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采用均匀沉淀法,在20%的乙醇水溶液中,用水杨酸、维生素B3与稀土硝酸盐合成了一类新的稀土三元配合物.通过元素分析、化学分析、摩尔电导、红外光谱、紫外光谱、热重-微分热重分析等手段对配合物的结构和性质进行表征,确定了它们的组成通式为[RE(C7H5O3)2(C6H4NO2)·H2O](RE=La,Ce,Nd).维生素B3吡啶环上的N原子和水杨酸的酚羟基均未参与配位,两种配体均是脱质子后以羧酸根与RE3+离子配位,且成键以离子性为主,兼有部分共价性.在298.15 K,用精密的溶解-反应热量计分别测量了配位反应相关各物质的溶解焓,根据盖斯(Hess)定律求得合成反应的标准摩尔反应焓r mHФ分别为:(180.61±0.72)、(187.25±0.68)和(185.61±0.26)kJ/mol.进而求出配合物的标准摩尔生成焓为:f mHФ[La(C7H5O3)2(C6H4NO2)·H2O(s),298.15 K]=-(2493.9±2.9)、f mHФ[Ce(C7H5O3)2(C6H4NO2)·H2O(s),298.15 K]=-(2441.0±2.8)和f mHФ[Nd(C7H5O3)2(C6H4NO2)·H2O(s),298.15 K]=-(2463.1±2.9)kJ/mol.
A novel rare earth ternary complex was synthesized by salting-out method with salicylic acid, vitamin B3 and rare earth nitrate in a 20% aqueous ethanol solution by the uniform precipitation method. Elemental analysis, chemical analysis, molar conductance, infrared spectroscopy, , Thermogravimetry-differential thermal gravimetric analysis (TGA), the structures and properties of the complexes were characterized, and their compositional formulas were confirmed as [RE (C7H5O3) 2 (C6H4NO2) · H2O] (RE = La, Ce, Nd). Vitamin B3 pyridine ring N atom and the phenolic hydroxyl group of salicylic acid are not involved in coordination, both ligands are deprotonated with carboxylate and RE3 ion coordination, and bond to the ionic-based, both Partial covalency.At 298.15 K, the enthalpies of dissolution of each substance related to the coordination reaction were measured respectively by the precision dissolution-reaction calorimeter, and the standard molar enthalpy of reaction r mHФ obtained from the Hess law was (180.61 ± 0.72), (187.25 ± 0.68) and (185.61 ± 0.26) kJ / mol, respectively, and the standard enthalpy of formation for the complex was calculated as: fmHФ [La (C7H5O3) 2 (C6H4NO2) , 298.15 K] = - (2493.9 ± 2.9), f mHФ [Ce (C7H5O3) 2 (C6H4NO2) · H2O (s), 298.15 K] = - (2441.0 ± 2.8) and fmHФ [Nd (C7H5O3) 2 ) · H 2O (s), 298.15 K] = - (2463.1 ± 2.9) kJ / mol.