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As the knowledge of the predominant molecular structure of antioxidant and anticancer flavonoid rutin in solution is very important for understanding the mechanism of action, a quantum chemical investigation of plausible rutin structures including solvent effects is of relevance. In this work, DFT calculations were performed to find possible minimum energy structures for the rutin molecule. 1H NMR chemical shift DFT calculations were carried out in DMSO solution using the polarizable continuum model (PCM) to simulate the solvent effect. Analysis of the experimental and theoretical 1H NMR chemical shift profiles offers a powerful fingerprint criterion to determine the predominant molecular structure in solution. Therefore, our aim is to find the best match between experimental (in DMSO‐d) and theoretical (PCM–DMSO) 1H NMR spectrum profiles. Among 34 optimized structures located on the potential energy surface, we found that structure 32, with a B‐ring deviated 30° from a planar configuration (geometry usually assumed for polyphenols), showed an almost perfect agreement with experimental the 1H NMR pattern when compared to the corresponding fully optimized planar geometry. This structure is also predicted as the global minimum based on room‐temperature Gibbs free energy calculations in solution and, therefore, should be experimentally observed. This is new and valuable structural information regarding structure–activity relationship studies, and such information is hard to obtain by experimentalists without the aid of the X‐ray diffraction technique.

B3LYP/6-31G optimized structures of carbon nanotube oxidized model. The left and right pictures show the oxidized molecules on the cap and tubular regions, respectively.

In this work we report theoretical quantum chemical design and investigation of supramolecular structures formed by cisplatin and single wall carbon nanotube (SWCNT). Through Density Functional Theory (DFT) calculations, plausible modes of interaction between cisplatin and SWCNT zigzag (12,0) model were found: inclusion and adsorption complex forms. B3LYP/6-31G(d,p)/Lanl2DZ calculations of NMR chemical shifts for the free and interacting molecular structures showed very promising to assist the experimentalists to identify these structures. Our results strongly indicate that the cisplatin-nanotube system form a stable molecular complex that can be used as a new drug delivery device.

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Capped carbon cones, known as carbon nanohorns (CNHs), are currently considered to be promising drug carrier agents. To explore the drug-carrying ability and other properties for practical use, the chemistry of production, functionalization, and characteristics of CNHs must be elucidated. To this end, molecular modeling can complement the experimental results by providing the molecular properties for single idealized molecules. In the present study, distinct structures for CNHs are proposed, and their equilibrium geometries, stability, and infrared spectrum are discussed. In addition to the opening angle of the cone, the topology of the tips was also changed, giving rise to 12 distinct geometries, which were analyzed by using the density functional-based tight binding approach (DFTB).