scholarly journals INVESTIGASI EKSTRAK BAHAN ALAM SEBAGAI INHIBITOR KOROSI HIJAU PADA BAJA MENGGUNAKAN TEORI FUNGSIONAL KERAPATAN

Sebatik ◽  
2022 ◽  
Vol 26 (1) ◽  
Author(s):  
Muhamad Akrom
Keyword(s):  
Molecular Orbitals ◽  
Frontier Molecular Orbitals ◽  
Green Inhibitor ◽  
Homo Lumo

Salah satu material yang ketahanannya terhadap korosi rendah adalah baja ketika berinteraksi dengan lingkungan korosif. Penggunaan green inhibitor mampu memberikan kinerja penghambatan korosi yang baik dengan efisiensi inhibisi yang tinggi pada baja.  Green inhibitor yang dalam struktur senyawanya mengandung gugus heteroatom (seperti O, N, S, P) dan cincin aromatik efisien digunakan sebagai inhibitor korosi pada baja. Makalah ini memberikan tinjauan komparatif penting bagi pengembangan green inhibitor ekstrak bahan alam pada baja. Kajian DFT pada level atomik berdasarkan orbital molekuler, parameter kuantum kimia, dan karakteristik adsorpsi menunjukkan hasil yang sesuai dengan hasil eksperimen. Distribusi kerapatan elektron melalui plot Frontier Molecular Orbitals (FMO) menggambarkan prediksi situs aktif melalui distribusi daerah HOMO-LUMO molekul inhibitor yang berinteraksi dengan permukaan baja. Untuk mendapatkan korelasi antara sifat elektronik molekul inhibitor dengan potensi penghambatan (inhibisi) korosi, kalkulasi parameter kimia kuantum seperti potensial ionisasi (I), afinitas elektron (A), kekerasan global (η), elektronegativitas absolut (χ), kelembutan global (σ), fraksi elektron yang ditransfer (ΔN), elektrofilisitas global (ɷ) dan donasi balik elektron (ΔEback-donation) menunjukkan reaktivitas molekul inhibitor yang berpotensi sangat baik untuk dapat berinteraksi dan berikatan kuat dengan permukaan logam, sehingga berpotensi menghasilkan efisiensi inhibisi yang tinggi. Mekanisme inhibisi korosi dapat melalui adsorpsi kimia dan/atau adsorpsi fisika dengan membentuk senyawa kompleks antara molekul inhibitor dengan permukaan baja untuk melindungi dari lingkungan korosif. Pengembangan kajian ke depan harus dapat menampilkan mekanisme interaksi dan inhibisi dari molekul inhibitor secara lebih detail dan sistematis pada level atomik pada beberapa permukaan logam seperti Fe, Al, Cu, dan lainnya.

scholarly journals Computational Study of Structural, Molecular Orbitals, Optical and Thermodynamic Parameters of Thiophene Sulfonamide Derivatives

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 211
Author(s):  
Adeel Mubarik ◽  
Nasir Rasool ◽  
Muhammad Ali Hashmi ◽  
Asim Mansha ◽  
Muhammad Zubair ◽  
...  
Keyword(s):  
Energy Gap ◽  
Computational Study ◽  
Molecular Orbitals ◽  
Biologically Active ◽  
Chemical Hardness ◽  
Geometrical Parameters ◽  
Frontier Molecular Orbitals ◽  
Lumo Energy ◽  
Stable Compound ◽  
Homo Lumo

Thiophene and sulfonamide derivatives serve as biologically active compounds, used for the manufacture of large numbers of new drugs. In this study, 11 selected derivatives of thiophene sulfonamide were computed for their geometric parameters, such as hyperpolarizability, chemical hardness (ƞ), electronic chemical potential (μ), electrophilicity index (ω), ionization potential (I), and electron affinity (A). In addition, FT-IR and UV-Vis spectra were also simulated through theoretical calculations. The geometrical parameters and vibrational frequencies with assignments of the vibrational spectra strongly resemble the experimentally calculated values. Besides, the frontier molecular orbitals were also determined for various intramolecular interactions that are responsible for the stability of the compounds. The isodensity surfaces of the frontier molecular orbitals (FMOs) are the same pattern in most of the compounds, but in some compounds are disturbed due to the presence of highly electronegative hetero-atoms. In this series of compounds, 3 shows the highest HOMO–LUMO energy gap and lowest hyperpolarizability, which leads to the most stable compound and less response to nonlinear optical (NLO), while 7 shows the lowest HOMO–LUMO energy gap and highest hyperpolarizability, which leads to a less stable compound and a high NLO response. All compounds have their extended three-dimensional p-electronic delocalization which plays an important role in studying NLO responses.

Prediction of Antiglycation Activity by Calculating the Energies of Frontier Molecular Orbitals for New 4-Hydroxy-1,4-Dihydroazolo[5,1-c]-1,2,4-Triazines Used as an Example

2020 ◽  
Vol 46 (6) ◽  
pp. 1278-1284
Author(s):  
R. A. Litvinov ◽  
R. A. Drokin ◽  
D. D. Shamshina ◽  
M. Yu. Kalenova ◽  
L. E. Usmianova ◽  
...  
Keyword(s):  
Molecular Orbitals ◽  
Frontier Molecular Orbitals

Comparison of P- and As-core-modified porphyrins with the parental porphyrin: a computational study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Aleksey E. Kuznetsov
Keyword(s):  
Computational Study ◽  
Electron Delocalization ◽  
Energy Structure ◽  
Frontier Molecular Orbitals ◽  
The Core ◽  
Potential Applications ◽  
Noticeable Reduction ◽  
Internal Electron ◽  
Porphyrin Core ◽  
Homo Lumo

Abstract The first comparative DFT (B3LYP/6-31G*) study of the Zn-porphyrin and its two derivatives, ZnP(P)4 and ZnP(As)4, is reported. For all three species studied, ZnP, ZnP(P)4 and ZnP(As)4, the singlet was calculated to be the lowest-energy structure and singlet-triplet gap was found to decrease from ca. 41—42 kcal/mol for N to ca. 17—18 kcal/mol for P and to ca. 10 kcal/mol for As. Both ZnP(P)4 and ZnP(As)4 were calculated to attain very pronounced bowl-like shapes. The frontier molecular orbitals (MOs) of the core-modified porphyrins are quite similar to the ZnP frontier MOs. For the HOMO-2 of the core-modified porphyrins due to the ZnP(P)4/ZnP(As)4 bowl-like shapes we might suppose the existence of “internal” electron delocalization inside the ZnP(P)4/ZnP(As)4 “bowls”. Noticeable reduction of the HOMO/LUMO gaps was calculated for ZnP(P)4 and ZnP(As)4, by ca. 1.10 and 1.47 eV, respectively, compared to ZnP. The core-modification of porphyrins by P and especially by As was found to result in significant decrease of the charge on Zn-centers, by ca. 0.61—0.67e for P and by ca. 0.69—0.76e for As. Charges on P- and As-centers were computed to have large positive values, ca. 0.41—0.45e and ca. 0.43—0.47e, for P and As, respectively, compared to significant negative values, ca. −0.65 to −0.66e for N. The porphyrin core-modification by heavier N congeners, P and As, can noticeably modify the structures, electronic, and optical properties of porphyrins, thus affecting their reactivity and potential applications.

Polarized .pi.-frontier molecular orbitals. A method for predicting diastereofacial selectivities

1993 ◽  
Vol 115 (10) ◽  
pp. 4024-4030 ◽  
Author(s):  
Xiao Ling Huang ◽  
J. J. Dannenberg ◽  
Miquel Duran ◽  
Juan Bertran
Keyword(s):  
Molecular Orbitals ◽  
Frontier Molecular Orbitals
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