On the Quantum Chemical Nature of Lead(II) “Lone Pair”

We study the quantum chemical nature of the Lead(II) valence basins, sometimes called the lead “lone pair”. Using various chemical interpretation tools, such as molecular orbital analysis, natural bond orbitals (NBO), natural population analysis (NPA) and electron localization function (ELF) topological analysis, we study a variety of Lead(II) complexes. A careful analysis of the results shows that the optimal structures of the lead complexes are only governed by the 6s and 6p subshells, whereas no involvement of the 5d orbitals is found. Similarly, we do not find any significant contribution of the 6d. Therefore, the Pb(II) complexation with its ligand can be explained through the interaction of the 6s2 electrons and the accepting 6p orbitals. We detail the potential structural and dynamical consequences of such electronic structure organization of the Pb (II) valence domain.

Download Full-text

Optimized Geometry, Charge Distributions, Frontier Molecular Orbital Analysis and NLO Efficiency of BIS (4-Methoxyanilinium) Adipate by Quantum Chemical Calculations

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.a1175.1291s419 ◽

2019 ◽

Vol 9 (1S3) ◽

pp. 329-340

Keyword(s):

Charge Transfer ◽

Quantum Chemical ◽

Molecular Geometry ◽

Basis Sets ◽

Frontier Molecular Orbital ◽

Mulliken Charge ◽

Quantum Chemical Analysis ◽

Molecular Orbital Analysis ◽

Orbital Analysis ◽

Good Agreement

In this work, optimized molecular geometry, vibrational and electronic properties of Bis(4-methoxylanilinium) adipate (4MAA) was obtained by Quantum chemical analysis using 6-311++G(d,p) basis sets. The experimental and computation vibrational spectra have been discussed. Experimental spectra of the 4MAA were recorded in the region 4000–400 cm-1 . The experimental and computational assignments were found to be in good agreement. FMO energies showed that charge transfer had occurred within the molecule. Mulliken charge distribution of the present compound was studied systematically. Furthermore, the hyperpolarizability calculations were analyzed.

Download Full-text

On the Origin of the Bohlmann Bands

Canadian Journal of Chemistry ◽

10.1139/v74-567 ◽

1974 ◽

Vol 52 (22) ◽

pp. 3787-3792 ◽

Cited By ~ 30

Author(s):

Saul Wolfe ◽

H. Bernhard Schlegel ◽

Myung-Hwan Whangbo ◽

Fernando Bernardi

Keyword(s):

Experimental Observation ◽

Molecular Orbital ◽

Lone Pair ◽

Electron Pairs ◽

Theoretical Support ◽

Nuclear Contribution ◽

Bond Strengths ◽

Molecular Orbital Analysis ◽

Orbital Analysis

A perturbational molecular orbital analysis has been performed of the strengths of the CH bonds of methylamine and methanol in their staggered conformations. This analysis leads to the prediction that a CH bond anti-coplanar to a directed lone pair is stronger than a gauche CH bond, and is in disagreement with experimental observation. The origin of the disagreement is to be found in the underestimation of the role of the nuclear–nuclear contribution to the bond strengths. Abinitio computation of the gauche and anti stretching force constants of methylamine provides quantitative theoretical support for the view that these differ because of a nuclear-dominated effect. It is suggested that effects, analogous to those observed in the Bohlmann bands, may be seen even in the absence of nonbonded electron pairs.

Download Full-text

Conformational Aspects of Substituents in Enamines. X-Ray Structure Analyses and Quantum Chemical Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-1992-7-812 ◽

1992 ◽

Vol 47 (7-8) ◽

pp. 869-876 ◽

Cited By ~ 2

Author(s):

Gerhard Raabe ◽

Wolfgang Karl ◽

Dieter Enders ◽

Jörg Fleischhauer

Keyword(s):

Molecular Structure ◽

Double Bond ◽

Ab Initio Calculations ◽

Ab Initio ◽

Quantum Chemical ◽

Lone Pair ◽

Phenyl Group ◽

Careful Analysis ◽

X Ray ◽

Nitrogen Lone Pair

Abstract X-ray structure determination of the enamine (Z)-4-(6'-t-butoxycarbonyl-2',2'-dimethyl-5'-phenyl- 3'-hexen-3'-yl)morpholine (1) reveals that certain bulky groups may enforce a relative orientation of the molecular subunits without conjugative interaction between the nitrogen lone pair and the olefinic double bond. According to the results of quantum chemical ab initio calculations the experimentally found arrangement would be the least favourable one in the absence of such substituents. A careful analysis of the molecular structure of 1 shows that this unusual arrangement is due to the presence of both, the a- and the ß-substituent. In (E)-4-(3'-t-butoxycarbonylmethyl-1'-phenyl-1'-penten-1'-yl)morpholine (2) rather the nitrogen lone pair than the phenyl n system is in conjugation with the olefinic double bound. The results of ab initio calculations on model compounds show that conjugation of the double bond with the nitrogen lone pair is by 2 - 6 kcal/mol more favourable than conjugative interaction between the phenyl group and the C = C bond. Closer examination of the molecular structure of 2, however, led to the conclusion that it is predominantly the ß-substituent which forces the phenyl ring in a position where conjugation with the enamine double bond is not possible

Download Full-text

Effect of the intramolecular hydrogen bond in the active metabolite analogs of leflunomide for blocking the Plasmodium falciparum dihydroorotate dehydrogenase enzyme: QTAIM, NBO, and docking study

Current Computer - Aided Drug Design ◽

10.2174/1573409916666200527133126 ◽

2020 ◽

Vol 16 ◽

Author(s):

Reihaneh Heidarian ◽

Mansoureh Zahedi-Tabrizi

Keyword(s):

Hydrogen Bond ◽

Plasmodium Falciparum ◽

Molecular Orbital ◽

Intramolecular Hydrogen Bond ◽

Active Metabolite ◽

Chemical Hardness ◽

Dihydroorotate Dehydrogenase ◽

Molecular Orbital Analysis ◽

Intramolecular Hydrogen ◽

Orbital Analysis

: Leflunomide (LFM) and its active metabolite, teriflunomide (TFM), have drawn a lot of attention for their anticancer activities, treatment of rheumatoid arthritis and malaria due to their capability to inhibit dihydroorotate dehydrogenase (DHODH) and Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. In this investigation, the strength of intramolecular hydrogen bond (IHB) in five analogs of TFM (ATFM) has been analyzed employing density functional theory (DFT) using B3LYP/6-311++G (d, p) level and molecular orbital analysis in the gas phase and water solution. A detailed electronic structure study has been performed using the quantum theory of atoms in molecules (QTAIM) and the hydrogen bond energies (EHB) of stable conformer obtained in the range of 76-97 kJ/mol, as a medium hydrogen bond. The effect of substitution on the IHB nature has been studied by natural bond orbital analysis (NBO). 1H NMR calculations show an upward trend in the proton chemical shift of the enolic proton in the chelated ring (14.5 to 15.7ppm) by increasing the IHB strength. All the calculations confirmed the strongest IHB in 5-F-ATFM and the weakest IHB in 2-F-ATFM. Molecular orbital analysis, including the HOMO-LUMO gap and chemical hardness, was performed to compare the reactivity of inhibitors. Finally, molecular docking analysis was carried out to identify the potency of inhibition of these compounds against PfDHODH enzyme.

Download Full-text

Magnetism and structure of a novel trinuclear cluster compound of divalent copper

Australian Journal of Chemistry ◽

10.1071/ch9692527 ◽

1969 ◽

Vol 22 (12) ◽

pp. 2527 ◽

Cited By ~ 53

Author(s):

R Beckett ◽

R Colton ◽

BF Hoskins ◽

RL Martin ◽

DG Vince

Keyword(s):

Structural Data ◽

Hydroxyl Group ◽

Cluster Compound ◽

X Ray Diffraction ◽

Trinuclear Cluster ◽

Metal Atoms ◽

Doublet Ground State ◽

Molecular Orbital Analysis ◽

Orbital Analysis ◽

Unusual Type

The magnetic properties of a series of salts of the type [Cu3L3OH]2+ (where HL is pyridine-2-aldehyde oxime and L is the deprotonated ligand) have been examined. All of the compounds showed a magnetic moment of 1.00 B.M. per copper atom over a wide temperature range which suggests that the cation contains a trinuclear cluster of interacting copper atoms. The crystal structure of Cu3L3OH(SO4),xH2O has been determined by single- crystal X-ray diffraction techniques and confirms that the complex does indeed contain an unusual type of trinuclear cluster of metal atoms. The three copper atoms form an equilateral triangle and the sulphato group exhibits a highly novel ?tripod? bridging function to the Cu3 triangle. On the other side of the triangle, the hydroxyl group also bridges to all the metal atoms. A qualitative molecular orbital analysis not only suggests that the hydroxyl group is involved in four-centre bonding with the Cu3 triads, but also highlights its role in reducing the spin of the trimer so that only a doublet ground state is populated between 80-300�K. However, the alternative super-exchange mechanism cannot be ruled out by the magnetic and structural data.

Download Full-text

UPS Study of [2,2] (2,5)Furanophane and [2,2] (2,5)Thiophenophane Evidence Regarding the Importance of Through Bond and Through Space Interactions

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-0815 ◽

1978 ◽

Vol 33 (8) ◽

pp. 959-963 ◽

Cited By ~ 5

Author(s):

Fernando Bernardi ◽

Andrea Bottoni ◽

Francesco Paolo Colonna ◽

Giuseppe Distefano ◽

Ugo Folli ◽

...

Keyword(s):

Molecular Orbital ◽

Photoelectron Spectra ◽

Molecular Orbital Analysis ◽

Orbital Analysis

The ultraviolet photoelectron spectra of [2,2](2,5)furanophane (FUPH) and [2,2](2,5)thiophenophane (THPH) have been analyzed on the basis of a perturbational molecular orbital analysis, by comparison with CNDO/2 computations and by correlating them with the spectra of related molecules. Through space and through bond interactions between the two heteroaromatic rings are shown to be important in determining the ordering of the outermost MO’s in this class of compounds.

Download Full-text