Peter C. Kunz

Metal carbonyls supported on iron oxide nanoparticles to trigger the CO-gasotransmitter release by magnetic heating

Magnetic iron oxide, maghemite (Fe2O3) nanoparticles with covalent surface-bound CO-releasing molecules (CORMs) can be triggered to release CO through heating in an alternating magnetic field. In the proof-of-concept study the rate of CO-release from [RuCl(CO3)(μ-DOPA)]@maghemite nanoparticles was doubled upon exposure to an external alternating magnetic field (31.7 kAm(-1), 247 kHz, 25 °C, 39.9 mTesla, DOPA = dioxyphenyl-alaninato).

Gold(I) complexes of water-soluble diphos-type ligands: Synthesis, anticancer activity, apoptosis and thioredoxin reductase inhibition

Gold(I) complexes of imidazole and thiazole-based diphos type ligands were prepared and their potential as chemotherapeutics investigated. Depending on the ligands employed and the reaction conditions complexes [L(AuCl)(2)] and [L(2)Au]X (X = Cl, PF(6)) are obtained. The ligands used are diphosphanes with azoyl substituents R(2)P(CH(2))(2)PR(2) {R = 1-methylimidazol-2-yl (1), 1-methylbenzimidazol-2-yl (4), thiazol-2-yl (5) and benzthiazol-2-yl (6)} as well as the novel ligands RPhP(CH(2))(2)PRPh {R = 1-methylimidazol-2-yl (3)} and R(2)P(CH(2))(3)PR(2) {R = 1-methylimidazol-2-yl (2)}. The cytotoxic activity of the complexes was assessed against three human cancer cell lines and a rat hepatoma cell line and correlated to the lipophilicity of the compounds. The tetrahedral gold complexes [(3)(2)Au]PF(6) and [(5)(2)Au]PF(6) with intermediate lipophilicity (logD(7.4) = 0.21 and 0.25) showed significant cytotoxic activity in different cell lines. Both compounds induce apoptosis and inhibit the enzymes thioredoxin reductase and glutathione reductase.

CO-releasing molecule (CORM) conjugate systems

The development of CORMs (CO-releasing molecules) as a prodrug for CO administration in living organisms has attracted significant attention. CORMs offer the promising possibility of a safe and controllable release of CO in low amounts triggered by light, ligands, enzymes, etc. For the targeting of specific tissues or diseases and to prevent possible side effects from metals and other residues after CO release, these CORMs are attached to biocompatible systems, like peptides, polymers, nanoparticles, dendrimers, protein cages, non-wovens, tablets, and metal-organic frameworks. We discuss in this review the known CORM carrier conjugates, in short CORM conjugates, with covalently-bound or incorporated CORMs for medicinal and therapeutic applications. Most conjugates are nontoxic, show increasing half-lives of CO release, and make use of the EPR-effect, but still show problems because of a continuous background of CO release and the absence of an on/off-switch for the CO release.

Gold(I) Catalysts with Bifunctional P, N Ligands

A series of phosphanes with imidazolyl substituents were prepared as hemilabile PN ligands. The corresponding gold(I) complexes were tested as bifunctional catalysts in the Markovnikov hydration of 1-octyne, as well as in the synthesis of propargylamines by the three component coupling reaction of piperidine, benzaldehyde, and phenylacetylene. While the activity in the hydration of 1-octyne was low, the complexes are potent catalysts for the three component coupling reaction. In homogeneous solution the conversions to the respective propargylamine were considerably higher than under aqueous biphasic conditions. The connectivity of the imidazolyl substituents to the phosphorus atom, their substitution pattern, as well as the number of heteroaromatic substituents have pronounced effects on the catalytic activity of the corresponding gold(I) complexes. Furthermore, formation of polymetallic species with Au(2), Au(3), and Au(4) units has been observed and the solid-state structures of the compounds [(5)(2)Au(3)Cl(2)]Cl and [(3c)(2)Au(4)Cl(2)]Cl(2) (3c = tris(2-isopropylimidazol-4(5)-yl phosphane, 5 = 2-tert-butylimidazol-4(5)-yldiphenyl phosphane) were determined. The gold(I) complexes of imidazol-2-yl phosphane ligands proved to be a novel source for bis(NHC)gold(I) complexes (NHC = N-heterocyclic carbene).

Is the 1 J PSe Coupling Constant a Reliable Probe for the Basicity of Phosphines? A 31P NMR Study

Abstract The influence of different heteroaryl and functionalized aryl substituents on the electron-donating ability and basicity of the phosphorus atoms in heteroaryl phosphines and diphosphines has been determined by the use of the direct 1JPSe coupling constants of the corresponding selenides. The generality of the use of 31P–77Se spin–spin coupling constants as probe for the basicity of phosphines is discussed as well as the scope and limits of this concept. GRAPHICAL ABSTRACT

(Picolinato-κ2N,O)[tris(2-isopropyl-1H-imidazol-4-yl-κN3)phosphane]cobalt(II) nitrate

Single crystals of the title compound, [Co(C6H4NO2)(C18H27N6P)]NO3, were obtained from the reaction of nitrato[tris(2-isopropylimidazol-4-yl)phosphane]cobalt(II) nitrate with picolinic acid in the presence of potassium tert-butoxide as base. The coordination polyhedron around the central CoII ion is about halfway between square-pyramidal and trigonal-bipyramidal geometry. In the structure, the nitrate counter-anion is connected by N—H⋯O hydrogen bonding to the complex cation. Additionally, the complex cations form one-dimensional chains along [010] by hydrogen bonding of the NH group of an imidazole ring to the picolinate group of a neighbouring complex cation.

A new crystal modification of diammonium hydrogen phosphate, (NH4)2(HPO4)

The addition of hexafluoridophosphate salts (ammonium, silver, thallium or potassium) is usually used to precipitate complex cations from aqueous solutions. It has long been known that PF6 − is sensitive towards hydrolysis under acidic conditions [Gebala & Jones (1969 ▶). J. Inorg. Nucl. Chem. 31, 771–776; Plakhotnyk et al. (2005 ▶). J. Fluorine Chem. 126, 27–31]. During the course of our investigation into coinage metal complexes of diphosphine ligands, we used ammonium hexafluoridophosphate in order to crystallize [Ag(diphosphine)2]PF6 complexes. From these solutions we always obtained needle-like crystals which turned out to be the title compound, 2NH4 +·HPO4 2−. It was received as the hydrolysis product of NH4PF6. The crystals are a new modification of diammonium hydrogen phosphate. In contrast to the previously published polymorph [Khan et al. (1972 ▶). Acta Cryst. B28, 2065–2069], Z′ of the title compound is 2. In the new modification of the title compound, there are eight molecules of (NH4)2(HPO4) in the unit cell. The structure consists of PO3OH and NH4 tetrahedra, held together by O—H⋯O and N—H⋯O hydrogen bonds.

The betainic form of (imidazol-2-yl)phenylphosphinic acid hydrate.

Single crystals of the title compound, (imidazolium-2-yl)phenylphosphinate monohydrate, C9H9N2O2·H2O, were obtained from methanol/water after deprotection and oxidation of bis(1-diethoxymethylimidazol-2-yl)phenylphosphane. In the structure, several N–H⋯O and P—O⋯H–O hydrogen bonds are found. π–π interactions between the protonated imidazolyl rings [centroid–centroid distance = 3.977 (2) Å] help to establish the crystal packing. The hydrate water molecule builds hydrogen bridges to three molecules of the phosphinic acid by the O and both H atoms.

Tricarbonyl[tris(1-methyl-1H-imidazol-2-yl-κN3)methanol]manganese(I) trifluoromethanesulfonate

In the title compound, [Mn(C13H16N6O)(CO)3](CF3O3S), the MnI atom has a slightly distorted octahedral geometry. The three CO ligands have C—Mn—C angles in the range 89.44 (10)–92.31 (9)°, while the three N atoms of the tripodal ligand form significantly smaller N—Mn—N angles of 82.76 (2)–85.51 (6)°. The three N atoms of the tripodal ligand and the three carbonyl ligands coordinate facially. In the crystal, the trifluoromethanesulfonate counter anion is connected by a medium-strength O—H⋯O hydrogen bond to the hydroxyl group of the manganese complex.