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A DFT investigation of the influence of α,β unsaturation in chemical reactivity of coumarin and some hydroxy coumarins
Published in Tanmoy Chakraborty, Prabhat Ranjan, Anand Pandey, Computational Chemistry Methodology in Structural Biology and Materials Sciences, 2017
M. A. Jaseela, T. M. Suhara, K. Muraleedharan
From the theoretical point of view, Quantum mechanical studies related with reactivity and physical properties of some Coumarin derivatives are demonstrated that DFT/B3LYP/6–311G (2d, 2p) is a reliable method and basis set for the calculation of geometries and related properties of them [39]. The gas phase structures of molecules under study in the ground state are optimized by performing DFT with Beck’s three parameters [2] for exchange interaction and Lee-Yang-Parr [26] is used to consider correlation functional (B3LYP) with 6–311G (2d, 2p) basis set. The vibration analysis is also performed in order to ensure that the optimized geometries are corresponding to a true minimum not a transition state. All computational chemistry calculations are done using Gaussian 09W simulation package [17]. Natural Bond Orbital (NBO) analysis implemented in GAUSSIAN 09W package is carried out at the same level of theory to get a good understanding of contributions from each atom in the formation of different molecular orbitals and various second order interactions exist between the subsystems. In order to study the extent of NLO property the polarisbility and hyper polarisability are calculated. The local (or regional) reactivity descriptors, condensed Fukui functions, are evaluated from single point calculation in terms of the molecular coefficients and the overlap matrix of the system. The optimized molecular geometries are utilized for the single point energy calculations with the same level of theory for anions and cations of the considering molecules in the ground state with doublet multiplicity. The individual atomic charges are calculated by natural population analysis (NPA) from NBO results, are used to calculate the Fukui functions of corresponding reactive sites. TD-DFT is used for the evaluation of absorption (UV-Vis) spectra of molecules by including one set of diffuse function in the basis set.
Synthesis, quantum chemical calculations and molecular docking studies of 2-ethoxy-4[(2-trifluromethyl-phenylimino)methyl]phenol
Published in Molecular Physics, 2020
Towseef Ahmad Hajam, H. Saleem, M. Syed Ali Padhusha, K. K. Mohammed Ameen
The natural bond orbital (NBO) analysis is a calculated bonding orbital with maximum electron density (ED) which is used to determine intra-molecular and inter-molecular bonding interactions, bond structures, bond species and natural atomic charges in a molecular system. In addition, it is used to study inter-molecular charge transfers (ICT) or hyperconjugation interactions and the stability between Lewis type filled orbitals and non-Lewis type vacancy orbitals. The hyperconjugation interaction energy (or the stabilisation energy, E(2)) shows the interaction between donor and acceptor groups. The ED delocalisation between occupied bonded orbitals and unoccupied non-bonded orbitals corresponds to stabilise donor acceptor interaction [54]. The interactions result a loss of occupancy from the localised NBO of the idealised Lewis structure into an empty non-Lewis orbital. For each donor (i) and acceptor (j) orbital the stabilisation energy E(2) associated with the delocalisation i→j is estimated as where qi represents occupancy of donor orbital, ϵi and ϵj are the diagonal elements and F(i,j) is the off diagonal NBO Fock matrix element [55,56].
Synthesis, spectral characterization, DFT, and molecular docking studies of metal(II) complexes derived from thiophene-2-carboxaldehyde and 2-amino-6-picoline
Published in Journal of Coordination Chemistry, 2019
Liji John, R. Selwin Joseyphus, I. Hubert Joe
The NBO analysis refers to a set of mathematical algorithms for analyzing electronic wavefunctions in the language of localized Lewis-like chemical bonds. Delocalization of electron density between occupied Lewis and formally unoccupied non-Lewis NBO orbitals correspond to a stabilizing donor–acceptor interaction, resulting from the second-order Fock matrix. The stabilization energy corresponding to the transfer of electrons from the lone pair of azomethine nitrogen, LP(1)N11\LP(1) N25 to metal atoms σ*(M-Cl49\M-Cl50) during complex formation is found to be 3.94 kcal/mol. The charge transfer also occurred towards ligand’s thiophene [LP(1)N11\LP(1)N25 → σ*(C2-C3)\σ*(C29-C30)] and pyridine [LP(1)N11\LP(1)N25 → σ*(C12-C13)\σ*(C36-C37)] fragments with stabilization energy 0.46 and 1.11 kcal/mol, respectively. Comparison of the stabilization energy of these interactions shows that the charge transfer towards the metal atom is higher than thiophene and pyridine rings. NBO analysis confirms C-H···N intramolecular hydrogen bonding formed by the orbital overlap between the lone pair LP(1)(N17) with σ*(C9-H10) and LP(1) (N41) with σ*(C56-H27) antibonding orbital having stabilization energy of 0.28 kcal/mol in the ligand and complexes. The other important interactions are electron donation from the lone pairs of thiophene sulfur (S5,S32) and pyridine nitrogen (N17,N41) to their neighboring anti-bonding orbitals. The interactions among them with high E(2) value (9.51 and 9.68 kcal/mol) are LP(2)S5 → σ*(C3-C4) and LP(2)S32 → σ*(C30-C31), respectively, are given in Table 2.
Theoretical modelling of encapsulation of the Altretamine drug into BN(9,9-5) and AlN(9,9-5) nano rings: a DFT study
Published in Molecular Physics, 2019
Mehrnoosh Khaleghian, Fatemeh Azarakhshi
NBO analysis is an important method for studying intra- and inter-molecular bonding and interaction between bonds in molecular systems [37]. The electron delocalisation from donor orbitals (full NBOs) to acceptor orbitals (empty NBOs) describes a conjugative electron transfer process between them [42]. For each donor orbital (i) and acceptor orbital (j), the stabilisation energy E(2) associated with the delocalisation i→j is computed [42]: