Cyanide-bridged complexes based on dinuclear Cu(II)-M(II) [M = Pb and Cu] building blocks: Synthesis, crystal structures and magnetic properties

Four cyanide-bridged heterometallic complexes {[CuPb(L 1 )][Fe III (bpb)(CN) 2 ]} 2 ·(ClO 4 ) 2 ·2H 2 O·2CH 3 CN (1), {[CuPb(L 1 )] 2 [Fe II (CN) 6 ](H 2 O) 2 }·10H 2 O (2), {[Cu 2 (L 2 )][Fe III (bpb)(CN) 2 ] 2 }·2H 2 O·2CH 3 OH (3) and {[Cu 2 (L 2 )] 3 [Fe III (CN) 6 ] 2 (H 2 O) 2 }·10H 2 O (4) have been synthesized by treating K[Fe III (bpb)(CN) 2 ] [bpb 2-=1,2-bis(pyridine-2-carboxamido)benzenate] and K 3 [Fe III (CN)] 6 with dinuclear compartmental macrocyclic Schiff-base complexes [CuPb(L 1 )] (ClO 4 ) 2 or [Cu 2 (L 2 )]·(ClO 4 ) 2 , in which H 2 L 1 was derived from 2,6-diformyl-4-methyl-phenol, ethylenediamine, and diethylenetriamine in the molar ratio of 2:1:1 and H 2 L 2 from 2,6-diformyl-4-methyl-phenol and propylenediamine in the molar ratio of 1:1. Single crystal X-ray diffraction analysis reveals that compound 1 displays a cyclic hexanuclear heterotrimetallic molecular structure with alternating [FeⅢ (bpb)(CN) 2 ]- and [CuPb(L 1 )] 2+ units. Complex 2 is of a neutral dumb-bell-type pentanuclear molecular configuration consisting of one [Fe(CN)6] 4- anion sandwiched in two [CuPu(L 1 )] 2+ cations, and the pentanuclear moieties are further connected by the hydrogen bonding to give a 2D supramolecular framework. Heterobimetallic complex 3 is a tetranuclear molecule composed of a centrosymmetric [Cu 2 (L2)] 2+ segment and two terminal cyanide-containing blocks [FeⅢ (bpb)(CN)2 ]- . Octanuclear compound 4 is built from two [Fe(CN)6]3- anions sandwiched in the three [Cu 2 L 2 ] 2+ cations. Investigation of their magnetic properties reveals the overall antiferromagnetic behavior in the series of complexes except 2.     

Zero-, one- and two-dimensional bis-triazole-bis-amide-based copper(II) complexes tuned by polycarboxylates with different protonation degrees: assembly, structures and properties

Three bis-triazole-bis-amide-based copper(II) complexes with different dimensionality, [Cu(dtcd)₂ (1,3-HBDC)₂]·2H₂O (1), [Cu(dtcd) (1,3,5-H₂BTC)₂]·2H₂O (2) and [Cu₄(μ ₃-OH)₂(dtcd)₂(SIP)₂]·4H₂O (3) (dtcd = N,N′-di(4H-1,2,4-triazole) cyclohexane-1,4-dicarboxamide, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid, 1,3,5-H₃BTC = 1,3,5-benzenetricarboxylic acid, NaH₂SIP = sodium 5-sulfoisophthalate), have been synthesized under different pH values and structurally characterized. Complex 1 exhibits a zero-dimensional mononuclear structure with one carboxyl group of 1,3-HBDC coordinating to copper(II), while the other carboxyl group is protonated. In complex 2, the Cu^II ions are bridged by the dtcd ligands forming a one-dimensional chain, in which only one carboxyl group of 1,3,5-H₂BTC coordinates with the metal, while the others are protonated. Complex 3 possesses a two-dimensional network based on tetranuclear Cu₄ clusters supported by the dtcd and nonprotonated SIP ligands. The various structures clearly indicate that the pH and polycarboxylates have a great influence on the dimensionality and structures of 1–3. The luminescence properties of 1–3 and magnetic properties of 3 were investigated.     

Synthesis,characterization, and thermal behavior of palladium(II) complexes containing 4-iodopyrazole

The mononuclear pyrazolyl complexes [PdCl₂(HIPz)₂] (1), [PdBr₂(HIPz)₂] (2), [PdI₂(HIPz)₂] (3), [Pd(SCN)₂(HIPz)₂] (4), and [Pd(NHCOIPz)₂] (5) have been prepared. Compound 1 was obtained from the displacement of acetonitrile from [PdCl₂(CH₃CN)₂] precursor by the 4-iodopyrazole (HIPz) ligand, whereas 2–5 were synthesized by substitution of the chlorido in 1 by the respective anionic group. The compounds were characterized by elemental analysis, infrared spectroscopy, and ¹H NMR spectroscopy. The thermal behavior of 1–5 has been studied by TG and DTA. The thermal stability of [PdX₂(HIPz)₂] compounds varies according to the trends X = Cl^? < I^? ? SCN^?< Br^?. No stable intermediates were isolated during the thermal decompositions due to the overlap of the degradation processes. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Keggin-Type Polyoxometalate Cluster Functionalized with Dinuclear M-H2biim (M = Cu, Ag) Metal–Organic Segments

Three inorganic–organic hybrid complexes, [Cu₂(H₂biim)₂(OH)₂]₂(SiW₁₂O₄₀)·2H₂O (1), [Cu₂(H₂biim)₂]₂(SiW₁₂O₄₀)·2H₂O (2) and [Ag₂(H₂biim)₂]₂(SiW₁₂O₄₀)·2H₂O (3) (H₂biim = 2, 2′-biimidazole), have been synthesized under hydrothermal conditions, and characterized by elemental analysis, IR, PXRD, TG and single-crystal X-ray diffraction. The crystallographic analysis reveals that in compounds 1–3, the Keggin polyanions [α-SiW₁₂O₄₀]^4? act as inorganic building blocks, which are linked with the dinuclear metal–organic units via Cu–O bonds in compound 1, or through supramolecular interactions in compounds 2 and 3. Compound 1 shows a 3D supramolecular structure constructed by net-like layers. Compounds 2 and 3 display 2D layer structures which were composed of wave-like chains. In addition, these compounds show electrochemical activities, and photoluminescence properties are measured in the solid state.     

Syntheses,crystal structures,and magnetic properties of a series of double end-on azido-bridged dinuclear manganese(II) complexes

Four azido-bridged dinuclear Mn(II) complexes, [Mn₂(phen)₄ μ-₁,₁-N₃)₂][Fe^III(bpmb)(CN)₂]₂·H₂O (1), [Mn₂(phen)₄(μ-₁,₁-N₃)₂][Fe^III(bpClb)(CN)₂]₂·H₂O (2), and [Mn₂(phen)₄(μ-₁,₁-N₃)₂][M^III(bpdmb)(CN)₂]₂·3H₂O [M = Fe (3) or Cr (4); phen = 1,10-phenanthroline, bpmb^2– = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate, bpClb^2– = 1,2-bis(pyridine-2-carboxamido) 4-chloro-benzenate, bpdmb^2– = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate], have been synthesized using the synthetic strategy of large anion inducement. Single-crystal X-ray diffraction analysis reveals that all four complexes are doubly end-on (EO) azido-bridged binuclear Mn(II) complexes with two large [M(L)(CN)₂]^– (L = bpmb^2?, bpClb^2?, or bpdmb^2?) building blocks acting as charge-compensating anions. The magnetic properties of the complexes have been investigated, and the results indicate that the magnetic coupling between two Mn(II) centers through the EO azide bridges is ferromagnetic, with J = 0.64(1) cm^?1 for 1, 0.43(1) cm^?1 for 2, 0.50(1) cm^?1 for 3, and 0.66(2) cm^?1 for 4. The magneto-structural relationships of EO azido-bridged Mn(II) systems are discussed.     

One-dimensional cyanide-bridged Cr(III)–Cu(II) complexes: synthesis,crystal structures and magnetic properties

Using two trans-dicyanidechromium(III) precursors K[Cr(bpdmb)(CN)₂] (bpdmb^2? = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate), K[Cr(bpClb)-(CN)₂] (bpClb^2? = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate) and one Cu(II) complex of a 14-membered macrocycle as ancillary organic ligand as assembling segments, two one-dimensional cyanide-bridged Cr^III–Cu^II complexes {{[Cu(cyclam)][Cr(bpdmb)(CN)₂]}ClO₄} _n ·nCH₃OH·nH₂O (1) and {{[Cu(cyclam)][Cr(bpClb)(CN)₂]}ClO₄} _n ·nCH₃OH (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis shows that their similar one-dimensional cationic single-chain structures consist of alternating units of [Cu(cyclam)]²⁺ and [Cr(bpdmb)(CN)₂]^?/[Cr(bpClb)(CN)₂]^? with free ClO₄ ^? as balancing anions. Investigations of the temperature dependences of magnetic susceptibility and the field-dependent magnetization reveal that both complexes have overall ferromagnetic coupling between the neighboring Cr(III) and Cu(II) centers through the bridging cyanide groups.     

Synthesis,structure, and magnetic properties of heterotrimetallic tetranuclear complexes

Two novel heterotrimetallic tetranuclear complexes [Cu(H₂L)(CH₃OH)]₂Gd(DMF)Fe(CN)₆·2H₂O·DMF (1) and [Cu(H₂L)(CH₃OH)]₂Tb(H₂O)_0.57(DMF)_0.43Fe(CN)₆·5.5H₂O (2) are reported (H₄L = N,N′-ethylenebis(3-hydroxysalicylidene)). The central Ln(III) ion is surrounded by two neutral [Cu(H₂L)(CH₃OH)] moieties, forming a Cu₂Ln trinuclear unit. The [Fe(CN)₆]^3? anion is weakly coordinated to one Cu(II) ion of [Cu(H₂L)(CH₃OH)] through a cyanide nitrogen atom with the N–Cu distance of ca. 3.2 Å. Magnetic susceptibility measurements indicate the presence of overall ferromagnetic interactions in complexes 1 and 2. The magnetic coupling constant in complex 1 is J _Cu1Gd1 = 4.54 cm^?1 and J _Cu2Gd1 = 7.97 cm^?1 based on \( \hat{H} = - 2J_{\text{Cu1Gd1}} \hat{S}_{\text{Cu1Gd1}} - 2J_{\text{Cu2Gd1}} \hat{S}_{\text{Cu2Gd1}} \) . Dynamic AC magnetic susceptibility studies reveal that complex 2 shows frequency-dependent out-of-phase signals, typical of single molecule magnet behavior. The energy barrier for complex 2 under a 2 kOe applied DC magnetic field is 13 K.     

A flexible chelate ligand in dodecatungstoborate-based supramolecular compounds

Two new dodecatungstoborate-based supramolecular compounds, [Cu₄(H₂EGTA)₂(H₂O)₄(HBW₁₂O₄₀)]·18H₂O (1) and [Na₃(H₂O)₆Ca₃(H₂O)₆(HEGTA)₂] [H₂BW₁₂O₄₀]·21H₂O (2) (EGTA = ethyleneglycol-bis-(2-aminoethylether)-tetra acetate anion), were synthesized in aqua solution and characterized by element analysis, infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction technique. The results show that in 1 two H₂EGTA^2? anions bond to four Cu²⁺ ions forming a four-nuclear cyclic cation, Cu₄(H₂EGTA)₂(H₂O) ₄ ⁴⁺ ; and dodecatungstoborate anion HBW₁₂O₄₀ ^4? acting as a bidentate ligand links two four-nuclear cations, leading to one-dimensional chain extending along [101] direction, [Cu₄(H₂EGTA)₂(H₂O)₄(HBW₁₂O₄₀)] _n (Cu–EGTA–BW₁₂). In 2 two HEGTA^3? anions coordinate to four Ca²⁺ ions in different modes, forming a Ca-EGTA polymeric chain. The building blocks (Cu–EGTA–BW₁₂ chains in 1, Ca–HEGTA chains and BW₁₂ anions in 2) are fused into three-dimensional architectures by hydrogen bonds. Variable temperature magnetic susceptibilities of 1 were determined and the results show that in 1 there is a weak ferromagnetic interaction.     

anti-syn and anti-anti coordination of the bridging CO 3 2− group in [Cu2(Phen)4(μ-CO3)]B10H10 binuclear complexes: Synthesis, structure, and magnetic properties

A redox reaction that occurs in the [Cu₂B₁₀H₁₀]/Phen system in CH₃CN/DMSO and CH₃CN/DMF in air yields a Cu(II) binuclear complex, [(Phen)₂Cu(CO₃)Cu(Phen)₂]²⁺. The [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 2.5DMSO · 2H₂O (I) and [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 4DMF (II) compounds have been isolated and studied by X-ray crystallography at 150 K and EPR at 295 K. Their magnetic properties have been studied in the range 300–2 K. In the cations of both compounds, the bridging CO ₃ ^2? group is bidentately coordinated to two Cu atoms. The cations in I and II have different spatial orientations of the Cu-O bonds: anti-syn and anti-anti, respectively. Compound I has weak magnetic interactions caused by a short Cu…Cu distance (4.441 Å) in the dimer. No exchange coupling is observed in II.     

Structure and catalytic activity of host–guest coordination polymers constructed from copper(I) cyanide nets and 1,4-diaminobutane or 1,5-diaminopentane in the presence of water

The reaction of K₃[Cu(CN)₄] and 1,4-diaminobutane (DAB) or 1,5-diaminopentane (DAP) in the presence of Me₃SnCl affords two monometallic host–guest Cu(I) cyanide polymers: {[H₂DAB][Cu₄(CN)₆]·2H₂O}, 1, and{[H₂DAP][H₃O][Cu₄(CN)₇]·2H₂O}, 2, with exclusion of Me₃Sn⁺ cation. The products were characterized by physicochemical and spectroscopic methods. The structure of 1 consists of two-dimensional hexagonal sheets of (CuCN) _n which stack along the b-axis creating honeycomb-shaped channels capable of encapsulating the protonated DAB and water molecules. The structure of 2 consists of a three-dimensional network of [Cu₄(CN)₇] with large cavities that include H₂DAP and water molecules. The rhombic minicycle [Cu₂(μ-CN)₂] fragments represent the basic building blocks of the network structure of 2. The structures of these compounds are stabilized by hydrogen bonding. The SCP 1 and SCP 2 exhibit good catalytic and photocatalytic activities for the degradation of methylene blue (MB) in the presence of H₂O₂. The efficiency of recycled SCP 1 and SCP 2 and the mechanism of degradation of MB dye were also investigated.     

Three types of heterometallic structural motifs based on [Mo(CN)8]3−/4− anion and MnII cation as building blocks

The reaction between K₃[Mo(CN)₈] · H₂O and MnCl₂ · 4H₂O in different reaction conditions have obtained three new bimetallic cyanide-bridged compounds, namely, {(tetrenH₂)_0.5[Mn(H₂O)₂][Mo^V(CN)₈] · 2H₂O} _n (1) (where, tetren is tetraethylenepentamine), {[Mn₂(H₂O)₄][Mo^IV(CN)₈] · 3H₂O} _n (2), and {[Mn₂(H₂O)₄][Mo^IV(CN)₈] · 4H₂O} _n (3). Compound 1 crystallizes in the orthorhombic system with space group Cmc21 and unit cell constants a = 7.8234(15), b = 26.013(5), c = 10.021(2) Å, β = 90°, and Z = 4. Compound 2 crystallizes in the monoclinic system with space group P21/n and unit cell constants a = 7.3329(11), b = 14.372(2), c = 18.070(3) Å, β = 90.869(2)°, and Z = 4. Compound 3 crystallizes in the tetragonal system with space group I4/m and unit cell constants a = b = 11.9371(8), c = 13.2930(18) Å, β = 90°, and Z = 4. X-ray single-crystal structures reveal that the Mo centers adopt a distorted square antiprism coordination environment for 1 and 3, while 2 closed to a bicapped trigonal prism. For these complexes, all the Mn^II centers in the extended structure adopt distorted octahedron geometry. For 1, each Mo^V coordinated via four cyanide groups to four Mn^II ions, and the other four cyanide groups are terminal, forming a two-dimensional framework. For 2, the Mo^IV center of structural unit coordinated via four cyanide groups to four Mn(1), and the other four cyanide groups coordinated to four Mn(2), forming a three-dimensional framework. For 3, each [Mo^IV(CN)₈]^4? building block is linked to Mn^II ions through its eight CN ligands, and each Mn^II center is connected to four Mo units forming a three-dimensional framework. In addition, magnetic studies of these complexes have also been presented.     

First MnIII complexes with tetradentate (N2O2) Schiff bases and tricyanomethanide: synthesis,crystal structure,and magnetic properties

The first Mn^III complexes with Schiff bases and tricyanomethanide-anion were synthesized: [Mn(salen)C(CN)₃(H₂O)] (1), [Mn(5-Brsalen)C(CN)₃(H₂O)] (2), [Mn(salpn)C(CN)₃(H₂O)] (3), [Mn(3-MeOsalen)C(CN)₃(H₂O)] (4), [Mn(5-Brsalen)(MeOH)(H₂O)][C(CN)₃] (5), and [Mn(3-MeOsalpn)(H₂O)₂][C(CN)₃] (6), where SalenH₂ is N,N′-bis(salicylidene)ethylenediamine, 5-BrsalenH₂ is N,N′-bis(5-bromosalicylidene)ethylenediamine, SalpnH₂ is N,N′-bis-(salicylidene)-1,3-diaminopropane, 3-MeOsalenH₂ is N,N′-bis(3-methoxysalicylidene)-ethylenediamine, 3-MeOsalpnH₂ — N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane. The tricyanomethanide anion in complexes 1–4 acts as a the terminal ligand, whereas in complexes 5 and 6 tricyanomethanide is not coordinated by Mn^III and acts as an out-of-sphere counterion. The structures of complexes 1–4 are characterized by the formation of dimers due to hydrogen bonds between the water molecules and oxygen atoms of the Schiff bases. The Mn...Mn distances inside the dimers are 4.69–5.41 Å. Complex 6 has a zigzag chain structure consisting of the [Mn(3-MeOsalpn)(H₂O)₂]⁺ cations bound by double bridging aqua ligands. The study of the magnetic properties of complexes 1, 3, 4, and 6 showed the existence of antiferromagnetic interactions between the Mn^III ions through the system of hydrogen bonds.     

Syntheses,structures, in vitro cytotoxicities and DNA-binding properties of four copper complexes based on a phenyl 2-pyridyl ketoxime ligand

Four complexes [Cu₆L₆(µ₄–O)₂(dca)₂] (1), [Cu₃L₃(µ₃–OH)Cl₂] (2), [Cu₃L₃(µ₃–OH)(OAc)₂]·py (3) and [Cu₂L₄] (4) (HL = phenyl 2-pyridyl ketoxime; dca = dicyanamide anion) have been synthesized and characterized by physicochemical and spectroscopic methods. The structures of all three complexes consist of a single or off-set stacked inverse 9-MC-3 metallacrown formed by three L^? ligands and three Cu atoms, and all of the Cu atoms are located in square planar or square pyramidal geometries with different apical ligands. In complex 4, four L^? ligands link two Cu atoms to form a dinuclear structure, and the Cu atoms adopt square pyramidal coordination geometry. The in vitro cytotoxicities against four cell lines (A549, HL-60, HT-29 and HCT-116) have been assayed by colorimetric MTT assay. In addition, all four complexes interact strongly with calf thymus DNA, which may be directly responsible for their antitumor activities.     

Syntheses and characterization of a new class of zirconia precursors of oxime-modified zirconium(IV) isopropoxide

Some oxime modified complexes of the type [Zr{OPrⁱ}_4?n{L}_n] {where, n = 1–4 and LH=(CH₃)₂C=NOH (1–4) and C₉H₁₆C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPrⁱ)₄·PrⁱOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (¹H and ¹³C{¹H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPrⁱ}₂{ONC(CH₃)₂}₂] (2), [Zr{OPrⁱ}₃{ONC₁₀H₁₆}] (5) and [Zr{OPrⁱ}{ONC₁₀H₁₆}₃] (7) and monomeric nature for [Zr{ONC₁₀H₁₆}₄] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO₂, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images.     

Synthesis,Characterization and Photophysical Studies of Luminescent Dinuclear and Trinuclear Copper(I) Alkynyl Phosphines

Luminescent polynuclear copper(I) alkynyl complexes, including two trinuclear bicapped complexes, [Cu₃(μ-dppm)₃(μ ₃-η ¹-C≡CC₆H ₄ ⁿ C₄H₉)₂]BF₄ (1) and [Cu₃(μ-dppm)₃(μ ₃-η ¹-C≡CC₆H₄C≡CC₆H₅)₂]BF₄ (2), as well as two dinuclear complexes, [Cu₂(PPh₂Me)₄(μ ₂-η ¹-C≡CC₆H ₄ ⁿ C₄H₉)₂] (3) and [Cu₂(PPh₂Me)₄(μ ₂-η ¹-C≡CC₆H₄C≡CC₆H₅)₂] (4), have been successfully synthesized and characterized. The carbazole moiety has also been incorporated into the alkynyl skeleton to prepare the trinuclear bicapped complex, [Cu₃(μ-dppm)₃(μ ₃-η ¹-C≡CC₆H₄-Cz)₂]BF₄ (Cz = carbazole) (5). The crystal structure of 3 has also been determined. The complexes exhibit high-energy intraligand (IL) π → π* absorption bands typical of the corresponding phosphine and alkynyl ligands. The complexes show intense luminescence originated from a ³LMCT [RC≡C^? → Cu _n ] state (n = 2, 3), with mixing of a triplet metal cluster-centered ds/dp state.     

Synthesis,crystal structures,luminescence and catalytic properties of three silver(I) coordination polymers with bis(imidazole) and benzenedicarboxylic acid ligands

Three new silver coordination compounds with empirical formula [Ag₂(L1)₂·(ntp)·(H₂O)_3.25]_n (1), [Ag_1.5(L1)_1.5·(H_0.5bdc)·(H₂O)₄]_n (2) and [Ag(L2)(Hmip)]_n (3) (L1 = 1,4-bis(imidazol-1-ylmethyl)benzene, L2 = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole, H₂ntp = 2-nitroterephthalic acid, H₂bdc = 1,3-benzenedicarboxylic acid, H₂mip = 5-methylisophthalic acid) were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and physico-chemical spectroscopic methods. The silver centers display different environments with a linear geometry in 1 and 2 and distorted T-shaped geometry in 3. In 1–3, the bidentate N-donor ligands (L1 and L2) bridge neighboring silver centers to form 1D infinite chain structures. Complexes 2 and 3 are extended into 2D layers, and 1 is packed into a 3D 3,4,4,6-connected supermolecular network via classical O–H···O hydrogen bonds, while 3 is further extended into 3D framework through π–π interactions. The luminescence properties of complexes 1, 2 and 3 were investigated in the solid state. These coordination polymers possess a remarkable activity for degradation of methyl orange by persulfate in a Fenton-like process.     

Synthesis and Characterization of the Face-Centered Cubic Clusters [(Me<Subscript>3</Subscript>tacn)<Subscript>8</Subscript>M<Subscript>8</Subscript>Pt<Subscript>6</Subscript>(CN)<Subscript>24</Subscript>]<Superscript>12+</Superscript> (M = Cr,Mo)

Incorporation of a 5d transition metal into the face-centered cubic metal-cyanide cluster geometry is accomplished for the first time with the isolation of a series of compounds featuring [(Me₃tacn)₈M₈Pt₆(CN)₂₄]¹²⁺ (M = Cr, Mo) clusters. Reaction of [(Me₃tacn)Cr(CN)₃] and K₂[PtCl₄] in a boiling aqueous solution generates [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄]Cl₁₂ · 27H₂O (1), wherein Pt^II centers reside at the face-centering sites and the cyanide ligands have reoriented to give Pt^II–C≡N–Cr^III linkages. The cyclic voltammogram obtained for a solution of 1 in DMSO exhibits a quasireversible reduction event centered at E _1/2 = ?1.59 V versus Cp₂Fe^0/1+. Reaction of 1 with K₂[Pt(CN)₄] in aqueous solution affords [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 6H₂O (2), in which each face of the cubic cluster is capped by a staggered tetracyanoplatinate anion with a Pt–Pt separation of 3.1552(7) Å. Attempts to perform analogous cluster-forming reactions with [(Me₃tacn)Mo(CN)₃] revealed a tendency toward cluster decomposition to give mixtures of insoluble products, including [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 46H₂O (3) and [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]_2.5[Pt(CN)₃Br]₂Br₃ · 6H₂O (4). Crystallographic analyses revealed these compounds to contain the anticipated [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄]¹²⁺ cluster in fully- and partially-capped forms, respectively. Unfortunately, the insolubility of these molybdenum-containing products precluded characterization of the cluster by cyclic voltammetry.     

Synthesis and structural studies of some copper-benzoate complexes

The reaction of CuCl₂·2H₂O with 3,5-diisopropylpyrazole (Pz^iPr2H) in the presence of sodium parafluorobenzoate (Na-p-FBz) resulted in the formation of an oxo-chloro-bridged tetranuclear complex [Cu₄(Pz^iPr2H)₄(μ-O)(μ-Cl)₆] 1, whereas the reaction of Cu(NO₃)₂·3H₂O with Pz^iPr2H in the presence of different benzoates gave [Cu(Pz^iPr2H)₂(μ-OCH₃)]₂(NO₃)₂ 2, [Cu(Pz^iPr2H)₃(NO₃)(p-ClBz)]·CH₃CN 3, [Cu(p-CH₃Bz)₂(Pz^iPr2H)]₂·2CH₃CN 4, [Cu(p-OCH₃Bz)₂(CH₃CN)]₂·4CH₃CN 5 and [Cu(p-CNBz)(CH₃CN)]₂ 6. Single-crystal X-ray diffraction studies confirmed these formulations. DNA binding studies for these complexes were performed by means of UV-visible absorption titration and viscosity measurements. Gel electrophoresis studies showed that hydroxyl radicals are involved in DNA cleavage in the presence of the complexes.     

Synthesis,Characterization and Crystal Structures of Two New Compounds of Polyoxometalates and Diaminocyclohexanetetraacetate–Copper Complexes

The two new compounds (NH₄)₂[Cu₅(H₂O)₁₀(DCTA)₂] [β-Mo₈O₂₆]·4H₂O (1) and Cu₂[Cu₃K₂(H₂O)₁₀(DCTA)₂(HBW₁₂O₄₀)]·14H₂O (2) (DCTA = 1,2-diaminocyclohexanetetraacetate anion) were synthesized in aqueous solutions and characterized by elemental analyses, TGA, IR spectroscopy and single-crystal X-ray diffraction technique. Single-crystal structure analyses indicate they are constructed by the complexes with different nuclearity and polyoxometalates. In 1 DCTA chelates Cu2 ion and bridges Cu1 and Cu3 ions, forming a tetra-nuclear-ring cation chain extending along [110] direction. In 2 DCTA chelates Cu2/Cu1 and combines Cu3 and K ions, leading to a cyclic ten-heteronuclear complex cation; the K2 ions combine the complex cations and BW₁₂O₄₀ ^5? anions, forming a complex cation-BW₁₂ layer extending on ab-plane. The variable-temperature magnetic susceptibilities of newly prepared crystalline sample of 1 were measured and 1 exhibits a weak antiferromagnetic interaction.     

Two new cyano-bridged Cu(II)-Fe(II) complexes: Synthesis and crystal structures

Two new cyano-bridged Cu(II)-Fe(II) binuclear complexes, [Cu(L¹)Fe(CN)₅(NO)] (I) [L¹ = 1,3,6,8,11,14-hexaazatricyclo[12.2.1.1^8,11]octadecane and [Cu(L²)Fe(CN)₅(NO)] · 2H₂O (II) L² = 1,3,6,9,11,14-hexaazatricyclo[12.2.1.1^6,9]octadecane, have been assembled and structurally characterized by spectroscopy and X-ray crystallography. Complex I crystallizes in the monoclinic crystalline system of space group P2₁/c, while complex II crystallizes in the monoclinic crystalline system of space group P2₁/n. These two complexes assume a binuclear structure in which the Fe²⁺ ion is in an octahedron environment and the Cu²⁺ ion is in a square-prism geometry environment.