Three new dinuclear manganese(II) complexes with bis(μ-phosphinato)-bridges

A new series of dinuclear phosphinato-bridged manganese(II) complexes [Mn(μ-bmp)(bpy)(NO₃)]₂ (1), [Mn(μ-bmp)(phen)(NO₃)]₂·4CH₂Cl₂ (2) and [Mn₂(μ-bmp)₂(5-dmbpy)₂(NO₃)]₂ (3) where Hbmp is bis(4-methoxyphenyl)phosphinic acid, bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline and 5-dmbpy = 5,5′-dimethyl-2,2′-dipyridyl, have been synthesized and structurally characterized by X-ray crystallography. In this series, the structures consist in bis(4-methoxyphenyl)phosphinato anions (bmp) bridging the two Mn(II) centers in a syn-syn coordination mode. The coordination geometry around the Mn(II) ions in 1-3 is six-coordinate with distorted octahedral environment. The magnetic behavior of these complexes is reported. The complexes show weak antiferromagnetic coupling with |J| in the range 0.1-0.6 cm⁻¹. The magnetic properties are discussed in relation to the structural data.     

Organically pillared layered zinc hydroxides

The two organically pillared layered zinc hydroxides [Zn₂(OH)₂(ndc)], CPO-6, and [Zn₃(OH)₄(bpdc)], CPO-7, were obtained in hydrothermal reactions between 2,6-naphthalenedicarboxylic acid (ndc) and zinc nitrate (CPO-6) and 4,4′biphenyldicarboxylate (bpdc) and zinc nitrate (CPO-7), respectively. In CPO-6, the tetrahedral zinc atoms are connected by two μ₂-OH groups and two carboxylate oxygen atoms, forming infinite layers extending parallel to the bc-plane. These layers are pillared by ndc to form a three-dimensional structure. In CPO-7, the zinc hydroxide layers are containing four-, five- and six coordinated zinc atoms, and the layers are built like stairways running along the [001] direction. Each step is composed of three infinite chains running in the [010] direction. Both crystal structures were solved from conventional single crystal data. Crystal data for CPO-6: Monoclinic space group P2₁/c (No. 14), a=11.9703(7), b=7.8154(5), c=6.2428(4) Å, β=90.816(2)°, V=583.97(6) Å³ and Z=4. Crystal data for CPO-7: Monoclinic space group C2/c (No. 15), a=35.220(4), b=6.2658(8), c=14.8888(17) Å, β=112.580(4)°, V=3033.8(6) Å³ and Z=8. The compounds were further characterized by thermogravimetric- and chemical analysis.     

Molecular hexagonal perovskite: a new type of organic-inorganic hybrid conductor

An organic charge-transfer (CT) salt (BEDT-TTF)₃(MnCl₃)₂(C₂H₅OH)₂ has been synthesized by a standard electrochemical method. The crystal data are monoclinic, C2/c (#15), a=38.863(4)Å, b=6.716(1) Å, c=23.608(3) Å, β=115.007(3)°, V=5584(1) Å³, and Z=4. The structure consists of one-dimensional (1D) infinite {[MnCl₃]⁻}_∞ magnetic chains and two-dimensional (2D) organic conduction pathways. The former consists of face-sharing octahedra of manganese chloride complex ions, and dominates the magnetic properties of this compound. Such a feature of the crystal structure closely relates to transition metal hexagonal perovskite compounds, all of which are known for frustrated triangular lattices comprised of weakly interacting 1D magnetic chains. The new compound exhibits a high conductivity down to 4 K.     

Self assembly of two novel three-dimensional supramolecular networks with blue photoluminescence

Two novel photoluminescent coordination polymers of the formula [Cd(Haip)₂(H₂O)₂] · 2H₂O (1) and [Zn(aip)(atz)] · 3H₂O (2) (H₂aip = 5-aminoisophthalic acid; atz = 3-amino-1,2,4-triazole) have been synthesized through the self-assembly of metal(II) ions with H₂aip and N-containing ligands [2-amino-5-mercapto-1,3,4-thiadiazole for 1 and 3-amino-1,2,4-triazole for 2, respectively] in the presence of NaOH. These complexes were characterized by FT-IR spectroscopy, thermogravimetric analysis (TG), elemental analysis and X-ray analysis. X-ray crystallographic studies of the complexes reveal that 1 is a first example where only one carboxylate group of the H₂aip ligand participates in coordination with the metal(II) ion and it exhibits a two-dimensional framework which further assembles into a three-dimensional supramolecular network via interlayer π–π stacking interactions and strong hydrogen bonds, while 2 exhibits a two-dimensional porous architecture. The extensively strong hydrogen bonds and interlayer π–π stacking interactions in 2 lead to the formation of a three-dimensional supramolecular network. Photoluminescence properties of the compounds 1 and 2 have been examined in the solid state at room temperature. These compounds have been found to exhibit blue photoluminescence and may be good candidates for photoactive materials.     

Synthesis, characterization and properties of some metal(II) 5-(nicotinamido)isophthalate complexes

Four new complexes, {[M(NAIP)(H₂O)₄]·2H₂O}_n (M = Co (1), M = Mn (2)), {[Zn(NAIP)]·0.5H₂O}_n (3) and {Cd(NAIP)(H₂O)₂]·1.5H₂O}_n (4) [H₂NAIP = 5-(nicotinamido)-isophthalic acid] have been prepared and structurally characterized. The ligand NAIP²⁻ exhibits different coordination modes and leads to the formation of various architectures. Complexes 1 and 2 show a one-dimensional (1D) zigzag chain, where hydrogen-bonding interactions further link these chains to a three dimensional (3D) supramolecular structure. For complex 3, a 3D coordination network with a four-coordinated Zn(II) and NAIP²⁻ as a SBU was observed. Complex 4 presents a three-connected 2-fold interpenetrated 3D network with a (10, 3)-b net topology. Their luminescent and magnetic properties have been investigated in the solid state.     

Bitriazole bridged manganese(II) framework with weak ferromagnet behavior

An asymmetric bridging ligand 3,4′-bi-1,2,4-triazole (Hbtr) was used for constructing transition metal coordination polymer, and yielding a manganese(II) compound [Mn(btr)₂]_n (1) with a unique three-dimensional (3D) framework. Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic space group Fdd2 and the structure is 3D (3, 6)-connected topological framework constructed from manganese ions and μ₃-btr ligands. The magnetic investigation for compound 1 shows that it is an antiferromagnetically coupled 3D array of high-spin manganese(II) ions with long-range ordering below T = 2.6 K, which is a weak ferromagnetic state due to spin-canting.     

Synthesis, crystal structure and magnetic properties of three polynuclear manganese compounds bearing ferrocenecarboxylato ligands

The reactions of sodium ferrocenecarboxylate (FcCO₂Na) and Mn(ClO₄)₂ · 6H₂O in methanol in the presence of ancillary ligands of 1,10-phenanthroline (phen) or 2,2′-bipyridine (2,2′-bpy) produce three discrete polynuclear complexes bearing ferrocenecarboxylato ligands: [Mn₂(FcCO₂)₃(phen)₂](ClO₄) · 2CH₂Cl₂ (1), [Mn₃(FcCO₂)₆(2,2′-bpy)₂] · 2H₂O (2) and [Mn₄O₂(FcCO₂)₇(2,2′-bpy)₂]ClO₄ · 2CH₂Cl₂ · 6H₂O (3). It is shown that their composition and skeletons are tuned by the ancillary ligands and the ratios of starting materials. In dimanganese complex 1, both Mn(II) ions are pentacoordinated in a distorted trigonal bipyramidal geometry and bridged by three ferrocenecarboxylato ligands in a distorted syn-syn bridging mode, which is rare in triply carboxylato-bridged dimanganese complexes. Compound 2 presents a linear trinuclear [Mn₃(μ₂-η¹:η¹-O₂CFc)₄(μ₂-η¹:η²-O₂CFc)₂] core, in which six ferrocencarboxylato ligands show two different bridging modes. The cationic Mn₄O₂ core of 3 has a butterfly structure, in which two Mn(III) ions at “body” sites are bridged by an additional ferrocenecarboxylato ligand and they are further connected to the Mn(III) ions at “wing-tip” sites by ferrocenecarboxylato ligands. Magnetic susceptibilities of 1 and 2 were measured. Both of them mediate a weak antiferromagnetic coupling between the Mn(II) ions bridged by ferrocenecarboxylato ligands.     

Ab-initio crystal structure of hydroxy adipate of nickel and hydroxy subarate of nickel and cobalt from synchrotron powder diffraction and magnetic properties

Organic-inorganic hybrid compounds Ni(II)₅(OH)₆(C₆H₈O₄)₂(1), Ni(II)₅(OH)₆(C₈H₁₂O₄)₂(2) and Co(II)₅(OH)₆(C₈H₁₂O₄)₂(3) have a similar layered structure as determined ab initio from synchrotron powder diffraction analysis. The metal sites are octahedrally coordinated by O atoms. The slabs are built from edge-sharing octahedra in such a way that channels with an average size of 4 Å are formed. Bis-bidentate and bridging dicarboxylate anions lead to a 3D framework. The compounds (1) and (2) order antiferromagnetically below T_N=26.5 and 19.3 K, respectively, while (3) is ferrimagnetic with T_C=16.2 K. Crystal data for compounds are as follows: (1)a=11.6504(1) Å, b=6.8021(3) Å, c=6.3603(1) Å, α=73.52(1)°, β=99.69(1)°, γ=96.16(1)°, R_B=0.070, 668 reflections; (2)a=13.9325(1) Å, b=6.7893(1) Å, c=6.3534(4) Å, α=73.63(1)°, β=95.14(1)°, γ=91.80(1)°, R_B=0.052, 804 reflections; (3)a=13.9806(1) Å, b=6.9588(1) Å, c=6.3967(1) Å, α=73.05(1)°, β=94.51(1)°, γ=92.19(1)°, R_B=0.048, 410 reflections. The space group is P−1 for the three compounds.     

Magnetostructural correlations in the antiferromagnetic Co2−x Cux(OH)AsO4 (x=0 and 0.3) phases

The Co_2−xCu_x(OH)AsO₄ (x=0 and 0.3) compounds have been synthesized under mild hydrothermal conditions and characterized by X-ray single-crystal diffraction and spectroscopic data. The hydroxi-arsenate phases crystallize in the Pnnm orthorhombic space group with Z=4 and the unit-cell parameters are a=8.277(2) Å, b=8.559(2) Å, c=6.039(1) Å and a=8.316(1) Å, b=8.523(2) Å, c=6.047(1) Å for x=0 and 0.3, respectively. The crystal structure consists of a three-dimensional framework in which M(1)O₅-trigonal bipyramid dimers and M(2)O₆-octahedral chains (M=Co and Cu) are present. Co₂(OH)AsO₄ shows an anomalous three-dimensional antiferromagnetic ordering influenced by the magnetic field below 21 K within the presence of a ferromagnetic component below the ordering temperature. When Co²⁺ is partially substituted by Cu²⁺ions, Co_1.7Cu_0.3(OH)AsO₄, the ferromagnetic component observed in Co₂(OH)AsO₄ disappears and the antiferromagnetic order is maintained in the entire temperature range. Heat capacity measurements show an unusual magnetic field dependence of the antiferromagnetic transitions. This λ-type anomaly associated to the three-dimensional antiferromagnetic ordering grows with the magnetic field and becomes better defined as observed in the non-substituted phase. These results are attributed to the presence of the unpaired electron in the dx²−y² orbital and the absence of overlap between neighbour ions.     

Synthesis,crystal structure and magnetic properties of a new dinuclear copper(II) amino acid complex [Cu2(l-arg)2(μ-HPO4-O)(μ-HPO4-O,O′)(μ-OH)] · (H3O) · (H2O)6

A novel dinuclear copper(II) complex with the amino acid l-arginine (l-arg), with mono and bidentate HPO₄²⁻ oxoanions and an OH⁻ anion. [Cu₂(l-arg)₂(μ-HPO₄-O)(μ-HPO₄-O,O′)(μ-OH)]⁻ · (H₃O)⁺ · 6H₂O (1) was prepared and its structure was determined by X-ray diffraction methods. The two independent copper ions are in a distorted square pyramidal coordination, each bonded to one l-arginine molecule. These two Cu(l-arg) units are bridged by two monoatomic equatorial–apical oxygen ligands belonging to a monodentate hydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d = 3.1948(8) Å are also connected by two equatorial oxygen belonging to a bidentate hydrogenphosphate. This dinuclear character and bridging scheme, not common for metal–amino acid compounds, is a consequence of the properties of the phosphate anions. The magnetic susceptibility at temperatures between 2 and 300 K and the isothermal magnetization curves at T = 2.29(1) K with applied fields up to 9 T were measured. The magnetic data indicate an antiferromagnetic intradinuclear exchange coupling J/k_B = −3.7(1) K and using a molecular field approximation we estimated a weaker ferromagnetic interaction J′/k_B ∼ 0.3 K between neighbour dinuclear units.     

Magnetism and crystal structures of CuMn and CuNi ordered bimetallic chains

The syntheses, crystal structures and magnetic properties of the new bimetallic compounds {CuL_α[Ni(NCS)₄(H₂O)₂]} (1) and {CuL_α[Mn(NCS)₄(H₂O)₂]} (2), where L = N-dl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene, are reported. Both structures consist of well-separated and magnetically equivalent layers which are composed of thiocyanate-bridged Cu(II)–Mn(II) or Cu(II)–Ni(II) binuclear units and create infinite polymeric zig-zag-like chains in the crystal lattices. The [Ni(NCS)₄(H₂O)₂] and [Mn(NCS)₄(H₂O)₂] molecular fragments have a distorted octahedral symmetry. The geometry of the Cu(II) unit is octahedral with the apical positions occupied by bridging thiocyanate ligands and the basal ones by four nitrogen atoms from the macrocyclic ring. The shortest intramolecular M–M distances are: 6.342 Å (Cu–Ni) and 6.421 Å (Cu–Mn). Magnetic susceptibility and magnetization measurements for the examined compounds have been carried out over the range 1.8–300 K. The data suggest antiferromagnetic interactions through the thiocyanate bridge. Finally, the magnitudes of the Cu(II)–M(II) interactions (M = Ni and Mn) have been compared and qualitatively rationalised.     

Syntheses,characterization and luminescent properties of two lead(II) fumarate metal-organic frameworks

It is of interest that the hydrous 3D metal-organic framework (MOF) {[Pb₂(fum)₂(H₂O)₄] · 2H₂O}_n (1) has been synthesized by the reaction of the fum dianion with the lead(II) ion (fum = fumarate) in the presence of pyrazole, while the anhydrous 3D MOF [Pb(fum)]_n (2) is obtained by the reaction of the fum dianion with the lead(II) ion in the presence of pyrazine. These complexes were further characterized by FT-IR spectroscopy, thermogravimetric analysis (TG), X-ray analysis and solid state photoluminescence spectra. The arrangement of the ligands displays a coordination gap around the Pb atom, occupied possibly by a stereoactive lone pair of electrons on lead(II), with the coordination around both the eight-coordinated lead atom in 1 and six-coordinated lead atom in 2 exhibiting a hemidirected geometry. The fum ligand shows different ligation behavior toward the lead(II) ions in these complexes. These compounds exhibit photoluminescence with the maximum emission located in the UV region.     

meta-Phenylene-bridged double Schiff base copper(II) complexes as building blocks for 1D coordination polymers: Synthesis,crystal structure and magnetic properties

The new double Schiff-base ligands H₆ipa-hyhb and H₆ipa-hyhh were synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with 4-hydroxy-butanoic acid hydrazide (hyhb) and 6-hydroxy-hexanoic acid hydrazide (hyhh). The reaction with copper(II) perchlorate in the presence of an appropriate co-ligand (Him = imidazole, Hpz = pyrazole) leads to the novel coordination polymers {[Cu₂(H₄ipa-hyhb)(Hpz)₂](ClO₄)₂}_n (1), {[Cu₂(H₄ipa-hyhb)(Him)₂](ClO₄)₂}_n (2), and {[Cu₂-(H₄ipa-hyhh)(Hpz)₂](ClO₄)₂}_n (3). These coordination polymers are composed of primary building blocks with the general formula [Cu₂(H₄ipa-X)(L)₂]²⁺ (X = hyhb, hyhh; L = Him, Hpz) which are linked by coordination of the hydroxyl groups of the ligand side chains at the apical position of copper(II) centers of adjacent building blocks. The resulting chains possess different topologies and therefore different supramolecular structures due to the variation in length of the ligand alkyl side chains. For the complexes 1 and 2 double hydroxyalkyl-bridged distorted ladder like chains are formed. Whereas in case of complex 3 single hydroxyalkyl-bridged chains are obtained which assemble to hydrogen bonded double chains. In the case of 1 and 2 these chains are cross-linked by hydrogen bonding interactions with the perchlorate counterions, whereas for 3 additional π–π stacking interaction are observed. The temperature-dependent magnetic measurements indicate weak antiferromagnetic interactions with coupling constants J = −26.1 cm⁻¹ (1), J = −28.2 cm⁻¹ (2), and J = −26.5 cm⁻¹ (3). The magnetic exchange interaction is solely the result of a coupling within the dinuclear complex moieties through the central resorcinol moiety.     

Synthesis and characterization of a bis-μ,η-carboxylate-bridged dinuclear manganese(II) complex containing a tetradentate tripodal ligand, N-(benzimidazol-2-ylmethyl)iminodiacetic acid

The dinuclear Mn(II) complex, [Mn₂(Hbida)₂(H₂O)₂], was prepared using a tetradentate tripodal ligand, N-(benzimidazol-2-ylmethyl)iminodiacetic acid (H₃bida) which has two carboxylate and one benzimidazole groups. The manganese ions are doubly bridged using μ,η¹-bridging monodentate carboxylate oxygen atoms. The Mn–Mn bond distance of 3.446 Å in the complex is comparable to that observed in the active site of the native manganese arginase enzyme (3.30 Å). The geometry of the complex with four carboxylates in two different types of binding modes, non-bridging monodentate and μ,η¹-type bridging monodentate, mimics the active site structure of manganese arginase. The magnetic properties of the complex show a coupling constant of J = −0.471(1) cm⁻¹, which is consistent with weakly coupled antiferromagnetic Mn^II (S = 5/2) centers. The cyclic voltammograms of the Mn(II) complex in DMF show irreversible oxidation occurring around 570 mV (versus Ag/AgCl).     

Metamagnetism and long range ordering in μ-1,3 bridging transition metal thiocyanato coordination polymers

Reaction of M(SCN)₂ (M = Mn, Fe, Ni) with pyridine (pyr) in aqueous solution at room temperature leads to the formation of the literature known pyridine-rich 1:4 compounds of composition [M(SCN)₂(pyridine)₄] (M = Mn (1-Mn), Fe (1-Fe), Ni (1-Ni)) reported recently. On heating, the 1:4 compounds decompose into their corresponding pyridine-deficient 1:2 compounds of composition [M(SCN)₂(pyridine)₂]_n (M = Mn (2-Mn), Fe (2-Fe), Ni (2-Ni)) which decompose on further heating. In the crystal structure of the pyridine-deficient 1:2 compounds the metal cations are coordinated by four N-atoms of two pyridine ligands and two N-bonded thiocyanato anions, each in mutually trans orientation, and by two S-atoms of two adjacent thiocyanato anions in a slightly distorted octahedral geometry. The thiocyanato anions bridge the metal cations into one-dimensional (1D) polymeric chains. IR spectroscopic investigations on the pyridine-deficient 1:2 compounds are in agreement with the presence of μ-1,3 bridging thiocyanato anions. Magnetic measurements of the pyridine-rich 1:4 compounds show only Curie-Weiss paramagnetism whereas for the pyridine-deficient 1:2 compounds an antiferromagnetic ordering for [Mn(NCS)₂(pyridine)₂]_n (2-Mn) and metamagnetic behavior for [Ni(NCS)₂(pyridine)₂]_n (2-Ni) is found. For [Cu(NCS)₂(pyridine)₂]_n (2-Cu) Curie-Weiss paramagnetic behavior is observed. [Fe(NCS)₂(pyridine)₂]_n (2-Fe) shows metamagnetic behavior, which was already investigated but remeasured for a more detailed characterization.     

Hetero-metallic frameworks of [Pd(CN)4] and Cu(II) with triamines: A rare example of a tetracyanometallate bridged 2D coordination polymer

Four cyano bridged Cu(II)–Pd(II) heterometallic complexes, [Cu(dpt)Pd(CN)₄]_n (1), {[Cu₂(medpt)₂Pd(CN)₄](ClO₄)₂ · 3H₂O}_n (2), {[Cu₂(dien)₂Pd(CN)₄](ClO₄)₂ · 2CH₃OH}_n (3) and {[Cu₂(iPrdien)₂Pd(CN)₄](ClO₄)₂ · 2H₂O}_n (4) [dpt = 3,3′-iminobispropylamine; medpt = 3,3′-diamino-N-methyldipropylamine; dien = diethylenetriamine and iprdien = N′-isopropyldiethylenetriamine] have been synthesized and characterized by single crystal X-ray diffraction analysis, magnetic measurement and thermal study. Complexes 1, 2 and 3 are 1D coordination polymers, while 4 presents a 2D network. In 1, the cis-directed cyanide ligands of [Pd(CN)₄]²⁻ anions link two Cu(dpt) units to form a neutral coordination polymer, whereas in 2, 3 and 4, all the cyanide groups of [Pd(CN)₄]²⁻ take part in bonding with four adjacent Cu(II) ions, resulting in cationic coordination polymers counterbalanced by perchlorate anions. The structures are compared with those of analogous [Ni(CN)₄]²⁻ derivatives. The magnetic behavior shows antiferromagnetic interactions in all the complexes.     

Three-component reactions leading to 2D and 3D metal-organic frameworks assembled on dinickel-carboxylate secondary building units

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal-organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni₂(PDA)₂(BPP)(H₂O)]·2.5H₂O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal-organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.     

Syntheses and characterization of ferrocenylthiocarboxylate-containing coordination compounds for nonlinear optics

Four metal-organic coordination compounds containing ferrocenylthiocarboxylate components, [Cd₂(η²-SOCFc)₂(η¹-μ₂-SOCFc)₂(4,4′-bpy)]_n (1), [Cd(SOCFc)₂(tmp)]_n (tmp = 4,4′-trimethylene-dipyridine) (2) [Zn(SOCFc)₂(2,2′-bpy)] (3), and {[Hg(SOCFc)₂(phen)] · (0.5CH₃OH)} (4) (Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)), have been prepared in search of good nonlinear optical (NLO) materials. Investigation of the NLO properties shows that Hg-containing compound 4 exhibits very strong third-order NLO absorptive and refractive effects. The NLO absorptive coefficient α₂ value (2.11 × 10⁻¹⁰ m W⁻¹) is larger than those of all the reported ferrocenylcarboxylate-containing coordination compounds and comparable to the well-performing Hg-containing complexes. Additionally, we further analyzed their NLO behaviors through studying electrochemical properties of the four compounds.