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.     

Synthesis, crystal structures, and DNA-binding properties of zinc(II) and nickel(II) complexes with tris[2-(N-ethyl)benzimidazylmethyl]amine and cinnamate ligands

Tris[2-(N-ethyl)benzimidazylmethyl]amine (Etntb) and two of its complexes, [Zn(Etntb)(cinnamate)]NO₃·2DMF (1) and [Ni(Etntb)(cinnamate)·(H₂O)]NO₃ (2) have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the complexes have different structures. In complex 1, the coordination sphere around Zn(II) is distorted trigonal bipyramidal, whereas the coordination sphere around Ni(II) is distorted octahedral in complex 2. The DNA-binding properties of the free ligand and its complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and both complexes bind to DNA via an intercalative mode, and their binding affinity for DNA follows the order 1 > 2> ligand.     

Copper(II) and manganese(II) picrate complexes with the V-shaped ligand 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane: preparation,structure, DNA-binding properties and antioxidant activities

A V-shaped ligand, 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane (L), and its copper(II) and manganese(II) picrate complexes have been synthesized and characterized. The compositions of the complexes are [Cu(L)₂](pic)₂·2DMF (1) and [Mn(L)(pic)₂] (2), respectively. The crystal structure of complex 1 reveals a distorted tetrahedral geometry provided by four N donors from two ligands. Complex 2 is six coordinated, with a distorted octahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via the intercalation mode, and the order of the binding affinity is L > 1 > 2. Antioxidant tests in vitro show that the Cu(II) complex possesses significant antioxidant activity against superoxide and hydroxyl radicals, with better scavenging effects than mannitol and vitamin C.     

Cobalt(II) and silver(I) coordination polymers constructed from flexible bis(5,6-dimethylbenzimidazole) and substituted isophthalate co-ligands

Two coordination polymers, [Co(L1)(IPA] _n (1) and {[Ag(L2)(HMIPA)]·H₂O} _n (2) (H₂IPA = isophthalic acid, L1 = 1,2-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H₂MIPA = 5-methylisophthalic acid, L2 = 1,6-bis(5,6-dimethylbenzimidazol-1-yl)hexane, have been synthesized and characterized by physicochemical and spectroscopic methods, as well as single-crystal X-ray diffraction. In 1, six-coordinated cobalt centers are bridged by L1 and IPA^2? ligands to generate a (4,4) two-dimensional layer. However, complex 2 features a 1D chain structure, which is further extended by O–H···O hydrogen bonding interactions into a 2D supramolecular layer with (6³) topology. The fluorescence and thermal gravimetric analysis of both complexes were also explored. Furthermore, the complexes 1 and 2 exhibit remarkable catalytic properties for the degradation of methyl orange dyes in a Fenton-like process.     

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.     

Inclusion of Cl− or Br− anions within host framework formed by second-sphere interactions

In this study, we have deliberately utilized the second-sphere coordination approach into the construction of supramolecular inclusion solids Cl ? [H₂ L1]·[InCl₄] (Crystal I) and Br ? [H₂ L1]·[TeBr₆] (Crystal II). The chloride or bromine anions can be encapsulated inside the host assemblies formed by the diamine molecule (4,6-dimethyl-1,3-phenylene) bis(N,N-dibenzylmethane) (L1) and the metal complexes ([InCl₄]^? and [TeBr₆]^2?) via second-sphere interactions. The inclusion complexes have been structurally characterized by X-ray crystallography, indicating that weak C–H···Cl and C–H···Br hydrogen bonding synthons play a significant role in the construction of host framework. 2-D networks are formed in both complexes by the interconnection of 1-D networks through the multiple weak hydrogen bonding interactions with [InCl₄]^? or [TeBr₆]^2?. The guest Cl^? or Br^? anions are encapsulated inside the host cages through N–H···Cl hydrogen bonds. The inclusion selectively was studied for the two host assemblies.     

Host–guest complexes of various cucurbit[n]urils with the hydrochloride salt of 2,4-diaminoazobenzene

The interaction products of normal cucurbit[n]urils (n = 7, 8; Q[7] Q[8]) and a sym- tetramethyl-substituted cucurbit[6]uril derivative (TMeQ[6]) with the hydrochloride salts of 2,4-diaminoazobenzene (g·HCl) were investigated in aqueous solution using ¹H NMR spectroscopy, electronic absorption spectroscopy, as well as single crystal X-ray diffraction. The ¹H NMR spectra analysis established a basic interaction model in which inclusion complexes with a host:guest ratio of 1:1 form for the TMeQ[6] and Q[7] cases, while they form with a host:guest ratio of 1:2 for the Q[8] case. Commonly, the hosts selectively bound to the phenyl moieties of the guests. Absorption spectrophotometric analysis in aqueous solution defined the stability of the host–guest inclusion complexes at pH 3.2. Quantitatively, at this pH, complexes with a host:guest ratio of 1:1—those with smaller hosts TMeQ[6] and Q[7]—formed with logK values between 6 and 7. That with host Q[8] and a host:guest ratio of 1:2 formed with a logK value of 10.8. Single crystal X-ray structures of the inclusion complexes TMeQ[6]–g·HCl and Q[8]–g·HCl showed the phenyl moiety of the guest inserted into the host cavity. This result supports the solution-based ¹H NMR spectroscopic study.     

Synthesis,spectroscopic characterization,X-ray crystal structure,biological screening and catalytic studies of organotin(IV) carboxylates of 3-(4-cyanophenyl) acrylic acid

A series of six organotin(IV) carboxylates [Me₂SnL₂] (1), [n-Bu₂SnL₂] (2), [n-Oct₂SnL₂] (3), [Me₃SnL] (4), n-Bu₃SnL (5) and [Ph₃SnL] (6), where L = 3-(4-cyanophenyl) acrylic acid have been synthesized and characterized by elemental analysis, FT-IR and NMR (¹H, ¹³C). The complex (4) was also analyzed by single crystal X-ray analysis which showed distorted trigonal bipyramidal geometry with polymeric bridging behavior. The complexes 1–6 were screened for antimicrobial activities and cytotoxicity. The results showed significant activity with few exceptions. The catalytic activity of complexes was assessed in transesterification reaction of Brassica campestris oil (triglycerides) to produce biodiesel (fatty acid methyl esters). The results showed that triorganotin(IV) complexes exhibited good catalytic activity than their di-analogues.     

One- and two-dimensional cobalt(II) coordination polymers derived from flexible bis(benzimidazole) and aromatic carboxylate co-ligands

Two new coordination polymers, formulated as [Co(L1)(btec)_0.5] _n (1) and {[Co(L2)(bdc)]·H₂O} _n (2) (L1 = 1,3-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H₂bdc = 1,3-benzenedicarboxylic acid, H₄btec = 1,2,4,5-benzenetetracarboxylic acid, L2 = 1,3-bis(benzimidazol-1-ylmethyl)benzene), have been hydrothermally synthesized and characterized by physicochemical and spectroscopic methods as well as single-crystal X-ray diffraction. The cobalt atoms present different environments, with a trigonal pyramidal geometry in 1 and a distorted octahedral configuration in 2. Complex 1 shows a 2D (4,4) network linked by L1 and btec^4? anions, giving an uninodal 4-connected sql topology with a point symbol of {4²·6²}, while complex 2 displays a 1D ladder-like chain structure, which is further assembled into a 3D supramolecular architecture via C–H···π hydrogen bonding interactions. The fluorescence properties of both complexes have been investigated in the solid state.     

Assembly of 1D and 3D cobalt(II) coordination polymers based on isophthalic acid and flexible benzimidazolyl-based ligands

Two new metal–organic coordination polymers {[Co(L1)(nip)]·H₂O} _n (1) and [Co(L2)(ip)] _n (2) (H₂ip = isophthalic acid, L1 = 1,3-bis(benzimidazol-1-ylmethyl)benzene, L2 = 1,4-bis(5-methylbenzimidazol-1-ylmethyl)benzene, H₂nip = 5-nitroisophthalic acid) have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as single-crystal X-ray diffraction analysis. The analysis reveals that complex 1 has a 1D double chain structure connected by L1 and nip^2? ligands, which is further assembled into a 3D bbf (moganite network) supermolecular framework via two types of C–H···O hydrogen bond interactions. Complex 2 possesses a 3D MOF with a four-connected cds (CdSO₄ network) topology. The fluorescence and catalytic properties of the complexes for the degradation of Congo red have been investigated.     

Guest inclusion in cyclic imides containing flexible tethers

Guest inclusion properties of two cyclic imides which have carboxylic acids connected through flexible tether, namely, 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid (1) and 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-cyclohexanecarboxylic acid (2) are studied. The crystals of host 1 containing one molecule of 1, the crystals of 4,4′-bipyridine (bpy) cocrystal of 1 containing one molecule of 1 and half molecule of bpy (1a), the crystals of 1,4-dioxane solvate of 1 containing two molecule of 1 and one and half molecule of 1,4-dioxane (1b) and the crystals of quinoline solvate of 1 containing one molecule of 1 and one molecule of quinoline (1c) in their crystallographic asymmetric units are investigated. Intermolecular hydrogen bonded two dimensional (2D) sheet structure of 1 and 3D channel network of 1b are comprised of cyclic R ₂ ² (8) hydrogen bond motifs; whereas cleavage of dimeric carboxylic acid R ₂ ² (8) motifs occurs in the structures of 1a and 1c in which 3D host–guest networks are comprised of discrete O–H···N and cyclic R ₂ ² (7) interactions, respectively. Various types of weak interactions between the two symmetry nonequivalent host molecule are found to be responsible for the formation of channels (14 × 11 Å) filled by guest 1,4-dioxane molecules in the crystal lattice of 1b. Two different solvates of 2 containing one molecule of 2 with a water molecule (2a) and one molecule of 2 with a quinoline molecule (2b) in their crystallographic asymmetric units, respectively, are also crystallized in different space groups. The quinoline molecules are held with host molecules by discrete O–H···N and C–H···O interactions and reside inside the voids formed by 3D repeated hexameric assemblies of host molecules in the crystal lattice of 2b.     

Design and synthesis of two-dimensional pillared MOF layers by connecting infinite one-dimensional chains via 4,4′-bipyridine

Two novel metal-organic frameworks, [Cd(Bna)(DMF)₂(H₂O)₂] _n · nDMF (I) (Bna = 2,2′-dihydroxy-l,l′-dinaphthyl-3,3′-dicarboxylate) and [Cd(Bna)(Bipy)(DMF)₂] _n (II) (Bipy = 4,4′-bipyridine) have been synthesized under mild conditions and structurally characterized. Crystal structural analyses reveal that complex I adots a 1D spiral structure with DMF guest molecules in the spiral by hydrogen bondings. Complex II is constructed by -Cd-Bna-Cd- zigzag chains, which are further connected by Bipy into a 2D sheet. X-ray powder diffraction and thermogravimetric analyses for I and II show that they are highly themally stable in the solid state.     

Mononuclear copper(II) complexes of bis-triazole-based macrocyclic Schiff base hydrazones: direct synthesis,EPR studies,magnetic and thermal properties

Mononuclear copper(II) complexes of 1,2,4-triazole-based Schiff base macrocyclic hydrazones, III and IV, have been reported. The prepared amorphous complexes have been characterized by spectroscopic methods, electron spray ionization mass spectrometry, and elemental analysis data. Electrochemical studies of the complexes in DMSO show only one quasi-reversible reduction wave at +0.43 V (ΔE = 70 mV) and +0.42 V (ΔE = 310 mV) for III and IV, respectively, which is assigned to the Cu(II) → Cu(I) reduction process. Temperature dependence of magnetic susceptibilities of III and IV has been measured within an interval of 2–290 K. The values of χ_M at 290 K are 1.72 × 10^?3 cm³ mol^?1 and 1.71 × 10^?3 for III and IV, respectively, which increases continuously upon cooling to 2 K. EPR spectra of III and IV in frozen DMSO and DMF were also reported. The trend g_|| > g⊥ > g_e suggests the presence of an unpaired electron in the d_x2?y2 orbital of the Cu(II) in both complexes. Furthermore, spectral and antimicrobial properties of the prepared complexes were also investigated.     

Synthesis,crystal structure,and electrochemical properties of Ni(II) and Cu(II) complexes with two unsymmetrical N2O2 Schiff base ligands

Nickel(II) and copper(II) complexes of two unsymmetrical tetradentate Schiff base ligands [Ni(Me-salabza)] (1), [Cu(Me-salabza)] (2) and [Ni(salabza)] (3), {H₂salabza = N,N′-bis[(salicylidene)-2-aminobenzylamine] and H₂Me-salabza = N,N′-bis[(methylsalicylidene)-2-aminobenzylamine]}, have been synthesized and characterized by elemental analysis and spectroscopic methods. The crystal structures of 2 and 3 complexes have been determined by single crystal X-ray diffraction. Both copper(II) and nickel(II) ions adopt a distorted square planar geometry in [Cu(Me-salabza)] and [Ni(salabza)] complexes. The cyclic voltammetric studies of these complexes in dichloromethane indicate the electronic effects of the methyl groups on redox potential.     

Anthracene Based Bulky Diol Hosts. Crystal Structures of a Free Host and of Inclusion Compounds with Dipolar Guests

X-ray crystal structures are reported of a free host compound 1, comprising two diphenylmethanol terminal groups attached to a central 9,10-ethynyl substituted anthracene unit, and of three inclusion compounds of a fluoren-9-ol substituted analogous host 2 with acetone, dimethyl sulphoxide (DMSO) and dimethylformamide (DMF) as guest, respectively. Despite the presence of two hydroxyl groups in 1, there is no O–H...O hydrogen bond between the molecules in the guest free crystal – only weaker C–H...O interactions and van der Waals' type connections. In the inclusion compounds of 2, H-bonded 1:2 host–guest associates are formed, where each of the host hydroxyl groups binds to a guest oxygen atom. The orientations of the host–guest connections in these complexes vary, being E for acetone and Z for both DMSO and DMF guests, relative to the host anthracene unit. The DMSO and DMF inclusion compounds of 2 proved to be isostructural.     

Solid-state thermal degradation behaviour of 1-D coordination polymers of Ni(II) and Cu(II) bridged by conjugated ligand

Monometallic complexes [Cudadb·yH₂O]_n (2) and [Nidadb·yH₂O]_n (3) and heterobimetallic complex [Cu_0.5Ni_0.5dadb·yH₂O]_n (4) {where dadbH₂ = 2,5-Diamino-3,6-dichloro-1,4-benzoquinone (1); y = 2–4; n = degree of polymerization} were characterized by elemental analysis, atomic absorption spectroscopy, infrared spectroscopy (FTIR) and powder X-ray diffraction. The thermal behaviour of the complexes was studied by thermal analysis (TG/DTA) under air as well as under helium atmospheres. The released gaseous products were investigated by evolved gas analysis performed by an online coupled mass spectrometer (TG/DTA-MS). Thermal degradation of 2 under helium atmosphere is distributed over five steps, whereas 3 and 4 exhibited only four degradation steps due to overlap of second and third degradation steps of into one major step. All the complexes exhibit three steps degradation under air. The complex 2 loses NH group in the second and HCl/Cl₂, CO groups simultaneously in third steps of decomposition under helium, whereas it loses NH and CO groups simultaneously in low temperature region of second step of degradation under air atmosphere as the loss of CO group is facilitated by air. EGA-MS under air and helium atmospheres shows that HCl, CO/CO₂ and (CN)₂ fragments are lost simultaneously at multiple steps, and not successively as predicted earlier. Rate of evolution of most evolved gases exhibits several maxima as a consequence of degradation followed by recombination reactions. Final residues under air and helium atmospheres correspond to the metal oxides and metals along with some carbonaceous matter.     

Syntheses, structures, and properties of zinc(II), cadmium(II), cobalt(II), and manganese(II) coordination polymers with tetraiodoterephthalate

The coordination chemistry of a rigid periodinated ligand, 2,3,5,6-tetraiodo-1,4-benzenedicarboxylic acid (H₂BDC-I₄), with a series of transition metal ions has been explored to afford five new coordination polymers {[M(BDC-I₄)(MeOH)₄](H₂BDC-I₄)(MeOH)₂} _n (M?=?Zn^II for 1, Cd^II for 2, Co^II for 3 and Mn^II for 4) and {[Mn(BDC-I₄)(MeOH)₄](DMF)} _n (5). All these complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric (TG) analysis, and X-ray crystallography. Single-crystal X-ray diffraction reveals that complexes 1?C4 are isostructural and have a one-dimensional chain structure. Upon the addition of the solvent DMF, the infinite linear chain array in 4 is converted to a 1-D wave-like chain motif in 5 with a different space group ( $ P\overline{1} $ for 4 and P2₁/c for 5). The difference between structures 1?C4 and 5 can be attributed to the coordination mode of carboxylate changing from trans to cis fashion. The Zn^II and Cd^II complexes 1 and 2 display similar emissions in the solid state, which essentially are intraligand transitions.     

Structurally diverse complexes from a bifunctional benzimidazole-carboxylate ligand

Three new complexes, namely {Ag₂(Hmbbc)₂(SO₃CF₃)₂}_n (1), Ag₂(Hmbbc)₂(NO₃)₂(DMF)₂(CH₃OH) (2), and Hg₂(Hmbbc)₂(I)₄(DMF)₂ (3) were constructed by the reaction of 4′-[4-methyl-6-(1-methyl-1H-benzimidazolyl-l-2-group)-2-n-propyl-1H-benzimidazolyl methyl]-biphenyl-2-carboxylic acid (Hmbbc) with Ag(I) or Hg(II) salts under solvothermal or solution reactions. In the complexes, the Hmbbc ligand exhibits different coordination modes, giving various crystal architectures. X-ray analysis demonstrates that 1 has a 2D layer structure, while 2 and 3 are binuclear. All three complexes are further extended into 3D supramolecular architectures through hydrogen bonds and π···π interactions. They exhibit luminescence emission in the solid state at room temperature.     

Synthesis, crystal structures and electrochemical properties of CoIII complexes with hexadentate ligand containing thioether-amidopyridyl donor set

Two new cobalt(III) complexes of the hexadentate ligand [1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane] (H₂bpctb) with N₄S₂ donor set atoms have been synthesized. A reaction of Co(CH₃COO)₂·4H₂O with (H₂bpctb) leads to the formation of [Co^III(bpctb)]PF₆ (1) having a CoN₂(pyridine)N′₂(amide)S₂(thioether) coordination by symmetric bpctb^2? ligand. A similar reaction under slightly different conditions, however, gives [Co^III(L ^a )(L ^b )] (2), resulting from a C–S bond cleavage reaction triggered by an acetate ion as a base, having CoN₂(pyridine)N′₂(amide)S(thioether)S′(thiolate) coordination. These two Co(III) complexes have been characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structures of [Co^III(bpctb)]PF₆ (1) in the form of the solvate (1·MeOH·H₂O) and of [Co^III(L ^a )(L ^b )] (2) have been determined by X-ray crystallography. The Co atoms of both complexes exhibit distorted octahedral geometry. The electrochemical investigation of [Co(bpctb)]PF₆·MeOH·H₂O (1·MeOH·H₂O) and [Co^III(L ^a )(L ^b )] (2) by cyclic voltammetry reveals a reversible Co^III–Co^II redox process at E _1/2 = ?0.32 V (ΔE _p = 80 mV); for 1, and E _1/2 = ?0. 87 V (ΔE _p = 70 mV) for 2.     

Interaction of hydroquinone and substituted derivatives with two cyclophane-like hosts: X-ray, molecular modelling and NMR studies

An investigation of the interaction of hydroquinone and selected substituted derivatives with the 28-membered tetrabenzo-cyclophane-type receptor 1 and a tetramethoxy-substituted variant, 2, each incorporating an O₄N₂-heteroatom set, is reported. In a preliminary solution study, aromatic solvent introduced shift (ASIS) experiments had indicated that deuterated benzene is intercalated between the two xylyl bridges of cyclophane 1. In parallel with this result, a further NMR study was consistent with the inclusion of hydroquinone between the xylyl groups of 1 to produce a face-to-face π-stacked arrangement, with additional host–guest stability being provided by a pair of simultaneous hydrogen bonds between host and guest. Owing to limited CHCl₃ or CH₂Cl₂ solubilities no association constant (K) for this host–guest system could be determined. However, use of the more soluble substituted guests 2,5-di-tert-butylquinone and 2,3-dimethylquinone enabled K values for 1 and 2 (ranging from 54 to 162 dm³ mol^?1) to be determined. Single crystal X-ray structure determinations of (solvated) 1 and 2 are reported, their highly different conformations reflecting their change in substitution pattern.