Heibbe's Group

Research Group under Prof. Dr. Heibbe Cristhian B. de Oliveira


Qualifying Defense of Fernanda Santos

Title: "Efeito Anomérico em Rearranjos de Hurd Claisen e Investigações Termocinéticas de seus Estados de Transição Early e Late"
Adivisor: Heibbe Cristhian Benedito de Oliveira
Co-adivisor: Ângelo Henrique de Lira Machado
Committee members: Wender Alves Silva and Luciano Ribeiro


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Qualifying Defense of Ueslei Vasconcelos

Title: "Viabilidade Termodinâmica da Modificação do Band Gap de Folhas de Grafeno por Intermédio de Cátions Alcalinos: Uma Abordagem Minimalista Beseada em Propriedades Rovibracionais"
Adivisor: Heibbe Cristhian Benedito de Oliveira
Committee members: Elaine Rose Maia and José Roberto dos Santos Politi


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Thesis Defense of Daniel FS Machado

Theme: Desenvolvimento de Métodos Fisicamente Inspirados para Cálculos de Ótica Não-Linear e Efeitos de Solventes nas Propriedades Óticas Não-Lineares em Derivados de Azo-Enaminonas
Advisor: Prof. Dr. Heibbe CB de Oliveira
Coadivisor: Prof. Dr. Demétrio AS Filho
Committee members: Ricardo Gargano, João Batista Lopes Martins and Luciano Ribeiro


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New Paper at Journal of The American Society for Mass Spectrometry

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Charge-tagged N-heterocyclic carbenes (NHC): Direct transfer from ionic liquid solutions and long-lived nature in the gas phase

Thyago S. Rodrigues, Denis Lesage, Wender A. da Silva, Richard B. Cole, Günter Ebeling, Jaïrton Dupont, Heibbe C. B. de Oliveira, Marcos N. Eberlin, Brenno A. D. Neto

Negatively charge-tagged N-heterocyclic carbenes have been formed in solution via deprotonation of imidazolium ions bearing acid side groups and transferred to the gas phase via ESI(–)-MS. The structure of the putative and apparently stable gaseous carbenes formed in such conditions were then probed via reactions with carbon dioxide using a triple quadrupole mass spectrometer particularly optimized for ion/molecule reactions of ESI-generated ions. Complete conversion to imidazolium carboxylates was achieved, which seems to demonstrate the efficiency of the transfer, the gas-phase stability, and the long-lived nature of these unprecedented charge-tagged carbenes and their predominance in the ionic population. Comprehensive studies on the intrinsic reactivity of N-heterocyclic carbenes with silent charge tags are therefore possible.

New Paper at Journal of Molecular Modeling

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A novel analytical potential function for dicationic diatomic molecular systems based on deformed exponential function

Daniel F. S. Machado, Rodrigo A. L. Silva, Ana Paula de Oliveira, Valter H. Carvalho-Silvam Ricardo Garganom Luciano Ribeiro, Heibbe C. B. de Oliveira

In this paper, we propose a new alternative analytical function aiming to better describe the potential energy curves of the doubly charged diatomic molecules. To achieve this goal, we modified an existing potential function in the literature to describe dicationic diatomic molecules using the deformed exponential function. We generated the potential energy curve of the testing group of dicationic diatomic molecules Be2+2Be22+ , BH2+, He2+2He22+ and NH2+ by means of the CCSD(T)/aug-cc-pVQZ level of theory. To validate this new function, we also calculated the spectroscopic constants and the rovibrational spectra for the electronic state X1Σ+gX1Σg+ of the Be2+2Be22+ and He2+2He22+ systems using the Dunham and discrete variable representation methods. For BH2+ and NH2+ molecules, despite exhibiting a local minimum in the potential energy curve, no vibrational levels are supported, so the spectroscopic constants for these poorly bound systems are invalidated. The fitting accuracy had a better performance over the original potential for describing dicationic diatomic systems, considering that the discrete variable representation method resulted in a similar vibrational structure described in the literature. This fact can be explained due to the deformed function’s flexibility.

New Paper at Journal of Molecular Modeling

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Effect of the crystalline environment on the third-order nonlinear optical properties of L-arginine phosphate monohydrate: a theoretical study

Clodoaldo Valverde, Rosemberg F. N. Rodrigues, Daniel F. S. MachadoBasílio Baseia, Heibbe C. B. de Oliveira

A supermolecular approach combined with an iterative electrostatic scheme was employed to investigate the nonlinear optical properties of the hybrid L-arginine phosphate monohydrate crystal, the procedure being aided by DFT calculations. The supermolecular scheme basically treated the molecules surrounding the unit cell as point charges; this approximation results in rapid convergence, making it a feasible method. DFT functionals of different flavors were considered: B3LYP, B2PLYP, CAM-B3LYP, ωB97, and M06HF, utilizing the 6-311 + G(d) basis set. All functionals gave sufficiently accurate values for the dipole moment (μ) with respect to the experimental value 32(2) D. For the average linear polarizability ( α⎯⎯⎯α¯ ) and the total first hyperpolarizability (βtot), good agreement was observed between the DFT-calculated values and MP2-derived results reported in the literature. For the second hyperpolarizability, both static and dynamic regimes were considered. The point-charge embedding approach led to an attenuation of the second hyperpolarizability γ for all frequencies considered. Excitations of γ were not observed for frequencies smaller than 0.1 a.u. For the second hyperpolarizability (both static and dynamic), computational results showed that L-arginine phosphate monohydrate exhibits a large nonlinear optical effect, which implies the occurrence of microscopic third-order NLO behavior.

Back Cover of Physical Chemistry Chemical Physics

cover PCCP 2015
Rovibrational spectroscopic constants of the interaction between ammonia and metallo-phthalocyanines: a theoretical protocol for ammonia sensor design

Alan R. Baggio, Daniel F. S. Machado, Valter H. Carvalho-Silva, Leonardo G. Paterno and Heibbe Cristhian B. de Oliveira

In the present contribution, we develop an adapted theoretical approach based on DFT calculations (B3LYP functional) and solution of the nuclear Schrödinger equation by using the Discrete Variable Representation method to model the interaction of ammonia with metallo-phthalocyanines (MPcs, where M = Fe2+, Co2+, Ni2+, Cu2+ or Zn2+). This approach is intended to be a general protocol for the rational design of chemical sensors. The as-obtained binding energy curves, obtained from ab initio points, permitted us to calculate rovibrational energies and spectroscopic constants, as well as to establish the relative population of rovibrational states in different types of MPc–NH3 thermodynamic systems. Simulated binding energy curves show that the binding energy in MPc–NH3 systems is dependent on the type of M central ion, decreasing in the order FePc > ZnPc > CoPc > CuPc > NiPc, with values spanning from −170 to −16 kJ mol−1. Also, MPc–NH3 systems have at least 16 rovibrational levels, which confirms that they are all bound systems (chemically or physically). Despite that, only the interaction between ammonia and FePc, CoPc or ZnPc is spontaneous within the studied temperature range (200–700 K). NiPc and CuPc show a change between spontaneous and non-spontaneous behaviours at 400 K and 500 K, respectively. Less bound systems should more efficiently guarantee the sensors' signal reset, while they are also less specific than sensors built with medium to strongly bound systems. Moreover, the intermediate energy and spontaneous binding of ammonia to NiPc and CuPc at operation temperatures, as determined with our theoretical approach, suggests that these MPcs are most promising for ammonia sensors.