Bismetal Complexes of 5,20‐Bis(5‐formyl‐2‐pyrrolyl)‐[26]hexaphyrin(1.1.1.1.1.1) Exhibiting Strong Near‐Infrared Region Absorptions

[26]Hexaphyrin(1.1.1.1.1.1) bearing two 5‐formyl‐2‐pyrrolyl groups at the 5‐ and 20‐positions was prepared by cross‐condensation of 5,10‐bis(pentafluorophenyl)‐substituted tripyrrane with 2,5‐diformylpyrrole as an effective binuclear metal‐coordinating ligand, owing to the two hemiporphyrin‐like NNNN pockets. In fact, metalation of this hexaphyrin with Zn^II, Cu^II, and Pd^II salts proceed smoothly at room temperature to give the corresponding bismetal complexes that displayed remarkably redshifted absorption spectra reaching deep into near infrared region. These redshifted absorption bands are ascribed, through electrochemical investigations and DFT calculations, to two structural motifs: the N‐metalopyrrole substructure that elevates the HOMO level due to the electron‐donating property and the two coordinated metal ions that serve as Lewis acids to lower the LUMO level.     

Encapsulation of Metalloporphyrins in a Self‐Assembled Cubic M8L6 Cage: A New Molecular Flask for Cobalt–Porphyrin‐Catalysed Radical‐Type Reactions

The synthesis of a new, cubic M₈L₆ cage is described. This new assembly was characterised by using NMR spectroscopy, DOSY, TGA, MS, and molecular modelling techniques. Interestingly, the enlarged cavity size of this new supramolecular assembly allows the selective encapsulation of tetra(4‐pyridyl)metalloporphyrins (M^II(TPyP), M=Zn, Co). The obtained encapsulated cobalt–porphyrin embedded in the cubic zinc–porphyrin assembly is the first example of a catalytically active encapsulated transition‐metal complex in a cubic M₈L₆ cage. The substrate accessibility of this system was demonstrated through radical‐trapping experiments, and its catalytic activity was demonstrated in two different radical‐type transformations. The reactivity of the encapsulated Co^II(TPyP) complex is significantly increased compared to free Co^II(TPyP) and other cobalt–porphyrin complexes. The reactions catalysed by this system are the first examples of cobalt–porphyrin‐catalysed radical‐type transformations involving diazo compounds which occur inside a supramolecular cage.     

Entropy‐Driven Mechanochemical Synthesis of Polymetallic Zeolitic Imidazolate Frameworks for CO2 Fixation

High‐entropy materials refer to a kind of materials in which five or more metal species were incorporated deliberately into a single lattice with random occupancy. Up to now, such a concept has been only restricted to hard materials, such as high‐entropy alloys and ceramics. Herein we report the synthesis of hybrid high‐entropy materials, polymetallic zeolitic imidazolate framework (also named as high‐entropy zeolitic imidazolate framework, HE‐ZIF), via entropy‐driven room‐temperature mechanochemistry. HE‐ZIF contains five metals including Zn^II, Co^II, Cd^II, Ni^II, and Cu^II which are dispersed in the ZIF structure randomly. Moreover, HE‐ZIF shows enhanced catalytic conversion of CO₂ into carbonate compared with ZIF‐8 presumably a result of the synergistic effect of the five metal ions as Lewis acid in epoxide activation.     

Structural Variety of Cobalt(II), Nickel(II), Zinc(II), and Cadmium(II) Complexes with 4,4′‐Azopyridine: Synthesis,Structure and Luminescence Properties

Self‐assembled bi‐ and polymetallic complexes of Co^II, Ni^II, Zn^II, and Cd^II were obtained by the reaction of 4,4′‐azopyridine (azpy) with metal tri‐tert‐butoxysilanethiolates (Co, 1 ; Cd, 2 ), acetylacetonates (Ni, 3 ; Zn, 4 ), and acetates (Cd, 5 ). All compounds were characterized by single‐crystal X‐ray structure analysis, elemental analysis, FTIR spectroscopy, and thermogravimetry. Complexes 1 , 2 and 4 , 5 exhibit diverse structural conformations: 1 is bimetallic, 2 and 4 are 1D coordination polymers, and 5 is a 2D coordination framework formed from bimetallic units. The obtained complexes contain metal atoms bridged by a molecule of azpy. The luminescent properties of 1–5 were investigated in the solid state.     

Triesterase and Promiscuous Diesterase Activities of a Di‐CoII‐Containing Organophosphate Degrading Enzyme Reaction Mechanisms

The reaction mechanism for the hydrolysis of trimethyl phosphate and of the obtained phosphodiester by the di‐Co^II derivative of organophosphate degrading enzyme from Agrobacterium radiobacter P230(OpdA), have been investigated at density functional level of theory in the framework of the cluster model approach. Both mechanisms proceed by a multistep sequence and each catalytic cycle begins with the nucleophilic attack by a metal‐bound hydroxide on the phosphorus atom of the substrate, leading to the cleavage of the phosphate‐ester bond. Four exchange‐correlation functionals were used to derive the potential energy profiles in protein environments. Although the enzyme is confirmed to work better as triesterase, as revealed by the barrier heights in the rate‐limiting steps of the catalytic processes, its promiscuous ability to hydrolyze also the product of the reaction has been confirmed. The important role played by water molecules and some residues in the outer coordination sphere has been elucidated, while the binuclear Co^II center accomplishes both structural and catalytic functions. To correctly describe the electronic configuration of the d shell of the metal ions, high‐ and low‐spin arrangement jointly with the occurrence of antiferromagnetic coupling, have been herein considered.     

Rational Approach Towards Designing Metallogels From a Urea‐Functionalized Pyridyl Dicarboxylate: Anti‐inflammatory,Anticancer, and Drug Delivery

A structural rationale was adopted to design a series of metallogels from a newly synthesized urea‐functionalized dicarboxylate ligand, namely, 5‐[3‐(pyridin‐3‐yl)ureido]isophthalic acid ( PUIA ), that produces metallogels upon reaction with various metal salts (Cu^II, Zn^II, Co^II, Cd^II, and Ni^II salts) at room temperature. The gels were characterized by dynamic rheology and transmission electron microscopy (TEM). The existence of a coordination bond in the gel state was probed by FTIR and ¹H NMR spectroscopy in a Zn^II metallogel (i.e., MG2 ). Single crystals isolated from the reaction mixture of PUIA and Co^II or Cd^II salts characterized by X‐ray diffraction revealed lattice inclusion of solvent molecules, which was in agreement with the hypothesis based on which the metallogels were designed. MG2 displayed anti‐inflammatory response (prostaglandin E₂ assay) in the macrophage cell line (RAW 264.7) and anticancer properties (cell migration assay) on a highly aggressive human breast cancer cell line (MDA‐MB‐231). The MG2 metallogel matrix could also be used to load and release (pH responsive) the anticancer drug doxorubicin. Fluorescence imaging of MDA‐MB‐231 cells treated with MG2 revealed that it was successfully internalized.     

Bis[tris(2,2′‐bipyridyl‐κ2N,N′)cobalt(II)] cyclo‐tetravanadate undecahydrate

The title compound, [Co(C₁₀H₈N₂)₃]₂[V₄O₁₂]·11H₂O, is composed of two symmetry‐related cations containing octahedrally coordinated Co^II ions, a centrosymmetric [V₄O₁₂]⁴⁻ anion with an eight‐membered ring structure made up of four VO₄ tetrahedra, and 11 solvent water molecules. The Co^II cations and vanadate anions are isolated and build cation and anion layers, respectively. In addition, the title compound exhibits a three‐dimensional network through intra‐ and intermolecular hydrogen‐bond interactions between water molecules and O atoms of the anions, and the crystal structure is stabilized mainly by hydrogen bonds.     

Pressure‐Induced Conversion of a Paramagnetic FeCo Complex into a Molecular Magnetic Switch with Tuneable Hysteresis

A key challenge in the design of magnetic molecular switches is to obtain bistability at room temperature. Here, we show that application of moderate pressure makes it possible to convert a paramagnetic Fe^III₂Co^II₂ square complex into a molecular switch exhibiting a full dia‐ to paramagnetic transition: Fe^IICo^III ? Fe^IIICo^II. Moreover, the complex follows a rare behavior: the higher the pressure, the broader the magnetic hysteresis. Thus, the application of an adequate pressure allows inducing a magnetic bistability at room temperature with predictable hysteresis width. The structural studies at different pressures suggest that the pressure‐enhanced bistability is due to the strengthening of intermolecular interactions upon pressure increase. An original microscopic Ising‐like model including pressure effects is developed to simulate this unprecedented behavior. Overall, this study shows that FeCo complexes could be very sensitive piezo switches with potential use as sensors.     

Antimony‐ and Bismuth‐Based Chalcogenides for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) have received much attention, owing to their great potential for large‐scale application. A lack of efficient anode materials with high reversible capacity is one main challenge facing the development of SIBs. Antimony‐ and bismuth‐based chalcogenides materials can store large amounts of Na⁺ ions, owing to the alloying/dealloying reaction mechanism within a low potential range, and thus, are regarded as promising anodes for SIBs. However, these materials face great challenges of poor ion diffusion rate, multiple phase transformations, and severe morphology pulverization. Herein, recent developments in antimony‐ and bismuth‐based chalcogenides materials, mainly rational structural design strategies used and the electrochemical reaction mechanisms involved, are summarized. Perspectives for further improving antimony‐ and bismuth‐based chalcogenides anodes are also provided.     

Thermal Cleavage of Cyclobutane Rings in Photodimerized Coordination‐Polymeric Sheets

Three coordination polymers, [Cd₂(pvba)₂(tbdc)(dmf)₂] ( 1 ), [Co₂(pvba)₂(tbdc)(dmf)₂(H₂O)₂] ( 2 ), and [Ni₂(pvba)₂(tbdc)(dmf)₂(H₂O)₂] ( 3 ) (H₂tbdc=2,3,5,6‐tetrabromobenzenedicarboxylic acid, Hpvba=trans‐2‐(4′‐pyridyl)vinylbenzoic acid), were synthesized by solvothermal methods. The solid‐state structures of compounds 1 and 2 were determined by X‐ray crystallography. In compounds 1 and 2 , the bimetallic cores acted as secondary building units that connected the tbdc ligands in one direction and a pair of pvba ligands, which were aligned in a head‐to‐tail parallel manner, in the orthogonal direction to form sheet structures. The C?C bonds in these pvba ligand pairs in all three compounds were well‐aligned to undergo quantitative [2+2] cycloaddition reactions in the solid state under UV irradiation, thereby yielding their cyclobutane derivatives. This photochemical reaction appeared to facilitate structural transformations from one 2D structure into another in the solid state. The photoreactive Co^II‐ and Ni^II coordination polymers exhibited a reversible dehydration–rehydration reaction that was accompanied by color changes from pink to purple and green to yellow, respectively, owing to a change in coordination number from six to five. Magnetic studies showed that compound 2 was an antiferromagnet, which displayed a field‐dependent transition with a critical field (H_c) of 40 kOe at 2 K; the antiferromagnetic interaction between the Co₂ units was strengthened and weakened by dehydration and UV irradiation, respectively. The cyclobutane ligand in the photodimerized products was cleaved on heating to yield a mixture of trans‐ and cis‐isomers of pvba, as monitored by ¹H NMR spectroscopy. The Cd^II coordination polymer underwent quantitative cleavage of the cyclobutane ring whilst the other two underwent partial cleavage.     

A novel two‐dimensional cobalt(II) complex composed of one‐dimensional twisted pair‐like chains: poly[[tetraaquabis(μ3‐pyridine‐2,5‐dicarboxylato‐κ4N,O2:O5:O5′)dicobalt(II)] dihydrate]

A novel neutral polymer, {[Co₂(C₇H₃NO₄)₂(H₂O)₄]·2H₂O}_n, was hydrothermally synthesized using pyridine‐2,5‐dicarboxylate (2,5‐PDC²⁻) as the organic linker. It features a two‐dimensional layer structure constructed from one‐dimensional {[Co(2,5‐PDC)₂]²⁻}_n chains interlinked by [Co(H₂O)₄]⁺ units. The two Co^II cations occupy special positions, sitting on inversion centres. Each 2,5‐PDC²⁻ anion chelates to one Co^II cation via the pyridine N atom and an O atom of the adjacent carboxylate group, and links to two other Co^II cations in a bridging mode via the O atoms of the other carboxylate group. In this way, the 2,5‐PDC²⁻ ligand connects three neighbouring Co^II centres to form a two‐dimensional network. The two‐dimensional undulating layers are linked by extensive hydrogen bonds to form a three‐dimensional supramolecular structure, with the uncoordinated solvent molecules occupying the interlamellar region.     

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 .     

Counter‐Anion‐Regulated Mixed‐Valency of Cobalt(II/III) Centers in a Metallosupramolecular Framework

A diamagnetic Au^I₄Co^III₂ hexanuclear complex, [Au₄Co₂(dppe)₂(l ‐nmc)₄]²⁺ ([ 1_{L ‐ nmc} ]²⁺; dppe=1,2‐bis(diphenylphosphino)ethane, l ‐H₂nmc=N‐methyl‐l ‐cysteine), was newly synthesized by the reaction of [Co(l ‐nmc)₂]^? with [Au₂Cl₂(dppe)] and crystallized with different inorganic anions (X=ClO₄^?, NO₃^?, Cl^?, SO₄^2?) to produce ionic solids ([ 1_{L ‐ nmc} ]X_n). Single‐crystal X‐ray analysis revealed that all the solids crystallize in the chiral space group F432 with a face‐centered‐cubic lattice structure consisting of supramolecular octahedra of complex cations. The paramagnetic nature of all the solids was evidenced by magnetic susceptibility measurements, showing the variation of the oxidation states of two cobalt centers in [ 1_{L ‐ nmc} ]ⁿ⁺ from Co^II_1.00Co^III_1.00 for X=ClO₄^? or NO₃^? to Co^II_0.67Co^III_1.33 for X=Cl^?, via Co^II_0.83Co^III_1.17 for X=SO₄^2?. The difference in the Co^II/III mixed‐valences was explained by the difference in sizes and charges of counter anions accommodated in lattice interstices with a fixed volume.     

Isomorphous Catena Transition Metal Squarates [MII(C4O4)(dmso)2(OH2)2] (M = Co,Mn) and Magnetic Investigation into their Solid Solution M = CoxMn1–x

The crystal structures of two new isomorphous transition metal squarato complexes [M^II(C₄O₄)(dmso)₂(OH₂)₂] [M^II = Co^II (3d⁷), Mn^II (3d⁵); dmso = dimethylsulfoxide] and their magnetic properties are reported. The compounds feature two symmetrically independent chains, in which 1,3‐bridging squarato ligands connect cations in distorted octahedral surroundings of pseudo‐symmetry D_4h. From an equimolar solution of CoCl₂ · 6H₂O and MnCl₂ · 2H₂O a mixed‐metal coordination polymer crystallizes; it represents a solid solution and adopts the same structure as the corresponding monometallic compounds. The results of the diffraction experiment unambiguously proof the presence of both Co^II and Mn^II cations in either independent site albeit no precise ratio between the metal cations involved may be deduced from these findings. The difference in the magnetic properties between Co^II and Mn^II cations in the given ligand field has allowed us to establish their ratio in the solid solution more reliably than by X‐ray diffraction: Accounting for ligand field potential and spin‐orbit coupling of Co^II and regarding Mn^II as a pure spin system, the calculations yielded a fraction of 73 % Co^II in the mixed‐metal polymer. With respect to superexchange effects only weak antiferromagnetic interactions have been detected for the three coordination polymers.     

A New Sulfur‐containing Schiff‐Base Ligand and Binding to Copper(II) and Cobalt(II)

A new Schiff‐base ligand having a potentially coordinating thioether group (2‐quinoline‐N‐(2′‐methylthiophenyl)methyleneimine, qmtpm ) has been prepared. The synthesis, structure, UV‐Vis and EPR studies of one copper(II) and two cobalt(II) complexes from this ligand is reported. The X‐ray structures of the Cu^II and Co^II chlorido complexes 1 and 2 reveal the metal atoms in highly distorted square‐pyramidal environments constituted of one tridentate ligand and two anions. On the other hand, the thiocyanato Co^II compound 3 exhibits a distorted trigonal‐bipyramidal structure. These structural variations are apparently due to the different counter‐ions which leads to distinct lattice interactions. The spectroscopic data obtained by EPR and UV‐Vis investigations are in agreement with the solid‐state structures of the coordination compounds.     

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.     

Heterotrimetallic Mixed‐Valent Molecular Precursors Containing Periodic Table Neighbors: Assignment of Metal Positions and Oxidation States

A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [Co^II(hfac)₃?Na?Co^III(acac)₃] ( 1 ). This was used as a template structure to develop heterotrimetallic molecules [Co^II(hfac)₃?Na?Fe^III(acac)₃] ( 2 ) and [Ni^II(hfac)₃?Na?Co^III(acac)₃] ( 3 ) via isovalent site‐specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple‐wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di‐ and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O₄ functional oxide materials.     

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.     

Group 9 Metal Complexes of meso‐Aryl‐Substituted Rubyrin

The metalation of meso‐tetrakis(pentafluorophenyl)‐substituted [26]rubyrin has been explored with Group 9 metal salts (Rh^I, Co^II, Ir^III), affording a Hückel aromatic [26]rubyrin–bis‐Rh^I complex with a highly curved gable‐like structure, a Hückel antiaromatic [24]rubyrin–bis‐Co^II complex that displays intramolecular antiferromagnetic coupling between the two Co^II ions (J=?4.5 cm^?1), and two Cp*‐capped Ir^III complexes; in one, the iridium metal sits on the [26]rubyrin frame with two Ir?N bonds, whereas the other has an additional Ir?C bond, although both Ir^III complexes display moderate aromatic character. This work demonstrates characteristic metalation abilities of this [26]rubyrin toward Group 9 metals.     

[62]Tetradecaphyrin and Its Mono‐ and Bis‐ZnII Complexes

A coiled structure of meso‐pentafluorophenyl‐substituted [62]tetradecaphyrin 1 was revealed by X‐ray structural analysis. Synthetic protocols were devised to form mono‐ and bis‐Zn^II complexes, 1 Zn and 1 Zn₂ , selectively. The former displayed a trigonal‐bipyramidal pentacoordinated Zn^II ion as a rare case and a cyclic voltammogram exhibiting eleven reversible redox waves. The latter showed a Ci‐symmetric structure with modest Hückel aromaticity owing to a 62 π‐electronic circuit as the largest aromatic molecule to date.