Μ2 Coordination Mode Research Articles

Front Cover: Copper(I) and Gold(I) Complexes of Aminofunctionalized Phosphinines: Synthesis and Structural Characterization (Z. Anorg. Allg. Chem. 6‐7/2023)

The cover picture shows the solid-state structure of an unusual Cu4-rhombus, which is capped by a total of four chlorido ligands. Two aminofunctionalized, aromatic phosphinines coordinate in the classical σ-coordination mode via the phosphorus lone pair to two of the four Cu(I) centers. The other two phosphinines show a rare bridging μ2-coordination mode and span two of the four Cu(I) centers. (DOI: 10.1002/zaac.202200365).

Cytosine as a root to a nonconventional layered hydroxide nanostructure

A self-assembled layered compound of formula {[Cu5(OH)8Cyt2]·2ClO4} n (1) was obtained from the direct reaction between copper perchlorate and cytosine. Thanks to its peculiar structural features, this coordination compound can be classified as an intermediate nonconventional analog of Layered Simple Hydroxides (LSHs) and Layered Double Hydroxides (LDHs), two fascinating classes of inorganic materials with variable chemical composition and structures. Like LDHs, 1 consists of positively charged layers of metal hydroxides and non-framework charge-balancing anions located between the layers. However, the hydroxide layers, similar to LSHs, contain only divalent copper(II) metal ions, supported by cytosine molecules with long contacts. Cytosine coordinates to the metal centers adopting an unusual µ3 coordination mode, the exocyclic oxygen atom simultaneously binding to three adjacent copper(II) centers. This coordination mode has not been observed with transition metal ions. This work further demonstrates that nucleobases and their derivatives, despite presenting a limited pool of molecules, can potentially afford a significantly expanded set of compounds with diverse nanostructures, owing to their multiple metal binding sites of different coordination properties and their ability to direct assembly of highly ordered structures. Their potential as building blocks should be further explored for the preparation of new bio-inorganic hybrid materials.

A novel three-dimensional copper aspartate coordination compound with efficient photoluminescence

Abstract Solvothermal reaction of a copper salt, racemic aspartic acid (AspH3), and 1,2,4-triazole (TaH) leads to a nanoporous copper aspartate, Cu4(Asp)2(Ta)2(H2O)2 · 2H2O (1). The compound was characterized by FT-IR spectroscopy and elemental analysis, and the structure was determined by single-crystal X-ray diffraction. Pairs of l-Asp3− and d-Asp3− ligands in unprecedented μ 4-1,2κO:3,4κOκN coordination modes chelate pairs of adjacent copper cations to form a centrosymmetric 8n-membered rectangular pipe, and these pipes are further bridged by copper cations in four directions of the bc plane to form a 3D porous structure with approximately rectangular channels of ~ 5 × 10 Å2 along the crystallographic a-axis. Along the corners of the rectangular channels, each Ta− ligand connects three adjacent copper cations in a μ 3 coordination mode to form the final 3D porous framework with relatively large rectangular channels of ~ 2 × 8 Å2 along the a-axis. Water molecules reside in these large channels. The thermal stability and solid-state photoluminescence properties of the title compound are also investigated.

Syntheses and characterization of dinuclear and tetranuclear AgI supramolecular complexes generated from symmetric and asymmetric molecular clips containing oxadiazole rings.

A new asymmetric ligand, 5-{3-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]phenyl}-2-(pyridin-3-yl)-1,3,4-oxadiazole (L5), which contains two oxadiazole rings, was synthesized and characterized. The assembly of symmetric 2,5-bis(pyridin-3-yl)-1,3,4-oxadiazole (L1) and asymmetric L5 with AgCO2CF3 in solution yielded two novel AgI complexes, namely catena-poly[[di-μ-trifluoroacetato-disilver(I)]-bis[μ-2,5-bis(pyridin-3-yl)-1,3,4-oxadiazole]], [Ag2(C2F3O2)2(C12H8N4O)2]n or [Ag2(μ2-O2CCF3)2(L1)2]n (1), and bis(μ3-5-{3-[5-(4-methylphenyl)-1,3,4-oxadiazol-2-yl]phenyl}-2-(pyridin-3-yl)-1,3,4-oxadiazole)tetra-μ3-trifluoroacetato-tetrasilver(I) dichloromethane monosolvate, [Ag4(C2F3O2)4(C22H15N5O2)2]·CH2Cl2 or [Ag2(μ3-O2CCF3)2(L5)]2·CH2Cl2 (2). Complex 1 displays a one-dimensional ring-chain motif, where dinuclear Ag2(CF3CO2)2 units alternate with Ag2(L1)2 macrocycles. This structure is different from previously reported Ag-L1 complexes with different anions. Complex 2 features a tetranuclear supramolecular macrocycle, in which each ligand adopts a tridentate coordination mode with the oxadiazole ring next to the p-tolyl ring coordinated and that next to the pyridyl ring free. Two L5 ligands are bound to two Ag1 centres through two oxadiazole N and two pyridyl N atoms to form a macrocycle. The other two oxadiazole N atoms coordinate to the two Ag2 centres of the Ag2(O2CCF3)4 dimer. Each CF3CO2- anion adopts a μ3-coordination mode, bridging the Ag1 and Ag2 centres to form a tetranuclear silver(I) complex. This study indicates that the donor ability of the bridging oxadiazole rings can be tuned by electron-withdrawing and -donating substituents. The emission properties of ligands L1 and L5 and complexes 1 and 2 were also investigated in the solid state.

Syntheses, structure variations and luminescent properties of rare earth metal-organic complexes modulated by multifunctional arenesulfonate and N-heterocycle

Self-assembly of 2-hydroxyl-5-carboxylbenzenesulfonic acid (H3L) and rare earth (RE) metal nitrates together with 1,10-phenanthroline (1,10-phen) generates sixteen complexes, namely, [RE(NO3)(H2O)8]·2(H2L)·2H2O (1-RE) (RE = Nd, Sm, Gd, Tb, Dy), [RE(NO3)2(H2O)6]·[RE(H2O)9]·4(H2L)·4H2O (2-RE) (RE = Ho and Y), [La(L)(H2O)3]n·3nH2O (3-La), [Eu2(L)2(1,10-phen)2(H2O)2]n·nH2O (4-Eu), [Tb2(L)2(1,10-phen)3(H2O)2]n·nH2O (5-Tb), [RE(L)(1,10-phen)2]n·nH2O (6-RE) (RE = Dy, Ho and Y), and [RE(L)(1,10-phen)(H2O)2]n (7-RE) (RE = Er, Yb and Lu), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. 1-RE and 2-RE are mononuclear complexes containing different RE(III) hydrates and H2L- counter-anions. In comparison with the room temperature self-assembly, hydrothermal reaction is more suitable for the formation of coordination polymer. The La(III) cations in 3-La are interconnected by the μ3-L3- trianions to form (4,4) layer, while the Eu(III) cations in 4-Eu are joined by two L3- trianions in different μ3 coordination modes into (4,4) layer. Polymer 5-Tb exhibits tubular structure extended by two unique L3- trianions in different μ2 and μ3 coordination modes. Polymers 6-RE and 7-RE present distinct chain structures with the extension of L3- trianions in the same μ2 coordination mode. Such structure evolutions are highly dependent on the diverse coordination modes of L3- trianion and the participation of 1,10-phen. Complexes 1-Nd, 1-Sm, 1-Gd, 2-Y, 3-La and 7-Lu exhibit violet, blue and green emissions from 362 to 502 nm, meanwhile, complexes 1-Dy and 6-Dy, 1-Tb and 5-Tb, as well as 4-Eu exhibit their characteristic green and red emissions. These results indicate that the present multifunctional H3L is a good antenna molecule for sensitizing RE(III) cations luminescence.

Structures, Magnetic and Thermodynamic Properties of a 3d–4f Mixed Metal Cluster [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+

A heterometallic 3d–4f complex with hepta-nuclear hexagonal cluster, [ErZn6(μ3-O)3(μ3-C2H4NO2)6(H2O)9]6+ (C2H4NO2 = glycine) was synthesized and characterized. The cluster belongs to hexagonal crystal system. It crystallizes in the P-6 space group. In each cluster, Er3+ ion is in the center of a prism, which is composed of six zinc atoms. Er3+ ion coordinates to nine oxygen atoms. Each glycine ligand chelates to two Zn2+ and one Er3+ ions using a μ3-coordination mode. Fluorescent, thermodynamic and magnetic studies of the cluster were performed. The complex does not show single molecule magnet behavior.

Nickel precursors based on diamagnetic and paramagnetic di(imine)pyridine ligands for magnetic materials: Synthesis, X-ray structures and magnetic studies

Abstract Structural characterization and spectroscopic studies of the (2-acetyl-6-(1-TEMPO-imino)ethyl)pyridine (pat) and the 2,6-bis(1-TEMPO-imino)ethyl)pyridine (pbtMe) ligands are presented. Their electrochemical properties are also discussed. Two new nickel complexes, [NiII(dip)(CH3CN)(H2O)2](BF4)2 (1) (dip = 2,6-(di-iminepyridine)) and [NiII(pbtMe)(CH3CN)3](BF4)2 (2) have been characterized by X-ray diffraction. The reaction of 1 with the tetraethyl ammonium pentacyanopropenide salt (Et4N)(pcp) affords the new compound [NiII(pcp)(dip)(CH3CN)](pcp) (3) for which X-ray diffraction studies evidence an usual bridging μ2 coordination mode for the pentacyanopropenide anion, leading to chains running along the [1 0 0] direction with Ni⋯Ni intra-chains distances of 10.653 A. Magnetic measurements for 3 indicate that it presents antiferromagnetic interactions that can be reproduced with a S = 1 regular chain model with g = 2.115(1) and Jchain = −0.589(5) cm−1.

Electrochemical study of azide bridged heterobimetallic films of porphyrins: Application as an impedimetric sensor

In this study, heterobimetallic films of metalloporphyrins, polyCo(II)PP and polyNi(II)PP, linked with azide (polyCoN3NiPP) were immobilized on a glassy carbon electrode. The intense FTIR absorption band at 2056cm−1, corresponding to the νasy (N3) of the bridged azide, indicates a μ2-coordination mode of polyCoN3NiPP. The electrochemical characterization of the films clearly shows that the order of deposition significantly affects the charge transfer process, correlated to the organized polymeric structure. The linked azide anion shows a reversible wave exclusively in the configuration polyNi(II)PP deposited over a film of polyCo(II)PP. The Nyquist plots of this electrode, using Fe(CN)63−/Fe(CN) 64− as redox probe, demonstrated a lower Rct and higher Kapp than other configurations. This electrode was applied as an impedimetric sensor for sulfite anion.

A Ni11 Coordination Cluster from the Use of the Di-2-Pyridyl Ketone/Acetate Ligand Combination: Synthetic, Structural and Magnetic Studies

The combined use of di-2-pyridyl ketone, (py)2CO, and acetates (MeCO2−) in nickel(II) chemistry in H2O-MeCN under basic conditions (Et3N) afforded the coordination cluster [Ni11(OH)6(O2CMe)12{(py)2C(OH)(O)}4(H2O)2] (1) in 80% yield, where (py)2C(OH)(O)− is the monoanion of the gem-diol form of (py)2CO. The complex contains a novel core topology. The core of 1 comprises a central non-linear {Ni3(μ2-OH)4}2+ subunit which is connected to two cubane {Ni4(OH)(μ3-OR)2(μ3-OR′)}4+ subunits [RO− = (py)2C(OH)(O)− and R′O− = MeCO2−] via the OH− groups of the former which become μ3. The linkage of the Ni3 subunit to each Ni4 subunit is completed by two η1:η1:μ2 and one η1:η3:μ4 MeCO2− groups. Peripheral ligation is provided by two terminal monodentate MeCO2− and two terminal aqua ligands. The (py)2C(OH)(O)− ligands adopt the η1:η1:η3:μ3 coordination mode. From the twelve MeCO2− ligands, two are η1, two η1:η3:μ4 and eight adopt the syn, syn η1:η1:μ2 coordination mode; four of the latter bridge NiII centers at opposite faces of the cubane subunits. Complex 1 is the largest nickel(II)/(py)2CO-based ligand coordination cluster discovered to date and has an extremely rare nuclearity (Ni11) in the cluster chemistry of nickel(II). Variable-temperature, solid state dc susceptibility, and variable-field magnetization studies at low temperatures were carried out on complex 1. The study of the data reveals an S = 3 ground state, which has been well rationalized in terms of known magnetostructural correlations and the structural features of 1. An attempt has also been made to interpret the magnetic properties of the undecanuclear cluster in a quantitative manner using four exchange interaction parameters and the obtained J values are discussed. The role of H2O in the solvent medium that led to 1, and the high nickel(II) and acetate to di-2-pyridyl ketone reaction ratio employed for its preparation, on the nuclearity and identity of the cluster are critically analyzed.

The new one-dimensional coordination polymer catena-poly[[diaquasodium(I)]-μ-oxalato-[diaquairon(III)]-μ-oxalato

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one-, two- or three-dimensional extended structures. Yellow single crystals of a new mixed-metal oxalate, namely catena-poly[[diaquasodium(I)]-μ-oxalato-κ(4)O(1),O(2):O(1'),O(2')-[diaquairon(III)]-μ-oxalato-κ(4)O(1),O(2):O(1'),O(2')], [NaFe(C2O4)2(H2O)4]n, have been synthesized and the crystal structure elucidated by X-ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space group I41 (Z = 4). The asymmetric unit contains one Na(I) and one Fe(III) atom lying on a fourfold symmetry axis, one μ2-bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one-dimensional chains of alternating FeO4(H2OW1)2 and NaO4(H2OW2)2 octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of the cis configuration and the μ2-coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H2O and oxalate ligands, leading to a two-dimensional framework. The structure of this new one-dimensional coordination polymer is shown to be unique among the A(I)M(III)(C2O4)2(H2O)n series. In addition, the absorption bands in the IR and UV-Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well-known ternary oxide NaFeO2.

Synthesis, Structure, and Luminescent Property of One-Dimensional Chain Copper-Bisulfonate Derived from 1,5-Naphthalenedisulfonate and Pyridine

The synthesis, structural characterization, and luminescent property of a novel coordination polymer [Cu(1,5-nds)(py)2(H2O)2]n·nH2O (1, 5-nds = 1,5-naphthalenedisulfonate, py = pyridine) is reported. The 1,5-nds cations adopt the μ2-coordination mode and act as bridged ligands coordinate to the copper ions, generating one-dimensional chain structure. The chains are assembled into a three-dimensional super-molecular architecture through hydrogen bonds. The IR spectrum and thermal analysis data are in agreement with the crystal structure of the copper complex. Compared with the ligands, the fluorescence spectrum of the complex happens red shift with the emission peaks at 392 nm and 460 nm at room temperature.

3- and 4-(α-diazobenzyl)pyridine-N-oxides as photoresponsive magnetic couplers for 2p-4f heterospin systems: formation of carbene-Tb(III) and carbene-Dy(III) single-molecule magnets.

3- and 4-(α-diazophenyl)pyridine-N-oxides, and , were prepared as new photoresponsive magnetic couplers in heterospin systems. Lanthanide dinuclear complexes, [Ln(III)(tta)3()]2; Ln(III) = Gd (), Tb (), and Dy () and tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate, bridged with in μ2 coordination mode were obtained. The obtained , , and were isostructures. The isomeric complex, [Tb(III)(tta)3()]2 was also prepared. In the carbene-Ln(III) complexes [Ln(III)(tta)3( and )]2 generated by photolysis, regioselectively interacted with the Ln(III) ions through pyridine-N-oxide, in which the magnetic coupling of was weakly ferromagnetic, while that of was insignificant. Before and after irradiation of , no SMM behavior was observed. In contrast, the Tb(III) and Dy(III) complexes being anisotropic functioned as heterospin SMMs. Before irradiation, showed no SMM behavior. After irradiation, two species showing slow magnetic relaxations were produced and one of them exhibited SMM behavior with the thermal activation barrier, Ueff/kB = 30 K, and τ0 = 5.8 × 10(-8) s. In , SMM behaviors were observed before and after irradiation, and the Ueff/kB value of 102 K (τ0 = 3.6 × 10(-7) s) before irradiation was reduced to 39 K (τ0 = 1.5 × 10(-8) s) after irradiation.

Synthesis, structure and characterization of two new metal-organic coordination polymers based on the ligand 5-iodobenzene-1,3-dicarboxylate.

Two new coordination polymers (CPs) formed from 5-iodobenzene-1,3-dicarboxylic acid (H2iip) in the presence of the flexible 1,4-bis(1H-imidazol-1-yl)butane (bimb) auxiliary ligand, namely poly[[μ2-1,4-bis(1H-imidazol-1-yl)butane-κ(2)N(3):N(3')](μ3-5-iodobenzene-1,3-dicarboxylato-κ(4)O(1),O(1'):O(3):O(3'))cobalt(II)], [Co(C8H3IO4)(C10H14N4)]n or [Co(iip)(bimb)]n, (1), and poly[[[μ2-1,4-bis(1H-imidazol-1-yl)butane-κ(2)N(3):N(3')](μ2-5-iodobenzene-1,3-dicarboxylato-κ(2)O(1):O(3))zinc(II)] trihydrate], {[Zn(C8H3IO4)(C10H14N4)]·3H2O}n or {[Zn(iip)(bimb)]·3H2O}n, (2), were synthesized and characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), solid-state UV-Vis spectroscopy, single-crystal X-ray diffraction analysis and powder X-ray diffraction analysis (PXRD). The iip(2-) ligand in (1) adopts the (κ(1),κ(1)-μ2)(κ(1), κ(1)-μ1)-μ3 coordination mode, linking adjacent secondary building units into a ladder-like chain. These chains are further connected by the flexible bimb ligand in a trans-trans-trans conformation. As a result, a twofold three-dimensional interpenetrating α-Po network is formed. Complex (2) exhibits a two-dimensional (4,4) topological network architecture in which the iip(2-) ligand shows the (κ(1))(κ(1))-μ2 coordination mode. The solid-state UV-Vis spectra of (1) and (2) were investigated, together with the fluorescence properties of (2) in the solid state.

A Novel One‐Dimensional Copper Mellitate Complex Featured by {Cu(H2O)2(urea)[C6(COO)4(COOH)2]}n2n– Polyanions

AbstractBlue monoclinic single crystals of the novel one‐dimensional [H3N‐(CH2)6‐NH3][Cu(H2O)2(urea)(μ2‐C6(COO)4(COOH)2)]·H2O coordination polymer were prepared in aqueous solution at room temperature in the presence of 1,6‐diaminohexane and urea [space group P21/n (no. 14) with a = 958.48(9), b = 1465.74(11), c = 1821.14(12) pm, β = 97.655(8)°]. The Cu2+ cation is coordinated in a square pyramidal manner by two oxygen atoms stemming from the dihydrogen mellitate tetraanion, one oxygen atom from the urea molecule, and two water molecules. The Cu–O distances are in the range of 193.3(2) and 229.4(2) pm. The connection between Cu2+ and [C6(COO)4(COOH)2]4– yields infinite chain‐like polyanions parallel to [1$\bar{}$01] with a composition of {Cu(H2O)2(urea)[C6(COO)4(COOH)2]}n2n–. The dihydrogen mellitate tetraanion adopts a μ2 coordination mode. The [(H3N–(CH2)6–NH3)]2+ cations are accommodated between the chains as counter cations. The hexane‐1,6‐diammonium cations adopt a partial synclinal conformation. The chains are connected by strong and weak hydrogen bonds. Magnetic measurements reveal a paramagnetic Curie‐Weiss behavior and a magnetic moment of 1.93 μB per Cu2+. Thermoanalytical investigations in air show that the complex is stable up to 135 °C, and the following decomposition processes yield CuO.

Two Zinc Porphyrin Complexes Obtained by One-port Reaction

Two zinc porphyrin complexes were synthesized by one-port reaction. Compound 1 is a mononuclear complex. The zinc ion is bound in the cavity of the ligand and it is coordinated by five atoms in a square pyramidal geometry. Whereas in 2, the metal ion is coordinated by six nitrogen atoms in an octahedral conformation. The porphyrin ligand is coordinated to three zinc ions with a η1–η1–η4–μ3 coordination mode. Six neighboring zinc atoms constitute a six-numbered ring in a chair structure. Besides, three neighboring zinc atoms form another triangle helical structure and the structure extends into a three-dimensional metallic polymer.

3D Coordination Network of Ag(I) Ions with μ 3 -Bridging Melamine Ligands

A new 3D silver complex [Ag(mela)(H2O)(NO3)]n (1) (mela = melamine or 2,4,6-triaminotriazine) is synthesized and characterized by single crystal X-ray diffraction, IR, and elemental analysis. The structural characterization shows that the compound crystallizes in space group C c, a = 8.181(2), b = 10.269(3) c = 11.347(3) A, β = 105.88(2)°, Z = 4. Out of several structurally characterized transition metal compounds comprising melamine, the titled complex represents a rare example of μ 3 -melamine coordination mode realized through the heterocycle nitrogen donors. The fluorescent property of complex 1 was investigated and the mechanism was validated by means of a density functional theory (DFT) calculation. A new 3D silver complex was synthesized using the 2,4,6-triaminotriazine ligand. The X-ray structural analysis shows a highly distorted trigonal bipyramidal geometry of Ag(I) ion with a rare μ3-coordination mode of the ligand achieved through the heterocyclic nitrogen donors. Emission study reveals intraligand and ligand-to-metal charge transfer in the complex.

A new 8-connected porous coordination polymer: crystal structure and selective adsorption properties

A new coordination polymer associated with cobalt ion, [Co3(Tda)3(bpp)2]·2DMF (1, Tda = thiophene-2,5-dicarboxylic acid, bpp = 1,3-bis(4-pyridyl)propane, DMF = dimethylformamide), was prepared under solvothermal conditions, and characterized by the single-crystal X-ray diffraction, element analysis, and IR spectra. Each Tda is coordinated to four CoII ions with µ4-κO : κO′ : κO″,κO‴-µ2 coordination mode and each bpp ligand is ligated to two CoII ions with anti–anti bridging mode in 1. Each cobalt(II) trimer is connected to eight adjacent Co3 units via four Tda and four bpp ligands reduced to a uninodal 8-connected topology. Sorption studies conducted on this permanently microporous material imply that it can separate carbon dioxide from nitrogen and methane with high selectivity.

Synthesis, structural characterization and magnetic behavior of a 2D bi-layer MOF, {[Ni2(C5O5)2(bpe)2]·H2O}n(bpe = 1,2-bis(4-pyridyl)ethylene)

Coordination polymers of metal-croconate (C5O52−) complex, {[Ni2(bpe)2(C5O5)2]·H2O}n (1) (bpe = 1,2-bis(-4-pyridyl)ethylene)) with two-dimensional (2D) metal–organic frameworks (MOF), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that compound 1 contains two crystallographically independent Ni(II) ions which both lie in a distorted octahedral environment bonded to two bpe nitrogen atoms and four oxygen donors from two croconates. The croconate acts as a bridging ligand with two different bridging modes, one presents a bis-bidentate adjacent μ3-coordination mode and the other a bis-bidentate μ4-coordination mode. A 2D brick-wall-like layered framework is formed by using a rectangle grid as a basic building unit through the connectivity of NiII with hybrid μ3-, μ4-croconates and bpe ligands. Two layers are then cross-linked by the other bpe ligands to complete a 2D bi-layered MOF. The TGA associated with in situXRD measurements demonstrated that 1 have quite high thermo-stability that keep their crystalline forms up to 350 °C. Magnetic measurements show the long range magnetic ordering and spin canting behavior in 1 below the critical temperature of 22 K with an approximate canting angle of 0.79°. A large coercivity of 3.5 kOe in the hysteresis loop is observed at 1.8 K, indicating that 1 is a weak hard magnet.

Tetranuclear mixed-valence Co(II/III) and binuclear Ni(II) complexes incorporating hydroxyl-rich ligand: Syntheses, structures and magnetic properties

Three complexes of composition [Co2IICo2III(H2hbhpd)2(H4hbhpd)2(H2O)2]Cl2(CH3OH)4 (1), [Co2IICo2III(H2hbhpd)2(H4hbhpd)2(H2O)2](NO3)2(CH3OH)4 (2) and [Ni2(H4hbhpd)2(NO3)](NO3)(CH3OH)1.5 (3) (H5hbhpd=2-(2-hydroxy-benzylamino)-2-hydroxymethyl-propane-1,3-diol) have been synthesized and their structures have been characterized. Complexes 1 and 2 are mixed-valence cobalt clusters and display face-sharing monovacant dicubane structures. In the complexes 1 and 2, one of the three alkyl hydroxyl groups of H5hbhpd ligand is deprotonated instead of deprotonation of phenyl hydroxyl group; thus monoanionic H4hbhpd− ligand displays novel η3, η1, η1, μ3 coordination mode. Complex 3 is binuclear, and the two metal centers of 3 are bridged by two deprotonated phenyl hydroxyl oxygen atoms and iso-orthogonalized by a nitrato group in η1η1-O,O′ coordination fashion. Variable-temperature solid-state dc magnetization studies have been performed in the temperature range 2–300K for compounds 1 and 3. Antiferromagnetic interactions were determined for 1 and ferromagnetic couplings were found for 3.

Novel silver(I)–saccharinate complexes exhibiting Ag···π and C–H···Ag close interactions with a new coordination mode of saccharinate

Two novel silver(I) complexes, namely [Ag2(μ3-sac)2(μ-nmpen)]n (1) and [Ag(sac)(mpr)]2 (2) (sac=saccharinate; nmpen=N-methyl-1,3-propanediamine; mpr=2-methyl-1-pyrroline) have been synthesized and characterized by IR spectra, thermal (TG, DTG and DTA) analysis and single crystal X-ray diffraction techniques. Complexes crystallize in the monoclinic system with the space group C2/c and P21/c, respectively. In 1, Ag(I) ion exhibits a distorted tetrahedral geometry by tridentate μ3-bridging sac and μ2-bridging nmpen ligands. The sac ligand exhibits a new μ3-coordination mode by means of μ2-bridging O atom of sulfonyl group and N atom of imino group. Furthermore, complex 1 exhibits a two-dimensional polynuclear structure. In 2, the silver(I) ion is linearly coordinated by the N atoms of a sac and a mpr ligands, forming mononuclear species. The individual molecules are linked into dimers by Ag···Csac (η1) interactions between silver(I) ion and phenyl ring of the adjacent complex and these dimers are assembled into two-dimensional layered networks through weak Ag···Ag (3.507Å), SO···Ag (2.961Å) and π···π interactions. The most interesting structural features of complexes is the presence of obvious C–H···M hydrogen-bonding interactions between the Ag centers and H atoms of nmpen or mpr ligands.