Inorganica Chimica Acta

Cu(III)2 (μ-O)2 bis-oxides ( O ) form spontaneously by direct oxygenation of nitrogen-chelated Cu(I) species and constitute a diverse class of versatile 2e- /2H+ oxidants, but while these species have attracted attention as biomimetic models for dinuclear Cu enzymes, reactivity is typically limited to intramolecular ligand oxidation, and systems exhibiting synthetically useful reactivity with exogenous substrates are limited. O tmpd (TMPD = N 1 , N 1 , N 3 , N 3 -tetramethylpropane-1,3-diamine) presents an exception, readily oxidizing a diverse array of exogenous substrates, including primary alcohols and amines selectively over their secondary counterparts in good yields...

Ligands that coordinate via dianionic phosphonate groups have not been widely utilized in radiopharmaceuticals. N -(phosphonomethyl)iminodiacetic acid ( 1 , PMIDA) and N- (phosphonomethyl)glycine ( 2 , PMG) were investigated as new chelators for the 99m Tc/Re-tricarbonyl "core" ( fac -M(CO)3 , M = 99m Tc, Re) present in a major class of radiopharmaceuticals. fac-M(CO)3 (PMIDA) and fac-M(CO)3 (PMG) complexes were studied by HPLC and 1 H/13 C/31 P NMR methods for M = Re ( Re-1 and Re-2 ) and by HPLC for M = 99m Tc ( 99m Tc-1 and 99m Tc-2 )...

The copper coordination chemistry of two multidentate carboxamido ligands derived from HL1 (offering two quinolyl and one carboxamide donor) and H4 L2 (with two pyridine(dicarboxamido) units linked by naphthalene spacers) was explored. The former was chosen because upon deprotonation it would provide a monoanionic mer -coordinating N-donor set that would model the putative deprotonated form of the His-brace in copper monooxygenases, while the latter was designed to bind two copper ions and enable comparisons to other systems with different ligand spacers...

Investigations of small molecule copper-dioxygen chemistry can and have provided fundamental insights into enzymatic processes (e.g., copper metalloenzyme dioxygen binding geometries and their associated spectroscopy and substrate reactivity). Strategically designing copper-binding ligands has allowed for insight into properties that favor specific (di)copper-dioxygen species. Herein, the tetradentate tripodal TMPA-based ligand (TMPA = tris((2-pyridyl)methyl)amine) possessing a methoxy moiety in the 6-pyridyl position on one arm (OCH3 TMPA) was investigated...

The tetradentate mixed imino/amino phenoxide ligand (N-(3,5-di-tert-butylsalicylidene)-N'-(2-hydroxyl-3,5-di-tert-butylbenzyl))-trans-1,2-cyclohexanediamine (salalen) was complexed with CuII , and the resulting Cu complex ( 2 ) was characterized by a number of experimental techniques and theoretical calculations. Two quasi-reversible redox processes for 2 , as observed by cyclic voltammetry, demonstrated the potential stability of oxidized forms, and also the increased electron-donating ability of the salalen ligand in comparison to the salen analogue...

Chemical tools are needed to discover new effective drugs for tackling multifaceted complex neurodegenerative diseases like Alzheimer's disease (AD). Multifunctional nature of two compounds, 5-((4-nitro-phenyl)diazenyl)quinolin-8-ol (HL1) and 4-((4-nitrophenyl)diazenyl)benzene-1,3-diol (HL2) is reported w.r.t. their ability to bind Cu2+ ions and amyloid aggregates related to AD. HL1 and HL2 have half congo-red type azo-stilbene structural framework incorporated with metal chelating groups, designed to chelate metal ions from metal-amyloid species...

A new near-infrared fluorescent probe (NIR-PbP) for sensitive detection of Pb(II) ions in solution and living cells has been rationally designed and synthesized. The NIR-PbP is inherently non-fluorescent and gains fluorescence in the presence Pb(II) ions. The ion detection is based on Pb(II)-induced unmasking the fluorophore through the opening of the spyrocycle, with more than 500-fold fluorescence for sub-micromolar Pb(II) concentration. The NIR-PbP has high sensitivity, good photo-stability, low detection limit, and reversible response to Pb(II) ions...

A novel series of ferrocenyl chalcone ammonium and pyridinium salt derivatives were synthesized in order to improve their solubility in aqueous media. Substituted ferrocenyl chalcones with amines and pyridines were synthesized using the base-catalyzed Claisen-Schmidt reaction, and their corresponding salts were prepared by a nucleophilic quaternization reaction at the nitrogen atom. Most of the synthesized ferrocenyl chalcone salts were soluble in water at room temperature. They were fully characterized by IR, NMR spectroscopy and HRMS spectrometry, and their electrochemistry was studied...

The enantioselective synthesis of polypropionates continues to be an attractive realm for the synthetic chemists mostly due to the challenges presented by the number of consecutive stereogenic centers contained within the aliphatic chain. Over the years, our laboratory has developed an epoxide-based three-step reiterative methodology for the construction of these targets, with the ultimate goal that the approach could be extended to the synthesis of polypropionate-containing natural products. The key steps include the diastereoselective epoxidation of allylic and homoallylic alcohols, and the regioselective cleavage of 2-methyl-3,4-epoxy alcohols...

Guanosine and related derivatives self-assemble in the presence of cations like potassium into supramolecular G-quadruplexes (SGQs), where four guanine moieties form planar tetrads (T) that coaxially stack into columnar aggregates with broad size distributions. However, SGQs made from 8-aryl-2'-deoxyguanosine derivatives (8ArGs), form mostly octamers, or two-tetrad ( 2 T)-SGQs, while some form dodecamers ( 3 T-SGQs), or hexadecamers ( 4 T-SGQs), and none reported to date form higher assemblies. A theoretical model that addresses the configurational space available for the multiple pathways available for 8ArGs to self-assemble into SGQs is used to frame a series of molecular dynamics simulations (MDS) with selected SGQs...

We report the synthesis and characterization of new ruthenium(II) and iridium(III) complexes of a new bidentate chelate, NHCR' -pyOR (OR = OMe, OtBu, OH and R' = Me, Et). Synthesis and characterization studies were done on the following compounds: four ligand precursors (1-4); two silver complexes of these NHCR' -pyOR ligands (5-7); six ruthenium complexes of the type [η6 -(p-cymene)Ru(NHCR' -pyOR )Cl]X with R' = Me, Et and R = Me, tBu, H and X = OTf- , PF6 - and PO2 F2 - (8-13); and two iridium complexes, [Cp*Ir(NHCMe -pyOtBu )Cl]PF6 (14) and [Cp*Ir(NHCMe -pyOH )Cl]PO2 F2 (15)...

A new iron(II) complex has been prepared and characterized. [Fe(TrImA)2 (OTf)2 ] ( 1 , TrImA = 1-Tritylimidazole-4-carboxaldehyde). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in monoclinic space group P 21 / c , with a = 10.8323(18) Å, b = 8.1606(13) Å and c = 24.818(4) Å. The iron center is coordinated to two imidazole groups, two pendant aldehyde-derived carbonyl oxygens and two triflate oxygens. The complex is high spin between 300 and 20 K as indicated by variable field variable temperature magnetic measurements...

A new Rh2 (II,II) complex containing one dppn (benzo[ i ]dipyrido[3,2- a :2,3- c ]phenazine) ligand with an extended π-system, cis -H,H-[Rh2 (OCCH3 NH)2 (dppn)(CH3 CN)2 ]2+ ( 2 ), was synthesized and characterized. The dppn ligand, which serves as a DNA base pair intercalator, chelates to a single Rh center and is positioned trans to the amidato N atoms of the bridging acetamide ligand. This ligand also possesses a low-lying dppn-centered 3 ππ* state that is advantageous for the sensitization of singlet oxygen (1 O2 ), which complex 2 produced with a quantum yield, Φ 1 O2 460 , of 0...

The kinetics and mechanism of the oxidation of [Co(dmgBF2 )2 (OH2 )2 ] (where dmgBF2 = difluoroboryldimethylglyoximato) by sodium hypochlorite (NaOCl) were investigated by stopped-flow spectrophotometry at 450 nm over the temperature range of 10 °C ≤ θ ≤ 25 °C, pH range of 5.0 ≤ pH ≤ 7.8, and at an ionic strength of 0.60 M (NaCl). The pKa1 value for [Co(dmgBF2 )2 (H2 O)2 ] was calculated as 5.27 ± 0.14 at I = 0.60 (NaCl). The redox process was dependent on pH and oxidant concentration in a complex manner, that is, kobs = ((k2 [H+ ] + k1 Ka )/([H+ ] + Ka ))[OCl- ]T , where at 25...

This article is a short review that presents a short review of photosubstitution reactions of Ru(II) imine complexes and illustrates their use in the development of therapeutic agents. The review begins with an overview of the photophysical behavior and common photoreactions of Ru(II) imine complexes, with select examples from the literature since the 1960s. It is followed by a more detailed picture of the application of knowledge gained over the years in the development of Ru(II) complexes for photobiology and photodynamic therapy...

H2 -evolution assays, plus EPR and FTIR spectroscopies, using CO-inhibited Azotobacter vinelandii Mo-nitrogenase have shown that the disaccharide trehalose is an effective quenching agent of enzymatic turnover and also stabilizes the reaction intermediates formed. Complete inhibition of H2 -evolution activity was achieved at 1.5 M trehalose, which compares favorably to the requirement for 10 M ethylene glycol to achieve similar inhibition. Reaction-intermediate stabilization was demonstrated by monitoring the EPR spectrum of the 'hi-CO' form of CO-inhibited N2 ase, which did not change during 1 hr after trehalose quenching...

The cellular response evoked by a hexanuclear platinum complex, Pt6L4 (1), is reported. Compound 1, a 3-nm octahedral cage formed by self-assembly of six Pt(II) centers and four 2,4,6-tris(4-pyridyl)-1,3,5-triazine ligands (L), exhibits promising in vitro potency against a panel of human cancer cell lines. Unlike classical platinum-based anticancer agents, 1 interacts with DNA in a non-covalent, intercalative manner and promotes DNA condensation. In cancer cells, 1 induces DNA damage, upregulates p53, its phosphorylated form phospho-p53 and its downstream effector, p21, as well as both apoptosis and senescence...

DNA has been exploited as a biological target of chemotherapeutics since the 1940s. Traditional chemotherapeutics, such as cisplatin and DNA-alkylating agents, rely primarily on increased uptake by rapidly proliferating cancer cells for therapeutic effects, but this strategy can result in off-target toxicity in healthy tissue. Recently, research interests have shifted towards targeted chemotherapeutics, in which a drug targets a specific biological signature of cancer, resulting in selective toxicity towards cancerous cells...

This review summarizes research into the metal-binding properties of catalytic DNAzymes, towards the goal of understanding the structural properties leading to metal ion specificity. Progress made and insight gained from a range of biochemical and biophysical techniques are covered, and promising directions for future investigations are discussed.

Mixed amine/ammine motifs are important features in newer generation platinum anticancer agents, including the Pt(IV) prodrug satraplatin. One synthetic route that can be used to access platinum molecules with such structures exploits the trans effect during NH3-mediated cleavage of iodo-bridged platinum(II) dimers of the form [Pt(Am)I(μ-I)]2, where Am is an amine. A clear picture of the nature of these dimers that is consistent with the reactivity they exhibit has remained elusive. Moreover, technical aspects of this chemistry have impeded its more widespread use...