scholarly journals Modulating the Frontier Orbitals of an Aluminylene for Facile Dearomatization of Inert Arenes

2021 ◽  
Author(s):  
Xin Zhang ◽  
Liu Leo Liu
Keyword(s):  
Chemical Reactivity ◽  
Cycloaddition Reaction ◽  
Lewis Base ◽  
Single Atom ◽  
Frontier Orbitals ◽  
Lewis Bases ◽  
Valence Electrons ◽  
Singlet Carbenes ◽  
Homo Lumo ◽  
Atom Center

Lewis bases are well known to stabilize electron-deficient species. We demonstrate herein that the redox property of a monocoordinated aluminylene 1 featuring only four valence electrons for the shell of Al can be boosted by a Lewis base. The coordination of 1 with an N-heterocyclic carbene (NHC) effectively shrinks the HOMO−LUMO gap, thereby enhancing the reactivity of the ensuing acyclic mono-NHC-stabilized aluminylene 2, which is isoelectronic with singlet carbenes. Moreover, such base coordination completely reverses the predominant chemical reactivity (i.e. electrophilicity/nucleophilicity) of aluminylenes. In marked contrast to 1, 2 readily undergoes a [4+1] cycloaddition reaction with naphthalene and biphenylene at room temperature. Remarkably, the enhanced ambiphilic nature of Al in 2 also enables facile cleavage of aromatic C−C bonds of inert arenes in both intra- and intermolecular fashion affording 3 and 5. The formation of 5 represents the first example of the cleavage of aromatic C(3)−C(4) bond in biphenylene by a single atom center.

scholarly journals Modulating the Frontier Orbitals of an Aluminylene for Facile Dearomatization of Inert Arenes

2021 ◽  
Author(s):  
Xin Zhang ◽  
Liu Leo Liu
Keyword(s):  
Chemical Reactivity ◽  
Cycloaddition Reaction ◽  
Lewis Base ◽  
Single Atom ◽  
Frontier Orbitals ◽  
Lewis Bases ◽  
Valence Electrons ◽  
Singlet Carbenes ◽  
Homo Lumo ◽  
Atom Center

Lewis bases are well known to stabilize electron-deficient species. We demonstrate herein that the redox property of a monocoordinated aluminylene 1 featuring only four valence electrons for the shell of Al can be boosted by a Lewis base. The coordination of 1 with an N-heterocyclic carbene (NHC) effectively shrinks the HOMO−LUMO gap, thereby enhancing the reactivity of the ensuing acyclic mono-NHC-stabilized aluminylene 2, which is isoelectronic with singlet carbenes. Moreover, such base coordination completely reverses the predominant chemical reactivity (i.e. electrophilicity/nucleophilicity) of aluminylenes. In marked contrast to 1, 2 readily undergoes a [4+1] cycloaddition reaction with naphthalene and biphenylene at room temperature. Remarkably, the enhanced ambiphilic nature of Al in 2 also enables facile cleavage of aromatic C−C bonds of inert arenes in both intra- and intermolecular fashion affording 3 and 5. The formation of 5 represents the first example of the cleavage of aromatic C(3)−C(4) bond in biphenylene by a single atom center.

scholarly journals Relativistic Effects on NMR Parameters of Halogen-Bonded Complexes

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4399 ◽  
Author(s):  
Ibon Alkorta ◽  
José Elguero ◽  
Manuel Yáñez ◽  
Otilia Mó ◽  
M. Merced Montero-Campillo
Keyword(s):  
Relativistic Effects ◽  
Lewis Base ◽  
Coupling Constants ◽  
Basic Site ◽  
Lewis Bases ◽  
Nmr Parameters ◽  
Quadrupolar Coupling ◽  
Binary Complexes ◽  
Computational Level ◽  
Bonded Complexes

Relativistic effects are found to be important for the estimation of NMR parameters in halogen-bonded complexes, mainly when they involve the heavier elements, iodine and astatine. A detailed study of 60 binary complexes formed between dihalogen molecules (XY with X, Y = F, Cl, Br, I and At) and four Lewis bases (NH3, H2O, PH3 and SH2) was carried out at the MP2/aug-cc-pVTZ/aug-cc-pVTZ-PP computational level to show the extent of these effects. The NMR parameters (shielding and nuclear quadrupolar coupling constants) were computed using the relativistic Hamiltonian ZORA and compared to the values obtained with a non-relativistic Hamiltonian. The results show a mixture of the importance of the relativistic corrections as both the size of the halogen atom and the proximity of this atom to the basic site of the Lewis base increase.

Solvent and temperature effects on the tautomerization of a carbonitrile molecule: A conductor-like polarizable continuum model (CPCM) study

2021 ◽  
Vol 20 (1) ◽  
pp. 59-68
Author(s):  
Zohreh Khanjari ◽  
Bita Mohtat ◽  
Reza Ghiasi ◽  
Hoorieh Djahaniani ◽  
Farahnaz Kargar Behbahani
Keyword(s):  
Gas Phase ◽  
Solvent Effects ◽  
Continuum Model ◽  
Solvent Polarity ◽  
Polarizable Continuum Model ◽  
Dielectric Constants ◽  
Frontier Orbitals ◽  
Reaction Field ◽  
Polarizable Continuum ◽  
Homo Lumo

This research examined the effects of solvent polarity and temperature on the tautomerization of a carbonitrile molecule at CAM-B3LYP/6-311G (d,p) level of theory. The selected solvents were n-hexane, diethyl ether, pyridine, ethanol, methanol, and water. The solvent effects were examined by the self-consistent reaction field theory (SCRF) based on conductor-like polarizable continuum model (CPCM). The solvent effects were explored on the energy barrier, frontier orbitals energies, and HOMO-LUMO gap. Dependencies of thermodynamic parameters (ΔG and ΔH) on the dielectric constants of solvents were also tested. Specifically, the temperature dependencies of the thermodynamics parameters were studied within 100–1000 K range. The rate constant of the tautomerism reaction was computed from 300 to 1200 K, in the gas phase.

scholarly journals 5-Nitrosalicylic Acid and its Proton-Transfer Compounds with Aliphatic Lewis Bases

2005 ◽  
Vol 58 (1) ◽  
pp. 47 ◽  
Author(s):  
Graham Smith ◽  
Andy W. Hartono ◽  
Urs D. Wermuth ◽  
Peter C. Healy ◽  
Jonathan M. White ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Proton Transfer ◽  
Lewis Base ◽  
Unusual Structure ◽  
Lewis Bases ◽  
Carboxylate Oxygen ◽  
Hydrogen Bonding Interactions ◽  
Polymer Compound ◽  
Proton Transfer Compounds ◽  
Centrosymmetric Dimers

The crystal structures of the proton-transfer compounds of 5-nitrosalicylic acid (5-nsa) with morpholine (morph), hexamethylenetetramine (hmt), and ethylenediamine (en) have been determined and their solid-state packing structures described. The compounds are [(morph)+(5-nsa)–] 1, [(hmt)+(5-nsa)–·H2O] 2, and [(en)2+2(5-nsa)–·H2O] 3. In all compounds, protonation of the hetero-nitrogen of the Lewis base occurs. With 1, the 5-nsa anions and the morpholine cations lie, respectively, in or across crystallographic mirror planes and are linked within the planes by hydrogen-bonding interactions through the aminium group and the carboxylic and phenolic oxygens of the anionic 5-nsa species giving a two-dimensional sheet polymer. Compound 2 is an unusual structure with the planar 5-nsa anions lying within pseudo mirror planes and cyclically linked by duplex water bridges through a single carboxylate oxygen into centrosymmetric dimers. The hmt cation molecules are disordered across the pseudo mirror and are strongly linked by N+–H···O hydrogen bonds only to the water molecules with peripheral weak hmt C–H···O hydrogen bonds extending the dimer within and between the dimer planes. Compound 3 is a network polymer comprised of the 5-nsa anions, the en dianions, and the water molecule in an extensive hydrogen-bonded structure.

scholarly journals Lewis acid- and/or Lewis base-catalyzed [3+2] cycloaddition reaction: synthesis of pyrazoles and pyrazolines

2008 ◽  
Vol 49 (48) ◽  
pp. 6768-6772 ◽  
Author(s):  
Palakodety Radha Krishna ◽  
Empati Raja Sekhar ◽  
Florence Mongin
Keyword(s):  
Lewis Acid ◽  
Cycloaddition Reaction ◽  
Lewis Base ◽  
Reaction Synthesis

SOLVENT EFFECTS ON THE ELECTRONIC STRUCTURE AND NON-LINEAR OPTICAL PROPERTIES OF PYRENE AND SOME OF ITS DERIVATIVES BASED ON DENSITY FUNCTIONAL THEORY

2021 ◽  
Vol 4 (4) ◽  
pp. 236-251
Author(s):  
A. S. Gidado ◽  
L. S. Taura ◽  
A. Musa
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Gap ◽  
Chemical Reactivity ◽  
Basis Set ◽  
Lumo Energy ◽  
Functional Theory ◽  
Organic Optoelectronic ◽  
Homo Lumo

Pyrene (C16H10) is an organic semiconductor which has wide applications in the field of organic electronics suitable for the development of organic light emitting diodes (OLED) and organic photovoltaic cells (OPV). In this work, Density Functional Theory (DFT) using Becke’s three and Lee Yang Parr (B3LYP) functional with basis set 6-311++G(d, p) implemented in Gaussian 03 package was  used to compute total energy, bond parameters, HOMO-LUMO energy gap, electron affinity, ionization potential, chemical reactivity descriptors, dipole moment, isotropic polarizability (α), anisotropy of polarizability ( Δ∝) total first order hyper-polarizability () and second order hyperpolarizability (). The molecules used are pyrene, 1-chloropyrene and 4-chloropyrene  in gas phase and in five different solvents: benzene, chloroform, acetone, DMSO and water. The results obtained show that solvents and chlorination actually influenced the properties of the molecules. The isolated pyrene in acetone has the largest value of HOMO-LUMO energy gap of and is a bit closer to a previously reported experimental value of  and hence is the most stable. Thus, the pyrene molecule has more kinetic stability and can be described as low reactive molecule. The calculated dipole moments are in the order of 4-chloropyrene (1.7645 D) < 1-chloropyrene (1.9663 D) in gas phase. The anisotropy of polarizability ( for pyrene and its derivatives were found to increase with increasing polarity of the solvents.  In a nutshell, the molecules will be promising for organic optoelectronic devices based on their computed properties as reported by this work.

scholarly journals Recent Synthesis Developments of Organoboron Compounds via Metal-Free Catalytic Borylation of Alkynes and Alkenes

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 101 ◽  
Author(s):  
Yanmei Wen ◽  
Chunmei Deng ◽  
Jianying Xie ◽  
Xinhuang Kang
Keyword(s):  
Lewis Acids ◽  
Heterocyclic Carbenes ◽  
Lewis Base ◽  
Organoboron Compounds ◽  
Lewis Bases ◽  
Metal Free ◽  
Recent Synthesis

Diboron reagents have been traditionally regarded as “Lewis acids”, which can react with simple Lewis base to create a significant nucleophilic character in one of boryl moieties. In particular, bis(pinacolato)diboron (B2pin2) reacts with simple Lewis bases, such as N-heterocyclic carbenes (NHCs), phosphines and alkoxides. This review focuses on the application of trivalent nucleophilic boryl synthon in the selective preparation of organoboron compounds, mainly through metal-free catalytic diboration and the β-boration reactions of alkynes and alkenes.

scholarly journals Molecular Geometry, NLO, MEP, HOMO-LUMO and Mulliken Charges of Substituted Piperidine Phenyl Hydrazines by Using Density Functional Theory

2019 ◽  
Vol 32 (2) ◽  
pp. 401-407
Author(s):  
M. Dinesh Kumar ◽  
P. Rajesh ◽  
R. Priya Dharsini ◽  
M. Ezhil Inban
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Chemical Reactivity ◽  
Molecular Geometry ◽  
Basis Set ◽  
Functional Theory ◽  
B3lyp Method ◽  
Reactivity Descriptor ◽  
Homo Lumo ◽  
Optimized Geometries

The quantum chemical calculations of organic compounds viz. (E)-1-(2,6-bis(4-chlorophenyl)-3-ethylpiperidine-4-ylidene)-2-phenyl-hydrazine (3ECl), (E)-1-(2,6-bis(4-chlorophenyl)-3-methylpiperidine-4-ylidene)-2-phenylhydrazine (3MCl) and (E)-1-(2,6-bis(4-chloro-phenyl)-3,5-dimethylpiperidine-4-ylidene)-2-phenylhydrazine (3,5-DMCl) have been performed by density functional theory (DFT) using B3LYP method with 6-311G (d,p) basis set. The electronic properties such as Frontier orbital and band gap energies have been calculated using DFT. Global reactivity descriptor has been computed to predict chemical stability and reactivity of the molecule. The chemical reactivity sites of compounds were predicted by mapping molecular electrostatic potential (MEP) surface over optimized geometries and comparing these with MEP map generated over crystal structures. The charge distribution of molecules predict by using Mulliken atomic charges. The non-linear optical property was predicted and interpreted the dipole moment (μ), polarizability (α) and hyperpolarizability (β) by using density functional theory.

Dioxouranium(VI) complexes with N-salicylsalicylaldimines and their Lewis base adducts

1975 ◽  
Vol 28 (4) ◽  
pp. 885 ◽  
Author(s):  
ATT Hsieh ◽  
RM Sheahan ◽  
BO West
Keyword(s):  
Schiff Bases ◽  
Metal Atom ◽  
Lewis Base ◽  
Donor Ligands ◽  
Chelate Complexes ◽  
Nitrogen Donor Ligands ◽  
Uranium Metal ◽  
Lewis Bases ◽  
Nitrogen Donor ◽  
Weak Coordination

New dioxouranium(VI) complexes with the dibasic terdentate Schiff bases, XC6H3(2-OH)CH=N-CH2C6H4(2?-OH) (X = H, 5-Cl or 3-MeO), have been synthesized and characterized as their 1 : 1 alcohol adducts. The labile alcohol molecules in these complexes are readily replaced by various oxygen or nitrogen donor ligands, affording six- or seven- coordinate complexes. Evidence is presented for the rather weak coordination of these Lewis bases to the uranium metal atom. The various possible conformations for these [6,6]-membered chelate complexes are also discussed.

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