A novel, potent, and selective antitumor agent, namely (E)-3-phenyl-1-(2-pyridinyl)-2-propen-1-one 4,4-dimethyl-3-thiosemicarbazone (PPP44mT), and its analogues were synthesized and characterized and displayed strikingly distinctive properties. This activity was mediated by the inclusion of a styrene moiety, which through steric and electrochemical mechanisms prevented deleterious oxy-myoglobin or oxy-hemoglobin oxidation relative to other potent thiosemicarbazones, i.e., di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) or di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). Structure−activity relationship analysis demonstrated specific tuning of PPP44mT electrochemistry further inhibited oxy-myoglobin or oxy-hemoglobin oxidation. Both PPP44mT and its Cu(II) complexes showed conspicuous almost immediate cytotoxicity against SK-N-MC tumor cells (within 3 h). In contrast, [Zn(PPP44mT) 2 ] demonstrated a pronounced delay in activity, taking 48 h before marked antiproliferative efficacy was apparent. As such, [Zn(PPP44mT) 2 ] was designated as a "stealth Zn(II) complex" that overcomes the near immediate cytotoxicity of PPP44mT or its copper complexes. Upon examination of the suppression of oncogenic signaling, [Zn(PPP44mT) 2 ] was superior at inhibiting cyclin D1 expression compared to DpC or Dp44mT.

A novel type of water-soluble anionic cubic cages K 4 [{Co III (Me 3-Tacn)} 4 {Fe II (CN) 6 } 4 ] and Na 4 [{Co III (Me 3-Tacn)} 4 {Fe II (CN) 6 } 4 ] were prepared by means of a mechanistically designed selfassembly process between [Co(Me 3-Tacn)Cl 3 ] and M 4 [Fe II (CN) 6 ] for M = Na or K, respectively; consisting on a rate limiting outer-sphere redox step followed by a fast substitution/inner-sphere redox reaction sequence. These compounds show a remarkable stability in aqueous solution at different pH ranges, displaying neat protonation processes and a reversible oxidation with peroxodisulfate to its neutral {Fe III 4 Co III 4 } form. Furthermore, the cages behave as a robust and water-soluble molecular PrussianBlueAnalog capable of encapsulating {Na-OH 2 } + pairs and K + cations in aqueous solution, where the cubic structure of the complex is preserved. The substitution of the {Na-OH 2 } + pairs by K + is easily accomplished, and the electrochemical properties of the sodium and potassium salts of the new cages have been found dramatically dependent on the encapsulated units.

Air oxidation of methanolic solutions of biologically active tridentate pyridyl thiosemicarbazone (TSC) complexes of the general formula [Fe(TSC)] has been studied at varying dioxygen concentrations, temperatures, and pressures. The data collected indicate that the activation entropy of the reaction increases linearly with the redox potential of the complexes in a more definite way than the activation enthalpy. However, a very distinct behavior is observed for the values of the activation volumes, which do not follow the expected entropy-volume parallel trend for all of the systems studied. The involvement of important interactions between the terminal NH groups of the coordinated TSC ligand and molecular dioxygen has been found to be significant by measurements carried out at varying hydrostatic pressures. Kinetic experiments run on analogous N-deuterated complexes confirm the importance of these noncovalent interactions, which are weaker for the less acidic ND groups. These interactions show the existence of an ordering/expansion process upon going from the reactants to the transition state, whenever an interaction between the polar terminal amino groups and dioxygen can be established.

Organocopper(II) complexes are a rarity while organocopper(I) complexes are commonplace in chemical synthesis. In the course of building a strategy to generate organocopper(II) species utilizing electrochemistry, a method to form...

The rare organocopper­(II) complex [Cu­(Me6tren)­(CH2CN)]+ (Me6tren = tris­(2-(dimethylamino)­ethyl)­amine) has emerged as an important model of potential byproducts in copper-catalyzed atom transfer radical polymerization. This complex has been generated by controlled potential electrolysis of [Cu­(Me6tren)­(NCMe)]2+ in the presence of BrCH2CN. Time-resolved UV–vis and continuous wave and pulse electron paramagnetic resonance (EPR) spectra identified [Cu­(Me6tren)­Br]+ as an intermediate. Hyperfine sublevel correlation and electron nuclear double resonance spectroscopy of samples at different timepoints reveal signals that are assigned to a C-bound cyanomethylate ligand, with distinct 14N and 1H hyperfine coupling constants in comparison with the corresponding N-bound acetonitrile and bromido complexes. The experimental EPR data are supported by density functional theory calculations to understand how the geometries of the species involved produce distinct spectroscopic signatures, and a clear picture of how this unusual organocopper­(II) complex is formed has emerged.