Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands

The synthesis, spectroscopy, structures, and chemical reactivity of the organometallic complexes [(COD)­Pt­(CCR)₂] and [(COD)­Pt­(CCR)­(R′)] (COD = 1,5-cyclooctadiene, R = Ph, (Me)­Ph (2Me, 3Me, or 4Me), (NO₂)­Ph (2NO₂, 3NO₂, or 4NO₂), (4F)­Ph, (4OMe)­Ph, 2Py (2-pyridyl); R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl), NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored. The crystal structures reveal square-planar surroundings of the Pt atoms with short Pt–C­(alkynyl) bonds (<2 Å) and almost perpendicular orientation of the CC–aryl group to the Pt coordination plane. Nonattractive π–π stacking and C–H···F intermolecular interactions were observed in the crystal structures. Multinuclear (¹H, ¹³C, ¹⁹⁵Pt, and ¹⁹F) NMR spectroscopy reveals structures in solution and Pt–ligand bond strength. The thermal stability in organic solvents, the electrochemical stability, and the reactivity of the complexes in organic or aquatic (water-containing) solution toward the physiologically relevant species glutathione, chloride, and protons was tested, revealing remarkable stability or inertness of the complexes. Cytotoxicity experiments in HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines revealed highly promising activities for selected platinum alkynyl COD complexes

Interdependence of Structure, Morphology, and Phase Transitions in CVD Grown VO₂ and V₂O₃ Nanostructures

Phase selective chemical vapor deposition of nanostructured vanadium dioxide (VO₂) and sesquioxide (V₂O₃) was achieved by deploying [V­(O<i>R</i>)₄]_<i>n</i> (<i>R</i> = ^<i>t</i>Bu, <i>n</i> = 1 (<b>1</b>), <i>R</i> = Et, <i>n</i> = 3 (<b>2</b>), <i>R</i> = Me, <i>n</i> = 4 (<b>3</b>)). Use of [V­(O^<i>t</i>Bu)₄] (<b>1</b>) produced thin films of monoclinic VO₂ (M1) at 700 and 800 °C consisting of anisotropic nanostructures with high crystallinity and small hysteresis in the metal-to-semiconductor transition (MST). Film morphologies manifested strong dependence on growth temperatures and exhibited pronounced texturing effects at high temperatures (>700 °C). The microstructure of the films was found to significantly affect the MST behavior of VO₂ films. DTA measurements of VO₂ films showed MST at 63 °C (700 °C) and 65 °C (800 °C), much lower than the transition temperature observed in single crystal material (68 °C). Precursors were characterized in the solid state (XRD) and solution state (temperature dependent EPR, NMR) to reveal an association–dissociation equilibrium in solution (complexes <b>2</b> and <b>3</b>), involving monomeric, dimeric, and oligomeric species. Use of <b>2</b> and <b>3</b> as single precursors produced thin films of crystalline V₂O₃ consisting of nanosheets (5 nm) with a flower-like morphology

Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands

The synthesis, spectroscopy, structures, and chemical reactivity of the organometallic complexes [(COD)­Pt­(CCR)₂] and [(COD)­Pt­(CCR)­(R′)] (COD = 1,5-cyclooctadiene, R = Ph, (Me)­Ph (2Me, 3Me, or 4Me), (NO₂)­Ph (2NO₂, 3NO₂, or 4NO₂), (4F)­Ph, (4OMe)­Ph, 2Py (2-pyridyl); R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl), NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored. The crystal structures reveal square-planar surroundings of the Pt atoms with short Pt–C­(alkynyl) bonds (<2 Å) and almost perpendicular orientation of the CC–aryl group to the Pt coordination plane. Nonattractive π–π stacking and C–H···F intermolecular interactions were observed in the crystal structures. Multinuclear (¹H, ¹³C, ¹⁹⁵Pt, and ¹⁹F) NMR spectroscopy reveals structures in solution and Pt–ligand bond strength. The thermal stability in organic solvents, the electrochemical stability, and the reactivity of the complexes in organic or aquatic (water-containing) solution toward the physiologically relevant species glutathione, chloride, and protons was tested, revealing remarkable stability or inertness of the complexes. Cytotoxicity experiments in HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines revealed highly promising activities for selected platinum alkynyl COD complexes

Linear Bis(perfluoroalkyl) Complexes of Nickel Bipyridine

Three new complexes were prepared: [(dtbpy)­Ni­(CF₃)₂] (<b>1</b>), [(dtbpy)­Ni­(CF₂CF₃)₂] (<b>2</b>), and [(dtbpy)­Ni­(CH₃)₂] (<b>3</b>) (dtbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine). Remarkable differences in the structure, electronics, reactivity, and absorption of visible light for the alkyl versus perfluoroalkyl complexes were observed and are detailed in this report

Nitrogen–Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform

The nickel-C₄F₈ fragment coordinates an aminoaryl N–H ketimine to form a stable complex, which upon treatment with base and oxidant leads to an N–N bond-forming reaction and the release of indazole product. A key and previously unidentified intermediate in the formation of the indazole was a diimine complex of nickel bearing significant charge on the aryl ring that initially contained the amine substituent. The C₄F₈ coligand was key for the redox transformation and for stabilization of the intermediate for characterization

CdS Nanoparticles Fabricated from the Single-Source Precursor [Cd{Et₂NC(S)NP(S)(O<i>i</i>Pr)₂}₂]: In Depth Experimental and Theoretical Studies

Reaction of the diethylammonium salt of <i>N</i>-thiophosphorylated thioureate [Et₂NC­(S)­NP­(S)­(O<i>i</i>Pr)₂]⁻ (<b>L</b>^<b>–</b>) with CdCl₂ in aqueous ethanol leads to the complex <b>[CdL</b>_<b>2</b><b>]</b>. The compound crystallizes in the triclinic space group <i>P</i>1̅ with <i>Z</i> = 2 and the metal cation is found in a tetrahedral <i>S</i>₂<i>S</i>′₂ coordination environment formed by the C–S and P–S sulfur atoms. The Hirshfeld surface analysis showed that the structure of <b>[CdL</b>_<b>2</b><b>]</b> is dominated by H···H, S···H, and O···H contacts. According to charge and energy decomposition scheme ETS-NOCV, topological noncovalent index (NCI) and quantum theory of atoms in molecules (QTAIM) calculations, both inter- and intramolecular noncovalent C–H···S and C–H···H–C interactions are the main factors that stabilize <b>[CdL</b>_<b>2</b><b>]</b>. Calculated NMR data, based on the GIAO approach, are in very good agreement with experimental data. The complex <b>[CdL</b>_<b>2</b><b>]</b> is an efficient single-source precursor for the formation of TOPO-capped CdS nanoparticles of about 5 nm diameter with wurtzite structure (TOPO = tri-<i>n</i>-octylphosphine oxide). Their growth was monitored over a period of time by means of UV–vis spectroscopy. From ETS-NOCV modeling, the TOPO molecules were found to strongly adhere to the CdS nanoparticles through dative-covalent Cd–O bonds as well as through secondary noncovalent C–H···Cd and C–H···S interactions. The characteristic band edge luminescence was observed in the emission spectra of all samples. The TEM microscopy showed well-dispersed spherical CdS nanoparticles; the composition was supported by EDX

Unsymmetrical <i>N</i>‑Aryl-1-(pyridin-2-yl)methanimine Ligands in Organonickel(II) Complexes: More Than a Blend of 2,2′-Bipyridine and <i>N</i>,<i>N</i>‑Diaryl-α-diimines?

The new organonickel complexes [(R-PyMA)­Ni­(Mes)­X] [R-PyMA = <i>N</i>-aryl-1-(pyridin-2-yl)­methanimine; aryl = phenyl, 2,6-Me₂-, 3,5-Me₂-, 2,4,6-Me₃-, 2,6-^<i>i</i>Pr₂-, 3,5-(OMe)₂-, 2-NO₂-4-Me-, 4-NO₂-, 2-CF₃-, and 2-CF₃-6-F-phenyl; Mes = 2,4,6-trimethylphenyl; X = F, Cl, Br, or I] were obtained as approximate 1/1 cis and trans isomeric mixtures or pure cis isomers depending on the PyMA ligand and X. The [(R-PyMA)­Ni­(Mes)­X] complexes with X = Br or Cl were directly synthesized from the precursors <i>trans</i>-[(PPh₃)₂Ni­(Mes)­X], while [(PyMA)­Ni­(Mes)­X] derivatives with X = F or I were obtained from [(PyMA)­Ni­(Mes)­Br] through X exchange reactions. Although density functional theory (DFT) calculations show a preference for the sterically favored cis isomers, both isomers could be observed in many cases; in three cases, even single crystals for X-ray diffraction could be obtained for the trans isomers. Possible intermediates for the isomerization were investigated by DFT calculations. All complexes were studied by multiple spectroscopic means, electrochemistry, and spectroelectrochemistry (for the reduction processes). The long-wavelength metal-to-ligand charge-transfer (MLCT) absorptions vary markedly with the R substituent of the ligand and the cathodic electrochemical potentials to a far smaller degree. Both are almost invariable upon variation of X. All of this is in line with Ni-based and π*-based lowest unoccupied molecular orbitals (LUMOs). In line with the unsymmetric character of the N_Py^N_methanimine ligand, electrochemistry and MLCT transitions seem to not correspond to the same type of π* LUMO, making these PyMA ligands more interesting than the symmetric heteroaromatic polypyridine ligands such as 2,2′-bipyridine (bpy; N_Py^N_Py) and <i>N</i>,<i>N</i>-diaryl-substituted aliphatic α-diimines (N_methanimine^N_methanimine) such as the diaza-1,3-butadienes (DAB). First attempts to use these complexes in Negishi-type cross-coupling reactions were successful

A Five-Coordinate Nickel(II) Fluoroalkyl Complex as a Precursor to a Spectroscopically Detectable Ni(III) Species

Mechanistic proposals for nickel-catalyzed coupling reactions often invoke five-coordinate alkyl- or aryl-bound Ni­(II) and/or high-valent nickel­(III) species, but because of their reactive nature, they have been difficult to study and fingerprint. In this work, we invoked the stabilizing properties of fluoroalkyl ligands to access such nickel species bearing ligands that are commonplace in organic coupling reactions. We show that five-coordinate Ni­(II) complexes containing nickel–carbon bonds can readily be prepared given the appropriate precursor, and we also present evidence for the formation of Ni­(III) species upon chemical and electrochemical oxidation of the five-coordinate complexes