Density functional calculation of core‐electron binding energies of isomers of C3H6O2 and C3H5NO

The core‐electron binding energies of six isomers of C₃H₆O₂ and four isomers of C₃H₅NO were calculated by a DFT/uGTS/scaled‐pVTZ approach. An average absolute deviation from experiment of 0.15 eV was found for 14 C, N, and O 1s energies. The results confirm the distinctive nature of the X‐ray photoelectron spectra (XPS) of isomers and support the use of electron spectroscopy complemented by accurate theoretical predictions as a tool for chemical analysis. © 1999 John Wiley & Sons, Inc. Int J Quant Chem 76: 44–50, 2000     

Theoretical Studies on the Cu-Cu Interaction and Stability of [Cu_a(Ph_2Ppy)_b(CH_3CN)_c]~(a+) (a=1～2,b=1～3,c=0～2)

To study the Cu-Cu interaction and stability of the title complexes,the structures of complexes [Cu(Ph2Ppy)(CH3CN)]+ 1,[Cu(Ph2Ppy)]+ 2,[Cu2(Ph2Ppy)2(CH3CN)2]2+ 3,[Cu2(Ph2Ppy)2(CH3CN)]2+ 4,[Cu2(Ph2Ppy)2]2+ 5 and [Cu2(Ph2Ppy)3(CH3CN)]2+ 6 were calculated by density functional theory PBE0 method,and the following conclusions can be drawn:(1) There is no orbital overlapping between two Cu atoms,indicating no Cu-Cu orbital interaction exists in complexes 3～6.Due to a breakdown of the closed shell configuration of Cu atoms,the weak Cu-Cu interactions result from the 3dCu → 4sCu' charge-transfer in 4～6.The Cu-Cu interaction strength follows 5 6 4,implying that there are stronger Cu-Cu interactions in the complexes with fewer CH3CN or more Ph2Ppy ligands.(2) The calculated interaction energies suggest that the coordination of Cu to Ph2Ppy is stronger than that to CH3CN.In 3～6,there are weaker interactions between Cu and CH3CN or Ph2Ppy in the complexes with more CH3CN or Ph2Ppy ligands.(3) The P-Cu and N-Cu interactions are much stronger than the Cu-Cu interaction,so we mainly attribute the stabilities of the binuclear complexes to the eight-membered rings Cu2P2N2C2.     

Ir(CO)Cla(Ph2Ppy)2HgClb(HgCl2)c(a,b=1,2;c=0,1)的Ir-Hg相互作用和氧化还原反应性质

应用密度泛函理论(DFT)的PBEO方法,金属原子采用SDD基组,H、C、O和N原子采用6-31G*基组,P和Cl原子采用6-311G*基组,对单核配合物Ir(CO)Cl(Ph2Ppy)2(1),双核配合物Ir(CO)(Cl)2(Ph2Ppy)2HgCl(2)、Ir(CO)Cl(Ph2Ppy)2HgCl2(3)和Ir(CO)(Cl)2(HgCl2)(Ph2Ppy)2HgCl(4)进行结构优化,并在优化的基础上采用基组重叠误差(BSSE)校正计算相互作用能,通过自然键轨道(NBO)和前线轨道分析研究Ir-Hg相互作用和氧化还原反应的实质.通过计算发现,Ir(CO)Cl(Ph2Ppy)2与HgCl2发生氧化还原反应得到的产物2和4比非氧化还原产物3稳定.Ir-Hg相互作用强度顺序为3＜4＜2,且随着Ir-Hg相互作用强度增大,HOMO轨道中Ir和Hg成分逐渐趋于接近.配合物2和4都具有一对Ir-Hg成键与反键轨道,其成键轨道的组成分别为0.5985sd0.06Hg+0.8012sd2.48Ir和0.5794sd0.05Hg+0.8151sd2.48Ir,但3中Ir与Hg的相瓦作用较弱,只存在弱相互作用(电荷转移作用),表现为nIr→nHg的直接作用和σIr-P(1)→nHg、σIr-C(1)→nHg的间接作用.     

配合物[M（CO）3（PPh2py）2]（M=Fe，Ru）异构体的理论研究

对PPh2py配合物[M(CO)3(PPh2py)2](M=Fe,Ru)的三种构型的异构体1-6进行了研究.其中PPh2py以两个P原子与M配位形成HH构型1(Fe)和4(Ru),以一个P和一个N原子与M配位形成HT构型2(Fe)和5(Ru),以两个N原子与M配位形成HH'构型3(Fe)和6(Ru).结果表明,(1)PPh2py中P原子对HOMO轨道的贡献最大,PPh2py作为电子给体时易以P原子与金属原子结合.(2)从分子能量和相互作用能数据表明,配合物中HH构型最稳定,HH'构型最不稳定,这与合成产物为HH构型的结果一致.(3)键长和Wiberg键级均表明P-M键比N-M键结合力强.P、M原子间存在σ键,而N、Fe原子间仅存在nN→nM或nN→σM-P的电荷转移作用.(4)HH构型中M对HOMO的贡献最大,PPh2py向M的电荷转移最强,使M的负电荷最大,故HH构型最易作为电子给体以M原子与第二个金属配位形成双核配合物.     

Theoretical Studies on the M-M Bonding in Complexes [M2Cl4L2] and [M2Cl7L]- （M = Mo, Re; L = Ph2Ppy, （Ph2P）2py）

The structures of complexes [MⅡ2Cl4L2] and [MⅢ2Cl7L]- (M = Mo, Re; L = Ph2Ppy, (Ph2P)2py) were calculated by using density functional theory (DFT) PBE0 method. Based on the optimized geometries, the natural bond orbital (NBO) analyses were carried out to study the nature of Re-Re and Mo-Mo bonds. The conclusions are as follows: the M-M distances in two-Ph2Ppy or (Ph2P)2py complexes [MⅡ2Cl4L2] are shorter than those in mono-Ph2Ppy or (Ph2P)2py complexes [MⅢ2Cl7L]- due to the double bridged N-C-P interactions. For singlet of all complexes, there is ReⅢ-ReⅢ or MoⅡ-MoⅡ quadruply bond in complex [Re2Cl7L]- or [Mo2Cl4L2], while only ReⅡ-ReⅡ or MoⅢ-MoⅢ triply bond in complex [Re2Cl4L2] or [Mo2Cl7L]-. The most stable spin state of 2 and 6, triplet, only contains triple ReⅢ-ReⅢ bond. Because the LPCl → BD*Re-Re delocalizations weaken the Re-Re bond, the distance of ReⅢ-ReⅢ quadruple bonds in [Re2Cl7L]- is slightly longer than that of ReⅡ-ReⅡ triple bonds in [Re2Cl4L2]. Moreover, due to the delocalizations from the lone pair electrons of the remaining P' atom to the M-M antibonding orbitals, the M-M distance in (Ph2P)2py complexes is slightly longer than that in Ph2Ppy complexes.     

Improving the energies of approximate wave functions using the concepts of density functional theory

A simple method, derived from DFT, for improving the energy of a trial density is modified for the case of atoms. It is assumed that errors in the interelectronic repulsion are the only significant ones. The errors in the energies of single‐ζ Slater orbitals for the atoms from He to Ne are reduced an average factor of 21. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Donor acceptor groups effect,polar protic solvents influence on electronic properties and reactivity of 2-Chloropyridine-4-carboxylic acid

The computational reckoning of 2-Chloropyridine-4-carboxylic acid (2CP4CA) was accomplished employing DFT/B3LYP with the root set as 6–311++G(d, p). The impact of polar protic solvents which are eco-friendly solvents (water, methanol, ethanol, 1-propanol) on 2CP4CA were analysed. To examine the solvent effect, vibrational investigations and NLO reports of 2CP4CA in dissimilar solvents were executed. Geometrical properties were also established in gas phase for 2CP4CA. Exercising VEDA program, the entire vibrational assignment was accomplished. Donor-acceptor exchanges were ascertained utilizing NBO scrutiny technique. Thermodynamic properties of 2CP4CA were analysed at different temperatures. By applying TD - DFT approach, theoretic UV–Vis absorption spectrum was procured in different solvents. In order to evaluate the complete electron concentration and sensitive spots of 2CP4CA, MEP coupled with FMO analyses were employed. HOMO along with LUMO orbitals and energy band gap were acquired for 2CP4CA employing dissimilar polar protic solvents. Additionally, ELF, LOL and charge transfer studies were also executed. RDG analysis has been exercised for revealing non-covalent interactions.     

Predicting adsorption behavior of Triacanthine anticancer drug with pure B12N12 nano-cage: A theoretical study

Predicting adsorption behavior of the Triacanthine (TRC) anticancer drug on the surface of B₁₂N₁₂ nano-cage was investigated using DFT and TD-DFT methods by B3LYP/6-311+G(d) level in the water solution. The adsorption energies of the TRC-B₁₂N₁₂ complexes (A-C) were shown that the adsorption process is exothermic. The UV/Vis absorption and IR spectra analysis were calculated to investigate the changes happening in adsorption of TRC over nano-cage. According to the results, the interaction of the TRC drug from the N9 atom on the B₁₂N₁₂ nano-cage (model A) has the most chemical stability rather than models B and C. Based on NBO analysis, the charge transfer process has happened between the TRC drug and B₁₂N₁₂ nano-cage. Recovery time, charge difference (ΔN), and ELF analysis were calculated. It was understood that the B₁₂N₁₂ nano-cage can be a good carrier for the delivery of TRC anticancer medicine.     

The effect of electron charge transfer in biological activity and vibrational wavenumbers of 2′-Deoxyuridine and 5-Fluoro-2′-Deoxyuridine: DFT approach

Vibrational analysis of the 2′-Deoxyuridine and 5-Fluoro-2′-deoxyuridine compounds has been performed using FT-Raman and FTIR spectroscopic techniques. The optimized geometry, various bonding features and harmonic vibrational wavenumbers have been computed with the help of B3LYP/6-31G (d, p) density functional theory method. The natural bond orbital analysis, Mulliken population analysis on atomic charges and the HOMO–LUMO energy have been calculated to explore the reasons for the change in biological activity and vibrational wavenumbers of the title compounds. Potential energy distribution analysis has been used to assign the normal modes of vibrations unambiguously.     

Computation and analysis of 19F substituent chemical shifts of some bridgehead‐substituted polycyclic alkyl fluorides

The ¹⁹F NMR shieldings for several remotely substituted rigid polycyclic alkyl fluorides with common sets of substituents covering a wide range of electronic effects were calculated using the DFT‐GIAO theoretical model. The level of theory, B3LYP/6–311+G(2d,p), was chosen based on trial calculations which gave good agreement with experimental values where known. The optimized geometries were used to obtain various molecular parameters (fluorine natural charges, electron occupancies on fluorine of lone pairs and of the C? F bond, and hybridization states) by means of natural bond orbital (NBO) analysis which could help in understanding electronic transmission mechanisms underlying ¹⁹F substituent chemical shifts (SCS) in these systems. Linear regression analysis was employed to explore the relationship between the calculated ¹⁹F SCS and polar substituent constants and also the NBO derived molecular parameters. The ¹⁹F SCS are best described by an electronegativity parameter. The most pertinent molecular parameters appear to be the occupation number of the NBO p‐type fluorine lone pair and the occupation number of the C? F antibonding orbital. This trend suggests that in these types of rigid saturated systems hyperconjugative interactions play a key role in determining the ¹⁹F SCS. Electrostatic field effects appear to be relatively unimportant. Copyright © 2003 John Wiley & Sons, Ltd.     

Hydrogen bonding interaction and topological insights of the electron localization/delocalization of l- arginine acetate

The vibrational spectral studies of the semi-organic material l- arginine acetate (LAA) are carried out with the help of density functional calculations to derive the equilibrium geometry as well as the vibrational wavenumbers and intensities of the spectral bands. The vibrational spectrum assignments are performed using normal coordinate analysis (NCA) in accordance with the scaled quantum mechanical force field approach (SQMFF). Vibrational spectra confirm the COO- modes split due to intra- and intermolecular association based on C–O….H, N–H….O, and O–H?O hydrogen bonding in the molecule, which lowers carboxylate wavenumbers. The natural bond orbital (NBO) analysis and DFT computations also confirm the occurrence of strong intra and intermolecular N–H?O and O–H?O ionic hydrogen bonding between charged species, providing the non-centrosymmetric structure in the LAA crystal.     

Influence of acceptor tethering on the performance of nonlinear optical properties for pyrene-based materials with A-π-D-π-D architecture

In this study, we designed a series of pyrene-based donor-π-donor-π-acceptor compounds (HPTC1-HPTC7) by structural tailoring the reference compound (HPTC) using acceptor units. Nonlinear optical (NLO) properties, frontier molecular orbitals (FMOs), natural bonding orbital (NBO), transition density matric (TDM) analysis, and absorption spectra of reference and proposed derivatives were calculated at M06/6-31G(d,p) functional. All the designed compounds have smaller energy bandgaps than the HPTC compound. Moreover, the designed compounds exhibited larger global softness values than the reference. The absorption maxima of HPTC2, HPTC3, and HPTC7 are blue shifted with respect to HPTC. NBO analysis revealed that prolonged hyper conjugative associations and strong interactions between the donor (π) and acceptor (π*) moieties play a crucial part in their stabilization. The FMO and NBO findings supported the NLO responses of entitled compounds, and consequently, the linear and nonlinear properties of designed derivatives elevate compared to the reference molecule. Promisingly, the NLO response for HPTC7 comprises of highest values of <α>, β_total and < γ > as 1.92 × 10^?22 esu, 1.95 × 10^?27 esu, and 4.69 × 10⁷ (a.u). This NLO behavior shows push–pull NLO chromophores for HPTC7 predicting its role in pursuing NLO materials for optoelectronic applications.