Ricardo Oliveira Freire

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Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability--being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be(More)
The Sparkle/AM1 model is extended to ytterbium (III) complexes. Thus, a set of 15 complexes, with various representative ligands, chosen to be representative of all complexes of high crystallographic quality (R-factor <0.05 A) in the Cambridge Crystallographic Database, and which possess oxygen and/or nitrogen as coordinating atoms, was used as the training(More)
Complexes of dysprosium, holmium, and erbium find many applications as single-molecule magnets, as contrast agents for magnetic resonance imaging, as anti-cancer agents, in optical telecommunications, etc. Therefore, the development of tools that can be proven helpful to complex design is presently an active area of research. In this article, we advance a(More)
In this study, we will be presenting LUMPAC (LUMinescence PACkage), which was developed with the objective of making possible the theoretical study of lanthanide-based luminescent systems. This is the first software that allows the study of luminescent properties of lanthanide-based systems. Besides being a computationally efficient software, LUMPAC is user(More)
The Sparkle/PM3 model is extended to cerium(III) complexes. The validation procedure was carried out using only high quality crystallographic structures (R factor < 0.05Å), for a total of thirty-seven Ce(III) complexes. The Sparkle/PM3 unsigned mean error, for all interatomic distances between the Ce(III) ion and the directly coordinating oxygen or nitrogen(More)
We advance the concept that the charge factors of the simple overlap model and the polarizabilities of Judd-Ofelt theory for the luminescence of europium complexes can be effectively and uniquely modeled by perturbation theory on the semiempirical electronic wave function of the complex. With only three adjustable constants, we introduce expressions that(More)
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,(More)
The RM1 quantum chemical model for the calculation of complexes of Tm(III), Yb(III) and Lu(III) is advanced. Subsequently, we tested the models by fully optimizing the geometries of 126 complexes. We then compared the optimized structures with known crystallographic ones from the Cambridge Structural Database. Results indicate that, for thulium complexes,(More)
The correct prediction of the ground-state geometries of lanthanide complexes is an important step in the development of efficient light conversion molecular devices (LCMD). Considering this, we evaluate here the capability of semiempirical approaches and ab initio effective core potential (ECP) methodology in reproducing the coordination polyhedron(More)
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