Lipid oxidation in herring (Clupea harengus) light muscle, dark muscle, and skin, stored separately or as intact fillets

Light muscle, dark muscle, and skin from herring (Clupea harengus) were stored separately or as intact fillets at −18°C. After 0, 2, 8, 12, and 18 wk, all tissues were analyzed for conjugated dienes (A₂₃₄) and lipid hydroperoxides. In tissues stored separately, total absorbance at 268 nm (A₂₆₈) and lipid-soluble fluorescent oxidation products (FP) were also monitored. Further, prior to storage these tissues were subjected to measurement of total lipids, lipid classes, fatty acid pattern, α-tocopherol, iron, copper, selenium, and total aqueous pro-oxidative activity. When light muscle, dark muscle, and skin were stored as intact fillets, the following ranking order was seen for A₂₃₄ and levels of lipid hydroperoxides at the end of the storage period: skin > dark muscle > light muscle. The corresponding ranking order for tissues stored separately was: dark muscle > skin > light muscle, whereas for A₂₆₈ and FP the orders were: dark muscle > light muscle > skin and light muscle > dark muscle > skin, respectively. The compositional data obtained indicate the highest level of pro-oxidants in dark muscle and the highest level of polar lipids in light muscle. These observations reveal that pro-oxidants, to a greater extent than lipid composition, influence the increase in A₂₃₄, hydroperoxides, and A₂₆₈, whereas the reverse seems to be true for the increase in FP. The results also point to the strong influence from oxygen contact and tissue interactions on the progress of lipid oxidation in herring during storage.     

An apparatus for the measurement of lipoxygenase activity and pentane production

The enzyme lipoxygenase has been demonstrated to produce pentane. However, until now no apparatus has been available to measure the pentane concomitantly with the lipoxygenase activity. Such an apparatus is described by this paper. The apparatus consists of a reaction vessel which can be sealed with a rubber septum to allow sampling for pentane production and an oxygen measuring device to determine the oxygen level of the system. The apparatus is being used to conduct in-depth studies of the lipoxygenase enzyme and its possible role in food quality. Paper 4128 of the journal series of the North Carolina State University Agricultural Experiment Station, Raleigh, N.C.     

Evaluation of the agronomic effectiveness of natural and partially acidulated phosphate rocks in several soils using32P isotopic dilution techniques

The agronomic effectiveness of two natural phosphate rocks (PRs) from North Carolina (USA) and Togo and their 50% partially acidulated products (PAPRs) was evaluated in two greenhouse experiments using³²P isotopic dilution techniques, namely L and A_L values.In the first experiment rye grass was grown in a soil from Ghana. While the proportion of P in the plant derived from the P fertilizer (Pdff) ranged on. the average from about 10% for the PRs up to 80% for the PAPRs, the P fertilizer recovery was less than 1% for a 60-day growth period. In the second experiment, average values of P in the maize plants derived from the PAPRs ranged from 35% to 75% in 3 different soils. Both PRs were ineffective with the exception of North Carolina PR in the Seibersdorf soil. The P fertilizer recovery was 0.25% for the North Carolina PR in this soil whereas the recovery values ranged from 1.2% to 1.6% for the PAPRs.Mean values of the relative fertilizer efficiency estimated from the L values of each soil were less than 1% for the PRs whereas the values for the PAPRs which were dependent on soil type ranged from 20% up to 45%. The coefficient of relative effect of partial acidulation, that was calculated from the ratio of A_L values for PR and PAPR in each soil indicated that partial acidulation increased the effectiveness of the natural PRs in all soils under study.This study showed that the use of³²P isotope dilution techniques allows an accurate measurement of the P availability from natural and modified PR products to crops. Another advantage is that quantitative comparison of the P sources under study, PRs and PAPRs in this case, can be made even in soils where there is no response to the applied P sources.     

Calcium activation of peanut lipoxygenase

Peanut lipoxygenase isozyme 1 (pH optimum, 8.3) was strongly activated by 0.5–1.0 mM Ca⁺⁺, and the rate of activation was maximum when the ratio of substrate to Ca⁺⁺ was ca. 2∶1. Peanut lipoxygenase isozymes 2 and 3 (pH optima, 6.2) were activated by calcium but did not have an optimum level of activity. Calcium differentially activated peanut lipoxygenase causing the rate of pentane production to increase much more rapidly than the rate of oxygen consumed by the enzyme reaction. At pH 6.2, in the absence of calcium, the percentages of the hydroperoxide isomers produced by peanut lipoxygenase were 74.9% 13-hydroperoxycis-9,trans-11-octadecadienoic acid (13 LOOHcis-trans), 2.6% 13-hydroperoxytrans-9,trans-11-octadecadienoic acid (13 LOOHtrans-trans) and 22.5% 9-hydroperoxy 10, 12-octadecadienoic acid (9 LOOH). The presence of 1 mM Ca⁺⁺ at pH 6.2 did not significantly affect the percentage distribution of the hydroperoxides produced. However, at pH 8.3, the percentage distribution of hydroperoxides produced was 45.2% 13 LOOHcis-trans, 10.9% 13 LOOHtrans-trans and 43.9% 9 LOOH in the absence of Ca⁺⁺ and 57.0% 13 LOOHcis-trans, 8.0% 13 LOOHtrans-trans and 35.0% 9 LOOH in the presence of 1 mM Ca⁺⁺. Paper No. 5110 of the Journal of the North Carolina Agricultural Experiment Station, Raleight, NC 27607.     

Partially acidulated phosphate rocks: Controlled release phosphorus fertilizers for more sustainable agriculture

Phosphate rocks partially acidulated either with H₃PO₄ or H₂SO₄ were compared against SSP or TSP as phosphate fertilizers for permanent pasture. Eleven field trials were conducted over periods of up to 6 yrs. Fertilizers were surface applied annually. Initial soil pHw values ranged from 5.5–6.3 and Soil P retention from 25% to 97%. The PRs used for partial acidulation were unground or ground North Carolina PR, ground Khouribga PR, and a blend of ground PRs of North Carolina, Arad and Khouribga PRs. From the DM yields, fertilizer substitution values were calculated: fertilizer substitution value was the ratio of total P applied as superphosphate to total P as PAPR required to produce the same DM yield.Rates of dissolution of the PR component of PAPRs were also determined in soils collected from two trials.Agronomic results demonstrated that 30% acidulated phosphoric PAPRs (about 50% of total P as water-soluble P) were as effective as TSP, when the PR acidulated was from unground North Carolina PR. Results from one field trial indicated that when PAPR was from ground North Carolina PR, 20% acidulated product (water-soluble P 30–40% of total P) was equally effective as TSP. Replacement of ground North Carolina PR by a less reactive Khouribga PR did not appear to decrease the yield. Results indicated that per unit P released into soil solution, PAPRs were more efficient fertilizers than TSP. With annual applications, fertilizer substitution value of PAPR 30% tended to increase with time.Sulphuric PAPRs prepared from North Carolina PR were generally inferior to phosphoric PAPRs containing similar amounts of water-soluble P. This was attributed to the presence of CaSO₄ coatings.Abbreviations DM Dry matter - PAPR Partially acidulated phosphate rock - PR Phosphate rock - SSP Single superphosphate - TSP Triple superphosphate     

2‐Amino[1,2,4]triazolo[1,5‐c]quinazolines and Derived Novel Heterocycles: Syntheses and Structure–Activity Relationships of Potent Adenosine Receptor Antagonists

2‐Amino[1,2,4]triazolo[1,5‐c]quinazolines were identified as potent adenosine receptor (AR) antagonists. Synthetic strategies were devised to gain access to a broad range of derivatives including novel polyheterocyclic compounds. Potent and selective A₃AR antagonists were discovered, including 3,5‐diphenyl[1,2,4]triazolo[4,3‐c]quinazoline ( 17 , K_i human A₃AR 1.16 nm ) and 5′‐phenyl‐1,2‐dihydro‐3′H‐spiro[indole‐3,2′‐[1,2,4]triazolo[1,5‐c]quinazolin]‐2‐one ( 20 , K_i human A₃AR 6.94 nm ). In addition, multitarget antagonists were obtained, such as the dual A₁/A₃ antagonist 2,5‐diphenyl[1,2,4]triazolo[1,5‐c]quinazoline ( 13 b , K_i human A₁AR 51.6 nm , human A₃AR 11.1 nm ), and the balanced pan‐AR antagonists 5‐(2‐thienyl)[1,2,4]triazolo[1,5‐c]quinazolin‐2‐amine ( 11 c , K_i human A₁AR 131 nm , A_2AAR 32.7 nm , A_2BAR 150 nm , A₃AR 47.5 nm ) and 9‐bromo‐5‐phenyl[1,2,4]triazolo[1,5‐c]quinazolin‐2‐amine ( 11 q , K_i human A₁AR 67.7 nm , A_2AAR 13.6 nm , A_2BAR 75.0 nm , A₃AR 703 nm ). In many cases, significantly different affinities for human and rat receptors were observed, which emphasizes the need for caution in extrapolating conclusions between different species.     

Vulcanization of Nitrile Rubber. Part I. Effect of Some Accelerators on the Physicomechanical Properties of Vulcanized Nitrile Rubber for Resistance to Fuel and General Use

Compounding mixtures were prepared based on acrylonitrile-butadiene rubber (Krynac 803) to which increasing parts per hundred rubber (pphr) of the following accelerates were added: tetramethyl thiuram disulfur (TMTD in series A₁), tetramethyl thiuram monosulfur (TMTM in series A₂), 2-mercaptobenzothiazole (MBT in series A₃), and 2,2′-dithiobisbenzothiazole (MBTS in series A₄). Effects of the quantity and type of accelerator on the vulcanization characteristics were studied. Physicomechanical investigations and swelling resistance were determined for samples immersed in benzene:benzol mixture at normal temperature. It was found that according to the type and quantity of accelerator, the optimum cure time decreased with increasing the quantity of accelerator. Relatively higher values of scorch time (8 min, at 1.0–3.0 pphr), which seems to ensure safe processing during production was obtained for TMTM (series A₂). TMTD (in quantity of 2.0 pphr) led to the highest value of rate of cure (14.0 min^?1). The best values of tensile strength (210 kg/cm², and 208 kg/cm²) were reached in TMTD (series A₁) and TMTM (series A₂), whereas MBT (series A₃) and MBTS (series A₄) resulted in tensile strength values of 140 and 155 kg/cm², respectively. The highest value of modulus (86 kg/cm²) was obtained in TMTD (series A₁ at 2.0 pphr). Whereas TMTD (series A₁) and TMTM (series A₂) led to relatively lower values of elongation at break (180% and 190%), it was found that MBT (series A₃) and MBTS (series A₄) led to higher values (280% and 260%). Small effects on the elasticity were observed when changing the type and quantity of accelerator. Relatively higher values of hardness were reached for series A₁ and A₂ as compared with series A₃ and A₄. The lowest values of percent volume increase after immersion in benzene:benzol mixture (8.3%) was obtained for A₁ (at 1.5 pphr of TMTD), as compared with the other three accelerators.     

An efficient method for a numerical description of virgin olive oil color with only two absorbance measurements

Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic coordinates and the chroma—L ^*, a ^*, b ^*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480 and 670 nm. These are as follows: L ^*=0.556458(A₄₈₀)²−2.51145A₄₈₀+0.55504(A₆₇₀)²−8.53016A₆₇₀+98.4089; a ^*=0.177372(A₄₈₀)²+2.1363A₄₈₀+1.43254(A₆₇₀)²−0.789231A₆₇₀−13.9246; b ^*=−16.0277(A₄₈₀)²+79.8932A₄₈₀−5.06558(A₆₇₀)²+3.36169A₆₇₀+31.9405; C=−15.8439(A₄₈₀)²+78.9312A₄₈₀−5.26784(A₆₇₀)²+3.56917A₆₇₀+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale d’Eclairage (CIE) L ^* a ^* b ^* system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L ^* , a ^* , b ^* , and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R ²-terms also confirmed the validity of the method.     

Effect of A+ (A = Li,Na and K) co-doping on enhancing the luminescence of Ca5(PO4)2SiO4:Eu3+ red-emitting phosphors as charge compensator

A series of Ca_5-x(PO₄)₂SiO₄:xEu³⁺ red-emitting phosphors were synthesized through solid-state reaction, and alkali metal ions A⁺ (A = Li, Na and K) were co-doped in Ca₅(PO₄)₂SiO₄:Eu³⁺ to improve its luminescence property. The impacts of synthesis temperature, luminescence center Eu³⁺ concentration and charge compensator A⁺ on the structure and luminescence property of samples were studied in detail. X-ray diffraction results indicated that prepared Ca₅(PO₄)₂SiO₄:Eu³⁺, A⁺ had a standard Ca₅(PO₄)₂SiO₄ structure with space group P6₃/m. Under the excitation of 392 nm, Ca₅(PO₄)₂SiO₄:Eu³⁺ phosphors showed a red emission consisting of several emission peaks at 593 nm, 616 nm and 656 nm, relevant to ⁵D₀→⁷F₁, ⁵D₀→⁷F₂ and ⁵D₀→⁷F₄ electron transitions of Eu³⁺ ions, respectively. Luminescence intensity and lifetime of Ca₅(PO₄)₂SiO₄:Eu³⁺ can be significantly enhanced through co-doping alkali metal ion A⁺, which play an important role as charge compensator. The results suggest that Ca₅(PO₄)₂SiO₄:Eu³⁺, A⁺ red phosphors with excellent luminescence property are expectantly served as red component for white light-emitting diodes excited by near-ultraviolet.     

Effects of moderate pressure on premeability and viability of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> cells

With CO₂ and N₂ as the pressure media, the effects of the moderate pressure (0.1–1.0MPa) and the holding time on the conductivities of the cell suspension of Saccharomyces cerevisiae CICC1447 and Saccharomyces cerevisiae CICC1339, as well as the absorbances of the supernatant (after centrifuged) at 280 nm (A₂₈₀) and 260 nm (A₂₆₀) were determined. The membrane permeability of Saccharomyces cerevisiae CICC1447 increased significantly and the cell leakage was aggravated with the pressure increase. For Saccharomyces cerevisiae CICC1339, the conductivity of the cell suspension, A₂₈₀ and A₂₆₀ of the supernatant fluctuated with the pressure increase; as a whole, they increased with pressure. Different from high pressure, a moderate pressure not only remarkably improved the permeability of the yeast cell membrane, but also kept yeast cell viability; moreover, the integrity of the yeast cell membrane could be maintained. The first author and the fifth author contributed to the work equally.     

Emission analysis of CdO–Bi2O3–B2O3 glasses doped with Eu and Tb

This article reports on the emission properties of cadmium bismuth borate (CdBiB) glasses as a function of doping concentrations of Eu³⁺ and Tb³⁺ ions. The functional groups present in the glasses have been identified by analyzing FT-IR spectra. The emission spectra of Eu³⁺ and Tb³⁺:CdBiB glasses have shown reddish green emissions at 616 nm (⁵D₀→⁷F₂) under the excitation at 465 nm and at 547 nm (⁵D₄→⁷F₅) under the excitation at 485 nm, respectively. The Judd–Ofelt (J–O) theory was applied to evaluate the J–O intensity parameters from the absorption and the emission spectra; by using the J–O intensity (Ω_λ) parameters, spontaneous emission transition probability (A), total radiative transition rate (A_T), radiative lifetime (τ_R) and branching ratios (β) of the various emission transitions have been computed for both Eu³⁺ and Tb³⁺:CdBiB glasses. The quenching behavior in the emission intensity with increased concentration of Eu³⁺ and Tb³⁺ was observed, which could be useful for optimizing the compositions toward practical applications.     

8‐Benzyltetrahydropyrazino[2,1‐f]purinediones: Water‐Soluble Tricyclic Xanthine Derivatives as Multitarget Drugs for Neurodegenerative Diseases

8‐Benzyl‐substituted tetrahydropyrazino[2,1‐f]purinediones were designed as tricyclic xanthine derivatives containing a basic nitrogen atom in the tetrahydropyrazine ring to improve water solubility. A library of 69 derivatives was prepared and evaluated in radioligand binding studies at adenosine receptor (AR) subtypes and for their ability to inhibit monoamine oxidases (MAO). Potent dual‐target‐directed A₁/A_2A adenosine receptor antagonists were identified. Several compounds showed triple‐target inhibition; one of the best compounds was 8‐(2,4‐dichloro‐5‐fluorobenzyl)‐1,3‐dimethyl‐6,7,8,9‐tetrahydropyrazino[2,1‐f]purine‐2,4(1H,3H)‐dione ( 72 ) (human AR: K_i A₁ 217 nM , A_2A 233 nM ; IC₅₀ MAO‐B: 508 nM ). Dichlorinated compound 36 [8‐(3,4‐dichlorobenzyl)‐1,3‐dimethyl‐6,7,8,9‐tetrahydropyrazino[2,1‐f]purine‐2,4(1H,3H)‐dione] was found to be the best triple‐target drug in rat (K_i A₁ 351 nM , A_2A 322 nm; IC₅₀ MAO‐B: 260 nM ), and may serve as a useful tool for preclinical proof‐of‐principle studies. Compounds that act at multiple targets relevant for symptomatic as well as disease‐modifying treatment of neurodegenerative diseases are expected to show advantages over single‐target therapeutics.     

UV–VIS absorption and NIR‐stimulated emission of Nd3+: PVA films

Neodymium‐doped polyvinyl alcohol films were prepared and the optical properties of the films were investigated. By applying Judd–Ofelt theory, the Ω parameters were obtained from the absorption spectrum. Various radiative parameters like transition probability for each level (A_J), total transition probability (A_T), branching ratio (β_R), radiative lifetime (τ_rad), and absorption cross‐section (σ_A) were calculated. The theoretically obtained branching ratio and integrated absorption cross‐section are found to be greater for the transition ⁴F_3/2 → ⁴I_11/2. From the emission spectrum peaked at 1064‐nm stimulated emission cross‐section (σ_E), the line width (Δλ_eff) is calculated to be 6.21 × 10^?21 cm² and 41 nm, respectively. Further the variation of the optical gain with the length of the film was studied and the slope efficiency (η = 8.5%) was determined from laser measurements. These results clearly support the potentiality of the Nd³⁺: polyvinyl alcohol films in realizing optical amplification and stimulated emission. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Isolation and characterization of thermostable phycocyanin from Galdieria sulphuraria

Phycocyanin is a highly valuable pigmented protein synthesized by several species of cyanobacteria and red alga. In this study we demonstrate the production of thermostable phycocyanin from the unicellular red alga Galdieria sulphuraria. Phycocyanin was extracted by repeated freeze-thaw cycles and purified in a two-step process using ammonium sulfate fractionation, at 25% and 50% concentrations. Purified phycocyanin exhibited maximum absorbance at 620 nm, and the purity ratio (A₆₂₀/A₂₈₀) was found to be greater than 4. The recovery efficiency of phycocyanin from the crude extract was above 80%. In total, approximately 19 milligram pure phycocyanin was obtained from 3 g of wet cell mass of Galdieria sp. Subunits α and β of the protein were separated by SDS-PAGE and analyzed by MALDITOF mass spectrometry for identification, which confirmed that the isolated protein is phycocyanin. The molecular weight of α and β subunits of phycocyanin was found to be 17.6 and 18.4 kDa, respectively.     

Effects of mixtures of phenolic acids on leaf area expansion of cucumber seedlings grown in different pH portsmouth A1 soil materials

Cucumber seedlings growing in A₁horizon Portsmouth soil material adjusted to pH 5.2, 6.0, or 6.9 were treated with 0, 0.25 or 0.5, mol/ g soil ferulic acid,p-coumaric acid, vanillic acid, or an equal mixture (0.5 mol/g total) of two acids every other day. A total of five treatments was given starting with day 7 from seeding. Absolute rates of leaf expansion were determined for seedlings. The experiment was terminated when seedlings were 17 days old. All three phenolic acids inhibited leaf expansion. The dose required for 50% inhibition of absolute rates of leaf expansion increased as pH of the soil systems increased. The order of toxicity based on 50% dose and relative potency were as follows: ferulic acid > vanillic acid =p-coumaric acid. Effects of mixtures of phenolic acids on absolute rates of leaf expansion, when compared to the effects of individual phenolic acids, were found to be antagonistic for the ferulic-vanillic acid mixture and the ferulic-p-coumaric acid mixture in the pH 5.2 soil systems. Several phenolic acid treatments were required before antagonistic effects of mixtures were evident. In all other instances, when treatment effects were significant, the effects of individual phenolic acids were additive.Paper No. 11875 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601. The use of trade names in this publication does not imply endorsement by North Carolina Agricultural Research Service of the product named, nor criticism of similar products not mentioned. This research was partially supported by US-Spain Joint Committee for Scientific and Technological Corporation project CCA-8309/166.     

The Fe(CO)5 catalyzed pyrolysis of pentane: carbon nanotube and carbon nanoball formation

The Fe(CO)₅ catalyzed pyrolysis of pentane was investigated. The study, performed in a quartz tube, revealed that a range of carbonaceous materials could be formed with products determined by the temperature profile in the tube, the Fe(CO)₅ content in pentane, the carrier gas flow rate, the pyrolysis temperature and the pyrolysis time. The distribution of carbonaceous products also depends on the competition of the pyrolysis of Fe(CO)₅ and pentane in the different regions of the reactor. Carbonaceous materials produced included graphite film, carbon nanotubes and carbon nanoballs. The formation of carbon nanotubes takes place in a region in the quartz tube where both the pyrolysis of both Fe(CO)₅ and pentane occur, with carbon nanotubes formed by the pyrolysis of pentane. Alignment of carbon nanotubes was found when a high Fe(CO)₅ concentration was used.     

A benign approach for novel synthesis of Eu3+ doped MgNb2O6: Its photoluminescence and photocatalytic studies

The Present work involves the production of Eu³⁺ (1–11 mol %) doped MgNb₂O₆ nanophosphors (NPs) by combustion technique using ODH as a fuel for the first time and well characterized. The average crystallite and the energy gap of the samples were found to be in the range of 20–45 nm and 4.65–5.66 eV respectively, TEM results reflects the same crystallite size values. The effect of doping was confirmed by the characteristic emission peaks recorded at ~535, 590, 614, 642 and 698 nm may be attributed to the 4f–4f intra shell transitions (⁵D₀→⁷F_j=0,1,2,3,4) of Eu³⁺ cations when bombarded at 395 nm energy. Judd–Ofelt parameters (Ω₂, Ω₄), transition probabilities (A_T), quantum efficiency (η), luminescence lifetime (τ_rad) are discussed in detail. From the emission spectra, CIE (Commission International de I’ Eclairage) chromaticity co-ordinates and Correlated color temperature (CCT) were estimated. Langmuir-Hinshelwood model was used to study the photocatalytic degradation of AR-88 dye. The above results confirmed that the present phosphor can be potentially used for display and photocatalytic applications.     

Zur Erfassung der endogenen Lipidperoxidation - Pentanproduktion in vivo beim Huhn

On the Registration of Endogenous Lipid Peroxidation - in vivo pentane Production in Broiler Chickens This report deals with experimental attempts to clarify the mechanism of pentane development in chicken after feeding fresh and oxidized reesterified triglycerid and different amounts of Vitamin E. In a closed system the concentration of exhaled pentane was determined and in-vivo production rates calculated. On the other hand pentane production was measured from intestinal chyme in an in-vitro preparation after killing the animals. With regard to the question of the microbial cause of pentane development, the effect of Clindamycin was tested both in the in-vitro and in-vivo experiment. In-vivo pentane production rates were increased by feeding oxidized fat, Vitamin E supplementation had no significant influence. Likewise pentane formation from chyme was significantly increased by administering oxidized fats, Vitamin E however inhibited pentane formation. Clindamycin did not suppress pentane production, suggesting that in chicken feed lipid peroxides are not broken down by microbial enzymes but by spontaneous decay, anyway intestinal processes have to be considered in pentane exhalation studies.     

First crystal structure determination and high-frequency EPR study of an organoarsanecopper radical complex

The red radical complex {(μ-bptz)[Cu(AsPh₃)₂]₂}(BF₄) 1, bptz=3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, was obtained as a stable species and characterized by X-ray crystallography, spectroelectrochemistry and EPR at 9.5 and 285 GHz. Comparison with the previously reported {(μ-bptz)[Cu(PPh₃)₂]₂}(BF₄) 2 reveals longer Cu-element bonds by about 0.1 Å but otherwise a similar “organic sandwich” structure involving intramolecular π(phenyl)–π(tetrazine)–π(phenyl) interactions, a 3+1 coordination at the copper(I) centers, and averaged tetrazine intraring bond distances. Reversible oxidation to a blue dication with an intense MLCT band at 650 nm occurs at −0.24 V vs. Fc^+/o. EPR studies show the effect of the higher spin–orbit coupling constant of the As vs. P atoms through slightly larger g anisotropy as determined through high frequency measurements.