RM1 Semiempirical Quantum Chemistry: Parameters for Trivalent Lanthanum, Cerium and Praseodymium

Abstract

The RM1 model for the lanthanides is parameterized for complexes of the trications of lanthanum, cerium, and praseodymium. The semiempirical quantum chemical model core stands for the [Xe]4fn electronic configuration, with n =0,1,2 for La(III), Ce(III), and Pr(III), respectively. In addition, the valence shell is described by three electrons in a set of 5d, 6s, and 6p orbitals. Results indicate that the present model is more accurate than the previous sparkle models, although these are still very good methods provided the ligands only possess oxygen or nitrogen atoms directly coordinated to the lanthanide ion. For all other different types of coordination, the present RM1 model for the lanthanides is much superior and must definitely be used. Overall, the accuracy of the model is of the order of 0.07Å for La(III) and Pr(III), and 0.08Å for Ce(III) for lanthanide-ligand atom distances which lie mostly around the 2.3Å to 2.6Å interval, implying an error around 3% only.

RM1 Semiempirical Model: Chemistry, Pharmaceutical Research, Molecular Biology and Materials Science

“…356 This widespread availability motivated several research groups to publish improvements to the method, such as the multiple protocol parameters named semiglobal semiempirical self-consistently scaled quantum mechanical (S4QM), 27 for the adjustment of harmonic vibrational frequencies; the continuous model for neutral solutes in water, octanol, chloroform, carbon tetrachloride and for ions in water, MST/RM1; 33 a modification of RM1 to calculate the binding energy of hydrogen bonding, RM1 BH ; 34 optimization for RM1 of some atomic parameters associated to the continuum solvent COSMO model; 41 implementation of D3H4 dispersion and hydrogen bond correction in RM1 by Řezáč and Hobza; 43 parameterization of the Sparkle model within RM1 for the calculation of lanthanide complexes; 45 and, finally, parameterization of RM1 itself for the lanthanide trications. [36][37][38][39][40] All improvements greatly expanded the scope of RM1 leading to a wide range of applications to organic chemistry, physical chemistry, analytical chemistry and inorganic chemistry, as well as to their interfaces with medicine, biology and materials science.…”

“…Recently, we have completed the parameterization for the 15 lanthanide trivalent ions. [36][37][38][39][40] Aiming at increasing the accuracy of semiempirical methods for the study of biomolecules in aqueous medium, Anisimov and Cavasotto 41 sought to optimize the atomic radii and surface tension coefficients associated to the continuum solvent conductor-like screening model COSMO. Moreover, the authors introduced a multiple atom-type for hydrogen, nitrogen and oxygen (see Table 1).…”

“…45 Thus, the Sparkle/RM1 geometries can therefore be used as a starting geometry to compute other properties by any other methods, ab initio included. More recently, our group [36][37][38][39][40] performed a parameterization of the RM1 model also for the fifteen trivalent lanthanide ions, this time considering a semiempirical basis set of 5d, 6s, and 6p orbitals. The RM1 UME for all lanthanides, now range from a minimum of 0.04 Å for Dy III , 39 Ho III39 and Er III39 to 0.08 Å for Ce III , 39 Yb III37 and Lu III trivalent ions.…”

“…As has been shown using a large set of molecules, the RM1 method is able to predict geometries and heats of formation consistent with DFT results and experimental observations. 36 The speed of MOPAC2009 and improved accuracy of RM1 are particularly valuable for generating electronic descriptors for structure-activity and structure-property relationship analyses".…”

Chemical Partition of the Radiative Decay Rate of Luminescence of Europium Complexes

“…Even though, it is possible to verify an increase in the use of theoretical tools assisting the experimental studies in their quest to design increasingly more efficient luminescent systems 13 14 15 16 . Hence, the extant theoretical tools and techniques are slowly becoming increasingly popular, such as the Sparkle Models 17 18 19 20 21 and RM1 for lanthanides 22 23 24 25 , which are fully available in the MOPAC software 26 , as well as the new lanthanide luminescence software package LUMPAC ( www.lumpac.pro.br ) 12 , the first and only software dedicated to the study of the luminescence properties of systems containing europium ions.…”