal structure of the Cu^II complex shows that the Cu^II centre is octahedrally coordinated by six nitrogen atoms of three benzimidazoles and tacn.     

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.     

Double‐Helix Structure in Carrageenan–Metal Hydrogels: A General Approach to Porous Metal Sulfides/Carbon Aerogels with Excellent Sodium‐Ion Storage

The metal sulfide‐carbon nanocomposite is a new class of anode material for sodium ion batteries, but its development is restricted by its relative poor rate ability and cyclic stability. Herein, we report the use of double‐helix structure of carrageenan–metal hydrogels for the synthesis of 3D metal sulfide (M_xS_y) nanostructure/carbon aerogels (CAs) for high‐performance sodium‐ion storage. The method is unique, and can be used to make multiple M_xS_y/CAs (such as FeS/CA, Co₉S₈/CA, Ni₃S₄/CA, CuS/CA, ZnS/CA, and CdS/CA) with ultra‐small nanoparticles and hierarchical porous structure by pyrolyzing the carrageenan–metal hydrogels. The as‐prepared FeS/CA exhibits a high reversible capacity and excellent cycling stability (280 mA h^?1 at 0.5 A g^?1 over 200 cycles) and rate performance (222 mA h^?1 at 5 A g^?1) when used as the anode material for sodium‐ion batteries. The work shows the value of biomass‐derived metal sulfide–carbon heterostuctures in sodium‐ion storage.     

Synthesis,Structures, and Properties of Crystalline Salts with Radical Anions of Metal‐Containing and Metal‐Free Phthalocyanines

Radical anion salts of metal‐containing and metal‐free phthalocyanines [MPc(3?)]^.?, where M=Cu^II, Ni^II, H₂, Sn^II, Pb^II, Ti^IVO, and V^IVO ( 1 – 10 ) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C?N_imine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1 – 10 show new bands at 833–1041 nm in the NIR range, whereas the Q‐ and Soret bands are blue‐shifted by 0.13–0.25 eV (38‐92 nm) and 0.04–0.07 eV (4–13 nm), respectively. Radical anions with Ni^II, Sn^II, Pb^II, and Ti^IVO have S=1/2 spin state, whereas [Cu^IIPc(3?)]^.? and [V^IVOPc(3?)]^.? containing paramagnetic Cu^II and V^IVO have two S=1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal‐free phthalocyanine radical anions [H₂Pc(3?)]^.? (linewidth of 0.08–0.24 mT), broad EPR signals are manifested (linewidth of 2–70 mT) with g‐factors and linewidths that are strongly temperature‐dependent. Salt 11 containing the [Na^IPc(2?)]^? anions as well as previously studied [Fe^IPc(2?)]^? and [Co^IPc(2?)]^? anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3?)]^.? in 1 – 10 .     

Deactivation of Cu‐Exchanged Automotive‐Emission NH3‐SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X‐ray Microscopy

To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NO_x with an ammonia reductant, we employed scanning transmission X‐ray microscopy (STXM) to study Cu‐exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000‐mile aging. X‐ray absorption near‐edge structure (XANES) measurements were performed at the Al K‐ and Cu L‐edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi‐factor‐induced catalytic deactivation. In Cu‐exchanged MFI, a transformation of Cu^II to Cu^I and Cu_xO_y was observed. We also found a spatial correlation between extra‐framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of Cu^I and tri‐coordinated Al. By inspecting both Al and Cu in fresh and aged Cu‐exchanged zeolites, we conclude that the importance of the preservation of isolated Cu^II sites trumps that of Brønsted acid sites for NH₃‐SCR activity.     

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.     

Copper(II) and Sodium(I) Complexes based on 3,7‐Diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide: Synthesis,Characterization, and Catalytic Activity

The reaction of 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane (DAPTA) with metal salts of Cu^II or Na^I/Ni^II under mild conditions led to the oxidized phosphane derivative 3,7‐diacetyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane‐5‐oxide (DAPTA=O) and to the first examples of metal complexes based on the DAPTA=O ligand, that is, [Cu^II(μ‐CH₃COO)₂(κO‐DAPTA=O)]₂ ( 1 ) and [Na(1κOO′;2κO‐DAPTA=O)(MeOH)]₂(BPh₄)₂ ( 2 ). The catalytic activity of 1 was tested in the Henry reaction and for the aerobic 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO)‐mediated oxidation of benzyl alcohol. Compound 1 was also evaluated as a model system for the catechol oxidase enzyme by using 3,5‐di‐tert‐butylcatechol as the substrate. The kinetic data fitted the Michaelis–Menten equation and enabled the obtainment of a rate constant for the catalytic reaction; this rate constant is among the highest obtained for this substrate with the use of dinuclear Cu^II complexes. DFT calculations discarded a bridging mode binding type of the substrate and suggested a mixed‐valence Cu^II/Cu^I complex intermediate, in which the spin electron density is mostly concentrated at one of the Cu atoms and at the organic ligand.