Maximiliano Segala

Heterocyclic dyes displaying excited-state intramolecular proton-transfer reactions (ESIPT): computational study of the substitution effect on the electronic absorption spectra of 2-(2′-hydroxyphenyl)-1,3-benzoxazole derivatives †

Semi-empirical molecular-orbital methods were used to simulate the electronic absorption spectra of a series of 2-(2′-hydroxyphenyl)-1,3-benzoxazole derivatives, namely AM1 and MNDO-PM3 for geometry optimization and INDO/S-CI and HAM/3 for spectroscopic features. Wavelengths of maximum absorption that agree better with experimental data were found when INDO/S-CI was applied to PM3-generated inputs. Chemical substitution red-shifted the absorption spectrum of all the model compounds, a feature discussed based on the calculated energy levels of frontier orbitals and charge redistribution upon electronic excitation.

Conformational analyses and SAR studies of antispermatogenic hexahydroindenopyridines

Abstract We studied Structure–Activity Relationships (SAR) of a series of 2,3,4,4a,5,9b-hexahydroindeno[1,2-c]pyridine derivatives, which present antispermatogenic activity, using Principal Component Analysis (PCA), K-Nearest Neighbor (KNN) and Neural Network (NN) methods. Firstly, we carried out thorough conformational explorations using the PM3 method, in order to determine the most stable conformations. The minima found were optimized using ab initio HF/3-21G. Molecular properties were calculated using the same ab initio method. Steric properties such as molecular volume and surface and the octanol/water partition coefficient were also calculated. A total of three variables (atomic charges on two specific atoms and the molecular volume) out of many were selected as being useful for SAR. PCA yielded a reasonable separation between high-activity and low-activity groups. The KNN and NN methods presented approximately 70% correct classifications. Finally, a set of new compounds was proposed and analyzed.

Quatro alternativas para resolver a equação de Schrödinger para o átomo de hidrogênio

Quantum chemistry describes the hydrogen atom as one of the few systems that permits an exact solution of the Schrodinger equation. Students tend to consider that little can be learned from the hydrogen atom and forget that it can be used as a standard to test numerical procedures used to calculate properties of multielectronic systems. In this paper, four different numerical procedures are described in order to solve the Schrodinger equation for the hydrogen atom. The basic motivation is to identify new insights and methods that can be obtained from the application of powerful numerical techniques in a well-known system.