Chiral resolution of l- and d-alanine and a racemic macrocyclic nickel(II) complex: synthesis and crystal structures

The reactions of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO₄)₂ with l- and d-alanine in acetonitrile/water gave two six-coordinate enantiomers formulated as [Ni(RR-L)(l-Ala)](ClO₄)·2CH₃CN (1) and [Ni(SS-L)(d-Ala)](ClO4) (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane, Ala^? = alanine anion), respectively. Evaporation from the remaining solutions gave two four-coordinate enantiomers characterized as [Ni(SS-L)](ClO₄)₂ (S-3) and [Ni(RR-L)](ClO₄)₂ (R-3), respectively. Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni(II) atom has a distorted octahedral coordination geometry, being coordinated by four nitrogen atoms of L in a folded configuration, plus one carboxylate oxygen atom and one nitrogen atom of l- or d-Ala^? in mutually cis-positions. Complexes 1 and 2 are supramolecular stereoisomers, constructed via hydrogen bonding between [Ni(RR-L)(l-Ala)]⁺ or [Ni(SS-L)(d-Ala)]⁺ monomers to form 1D hydrogen-bonded zigzag chains. The homochiral natures of complexes 1 and 2 have been confirmed by CD spectroscopy.     

Cis–trans isomerization and spin multiplicity dependences on the static first hyperpolarizability for the two-alkali-metal-doped saddle[4]pyrrole compounds

Doping two alkali-metal atoms (Li and Na) into the saddle-shaped saddle[4]pyrrole forms four new two-alkali-metal-doped compounds with alkalide or electride characteristic. They are cis-LiNa(saddle[4]pyrrole) isomers 1(singlet) and 2(triplet), and trans-Li(saddle[4]pyrrole)Na isomers 3(singlet) and 4(triplet). The four structures with all-real frequencies are obtained at the density functional theory (DFT) B3LYP/6-311+G(d) level. All calculations of electric properties have been carried out at the second order Møller–Plesset perturbation theory (MP2) level. The order of the β ₀ values is 3.54 × 10³ for trans-4(triplet) <1.51 × 10⁴ for cis-1(singlet) <3.57 × 10⁴ for cis-2(triplet) <2.34 × 10⁵ a.u. for trans-3(singlet). The static first hyperpolarizability (β ₀) depends on the cis–trans isomerization and spin multiplicity. The result demonstrates that the cis–trans isomerization and spin multiplicity controls of the second-order NLO response are possible.     

Synthesis and biological activity of Magnesium(II) complexes of heptaaza Schiff base macrocyclic ligands; 1H and 13C chemical shifts computed by the GIAO-DFT and CSGT-DFT methodologies

Two new pendant armed Schiff base macrocyclic complexes, [MgL¹](ClO₄)₂ (1), and [MgL²](ClO₄)₂ (2), have been prepared via cyclocondensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with two hexadentate hexaamines, ten and tmen, in the presence of Mg(II) ion. The ligands are 15-membered pentaaza macrocycles having two 2-aminoethyl pendant arms. The newly prepared complexes are investigated by IR, ¹H NMR, ¹³C{¹H} NMR, DEPT(135), COSY(H, H) and HMQC spectroscopic methods. The antimicrobial screening of newly prepared complexes, 1 and 2, as well as previously prepared similar complexes, [MgL³](ClO₄)₂ (3) and [MgL⁴](ClO₄)₂ (4), against Escherichia coli, Staphylococcus aureus and candidia albicans showed that the macrocyclic complexes of Mg(II) containing 15-membered pentaaza ring (1, 2 and 3) have no activity. Where as the compound 4, which contain 16-membered pentaaza ring, had remarkable inhibition zone on the culture of S. aureus and E. coli as compared with standard drugs. The ¹H and ¹³C chemical shieldings of gas phase complexes were also studied by the gauge independent atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) methods at the level of density functional theory (DFT). The computed ¹³C chemical shifts are in reasonably good agreement with the experimental data.     

Crown ether styryl dyes

Novel styryl dyes (trans-2a,b) containing a 15-crown-5 ether moiety and anN-sulfobenzyl spacer were synthesized. The reactions oftrans-2a,b with Mg(ClO₄)₂ in MeCN afford dimeric complexes. During photolysis of the lattertrans-cis isomerization to give anion-“capped” complexes (cis-2a,b)·Mg²⁺ and stereospecific [2+2] autocycloaddition to yield cyclobutane derivative occur in parallel The ratio of the two transformation pathways of dyes2a,b depends on the spacer type. To interpret the experimental data, the molecular-mechanics and semiempirical quantum-chemical calculations were performed.     

Synthesis,crystal structures and phosphodiesterase activities of alkoxide-bridged asymmetric dinuclear nickel(II) complexes

An asymmetric dinuclear ligand, N-4-methyl-homopiperazine-N′-[N-(2-pyridylmethyl)-N-2-(2-pyridylethyl)amine]-1,3-diaminopr-opan-2-ol (HL) and two dinuclear Ni(II) complexes [Ni₂L(DNBA)₂]ClO₄ (1) and [Ni₂L(BPP)₂]ClO₄·2H₂O (2) (3,5-dinitrobenzoic acid, bisphenyl phosphate) have been synthesized and characterized. Single crystal X-ray crystallographic analysis reveals that the coordination environments of the two Ni(II) atoms in complexes 1 and 2 are five and six coordinate, respectively. The phosphodiesterase activity of a di-Ni(II) complex Ni₂L formed in situ from a 2:1 mixture of Ni²⁺ and HL was investigated using bis(4-nitrophenyl) phosphate (BNPP) as the substrate. The pH dependence of the rate of BNPP cleavage in aqueous buffer indicates a bell-shaped profile with an optimum at about pH 8.4, which is parallel to the formation of the dinuclear species [Ni₂LOH]²⁺ according to UV–vis spectroscopy. At pH 8.4 and 25 °C, the k _cat (7.40 × 10^?5 s^?1) is ca.10⁶-fold higher than that of the uncatalyzed reaction. A possible mechanism for BNPP cleavage promoted by Ni₂L is proposed.     

Interaction between chiral ions: synthesis and characterization of tartratovanadates(V) with tris(2,2′-bipyridine) complexes of iron(II) and nickel(II) as cations

Four new compounds composed of chiral complex cations and anions: Δ-[Fe(bpy)₃] Λ-[Fe(bpy)₃][V₄O₈((2R,3R)-tart)₂]·12H₂O (1), Δ-[Fe(bpy)₃]₂Λ-[Fe(bpy)₃]₂[V₄O₈((2R,3R)-tart)₂][V₄O₈((2S,3S)-tart)₂]·24H₂O (2), Δ-[Ni(bpy)₃]Λ-[Ni(bpy)₃][V₄O₈((2R,3R)-tart)₂]·12H₂O (3) and Δ-[Ni(bpy)₃]₂Λ-[Ni(bpy)₃]₂[V₄O₈((2R,3R)-tart)₂][V₄O₈((2S,3S)-tart)₂]·24H₂O (4) have been prepared. The compounds have been characterized by spectral methods, and their thermal decomposition was studied by simultaneous DTA, TG measurements. The final products after dynamic decomposition and additional heating were Fe₂V₄O₁₃ for 1 and 2 and Ni(VO₃)₂ for 3 and 4. The crystal structures determined for 1, 2 and 4 have evidenced that 1 is “hemiracemic” and 2 and 4 are “fully racemic” compounds.     

Synthesis and thermal behavior study of complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 (X = Cl,Br, I,N3, NCO,SCN) and 4-eb-p-phen [bis(4-ethylbenzyl)p-phenylenediimine]

The Schiff base bis(4-ethylbenzyl) p-phenylenediimine, 4-eb-p-phen (1), and six new dimeric Pd(II) complexes of the type [Pd(μ-X)(4-eb-p-phen)]₂ {X = Cl (2), Br (3), I (4), N₃ (5), NCO (6), SCN (7)} have been synthesized and characterized by elemental analysis, IR spectroscopy, and ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 2–7 has been investigated by means of thermogravimetry and differential thermal analysis. From the final decomposition temperatures, the thermal stability of the complexes can be ordered in the following sequence: 3 > 4 > 7 > 2 ≈ 5 > 6. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction (XRD).     

fac-Cobalt(III)-azido complexes derived from substituted pyridyl-based tridentate amines

Four new mononuclear triazido-cobalt(III) complexes [Co(L ^1/2/4 )(N₃)₃] and [Co(L ³ )(N₃)₃]·CH₃CN where L ¹  = [(2-pyridyl)-2-ethyl]-(2-pyridylmethyl)-N-methylamine, L ²  = [(2-pyridyl)-2-ethyl]-[6-methyl-(2-pyridylmethyl)]-N-methylamine, L ³  = [(2-pyridyl)-2-ethyl]-[3,5-dimethyl-4-methoxy-(2-pyridylmethyl)]-N-methylamine, and L ⁴  = [(2-pyridyl)-2-ethyl]-[3,4-dimethoxy-(2-pyridylmethyl)]-N-methylamine, respectively, were synthesized and structurally characterized. The four complexes were characterized by elemental microanalyses, IR and UV–VIS spectroscopy and X-ray single crystal crystallography. The complexes display two strong IR bands over the frequency region 2,020–2,050 cm^?1 assigned for the asymmetric stretching frequency, ν_a(N₃) of the coordinated azides indicating facial geometry. The molecular structure determinations of the complexes were in complete agreement with fac-[Co(L)(N₃)₃] conformation in distorted octahedral Co(III) environment.     

Copper complexes of two isomeric NS2-macrocycles

Two isomeric NS₂-macrocycles incorporating a xylyl group at ortho (o -L) and meta (m -L) positions were employed and their copper complexes (1?C5) were prepared and structurally characterized. The copper(II) nitrate complexes [Cu(L)(NO₃)₂] (1: L = o -L, 2: L = m -L) for both ligands were isolated. In each case, the copper center is five-coordinated with a distorted square pyramidal geometry. Despite the overall geometrical similarity, 1 and 2 show the different ligand conformation due to the discriminated packing pattern. Reaction of o -L with copper(II) perchlorate afforded complex 3 containing two independent complex cations [Cu(o -L)(H₂O)(DMF)(ClO₄)]⁺ and [Cu(o -L)(H₂O)(DMF)]²⁺; the coordination geometry of the former is a distorted octahedron while the latter shows a distorted square pyramidal arrangement. In the reactions of copper(I) halides (I or Br), o -L gave a mononuclear complex [Cu(o-L)I] (4) with a distorted tetrahedral geometry, while m -L afforded a unique exodentate 2:1 (ligand-to-metal) complex [trans-Br₂Cu(m-L)₂] (5) adopting a trans-type square-planar arrangement.     

Syntheses,crystal structures and magnetic properties of three new binuclear Ni(II) complexes derived from tripodal tetradentate (N4) ligands

Three new binuclear Ni(II) complexes [{Ni(L_22py)Cl}₂](ClO₄)₂ (1), [{Ni(L_23py)Cl}₂](ClO₄)₂ (2), and [{Ni(L_33py)Cl}₂](ClO₄)₂ (3), {L_22py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,2-diaminoethane, L_23py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,3-diaminopropane, L_33py = N-(2-pyridylmethyl)-N-(3-aminopropyl)-1,3-diaminopropane} have been synthesized. Single crystal X-ray structure analysis showed that in each complex two distorted octahedral Ni(II) ions are bridged asymmetrically by a pair of chloride anions. Variable temperature magnetic susceptibility measurements of 1 and 3 revealed dominant ferromagnetic exchange interactions.     

Copper(II), iron(III) and cobalt(III) complexes of the pendent-arm cyclam derivative 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane

The interaction of Cu(II), Fe(III) and Co(III) with 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane (L ³ ) incorporating a pendent amine group has led to isolation of the new octahedral complexes [Cu(HL ³ )(ClO₄)₂]Cl·H₂O (1), [Fe(L ³ )Cl](S₂O₆)·H₂O (2), [Co(L ³ )Cl](ClO₄)_1.5Cl_0.5·0.25H₂O (3), [Co(HL ³ )Cl₂](ClO₄)₂·H₂O (4) and [Co(L ³ )Cl]₂(S₂O₄)(ClO₄)₂ (5). In (1) the copper ion occupies the macrocyclic cavity of protonated (–NH₃ ⁺) L ³ which is present in its trans-III configuration; weakly bound ClO₄ ^? ligands occupy the axial positions. The X-ray structure of (2) showed that Fe(III) occupies the N₄-macrocyclic cavity of L ³ in a trans-III configuration, with the pendent amine group binding in an axial position. The remaining axial position is occupied by a Cl^? ligand. Chromatography of the product obtained from the reaction of Na₃[Co(CO₃)₃] with L ³ yielded three fractions. Fraction 1 yielded crystals (3) composed of three crystallographically independent species incorporating cations of type [Co(L ³ )Cl]²⁺ with very similar structures; in each case the macrocyclic ring nitrogens of L ³ are bound to the Co(III) in an asymmetric cis-fashion. Fraction 2 yielded the trans-III octahedral cationic complex (4) incorporating L ³ in its protonated form. The Co(III) complex (5) from fraction 3 shows a different coordination arrangement to the products from fractions 1 or 2. The macrocyclic ring coordinates in its trans-III form, but the axial sites in this case are occupied by the pendent-NH₂ group and a Cl^? ligand.     

Nucleic Acid Binding Behavior and Cytotoxicity Properties of a Ruthenium(II) Polypyridyl Complex

The binding of [Ru(IP)₂(dppz-11-CO₂Me)]²⁺ (1) {IP = imidazo[4,5-f][1,10]phenanthroline, dppz-11-CO₂Me = dipyrido[3,2-a:2′,3′-c]phenazine-11-carboxylic acid methyl ester} to calf thymus DNA and yeast tRNA has been investigated by UV–Vis spectroscopy, fluorescence spectroscopy, viscosity, as well as equilibrium dialysis and circular dichroism. In addition, the antitumor activities of complex 1 have been evaluated by the MTT method. On the basis of the spectroscopic results, the binding mode of complex 1 to CT-DNA and yeast tRNA is intercalation. However, DNA binding with complex 1 is stronger than RNA binding with complex 1, and complex 1 is a better candidate for an enantioselective binder to CT-DNA than to yeast tRNA. These results indicate that the structures of DNA and RNA have significant effects on the binding behaviors of complex 1. Furthermore, complex 1 demonstrates different antitumor activities against selected cancer cell lines in vitro.     

Transformation of a ditopic Schiff base nickel(II) nitrate complex into an unsymmetrical Schiff base complex by partial hydrolytic degradation: structural and density functional theory studies

A new Schiff base complex [Ni(H₂L¹)(NO₃)](NO₃) (1) (H₂L¹ = 3-[N,N′-bis-2-(5-bromo-3-(morpholinomethyl) salicylideneamino) ethyl amine]) was synthesized from reaction of the ditopic ligand H₂L¹ with Ni(NO₃)₂ in anhydrous MeOH. Complex 1 is stable in the solid state, but prone to hydrolysis. Recrystallization of 1 from wet MeOH led to the isolation of a novel unsymmetrical complex [Ni(HL²)(NO₃)](NO₃) (2) (HL² = 2-[(2-(2-aminoethylamino) ethylimino) ethyl)-5-bromo-3-(morpholino methyl) salicylidene amine]). X-ray single-crystal analysis of complex 2 showed that complex 1 had undergone partial decomposition of one imine bond. In contrast, the Schiff base complex [Ni(HL³)](NO₃) (3) (H₂L³ = N,N′-bis(5-methyl-salicylidene) diethylenetriamine) was stable in wet methanol, and the single-crystal structure of 3 showed that the Ni(II) center was coordinated in an unsymmetrical square planar geometry. Density functional theory calculations were performed in order to obtain a geometry-optimized model of complex 1, in which the Ni(II) center was coordinated in a similar manner as that in complex 3. The thermodynamic parameters were calculated, in order to rationalize the difference in hydrolytic reactivity between complexes 1 and 3.     

Complexes built with a scorpion-type tripodal ligand and metal ions: syntheses, structural features, electrochemical properties and magnetic properties

The complexes [Fe(bpz*mpy)₂](ClO₄)₂ (1a), [Cu(bpz*mpy)₂](ClO₄)₂ (1b) and [Ag(bpz*mpy)(Ph₃P)](ClO₄) · H₂O (2) (bpz*mpy = pyridin-2-yl-bis(3,5-dimethylpyrazol-1-yl)methane) have been synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analysis reveals that the central Fe^II and Cu^II ions in complexes 1a and 1b are located on a twofold rotation axis and have a distorted octahedral coordination sphere, while the Ag^I center in complex 2 is tetrahedrally coordinated. The electrochemical properties of complex 1b have been investigated. Furthermore, a variable temperature magnetic susceptibility study of complex 1a has also been performed over the measured temperature range 2–300 K.     

Synthesis and structural characterisation of rhodium hydride complexes bearing N-heterocyclic carbene ligands

Addition of excesses of N-heterocyclic carbenes (NHCs) IEt₂Me₂, IⁱPr₂Me₂ or ICy (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene; IⁱPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; ICy = 1,3-dicyclohexylimidazol-2-ylidene) to [HRh(PPh₃)₄] (1) affords an isomeric mixture of [HRh(NHC)(PPh₃)₂] (NHC = IEt₂Me₂ (cis-/trans-2), IⁱPr₂Me₂ (cis-/trans-3), ICy (cis-/trans-4) and [HRh(NHC)₂(PPh₃)] (IEt₂Me₂(cis-/trans-5), IⁱPr₂Me₂ (cis-/trans-6), ICy (cis-/trans-7)). Thermolysis of 1 with the aryl substituted NHC, 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (IMesH₂), affords the bridging hydrido phosphido dimer, [{(PPh₃)₂Rh}₂(μ-H)(μ-PPh₂)] (8), which is also the reaction product formed in the absence of carbene. When the rhodium precursor was changed from 1 to [HRh(CO)(PPh₃)₃] (9) and treated with either IMes (=1,3-dimesitylimidazol-2-ylidene) or ICy, the bis-NHC complexes trans-[HRh(CO)(IMes)₂] (10) and trans-[HRh(CO)(ICy)₂] (11) were formed. In contrast, the reaction of 9 with IⁱPr₂Me₂ gave [HRh(CO)(IⁱPr₂Me₂)₂] (cis-/trans-12) and the unusual unsymmetrical dimer, [(PPh₃)₂Rh(μ-CO)₂Rh(IⁱPr₂Me₂)₂] (13). The complexes trans-3, 8, 10 and 13 have been structurally characterised.     

Synthesis, characterisation and catalytic activities of manganese(III) complexes of pyridoxal-based ONNO donor tetradenatate ligands

Reaction of Mn^II(CH₃COO)₂ with dibasic tetradentate ligands, N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-en, I), N,N′-propylenebis(pyridoxylideneiminato) (H₂pydx-1,3-pn, II) and 1-methyl-N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-1,2-pn, III) followed by aerial oxidation in the presence of LiCl gives complexes [Mn^III(pydx-en)Cl(H₂O)] (1) [Mn^III(pydx-1,3-pn)Cl(CH₃OH)] (2) and [Mn^III(pydx-1,2-pn)Cl(H₂O)] (3), respectively. Crystal and molecular structures of [Mn(pydx-en)Cl(H₂O)] (1) and [Mn(pydx-1,3-pn)Cl(CH₃OH)] (2) confirm their octahedral geometry and the coordination of ligands through ONNO(2-) form. Reaction of manganese(II)-exchanged zeolite-Y with these ligands in refluxing methanol followed by aerial oxidation in the presence of NaCl leads to the formation of the corresponding zeolite-Y encapsulated complexes, abbreviated herein as [Mn^III(pydx-en)]-Y (4), [Mn^III(pydx-1,3-pn)]-Y (5) and [Mn^III(pydx-1,2-pn)]-Y (6). These encapsulated complexes are used as catalysts for the oxidation, by H₂O₂, of methyl phenyl sulfide, styrene and benzoin efficiently. Oxidation of methyl phenyl sulfide under the optimized reaction conditions gave ca. 86% conversion with two major products methyl phenyl sulfoxide and methyl phenyl sulfone in the ca. 70% and 30% selectivity, respectively. Oxidation of styrene catalyzed by these complexes gave at least five products namely styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde with a maximum of 76.9% conversion of styrene by 4, 76.3% by 5 and 76.0% by 6 under optimized conditions. The selectivity of the obtained products followed the order: benzaldehyde > benzoic acid > styrene oxide > phenylacetaldehyde > 1-phenylethane-1,2-diol. Similarly, ca. 93% conversion of benzoin was obtained by these catalysts, where the selectivity of the products followed the order benzil > benzoic acid > benzaldehyde-dimethylacetal. Tests for the recyclability and heterogeneity of the reactions have also been carried. Neat complexes are equally active. However, the recycle ability of encapsulated complexes makes them better over neat ones.     

Novel redox receptors for ion-pair and α-amino acid: synthesis and complexation properties of calix[4]arene derivatives bearing large conjugated ferrocene groups

By reacting calix[4]arene 1,3-bi-hydrazide derivative (2) with formacylferrocene in “1?+?2” condensation mode, novel calix[4]arene derivative bearing two conjugated ferrocene groups (3) was obtained in yield of 88%. By reacting 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (5) with 1,1′-diacetylferrocene hydrazone (4) in “1?+?1” condensation mode, novel calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge (6) was synthesized in yield of 83%. The structures and conformations of new compounds were confirmed by elemental analyses, IR spectra, ESI-MS, ¹H NMR, etc. The electrochemical cyclic voltammetry experiments revealed that compounds 3 and 6 possessed excellent reversible electrochemical properties. The ¹H NMR titration study showed that compound 6 possessed excellent complexation abilities for NaH₂PO₄ and glycine in 1:1 host–guest complex with the association constants of 3,850 and 2,460?M^?1, respectively.     

Syntheses and extraction properties of novel biscalixarene and thiacalix[4]arene hydrazone derivatives

By reacting thiacalix[4]arene with p-tosyloxyethoxylbenzaldehyde 1, 3-bis(benzaldehyde-4-oxyethyloxy)-p-tert-butylthiacalix[4]arene (2) were prepared in yield of 65%. Refluxing compound 2 with aniline, salicylic hydrazide, nicotinic hydrazide and isonicotinic hydrazide, novel ringopening 1,3-bis-arylformyl-hydrazone substituted thiacalix[4]arene derivatives (3a–3d) were obtained in yields of 77–89%. Refluxing compound 2 with o-phenylendiamine, oxalyl dihydrazide, malonic dihydrazide and adipic dihydrazide in “1 + 1” intermolecular condensation mode under diluted condition, novel 1,3-bis-acyl hydrazone-bridged calix[4]arene derivatives (4a–4d) were prepared in good yields. Moreover, by condensating compound 2 with 1,3-bis(hydrazinocarbonyl-methoxy)-p-tert-butylcalix[4]arene (5), the first example of hydrazone-bridged biscalixarene (6) with calix[4]arene and thiacalix[4]arene subunits was facilely synthesized in yield of 90%. The noncompetitive and competitive extracting experiments showed that these novel hosts were good receptors for both metal cations and α-amino acids. Compounds 3a–3d and 4a–4d showed similar binding properties with high extraction percentage but low extracting selectivities. Biscalixarene 6 exhibited not only high extracting abilities but also good extracting selectivities.     

Crystal structures, cyclic voltammetry and DNA binding of two mononuclear nickel(II) complexes

Two unsymmetrical complexes, [NiL¹]ClO₄ (1) and [NiL²]ClO₄ (2) have been synthesized and characterized by IR, UV, ES-MS and single crystal X-ray diffraction, where HL¹ and HL² are, respectively, the [1+1] condensation products of 2,6-diformyl-4-X-phenol (X = F or CH₃) with N ¹-(2-aminoethyl)-N ²-(4-nitrobenzyl) ethane-1,2-diamine. The coordination geometry of the metal in both complexes can be approximately described as square planar with a mean plane deviation of 0.032 Å in complex 1 and 0.027 Å in complex 2, respectively. The binding activities of the complexes toward calf-thymus DNA have been analyzed by spectroscopy and viscosity methods. The binding constants of 1 and 2 obtained from UV spectroscopic studies are 5.43 × 10⁵ and 1.83 × 10⁵ M^?1, respectively, while the linear Stern–Volmer quenching constants obtained from fluorescence spectroscopic studies are 0.83 × 10³ and 0.71 × 10³ M^?1, respectively. The cyclic voltammograms of the complexes show a pseudo-reversible electrochemical process.     

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.