Conceptual DFT Study of the Local Chemical Reactivity of the Colored BISARG Melanoidin and Its Protonated Derivative

Abstract

This computational study assessed eight fixed RSH (range-separated hybrid) density functionals that include CAM-B3LYP, LC-ωPBE, M11, MN12SX, N12SX, ωB97, ωB97X, and ωB97XD related to the Def2TZVP basis sets together with the SMD solvation model in the calculation the molecular structure and reactivity properties of the BISARG intermediate melanoidin pigment (5-(2-(E)-(Z)-5-[(2-furyl)methylidene]-3-(4-acetylamino-4-carboxybutyl)-2-imino-1,3-dihydroimidazol-4-ylideneamino(E)-4-[(2-furyl)methylidene]-5-oxo-1H-imidazol-1-yl)-2-acetylaminovaleric acid) and its protonated derivative, BISARG(p). The chemical reactivity descriptors for the systems were calculated via the Conceptual Density Functional Theory. The choice of active sites applicable to nucleophilic, electrophilic as well as radical attacks were made by linking them with Fukui functions indices, electrophilic and nucleophilic Parr functions, and the condensed Dual Descriptor Δf(r). The study found the MN12SX and N12SX density functionals to be the most appropriate in predicting the chemical reactivity of the molecular systems under study starting from the knowledge of the HOMO, LUMO, and HOMO-LUMO gap energies.

Local Molecular Reactivity of the Colored Dansylglycine in Water and Dioxane Studied through Conceptual DFT

“…In the same way, as in our recent works on melanoidins [6][7][8][9][10], it has been found that the model chemistry formed by the connection between the MN12SX density functional and the Def2TZVP basis set is the best for justifying the fulfilling of the KID procedure for the dansylglycine molecule, both in the presence of water and dioxane. is, instead of presenting the comparison of the values of the orbital energies with the ionization potential I and the electron affinity A for different density functionals, we are showing the results for the global descriptors calculated with the MN12SX density functional in Table 1 comparing the values that arise from both solvents.…”

“…Following the lines of our previous work [6][7][8][9][10], the computational studies were performed with the Gaussian 09 [34] series of programs with density functional methods as implemented in the computational package. e basis set used in this work was Def2SVP for geometry optimization and frequencies, while Def2TZVP was considered for the calculation of the electronic properties [35,36].…”

“…If we consider the KID (for Koopmans in DFT) procedure presented in our previous works [6][7][8][9][10] together with a finite difference approximation, then the global reactivity descriptors can be calculated starting from the orbital energies of the HOMO and LUMO: electronegativity χ [19,20], global hardness η [19,20], electrophilicty ω [21], electrodonating ω − [22], electroaccepting power ω + [22], and net electrophilicity Δω ± [23]. Applying the same ideas related to the KID procedure, the local reactivity descriptors can be expressed as follows: [24][25][26][27][28][29][30], nucleophilic Parr function: P − (r) � ρ rc s (r) [31,32], and electrophilic Parr function: P + (r) � ρ ra s (r) [31,32], where ρ N+1 (r), ρ N (r), and ρ N−1 (r) are the electronic densities at point r for the system with N + 1, N, and N − 1 electrons, respectively, and ρ rc s (r) and ρ ra s (r) are related to the atomic spin density (ASD) at the r atom of the radical cation or anion of a given molecule, respectively [33].…”

“…One of these isolated molecules is called dansylglycine (or 2-[[5-(dimethylamino)naphthalen-1-yl]sulfonylamino] acetic acid) which has interesting properties as a colored molecule and as a fluorescent dye in water and dioxane, and we believe that it could be of interest to study their molecular reactivity by using the ideas of conceptual DFT [1][2][3][4][5], in the same way of our previous works [6][7][8][9][10].…”

Conceptual DFT as a Helpful Chemoinformatics Tool for the Study of the Clavanin Family of Antimicrobial Marine Peptides

“…According to Frau and Glossman-Mitnik, the evaluation of marine peptides and melanoidins in the generation of HOMO and LUMO energies is required in the verification of the levels of agreement with the estimated Koopmans' theorem based on the combination of the MN12SX density functional and the Def2TZVP basis set [22][23][24][25][26][27][28]. This justifies the application of the proposed KID (for Koopmans in DFT) technique.…”