Sparkle/RM1 parameters for the semiempirical quantum chemical calculation of lanthanide complexes

In this article, we present Sparkle Model parameters to be used with RM1, presently one of the most accurate and widely used semiempirical molecular orbital models based exclusively on monoatomic parameters, for systems containing H, C, N, O, P, S, F, Cl, Br, and I. Accordingly, we used the geometries of 169 high quality crystallographic structures of complexes for the training set, and 435 more for the validation of the parameterization for the whole lanthanide series, from La(III) to Lu(III). The distance deviations appear to be random around a mean for all lanthanides. The average unsigned error for Sparkle/RM1 for the distances between the metal ion and its coordinating atoms is 0.065 angstrom for all lanthanides, ranging from a minimum of 0.056 angstrom for Pm(III) to 0.074 angstrom for Ce(III), making Sparkle/RM1 a balanced method across the lanthanide series. Moreover, a detailed analysis of all results indicates that Sparkle/RM1 is particularly accurate in the prediction of lanthanide cation-coordinating atom distances, making it a suitable method for the design of luminescent lanthanide complexes. We illustrate the potential of Sparkle/RM1 by carrying out a Sparkle/RM1 full geometry optimization of a tetramer complex of europium with 181 atoms. Sparkle/RM1 may be used for the prediction of geometries of large complexes, metal-organic frameworks, etc., to useful accuracy.