Sparkle Model for AM1 Calculation of Lanthanide Complexes:  Improved Parameters for Europium

Abstract

In the present work, we sought to improve our sparkle model for the calculation of lanthanide complexes, SMLC,in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(III), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core-core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that this new parametrization of the SMLC model, with the inclusion of spherical Gaussian functions in the core-core repulsion energy, is better capable of predicting the Eu-ligand distances than the previous version. The unsigned mean error for all interatomic distances Eu-L, in all 96 complexes, which, for the original SMLC is 0.3564 A, is lowered to 0.1993 A when the model was parametrized with the inclusion of two Gaussian functions. Our results also indicate that this model is more applicable to europium complexes with beta-diketone ligands. As such, we conclude that this improved model can be considered a powerful tool for the study of lanthanide complexes and their applications, such as the modeling of light conversion molecular devices.

Interaction of 6,6′′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2′:6′,2′′-terpyridine (CyMe4-BTTP) with some trivalent ions such as lanthanide(iii) ions and americium(iii)

“…3,3,6,6-Tetramethylcyclohexane-1,2-dione 11 was obtained 30 by the acyloin reaction of diethyl 2,2,5,5-tetramethylhexanedioate with sodium/trimethylchlorosilane, 12 followed by oxidation with bromine. 13 Diethyl 2,2,5,5-tetramethylhexanedioate 11 was obtained by the dimerization of pivalic acid using Fenton's reagent, 14 followed by 35 esterification of 2,2,5,5-tetramethylhexanedioic acid with conc.…”

“…15 mL. The flask was cooled to 0 o C and the precipitate was filtered and washed 30 with MeOH (10 mL) and allowed to dry in air to afford the complex as a pale green solid (0.12 g, 75% …”

“…As in the parent ligand 5, the three triplets were assigned to the protons at the 4-positions of each ring while the remaining signals were assigned to the protons at the 3-and 5-positions of each ring. The tentative 30 assignments were made as shown in Figure 9 based on a comparison with the 1 H NMR spectrum of the corresponding quinquepyridine complex. 24 In the aliphatic region, 8 singlets were observed corresponding to each of the methyl groups while the methylene protons appeared as poorly-resolved 35 multiplets.…”

“…We next recorded the NMR spectrum of the Eu(III) biscomplex in perchlorate medium. The Eu(III) ion is not suitable for a conformational analysis because the dipolar contribution to the paramagnetic shifts is comparable to the contact contribution, but this ion causes minimal broadening 30 of the NMR peaks and well-resolved spectra are usually obtained. 26,27 A qualitative analysis of the NMR spectra is thus greatly facilitated.…”

“…All structures were optimized by a force field approach using parameters published by Cundari et al for Gd(III) complexes. 29 Finally, full optimizations were performed using 20 the SPARKLE Yb(III) parameter set that was proposed by Simas et al 30 and that is included in MOPAC 2009. The minimum energy geometry with expected Yb(III)-N distances (2.41-2.43 Ǻ) was obtained starting from the twisted arrangement.…”