　本文合成了对甲苯磺酸铜,并应用热重(TG)和差示扫描量热法(DSC)进行分析.该铜盐容易脱除全部结晶水,且在空气中不潮解,如与乙醇胺形成等摩尔配合物,则在DMSO和DMF溶剂中能催化1,1′ 联 2 萘酚的氧化,但在H2O或CH3OH溶剂中则不发生反应.此外,还分别研究了该铜盐及其它铜盐与乙醇胺(1∶1)的配合物在DMSO、DMF、CH3OH和H2O中的电化学行为和催化活性.实验表明,铜胺配合物的两步单电子还原过程对催化氧化1,1′ 联 2 萘酚是必要的条件.Copper (II) paratolysulfate has been synthesized and characterized by thermo-gravimetric (TG) measurements and differential scanning calorimetric (DSC) analysis. This salt can easily lose all crystal water and the dehydrated salt does not deliquesce in the air. It is found for the first time that the complex of Cu(p-OTs)_(2)/ethanolamine(1∶1) can catalyze the oxidation of 1,1′-bi-2-naphthol in DMSO and DMF, while the process is difficult to perform in H_(2)O and CH_(3)OH. The electrochemical behaviors of both Cu(p-OTs)_(2) and its complexes with ethanolamine have been studied on platinum electrode in DMSO, DMF, (CH_(3)OH) and H_(2)O respectively. The complexes of various copper salts with ethanolamine are also studied by cyclic voltammetry in different solvents. It is concluded that the two one-electron steps are essential condition for the oxidation of 1,1′-bi-2-naphthol.作者联系地址：中山大学理工学院光电材料与技术国家重点实验室,中山大学理工学院光电材料与技术国家重点实验室 广东广州510275 ,广东广州51027

SHEN Pei-kang

SONG Ji-guo

宋继国

沈培康

Xiamen University Institutional Repository

第 10 卷 　第 3 期2004 年 8 月电化学ELECTROCHEMISTRYVol. 10 　No. 3Aug. 2004Article ID :100623471 (2004) 0320271208Studies on the Electrochemical Behavior ofCopper Paratolysulfate and its ComplexesSONGJi2guo , SHEN Pei2kang 3( The State Key Lab of Optoelectronic Materials and Technologies , School ofPhysics and Engineering , Sun Yat2sen University , Guangzhou 510275 , China)Abstract : Copper ( II) paratolysulfate has been synthesized and characterized by thermo2gravimetric(TG) measurements and differential scanning calorimetric (DSC) analysis. This salt can easily lose allcrystal water and the dehydrated salt does not deliquesce in the air. It is found for the first time that thecomplex of Cu( p2OTs) 2/ ethanolamine (1∶1) can catalyze the oxidation of 1 ,1′2bi222naphthol in DMSOand DMF , while the process is difficult to perform in H2O and CH3OH. The electrochemical behaviors ofboth Cu( p2OTs) 2 and its complexes with ethanolamine have been studied on platinum electrode in DM2SO , DMF , CH3OH and H2O respectively. The complexes of various copper salts with ethanolamine arealso studied by cyclic voltammetry in different solvents. It is concluded that the two one2electron steps areessential condition for the oxidation of 1 ,1′2bi222naphthol .Key words :Copper paratolysulfate , Mimetic enzyme , Electrochemistry , 1 ,1′2bi222naphtholCLC Number : O 646 Document Code : A1 　IntroductionCopper complexes are involved in variety of important biochemical process , such as oxygen transportand oxygen activation by oxidase and monooxygenase enzymes[1 ] . Synthesis and characterization of low2molecular weight analogs for the active sites of metalloproteins is receiving increasing attention worldwide.Some copper complexes with different type of ligands have been synthesized and studiedas mimetic enzyme[2 ,3 ] . As a rule , their redox properties have been investigated by electro 2Received date : 2003212224 , accepted date : 2004202220To whom correspondence should be addressed ,Tel :(86220) 84113369 ,E2mail :stdp32 @zsu. edu. cnGuandong Province Project(2003B12006 ,013024) , Guangzhou Science and Technology Project (2003Z22D0081) supported© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.netchemical techniques , especially the cyclic voltammetry (CV) in appropriate solvents[4 ,5 ] . It is recentlyreported that the complex of CuCl2/ ethanolamine (1∶1) can catalyze the oxidation of 1 ,1′2bi2 22naphtholin methanol with high yield[6 ] .In the present paper we report that copper paratolysulfate (Cu ( p2OTs) 2) can lose all the crystal wa2ter easily and the dehydrated salt does not deliquesce in the air. Preliminary study showed that the com2plex of Cu( p2OTs) 2/ ethanolamine (1∶1) could catalyze the oxidation of 1 ,1′2bi222naphthol by O2 in DM2SO and DMF. The product was peri2xanthenoxanthene in accord with the result catalyzed by CuCl2/ethanolamine (1∶1) in the same solvent [6 ] . However , the catalytic reaction could hardly proceed in CH3OH and H2O.The work on the electrochemical behavior of both Cu( p2OTs) 2 and its complexes with ethanolamineis also reported here. This study is undertaken with the purpose of investigating the effect of solvents onthe redox and catalytic properties of Cu( p2OTs) 2 and analyze the reaction mechanism.2 　Experimental2. 1 　ApparatusThermogravimetric (TG) analyses and differential scanning calorimetric (DSC) analyses were carriedout with NETZSCH TG 209 Thermogravimetric analyzer and Perkin2Elmer Differential Scanning Calorime2ter , respectively. 1H NMR was recorded in a Varian Unity INOVA2500 spectrometer in CDCl3 with TMSas the internal standard. Mass spectra (MALDI2TOF2MS) was taken on REFLEX 3 Bruker matrix assist2ed laser desorption/ ionization time of flight mass spectrometry. The electrochemical measurements werecarried out on a French VoltaLab 80 electrochemical workstation (Radiometer Analytical) . The workingelectrode was a Pt (99. 9 %) wire (0. 073 cm2) and the counter electrode was a Pt (99. 9 %) sheet .The saturated calomel electrode (SCE) was used as reference electrode. All the potential values in thispaper are versus SCE. Purified argon was bubbled through the electrolytic solution to remove oxygen. Theelectrochemical measurements were carried out in an argon atmosphere.2. 2 　ReagentsDimethyl sulfoxide (DMSO , AR) and N ,N2Dimethylformamide (DMF , AR) and CH3OH was dis2tilled under vacuum after added 0. 4 nm molecular sieves to remove water. The supporting electrolyte te2trabutyl ammonium perchlorate ( ( n2Bu) 4NClO4 or TBAP) was prepared following the literature[7 ] . Cop2per paratolysulfate was prepared by the reaction of CuO (99. 95 %) and p2CH3C6H4SO3H·H2O (AR) .The hydrated salt was dehydrated at 120 ℃under 0. 51 kPa and preserved in a desiccator containing an2hydrous CaCl2 for using in the electrochemical experiments. Unless stated otherwise , all the reagents wereanalytical pure. Aqueous solutions were prepared by double distilled water.·272· 电 　化 　学 　　　　　　　　　2004 年© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.net2. 3 　Catalytic Oxidation of 1 ,1′2bi222naphthol with Cu( p2OTs) 2/ ethanolamine　( 1∶1) as Mimetic EnzymeA 50 mg ( 0. 17 mmol ) sample of 1 , 1′2bi222naphthol was added to a flask containing 2 mLDMSO(or DMF) solution of 0. 01 mol/ L Cu( p2OTs) 2/ ethanolamine (1∶1) complex dissolved in 20 mL ofDMSO(or DMF) . The solution was stirred at 60 ℃and oxygen was bubbled through the solution. Thereaction was allowed to take place until the oxygen consumption had ceased. A 2 mL ammonia solutionand 50 mL water were added to the solution and extracted with chloroform (3 ×10 mL) . The peri2xan2thenoxanthene (10. 5 mg , 21 % yield) oxidation product was then isolated by evaporation of CHCl3 driedby anhydrous CaCl2 followed by column chromatography on silica gel using petroleum ether∶ethyl acetate(10∶1 , V∶V) as eluant . 1H NMR (CDCl3)∶δ (10- 6 from TMS) 6. 63～6. 65 (m , 2H , 12H , 72H) , 6. 91(d , 2H , J = 9. 2Hz , 32H , 92H) , 7. 0727. 09 (m , 4H , 22H , 52H , 82H , 112H) , 7. 29 (d , 2H , J = 8.9Hz , 42H , 102H) . MALDI2TOF2MS : 283 ( [M + H] + ) .The complex of Cu( p2OTs) 2/ ethanolamine (1∶1) precipitated from aqueous solution. The oxidationof 1 ,1′2bi222naphthol could not take place in CH3OH and H2O (monitored by thin layer chromatography ,TLC) under the same condition as in DMSO (or DMF) since the 1 ,1′2bi222naphthol does not dissolve inH2O.3 　Results and Discussion3. 1 　Analysis of Copper ParatolysulfateTwo endothermic peaks (58. 1186. 6 ℃) and two exothermic peaks (292. 8～481. 7 ℃) were foundfrom the DSC curve analysis of the salt in the temperature range of 30630 ℃as shown in Fig. 1. The TGcurve showed four weight lose processes. The first two peaks are owing to water loss ; according to the val2ues of weight loss on the TG curve , the numbers of water molecules lost were calculated as 4 and 2 re2spectively. Therefore , the freshly prepared copper paratolysulfate should has the molecular formula of Cu( p2CH3C6H4SO3) 2·6H2O , this is also proved by X2ray crystal structure. The DSC and TG experimentsshowed that this salt can lose all crystal water easily and the dehydrated salt does not deliquesce in theair. Hence , the Cu( p2OTs) 2 is suitable for the electrochemical studies in nonaqueous solvents.·372·第 3 期 　　　　　　　宋继国等 :对甲苯磺酸铜及其配合物的电化学行为研究© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.net3. 2 　The Electrochemical Behavior of Cu( p2OTs) 2 in H2OThe cyclic voltammograms of Pt electrode in Cu ( p2OTs) 2/ KCl aqueous solution at different scanrates were shown in Fig. 2. There were two pairs of redox peaks as shown in the figure. The surface of Ptelectrode kept clean after 5 min electrolysis at the potential of 0. 1 V (at the first cathodic peak) ; howev2er , red color appeared on the Pt electrode after 5 min electrolysis at the potential of - 0. 2 V (at the sec2ond cathodic peak) . It was proved that the electrochemical reduction of Cu( p2OTs) 2 in aqueous solutionwas through two steps. The CV curves changed a little after added equivalent ethanolamine in Cu( p2OTs) 2/ KCl aqueous solution.3. 3 　The Electrochemical Behavior of Cu( p2OTs) 2 in CH3OHIn Fig. 3 curve a shows the cyclic voltammogram of Cu( p2OTs) 2/ TBAP/ CH3OH on Pt electrode.Only one pair of redox peak on the curve was found. Yellow compact deposit was appeared on the surfaceof Pt electrode after 5 min electrolysis at the cathodic peak potential . It is obvious that the peaks are cor2responding to the cathodic reduction of Cu ( II) to Cu and the anodic oxidation of Cu. Therefore , the re2sult revealed that the electrochemical reduction of Cu( p2OTs) 2 in CH3OH was through one step .The electrochemical reduction of Cu ( p2OTs) 2 was also a one step process after added equivalentethanolamine (see Fig. 3b) .3. 4 　The Electrochemical Behavior of Cu( p2OTs) 2 in DMSOIn Fig. 4 ,curve a shows the cyclic voltammogram of Cu( p2OTs) 2/ TBAP/ DMSO on Pt electrode atscan rate of 100 mV·s - 1 . There are two pairs of redox peaks on the curve , indicating that the first ca2thodic peak was due to the reduction of Cu( II) to Cu ( I) and the second cathodic peak was the reductionof Cu ( I) to Cu. Curve b is the cyclic voltammogram of Cu( p2OTs) 2/ TBAP/ DMSO after adding equiva2·472· 电 　化 　学 　　　　　　　　　2004 年© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.netlent ethanolamine. There are appeared two pairs of peaks. Both of two cathodic peaks shifted to morepositive potentials. The first peak potential positively changed 351 mV and the second one changed 238mV.3. 5 　The Electrochemical Behavior of Cu( p2OTs) 2 in DMFOne step mechanism was also found in Cu( p2OTs) 2/ TBAP/ DMF system. The cyclic voltammogramof Cu ( p2OTs) 2/ TBAP in DMF is shown in Fig. 5a. Only one pair of cathodic peak and anodic peak ap2peared. Black compact deposited on the electrode surface after 5min galvanostatic electrolysis at the ca2thodic peak potential . However , the one step process changed to two steps processes for the system of Cu( p2OTs) 2/ TBAP/ DMF after added equivalent ethanolamine. Two cathodic peaks (at 202 mV and - 105mV) and one anodic peak (188 mV) appeared in Fig. 5b. Both of the cathodic peak potential moved pos2itively compared with Fig. 5a ( - 216 mV) and the anodic peak potential moved negatively compared withFig. 5a (233 mV) .Cu ( II) can be solvated by DMF better than by CH3OH , therefore , the oxidation of Cu is easier inDMF than that of in CH3OH which resulting in the more negative anodic peak in DMF compared with thatin CH3OH. The reductive process became two steps processes by the addition of ethanolamine is probablydue to the strong coordination power between solvated Cu( II) and the amino of ethanolamine.3. 6 　Studies of Cu( p2OTs) 2/ ethanolamine( 1∶1) as Mimetic EnzymeThe derivatives of xanthone are widely existed in natural products and have many physiological activ2ities[8 ] . This work aims to use the complex of Cu( p2OTs) 2/ ethanolamine (1∶1) as mimetic enzyme to syn2thesize physiologically active compounds and research the reactive mechanism.·572·第 3 期 　　　　　　　宋继国等 :对甲苯磺酸铜及其配合物的电化学行为研究© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.net　Fig. 5 　The CV curves of the 0. 05mol·L - 1TBAP + 0.012mol·L - 1 Cu( p2OTs) 2 in DMF (a) and afteradded 0. 012 mol L - 1 ethanolamine(b) 　t : 298K, scan rate : 0. 1 V·s - 1In the present work , Cu ( p2OTs ) 2/ethanolamine ( 1 ∶1) was applied for the catalyticreactions. The preliminary results showed that thecomplex of Cu ( p2OTs) 2/ ethanolamine (1∶1) couldcatalyze the oxidation of 1 ,1′2bi222naphthol in DM2SO and DMF but could not work in CH3OH and H2O. In all the cases , the solution became brown incolor and small quantity of brown precipitation pro2duced after added Cu ( p2OTs) 2/ ethanolamine (1∶1)into 1 , 1′2bi222naphthol as reported in the litera2ture[6 ] . The precipitation disappeared at the end ofthe reaction in DMSO and DMF , but kept the samein CH3OH and H2O. By comparing the CV curvesof Cu ( p2OTs) 2/ ethanolamine (1∶1) in the four solu2tions , it was found that the electrochemical reduc2tion of Cu( p2OTs) 2/ ethanolamine (1∶1) is a two one2electron processes in DMSO and DMF. In that case ,Cu( p2OTs) 2/ ethanolamine (1∶1) acts as a mimetic enzyme to catalytically oxidize 1 ,1′2bi222naphthol .However , the process is a one two2electron reaction in CH3OH , which can hardly work for the 1 ,1′2bi222naphthol oxidation.Tab. 1 　Performance of cupric salt/ ethanolamine (1∶1) complexes in different solventsCupric salt Solvents Electrochemical reduction 1 ,1′2bi222naphthol oxidationCuCl2 H2O Two steps NoDMSO Two steps YesCH3OH Two steps YesCuBr2 H2O Two steps NoCH3OH Two steps YesCuSO4 H2O Two steps NoCH3OH One step NoCu( p2OTs) 2 H2O Two steps NoDMSO Two steps YesCH3OH One step NoDMF Two steps YesCu(AcO) 2 H2O Two steps NoCH3OH One step NoCu(NO3) 2 H2O Two steps NoCH3OH One step NoCu(ClO4) 2 H2O Two steps NoCH3OH One step NoThe complexes of various copper salts with ethanolamine have been tested and summarized in Table1. The complexes that the reduction proceeds by two steps can be used as mimetic enzyme , the complexesthat the reduction is through one step can not catalyze the oxidation of 1 ,1′2bi222naphthol . So the oxida2·672· 电 　化 　学 　　　　　　　　　2004 年© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.nettion of 1 ,1′2bi222naphthol catalyzed by Cu( II) / ethanolamine is carried out by the transfer of Cu( I) / Cu( II) .Although the electrochemical reduction of copper2amine complexes in H2O is a two one2electron pro2cesses , the catalytic oxidation of 1 ,1′2bi222naphthol can not carry out is mainly due to the poor solubilityof copper2amine complexes and 1 ,1′2bi222naphthol in H2O solution.4 ConclusionsCopper paratolysulfate was synthesized and characterized by various techniques. The electrochemicalbehaviors of Cu( p2OTs) 2 on platinum electrode were studied in DMSO , DMF , CH3OH and H2O solutionsfor the first time. The results showed that the electrochemical reduction of Cu( II) to Cu is via a two one2electron steps in DMSOand H2O solutions and proceeds by one two2electron step in CH3OHand DMF so2lution. However , the reaction transforms to two one2electron steps by the addition of ethanolamine inDMF.The complex of Cu( p2OTs) 2/ ethanolamine (1∶1) can catalyze the oxidation of 1 ,1′2bi222naphthol inDMSO and DMF. This reaction does not work in CH3OH and H2O. Summarizing the electrochemical be2haviors of complexes of various copper salts with ethanolamine , it can conclude that two one2electron stepsreduction of Cu( p2OTs) 2 is the essential condition for the oxidation of 1 ,1′2bi222naphthol .The reaction is indistinguishable in aqueous solutions due to the limited solubility bothCu ( p2OTs) 2/ ethanolamine and 1 ,1′2bi222naphthol .Reference s :[1 ] Solomon E I , Baldwin MJ , Lowery M D. Electronic structure of active sites in copper proteins : contributions to reac2tivity [J ] . Chem. Rev. , 1992 , 92 :521.[2 ] Wang Y, DuBois J L , Hedman B , et al. Catalytic galactose oxidase models : biomimetic Cu( II)2phenoxyl2radical re2activity [J ] . Science , 1998 , 279 :537.[3 ] Collman J P , Fu L , Herrmann P C , et al. A functional model related to cytochrome c oxidase and its electrocatalyticfour2electron reduction of O2 [J ] . Science , 1997 , 275 :949.[4 ] 　Carbral M F , Cabral J de O , Bouwman E , et al. Cyclic voltammetric studies of copper( II) complexes with some bis(imidazole) bis(thioether) ligands. The X2ray crystal structure of (1 ,62bis2(5 (4)2imidazolyl) 22 ,52dithiahexane)dichlorocopper( II) [J ] . Inorg. Chem. Acta , 1992 , 196 :137.[5 ] Wieghardt K, Bossek U , Ventur D , et al. Assembly and structural characterization of binuclearμ2oxo2di2μ2acetatobridged complexes of manganese ( III) . Analogues of the di2iron ( III) centre in Hemerythrin [J ] . J . Chem. Soc.Chem. Commun. , 1985 :347.[6 ] 　Tan D M , Li H H , Wang B , et al. A novel domino reaction of 1 ,1′2bi222naphthol catalyzed by copper( II)2aminecomplexes [J ] . Chinese J . Chem. , 2001 , 19 :91.[7 ] 　House H O , Feng E , Meites L. A comparison of various tetraalkylammonium salt as supporting electrolytes in organicelectrochemical reactions [J ]. J . Org. Chem. , 1971 , 36 :2 371.[8 ] Ahuwalia V K, Tehim A K. Synthesis of some 1 ,3 ,62trioxygenated isopentenylated xanthones [J ] . Tetrahedron ,1984 , 40 :3 303.·772·第 3 期 　　　　　　　宋继国等 :对甲苯磺酸铜及其配合物的电化学行为研究© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.net对甲苯磺酸铜及其配合物电化学行为研究宋继国 ,沈培康 3(中山大学理工学院 ,光电材料与技术国家重点实验室 ,广东 广州 510275)摘要 : 　本文合成了对甲苯磺酸铜 ,并应用热重 (TG)和差示扫描量热法 (DSC)进行分析. 该铜盐容易脱除全部结晶水 ,且在空气中不潮解 ,如与乙醇胺形成等摩尔配合物 ,则在 DMSO 和 DMF 溶剂中能催化 1 ,1′2联222萘酚的氧化 ,但在 H2O 或 CH3OH溶剂中则不发生反应. 此外 ,还分别研究了该铜盐及其它铜盐与乙醇胺 (1∶1)的配合物在 DMSO、DMF、CH3OH 和 H2O 中的电化学行为和催化活性.实验表明 ,铜胺配合物的两步单电子还原过程对催化氧化 1 ,1′2联222萘酚是必要的条件.关键词 : 　对甲苯磺酸铜 ;模拟酶 ;电化学 ;1 ,1′2联222萘酚·872· 电 　化 　学 　　　　　　　　　2004 年© 1994-2008 China Academic Journal Electronic Publishing House. All rights reserved.    http://www.cnki.net

Studies on the Electrochemical Behavior of Copper Paratolysulfate and its Complexes

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Studies on the Electrochemical Behavior of Copper Paratolysulfate and its Complexes

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