One-step synthesis and characterization of difunctionalized N-confused tetraphenylporphyrins

Three disubstituted N-confused porphyrins (2-4) were prepared in ca. 4% yield using a one-pot synthesis. These porphyrins bear 3,5-di-tert-butylphenyl groups substituted at the C(5) and C(20) meso positions and para-substituted (Br, NO(2), ethynyl) phenyl groups at the C(10) and C(15) meso positions. The specific orientation of the aryl rings around the macrocycle in porphyrin 2 was definitively determined using a combination of 1D ((1)H and (13)C) and 2D (gHMQC and gHMBC) NMR spectroscopy. The absorption spectra of 2-4 in CH(2)Cl(2) and dimethylacetamide are similar to those of N-confused tetraphenylporphyrin in the same solvents but have Soret and Q-bands that are shifted to lower energies. Steady-state fluorescence measurements revealed Q(x)(0,0) and Q(x)(0,1) bands similar in energy to the unsubstituted NCPs 1i and 1e. The fluorescence quantum yield results for two of these NCPs (2, 4) are atypical of porphyrin behavior and are being further investigated by time-resolved spectroscopy.     

Synthesis and magnetic properties of Gd doped EuS nanocrystals with enhanced Curie temperatures

EuS nanocrystals (NCs) were doped with Gd resulting in an enhancement of their magnetic properties. New EuS and GdS single source precursors (SSPs) were synthesized, characterized, and employed to synthesize Eu(1-x)Gd(x)S NCs by decomposition in oleylamine and trioctylphosphine at 290 °C. The doped NCs were characterized using X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, which support the uniform distribution of Gd dopants through electron energy loss spectroscopy (EELS) mapping. X-ray absorption spectroscopy (XAS) revealed the dopant ions in Eu(1-x)Gd(x)S NCs to be predominantly Gd(3+). NCs with a variety of doping ratios of Gd (0 ≤ x < 1) were systematically studied using vibrating sample magnetometry and the observed magnetic properties were correlated with the Gd doping levels (x) as quantified with ICP-AES. Enhancement of the Curie temperature (T(C)) was observed for samples with low Gd concentrations (x ≤ 10%) with a maximum T(C) of 29.4 K observed for NCs containing 5.3% Gd. Overall, the observed T(C), Weiss temperature (θ), and hysteretic behavior correspond directly to the doping level in Eu(1-x)Gd(x)S NCs and the trends qualitatively follow those previously reported for bulk and thin film samples.     

Synthesis,characterization, duplex-DNA interactions,and anticancer activities of novel octahedral [Ni(phen)2(dppz-idzo)]2+ and [Co(phen)2(dppz-idzo)]3+ complexes

Two new octahedral [Ni(phen)₂(dppz-idzo)]²⁺ and [Co(phen)₂(dppz-idzo)]³⁺ complexes have been synthesized and characterized by CHN analysis, electrospray ionization-MS, nuclear magnetic resonance, and UV–Vis spectra. The DNA-binding ability of these complexes was spectrophotometrically, hydrodynamically, and electrophoretically evaluated which indicated that they strongly intercalate into the DNA double helix, and that both induced severe DNA damage in the presence of peroxide. The complexes also showed strong antiproliferative effect against HepG2 and MDA-MB-231 cells. By contrast, they were found to be inactive against the MCF-7 cell line. The ligand itself was found to be inactive against the cells tested.     

Cyan-Blue Luminescence and Antiferromagnetic Coupling of CN-Bridged Tetranuclear Complex Based on Manganese(III) Schiff Base and Hexacyanoferrate(III)

A new tetranuclear cyanide-bridged Mn^III–Fe^III complex based on manganese(III) Schiff base and hexacyanoferrate(III) units, [Mn(L)(MeOH)₂][{Mn(L)}{Fe(CN)₆}{Mn(L)(MeOH)}].2MeOH, [H₂L?=?N,N′-bis(2-hydroxy-1-naphthalidenato)-1,2-diaminopropane] (1), has been synthesized and characterized by elemental analysis, UV–Vis, FT-IR, PXRD, single crystal X-ray analyses, magnetic and photoluminescence measurements. Complex 1 consist of one trinuclear cyanido-bridged anion, in which [Fe(CN)₆]^3? anion bridge [Mn(L)]⁺ and Mn(L)(MeOH)}]⁺ cations via two C≡N groups in the cis positions, and also one isolated manganese [Mn(L)(MeOH)₂]⁺ cation. DC magnetic susceptibility and magnetization studies showed that complex 1 indicates an antiferromagnetic coupling between low-spin Fe(III) and high-spin Mn(III) through the cyanide bridges. In addition, the complex 1 displays a strong cyan-blue luminescence emission in the solid state condition at room temperature. This behavior might be seen easily from the chromaticity diagram. Thus, the complex may be a good promising cyan-blue OLED developing electroluminescent materials for flatted or curved panel display applications due to the fact that it has such features.     

Modifying the Steric Properties in the Second Coordination Sphere of Designed Peptides Leads to Enhancement of Nitrite Reductase Activity

Protein design is a useful strategy to interrogate the protein structure‐function relationship. We demonstrate using a highly modular 3‐stranded coiled coil (TRI‐peptide system) that a functional type 2 copper center exhibiting copper nitrite reductase (NiR) activity exhibits the highest homogeneous catalytic efficiency under aqueous conditions for the reduction of nitrite to NO and H₂O. Modification of the amino acids in the second coordination sphere of the copper center increases the nitrite reductase activity up to 75‐fold compared to previously reported systems. We find also that steric bulk can be used to enforce a three‐coordinate Cu^I in a site, which tends toward two‐coordination with decreased steric bulk. This study demonstrates the importance of the second coordination sphere environment both for controlling metal‐center ligation and enhancing the catalytic efficiency of metalloenzymes and their analogues.     

Antiferromagnetic Coupling in a New Mn(III) Schiff Base Complex with Open-Cubane Core: Structure,Spectroscopic and Luminescence Properties

A new open-cubane Mn^III, [{(H₂O)Mn^IIIL}{Mn^IIIL}]₂·2(CH₃OH).2(CH₃CH₂OH)·2Cl, 1 where H ₂ L=[N-(2-hydroxyethyl)-3-methoxysalicylaldimine] has been synthesized and characterized by element analysis, FT-IR, solid UV–Vis spectroscopy and single crystal X-ray diffraction. The crystal structure determination shows an open-cubane tetranuclear complex. The Mn1 (Mn1ⁱ) ions is hexacoordinate by NO₅ donor sets while the Mn2 (Mn2ⁱ) is pentacoordinate by NO₄ donor sets. The solid state photoluminescence properties of complex 1 and its ligand H ₂ L have been investigated under UV light at 349 nm in the visible region. H ₂ L exhibits blue emission while complex 1 shows orange-red emission at room temperature. Variable-temperature magnetic susceptibility measurements on the complex 1 in the range 2–300 K indicate an antiferromagnetic interaction.     

Photophysical properties of a series of free-base corroles

Four free-base corroles with electron-donating or electron-withdrawing groups on the para or 2 through 6-positons of the meso phenyl rings were prepared via either Paolesse or Gross conditions and investigated for their absorption and emission properties. The triaryl corroles 5,10,15-triphenylcorrole, 5,10,15-tris(pentafluorophenyl)corrole, 5,10,15-tris(p-nitrophenyl)corrole, and 5,10,15-tris(p-methoxyphenyl)corrole were examined. Absorption, steady-state, and time-resolved fluorescence measurements were performed on all compounds in both nonpolar (dichloromethane) and polar (dimethylacetamide) solvents. The experimental evidence points to hydrogen bonding with an internal N-H group as the most likely factor in the solvent-dependent photophysical behavior of these corroles, that is also highly dependent upon substitution.     

An experimentally validated electromagnetic energy harvester

A relatively simple method for determining the electromechanical parameters of electromagnetic energy harvesters are presented in this paper. The optimal power generated through a load resistor at both off-resonance and resonance is derived analytically. The experimentally measured performance of a rudimentary electromechanical energy harvester using a rare-earth magnet shows good agreement with the results from the model. The parasitic generator coil resistance can have a profound effect on the overall performance of an electromagnetic generator by essentially acting to degrade the effective coupling coefficient. Data from the setup electromagnetic generator shows normalized power densities of 1.7 μW/[(m/s²)² cm³] operating at a resonance frequency of 112.25 Hz. This power density is comparable with other electromagnetic devices of the same volume operating at these frequencies. The power output of the presented electromagnetic generator is comparable to equivalent piezoelectric generators.