Jozef Kožíšek

Tricyanomethanide and Dicyanamide Complexes of Cu(II), Ni(II), Co(II), Their Structures and Properties

Abstract This review summarizes data for all known tricyanomethanide and dicyanamide compounds of copper(II), nickel(II) and cobalt(II). The possible bonding modes of [C(CN)3]− and [N(CN)2]− ions and their influence on infrared spectra are demonstrated. Preparative methods are briefly described and structural data for crystallographically characterized compounds are given. Data for electronic and ESR spectra, magnetic susceptibilities, vibrational and ESCA spectra are reviewed and consequences following from these techniques for structural characteristics are discussed. The most striking features of the behaviour of both pseudohalide ligands are their polydentate character and ability for bridging. This ability is revealed by many physical properties, especially by the temperature dependence of magnetic susceptibilities, in which exchange interaction through pseudohalide bridges is manifested. Reactivity of C(CN)3 and N(CN)2 groups in the coordination sphere of Cu(II) and Ni(II) is mentioned.

Expedient and Practical Synthesis of CERT-Dependent Ceramide Trafficking Inhibitor HPA-12 and Its Analogues

The practical stereodivergent route to both syn- and anti-diastereomers of 1-substituted 3-aminobutane-1,4-diols based on the crystallization-induced asymmetric transformation (CIAT) approach was completed. This led to the revision of the reported stereochemistry of the first inhibitor of CERT-dependent ceramide trafficking HPA-12 from (R,R)-anti- to the (R,S)-syn-enantiomer. Due to the expeditiousness of production and inexpensive conditions developed, a series of alkyl- and aryl-substituted analogues of HPA-12 is also reported.

Cyanamidonitrate–copper(II) complexes of imidazole ligands: X-ray crystallography and physical investigation

Abstract New cyanamidonitrate–copper(II) complexes [Cu(NO2NCN)2Ln] (L=imidazole (iz), n=2; L=iz, 1-, 2- or 4-methylimidazole (meiz), n=4) have been isolated and characterised by IR, electronic and ESR spectroscopy. The crystal structures of 1- and 4-meiz complexes have been determined by X-ray crystallography; the structure of [Cu(NO2NCN)2(iz)2] is known (J. Kožisek, J.G. Diaz, M. Hvastijova, L. Jager, Acta Crystallogr., Sect. C 53 (1997) 703). The crystal structure of the first two compounds consists of [Cu(NO2NCN)2L4] units, in which the central CuII atoms are pseudo-octahedrally coordinated by six nitrogen atoms. Four of them, in equatorial planes, originate from meiz molecules and two, in axial positions, are nitrile nitrogens from the NO2NCN− anions. Influence of hydrogen bonds on equatorial–axial bond length correlation was ascertained. In the ESR spectra of the [Cu(NO2NCN)2L4] compounds copper hyperfine splitting is resolved. For all complexes, weak lines corresponding to the ΔMs=2 transitions appear. The spectrum of [Cu(NO2NCN)2(iz)4] in frozen methanolic solution shows 16-fold nitrogen splitting of the perpendicular band.

Spin crossover in a heptanuclear mixed-valence iron complex

The complex [Fe(II){(CN)Fe(III)L(5)}(6)]Cl(2) consists of a mixed-valence heptanuclear cyanide-bridged unit formed of a Schiff-base pentadentate ligand L(5) and it shows a spin crossover of the peripheral Fe(III) centres.

Synthesis, Crystal Structure, Spectroscopic Properties and Potential Biological Activities of Salicylate-Neocuproine Ternary Copper(II) Complexes

Mixed ligand copper(II) complexes containing derivatives of salicylic acid and heterocyclic ligands with nitrogen donor atoms have been the subject of various studies and reviews. In this paper, synthesis and characterization of the ternary copper(II) complexes of neocuproine (2,9-dimethyl-1,10-phenanthroline, Neo) and salicylate ligands (Sal) are reported. In addition, the crystal structures of ([Cu(H2O)(5-Cl-Sal)(Neo)] (1), [Cu(μ-Sal)(Neo)]2 (2), Cu2(μ-5-Cl-Sal)(5-Cl-HSal)2(Neo)2]·EtOH (3)) were determined. In order to compare structural and biological properties of the prepared complexes, spectroscopic and biological studies were performed. Results of X-ray diffraction show that prepared complexes form three types of crystal structures in a given system: monomeric, dimeric and dinuclear complex. The preliminary study on the DNA cleavage activity has shown that the complexes under study behave as the chemical nucleases in the presence of added hydrogen peroxide with slight differences in the activity (1 > 2 > 3). The complexes 1 and 2 exhibited nuclease activity itself indicating the interaction of complexes with the DNA. It has been proposed that the enhanced destructive effect of the complexes 1 and 2 on the DNA is a result of two possible mechanisms of action: (i) the conversion of closed circular DNA (form I) to the nicked DNA (form II) caused by the copper complex itself and (ii) damage of DNA by Reactive Oxygen Species (ROS)—products of the interaction of copper with hydrogen peroxide by means of Fenton reaction (hydroxyl radicals). Thus the biological activity of the prepared Cu(II) complexes containing derivatives of salicylic acid and phenanthroline molecules is substantiated by two independent mechanisms. While derivatives of salicylic acids in the coordination sphere of copper complexes are responsible for radical-scavenging activity (predominantly towards superoxide radical anion), the presence of chelating ligand 2,9-dimethyl-1,10-phenanthroline significantly enhances capability of Cu(II) complexes binding to DNA via intercalation.

Efficient total synthesis of (+)-dihydropinidine, (-)-epidihydropinidine, and (-)-pinidinone.

The 2,6-disubstituted piperidine alkaloids (+)-dihydropinidine (1), (-)-epidihydropinidine (2) (as HCl salts), and (-)-pinidinone (3) were efficiently synthesized from (S)-epichlorohydrin (7) as common substrate using regioselective Wacker-Tsuji oxidation of alkenylazides 10 and 14 as well as a highly diastereoselective reduction of cyclic imine 11 as key steps. The protecting group free total syntheses represent the up to date shortest routes with highest overall yields for all three naturally occurring alkaloids (1-3). The first single-crystal X-ray analysis of (-)-epidihydropinidine hydrochloride (2·HCl) confirmed its proposed absolute configuration to be (2S,6S), corresponding to that of the isolated natural product.

X-ray constrained unrestricted Hartree-Fock and Douglas-Kroll-Hess wavefunctions.

The extension of the X-ray constrained (XC) wavefunction approach to open-shell systems using the unrestricted Hartree-Fock formalism is reported. The XC method is also extended to include relativistic effects using the scalar second-order Douglas-Kroll-Hess approach. The relativistic effects on the charge and spin density on two model compounds containing the copper and iron atom are reported. The size of the relativistic effects is investigated in real and reciprocal space; in addition, picture-change effects are investigated and discussed for the isolated Cu atom. It is found that the relativistic terms lead to changes in the densities that are much smaller than those from the X-ray constraint. Nevertheless, the use of the relativistic corrections in the ab initio model always leads to an improvement in the agreement statistics. An interesting result of the unrestricted XC technique is the possibility of obtaining experimentally derived spin densities from X-ray data.

Syntheses, Electronic Structures, and EPR/UV−Vis−NIR Spectroelectrochemistry of Nickel(II), Copper(II), and Zinc(II) Complexes with a Tetradentate Ligand Based on S-Methylisothiosemicarbazide

Template condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde S-methylisothiosemicarbazone with pentane-2,4-dione and triethyl orthoformate at elevated temperatures resulted in metal complexes of the type M(II)L, where M = Ni and Cu and H(2)L = a novel tetradentate ligand. These complexes are relevant to the active site of the copper enzymes galactose oxidase and glyoxal oxidase. Demetalation of Ni(II)L with gaseous hydrogen chloride in chloroform afforded the metal-free ligand H(2)L. Then by the reaction of H(2)L with Zn(CH(3)COO)(2)·2H(2)O in a 1:1 molar ratio in 1:2 chloroform/methanol, the complex Zn(II)L(CH(3)OH) was prepared. The three metal complexes and the prepared ligand were characterized by spectroscopic methods (IR, UV-vis, and NMR spectroscopy), X-ray crystallography, and DFT calculations. Electrochemically generated one-electron oxidized metal complexes [NiL](+), [CuL](+), and [ZnL(CH(3)OH)](+) and the metal-free ligand cation radical [H(2)L](+•) were studied by EPR/UV-vis-NIR and DFT calculations. These studies demonstrated the interaction between the metal ion and the phenoxyl radical.

Structural, spectral and magnetic investigations of various types of compounds and their isomers isolated from the system copper(II)–C(CN)3––pyrazole

From the system CuII–C(CN)3––Hpz (Hpz = pyrazole) the following compounds were isolated: [Cu{C(CN)3}(Hpz)4][C(CN)3]1, [Cu{C(CN)3}2(Hpz)3]2, α-[Cu{C(CN)3}2(Hpz)2]3, β-[Cu{C(CN)3}2(Hpz)2]4 and [Cu{Hpz·C(CN)3}2]5. They were studied by the use of spectroscopic and cryomagnetic methods. The structures of 1 and 2 were refined to R values of 0.0369 and 0.0374 for 1346 and 2066 independent reflections respectively. Compound 1 crystallises in space group P21/c, with a= 9.568(4), b= 16.692(7), c= 14.957(9)A, β= 94.05(4)° and Z= 4; 2 crystallises in space group P, with a= 7.607(4), b= 8.942(6), c= 16.027(10)A, α= 95.95(6), β= 90.83(5), γ= 106.88(5)° and Z= 2. Both compounds show elongated pseudo-octahedral copper environments, with the Hpz molecules in the equatorial plane. In 1 one C(CN)3 group bridges the CuII atoms in axial positions while the second group is anionic. Compound 2 contains mono- as well as bi-dentate bridging C(CN)3 groups; the latter join the basic structure units into binuclear species. Weak ferromagnetic coupling operates between the copper(II) centres inside the dimers. Physical measurements show that compounds 3 and 4 display rhombic octahedral arrangements around CuII in which all C(CN)3 groups are bridging. The α and β compounds are distortion isomers. Compound 5, a coligand isomer with respect to 3 and 4, contains new anionic chelate ligands, HNC(pz)CH(CN)2–, formed by nucleophilic addition. In all these three compounds polymeric chains are present in which and between which there is magnetic interaction.

X-ray crystallographic and physical investigation of tricyanomethanide and dicyanamide complexes of cobalt(II) with imidazole and its methyl derivatives

SummaryReaction of CoII with N(CN)inf2sup− or C(CN)inf3sup− in the presence of imidazole (iz) or its methyl derivatives (2-meiz and 4-meiz) gave eight compounds of CoII: ligand stoichiometry 1∶2, including two isomeric pairs (α and β) for the complexes [Co{C(CN)3}2(2-meiz)2] and [Co{C(CN)3}2-(4-meiz)2]. The complexes were studied by electronic and i.r. spectroscopies. For α-[Co{C(CN)3}2(2-meiz)2] singlecrystal X-ray analysis was performed; its crystal structure consists of one-dimensional chains, formed by C(CN)inf3sup− anions bridging between the CoII atoms. The CoII atom is nearly octahedrally coordinated by two tertiary nitrogens of 2-meiz and four nitrogens of C(CN)inf3sup−. The spectra of these compounds and of the complexes with iz, as well as that of α-[Co{C(CN)3}2(4-meiz)2], indicate all these compounds to have basically the same bridging polymeric octahedral structure. However, the spectra indicate distorted tetrahedral structures for the remaining compounds.