Interaction of 5-Fluorouracil on the Surfaces of Pristine and Functionalized Ca12O12 Nanocages: An Intuition from DFT.

The utilization of nanostructured materials for several biomedical applications has tremendously increased over the last few decades owing to their nanosizes, porosity, large surface area, sensitivity, and efficiency as drug delivery systems. Thus, the incorporation of functionalized and pristine nanostructures for cancer therapy offers substantial prospects to curb the persistent problems of ineffective drug administration and delivery to target sites. The potential of pristine (Ca12O12) and formyl (-CHO)- and amino (-NH2)-functionalized (Ca12O12-CHO and Ca12O12-NH2) derivatives as efficient nanocarriers for 5-fluorouracil (5FU) was studied at the B3LYP-GD3(BJ)/6-311++G(d,p) theoretical level in two electronic media (gas and solvent). To effectively account for all adsorption interactions of the drug on the investigated surfaces, electronic studies as well as topological analysis based on the quantum theory of atoms in molecules (QTAIM) and noncovalent interactions were exhaustively utilized. Interestingly, the obtained results divulged that the 5FU drug interacted favorably with both Ca12O12 and its functionalized derivatives. The adsorption energies of pristine and functionalized nanostructures were calculated to be -133.4, -96.9, and -175.6 kcal/mol, respectively, for Ca12O12, Ca12O12-CHO, and Ca12O12-NH2. Also, both topological analysis and NBO stabilization analysis revealed the presence of interactions among O3-H32, O27-C24, O10-C27, and N24-H32 atoms of the drug and the surface. However, 5FU@Ca12O12-CHO molecules portrayed the least adsorption energy due to considerable destabilization of the molecular complex as revealed by the computed deformation energy. Therefore, 5FU@Ca12O12 and 5FU@Ca12O12-NH2 acted as better nanovehicles for 5FU.

Evaluation of the excited state dynamics, photophysical properties, and the influence of donor substitution in a donor-[Formula: see text]-acceptor system.

There have been numerous attempts for the theoretical design of a better donor-[Formula: see text]-acceptor structural framework with improved absorption and emission properties. However, for effective dye designing, it is necessary to understand the electronic and photophysical properties of the dye systems. In this work, we report a detailed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) investigations of the excited state characteristics and the influence of various groups (-HCO, =CH2, (-CH3)2, (HCO)2, and (-OCH3)2) attached to the donor group (-NH2) in a p-nitroaniline D-[Formula: see text]-A system which are symbolized respectively as p-nitroaniline (A), N,N-dimethylnitroaniline (A2), N,N-dicarbonylnitroaniline (A3), N-methylenenitroaniline (A4), and N,N-dimethoxynitroaniline (A5). The first principles DFT and TD-DFT calculations from the ground state (S0) to the first five excited states: (S0→S1), (S0→S2), (S0→S3), (S0→S4), and (S0→S5) were utilized to explore the reactivity of D-[Formula: see text]-A system using the conceptual DFT approach, characterization of electron excitation using the hole-electron analysis, visual study of the various real space functions in the hole-electron framework, density of states (DOS), measurement of charge transfer (CT) length of electron excitation ([Formula: see text]), measurement of the overlapping degrees of hole and electron of electron excitation ([Formula: see text]), interfragment charge transfer (IFCT) during electron excitation, and the second-order perturbation energy analysis from the natural bond orbitals (NBO) computation. Results of the excitation studies show that all the studied compounds exhibited an n→[Formula: see text]* localized type for first excitations (S0→S1) on -NO2 group in A, A2, A4, and A5 and -NCl2 in A3. [Formula: see text]→[Formula: see text]* charge transfer excitations were confirmed for S0→S2/S4/S5 in A and A2, S0→S3/S4/S5 in A3 and A5, and S0→S4/S5 in A4. The NBO second-order perturbation energy analysis suggest that the most significant hyperconjugative interactions were [Formula: see text] (54.43kcal/mol), [Formula: see text] (40.82kcal/mol), [Formula: see text] (11.67kcal/mol), [Formula: see text] (29.52kcal/mol), [Formula: see text] (11.55kcal/mol), [Formula: see text] (23.40kcal/mol), and [Formula: see text] (24.88kcal/mol) [Formula: see text](24.64kcal/mol), which respectively corresponds to the A, A2, A3, A4, and A5 D-[Formula: see text]-A systems under investigation, and these strong interactions stabilize the systems.

Understanding the aqueous chemistry of quinoline and the diazanaphthalenes: insight from DFT study.

The inter-fragment interactions at various binding sites and the overall cluster stability of quinolone (QNOL), cinnoline (CNOL), quinazoline (QNAZ), and quinoxaline (QNOX) complexes with H2O were studied using the density functional theory (DFT) approach. The adsorption and H-bond binding energies, and the energy decomposition mechanism was considered to determine the relative stabilization status of the studied clusters. Scanning tunneling microscopy (STM), natural bonding orbitals (NBO) and charge decomposition were studied to expose the electronic distribution and interaction between fragments. The feasibility of formations of the various complexes were also studied by considering their thermodynamic properties. Results from adsorption studies confirmed the actual adsorption of H2O molecules on the various binding sites studied, with QNOX clusters exhibiting the best adsorptions. Charge decomposition analysis (CDA) revealed significant charge transfer from substrate to H2O fragment in most complexes, except in QNOL, CNOL and QNAZ clusters with H2O at binding position 4, where much charges are back-donated to substrate. The O---H inter-fragment bonds was discovered to be stronger than counterpart N---H bonds in the complexes, whilst polarity indices confirmed N---H as more polar covalent than O---H bonds. Thermodynamic considerations revealed that the formation process of all studied complexes are endothermic (+ve ΔH f ) and non-spontaneous (+ve ΔG f ).

Aromaticity indices, electronic structural properties, and fuzzy atomic space investigations of naphthalene and its aza-derivatives.

The aromaticity and CDFT properties of naphthalene and its aza-derivatives were theoretically investigated using density functional theory (DFT) electronic structure method. The reactivity and chemistry of Azanaphthalene (1-AN), 1, 2-diazanaphthalene (1, 2-DAN), 1, 3-diazanaphthalene (1, 3-DAN), 1, 4-diazanaphthalene (1,4-DAN), 1, 5-diazanaphthalene (1, 5-DAN), 1, 6-diazanaphthalene (1, 6-DAN), 1, 7-diazanaphthalene (1,7-DAN) and 1, 8-diazanaphthalene (1, 8-DAN) were thoroughly explored and predicted focusing more on the fuzzy atomic space analysis, quantum chemical descriptors (CDFT), natural bond orbital (NBO), and structural electronic properties. The CDFT is focused on predicting the condensed Fukui function and dual descriptors along with condensed local electrophilicity and nucleophilicity investigation. From the aromaticity computational study, 1,7-DAN gave PDI, FLU, FLU- π , PLR, HOMA, BIRD and LOLIPOP values of approximately one (1) was found to be the most aromatic in the group, and strongest π -stacking ability. The aromaticity follows the trend: 1, 7-DAN > 1, 8-DAN > 1, 5-DAN > 1, 6-DAN > 1, 4-DAN > 1, 2-DAN > 1-AN > naphthalene. The second order perturbation energy NBO analysis revealed that the 3 highest stabilization energies in the molecules are C6-Na to C3-C4 ( π ∗ - π ∗ 236.90 kcal/mol) of 1, 6-DAN, C3-C4 to C1-C2 ( π ∗ - π ∗ 236.37 kcal/mol) of 1-AN and C7-N10 to C2-C4 ( π ∗ - π ∗ 235 kcal/mol) of 1, 3-DAN.