Tris Adducts Research Articles

Adducts of Tris(alkyl) Holmium(III) Showing Magnetic Relaxation.

In the series of the adducts of tris(alkyl) HoIII complexes, Ho(CH2SiMe3)3(THF)2 (1Ho-THF, Me = methyl) can exhibit slow magnetic relaxation under a zero applied direct current (DC) field with the energy barrier Δ/kB of 76 K, which is one of the highest in the non-Kramers ion HoIII-based single-ion magnets (SIMs). The DC field-dependence of relaxation time for 1Ho-THF indicates the occurrence of direct relaxation process at low temperature under certain DC fields. 1Ho-THF stands out in the series of 1Ln-THF (Ln = Tb, Dy, Ho, Er, Tm), wherein Dy congener is another SIM in the absence of a DC field with the relaxation barrier of 40 K, while Tb and Er congeners are field-induced SIMs. Further substitutions of the two trans-THF in 1Ho-THF by other neutral ligands such as quinuclidine, tricyclohexylphosphine oxide, and 3,5-lutidine afforded Ho(CH2SiMe3)3(quinuclidine)2 (2Ho-QN), Ho(CH2SiMe3)3(OPCy3)2 (3Ho-OPCy3), and Ho(CH2SiMe3)3(lutidine)3 (4Ho-Lut), respectively. The former two possess analogous structures to 1Ho-THF with two trans-arranged neutral ligands, and the latter one has three cis-lutidine coordinated. The fast quantum tunneling effect swamps the magnetic relaxation for the above three derivatives, so slow relaxation could not be observed under experimental conditions, even when a certain DC field was applied.

Optical properties and intensity parameters of UV excited efficient red emitting europium complexes containing fluorinated 1, 3-dione as primary sensitizer in solution, solid and PMMA thin films

The two adducts of tris(fluorinated β-diketonate)Eu (III) with 4,4ʹ-bpy (1) and tppo (2) were synthesized and characterized by spectroscopic techniques. The thermal stability, 1H NMR and IR studies of these complexes were discussed. The steady state and time resolved PL of the complexes were studied in chloroform, solid state and their 5% PMMA based hybrid thin films. The PL spectra of the complexes in different phases don't have characteristic emission from organic ligands (fluorescence and phosphorescence) which suggests that the energy transfer from the chosen organic sensitizers in this study to europium (III) is efficient. From the corresponding emission spectra, the photophysical parameters (e.g., radiative rate constant (Arad), non-radiative rate constant (Anrad), natural lifetime (τrad), intrinsic quantum yield (φEuEu), colour coordinate values and Judd-Ofelt intensity parameters were calculated in different phases. The φEuEu of [Eu(fod)3(tppo)2] (2) in solid state is 79% which is very high. It is worth to mention that the φEuEu of low asymmetric eight-coordinate [Eu(fod)3(tppo)2] (2) complex is higher (by 33.64% in chloroform, 15.30% in solid state and 59.198% in hybrid thin film) than low symmetric seven-coordinate [Eu(fod)3(4,4ʹ-bpy)] (1) complex. Moreover, the quantum efficiency of [Eu(fod)3(4,4ʹ-bpy)] (1) and [Eu(fod)3(tppo)2] (2) increased by 33.64 and 15.30% in solid state than their chloroform solution respectively. The φEuEu of both complexes decrease drastically when embedded in PMMA by 49.87% (1) and 40.29% (2) compared to their chloroform solutions. The colour coordinate values of both complexes depicts orange red to pure red emission.

Structure and Stereochemistry of Adducts of Tris(dipivaloylmethanato)europium(III), Eu(dpm)3, with Some Dipolar Aprotic Unidentate O-Donors

Single crystal X-ray structural characterisations are reported for adducts of the form [(L-O)Eu(O,O′-dpm)3] obtained by the crystallisation of tris(dipivaloylmethanato)europium(iii) (dpm=[HC(C(tBu).CO)2]−) from an array of dipolar aprotic oxygen-donor solvents L (L=N-methylpyrrolidinone (nmp), trimethylphosphate, (MeO)3PO, (tmp), hexamethylphosphoramide (hmpa), dimethylacetamide (dma), dimethyl sulfoxide (dmso), and the bidentate octamethylpyrophosphoramide (ompa). In all adducts, the resulting arrays contain seven-coordinate metal atoms, which adopt two different isomeric forms of the mono-capped trigonal prismatic stereochemistry, the L=dma and dmso adducts corresponding to one type, nmp and tmp the other. The adduct formed with ompa behaves as a pair of discrete metal environments bridged by the O-ompa-O′ ligand, thus; [(dpm-O,O′)3Eu(O-ompa-O′)Eu(O,O′-dpm)3], and is found in two forms, one in which both Eu environments is of the tmp type, the other of the dmso/dma type. In the hmpa adduct, the asymmetric unit of the structure is a disordered composite of both types. In none of the adducts is there any further solvation beyond coordination of a single L.

An Alcohol Dehydrogenase from the Short-Chain Dehydrogenase/Reductase Family of Enzymes for the Lactonization of Hexane-1,6-diol.

Biocatalytic production of lactones, and in particular ϵ-caprolactone (CL), have gained increasing interest as a greener route to polymer building blocks, especially through the use of Baeyer-Villiger monooxygenases (BVMOs). Despite several advances in the field, BVMOs, however, still suffer several practical limitations. Alcohol dehydrogenase (ADH)-mediated lactonization of diols in turn has received far less attention and very few enzymes have been identified for the conversion of diols to lactones, with horse-liver ADH (HLADH) remaining the catalyst of choice. Screening of a diverse panel of ADHs, AaSDR-1, a member of the short-chain dehydrogenase/reductase family, was found to produce ϵ-caprolactone from hexane-1,6-diol. Moreover, cofactor regeneration by an NADH oxidase eliminated the requirement of co-substrates, yielding water as the sole by-product. Despite lower turnover frequencies as compared to HLADH, higher selectivity was found for the production of CL, with HLADH forming significant amounts of 6-hydroxyhexanoic acid and adipic acid through aldehyde dehydrogenation/oxidation of the gem-diol intermediates. Also, CL yield were shown to be dependent on buffer choice, as structural elucidation of a Tris adduct confirmed the buffer amine to react with aliphatic aldehydes forming a Schiff-base intermediate which through further ADH oxidation, forms a tricyclic acetal product.

Theoretical study on reaction mechanisms of nitrite reduction by copper nitrite complexes: toward understanding and controlling possible mechanisms of copper nitrite reductase.

Using density functional theory, we studied denitrification reaction mechanisms of copper adducts of tris(pyrazolyl)methane and hydrotris(pyrazolyl)borate models of a copper nitrite reductase (Cu-NiR), and herein propose several possible reaction pathways, including some parts that have never been examined previously. Because electron and proton transfer reactions participate in the enzymatic cycles of Cu-NiR, the Gibbs energy of a proton in solution, G(H(+)), and the redox potential, Eredox, of the model Cu-NiR are also evaluated. Although the pathway where a nitrite is provided as HNO2 is energetically preferable, a well-known reaction pathway passing through the resting state with an active site occupied by a water molecule where nitrite is provided as NO2(-) is the main recognized pathway under normal conditions. These features do not change whether the electron transfer occurs before production of NO or not. However, our results suggest that the pathway involving HNO2 might become dominant under low pH conditions in conjunction with experimental results.

Hydrophilic gold nanoparticles stabilized with tris(2-aminoethyl)amine: Preparation and characterization

The synthesis of Au nanoparticles through the reduction of HAuCl4 with sodium borohydride in a mixture of ethanol and isopropanol in the presence of tris(2-aminoethyl)amine is presented. The resulting powder preparation is a mixture of primary particles with the average diameter of golden cores 3.2±0.6nm, and secondary particles that were formed as a result of agglomeration of the primary ones and have core diameter up to 20nm. The Au content of the preparation is 1.94% because Au nanoparticles have voluminous protective shells composed of the adducts of tris(2-aminoethyl)amine, acetone and boric acid, formed due to hydrogen bonding. The preparation is hydrophilic and allows one to obtain colloid solutions in water and polar solvents like acetone, isopropanol, dimethylsulphoxide, and in chloroform under ultrasonic treatment.

An expeditious regioselective synthesis of [60]fullerene e,e,e tris-adduct building blocks

A threefold Bingel reaction between C60 and t-butyl(trialkoxy)silane derivatives bearing three malonate substituents gave access to fullerene e,e,e tris adducts. Subsequent desilylation with HF·pyridine or BF3·Et2O afforded the corresponding fullerene tris-adducts bearing three alcohol functions.

Effect of Multiple Adduct Fullerenes on Microstructure and Phase Behavior of P3HT:Fullerene Blend Films for Organic Solar Cells

The bis and tris adducts of [6,6]phenyl-C(61)-butyric acid methyl ester (PCBM) offer lower reduction potentials than PCBM and are therefore expected to offer larger open-circuit voltages and more efficient energy conversion when blended with conjugated polymers in photovoltaic devices in place of PCBM. However, poor photovoltaic device performances are commonly observed when PCBM is replaced with higher-adduct fullerenes. In this work, we use transmission electron microscopy (TEM), steady-state and ultrafast time-resolved photoluminescence spectroscopy (PL), and differential scanning calorimetry (DSC) to probe the microstructural properties of blend films of poly(3-hexylthiophene-2,5-diyl) (P3HT) with the bis and tris adducts of PCBM. TEM and PL indicate that, in as-spun blend films, fullerenes become less soluble in P3HT as the number of adducts increases. PL indicates that upon annealing crystallization leads to phase separation in P3HT:PCBM samples only. DSC studies indicate that the interactions between P3HT and the fullerene become weaker with higher-adduct fullerenes and that all systems exhibit eutectic phase behavior with a eutectic composition being shifted to higher molar fullerene content for higher-adduct fullerenes. We propose two different mechanisms of microstructure development for PCBM and higher-adduct fullerenes. P3HT:PCBM blends, phase segregation is the result of crystallization of either one or both components and is facilitated by thermal treatments. In contrast, for blends containing higher adducts, the phase separation is due to a partial demixing of the amorphous phases. We rationalize the lower photocurrent generation by the higher-adduct fullerene blends in terms of film microstructure.

DFT Study of Paramagnetic Adducts of Tris-(8-hydroxyquinoline)aluminum (III)

Radicals formed by the addition of hydrogen (H) or muonium (Mu) to tris(8-hydroxyquinoline)aluminum(III) (Alq(3)) have been studied using density functional theory (DFT) calculations. Drew et al. (Phys. Rev. Lett. 2008, 100, 116601) studied Alq(3) using the longitudinal field muon spin relaxation technique and assumed the formation of muoniated radicals and rapid intermolecular electron hopping with a rate of (1.4 ± 0.2) × 10(12) s(-1). In this work, the results of DFT calculations on Alq(3), the H/Mu adducts of Alq(3), and the corresponding anions and cations are reported. The energy required to transfer an electron to or from the H/Mu adducts of Alq(3) is prohibitively large, ranging from 4.09 to 5.68 eV, which suggests that the unpaired electron does not hop onto neighboring molecules and that there is no long-range diffusion of the unpaired electron. The hyperfine coupling constants for the muoniated radicals were calculated and used to predict avoided level crossing resonance fields, which will allow experimenters to confirm that the unpaired electron is localized in close proximity to the muon.

Stable adducts of nerve agents sarin, soman and cyclosarin with TRIS, TES and related buffer compounds—Characterization by LC-ESI-MS/MS and NMR and implications for analytical chemistry

Buffering compounds like TRIS are frequently used in chemical, biochemical and biomedical applications to control pH in solution. One of the prerequisites of a buffer compound, in addition to sufficient buffering capacity and pH stability over time, is its non-reactivity with other constituents of the solution. This is especially important in the field of analytical chemistry where analytes are to be determined quantitatively. Investigating the enzymatic hydrolysis of G-type nerve agents sarin, soman and cyclosarin in buffered solution we have identified stable buffer adducts of TRIS, TES and other buffer compounds with the nerve agents. We identified the molecular structure of these adducts as phosphonic diesters using 1D 1H- 31P HSQC NMR and LC-ESI-MS/MS techniques. Reaction rates with TRIS and TES are fast enough to compete with spontaneous hydrolysis in aqueous solution and to yield substantial amounts (up to 20–40%) of buffer adduct over the course of several hours. A reaction mechanism is proposed in which the amino function of the buffer serves as an intramolecular proton acceptor rendering the buffer hydroxyl groups nucleophilic enough for attack on the phosphorus atom of the agents. Results show that similar buffer adducts are formed with a range of hydroxyl and amino function containing buffers including TES, BES, TRIS, BIS-TRIS, BIS-TRIS propane, Tricine, Bicine, HEPES and triethanol amine. It is recommended to use alternative buffers like MOPS, MES and CHES when working with G-type nerve agents especially at higher concentrations and over prolonged times.

Modulating Electronic Interactions between Closely Spaced Complementary π Surfaces with Different Outcomes: Regio‐ and Diastereomerically Pure Subphthalocyanine–C60 Tris Adducts

Modulating Electronic Interactions between Closely Spaced Complementary π Surfaces with Different Outcomes: Regio‐ and Diastereomerically Pure Subphthalocyanine–C₆₀ Tris Adducts

Modulating Electronic Interactions between Closely Spaced Complementary π Surfaces with Different Outcomes: Regio‐ and Diastereomerically Pure Subphthalocyanine–C60 Tris Adducts

Modulating Electronic Interactions between Closely Spaced Complementary π Surfaces with Different Outcomes: Regio‐ and Diastereomerically Pure Subphthalocyanine–C₆₀ Tris Adducts

Synthesis and Stability Studies of the Glutathione and N-Acetylcysteine Adducts of an Iminoquinone Reactive Intermediate Generated in the Biotransformation of 3-(N-Phenylamino)propane-1,2-diol: Implications for Toxic Oil Syndrome

Epidemiological studies have pointed to fatty acid mono- and diesters of 3-(N-phenylamino)propane-1,2-diol (PAP) as the biomarkers of the toxic oil batches that caused toxic oil syndrome (TOS), an intoxication episode that occurred in Spain in 1981, causing over 400 deaths and affecting more than 20000 people. The biotransformation of PAP administered intraperitoneally to two mouse strains produced potentially toxic metabolites. The identification of 3-(4'-hydroxyphenylamino)propane-1,2-diol among those metabolites was important because the compound can generate the quinoneimine intermediate 2. The potential toxicity of quinoneimines has been attributed primarily to their electrophilic character. Accordingly, the reactions of 2 with N-acetylcysteine, N-acetylcysteine methyl ester, and GSH were investigated. Quinoneimine 2 reacts with the N-acetylcysteine methyl ester to give the expected conjugate as a major product, accompanied by the corresponding bis and tris adducts. The monoadduct, when isolated in pure form, undergoes spontaneous oxidation to generate a new quinoneimine intermediate, which in turn rearranges and undergoes hydrolysis to afford the thiol adduct formally derived from the quinoneimine generated from p-aminophenol. The same overall pathway was observed for the reaction of 2 with N-acetylcysteine and GSH. Both thiol reagents reacted with the quinoneimine to give the corresponding adducts in which the addition took place at the ortho position with respect to the amino group. These conjugates were also unstable and ultimately afforded the corresponding adduct derived from p-aminophenol. The relevancy of these results to TOS, as well as their potential generalization for quinoneimines derived from other xenobiotics, is discussed herein.

Intra- and Intermolecular N−H···F−C Hydrogen-Bonding Interactions in Amine Adducts of Tris(pentafluorophenyl)borane and -alane

The reaction between B(C(6)F(5))(3) and NH(3)(g) in light petroleum yielded the solvated adduct H(3)N.B(C(6)F(5))(3).NH(3). Treatment with a second equivalent of B(C(6)F(5))(3) afforded H(3)N.B(C(6)F(5))(3). Attempts to prepare the analogous alane adduct were unsuccessful and resulted in protolysis. Related compounds of the form R'R' 'N(H).M(C(6)F(5))(3) were synthesized from M(C(6)F(5))(3) and the corresponding primary and secondary amines (M = B, Al; R' = H, Me, CH(2)Ph; R' ' = Me, CH(2)Ph, CH(Me)(Ph); R'R' ' = cyclo-C(5)H(10)). The solid-state structures of 13 new compounds have been elucidated by single-crystal X-ray diffraction and are discussed. Each of the borane adducts has a significant bifurcated intramolecular hydrogen bond between an amino hydrogen and two o-fluorines, while N-H...F-C interactions in the alane adducts are weaker and more variable. (19)F NMR studies demonstrate that the borane adducts retain the bifurcated C-F...H...F-C hydrogen bond in solution. Compounds of the type R'R' 'N(H).M(C(6)F(5))(3) conform to Etter's rules for the prediction of hydrogen-bonding interactions.

Effects of common buffer systems on drug activity: the case of clerocidin.

Two widely used biological buffers [tris(hydroxymethyl)aminomethane (TRIS) and phosphate] covalently react with the topoisomerase II inhibitor clerocidin, affecting the drug's reactivity profile. Comprehensive analytical and structural analysis obtained by LC/MS, MS/MS, NMR, and IR techniques shows that these buffers form reversible and irreversible adducts through reactions with chemical groups, such as carbonyls, aldehydes, and epoxide. Analysis of the kinetic data on adducts formation suggests two parallel mechanisms for the inhibition of drug activity. The first involves modulation of the reactivity of the epoxide group obtained by elimination of the spiro system and relief of ring strain. This effect does not abolish epoxide reactivity and is more evident for the TRIS adduct, which can count on intramolecular stabilization of the form devoid of the spiro system. The second mechanism involves the slow nucleophilic attack to the epoxide ring, which results in permanent deactivation of the functional group responsible for topoisomerase II inhibition. This effect is predominant in phosphate buffer and is more evident for longer reaction times. These results provide a compelling reminder that the activity of chemically complex drugs in biological systems can be severely altered by buffer interactions, which may not be immediately predictable from the identity of the active group(s) and may require a more detailed knowledge of the subtle effects induced by vicinal groups.

Synthesis of Xyloketals, Natural Products from the Mangrove Fungus Xylaria sp

AbstractThe xyloketal family of compounds was synthesized by condensation of phloroglucinol (7) or 2,4‐dihydroxyacetophenone (15) with the enone 8a or 14 in multistep, one‐pot, domino reactions, leading to the xyloketals and 5‐demethylxyloketals, respectively. In the case of condensation with phloroglucinol (7), the mono‐, bis, and tris adducts 6/18, 2/19, 1/20 are formed; their ratios depend on the ratio of stating materials and reaction time. The ring junction of the pyran and furan rings B and C (at C‐2 and C‐6) is always cis. The cis orientation of the methyl groups at C‐2 and C‐5 is also predominant (8.5:1.5), as found in the natural products. In the bis and tris adducts (2/19, 1/20), the relative orientation of the rings B and C can be syn and anti, with the sterically less demanding anti orientation slightly favored statistically. Xyloketal D (4a) was obtained in the condensation of 15 with enantiomerically enriched enone 8a, confirming the absolute configuration of the natural product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris(β -diketonato)lanthanide(III) complexes were prepared, where the β -diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β -diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.

Synthesis, Structures, and Donor−Acceptor Adducts of Tris(3,3-dimethyl-1-butynyl)borane

The synthesis and properties of tris(3,3-dimethyl-1-butynyl)borane (1), the first donor-free tris(alkynyl)borane, and of its adducts 2 [donor = pyridine (2a), triphenylphosphane (2b), tetrahydrofuran (2c)] are reported. X-ray structure analyses reveal that the B−C bond lengths in 1 are shorter than in 2; however, the C≡C triple bond lengths are similar to those of the donor-stabilized compounds 2a, 2b, and 2c. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Characterization of a 5'-aldehyde terminus resulting from the oxidative attack at C5' of a 2-deoxyribose on DNA.

The 5'-aldehyde terminus is a DNA oxidative damage resulting from attack at C5' of 2-deoxyriboses by some potent natural or chemical DNA cleavers. To offer a fast and specific method for characterization of this type of damage, we used on-line electrospray ionization mass spectrometry (ESI-MS) detection during liquid chromatography analyses. The intrinsic reactivity of 5'-aldehyde terminus with nucleophiles (formation of hydrate with water, of a Tris adduct with Tris buffer) or through beta-elimination reaction resulted in complex LC profiles and MS data. We showed that derivatization of the aldehyde function as an oxime ether gives a stable derivative easy to characterize during on-line ESI-MS analyses. Complete structural characterization of the Tris adduct and the oxime ether derivative were obtained from MS and detailed NMR studies performed on derivatized 5'-aldehyde thymidine models.

Thermolysis of free-radical initiators: tert-butylazocumene and its 1,3- and 1,4-bisazo and 1,3,5-trisazo analogues.

Four tert-butylazocumenes (4-7) were prepared from the corresponding cyanobenzenes, and their nitrogen evolution kinetics and products were analyzed. In combination with TEMPO, the simplest compound, tert-butylazocumene (4), shows promise as a "one-radical" initiator of styrene polymerization. The ABNO-trapped cumyl radical 29 is a particularly stable trialkylhydroxylamine, whose thermolysis half-life is 2.1 h at 150 degrees C. Taking advantage of this stability, we trapped the cumyl radical centers from 7 to afford tris adduct 32a. While the behavior of the meta bisazoalkane 6 can be mostly predicted from that of 4, the para isomer 5 exhibits both unusual products and kinetics, attributed to the formation of quinodimethane 33 via azo-containing radical 34. In fact, flash vacuum pyrolysis of 5 allowed observation of the (1)H and (13)C NMR spectra of 33, whose persistence even at ambient temperature showed that this quinodimethane is far more stable than the parent 36. Finally, evidence is presented that 7 is an initiator of star polymerization.