Ajuste de funções de base atômicas para o cálculo de propriedades moleculares

Abstract

A systematic study about the importance of the level of theory and the basis sets in the calculation of molecular properties was conducted. It performed studies on the linear and nonlinear optical properties of diatomic molecules, small polyatomic molecules and conjugated donor/acceptor organic molecules. In addition, the structure and reactivity of Pt(II) and Pd(II) complexes were evaluated. Finally, a study about the 195Pt chemical shift was conducted, where various parameters that influence such property have been extensively analyzed. For each work proposed a new basis set was developed. The following basis sets were proposed: D10 (BH), P3 (CO), F3 (CS), J5 (N2), NLO (H,C,N,O,F,S), NLO-X (X=I,II,III,V,aV) (H,B-F,Si-Cl), mDZP (Pd,Pt), kPd-ADZP(Pd) and NMR-TZPP-DKH (H-He, Li-Ne, Na-Ar, K-Ca, Ga-Kr, Rb-Sr, In-Xe e Pt). Estimates of L-NLO properties of several molecules were performed. For a set of molecules with values of first hyperpolarizability (β) ranging from 0 to 190 esu, an average absolute deviation of 13,2 esu was found at cam-B3LYP/NLO-V level compared with 27,2 esu with the standard basis set 6-31G(2d). Furthermore, studies of structure and reactivity of cisplatin and cispalladium were performed. For the aquation reaction of cisplatin an energy barrier of 22.8 kcal.mol-1 was predicted at B3LYP/mDZP/6-31+G(d) level, which it is in excellent agreement with the experimental value of 22.9±0.4 kcal.mol-1. Considering the same reaction, but for Pd analogous, a value of 17.11 kcal.mol-1 at B3LYP/mDZP/6-31+G(d) level and 16.94 kcal.mol-1 at B3LYP/kPd-ADZP/6-31+G(d) level were predicted and these values are in good agreement with the expected value of 16.34 kcal.mol-1. Added to this, an analysis about the 195Pt chemical shift was addressed, where for a wide range of 73 Pt(II) complexes and average absolute deviation of only 156 ppm was found at GIAO-B3LYP(DKHSO)/NMR-TZPP-DKH/IEFPCM-UFF level. All basis sets proposed here were systematically tested and, in general, good results were found for the properties of interest and highly affordable computational costs.