- Spin-State-Dependent Redox-Catalytic Activity of a Switchable Iron(II) Complex
-
The spin state of catalytically active 3d metal centers plays a significant role in their activity in enzymatic processes and organometallic catalysis. Here the catalytic activity of an FeII coordination compound that can undergo a cooperative switch between low-spin (LS) and high-spin (HS) states is reported. Catalytic measurements in the temperature range 291–318 K revealed a drastic drop of the catalytic activity on conversion of the metal centers from the LS to the HS form. For thermoswitchable complex [Fe(NH2trz)3]Br2 (NH2trz = 4-amino-1,2,4-tiazole; Tup = 305 K), the activation energy is found to be considerably lower for the LS state (158 kJ mol–1) compared to the HS state (305 kJ mol–1). M?ssbauer analysis revealed that this is related to higher conversion of the LS complex on oxidation. Comparisons with another polymorph of [Fe(NH2trz)3]Br2 (Tup = 301 K) and [Fe(NH2trz)3](ClO4)2 (Tup = 240 K) are made. These results show the potential of spin-crossover compounds to compare the catalytic activity of different spin states of the same material when other means of differentiation are limited.
- Gural'skiy, Il'ya A.,Shylin, Sergii I.,Ksenofontov, Vadim,Tremel, Wolfgang
-
-
Read Online
- Synthetic method for chlormadinone acetate drug intermediate o-tetrachlorobenzoquinone
-
The invention discloses a synthetic method for the chlormadinone acetate drug intermediate o-tetrachlorobenzoquinone. The synthetic method comprises the following steps: adding 2,3-dihydroxy-4,5,6-trichloro-aniline and a cyclohexane solution into a reaction vessel, slowly increasing a temperature, then adding a potassium sulfate solution, and carrying out a reaction; and continuing to add a 2,3-dichloropropene solution, lowering the temperature, adding tricarbonylcyclopentadienyl manganese in batches, controlling a stirring speed, continuing the reaction, subjecting the obtained solution to layering, lowering the temperature, carrying out washing with a sodium chloride solution a plurality of times, then carrying out washing with an ethylene oxide solution a plurality of times, then carrying out washing with a 1,4-dichlorobutane solution a plurality of times, carrying out recrystallization in a dichloropentane solution, and then carrying out dehydration with a dehydrating agent so as to obtain the finished o-tetrachlorobenzoquinone.
- -
-
Paragraph 0014; 0019; 0020; 0023; 0024; 0025; 0027; 0028
(2018/07/30)
-
- Effect of oxalate and pH on photodegradation of pentachlorophenol in heterogeneous irradiated maghemite System
-
Photochemical degradation in the system of iron oxides and oxalic acid (OX) is the important reaction for detoxification of organic pollutants in natural environments, including surface soils, surface water, and even aerosols, and it was more effective at low pH according to previous studies. However, in this study, the photodegradation of pentachlorophenol (PCP) proceeded rapidly at different pH conditions in the system with maghemite and OX under UV light illumination. It was observed that the removal of PCP was 77.7% ± 0.90%, 79.9% ± 0.80% and 74.3% ± 1.50% at initial pH of 3.5, 5.0 and 7.0, respectively. To explore the degradation mechanism, the interaction of OX and maghemite were systematically studied as a function of pH. The presence of OX of 1.2 mM effectively decreased the iso-electric point (iep) of the maghemite from 5.6 to 1.8. The maximum adsorption amount of maghemite adsorbing OX increased with increasing pH value from 208 mmol kg-1 at pH = 3.5 to 293 mmol kg-1 at pH = 9.0. However, PCP (0.0375 mM) inhibited the adsorption of oxalic acid at pH = 3.5 and pH = 5.0 but promoted it at pH = 7.0 and pH = 9.0. When the initial content of OX was 1.2 mM, the highly active compounds of Fe(C2O4)33- as Fe(III) and Fe(C2O4)22- as Fe(II) were the dominant species at different pH. The formation of H2O2 also relied on the value of pH and the concentration range of H2O2 during PCP degradation was 0-1.67 mg L-1, 0-1.16 mg L-1 and 0-0.16 mg L-1at initial pH of 3.5, 5.0 and 7.0, respectively. The low pH conditions favored the iron cycling, the H2O2 generation and the broken of aromatic ring of PCP, so as to enhance the degradation rates of PCP. At the high pH conditions, due to the slowdown of the iron cycling and the decreased amount of H2O2 formation, the direct photolysis was responsible for the enhanced degradation of PCP. The foundation of high photochemical efficiencies of OX and maghemite for PCP degradation at large-scale pH conditions improves the photochemical mechanisms of OX-iron oxide system and is of important for understanding the transformation of organic pollutants in light environments.
- Lan, Qing,Cao, Meiyuan,Ye, Zhijun,Zhu, Jishu,Chen, Manjia,Chen, Xuequan,Liu, Chengshuai
-
p. 198 - 206
(2016/07/06)
-
- Dinuclear cobalt(II) complexes of Schiff-base compartmental ligands: Syntheses, crystal structure and bio-relevant catalytic activities
-
Three dicobalt(II) complexes, namely [Co2(L1H)(H 2O)2(OAc)2](OAc)2 (1), [Co2(L 2)(H2O)2(OAc)2](OAc)(2) and [Co 2(L3)(H2O)2(OAc)2](OAc) (3) of the p-cresol based "end-off" compartmental ligands 2,6-bis(R-iminomethyl)- 4-methyl-phenolato, where R = N-ethylpiperazine for L1, 2-ethylpyridine for L2 and N-ethylpiperidine for L3, have been synthesized and characterized by common physicochemical techniques, and in the case of complex 1 also by single crystal X-ray diffraction analysis. All the complexes show excellent catecholase-like activity, monitored not only with 3,5-di-tert-butylcatechol but also with tetrachlorocatechol, a substrate reluctant to be oxidized. To the best of our knowledge, to date no cobalt complex has been found in the literature to manifest such activity. The complexes are observed to interact efficiently with CT-DNA and on incubation (employing plasmid pTZ57/R/T DNA) they exhibit concentration dependent DNA cleavage activity. The mechanisms related to the DNA cleavage and catecholase-like activities have been investigated. The cytotoxicity of the complexes has also been examined through an MTT assay.
- Banerjee, Arpita,Guha, Averi,Adhikary, Jaydeep,Khan, Amitava,Manna, Krishnendu,Dey, Sanjit,Zangrando, Ennio,Das, Debasis
-
supporting information
p. 102 - 109
(2013/07/26)
-
- A unique nickel system having versatile catalytic activity of biological significance
-
A new dinuclear nickel(ll) complex, [Ni2(LH2)(H 2O)2(OH)(NO3)](NO3)3 (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine- iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-ditert-buty !catechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV-vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.
- Chattopadhyay, Tanmay,Mukherjee, Madhupama,Mondal, Arindam,Maiti, Pali,Banerjee, Arpita,Banu, Kazi Sabnam,Bhattacharya, Santanu,Roy, Bappaditya,Chattopadhyay,Mondai, Tapan Kumar,Nethaji, Munirathinam,Zangrando, Ennio,Das, Debasis
-
scheme or table
p. 3121 - 3129
(2010/05/14)
-
- Toxicity changes during the UV treatment of pentachlorophenol in dilute aqueous solution
-
Pentachlorophenol (PCP) was photolysed using a 1 kW photochemical reactor. The degradation of PCP (0.15 mM) was carried out using both direct UV photolysis and photolysis in the presence of H2O2 (3.0, 6.7, 18.0 and 37.2 mM). The decay of PCP and the formation of photoproducts were followed by high performance liquid chromatography, ion chromatography and UV absorbance detection. The first-order rate constants k1 for the decay of PCP were estimated under various conditions: for direct UV photolysis, k1 = 0.115 min-1; for photolysis in the presence of various concentrations of H2O2, the rate constant increased to a plateau (k1 ? 0.7 min-1) at H2O2 concentrations greater than 6 mM. The correlation between photodegradation and toxicity was studied using a bacterial toxicity test and a 96 h Fathead Minnow toxicity test. In both cases, the toxicity decreased as the concentration of PCP or the total organic chlorine concentration fell. These results indicate that the UV treatment of PCP either does not generate significant levels of acutely toxic intermediates, or any toxic intermediates are rapidly degraded under the specific conditions used in these studies. Pentachlorophenol (PCP) was photolysed using a 1 kW photochemical reactor. The degradation of PCP (0.15 mM) was carried out using both direct UV photolysis and photolysis in the presence of H2O2 (3.0, 6.7, 18.0 and 37.2 mM). The decay of PCP and the formation of photoproducts were followed by high performance liquid chromatography, ion chromatography and UV absorbance detection. The first-order rate constants k1 for the decay of PCP were estimated under various conditions: for direct UV photolysis, k1 = 0.115 min-1; for photolysis in the presence of various concentrations of H2O2, the rate constant increased to a plateau (k1≈0.7 min-1) at H2O2 concentrations greater than 6 mM. The correlation between photodegradation and toxicity was studied using a bacterial toxicity test and a 96 h Fathead Minnow toxicity test. In both cases, the toxicity decreased as the concentration of PCP or the total organic chlorine concentration fell. These results indicate that the UV treatment of PCP either does not generate significant levels of acutely toxic intermediates, or any toxic intermediates are rapidly degraded under the specific conditions used in these studies.
- Ho, Te-Fu L.,Bolton, James R.
-
p. 489 - 497
(2007/10/03)
-
- Method for dyeing keratinous fibres using an aminoindole in combination with a quinone derivative
-
Method for dyeing keratinous fibres, characterized in that at least one composition (A) containing at least one aminoindole in a medium appropriate for dyeing is applied to these fibres, the application of the composition (A) being preceded or followed by the application of a composition (B) containing, in a medium appropriate for dyeing, at least one quinone derivative chosen from ortho- or para-benzoquinones, ortho- or para-benzoquinone monoimines or diimines, 1,2- or 1,4-naphthoquinones, ortho- or para-benzoquinone sulphonimides, α,ω-alkylene-bis-1,4-benzoquinones, or 1,2- or 1,4-naphthoquinone monoimines or diimines, the aminoindoles and the quinone derivatives being chosen such that the difference in redox potential ΔE between the redox potential Ei of the aminoindoles, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the redox potential Eq of the quinone derivative, determined at pH 7 in a phosphate medium by polarography on a mercury electrode relative to the saturated calomel electrode, in such that
- -
-
-
- The Nitration of Tetrachlorocatechol and 3,4,6-Trichloro-5-methylcatechol. The Formation of 1-Hydroxycyclopent-3-enecarboxylic Acids
-
Reaction of tetrachlorocatechol (1a) with nitric acid (d 1.48) gives the ring-contracted hydroxy dinitro acid (4), which was isolated as its ether solvate.Similar nitration of 3,4,6-trichloro-5-methylcatechol (1b) gives a mixture of stereoisomeric hydroxy dinitro acids (5), from which the methoxy methyl ester (8) can be isolated after methylation of the mixture with diazomethane.X-Ray crystal structure determinations are reported for the etherate of hydroxy dinitro acid (4) and the methoxy methyl ester (8).
- Calvert, Jane L.,Gordon, James L. M.,Hartshorn, Michael P.,Robinson, Ward T.,Wright, Graeme J.
-
p. 713 - 719
(2007/10/02)
-
- Process for dyeing keratinous fibres with a hydroxyindole in combination with a quinone derivative; and novel 1,4-benzoquinones
-
Process for dyeing keratinous fibres, comprising the step of applying to these fibres at least one composition A containing, in a medium appropriate for dyeing, at least one mono- or di-hydroxyindole the application of the composition A being preceded or followed by the application of a composition B containing, in a medium appropriate for dyeing, at least one quinone derivative chosen from ortho- or para-benzoquinones, monoimines or diimines of ortho- or para-benzoquinones, 1,2- or 1,4-naphthoquinones, sulphonimides of ortho- or para-benzoquinones, α, ω-alkylene-bis-1,4-benzoquinones, or 1,2- or 1,4-naphthoquinone-monoimines or -diimines; the mono- or di-hydroxyindoles and the quinone derivatives being chosen such that the oxidation-reduction potential difference ΔE between the oxidation-reduction potential Ei of the mono- or di-hydroxyindoles, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the oxidation-reduction potential Eq of the quinone derivative determined at pH 7 in a phosphate medium by polarography on a mercury electrode and relative to a saturated calomel electrode is such that
- -
-
-
- A defense Mechanism against Pathogenic Bacteria in the Digestive Tracts of Silkworm Larvae-in vitro Evidence of the Formation of Caffeoquinone, a True Antibacterial Substance, and Synergism of Amino Compounds
-
For the defense mechanism against pathogenic bacteria in the digestive tracts of silkworm larvae reared on mulberry leaves, in vitro evidence of the formation of atrue antibacterial substance was obtained. caffeic acid (CA) derived from chlorogenic acid (ChA)was converted into caffeoquinone (CQ) by base-catalyzed oxidation in a buffer solution (pH 10.0).CQ was trapped as 6'phenylsulfonylcaffeic acid (6'sulfone) by the addition of benzenesulfinic acid (BSA).The synergetic effects of amino compounds on the antibacterial activity of CQ are discussed in detail, and the probable reactions of CA with amino and thiol compounds in the alkaline solution are proposed.
- Nakano, Hidenori,Tahara, Satoshi,Iizuka, Toshihiko,Mizutani, Junya
-
p. 549 - 556
(2007/10/02)
-
- THE REACTION OF TETRACHLORO-o-BENZOQUINONE WITH THE SULFIDES OF TRIPHENYLARSINE AND TRIPHENYLSTIBINE
-
The reaction of tetrachloro-o-benzoquinone (1) with triphenylarsine sulfide gives a hydrogen-bonded complex of the corresponding hydroquinone and triphenylarsine oxide (5).The same quinone reacts with triphenylstibine sulfide yielding the cyclic adduct (9).In both cases, elemental sulfur is the other product.Possible reaction mechanisms are considered and the structural assignments are based on analytical, chemical and spectroscopic results.
- Sidky, M. M.,Mahran, M. R.,Abdou, W. M.
-
p. 129 - 136
(2007/10/02)
-
- Carbonyl and Thiocarbonyl Compounds: Part XV-Synthesis of Spiro and Quinazolinone Anils
-
Tetrachloro-o-benzoquinone reacts with 2,3-diarylquinazoline-4(3H)-thiones (4a-c) to give spiro (5).The latter are cleaved with mineral acids to give 2,3-diarylquinazolin-4(3H)-ones (4d-f).Reaction of 5 with anilines affords the hitherto unknown quinazolinoneanils (6) together with tetrachlorocatechol.Reaction mechanisms are discussed.
- Latif, N.,Mishriky, N.,Assad, Fahmy M.
-
p. 118 - 120
(2007/10/02)
-
- Nitrations and Oxidations with Inorganic Nitrate Salts in Trifluoroacetic Anhydride
-
Metal nitrates in trifluoroacetic anhydride nitrate many aromatic compounds in high yields at room temperature, including polymers with aromatic groups.However, this system oxidizes phenols to quinoid products.
- Crivello, J.V.
-
p. 3056 - 3060
(2007/10/02)
-
