Enthalpies of Solution of Complexes of Rare Earth Nitrate with L-α-Histidine in Water

JOURNAL OF RARE EARITHS2002 Vol.20 No.5Enthalpies of Solution of Complexes of Rare Earth Nitratewith L-a-Histidine in W aterLiu Yang(刘洋), Fang Yan(房艳), Gao Shengli(高胜利)* , Chen Sanping( 陈三平),Shi Qizhen(史启祯)( Departemnt of Chemistry , Shaanxi Key Laboratory of Physico- lnorganic Chemistry , Northwest University ,Xi' an 710069 , China )Abstract : The enthalpies of solution in water of complexes of RE( NO3 )( RE=La~Nd , Sm~Lu, Y ) with L-a- Histidine( His ) were measured at 298. 15 K. The standard enthalpies of formation of RE( His尸+( aq ) were calculated. The" tetradeffeet”regularity was observed from the curve , which is the enthalpies of solution plotted against the atomic numbers of theelements in lanthanide series .Key words : rare earths ; histidine ; enthalpy of solutionCLC number :0614.33 ;0641.4 .Document code :A Article ID : 1002 - 0721( 2002 )05 - 0424 - 03Lanthanide ions possess some special func-1 Experimentaltions in biological body and they are often used aspromoters in the textile dyeing industry , and as di-1.1Preparation and composition of title .agnostic agents in clinical medicine 1-31. Aminocomplexesacids are the basic units of proteins. It has becomeReferred to Ref. 7] , fifeen solid complexesmore important to understand the behavior of lan-were prepared , and put into a desiccator contain-thanide ions in biological systems. The structures ,ing P4O10 for drying until the weight of the com-synthesis and properties of the complexes of rareplexes became constant. Chemical analysis provedearths with amino acids have been reported in de-that the composition of the complexes were REtails by Wang Ruiyad4] , Ma AizengS] and Gao( His )( NO3 ); H20. The analytical results ofShenglF6], respectively. Gao Shengli and oth-composition of the complexes were given in Tableers 7~9J have investigated the solubility propertiesof RE( NO3 )-His-H2O systems at 298.15 K in the1.2 Experimental and conditionswhole concentration range by phase equilibriumAll measurements were made using a heatmethod , and the properties of complexes of REconduction microcalorimeter , type RD496- I from( HisX NO3 ); H2O. However , studies on the en-Southwest Electronic Engineering Institute of Chi-thalpies of solution of RE( His X NO3 ): H20 innt 10J , which was equipped with two 15 ml calori-water have not been reported. In this paper , themetric vessels( Fig.1 ) , and operated at 298. 15士enthalpies of solution of complexes of RE( His )0.005 K. The microcalorimeter was calibrated by(NO3 ); H2O in water at 298. 15 K were deter-the Joule effect and its sensitivity was 63. 994土0.mined using a heat conduction microcalorimeter.042 μV mW-1. The experimental precision andThe standard enthalpies of formation of REaccul中国煤化工measurement of the( His )+( aq) were calculated.enthaTYHCNMHG①Received date :2002- 07- 15 ; revised date :2002 -08 - 30Foundation item : Project supported by the National Natural Science Foundation of China( 2017036 )Bioqpraphy; liw Yang( 1977 - ), Female , MasterCorespondemt-mail : weizhang@ nwu. eodu. en)No.5.Enthalpies of Solution of Complexes of Rare Earth Nitrate with L-a- Histidine in Water425Table 1 Analytical results on chemical composition of title complexes ( mass fraction )*ComplexesRE/%His/%C/%H/%N/%L( HisY NO3) H2027.57(27. 89) 31.1K31.15) 14.21(14.47) 2.142.23) 16.92 16.87)C( HisX NO3) H2028.228.06) 31 .28(31.07) 14.07 14.43) 2. I2x 2.22 )16.89( 16.83 )P( HisINO3) H2027.91(28.18) 31.9031.03) 14.10(14.41) 2.0X2.22) 16.72 16. 80)Nd HisINO3) H2O28.53(28.65) 30.72(30.82) 14.0X14.32) 2.032.20) 16.54( 16.69)Sn( HisINO3) H2029.4<(29.51) 30.65(30.45) 13.98(14.14) 2.0K2. 18)16.28 16.49 )Eu( HisINO3) H2029.5<29.33) 30.14(30.36) 13.9214.10) 1.992.17) 16. I6( 16.44)Gd HisXNO3) H2030.4(30.45) 29.96(30.04) 14.14(13.95) 2.322.15) 16.03( 16.27)T( His I NO3) H2030.91(30.67) 30.0729.95) 14.0513.91) 2.20(2.14)16.31( 16.22)D( HisINO3) H2031.23(31.15) 29. 40( 29.74) 13. 8X 13.81) 2.242. 13 )16.24(16.11)Hd( His Y NO3) H2031.7(31.47) 29.4429.60) 13.64(13.75) 2.11(2.12) 16.0% 16.03)Ed( HisINO3) H2O31.42X31.77) 29.4329.47) 13.78(13.69) 1.9(2.11) 15.8x 15.96)Tm( HisINO3) H2O31.5431.99) 29.31(29.38) 13.50[13.65) 1.9(2. 10)16.0X 15.91 )YK( HisINO3) H2032.43(31.51) 28. 83(29.15) 13.3813.54) 1 .892.08) 15 .63( 15.79)Lud( His NO3) H20 .32. 51(32.76) 29.01(29.05) 13.29(13.49) 1.942.08) 15. 80( 15.73)Y( HisINO3) H20 _19.8X19.84) 34.2534.63) 15.9616.08) 1.5X2.47)18.8418.85)* The data in brackets were calculated values ; RE + was determined oplexomteically with EDTA. L-a-His was determined by the formalin method. C.H , andN analyses were carried out on a 2400-type elemental analyzer( RE comp. )in Table 2 could be considered of a value at infi-nite dilution. The dissolution processes of the com-plexes could be expressed as following12]:RE( His NO3 ); H2Q( s)+ nH20( 1)-A[ RE(His)+ [aq) + 3 NO3~(aq) + ( n+ 1 )H20(l)( 1)(1 ) According to Hess' Law , the standardFig.1 Sketch of the sample cellenthalpies of formation of RE( His )+( aq ) were1 - calorimetric cell ;2- solid sample ;3 - spacer ;calculated through Eq.( 1 ):4 - solution .solution of high-purity crystalline KCl in deionizedTable 2 Enthalpies of solution of RE( HisX NO3》water at 298. 15K. The experimental value of AsolH2O in water at 298. 15K'Hmof 17.238士0.048 kJ mol-1 was in good a-w/mg(kJ mol-1)greement with that of .o Hm of 17.241土0.018 kJHs&NO)H2O 6.218-8.08 3815~2414 2.71+0.07*C(HisNO3) HO 6.154-7.486 36106~ 2426823.29+0.08mol-1 reported in the literature 1. This indicat-P(HisINO3}HO 5.475-8.672 40743-25671 22.46+0.07 .ed that the device for the enthalpy of solution mea-N( HisXNO3) H20 6.492-9.302 34695-2005 20.35 +0.07Sn( HisINO3)H20 5.602-9.088 40373- 25090 21.37+0.06surements used in this work was reliable. The con-E(HisINO3) H06.184-9.26 36702~240050 2.82+0.05G( HisENO3) H2O 6.010~9.544 38284~24005 24.35 +0.06ductivity of the deionized water used in the experi-T6 His (N03) H206.662~9.108 34695~ 2597122.23 +0.07D( His页NO3) HO5.840~ 8.92539652-25971 21 31 +0.07ments was 5.48x 10-8 S cm -1.H( HisN03) H2O6.298-9.035 37008~ 2582020.59+0.07Ef His页NO3) H2O6.2529.82637319 ~ 23749 20.72+ 0.072 Results and DiscussionTi( His NO) HO5.648~ 12.93841505~ 181282.49+0.06YI( HisINO) H205.858-9.146 40373~ 2582023.17 +0.07L(HisN03} H0 6.280~ 10.588 376-22429 22.02+0.06Results for the enthalpies of solution of fifteenY(HisINO3) H0 6.544-9.518 30418-22774 19.44+0.05Deviations are standard deviationscomplexes of rare earths nitrate with His in deion-中国煤化工ized water at 298. 15 K are given in Table 2 ,MYHCNMHGHm-3OrNO;(un)HMwhere r is the molar ratio n( H2O ) n( complex ).The greater values of r ( 18128 ~ 41505 ) were+ Ar H.C 1)HM + Ar eoks)H%(2)used and the△sol Hm was nearly unchanged for dif-Here, ARHi"(an) Hm is from Table 2ferent n瓦友数据Therefore , the means of Asol HmOrNoO,(an)Hm= - 207.36 kJ mol-113], and426JOURNAL OF RARE EARTHSVol.20Aca1)H= - 285. 83 +0.042 kJ mol-1[16]，(3) According to the curves in Fig.2 , theand Arcood<) Hm is from Ref. 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