NBO Charges Research Articles

Donor→acceptor coordination interactions in 1,3-bis(NHC)triazenyl Cations: An electronic structure analysis.

Donor→acceptor coordination interactions (L → N) between ligands and nitrogen center as in L → N⊕ ← L were reported in the recent past. This article describes the possibility of L → N coordination interactions in triazenyl cation species L → N3 ⊕ ← L. A few 1,3-bis(NHC)triazenyl cation species were experimentally known, the electronic structure analysis reported in this work reveals the presence of L → N (donor→acceptor) interactions in these species. Molecular orbital analysis, NBO charge analysis, energy decomposition analysis, and so forth, confirm the possibility of L → N coordination bond character. Ten molecules with the general formula L → N3 ⊕ ← L have been designed carrying L → N3 ⊕ ← L interactions. © 2019 Wiley Periodicals, Inc.

New NHC cycloplatinated compounds. Significance of the cyclometalated group on the electronic and emitting properties of bis-cyanide compounds

Compounds NBu4[Pt(CˆC*A/B/C)(CN)2] (HCˆC*A = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene 1, HCˆC*B = 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene 2, HCˆC*C = 1-(3,5-dichlorophenyl)-3-methyl-1H-imidazol-2-ylidene 3) and NBu4 [Pt(CˆC*A/B/C)(13CN)2] (1′-3′) were synthesized by addition of KCN (or K13CN) to freshly prepared species [Pt(CˆC*A/B/C)(NCCH3)2]ClO4, in a 2:1 M ratio. Single crystal X-ray structures of 1–3 showed the absence of intermolecular π-π and Pt-Pt interactions. The 195Pt{1H} NMR data of 1–3 were obtained and compared with those of the related compounds NBu4[Pt(CˆN)(CN)2] (CˆN = benzoquinolate, bzq; phenylpyridinate, ppy). They indicate that the electronic density on the Pt center is larger for NBu4[Pt(CˆC*A/B/C)(CN)2](1–3) than for NBu4[Pt(CˆN)(CN)2], which has been proved through NBO charge distribution analysis. Compounds 1 and 2 resulted to be rather good blue-emitters with their emissions arising mainly from 3IL [π(NHC) → π*(NHC)] excited states with little 3MLCT [5d(Pt) → π*(NHC)] character. The emission of 2 in PMMA film render PLQY (Ф) of 70% and Commission Internationale de L'Eclairage (CIE) coordinates (0.15, 0.19) highly close to the optimal ones for blue emitters (0.15, 0.15).

Theoretical study on kinetics of ammonia-catalyzed ground-state tautomerization in 2-pyridone: effect of chemical modification

The effects of chemical modification on the kinetics of GSPT in 6R2PY-NH3 (R=NO2, CF3, COOH; CH3, C2H5) complex, in which the H atom at C6 position of 2PY was substituted, were researched in detail at the M06-2X/6-311 + G(d, p) level. The changes of structural parameter, reaction mechanism, and energies of GSPT before and after the replacement with different substituent have been analyzed. GSPT process in the 6R2PY-NH3 (R=NO2, CF3, COOH; CH3, C2H5) complex preferred to occur via a concerted but asynchronous protolysis pathway regardless of the electronic nature of substituent R. However, the structural parameters, asynchronicity of GSPT, and barrier height were influenced by the different substituent. The Hammett’s and Taft’s substituent constant had linear correlation with ∆(R1 + R2), NBO charges of NH4+ and ∆∆V.

Electronic Structure, Spectroscopic (IR, Raman, UV-Vis, NMR), Optoelectronic, and NLO Properties Investigations of Rubescin E (C31H36O7) Molecule in Gas Phase and Chloroform Solution Using Ab Initio and DFT Methods

Quantum chemical methods were used to study the electronic structure and some physicochemical properties of Rubescin E molecule. Good agreement with experiment was found for J3H-H coupling constant, IR, 1H NMR, and 13C NMR. The excitation energy and oscillator strength calculated by TD-DFT also complement with experiment. Large values were obtained for dipole moment, polarizability, first static hyperpolarizability, electric susceptibility, refractive index, and dielectric constant, meaning that Rubescin E has strong optical and phonon application and can be a good candidate as NLOs material. The 3D analysis of the title molecule leads us to the conclusion that electron can easily be transferred from furan to tetrahydrofuran ring. The global reactivity descriptors were evaluated. Mulliken, ESP, and NBO charges comparisons were carried out and described.

Theoretical Study of the Effect of Simultaneous Doping with Silicon, on Structure and Electronic Properties of Adamantane

In this paper, structural and electronic properties of adamantane (C10H16) and its Si-doped derivatives were calculated using density functional theory. In order to find diamondoids with specific properties, one to ten carbon atoms of adamantane were substituted with silicon atoms and the changes in structural and electronic properties of adamantane after substituting were investigated. HOMO-LUMO energies of 1–10 Si-doped adamantane and their gaps were calculated and the parameters that affect on the energy gaps of Si-doped structures were introduced. Among the doped molecules, 4-Si doped adamantane with high symmetry structure shows distinct properties. Adiabatic electron affinity and ionization potentials were calculated using Gibbs free energies of cationic and anionic forms of all structures. The results show that the electron affinity of adamantane is negative and reduces to positive values by simultaneous C/Si doping in 7–10-sila-doped adamantane. These results show the vacuum level transfer from above to below the conduction band. NBO charge analyses were also applied for describing the electron affinity and Ionization potential results.

A theoretical study on the mechanism and kinetics of toxic PCDD destruction by OH radicals

The mechanism and kinetics of toxic PCDDs destruction by OH radicals is investigated in detail by employing quantum chemistry. Results show that the OH radical degrades toxic PCDDs via substituting chlorine at the 2, 3, 7, 8 positions. The kinetic parameters are calculated by adopting transition state theory. The rate constant of OCDD destruction by OH is in agreement with the experimental result, especially at 298 K. The rate constants of 2, 3, 7, 8-TCDD destruction are obviously lower than those of other toxic PCDDs. The reason is discussed by using the NBO charge analysis. Owing to the activation effect of Cl atoms at 1, 4, 6, 9 positions, C atoms at 2, 3, 7, 8 positions have more negative charge. At aromatic rings, if the carbon has more negative charge, the carbon is more easily attacked by OH and the adjacent Cl is more easily substituted.

XRD, FT-IR, FT-Raman spectra and ab initio HF vibrational analysis of bis (5-amino-3-carboxy-1H-1,2,4-triazol-4-ium) selenate dihydrate

The selenic hydrogen bonded salt Bis(5-amino-3-carboxy-1H-1,2,4-triazol-4-ium) selenate dihydrate (BACTSe) has been synthesized and characterized by XRD, FT-IR and FT-Raman techniques. It crystallizes in the C2/c space group and displays a three-dimensional framework stabilized mainly via intermolecular OH⋯O, NH ⋯O and OH⋯N hydrogen bonds. The quantum chemical study performed with ab initio UHF method using 6-311G(d,p) base set, has permitted the determination of the structural parameters, the total energy, the HOMO and LUMO energies, the thermodynamic parameters and the NBO charges. Moreover, normal mode frequencies and corresponding vibrational assignments have been examined.

Computational study of halogen-free Boron based dicationic ionic liquids of [bis-Mim][BMB]2 and [bis-Mim][BScB]2.

In this paper, the structures and energetics of 1,3-bis[3-methylimidazolium-yl] pentane ([bis-Mim]2+) dication and bis(mandelato) borate [BMB]- and bis(salicylato) borate [BScB]-anions in isolated forms, ion pairs (IPs) and dicationic ionic liquids (DILs) were studied by Density Functional Theory (DFT) at the M06-2X/6-31G(d,p) level of theory. According to the IUPAC criteria, the hydrogen bonds between anion and cation were characterized and classified in the optimized geometries of the isolated ions, IPs and DILs. Inspection of the optimized structures revealed that the interionic hydrogen binding has important effect on the ions structures. The interaction energies between a dication and anions have been described in terms of NBO charge distribution, the stabilization energy E(2) values, changes of vibrational frequencies and the reduced density gradient (RDG) analysis. Also, the reactivity and interactions between chemical species were interpreted in terms of global electronic properties. Electrostatic potential surfaces (ESP) have been applied for visualizing the charge related properties and characterization of the most energetic sites of isolated ions and ion complexes.

A computational study on molecular structure and stability of tautomers of dipyrrole-based phenanthroline analogue

This work reports structure and stability of different tautomers of a newly-designed analogue of 1,10-phenanthroline-5,6-dione (the di-keto structure (DK) derived from 1H,8H-pyrrolo[3,2-g]indole (PI)) using quantum chemical computations. Molecular structures and relative stabilities of four tautomers and their relevant rotamers of the investigated system have been studied using the B3LYP and M06 methods combined with the 6–31 + G(d,p) basis set, as well as the CBS-QB3 method. The effect of solvent has also been modelled in water using the PCM method at the M06/6-31+G(d,p) level of theory. Moreover, the aromaticity of the seven structures have been discussed based on their geometrical properties as well as the NICS indices. The results emphasize the predominance of the di-keto isomer (DK) and its greater stability over the keto-enol and di-enol conformers according to structural, energetic and magnetic criteria. In addition, NBO charges, HOMO-LUMO and ESP of the most stable tautomer DK have been employed to predict the electron donation active side toward metal ions.

Applying the B12N12 nanoparticle as the CO, CO2, H2O and NH3 sensor

In this study, the various properties including the stability energies, structural and electronic aspects of the hydrazine (N2H4), carbon monoxide (CO) water (H2O) and ammonia (NH3) molecules adsorptions on the top of the boron nitride nanoparticles (BNn) were studied through the Minnesota Functionals computations, DFT/M06-2X. The calculations clarifies that the most stable adsorption configurations are those in which the oxygen, carbon, oxygen and nitrogen atoms of CO2, CO, H2O and NH3 are closed to the boron atom of the nanoparticle, respectively. The absorption energies were obtained about -0.14, -0.15, -0.87 and -1.54 eV for abosorption of CO2, CO, H2O and NH3 gasses. The geometry optimizations, energy calculations and NBO charge transfer were used to evaluate the sensing ability of BNn for different analytes. The computed density of states (DOS) clarifies that a strong orbital hybridization take place between CO2, CO, H2O and NH3 and BNn in adsorption process. Finally, it is concluded that the BNn nanoparticle has greater response selectivity toward NH3 compared to CO, CO2 and H2O

Experimental and Theoretical Study on New Zn(II) Halide Complexes of 3,5-Diazaindole

3,5-Diazaindole — zinc(II) halide complexes (halogen: Cl, Br, I) are synthesized for the first time. Experimental mid-IR spectra of the compounds were recorded in the range 4000–550 cm–1, and far-IR spectrum of the zinc(II) chloride complex is recorded in range 700–40 cm–1. The structural features of the zinc(II) halide complexes of 3,5-diazaindole (ICPY) are studied by quantum chemical methods. The optimized geometry and vibrational frequencies of the ICPY — zinc(II) halide complexes are calculated using the B3LYP/DFT method with the LANL2DZ basis set in the ground state. Vibrational assignments of the most important bands are made with the help of the vibrational energy distribution analysis. The frontier molecular orbital energies, NBO charges, and dipole moments are presented. 1H and 13C NMR spectra of the zinc(II) chloride complex is also given.

Insight into electronic and structural properties of nLi@ $$\text {B}_{20}$$ B 20 ( $$\hbox {n}=1{-}9$$ n = 1 - 9 ) nanotubules: a computational study

In this paper, we have theoretically focused on the doping of up to nine Li atoms to the double-ring $$\text {B}_{20}$$ nanotubule to reveal the electronic and structural features of the nLi@ $$\text {B}_{20}$$ ( $$\text {n}=1{-}9$$ ) molecules. The most stable species for each of the nLi@ $$\text {B}_{20}$$ ( $$\text {n}=1{-}9$$ ) molecules has been reported on the singlet or doublet potential energy surfaces through density functional theory (DFT). The calculated results show that the nLi@ $$\text {B}_{20}$$ ( $$\text {n}=1{-}9$$ ) molecules have high thermodynamic and chemical stabilities due to high values of the adsorption energy, −2.51 eV to −3.57 eV, and the HOMO–LUMO energy gap, 1.32 eV to 2.34 eV. Additionally, the values reported for deformation of the double-ring $$\text {B}_{20}$$ backbone, 0.10 eV to 4.29 eV, increase severely along with increasing number of the Li atoms in the nLi@ $$\text {B}_{20}$$ ( $$\text {n}=1{-}9$$ ) molecules. The NBO charges of positive values for the Li atoms along with those of negative values for the B atoms confirm the role of electron donor of the Li atom and electron acceptor of the B atom. Finally, we have not found any Li–Li interaction in the nLi@ $$\text {B}_{20}$$ ( $$\text {n}=1{-}9$$ ) molecules based on AIM analysis. Moreover, all reported Li–B interactions are weak and non-covalent. In the present study, we have systematically added up to nine Li atoms to the double-ring $$\text {B}_{20}$$ molecule to report electronic and structural properties of the most stable local minima for each nLi@ $$\text {B}_{20}$$ ( $$\hbox {n}=1{-}9$$ ) molecules on the singlet or doublet potential energy surfaces.

Büchi's model based analysis of local anesthetic action in procaine hydrochloride: Vibrational spectroscopic approach

The drug action of ester type local anesthetic (LA) procaine hydrochloride (PRC HCl) is activated by blocking Na+ ion flow when it binds to the ion channel in the ligand gated sodium ion channel protein. Büchi's model, explains binding action of ester type LA drug with receptor in terms of charge transfer, dipole-dipole, hydrogen bonding and van der Waals interactions through lipophilic, ester and hydrophilic moieties. The present work investigates molecular structural and vibrational spectral features of para amino benzoate group, ester part and tertiary amino group respectively belonging to lipophilic, ester and hydrophilic moieties, accountable for the binding of drug to sodium channel. The electron transport mechanism through the ring responsible for structural deviation from benzenoid to quinonoid form and consequent dipolar nature of carbonyl group have been investigated, based on the analysis of XRD, DFT computed molecular structure, 8a ring mode and NBO charges. The characteristic UV absorption peaks and vibrational marker bands of LA drugs have been identified and the charge transfer interaction responsible for lipophilic binding has been investigated. The blocking of Na+ in the ion channel has been probed using attractive and repulsive energy profile. The molecular polarizability has been computed to substantiate the correlation between the structure activity relationship of LA drug molecule and molecular polarizability. The low toxicity of PRC HCl was evaluated using in vitro cytotoxicity study, confirming it as a potential short acting local anesthetic.

Theoretical and experimental studies on optically tunable hydrogen bonded liquid crystal complex derived from mesogenic and non-mesogenic aromatic compound

A novel hydrogen bonded liquid crystal (HBLC) complex is synthesized from non-mesogenic benzylmalonic acid (BMA) and mesogenic 4-nonyloxybenzoic acid (9OBA). Structural properties and optimized vibrational frequencies of BMA + 9OBA have been studied by FT-IR spectrum. The weak intermolecular interaction between the molecules is proved by NBO and Mulliken charge distribution analysis. The optical and thermal properties are investigated by POM, DSC, UV-Visible and PL techniques. The present HBLC complex exhibits schlieren textures of nematic, broken focal conic texture of smectic C and multicolored mosaic texture of smectic G phases respectively which is not observed in the pure mesogen (9OBA). The HBLC complex geometry is optimized by DFT method at the level of B3LYP basis set 6311G (d, p). The electronic properties of HBLC complex such as, NBO, HOMO-LUMO, ESP and Mulliken charge distribution are also studied. A noteworthy observation is brought out by identifying the presence of photoluminescence in nematic phase due to the variation in intermolecular interaction of the mesophase. The utility of the same complex is discussed. The phase width, thermal stability factor, tilt angle, phase transition temperature and its enthalpy values are reported.

Structure-property relationships of coronene in external electric field

Abstract Coronene as the smallest molecular approximation of polycyclic aromatic hydrocarbon (PAH) has large π-conjugated orbital. In the present work, under the action the external electric fields (Eext, perpendicular to molecular plane), the geometric structure of Coronene from plane to “bowl” and “curly”. Interestingly, there is a redistribution of orbitals in Eext would give rise to significant effect on the NBO charge, which the main negative charge is gradually concentrated in the center-six-membered with the increasing Eext. The distinct charge transfer phenomenon brought about a remarkable nonlinear optical (NLO) property and changed the location of the main aromaticity. Surprisingly, the irregular phenomena of these properties would be happened in same Eext range: 5.00 × 10−2 to 6.00 × 10−2 au, which is respond to the structural change. We hope present work can provide a new strategy to design the high-performance electro-optical materials for large π-conjugated centrosymmetric system.

The ion pair mechanism in the thermal deamination of primary amines catalyzed by HBr in the gas phase: DFT and AIM analysis

The possible reaction mechanisms for the gas-phase thermal deamination of isopropylamine, tert-butylamine, and dextroamphetamine in the presence of hydrogen bromide are investigated by DFT calculations with several functionals. In each case, QTAIM analysis supports the formation of an ion-pair complex, which subsequently decays through a six-membered cyclic transition state (TS). NBO charges and interatomic lengths suggest the polarization of the N1δ−···δ+C2 bond in the TS is rate determining.

Organolithium complex as a gas sensing material for oxides from ab initio calculations and molecular dynamics simulations

AbstractGas sensing study of C2H4Li complex toward oxides viz. CO, CO2, NO, NO2, SO, and SO2 gas molecules has been carried out using ab initio method. Different possible configurations of gas molecule adsorption on C2H4Li complex are considered. The structural parameters of most stable configuration of gas molecule adsorbed complexes are thoroughly analysed. Electronic properties are studied using total density of states (DOS) plot. Charge transferred between the gas molecule and the substrate is studied using NBO charge analysis. Gas sensing of all the six gas molecules is possible at ambient conditions. Atom centred density matrix propagation (ADMP) molecular dynamics simulations confirmed that all the gas molecules remain adsorbed on C2H4Li complex at room temperature during the simulation. This study suggests that the C2H4Li complex acts as a novel gas sensing material for CO, CO2, NO, NO2, SO, and SO2 gas molecules at ambient conditions, below room temperature as well as at high pressure.

Redox-switchable structures and NLO property: Li2 doped into the cavity of pyridine helix

Abstract Helical structure was ubiquitous in the nature and many chemists were attracted to synthesize various helicates, to obtain more fantastic functional materials. In this work, we designed pyridine helical ligand with Li2 doped and explored the effects of redox process on its NLO property. All results stressed the control of redox switch on Li2-doped helical complex. In the aspect of geometric structural traits, obtaining or losing electrons made the helix shrank or extended like a coil spring. In the aspect of NLO property, the sharp fluctuation of βtot values with the range of 1.88 × 102 to 7.73 × 106 au indicated that redox process was an effective switch to control the on-off NLO response. According to the two-level formula, the variation of Δμ qualitatively explained the change of βtot. In terms of bonding traits, NBO and AIM analyses showed in the redox process, NBO charge transferred along reversed direction for oxidation and reduction process. The results of E2 and WBIs obtained by population analysis and the properties at Li N BCPs via AIM analysis, including ρ(r), ∇ 2 ρ(r) and H(r) suggested that in the process of obtaining electrons, Li1 N1 bond became weaker while Li1 N3 bond became stronger. All of the results suggested that obtaining or losing electrons was an effective switch to tune the peculiarities of the complex.

DFT study of structures and hydrogen bonds of imidazolium based halogen-free boron containing dicationic ionic liquids

Halogen containing IL based lubricants are sensitive to the moistures and produce acidic corrosive products. So, there is a growing need towards the development and study of the halogen-free boron based ILs (hf-BILs).In this research, we used the Density Functional Theory (DFT) at the M06-2X/6-31G(d,p)level to study the interactions between 1,3-bis[3-methylimidazolium-yl] pentane dication ([C5(mim)2]2+) and bis(oxalato) borate [BOB]− and bis(malonato) borate [BMLB]− anions (halogen-free Boron based anions). The structures changes in the ion complexes have discussed. The interactions of a dication and anions in the ion pairs (IPs) and ion triplets (ITs) have characterized in terms of changes of vibrational frequencies, NBO charge distribution, reduced density gradient (RDG) analysis, and the stabilization energy E(2) values. The interaction energies, thermodynamic parameters and electronic properties of the isolated ions and their complexes were calculated. Electrostatic potential surface (ESP) studies have also been employed to understand the active sites of isolated ions, IPs and ITs. The results demonstrated that intermolecular hydrogen bonding and electrostatic interactions have a significant role in the stabilizing of the ion pairs and dicationic ionic liquids (DILs). The favorable sites for the cation–anion systems have been determined. The results of this research can shed light on the nature of bonding and interactions between ions to help the design of the new task-specific DILs with a lower impact on the environment.

Experimental and theoretical investigations on magneto-structural correlation in trinuclear copper(II) hydroxido propellers

The trinuclear copper(II) compounds [Cu3(μ3-OH)(GL1)3](ClO4)2 (1–4) and [Cu3(μ3-OH)(GL2)3](ClO4)2 (5–8) with tridentate NNO Schiff base ligands GL1− and GL2− derived from 5-G-substituted salicylaldehydes (G = NO2, Br, H, Me) and the diamines 1,2-ethanediamine and 1,3-propanediamine, respectively, were investigated aiming at shedding light on possible magneto-structural correlation in this class of complexes. All derivatives contain [Cu3(μ3-OH)(L)3]2+ cations with partial cubane Cu3O4 cores, and the metal ions are linked together in a pyramidal fashion by a triple-bridging hydroxido group, giving rise to propellers with three [Cu(L)]+ blades. In these spin-frustrated magnetic systems, the three copper(II) ions within a cluster communicate anti-ferromagnetically (−2JŜi·Ŝj convention) through the bridging OH group with coupling constants J ranging from −4.5(1) for 4 (G = Me) to −10.1(1) cm−1 for 1 (G = NO2), and stabilization of the doublet S = 1/2 ground state. The structural features of the complexes reveal very minimal deviations upon variation of G or the diamine flexibility along the whole series of compounds, preserving almost constant magnetic cores. Similar conclusions are also drawn by DFT gas-phase geometry optimizations of the [Cu3(μ3-OH)(L)3]2+ cations. Therefore, confident of excluding structural influences on the magnetic super-exchange path, the modulating factor of J in our derivatives can be sought after the different electronic demand of G. Atomic NBO charges support this point, revealing small but systematic variations in the electron density flow along the blades and the positive charge on copper(II) ions with the electronic nature of G, with the most remarkable effect given by the nitro group. Topological analysis of electron density according to the Quantum Theory of Atoms In Molecules further support the distinguishing role of this group with respect to the other substituents taken into consideration, besides providing indirect information about the super-exchange path.