希土元素异硫氰酸盐与二甲基乙酰胺配合物的标准生成焓的测定

DETERMINATION OF STANDARD ENTHALPIES OF FORMATION FOR THE COMPLEXES OF RARE EARTH ISOTHIOCYANATES WITH DIMETHYLACETAMIDE

本文测量了298.15K时La、Ce、Pr、Nd、Sm、Eu、Gd、Dy、Ho、Yb、Y十一种希土元素异硫氰酸盐水合物[RE(NCS)_3·nH_2O]在二甲基乙酰胺(DMA)水溶液中的积分溶解热以及相应的十一种希土元素异硫氰酸盐二甲基乙酰胺配合物[RE(NCS)_3·mDMA]在水中的积分溶解热。藉助于本文所设计的热化学循环,用本文所测得的积分溶解热数据和文献数据,求得了这十一种RE(NCS)_3·mDMA的标准生成焓,进而计算出了它们的晶格能。此外,还对Tb、Er、Tm、Lu四种RE(NCS)_3·mDMA的相应数据进行了估算。

Fifteen solid complexes of rare earth (except Sc, Pm) isothiocyanates with N, N-dimcthylacetamide (DMA) were synthesized. They were characterized by chemical analysis, infrared spectra, X-ray diffraction, differential thermal and thermogravimetric analyses. Both integral heats of solution of RE(NCS)3·mDMA(for RE = La, Ce, Pr, Nd, m=5; for RE = Sm, Eu, Gd, Dy, Ho, Yb, Y, m = 4) in water and those of RE(NCS)3 ·nH2O(for RE = La, Ce, Pr, Nd, n = 7; for RE = Sm, Eu, Gd, Dy, Ho, Yb, Y, n = 6) in aqueous DMA solution have been measured calorimetrically at 298.15K. By means of the thermochcmical cycle suggested in this paper, using the data measured and picked from references [4-7], the standard enthalpies of formation for eleven RE(NCS)3 · mDMA as stated above were calculated. Furthermore, corresponding data for other four RE(NCS)3 · mDMA(RE = Tb, Er, Tm, Lu, m = 4) were estimated. Plot - ΔHf of RE(NCS)3 · mDMA against the atomic numbers of the elements in Ln-scrics, 'double peak' are observed at the positions of Eu and Yb. The lattice energies of RE(NCS)3 · mDMAwere also calculated.