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1.
Tetranuclear, Oxygen Centered Copper(II) Clusters Linked Together with Guanidine-Guanidinate Ligands
Gina M. Chiarella Doris Y. Melgarejo Andrey V. Prosvirin Kim R. Dunbar John P. Fackler 《Journal of Cluster Science》2010,21(3):551-565
The reaction of copper(I) chloride with Htbo (1,4,6-triazabicyclo[3.3.0]oct-4-ene) under reflux in THF with oxidation by oxygen,
produces a neutral cluster comprising two oxo-tetra-copper(II) units connected by six tbo− bridges three of them bind two and the other three bind four metals; each unit also contains three chlorine bridges and a
Htbo terminal ligand. Two different X-ray crystal structures (1a, 1b) have been determined and the magnetic behavior has been studied. The molar magnetic susceptibility measurements indicate
strong exchange interactions within an oxo cluster with coupling constants of J
1 = −163 cm−1 and J
2 = −1.1 cm−1, and a weak interaction across the guanidinate bridges of J
3 = −5.2 cm−1 of the octa-CuII cluster. 相似文献
2.
A naringenin Schiff-base ligand (H3L) and its three complexes, MHL . nH2O (M = Zn and Cu, n = 0.5) and NiH2LOAc . 3.5H2O, have been synthesized and characterized on the basis of elemental analysis, molar conductivity and i.r. spectrum, 1H-n.m.r., u.v. spectra and thermal analyses. In addition, the suppression ratio for O2−˙ (a) and the suppression ratio for OH˙(b) were determined by the use of spectrophotometric methods. IC50(a) and IC50(b) of the complexes are given. The results show that compared to the ligand, the complexes exhibit high activity in the suppression
of O2−˙ (a) and OH˙(b). 相似文献
3.
Dimethylgermylene and its Ge=Ge doubly bonded dimer, tetramethyldigermene, have been characterized directly in solution by
308-nm laser flash photolysis in n-hexane solution, as well as 254-nm photolysis in hydrocarbon glasses at t = 77 K. An absorption band maximum of λ
max ≈ 430 nm and molar absorption coefficient of ε ≈ 2,700 M−1 cm−1 have been shown to be attributable to low-temperature glasses, while the absorption band maximum of λ
max ≈ 480 nm and molar absorption coefficient of ε ≈ 2,400 M−1 cm−1 have been shown to be related to dimethylgermylene in n-hexane solution. The molar absorption coefficient of tetramethyldigermene (λ
max ≈ 380 nm) was determined to be ε ≈ 84,000 M−1 cm−1. The germylene is formed via (formal) cheletropic photocycloreversion of 7,7′-dimethylgerma-1,4,5,6-tetraphenyl-2,3-benzo-norbornadiene.
Tetramethyldigermene and 1,2,3,4-tetraphenylnaphthalene in the triplet state were formed, together with dimethylgermylene.
We attempted to explain the various contradictory interpretations of experimental data existing in the literature on this
reaction. 相似文献
4.
Ding-Wa Zhang Zheng-Yin Yang Shi-Ping Zhang Ru-Dong Yang 《Transition Metal Chemistry》2006,31(3):333-336
A novel ligand (H2L), diethylenetriamine-N,N′,N′′-triacetylisoniazide N,N′′-bisacetic acid, and its four non-ion transition metal complexes,
ML · nH2O (M = Mn, n = 4; M = Co, Ni, n = 2; M = Cu, n = 1), have been synthesized and characterized on the basis of elemental analysis, molar conductivity, 1H-NMR, FAB-MS, TG-DTA analysis and IR spectrum. In addition, relaxivity (R1) of the complexes was determined, the relaxivity of MnL, CoL, NiL, CuL as well as Gd(DTPA)2− used as a control are 6.94, 2.79, 2.52, 1.59 and 4.34 l mmol−1 s−1, respectively. The relaxivity of MnL is larger than that of Gd(DTPA)2−. The results show that the complex of MnL may be a potential MRI contrast agent. 相似文献
5.
Boris Orel Robi Ješe Aljaž Vilčnik Urška LavrenčIč Štangar 《Journal of Sol-Gel Science and Technology》2005,34(3):251-265
The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEOS) catalysed with HCl (hydrolysis) and to compare them with IR spectra of MTEOS catalysed with trifluoroacetic acid (TFAcOH). TFAcOH as a strong carboxylic acid performs non-hydrolytic sol-gel process based on the condensation between the alkoxide and the acid function, liberating ester molecules (solvolysis). We assessed from the time-dependent IR attenuated reflection spectroscopic (IR ATR) measurements the solvolysis and hydrolysis reactions, formation of the oligomeric species and final condensation products. Additional evidence for the formation of these species was obtained from the spectra of films dip-coated from sols aged to different extent. The results of the IR spectral analysis showed that the structure of both xerogels consisted of irregular Tn (n = 8, 10, 12) cube-like species bridged via the ladder-like oligomers (in the case of MTEOS/TFAcOH) and open-chain trisiloxane species (for MTEOS/HCl). 29Si NMR spectra of MTEOS/TFAcOH showed only signals of T3 while MTEOS/HCl spectra showed beside T3 also T2 signals, in agreement with IR spectra results. From the XRD peaks at low Bragg angles (∼ 9–10°) we inferred that both xerogels consisted of nanocrystalline CH3-SiO3/2 species. In addition, the surface energy values of the films deposited from the corresponding sols were measured and the dispersive and polar portions correlated with the spectral features noted in the films. 相似文献
6.
Xiaoling Xing Fengqi Zhao Liang Xue Kangzhen Xu Jianhua Yi Rongzu Hu 《Journal of solution chemistry》2011,40(8):1427-1434
The dissolution properties of 2-(1,1-dinitromethylene)-1,3-diazepentane in N-methyl pyrrolidone(NMP) were studied with a RD496-2000
Calvet microcalorimeter at three different temperatures. The measured molar enthalpies (Δsol
H) for 2-(1,1-dinitromethylene)-1,3-diazepentane in NMP at T=(298.15,306.15,311.15) K are (5.02, 5.59, 6.67) kJ⋅mol−1, respectively. The differential molar enthalpies (Δdif
H), the specific enthalpies (Δsol
h), and the standard heat effect (Q
Θ) for 2-(1,1-dinitromethylene)-1,3-diazepentane in NMP were obtained at the same time. The kinetic parameters of activation
energy E and pre-exponential factor A are 2.26×104 J⋅mol−1 and 102.06 s−1, which indicate that NMP is a good solvent for the title compound. 相似文献
7.
Alaa S. Amin 《Chemical Papers》2009,63(6):625-634
A simple, selective, highly sensitive and accurate procedure for the determination of trace amounts of copper has been developed
based on solid-phase spectrophotometry. Copper reacts with 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) to give a complex
with high molar absorptivity (3.17 × 107 L mol−1 cm−1, 3.07 × 108 L mol−1 cm−1, 1.22 × 109 L mol−1 cm−1, and 1.80 × 109 L mol−1 cm−1), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. The absorbance at
667 nm and 800 nm packed in a 1.0 mm cell was measured directly. Calibration is linear over the range 0.2–3.7 μg L−1 with RSD of < 1.28 % (n = 10). The detection and quantification limits of the 500 mL sample method are 79 ng L−1 and 260 ng L−1 when using 60 mg of Dowex 1-X8. For a 1000 mL sample, the detection and quantification limits are 67 ng L−1 and 220 ng L−1 using 60 mg of the exchanger. Increasing the sample volume can enhance the sensitivity. The proposed method was applied to
the determination of copper in different environmental water samples (tap, pit, spring, and river), food products (rice, corn
flour, and tea), and mushrooms, using the standard addition technique. 相似文献
8.
Patel II Trevisan J Singh PB Nicholson CM Krishnan RK Matanhelia SS Martin FL 《Analytical and bioanalytical chemistry》2011,401(3):969-982
Vibrational spectroscopy techniques can be applied to identify a susceptibility-to-adenocarcinoma biochemical signature. A
sevenfold difference in incidence of prostate adenocarcinoma (CaP) remains apparent amongst populations of low- (e.g. India)
compared with high-risk (e.g. UK) regions, with migrant studies implicating environmental and/or lifestyle/dietary causative
factors. This study set out to determine the biospectroscopy-derived spectral differences between risk-associated cohorts
to CaP. Benign prostate tissues were obtained using transurethral resection from high-risk (n = 11, UK) and low-risk (n = 14, India) cohorts. Samples were analysed using attenuated total reflection Fourier-transform infrared (FTIR) spectroscopy,
FTIR microspectroscopy and Raman microspectroscopy. Spectra were subsequently processed within the biochemical cell region
(1,800−1–500 cm–1) employing principal component analysis (PCA) and linear discriminant analysis (LDA) to determine whether wavenumber–absorbance/intensity
relationships might reveal biochemical differences associated with region-specific susceptibility to CaP. PCA-LDA scores and
corresponding cluster vector plots identified pivotal segregating biomarkers as 1,582 cm−1 (Amide I/II trough); 1,551 cm−1 (Amide II); 1,667 cm−1 (Amide I); 1,080 cm−1 (DNA/RNA); 1,541 cm−1 (Amide II); 1,468 cm−1 (protein); 1,232 cm−1 (DNA); 1,003 cm−1 (phenylalanine); 1,632 cm−1 [right-hand side (RHS) Amide I] for glandular epithelium (P < 0.0001) and 1,663 cm−1 (Amide I); 1,624 cm−1 (RHS Amide I); 1,126 cm−1 (RNA); 1,761, 1,782, 1,497 cm−1 (RHS Amide II); 1,003 cm−1 (phenylalanine); and 1,624 cm−1 (RHS Amide I) for adjacent stroma (P < 0.0001). Primarily protein secondary structure variations were biomolecular markers responsible for cohort segregation
with DNA alterations exclusively located in the glandular epithelial layers. These biochemical differences may lend vital
insights into the aetiology of CaP. 相似文献
9.
Yang Guang-Ming Liao Dai-Zheng Jiang Zong-Hui Yan Shi-Ping Wang Geng-Lin 《Transition Metal Chemistry》1998,23(3):313-315
Two new heterotrinuclear FeIII-MII-FeIII oxalate-bridged complexes have been prepared, and characterized, namely MII[(ox)FeIII(Salen)]2, [Salen = N,N′-ethylenebis(salicylideneiminate), ox = oxalate, M = Cu (1) and VO (2)]. Based on elemental analysis, conductivity measurements and i.r. spectra, the complexes are proposed to have an oxalate-bridged
structure. The magnetic susceptibilities of the complexes were measured over the 4.2–300 K range, giving the exchange integrals
J
AB = −4.23 cm−1, J
AA = −2.47 cm−1 for (1) and J
AB = −5.42 cm−1, J
AA = −1.55 cm−1 for (2). These results revealed the operation of an antiferromagnetic spin-exchange interaction between the metal ions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
V. Yu. Buz’ko G. Yu. Chuiko Kh. B. Kushkhov 《Russian Journal of Inorganic Chemistry》2012,57(1):62-67
The structural characteristics and energies of PuCl
n
(3 − n)+ and PuCl
n
(4 − n)+ complexes (n = 2–8) have been studied by the density functional theory (DFT) method in the SVWN5 local functional approximation. 相似文献
11.
Andrea Schuy Theo Woike Dominik Schaniel 《Journal of Sol-Gel Science and Technology》2009,50(3):403-408
Photoswitchable hybrid materials are successfully prepared by embedding guanidinium nitroprussides (GuNP, (CN3H6)2[Fe(CN)5NO]) into mesopores of transparent xerogel monoliths. The such prepared hybrid materials exhibit a higher photostability than
the corresponding GuNP solutions, whereby the chemical stability of the [Fe(CN)5NO]2−-anion in titania gel is nearly infinite. By irradiation with light in the blue-green spectral range one nitrosyl isomer is
formed by a 180° rotation of the NO ligand changing the Fe–NO into a Fe–ON coordination (SI), which is detected by the shift
of the ν(NO) stretching vibration from 1945 cm−1 (Fe–NO) to 1820 cm−1 (Fe–ON). Consequently there is enough space around the NO-ligand for such movement in xerogel mesopores. The embedding in
silica xerogels increases the achievable population of the isomeric nitrosyl configuration to about 15% with respect to a
single crystalline powder where only 9% are reached. 相似文献
12.
Víctor M. Ovando-Medina René D. Peralta Eduardo Mendizábal Hugo Martínez-Gutiérrez Tania E. Lara-Ceniceros Raquel Ledezma-Rodríguez 《Colloid and polymer science》2011,289(7):759-765
Conductive spherical polypyrrole nanoparticles were obtained by polymerization in oil-in-water (o/w) microemulsions using
sodium dodecyl sulfate (SDS) as anionic surfactant, ethanol as co-surfactant, and potassium persulfate (KPS, 0.017 wt.%) as
oxidizing agent. The average particle diameter (Dp) of the nanoparticles was between 38 and 45 nm with narrow particle size
distributions (D
w/D
n < 1.2). Dp increases with the ethanol concentration due to the intercalation between the polar heads of SDS, promoting instability
of the nanoparticles and some coagulation. In this work, low surfactant concentration was used, and the molar ratio of the
oxidizing agent to monomer was 8.5 × 10−3, a value much lower compared with others reported in the literature. Increasing the ethanol concentration in the recipes
enhanced the conductive properties of the polymers due to the high π-conjugation length obtained. 相似文献
13.
Brian T. Cooper Steven W. Buckner 《Journal of the American Society for Mass Spectrometry》1999,10(10):950-957
Radiative relaxation of Cr(CO)5− was investigated by two techniques: a standard two-pulse photodissociation experiment and by using the branching ratio of
its reaction with oxygen as an ion thermometric probe. Photoexcitation at 1064 nm was used to prepare highly vibrationally
excited Cr(CO)5−. Although the overall oxidation rate changes only slightly upon excitation (actually decreasing by a factor of 1.2 ± 0.1), the primary product distribution shifts dramatically, from Cr(CO)3O− (the thermodynamic product) to Cr(CO)3O2− (the kinetic product). The two-pulse photodissociation measurement gave a radiative relaxation rate constant (k
rad) of 15 ± 2 s−1, whereas the branching ratio experiments gave a k
rad value of 3. 3 ± 0.7 s−1. The large difference between these two values is due to the difference in Cr(CO)5− internal energy ranges probed by the two techniques. In the high internal energy regime interrogated by the two-pulse measurements
(about 12,000 to 6000 cm−1), the strongly emitting C-O stretching modes are populated and contribute to fast relaxation. In contrast, the branching
ratio measurements remain sensitive to internal energy changes all the way down to thermal energies, where the C-O stretches
are depopulated and thus unavailable for radiative relaxation. 相似文献
14.
Hui-fang Du An-you Zhang Zhu-xian Yang Zu-ming Zhou 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(1):241-243
The solvent extraction of U(VI) by p-tert-butylcalix[n]-arene acetate (H
n
L) (n=4, 6, 8) has been studied. The effects of acidity in aqueous phase and concentration of extractant in organic phase on the
distribution ratio were examined. It has been found that the distribution ratio is proportional to [H+]−2 and [H
n
L](O) and the extracted complex species is UO2H
n
−2L. The equilibrium constants of the extraction reactions have been determined. The reaction mechanism is discussed. 相似文献
15.
O. G. Shakirova L. G. Lavrenova N. V. Kurat’eva D. Yu. Naumov V. A. Daletskii L. A. Sheludyakova V. A. Logvinenko S. F. Vasilevskii 《Russian Journal of Coordination Chemistry》2010,36(4):275-283
Mononuclear iron(II) coordination compounds with tris(pyrazol-1-yl)methane (HC(Pz)3) described as [Fe{HC(Pz)3}2]A2 × nH2O, where A = Cl−, Br−, I−, 1/2 SO42−, n = 0–7, were synthesized. The compounds were studied by static magnetic susceptibility measurements, IR and UV/Vis spectroscopy,
and powder X-ray diffraction. The crystal and molecular structures of all compounds were determined by single crystal X-ray
diffraction. 相似文献
16.
V. D. Kiselev E. A. Kashaeva M. S. Shihab M. D. Medvedeva A. I. Konovalov 《Russian Chemical Bulletin》2000,49(6):1040-1044
The partial molar volumes (V) and the enthalpies of dissolution (Δdis
H) for tetracyanoethylene, cyclopentadiene, and their Diels—Alder adduct were determined at 25°C. Eleven solvents of the π-
and n-donor type were used. The use of alkylbenzenes as solvents for tetracyanoethylene induces pronounced changes in the
enthalpy of dissolution (up to 26 kJ mol−1) and in the partial molar volume (up to 11 cm3 mol−1), whereas these parameters for the adduct change slightly. TheV and Δdis
H values for cyclopentadiene virtually do not depend on the nature of the solvent. In the case of tetracyanoethylene and the
adduct in n-donor solvents, considerable variations of theV and Δdis
H values are observed; they are not linear functions of the change in the partial molar volume of the adduct. Therefore, the
reaction volumes in acetonitrile (−40.69) and ethyl acetate (−45.56) differ sharply from those ino-xylene (−24.28) and mesitylene (−21.76 cm3 mol−1).
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1046–1050, June, 2000. 相似文献
17.
Effect of a Carboxylic Group on the Conformational Properties of Some Gemini Surfactants 总被引:1,自引:0,他引:1
Paweł Misiak Bożenna Różycka-Roszak Anna Mozrzymas Emilia Fisicaro 《Journal of solution chemistry》2007,36(7):845-851
Molar volumes of derivatives of N,N-bisdimethyl-1,2-ethanediamine of general formula [C
n
H2n+1OOCCH2(CH3)2N+CH2CH2N+(CH3)2CH2COOC
n
H2n+1]2Cl− (bis-C
n
BEC), and betaine ester derivatives of general formula N+(CH3)3CH2COOC
n
H2n+1Cl− (C
n
BEC), were calculated by means of molecular connectivity indices and an additivity scheme. The COO group contribution in the
β-position to the molar volume of bis-C
n
BEC was found from experimental data to be significantly lower from that for C
n
BEC and was estimated to be 13.5 cm3⋅mol−1. It is suggested that this effect is due to hydrogen bonding between the carboxyl groups via water molecules. Molecular dynamics
simulations of bis-C12BEC and 14–2–14 molecules in water were performed and suggest that the upper part of the bis-C12BEC, containing the carboxyl groups, is stiffened by its hydration shell. 相似文献
18.
Botelho J. R. Souza A. G. Nunes L. M. Chagas A. P. Garcia dos Santos I. M. da Conceição M. M. Dunstan P. O. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):413-417
The standard molar enthalpies of formation of crystalline dialkyldithiocarbamates chelates, [Pd(S2CNR2)2], with R=C2H5, n-C3H7, n-C4H9 and i-C4H9, were determined through reaction-solution calorimetry in acetone, at 298.15 K. From the standard molar enthalpies of formation
of the gaseous chelates, the homolytic (172.4±3.8, 182.5±3.2,150.9±3.1 and 162.6±3.1 kJ mol−1) and heterolytic (745.0±3.8, 803.7±3.3,834.3±3.1 and 735.2±3.0 kJ mol−1) mean palladium-sulphur bond-dissociation enthalpies were calculated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Six new μ-terephthalato iron(III) binuclear complexes have been prepared and identified: [Fe2(TPHA)(L)4]-(ClO4)4 [L = 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me2bpy); 5-methyl-1,10-phenanthroline (Me-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-nitro-1,10-phenanthroline (NO2-phen)]; where TPHA = the terephthalate dianion. Based on the elemental analyses, molar conductance and magnetic moments of
room-temperature measurements, and spectroscopic studies, extended TPHA-bridged structures consisting of two iron(III) ions,
each in an octahedral environment, are proposed for these complexes. The [Fe2(TPHA)(Me-phen)4](ClO4)4
(1) and [Fe2(TPHA)(phen)4](ClO4)4
(2) complexes were characterized by variable temperature magnetic susceptibility (4–300 K) measurements and the observed data
were successfully simulated by the equation based on the spin Hamiltonian operator, Ĥ = −2JŜ
1
Ŝ
2, giving the exchange integrals J = −1.05 cm−1 for (1) and J = −9.28 cm−1 for (2). This result indicates the presence of a weak antiferromagnetic spin-exchange interaction between the metal ions within each
molecule. The influence of the terminal ligand methyl substituents on magnetic interactions between the metals is also discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
Małgorzata Pazderska-Szabłowicz Agnieszka Białkowska Ewa Kita 《Transition Metal Chemistry》2006,31(3):413-420
New chromium(III) complexes, [Cr(C2O4)2(2-hnic)]2− and [Cr(C2O4)2(3-hpic)]2− (where 2-hnic = O,O′-bonded 2-hydroxynicotinic acid and 3-hpic = N,O-bonded 3-hydroxypicolinic acid), were obtained and characterized
in solution. The acid-catalyzed aquation of the both complexes leads to liberation of the appropriate pyridinecarboxylic acid
and formation of cis-[Cr(C2O4)2(H2O)2]−. Kinetics of these reactions were studied spectrophotometrically in the 0.1–1.0 M HClO4 range, at I = 1.0 M. In the case of [Cr(C2O4)2(2-hnic)]2−, a slow chelate-ring opening at the Cr–O (phenolate) bond is followed by a fast Cr–O (carboxylate) bond breaking. The rate
law: kobs = kHQH[H+] was established, where kH is the acid-catalyzed rate constant and QH is the protonation constant of the coordinated phenolate oxygen atom. In the case of [Cr(C2O4)2(3-hpic)]2−, the reversible chelate-ring opening at Cr–N bond is followed by the rate determining step – the one-end bonded ligand liberation.
The rate law for the first step was determined: kobs = k1+k−1/Q1[H+], where k1 and k−1 are the rate constants of the chelate-ring opening and closure and Q1 is the protonation constant of the pyridine nitrogen atom. The aquation mechanisms are proposed and the effect of ligand
coordination mode on complex reactivity is discussed. 相似文献