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.     

Cyanide-bridged one-dimensional bimetallic complexes based on a tridentate copper(II) building block: synthesis,crystal structures and magnetic properties

The reactions of [M^III(CN)₆]^3? (M = Cr or Co) with Cu^II complexes of a tridentate schiff base [Cu(aemp)Cl] or [Cu(aemp)Ac]₂ (Haemp = 2-[(2-amino-ethylimino)-methyl]-phenol) give rise to 1D cyanide-bridged bimetallic coordination polymers [Cu₄(aemp)₄(H₂O)₂][Cr(CN)₆]Cl (1) and [Cu₃(aemp)₃(H₂O)][Co(CN)₆]·2H₂O·MeOH (2). In complex 1, the six cyanide ligands of the [Cr(CN)₆]^3? moiety are involved in bridging, while in complex 2 only five cyanide ligands act as bridges to give a neutral chain. Magnetic studies reveal that complex 1 exhibits intermetallic ferromagnetic coupling, with J = 8.2 cm^?1.     

New copper(II) 2-(alkylamino)troponates

The copper aminotropones Cu[ON(R′)C₇H₄R-4]₂ [R = H, R′ = Me (13), Et (14), n-Pr (15), n-Bu (16), Bz (17), MenOCH₂CH₂ (20); R = i-Pr, R′ = Me (18), n-Pr (19), MenOCH₂CH₂ (21)] have been prepared from the corresponding aminotropones HN(R′)OC₇H₄R-4 (1–7) by reacting with copper(II) acetate in aqueous ethanol. 20, 21 contain the flavourant, menthol, as part of the ligand. The structures of 5 (R = H, R′ = Bz), a hydrogen-bonded dimer, 14 and 20, both incorporating square-planar, four-coordinate copper centres, have been determined by X-ray crystallography. The antibacterial activities of complexes 13, 17, 20 and 21 have been assayed against Staphylococcus waneri, an in vitro model of plaque inhibition effects, and found to be more active than a commercial toothpaste formulation, but less active than the O,O-chelated copper(II) complex of ethylmaltol.     

Synthesis and biological evaluation of 1-(4-(4-(4-[18F]fluorobenzyl)-1-piperazinyl)butyl)indolin-2-one as dopamine D4 receptor ligand

A potential dopamine D₄ receptor ligand, 1-(4-(4-(4-fluorobenzyl)-1-piperazinyl)butyl)indolin-2-one (4) was synthesized through a four-step process and its affinity and selectivity for dopamine D₂-like receptors was determined through in vitro receptor binding assay. [¹⁸F]4 was prepared using a one-pot two-step method with total radiochemical yield 21.2 % (decay-corrected). The molar radioactivity was around 135 GBq/μmol and the radiochemical purity was greater than 95.5 %. The partition coefficient (Log P) of [¹⁸F]4 was determined to be 2.10 ± 0.30 through octanol experiment. The in vivo biodistribution and the competitive distribution of [¹⁸F]4 in rat exposed that the tracer passes through blood–brain-barrier (BBB) and may specifically bind to D₄ receptor. Metabolite analysis revealed that there was no metabolism of [¹⁸F]4 in brain. Conclusively, these preliminary results demonstrated that [¹⁸F]4 shows promises as a radioligand for the in vivo study of dopamine D₄ receptor.     

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.     

On rhodium(III) chloride complexes with N,N-dimethylformamide

A prolonged storage of a solution of RhCl₃·nH₂O in N,N-dimethylformamide (DMF) at room temperature is attended by the consecutive formation of two precipitates, which mainly contain the [(CH₃)₂NH₂][RhCl₅(DMF)] complex (I) and the complex [RhCl₃(DMF)₃] (II) liberates. The addition of PPh₄Cl to an aqueous solution of complex I brings about the precipitation of [PPh₄][RhCl₄(H₂O)₂] (III). Complex II (a mixture of mer-and fac-isomers) can be obtained also by treatment of [RhCl₃(CH₃CN)₃] with DMF. In the course of the latter reaction, the formation of intermediate complex [RhCl₃(CH₃CN)₂(DMF)] (IV) is observed. Complexes I–IV are characterized by elemental analysis; complexes I, II, and IV are characterized by the IR and ¹H and ¹³C NMR spectra. The structures of III and IV are determined by X-ray diffraction analysis.     

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.     

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

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.     

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.     

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.     

Nonenzymatic sensor for glucose based on a glassy carbon electrode modified with Ni(OH)2 nanoparticles grown on a film of molybdenum sulfide

A glassy carbon electrode (GCE) was modified with nickel(II) hydroxide nanoparticles and a film of molybdenum sulfide. The nanocomposite was prepared by two-step electrodeposition. Scanning electron microscopy reveals that the nanoparticles are uniformly deposited on the film. Cyclic voltammetry and chronoamperometry indicate that this modified GCE displays a remarkable electrocatalytic activity towards nonenzymatic oxidation of glucose. Response is linear in the 10–1,300 μM concentration range (R ² ?=?0.9987), the detection limit is very low (5.8 μM), response is rapid (< 2 s), and selectivity over ascorbic acid, dopamine, uric acid, fructose and galactose is very good.

Synthesis of 15-(4-[11C]methylphenyl)pentadecanoic acid (MePPA) via Stille cross-coupling reaction

For experimental studies by animal PET [¹¹C]-labeled 15-(4-methylphenyl)pentadecanoic acid (MePPA) is an attractive alternative to the radioiodinated 15-(4-iodophenyl)pentadecanoic acid (IPPA) which has widely been used for imaging of fatty acid metabolism. The important physiological aspect is that the iodine atom and the methyl substituent have similar steric and lipophilic properties. For preparation of [¹¹C]MePPA, Stille cross-coupling reaction was applied since the same tin precursor as for the radiosynthesis of IPPA and readily available [¹¹C]CH₃I can be used. Unsaturated tris(dibenzylideneacetone)dipalladium(0)/tri(o-tolyl)phosphine [Pd₂(dba)₃/P(o-tolyl)₃] was taken as the catalytic system. The reaction conditions were optimized with respect to temperature, time, solvent and amount of precursor. The best radiochemical yields of 73 ± 2.8% (decay corr.) were obtained using 0.525 mg tin precursor in DMF at 80 °C already after a reaction time of 10 min. The labeled methyl ester was hydrolyzed by 1 M NaOH/EtOH at 80 °C within 3 min to give [¹¹C]IPPA in a RCY of 62 ± 3.0%. The radiochemical purity of the product assured by HPLC was >99% and the overall preparation time including HPLC purification and formulation was 40 min.     

Synthesis,Characterization, and Crystal Structure of Tertiary Phosphine-Substituted Diiron Propanedithiolate Complexes

As the active site models of [FeFe]-hydrogenase, two new tertiary phosphine-substituted diiron propanedithiolate complexes [(μ-PDT)Fe₂(CO)₅L] (PDT = SCH₂CH₂CH₂S, L = P(PhMe-m)₃, 1; PPh₂(CH₂CH₂CH₃), 2) have been prepared through carbonyl substitution reactions of parent complex [(μ-PDT)Fe₂(CO)₆] (A) with P(PhMe-m)₃ or PPh₂(CH₂CH₂CH₃) in the presence of the decarbonylating agent Me₃NO·2H₂O in MeCN at room temperature. The new complexes 1 and 2 were fully characterized by elemental analysis, FT-IR, ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy, as well as for 1 by X-ray crystallography. In addition, the crystal structure of 1 has indicated that the phosphorus atom of the P(PhMe-m)₃ ligand resides in an apical position of the pseudo-square-pyramidal geometry of the tertiary phosphine-coordinated Fe₂ atom.     

Synthetic aspects, crystal structures and antibacterial activities of manganese(III) and cobalt(III) complexes containing a tetradentate Schiff base

Three new Schiff base complexes, namely [Mn(L)Cl] · H₂O (1), [Co(L)Cl]₂ · 2CH₃COCH₃ (2) and [Co(L)NCS]₂ (3), where H₂L = 2,2′-[propane-1,2-diylbis(nitriloeth-1-yl-1-ylidene)]diphenol, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base ligand (H₂L). While the mononuclear Mn(III) complex 1 was obtained with MnCl₂ in acetone medium, the same synthetic system yielded the binuclear Co(III) complex 2 in the presence of CoCl₂. Dissolution of 1 and 2 followed by crystallization with ammonium thiocyanate in methanol yielded two isostructural phenoxo-bridged binuclear complexes, namely [Mn(L)NCS]₂ (previously reported by us) and a new complex [Co(L)NCS]₂ (3), respectively. All the complexes 1–3 have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 adopts a distorted tetragonal pyramidal geometry while 2 and 3 comprise dimeric Co(III) units with bridging phenolate oxygen atoms. All the complex units in 1–3 and the respective solvent molecules are held together by weak intermolecular H-bonding to constitute a supramolecular network in the solid state. The antibacterial activity of the complexes has been tested against some Gram(+) and Gram(?) bacteria.     

Highly sensitive electrocatalytic determination of pyrazinamide using a modified poly(glycine) glassy carbon electrode by square-wave voltammetry

A new voltammetric sensor based on electropolymerization of glycine at glassy carbon electrode (GCE) was developed and applied to determine of pyrazinamide (PZA) by square-wave voltammetry (SWV). The initial cyclic voltammetric studies showed an electrocatalytic activity of poly(Gly)/GCE on redox system of pyrazinamide in 0.1 mol L^?1 phosphate buffer solution pH 7.5, with E _Pc and E _Pa in ?0.85 and ?0.8 V (versus E _Ag/AgCl), respectively. Studies at different scan rates suggest that the redox system of pyrazinamide at poly(Gly)/GCE is a process controlled by diffusion in the interval from 10 to 100 mV s^?1. Square-wave voltammetry-optimized conditions showed a linear response of PZA concentrations in the range from 0.47 to 6.15 μmol L^?1 (R?=?0.998) with a limit of detection (LOD) of 0.035 μmol L^?1 and a limit of quantification (LOQ) of 0.12 μmol L^?1. The developed SWV-poly(Gly)/GCE method provided a good intra-day (RSD?=?3.75 %) and inter-day repeatability (RSD?=?4.96 %) at 4.06 μmol L^?1 PZA (n?=?10). No interference of matrix of real samples was observed in the voltammetric response of PZA, and the method was considered to be highly selective for the compound. In the accuracy test, the recovery was found in the range of 98.2 and 104.0 % for human urine samples and pharmaceutical formulation (tablets). The PZA quantification results in pharmaceutical tablets obtained by the proposed SWV-poly(Gly)/GCE method were comparable to those found by official analytical protocols.     

Manganese(III) complexes with tetradentate (N2O2) Schiff bases and dicyanamide

New Mn(III) complexes with Schiff bases and dicyanamide are synthesized: [Mn(Salpn)N(CN)₂] _n (two polymorphous modifications, Ia and Ib), {[Mn(5-BrSalen)N(CN)₂] · CH₃OH} _n (II), and [Mn(3-MeOSalen)N(CN)₂(H₂O)] (III), where SalpnH₂ = N,N′-bis(salicylidene)-1,3-diaminopropane, 5-BrSalenH₂ = N,N′-bis(5-bromosalicylidene)-1,2-diaminoethane, and 3-MeOSalenH₂ = N,N′-bis(3-methoxysalicylidene)-1,2-diaminoethane. Complexes Ia, Ib, and II have the polymer structure in which the dicyanamide anion binds the paramagnetic Mn(III) complexes with the Schiff bases into one-dimensional chains. Unlike them, in complex III the monomer units containing water and the dicyanamide anion as terminal ligands form dimers due to hydrogen bonds. The study of the magnetic properties of complexes Ia and II shows a weak antiferromagnetic interaction between the Mn³⁺ ions through the dicyanamide bridges in these complexes.     

The crystal structures of α,ω-diaminoalkanecadmium(II) tetracyanonickelate(II)-aromatic molecule inclusion compounds. IV. (1,6-Diaminohexane)cadmium(II) tetracyanonickelate(II)-m-toluidine(1/1),-p-toluidine(1/1), and-2,4-xylidine(1/1) clathrates,and the coordination complex bis(p-toluidine) (1,6-diaminohexane)cadmium(II) tetracyanonickelate(II)

The crystal structures of the four title compounds have been analyzed by single crystal X-ray diffraction methods at room temperature. Three with a general formula Cd[NH₂(CH₂)₆NH₂]Ni(CN)₄·G (G=m-toluidine,Im;p-toluidine,Ip; and 2,4-xylidine,Ix) are the inclusion compounds of the respective aromatic molecules in the three-dimensional metal complex host (1,6-diaminohexane)cadmium(II) tetracyanonickelate(II). The remaining one is a coordination complex ofp-toluidine, bis(p-toluidine) (1,6-diaminohexane)cadmium(II) tetracyanonick-elate(II),II, Im, Ix, andII crystallize under similar experimental conditions;Ip is obtained using thep-toluidinemesitylene mixture at higher dilution than that used forII. Im crystallizes in the tri linic space group \(P\bar 1\) , witha=9.725(2),b=7.598(1),c=7.177(1) Å, α=90.44(1), β=98.80(1), γ=95.70(1)^o, andZ=1 (the final conventionalR=0.037 for 3526 reflections);Ip: monoclinic,P2/m,a=9.540(2),b=7.611(1),c=7.120(1) Å, β=100.95(1)^o, andZ=1 (R=0.027 for 1700 reflections);Ix: monoclinic,P2/m,a=9.628(2),b=7.613(1),c=7.122(1) Å, β=100.01(1)^o, andZ=1 (R=0.049 for 2704 reflections);II: monoclinic,P2₁/n,a=12.107(3),b=10.117(2),c=12.471(3) Å, β=113.67(2)^o, andZ=2 (R=0.037 for 2616 reflections). The structures ofIm, Ip andIx are similar to that of theo-toluidine inclusion compound of the same metal complex host. InII atrans pair of thep-toluidine molecules to the cadmium atom in the two-dimensional network formed by thecatena-μ-linkages of ?Cd?NH₂(CH₂)₆NH₂?Cd? and ?NC?Ni?CN?Cd?NC?Ni?CN?intersecting at each Cd atom; two cyanide groups of the tetracyanonickelate(II) moiety have free N-ends.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

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.