Heibbe's Group

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


New Paper at New Journal of Chemistry

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Synthesis, structural characterization and computational study of a novel amino chalcone: a potential nonlinear optical material

Leonardo R. Almeida, Murilo M. Anjos, Gabriela C. Ribeiro, Clodoaldo Valverde, Daniel F. S. Machado, Guilherme R. Oliveira, Hamilton B. Napolitano and Heibbe C. B. de Oliveira

The interest for novel chalcone-based materials in nonlinear optics is dependent on strong second harmonic generation in organic systems. Chalcones are α,β-unsaturated ketones that can be easily obtained by Claisen–Schmidt condensation between ketones and aromatic aldehydes. A new 2-amino-chalcone was synthesized and its crystal molecular structure was elucidated using the single crystal X-ray diffraction technique. This compound, C15H12BrNO2, crystallizes in monoclinic centrosymmetric space group C2/c with cell parameters a= 29.47(7) Å; b = 6.97(5) Å, c = 13.59(1) Å, β = 112.52(6)° and V = 2581.2(2) Å3. In addition to the crystal structure, the analysis of Hirshfeld surfaces indicates the presence of hydrogen bonds of types N–HO and O–HO that stabilize two independent centrosymmetric dimers, and also indicates the presence of π–π stacking interactions that stabilize a supramolecular trimeric system. Being a push–pull chromophore we investigated the NLO properties of the 2-amino-chalcone asymmetric unit using the supermolecule approach in combination with an iterative electrostatic polarization scheme. The calculations were performed using the CAM-B3LYP/6-311+G(d) level of theory for both dynamic and static situations. In the presence of the embedding charges, the γ value is increased by 20% for the dynamic calculation but only 8% for the static limit. In contrast to the crystal form, when in solution the 2-amino-chalcone lacks an inversion center so that second order NLO properties do not vanish. Following this idea we computed the NLO properties using the implicit solvation approach IEF-PCM. The solvent effect on the NLO properties was to augment its values as the solvent polarity increases. We obtained for the in-crystal and in DMSO 2-amino-chalcone, γ(−2ω;ω,ω,0) = 144.12 × 10−36 esu and 260.163 × 10−36 esu, respectively, and therefore interesting materials for third order NLO applications.

Cover of Journal of Computacional Chemistry

Cover JCC
Deformed transition-state theory: Deviation from Arrhenius behavior and application to bimolecular hydrogen transfer reaction rates in the tunneling regime

Valter H. Carvalho-Silva, Vincenzo Aquilanti, Heibbe C. B. de Oliveira, Kleber C. Mundim

A formulation is presented for the application of tools from quantum chemistry and transition-state theory to phenomenologically cover cases where reaction rates deviate from Arrhenius law at low temperatures. A parameter d is introduced to describe the deviation for the systems from reaching the thermodynamic limit and is identified as the linearizing coefficient in the dependence of the inverse activation energy with inverse temperature. Its physical meaning is given and when deviation can be ascribed to quantum mechanical tunneling its value is calculated explicitly. Here, a new derivation is given of the previously established relationship of the parameter d with features of the barrier in the potential energy surface. The proposed variant of transition state theory permits comparison with experiments and tests against alternative formulations. Prescriptions are provided and implemented to three hydrogen transfer reactions: CH4 + OH CH3 + H2O, CH3Cl + OH CH2Cl + H2O and H2 + CN H + HCN, widely investigated both experimentally and theoretically. © 2016 Wiley Periodicals, Inc.

New Paper at The Journal of Physical Chemistry C

TOC Graph paper JPCC 2017
Strong Solvent Effects on the Nonlinear Optical Properties of Z and E Isomers from Azo-Enaminone Derivatives

Daniel F. S. Machado, Thiago O. Lopes, Igo T. Lima, Demétrio A. da Silva Filho, and Heibbe C. B. de Oliveire

We calculated the nonlinear optical properties of 24 azo-enaminone derivatives, incorporating solvent effects on their geometric and electronic structure, to assess the impact of the environment on these properties. Namely, we incorporated chloroform, tetrahydrofuran, acetone, ethanol, methanol, and dimethyl sulfoxide in our calculations and compared our results incorporating solvent effects with our gas-phase calculations. To account for the electron correlation effects on NLO properties, we performed the calculations at MP2/6-31G(p)//MP2/6-31G(d) level set. The polarizable continuum model was used to simulate the presence of the solvent. The exponents of p extra functions added to heavy atoms were obtained, imposing the maximization of the first hyperpolarizability. Two structural configurations (Z and E) of azo-enaminones were investigated to assess the isomeric effects of the electric properties. Our results show that both solvent polarity and relative strength of the donor groups have a significant impact on the electric properties but more strikingly on the first hyperpolarizability β.