Sparkle/PM3 Parameters for the Modeling of Neodymium(III), Promethium(III), and Samarium(III) Complexes

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• 作者：Ricardo O. Freire ; Nivan B. da Costa ; Jr. ; Gerd B. Rocha ; Alfredo M. Simas
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2007
• 出版时间：July 2007
• 年：2007
• 卷：3
• 期：4
• 页码：1588 - 1596
• 全文大小：464K
• 年卷期：v.3,no.4(July 2007)
• ISSN：1549-9626

文摘

The Sparkle/PM3 model is extended to neodymium(III), promethium(III), andsamarium(III) complexes. The unsigned mean error, for all Sparkle/PM3 interatomic distancesbetween the trivalent lanthanide ion and the ligand atoms of the first sphere of coordination, is0.074 Å for Nd(III); 0.057 Å for Pm(III); and 0.075 Å for Sm(III). These figures are similar to theSparkle/AM1 ones of 0.076 Å, 0.059 Å, and 0.075 Å, respectively, indicating they are allcomparable models. Moreover, their accuracy is similar to what can be obtained by present-day ab initio effective potential calculations on such lanthanide complexes. Hence, the choiceof which model to utilize will depend on the assessment of the effect of either AM1 or PM3 onthe quantum chemical description of the organic ligands. Finally, we present a preliminary attemptto verify the geometry prediction consistency of Sparkle/PM3. Since lanthanide complexes areusually flexible, we randomly generated 200 different input geometries for the samarium complexQIPQOV which were then fully optimized by Sparkle/PM3. A trend appeared in that, on average,the lower the total energy of the local minima found, the lower the unsigned mean errors, andthe higher the accuracy of the model. These preliminary results do indicate that attempting tofind, with Sparkle/PM3, a global minimum for the geometry of a given complex, with theunderstanding that it will tend to be closer to the experimental geometry, appears to be warranted.Therefore, the sparkle model is seemingly a trustworthy semiempirical quantum chemical modelfor the prediction of lanthanide complexes geometries.