No abstract

The emergence of artemisinin-resistant variants of Plasmodium falciparum necessitates the urgent search for novel antimalarial drugs. In this regard, an in silico study to screen antimalarial drug candidates from a series of benzimidazole-thiosemicarbazone hybrid molecules with interesting antiplasmodial properties and explore their falcipain-2 (FP2) inhibitory potentials has been undertaken herein. FP2 is a key cysteine protease that degrades hemoglobin in Plasmodium falciparum and is an important biomolecular target in the development of antimalarial drugs. Pharmacokinetic properties, ADMET profiles, MM/GBSA-based binding free energies, reaction mechanisms, and associated barrier heights have been investigated. DFT, molecular dynamics simulation, molecular docking, and ONIOM methods were used. From the results obtained, four 4 N -substituted derivatives of the hybrid molecule ( E )-2-(1-(5-chloro-1 H -benzo[ d ]imidazol-2-yl)ethylidene)hydrazine-1-carbothioamide (1A) denoted 1B, 1C, 1D, and 1E are drug-like and promising inhibitors of FP2, exhibiting remarkably small inhibitory constants (5.94 × 10 –14 − 2.59 × 10 –04 M) and favorable binding free energies (−30.32 to −17.17 kcal/mol). Moreover, the ONIOM results have revealed that 1B and possibly 1C and 1D may act as covalent inhibitors of FP2. The rate-determining step of the thermodynamically favorable covalent binding mechanism occurs across a surmountable barrier height of 24.18 kcal/mol in water and 28.42 kcal/mol in diethyl ether. Our findings are useful for further experimental investigations on the antimalarial activities of the hybrid molecules studied. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s11030-022-10594-3.

This work reports on the density functional theory (DFT) and its time-dependent extension (TD-DFT) study of the structural, electronic, and charge transport properties of 2-(5-mercapto-1,3,4-oxadiazol-2-yl) phenol (MODP) and some of its transition M2+ complexes (M = Fe, Co, Cu, Ni, Zn, Pd, Pt). Reorganization energy, integral charge transfer, mobility, open circuit voltage, and electronic properties of these compounds have been calculated by employing the global hybrid functional PBE0 in conjunction with the Karlsruhe basis set def2-TZVP. Results show that MODP and its transition metal complexes are good electron donors for organic solar cells (OSC) owing to their relatively higher HOMO and LUMO energies compared to the prototypical (6, 6)-phenyl-C61-butyric acid methyl ester (PCBM). Energy gaps ranging between 2.502 and 4.455 eV, energy driving forces (∆EL-L) ranging between 2.08 and 2.44 eV, and large open circuit voltages ( V OC ) ranging from 1.12 to 2.05 eV were obtained. The results also revealed that MODP and its Pd(II) and Pt(II) complexes could serve as ambipolar charge transport materials owing to their very small reorganization energies, integral charge transfers, high rate charge transfers, and mobilities. All studied molecules showed OSC donor and hole/electron transport characteristics required by organic light-emitting diodes (OLEDs). Based on these results, new ways for designing charge transport materials for OLEDs as well as donor materials in OSCs are proposed.

Here, we report the findings from a study on the charge transport and nonlinear optical (NLO) properties of N-(4-methoxybenzylidene) isonicotinohydrazone (INH) and some of its derivatives named INH1-INH15. The density functional theory (DFT) approach was used for ground state computations at the B3LYP-D/6-311G (d,p) level of theory, while the time-dependent density functional theory (TD-DFT) was carried out at the CAM-B3LYP/6-311G (d,p) level. The results show that the energy gaps of all the studied compounds range from 3.933 to 4.645 eV. INH3 and INH4 have the lowest electron and hole reorganization energies (i.e., 0.409 and 0.634 eV, respectively) and can thus be classified as moderate electron and hole-carrying materials for organic light-emitting diode (OLED) applications. TD-DFT computations demonstrate that an extension of the conjugation (in INH2 and INH3) increases the oscillator strength, improving the NLO response. According to the NLO data, INH2 and INH3 have higher static isotropic polarizabilities (38.509 and 37.986 × 10−24 esu, respectively) and second hyperpolarizabilities (54.440 and 57.598 × 10−36 esu, respectively), while INH4 and INH13 have higher first hyperpolarizability values (11.944 and 10.939 × 10−30 esu, respectively). The results reveal that INH derivatives with different groups are viable alternatives for OLED and NLO applications.