Synthesis, structure, and magnetism of a binuclear Co(II) complex of a potentially bis-tridentate verdazyl radical ligand

The synthesis, structure, and magnetic properties of a dinuclear Co(II) complex of a tridentate verdazyl radical are presented. The reaction of a tetrazane containing a 4,6-bis(2-pyridyl)-pyrimid-2-yl substituent with cobalt chloride hexahydrate in aerated solution leads to in situ oxidation of the tetrazane to a verdazyl radical which is coordinated to Co(II) in a tridentate manner. The second tridentate coordination site of the verdazyl remains vacant. The crystal structure reveals the complex to be dimeric, with the cobalt ions linked by two bridging chlorides. The structure of Co₂Cl₂ core is highly asymmetric, with two short (2.3317 Å) and two long (2.744 Å) Co-Cl bonds. There are relatively short intermolecular contacts between coordinated verdazyl radicals in the solid state. Magnetic susceptibility data from 2 to 300 K suggest intramolecular ferromagnetic interactions, and modeling of the high-temperature data produced a best fit with J_Co-verdazyl of +20 cm⁻¹.     

Synthesis, characterization, and crystal structure of a quadruply bonded dimolybdenum(II) complex containing the water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane (PTA)

The quadruply bonded molybdenum(II)-molybdenum(II) complex, tetrachlorotetrakis(1,3,5-triaza-7-phosphaadamantane) dimolybdenum(II), Mo₂Cl₄(PTA)₄, was synthesized by reaction of 1,3,5-triaza-7-phosphaadamantane (PTA) with K₄[Mo₂Cl₈] in refluxing methanol. The complex was characterized using ¹H and ³¹P NMR, and UV-Vis spectroscopy, X-ray crystallography, and cyclic voltammetry. The Mo-Mo separation in the solid state structure is 2.13 Å, with the PTA and chloride ligands in an eclipsed arrangement with a P-Mo-Mo-Cl twist angle of 1.75(3)°. The ³¹P NMR spectrum contains a single peak at −62.8 ppm, and the ¹H NMR spectrum exhibits two singlets of equal height at 4.60 and 4.33 ppm. The UV-Vis spectrum contains three absorbance features at 615, 363, and 231 nm, with the absorbance at 615 nm due to the δ → δ* transition. The one electron oxidation of Mo₂Cl₄(PTA)₄ is reported at E_1/2 = 0.91 V relative to Ag/Ag⁺ in CH₂Cl₂. Also discussed is the reactivity of the molybdenum complex with CN⁻, H₂O, and HCl.     

Syntheses, structures, and magnetic properties of three Fe(II) complexes with reduced radical ligands

Three new Fe(II) complexes [Fe(HIM2py)₂(SCN)₂] (1), [Fe(HIM2py)₂(H₂O)₂](ClO₄)₂ · 2H₂O (2), and [Fe(HIM2py)₂(4,4-bipy)](ClO₄)₂ · 3CH₃CH₂OH (3) (4,4-bipy = 4,4′-bipyridine, HIM2py = 1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole) have been synthesized and characterized structurally as well as magnetically. The X-ray analysis reveals that HIM2py ligands are coordinated to the metal ions as an unusual six-membered didentate chelate with the κ²N(py), O(HIM) mode. Fe(II) ions in complex 3 are bridged by 4,4-bipy, leading to a 1D chain structure. The magnetic behavior of complex 3 is investigated, showing weak antiferromagnetic interactions.     

Synthesis, crystal structures and luminescent properties of zinc and manganese complexes from Demko-Sharpless reaction

The synthesis and crystal structure of two new complexes (Zn and Mn) containing tetrazolyl ligands are described. In situ [2+3] cycloaddition reactions of fipronil, (fipronil = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-carbonitrile) with sodium azide in the presence of ZnCl₂ or MnCl₂ as a Lewis acid (Demko-Sharpless tetrazole synthesis method) under hydrothermal (solvothermal) reaction conditions gave [Zn(L)₂](H₂O)₂] · H₂O, 1 and [Mn(L)₂](H₂O)₂] · H₂O, 2, (HL = (±)-5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazole-3-tetrazole). The central metals in both complexes are six coordinated, which connected by two water molecules, two nitrogen atoms from different tetrazolyl groups and two nitrogen atoms from pyrazolyl rings respectively. Photoluminescence studies reveal that both title complexes exhibit strong blue fluorescent emissions at λ_max = 383 nm for 1 and 411 nm for 2 respectively in the solid state at room temperature.     

Synthesis, anticancer activities, interaction with DNA and mitochondria of manganese complexes

Two new complexes [(Etdpa)MnCl₂] and [(Adpa)Mn(Cl)(H₂O)] (Etdpa = ethyl bis(2-pyridylmethyl)amino-2-propionate; Adpa = bis(2-pyridylmethyl)amino-2-propionic acid) were synthesized and characterized by spectral methods. The crystal structure of [(Etdpa)MnCl₂] shows that the Mn(II) atom is coordinated by three N atoms (N1, N2, N3), one oxygen atom (O1) of the ligand (Etdpa) and two chloride atoms (Cl1, Cl2), forming a distorted octahedral geometry. The binding interaction between ct-DNA and the synthesized complexes was relatively weak, but they can inhibit the induced swelling of Ca²⁺-loaded mitochondria in a dose-dependent manner. The [(Adpa)Mn(Cl)(H₂O)] can cause the obvious decrease of mitochondria membrane potential. The MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenpyltetra-zolium bromide) assay shows that the two Mn(II) complexes are more active against cancer cells. Especially [(Adpa)Mn(Cl)(H₂O)] can inhibit the proliferation of glioma cells with IC₅₀ 9.5 μM. Experimental results indicate that the [(Adpa)Mn(Cl)(H₂O)] could be a new potential antitumor complex to target the mitochondria.     

Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn₂(Hphth)₂(phen)₄] · 2Hphth · 6H₂O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)₂(H₂O)] · 2.5H₂O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H₂O)₂]_n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H₂O)₂]_n · 2nH₂O (4) (H₂phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn-syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]_n · nH₂O (5) with dehydration in warm solution.     

Hydrazone Schiff base-manganese(II) complexes: Synthesis, crystal structure and catalytic reactivity

Five dissymmetric tridentate Schiff base ligands, containing a mixed donor set of ONN and ONO were prepared by the reaction of benzhydrazide with the appropriate salicylaldehyde and pyridine-2-carbaldehyde and characterized by FT-IR, ¹H and ¹³C NMR. The complexes of these ligands were synthesized by treating an ethanolic solution of the appropriate ligand and one equivalent Et₃N with an equimolar amount of MnCl₂ · 4H₂O or alternatively by a more direct route in which an ethanolic solution of benzhydrazide was added to ethanolic solution of appropriate salicylaldehyde and MnCl₂ · 4H₂O solution to yield [MnCl(L¹)(H₂O)₂], [Mn(L²)₂(H₂O)₂], [MnCl(L³)], [MnCl(L⁴)] and [MnCl₂(H₂O)(L⁵)]. The hydrazone Schiff base ligands and their manganese complexes including HL^1-4 and L⁵ (HL¹ = benzoic acid (2-hydroxy-3-methoxy-benzylidene)-hydrazide, HL² = benzoic acid (2,3-dihydroxy-benzylidene)-hydrazide, HL³ = benzoic acid (2-hydroxy-benzylidene)-hydrazide, HL⁴ = benzoic acid (5-bromo-2-hydroxy-benzylidene)-hydrazide, L⁵ = benzoic acid pyridine-2-yl methylene-hydrazide) were characterized on the basis of their FT-IR, ¹H and ¹³C NMR, and molar conductivity. The crystal structures of HL¹ and [MnCl₂(H₂O)L⁵] have been determined. The results suggest that the Schiff bases HL¹, HL², HL³, and HL⁴ coordinate as univalent anions with their tridentate O,N,O donors derived from the carbonyl and phenolic oxygen and azomethine nitrogen. L⁵ is a neutral tridentate Schiff base with N,N,O donors. ESI-MS for the complexes Mn-L^2,3,5 provided evidence for the presence of multinuclear complexes in solution. Catalytic ability of Mn-L^1-5 complexes were examined and found that highly selective epoxidation (>95%) of cyclohexene was performed by iodosylbenzene in the presence of these complexes and imidazole in acetonitrile.     

Synthesis, X-ray crystal structure, DFT- and TDDFT-based spectroscopic property investigations on a mixed-ligand chromium(III) complex, bis[2-(2-hydroxyphenyl)benzimidazolato]-(1,10-phenanthroline)chromium(III) isophthalate

A mixed-ligand Cr(III) complex with 2-(2-hydroxyphenyl)benzimidazole, 1,10-phenanthroline and isophthalic acid, [Cr(pbm)₂(phen)]X_0.5 (1X_0.5) (Hpbm = 2-(2-hydroxyphenyl)benzimidazole; phen = 1,10-phenanthroline; H₂X = isophthalic acid) has been prepared by heating in aqueous solution and characterized, and the geometric structure and spectroscopic properties, investigated experimentally and theoretically by using the density functional theory level (DFT) and the time-dependent density functional theory level (TDDFT). The theoretical-experimental agreement is satisfactory. Further theoretical analyses of electronic structure and molecular orbitals have demonstrated that the low-lying absorption bands in UV-Vis spectrum are mainly π → π∗ ligand-to-ligand charge transfer transition (LLCT) and or π → (d_z²-d_x²-y²-d_yz) ligand-to-metal charge transfer transition (LMCT) in nature.     

Reversible ring opening and closure reactions of the triazine ligands derived from 1-phenylazo-2-naphthylamine and pyridine-2-aldehyde or quinoline-2-aldehyde - structure and reactivity of the palladium (II) complexes

New ligands containing a heterocyclic ring, L¹ (1-anilino-2-(2-pyridyl)-naphth[1,2-d]imidazol-1-io-3-ide), L² (2-phenyl-3-(2-pyridyl)-3,4-dihydro-naphtho[2,1-e][1,2,4]triazin-1-io-4-ide), and L³ (1-anilino-2-(2-quinolyl)-naphth[1,2-d]imidazol-1-io-3-ide), and their palladium (II) complexes have been prepared. Structures of the ligands and the complexes were determined by X-ray crystallography. The mononuclear square-planar complexes of [PdCl₂(Lⁿ)] (n = 1 (1), n = 2 (2) and n = 3 (3)) had didentate Lⁿ (n = 1-3) ligands. The Lⁿ (n = 1-3) ligands were stable and their absorption spectra did not change in dichloromethane and methanol. On the other hand, the absorption spectrum of [PdCl₂(L²)] (2) in dichloromethane changed rapidly when methanol was added to the solution, and [PdCl(L^4b)] (5) (L^4b = N-[methoxy(2-pyridyl)methyl]-1-(phenylazo)-2-naphthylamide) was obtained from the concentrated reaction mixture. In this reaction, the dihydrotriazine ring of the didentate L² ligand in complex 2 opened and the resulting tridentate L^4b ligand coordinated to the Pd atom in complex 5. When an excess amount of (ⁿBu)₄NCl was added to complex 5 in dichloromethane, the absorption spectrum reverted to that of complex 2. Thus, the reversible ring opening and closure reactions of the coordinating dihydrotriazine ligand were observed. We also prepared [PdCl₂(L⁵)] (9) (L⁵ = 1-(phenylazo)-N-[1-(2-pyridyl)ethylidene]-2-naphthylamine) and determined the structure. It is noted that neither the ring closure reaction nor the coordination of the azo nitrogen atom of the L⁵ ligand occurred in complex 9.     

A dimanganese(II) complex with bridging chlorides: Synthesis, electrochemistry, magnetic behavior, structure and bonding

The synthesis of dimeric [Mn₂Cl₂(μ-Cl)₂(dipa)₂]·MeOH (3) (dipa = dipyridylmethylamine) from [MnCl₂(H₂O)₄] (1) and dipa (2) and its structural characterization is reported. In the solid state complex 3 is dimeric and possesses crystallographically imposed C₂ symmetry, which differs from similar dimanganese(II) complexes showing an inversion symmetry for the central Mn(μ-Cl)₂Mn arrangement. Each manganese atom is thereby bound by three nitrogen atoms from a facially coordinated dipa ligand, and three chlorides (1 terminal and 2 μ-bridging) in an octahedrally distorted fashion.The cylovoltammogram of 3 displays that the two manganese(II) ions can independently be oxidized. The magnetic properties of 3 were determined by susceptibility measurements versus temperature. The intramolecular J parameter was determined to a value of J = (−5.2 ± 0.5) cm⁻¹.     

Supramolecular cobalt(II)-pyridine-2,5-dicarboxylate complexes with isonicotinamide, 2-amino-3-methylpyridine and 2-amino-6-methylpyridine: Syntheses, crystal structures, spectroscopic, thermal and antimicrobial activity studies

The mer-[Co(pydca)(H₂O)₃(ina)]·H₂O (1), (2a3mpyH)₂[Co(pydca)₂(H₂O)₂]·2H₂O (2) and (2a6mpyH)₂[Co(pydca)₂(H₂O)₂]·2H₂O (3) complexes (H₂pydca: pyridine-2,5-dicarboxylic acid, ina: isonicotinamide, 2a3mpy = 2-amino-3-methylpyridine and 2a6mpy = 2-amino-6-methylpyridine) were synthesised and characterised by elemental analysis, magnetic and spectroscopic measurements (UV-Vis and IR spectra) and single crystal X-ray diffraction technique. The thermal behaviour of the complexes was also studied by simultaneous thermal analysis techniques (TG, DTG and DTA). In complex 1, Co(II) ion was coordinated by one bidentate pydca, one isonicotinamide and three aqua ligands to generate a CoN₂O₄ distorted octahedral geometry. Complexes 2 and 3 crystallise in the triclinic system and space group and the structures consist of one complex anion [Co(pydca)₂(H₂O)₂]²⁻, two protonated aminomethylpyridinium cations, ampyH⁺ and two crystal water molecules. In the anions, the Co(II) ions have a distorted octahedral configuration and are coordinated by two bidentate pydca and two trans-aqua ligands. The pydca ligand is coordinated to the Co(II) by both the heterocyclic N atom and the adjacent carboxylate group O atom, creating a chelate ring, while protonated ampy ions behave as counter ion.     

Synthesis and spectral investigation of manganese(II), cadmium(II) and oxovanadium(IV) complexes with 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone): Crystal structure of manganese(II) and cadmium(II) complexes

The chelating behavior of 2,6-diacetylpyridine bis(2-aminobenzoylhydrazone) (H₂dapa) towards manganese(II), cadmium(II) and oxovanadium(IV) ions has been studied by elemental analyses, conductance measurements, magnetic properties and spectral (IR, ¹H NMR, UV-Vis and EPR) studies. The IR spectral studies suggest the pentadentate nature of the ligand with pyridine nitrogen, two azomethine nitrogens and two carbonyl oxygen atoms as the ligating sites. Six coordinate structure for [VO(H₂dapa)]SO₄ · H₂O and seven coordinate structures for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)Cl₂] · H₂O complexes have been proposed. Pentagonal bipyramidal geometry for [Mn(H₂dapa)(Cl)(H₂O)]Cl · 2H₂O and [Cd(H₂dapa)(Cl₂)] · H₂O complexes was confirmed by single crystal analysis. The X-band EPR spectra of the oxovanadium(IV) and manganese(II) complexes in the polycrystalline state at room (300 K) and also at liquid nitrogen temperature (77 K) were recorded and their salient features are reported.     

Structural variability in manganese(II) complexes of N,N′-bis(2-pyridinylmethylene) ethane (and propane) diamine ligands

Manganese(II) complexes, Mn₂L¹₃(ClO₄)₄, MnL¹(H₂O)₂(ClO₄)₂, MnL²(H₂O)₂(ClO₄)₂, and {(μ-Cl)MnL²(PF₆)}₂ based on N,N′-bis(2-pyridinylmethylene) ethanediamine (L¹) and N,N′-bis(2-pyridinylmethylene) propanediamine (L²) ligands have been prepared and characterized. The single crystal X-ray diffraction analysis of Mn₂L²₃(ClO₄)₄ shows that each of the two Mn(II) ion centers with a Mn-Mn distance of 7.15 Å are coordinated by one ligand while a common third ligand bridges the metal centers. Solid-state magnetic susceptibility measurements as well as DFT calculations confirm that each of the manganese centers is high-spin S = 5/2. The electronic structure obtained shows no orbital overlap between the Mn(II) centers indicating that the observed weak antiferromagentism is a result of through space interactions between the two Mn(II) centers. Under different reaction conditions, L¹ and Mn(II) yielded a one-dimensional polymer, MnL¹(H₂O)₂(ClO₄)₂. Ligand L² when reacted with manganese(II) perchlorate gives contrarily to L¹ mononuclear MnL²(H₂O)₂(ClO₄)₂ complex. The analysis of the structural properties of the MnL²(H₂O)₂(ClO₄)₂ lead to the design of dinuclear complex {(μ-Cl)MnL²(PF₆)} where two chlorine atoms were utilized as bridging moieties. This complex has a rhomboidal Mn₂Cl₂ core with a Mn-Mn distance of 3.726 Å. At room temperature {(μ-Cl)MnL²(PF₆)} is ferromagnetic with observed μ_eff = 4.04 μ_B per Mn(II) ion. With cooling, μ_eff grows reaching 4.81 μ_B per Mn(II) ion at 8 K, and then undergoes ferromagnetic-to-antiferromagnetic phase transition.     

Iron(III) induced 2-phenyl imidazolidine ring hydrolysis of a new binucleating Schiff base ligand: X-ray structure of the mononuclear Fe(NNO)2 end product

The reaction of triethylenetetramine, salicylaldehyde and benzaldehyde in 1:2:1 mole ratio in methanol at room temperature affords a novel μ-bis(tridentate) ligand H₂L′ through the formation of an imidazolidine ring within the parent hexadentate precursor in a two step reaction. The ligand H₂L′ reacts with Fe(ClO₄)₂ · 6H₂O in aqueous methanol in the presence of triethylamine to form the mononuclear [Fe^IIIL](ClO₄) complex, (where L²⁻ is the anion of the parent hexadentate H₂saltrien ligand) after the cleavage of the imidazolidine ring. The mononuclear complex has a structure with an N₄O₂ donor atom set of the hexadentate ligand forming a distorted octahedral coordination geometry around the metal atom as established from a crystal structure determination. The Fe-N(imine) distances are 1.934(10) and 1.948(9) Å, Fe-N(amine) distances are 2.062(8) and 2.076(9) Å and Fe-O(phenol) distances are 1.864(8) and 1.872(7) Å. The terminal oxygen donor atoms occupy cis positions and the remaining four nitrogen atoms (two cis amine and two trans imine) complete the coordination sphere. The mononuclear complex has a magnetic moment 1.89 μ_B corresponding to the low-spin 3d⁵ configuration. The UV-Vis spectrum of the end product, after the imidazolidine ring hydrolysis, is different from the spectrum of the initial reaction mixture containing the μ-bis(tridentate) ligand H₂L′.     

Syntheses, structures and magnetic properties of two copper(II) tricyanomethanide complexes with 2,2′-bipyrimidine as bridging ligands

Two copper(II) tricyanomethanide (tcm) complexes with 2,2′-bipyrimidine (bpym) as co-ligands Cu₄(bpym)₅(tcm)₈ · 2H₂O (1) and [Cu₂(bpym)₂(tcm)₄ · H₂O]_n (2) have been synthesized, and structurally and magnetically characterized. Compound 1 displays a tetranuclear structure, in which each middle copper(II) atom is coordinated by two bridging bpym molecules and two terminal tcm ligands to form a tetragonal bipyramidal geometry, while each side copper(II) atom is surrounded by one bridging bpym, one terminal bpym, one terminal bonded tcm and one terminal weakly coordinated tcm ligands to give a square bipyramidal geometry. In 1 the four neighbouring copper(II) atoms are joined to each other by the bpym molecules, which leads to the formation of a tetranuclear structure. Compound 2 features an infinite chain structure, in which two slightly different chains exist. In each chain the copper(II) atom is bonded to two bridging bpym molecules and two terminal tcm ligands to form a tetragonal bipyramidal geometry, the adjacent copper(II) atoms are linked each other by the bpym ligands to define an infinite chain structure. In 2 the distances between two neighbouring copper(II) atoms in one chain are different. Moreover these distances in one chain are also different from those of the other chain. Magnetic susceptibility measurements for the two complexes in the temperature range 2-300 K reveal the occurrence of significant antiferromagnetic interactions for 1 (J₁ = −20.42 cm⁻¹, J₂ = −5.29 cm⁻¹ and g = 2.22) and 2 (T > 50 K, θ = −20.00 K, C = 0.86 cm³ mol⁻¹ K), respectively.     

Synthesis, crystal structure and photoelectric property of Mn(II/IV) coordination complexes

Three novel coordination complexes [Mn(tpha)(phen)]_n (1); [Mn(na)₂(H₂O)₂]_n (2); {[Mn(phen)₂(OH)Cl] · Cl · (OH) · (C₉H₁₁NO₂) · 2H₂O} (3) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction (H₂tpha = terephthalic acid, Hna = nicotinic acid, phen = 1,10-phenanthroline). The tpha groups in complex 1 bridge the Mn(II) ions to an infinite 3D framework. Complex 2 exhibits a 2D network structure in which the Mn(II) ions are linked by nicotinic groups. Complex 3 is connected to a 2D coordination supramolecule by hydrogen bonds. The results of surface photovoltage spectra (SPS) of complexes 1-3 indicate that they all exhibit positive surface photovoltage (SPV) responses in the range of 300-800 nm. However, the intensity, position and numbers of SPV responses are obviously different. The distinctions can be mainly attributed to their structures, valences and coordination environments of the manganese ions in the three complexes. Moreover the external field induced surface photovoltage spectra (FISPS) of the three complexes have been measured.     

Synthesis, crystal structure and electroluminescent properties of a Schiff base zinc complex

A new complex of zinc with a Schiff base, zinc(N,N′-bis(salicylidene)-3, 6-dioxa-1, 8-diaminooctane monohydrate) (ZnBSO · H₂O), was synthesized and characterized by means of elemental analyses, IR spectra and DTA-TG. Its structure was determined by X-ray single crystal analysis. It was demonstrated that the zinc atom is coordinated by the two oxygen atoms in phenolate and two nitrogen atoms in imine of the ligand in a slightly distorted tetrahedral geometry, while the two oxygen atoms from the oxa-alkyl chain are not coordinated to Zn(II) atom. The energy levels of the HOMO, LUMO and the electrochemical band gap were determined by cyclic voltammeter. The electroluminescent devices with the complex as the emitter showed bright blue emission with a peak at 450 nm, which is same as the fluorescence of the complex in both solution and solid states.     

Two three-dimensional cyano-bridged bimetallic cadmium(II) and copper(II)-copper(I) mixed-valence polymer compounds: Crystal structures and thermal stability analysis and magnetic properties

Two cyano-bridged cadmium(II) and copper(II)-copper(I) mixed-valence polymer compounds 1 and [Cu^II(en)₂]_0.5[CdCu^I(CN)₃] · Cl · H₂O 2 (en = 1,2-ethanediamine) through systematically varying the solution environment have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. The cyano anions connected the copper and cadmium centres with bidentate or tridentate bridging modes resulting in two complicated 3D networks for 1 and 2. Compound 1 has a rare 5,6-connected network, while compound 2 can be reduced to a 6-connected α-Po net. The magnetic and thermal properties of 1 and 2 are also studied.     

Encapsulation of [Mn(bpy)3] cations in 2D [Mn(dca)3] sheet: Synthesis, X-ray structure and EPR study

The reaction of Mn(NO₃)₂ · 4H₂O, 2,2′-bipyridine (bpy) and sodium dicyanamide (dca) in aqueous medium yielded the {[Mn(bpy)₃][Mn(dca)₃]₂}_n (1). The single-crystal X-ray analysis of 1 revealed that the anionic part of the complex, [Mn(dca)₃]⁻, features infinite 2D sheets with a honeycomb-like porous structure having a void space of ca. 12 Å in which [Mn(bpy)₃]²⁺ cations are encapsulated to yield a fascinating molecular assembly. Mn^II ions possess an octahedral geometry both in the anionic and cationic components of complex 1. In the anionic component, each Mn^II ion is bridged by three pairs of dicyanamide anions in an end-to-end fashion with two other Mn^II ions from adjacent [Mn(dca)₃]⁻ moieties. This type of linking propagates parallel to the bc crystallographic plane to form 2D sheets. [Mn(bpy)₃]²⁺ is found to have somewhat “squeezed” upon encapsulation. No measurable magnetic interaction was evidenced through variable temperature magnetic susceptibility measurements. However, in addition to the broad g ≈ 2 resonance typical of magnetically diluted [Mn(bpy)₃]²⁺ cations, EPR spectroscopy evidenced exchange narrowing of the [Mn(dca)₃]⁻ resonance at g ≈ 2 thus indicating operation of weak magnetic interactions extended over the whole 2D network through the dca⁻ bridges.     

Synthesis and characterization of a series of N3O-ligated mononuclear Mn(II) halide complexes

Treatment of a N₃O-donor chelate ligand (mpppa = N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine; bpppa = N-benzyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine) with equimolar amounts of Mn(ClO₄)₂ · 6H₂O and Me₄NX (X = Cl, Br, I) in methanol resulted in the production of a series of mononuclear Mn(II) halide complexes of the formula [(L)Mn-X(CH₃OH)]ClO₄ (L = mpppa or bpppa). X-ray crystallographic studies of [(mpppa)Mn-Cl(CH₃OH)]ClO₄ · CH₃OH (2 · CH₃OH), [(mpppa)Mn-Br(CH₃OH)]ClO₄ · CH₃OH (4 · CH₃OH), [(mpppa)Mn-I(CH₃OH)]ClO₄ · CH₃OH (6 · CH₃OH), and [(bpppa)Mn-I(CH₃OH)]ClO₄ · O₂(CH₂CH₃)₂ (7 · O(CH₂CH₃)₂) revealed for each a mononuclear Mn(II) center having tetradentate coordination of the chelate ligand, one coordinated halide anion, and one molecule of coordinated methanol. An increase in the Mn-X distance through the halide series (Cl, Br, I) correlates linearly with the increase in the radius of the anion. The magnetic moment of each halide complex, measured via Evans method in methanol, is consistent with the presence of a high-spin distorted octahedral Mn(II) center. The EPR features of the halide complexes in methanol do not change as a function of the nature of the halide coordinated to the Mn(II) center.