DFT and TDDFT study of chemical reactivity and spectroscopic properties of M(TePh)2 [TMEDA] M=Zn, Cd, and Hg complexes

Biotransformation of 1-nitro-2-phenylethane ⟶ 2-phenylethanol from fungi species of the Amazon biome: an experimental and theoretical analysis

CONTEXT

Natural products and their biotransformation procedures are a powerful source of new chromophores with potential applications in fields like biology, pharmacology and materials science. Thus, this work discusses about the extraction procedure of 1-nitro-2-phenylethane (1N2PE) from Aniba canelilla, its biotransformation setup into 2-phenylethanol (2PE) using four fungi, Lasiodiplodia caatinguensis (phytopathogenic fungus from Citrus sinensis), Colletotrichum sp. (phytopathogenic fungus from Euterpe oleracea), Aspergillus flavus and Rigidoporus lineatus isolated from copper mining waste located in the interior of the Brazilian Amazon. A detailed experimental and theoretical vibrational analysis (IR and Raman) have allowed us to perform some charge transfer effects on the title compounds (push-pull effect) by monitoring specific vibrational modes of their electrophilic and nucleophilic molecular sites. The solvent interactions promote molecular conformations that affect the vibrational spectra of the donor and acceptor groups, as can be seen comparatively in the gas and aqueous solution spectra, an effect possibly related to the bathochromic shift in the calculated optical spectrum of the compounds. The nonlinear optical behavior shows that while the solvent reduces the response of 1N2PE, the response of 2PE increases the optical parameters, which presents low refractive index (n) and first hyperpolarizability. (β ) is almost eight times that reported for urea (42.79 a.u.), a common nonlinear optical material. Furthermore, the bioconversion goes from an electrophilic to a nucleophilic compound, affecting its molecular reactivity.

METHODS

1N2PE was obtained from Aniba canelilla, whose essential oil is constituted of∼ 80 % of 2PE. The A. canelilla essential oil was extracted under hydrodistillation. The biotransformation reactions were performed in autoclaved liquid media (100 mL) composed of malt extract (2%) in 250 mL Erlenmeyer flask. Each culture was incubated in an orbital shaker (130 rpm) at32 ∘ C during 7 days and after that, 50 mg of 1N2PE (80%) were diluted in 100μ L of dimethylsulfoxide (DMSO) and added to the reactions flasks. Aliquots (2 mL) were removed using ethyl acetate (2 mL) and analyzed by GC-MS (fused silica capillary col1umn, Rtx -5MS 30 m× 0.25 mm× 0.25μ m) in order to determine the amount of 1N2PE biotransformation. FTIR 1N2PE and 2PE spectra were obtained by attenuated total reflectance (ATR), using a Agilent CARY 630 spectrometer, in the spectral region 4000-650 cm− 1 . The quantum chemical calculations were carried out in the Gaussian 09 program while the DICE code was used to perform the classical Monte Carlo simulations and generate the liquid environment using the classical All-Atom Optimized parameters for Liquid Simulations (AA-OPLS). All nonlinear optical properties, reactive parameters, and electronic excitations were calculated using the Density Functional Theory framework coupled to the standard 6-311++G(d,p) basis set.

Pharmaceutical cocrystal consisting of ascorbic acid with p-aminobenzoic acid and paracetamol

As small molecule drugs become harder to develop and less cost effective for patient use, efficient strategies for their property improvement become increasingly important for global health initiatives. As a new crystal engineering strategy, cocrystals have opened a new way to modify the physicochemical properties of pharmaceutical solids. Improvements in the physical properties of Active Pharmaceutical Ingredients (APIs) without changes in the covalent chemistry have been possible through the application of binary component solids. In this work, a pharmaceutical cocrystal of ascorbic acid (A) + para-aminobenzoic acid (B) and ascorbic acid (A) + paracetamol (P) cocrystal are synthesized and characterized by PXRD, DSC, and FT-IR. FT-IR indicates the kind of interactions occurring between API and coformer. The DSC thermogram for (A–B) cocrystal showed a single endothermic peak attributed to the melting temperature at 155 °C. The thermal behavior of the cocrystal was distinct with different melting temperatures from that seen with either of the individual components; this suggests the formation of a new phase. As molecular modeling is presented as a support to the experiment, a computational study using density functional theory (DFT) at the level of the WB97XD functional and 6-311 + G (d, p) basis set was carried out using the Gaussian 09 program. This theoretical study made it possible to calculate the energetic properties, the intramolecular hydrogen bonds as well as the thermodynamic properties for the two cocrystals.

A DFT analysis of electronic, reactivity, and NLO responses of a reactive orange dye: the role of Hartree-Fock exchange corrections

An experimental and theoretical study based on DFT/TD-DFT approximations is presented to understand the nature of electronic excitations, reactivity, and nonlinear optical (NLO) properties of reactive orange 16 dye (RO16), an azo chromophore widely used in textile and pharmacological industries. The results show that the solvent has a considerable influence on the electronic properties of the material. According to experimental results, the absorption spectrum is formed by four intense transitions, which have been identified as [Formula: see text] states using TD-DFT calculations. However, the TD-DFT results reveal a weak [Formula: see text] in the low-lying spectral region. Continuum models of solvation indicate that these states suffer from bathochromic (ca. 15 nm) and hypsochromic shifts (ca. 4 nm), respectively. However, the expected blue shift for the absorption [Formula: see text] is only described using long-range or dispersion-corrected DFT methods. RO16 is classified as a strong electrophilic system, with electrophilicity ω > 1.5 eV. Concerning the nucleophilicity parameter (N), from vacuum to solvent, the environment is active and changes the nucleophilic status from strong to moderate nucleophile (2.0 ≤ N ≤ 3.0 eV). The results also suggest that all electrical constants are strongly dependent on long-range and Hartree-Fock exchange contributions, and the absence of these interactions gives results far from reality. In particular, the results for the NLO response show that the chromophore presents a potential application in this field with a low refractive index and first hyperpolarizability ca. 214 times bigger than the value usually reported for urea (β = 0.34 × 10^- 30 esu), which is a standard NLO material. Concerning the solvent effects, the results indicate that the polarizability increases [Formula: see text] esu from gas to solvent while the first hyperpolarizability is calculated as [Formula: see text] esu, ca. 180%, regarding the vacuum. The results suggest RO16 is a potential compound in NLO applications. Graphical Abstract The frontier molecular orbitals, and the inverse relation between the energy-gap (E_gap) and the first hyperpolarizability (β).