| 1. |
- Pandey, Jaya, et al.
(författare)
-
Studies of molecular structure, hydrogen bonding and chemical activity of a nitrofurantoin-L-proline cocrystal : a combined spectroscopic and quantum chemical approach
- 2016
-
Ingår i: RSC Advances. - 2046-2069. ; 6:78, s. 74135-74154
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrofurantoin (NTF) has been used as an antibacterial drug to treat bacterial infections of the urinary tract. The purpose of this work is to predict the hydrogen bonds (potential synthons) present in the cocrystal of nitrofurantoin-L-proline (NTF-LP) through a computational approach (DFT calculations) and validate using vibrational spectroscopic studies. The present study illustrates the formation and characterization of the cocrystal of NTF-LP. The molecular structure of the NTF-LP cocrystal has been predicted by forming several models on the basis of the hydrogen bonding patterns observed in other NTF cocrystals. A conformational study and potential energy surface scan have been plotted around three flexible bonds of the cocrystal molecule and two stable conformers have been obtained. NBO analysis of the second order perturbation theory of the Fock matrix suggests that interaction n1O(39) → σ*(N13–H21) is responsible for the stabilization of the molecule. Quantum theory of atoms in molecules (QTAIM) explains that all interactions are medium and partially covalent in nature as ∇2ρBCP > 0, HBCP < 0. The molecular electrostatic potential surface (MEPS) of the cocrystal has been visualized for its most electropositive potential in the region of the NH2+ group and most electronegative potential in the vicinity of the COO− group. The HOMO and LUMO energies and electronic charge transfer (ECT) confirms that charge flows from the co-former (LP) to NTF (API). Local reactivity descriptor parameters have been used to predict the reactive sites of the cocrystal and global reactivity descriptor parameters suggest that the cocrystal is softer thus more reactive in comparison to NTF. The experimental and theoretical results support the formation of the cocrystal through the strong hydrogen bond present between the NH group of NTF and carboxylate COO− group of LP and shows that LP is present in the zwitterionic form.
|
|
| 2. |
- Prajapati, Preeti, et al.
(författare)
-
Combined spectroscopic and quantum chemical studies of ezetimibe
- 2016
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1125, s. 193-203
-
Tidskriftsartikel (refereegranskat)abstract
- Ezetimibe (EZT) is a hypocholesterolemic agent used for the treatment of elevated blood cholesterol levels as it lowers the blood cholesterol by blocking the absorption of cholesterol in intestine. Study aims to combine experimental and computational methods to provide insights into the structural and vibrational spectroscopic properties of EZT which is important for explaining drug substance physical and biological properties. Computational study on molecular properties of ezetimibe is presented using density functional theory (DFT) with B3LYP functional and 6-311++G(d,p) basis set. A detailed vibrational assignment has been done for the observed IR and Raman spectra of EZT. In addition to the conformational study, hydrogen bonding and molecular docking studies have been also performed. For conformational studies, the double well potential energy curves have been plotted for the rotation around the six flexible bonds of the molecule. UV absorption spectrum was examined in methanol solvent and compared with calculated one in solvent environment (IEF-PCM) using TD-DFT/6-31G basis set. HOMO-LUMO energy gap of both the conformers have also been calculated in order to predict its chemical reactivity and stability. The stability of the molecule was also examined by means of natural bond analysis (NBO) analysis. To account for the chemical reactivity and site selectivity of the molecules, molecular electrostatic potential (MEPS) map has been plotted. The combination of experimental and calculated results provide an insight into the structural and vibrational spectroscopic properties of EZT. In order to give an insight for the biological activity of EZT, molecular docking of EZT with protein NPC1L1 has been done.
|
|
| 3. |
- Srivastava, Karnica, et al.
(författare)
-
Vibrational analysis and chemical activity of paracetamol-oxalic acid cocrystal based on monomer and dimer calculations : DFT and AIM approach
- 2016
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:12, s. 10024-10037
-
Tidskriftsartikel (refereegranskat)abstract
- The study of structural and spectral characteristics of a paracetamol-oxalic acid (PRA-OXA) cocrystal has been carried out using two models (monomer and dimer), with the aim to understand the supramolecular structure and intramolecular interactions within the cocrystal. The cocrystal has been characterized by infrared and Raman spectroscopy combined with quantum chemical calculations molecular electrostatic potential surface (MEPS), frontier orbital analysis and electronic reactivity descriptors were used to understand the role of interactions involved in affecting the chemical reactivity of individual molecules in the cocrystal. It is observed that the C=O, N-H and O-H groups of paracetamol are involved in hydrogen bonds to form cocrystals. NBO analysis suggests that the two types of interactions LP(1)(N8) -> pi*(C9-O10) and LP(2)(O10) -> sigma*(O25-H28) are responsible for the stability of the molecule. AIM analysis suggested that the non-covalent interactions are moderate in nature. The calculated HOMO-LUMO energies reveal that the charge transfer occurs within the cocrystal. Chemical reactivity parameters show that the cocrystal is more active than paracetamol.
|
|
