Density functional theory and time‐dependent density functional theory study on a series of iridium complexes with tetraphenylimidodiphosphinate ligand

A series of heteroleptic cyclometalated Ir(III) complexes for organic light‐emitting diodes (OLEDs) application have been investigated theoretically to explore their electronic structures and spectroscopic properties. The geometries, the electronic structures, the lowest‐lying singlet absorptions and triplet emissions of Ir(dfppy)₂(tpip), Ir(tfmppy)₂(tpip), and theoretically designed models of Ir(ppy)₂(tpip) were investigated with the density functional theory (DFT)‐based approaches, where ppy = 2‐phenylpyridine, dfppy = 4,6‐difluorophenylpyridine, tfmppy = 4‐trifluoromethylphenylpyridine, and tpip = tetraphenylimidodiphosphinate. Their structures in the ground and their excited states have been optimized at the DFT/Becke 3‐parameter Lee Yang Parr (B3LYP)/Los Alamos National Laboratory 2‐double‐z (LANL2DZ) and time‐dependent DFT/B3LYP/LANL2DZ levels, and the lowest absorptions and emissions were evaluated at B3LYP and M062X level of theory, respectively. Furthermore, the energy transfer mechanism together with the advantage of low efficiency roll‐off for these complexes also can be analyzed here. Copyright © 2013 John Wiley & Sons, Ltd.     

Modeling excitation properties of iridium complexes

Five iridium Ir(III) complexes have been studied using B3P86, B3LYP, M05, M06, M05‐2X, and M06‐2X functionals within configuration interaction singles (CIS) and time dependent density functional theory (TDDFT) formalisms with the aim of finding theory level that would allow for reliable prediction of emission properties. Knowledge of these properties prior to synthesis may significantly facilitate rational design of organic light‐emitting diodes (OLEDs). Our results indicate that the M05‐2X functional gives excellent results in this respect for the class of complexes studied here with the exception of the (bsn)₂Ir(acac) complex. We have shown that the discrepancy between the theoretical and experimental values for this complex is due to the presence of the sulfur atom. Copyright © 2009 John Wiley & Sons, Ltd.     

DFT/TDDFT study on the electronic structures and optoelectronic properties of a series of iridium(III) complexes based on quinoline derivatives in OLEDs

The electronic structures and photophysical properties of several heteroleptic iridium(III) complexes Ir(C^∧N)₂(acac) with acetylacetonate (acac) ligand, including 1 [C^∧N = 2‐phenylisoquinoline], 2 [C^∧N = 2‐biphenyl‐4‐yl‐quinoline], 3 [C^∧N = 2‐(fluoren‐2‐yl)‐quinoline], 4 [C^∧N = 2‐dibenzofuran‐3‐yl‐quinoline], 5 [C^∧N = 2‐dibenzothiophen‐3‐yl‐quinoline], and 6 [C^∧N = 2‐phenanthren‐2‐yl‐quinoline], have been investigated by density functional theory (DFT) and time‐dependent DFT. They show a wide color tuning of photoluminescence from orange–red (λ = 601 nm) to saturated red (λ = 685 nm). The calculated absorption and emission properties of complexes 1 and 2 are in good agreement with the available experimental data. Complex 6 has the smallest ionization potentials (IP) value, which is consistent with its highest occupied molecular orbital energy level, and thus its hole injection is easiest. Corresponding to its lowest unoccupied molecular orbital energy level, the assumed complex 5 has the large electron affinities value and enhanced electron injection ability compared to the others. These calculated results show that the assumed complex 3 may possess better charge transfer abilities than others and is the potential candidate for an efficient electrophosphorescent polymer‐based red‐emitting material. Copyright © 2013 John Wiley & Sons, Ltd.     

甲基和羟基在Ir(111)表面吸附的密度泛函理论研究

在超原胞近似和slab模型基础上,采用周期性密度泛函理论,在0.11覆盖度（ML）下,对甲基与羟基在Ir(111)表面的吸附进行了研究,得到了甲基和羟基在Ir(111)表面不同吸附位置的吸附能和吸附构型,计算了它们的振动频率,同时分析了甲基和羟基共吸附于Ir(111)表面的情况。结果表明,甲基和羟基在Ir(111)表面的最稳定吸附位置都是top位,甲基是碳端向下吸附,羟基是通过氧端向下倾斜吸附。通过频率分析发现吸附后CH3中C-H键的对称伸缩振动、反对称伸缩振动以及剪切振动频率均发生了红移,而羟基中的O-H键的振动频率发生蓝移现象。通过计算对比发现甲醇分解为甲基和羟基过程是一个放热反应,从热力学角度来说该反应是可行的。     

甲基和羟基在Ir(111)表面吸附的密度泛函理论研究

在超原胞近似和slab模型基础上,采用周期性密度泛函理论,在0.11覆盖度(ML)下,对甲基与羟基在Ir(111)表面的吸附进行了研究,得到了甲基和羟基在Ir(111)表面不同吸附位置的吸附能和吸附构型,计算了它们的振动频率,同时分析了甲基和羟基共吸附于Ir(111)表面的情况.结果表明,甲基和羟基在Ir(111)表面的最稳定吸附位置都是top位,甲基是碳端向下吸附,羟基是通过氧端向下倾斜吸附.通过频率分析发现吸附后CH3中C-H键的对称伸缩振动、反对称伸缩振动以及剪切振动频率均发生了红移,而羟基中的O-H键的振动频率发生蓝移现象.通过计算对比发现甲醇分解为甲基和羟基过程是一个放热反应,从热力学角度来说该反应是可行的.     

A theoretical investigation on the electronic structures and phosphorescent properties of three heteroleptic iridium(III) complexes with different substituted ancillary groups

Three heteroleptic iridium(III) complexes 1, 2 and 3 bearing two cyclometalating 2′,6′-difluoro-2,3′-bipyridyl (dfpypy) chelates and one pyridyl pyrazolate ligand have been investigated by using the density functional theory/time-dependent density functional theory method to study the influence of the different substituent groups (―CF₃ and ―N(CH₃)₂ moiety on the electronic structures, phosphorescent properties and the organic light-emitting diode performance. The lowest energy absorption wavelength calculated is in good agreement with the experimental value. The lowest energy emissions of complexes 1, 2 and 3 are localised at 454, 534 and 821 nm, respectively. Ionisation potential and electron affinity have been calculated to evaluate the injection abilities of holes and electrons into these complexes. The calculated results show that the different substitute groups affect the charge transfer rate and balance. Finally, we hope that this study can provide a good guide to the future design and synthesis of novel phosphorescent materials for use in the organic light-emitting diodes.     

Density functional theory study on the structural properties and energetics of microclusters

Density functional theory calculations with B3LYP exchange-correlation functional using CEP-121G basis set have been carried out in order to elucidate the structural properties and energetics of neutral zinc telluride clusters, Zn_mTe_n (m+n6), in their ground states. The geometric structures, binding energies, vibrational frequencies and infrared intensities, Mulliken charges on atoms, HOMO and LUMO energies, the most possible dissociation channels and their corresponding energies for the clusters have been considered.     

The polarisability of atoms and molecules: a comparison between a conceptual density functional theory approach and time-dependent density functional theory

We investigate the local polarisability or polarisability density using both a conceptual density functional theory approach based on the linear response function and time-dependent density functional theory. Using a zero frequency in the latter, we can immediately compare both approaches. Using an analytical expression for the linear response kernel, we are able to systematically analyse α(r) throughout the periodic table. An extension to molecules is also made with a study of the CO molecule retrieving the connection between local softness and local polarisability.     

Computational studies of CO and CO: Density functional theory and time-dependent density functional theory

Potential energy curves, equilibrium interatomic distances, term energies and harmonic vibration frequencies for the 16 lowest states of neutral carbon monoxide and the six lowest states of singly ionized carbon monoxide are calculated by density functional theory (DFT) and linear-response time-dependent density functional (LR-TDDFT) theory. The results are compared with experimental data. The two theories, DFT and LR-TDDFT, are described briefly.     

Density functional theory study on a fluorescent chemosensor device of aza‐crown ether

Three derivatives of alkyl anthracene covalently bonded to aza‐18‐crown‐6 at the nitrogen position, anthracene(CH₂)_n, (n = 1–3) which act as an on–off fluorogenic photoswitch have been theoretically studied using a computational strategy based on density functional theory at B3LYP/6‐31 + G(d,p) method. The fully optimized geometries have been performed with real frequencies which indicate the minima states. The binding energies, enthalpies and Gibbs free energies have been calculated for aza‐18‐crown‐6 ( L ) and their metal complexes. The natural bond orbital analysis is used to explore the interaction of host–guest molecules. The absorption spectra differences between L and their metal ligands, the excitation energies and absorption wavelength for their excited states have been studied by time‐dependent density functional theory with the basis set 6‐31 + G(d,p). These fluorescent sensors and switchers based on photoinduced electron transfer mechanism have been investigated. The PET process from aza‐crown ether to fluorophore can be suppressed or completely blocked by the entry of alkali metal cations into the aza‐crown ether‐based receptor. Such a suppression of the PET process means that fluorescence intensity is enhanced. The binding selectivity studies of the aza‐crown ether part of L indicate that the presence of the alkali metal cations Li⁺, Na⁺ and K⁺ play an important role in determining the internal charge transfer and the fluorescence properties of the complexes. In addition, the solvent effect has been investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Ge(SiO2)n团簇结构和电子性质的密度泛函理论研究

采用密度泛函理论中的广义梯度近似(GGA)对Ge(SiO2)n (n = 1—7)团簇的几何构型进行优化,并对能量、频率和电子性质进行了计算。 结果表明,Ge(SiO2)n的最低能量结构是在(SiO2)n端位O原子以及近邻端位O原子的Si原子上吸附一个Ge原子优化得到;随着锗原子数的增加,增加的锗原子易与原来的锗原子形成锗团簇。掺杂锗原子后团簇的能隙比(SiO2)n团簇的能隙小,当多个Ge原子掺杂到(SiO2)3团簇时,其能隙随着Ge原子个数的增加出现了振荡,Gem(SiO2)3的能隙从可见光区到近红外光区变化。二阶能量差分、分裂能表明Ge(SiO2)2和Ge(SiO2)5团簇是稳定的。     

HCOOH在Pd-Fe(111)(nPd:nFe=1:1)表面吸附的密度泛函理论研究

采用密度泛函理论与周期性平板模型相结合的方法,对HCOOH在Pd(111)表面top, fcc, hcp, bridge 四个吸附位和Pd-Fe(111)表面Pd-top, Fe-top, PdPd-bridge, PdFe-bridge, FeFe-bridge, Pd2Fe-hcp, PdFe2-hcp, Pd2Fe –fcc, PdFe2-fcc等9个吸附位的13种吸附模型进行了能量计算、构型优化,得到了HCOOH较有利的吸附位;并对清洁表面进行能带分析。结果表明：掺杂Fe后,Pd催化剂对HCOOH催化活性增强;HCOOH在Pd(111)表面的最稳定吸附位fcc的吸附能是-41.8kJ•mol-1,在Pd-Fe(111)表面的最稳定吸附位Pd2Fe-hcp的吸附能是-126.5 kJ•mol-1,而且HCOOH在金属表面属于化学吸附。     

HCOOH在Pd-Fe(111)(nPd∶nFe=1∶1)表面吸附的密度泛函理论研究简

采用密度泛函理论与周期性平板模型相结合的方法,对HCOOH在Pd(111)表面top,fcc,hcp,bridge四个吸附位和Pd-Fe(111)表面Pd-top,Fe-top,PdPd-bridge,PdFe-bridge,FeFe-bridge,Pd2Fehcp,PdFe2-hcp,Pd2Fe-fcc,PdFe2-fcc等9个吸附位的13种吸附模型进行了能量计算、构型优化,得到了HCOOH较有利的吸附位;并对清洁表面进行能带分析.结果表明:掺杂Fe后,Pd催化剂对HCOOH催化活性增强;HCOOH在Pd(111)表面的最稳定吸附位fcc的吸附能是-41.8kJ·mol-1,在Pd-Fe(111)表面的最稳定吸附位Pd2Fe-hcp的吸附能是-126.5kJ·mol-1,而且HCOOH在金属表面属于化学吸附.     

Density functional theory study on the magnetic properties of Co3O4 with normal spinel structure

The magnetic properties of Co₃O₄ with a normal spinel structure were investigated via the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The exchange and correlation effects between electrons were treated with a standard generalized gradient approximation (GGA) from Perdew–Burke–Ernzerhof (PBE), as a function of the on-site Coulomb U term, the GGA−PBE+U method, and a B3PW91 hybrid functional with different Hartree–Fock exchange admixtures. Were calculated all of these exchange–correlation (XC) functionals both with and without spin–orbit coupling (SOC). The objective for these calculations was to predict the ground-state magnetic structure of Co₃O₄ crystal using different XC functionals and to investigate the influence that SOC had on these results. All of our calculations confirmed that the collinear antiferromagnetic (AFM) order was energetically more favorable than the ferromagnetic (FM) one, which agrees with experimental findings. This conclusion was not influenced by the XC functional type employed or whether the spin–orbit effect was used. Thus, the present work does not confirm the recent DFT plane wave pseudopotential results that when including spin–orbit effects, the calculations determined that the collinear FM state had lower energy than the AFM one.     

Raman,FT‐IR,and DFT studies of 3,5‐pyrazoledicarboxylic acid and its Ce(III) and Nd(III) complexes

3,5‐Pyrazoledicarboxylic acid was used as a ligand for the synthesis of its Ce(III) and Nd(III) complexes. The complexes of Ce(III) and Nd(III) with 3,5‐pyrazoledicarboxylic acid were synthesized and their compositions were determined by elemental analysis. Vibrational study in the solid state of 3,5‐pyrazoledicarboxylic acid and its new Ce(III) and Nd(III) complexes was performed by IR and Raman spectroscopy. The changes observed between the IR and Raman spectra of the ligand and of the complexes allowed us to establish the coordination mode of the metal in both complexes. The comparative vibrational analysis of the free ligand and its lanthanide(III) complexes gave evidence that 3,5‐pyrazoledicarboxylic acid binds Ln(III) through the deprotonated carboxylic oxygens. The density functional theory (DFT) calculated geometries, harmonic vibrational modes and Raman scattering activities of the ligand were in good agreement with the experimental data, and a complete vibrational assignment is being proposed. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The effect of the intramolecular hydrogen bonds in the ligand on vibrational mode positions is also discussed. The characteristic IR and Raman bands of 3,5‐pyrazoledicarboxylic acid and its lanthanide complexes were specified and discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Theoretical and spectroscopic studies of 5‐aminoorotic acid and its new lanthanide(III) complexes

The complexes of cerium(III) and neodymium(III) were synthesized by reaction of the respective inorganic salts with 5‐aminoorotic acid (H₄L) in amounts equal to the metal:ligand molar ratio of 1:3. The structures of the final complexes were determined by means of spectral (IR, Raman, ¹H NMR and ¹³C NMR) and elemental analysis. Significant differences in the IR spectra of the complexes were observed as compared to the spectrum of the ligand. A comparative analysis of the Raman spectra of the complexes with that of the free H₄L allowed a straightforward assignment of the vibrations of the ligand groups involved in coordination. The geometry of H₄L was computed and optimized for the first time with the Gaussian03 program using the B3PW91/6‐311++G**, B3PW91/LANL2DZ, B3LYP/6‐311++G** and B3LYP/LANL2DZ methods. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The vibrational analysis performed for the studied species, H₄L and its complexes, helped to explain the vibrational behavior of the ligand vibrational modes sensitive to interaction with the lanthanides. The vibrational study gave evidence for the coordination mode of the ligand to lanthanide ions and was in agreement with the other theoretical prediction. Copyright © 2006 John Wiley & Sons, Ltd.     

氧化镁纳米管团簇电子结构的密度泛函研究

用密度泛函理论（DFT）的杂化密度泛函B3LYP方法在6-31G（d）基组水平上对MgO纳米管团簇的二元环双管、三元环、三元环双管三种构型共21个团簇进行优化,对各构型的平均结合能、能隙、平均原子电荷以及总电荷密度进行了理论研究. 结果表明,平均结合能和配位数呈线性关系;随着纳米管的生长,团簇的稳定性增加,其中以三元环纳米管最为稳定;生长过程中发生原子间的电荷转移现象,预测出至无限长时的平均原子电荷分别为1298,1270,1306;混合离子共价键始终存在于MgO纳米管团簇之中. 关键词： 氧化镁 纳米管团簇 密度泛函理论 电子结构     

Role of annealing on morphological,linear and nonlinear properties of nanoparticle of Tris [2-phenylpyridinato-C2, N] Iridium III films prepared by electron beam evaporator

Tris(2-phenylpyridinato-C₂, N] Iridium III, Ir(ppy)₃, is experimentally investigated as a novel deposited thin film. Ir(ppy)₃ thin films were fabricated by the electron beam evaporator technique. X-ray diffraction (XRD) of Ir(ppy)₃ powder is investigated to be polycrystalline with triclinic crystal. XRD pattern of Ir(ppy)₃ film and the annealed film is analyzed, and the average of crystallite size slightly increases with thermal annealing from 14 to 40 nm. The linear optical parameters were estimated and found that the annealing effect on lattice dielectric constants, dispersion energy, oscillator energy, and the ratio of carrier concentration to its effective mass. The Urbach energy and optical energy gap are estimated at different thermal annealing. On the other hand, dielectric constants and optical conductivity were estimated and found that the annealing plays a remarkable role in the increasing of their values. The calculated values of third-order susceptibility were increased by thermal annealing. Thus, the thermal annealing can be utilized as a tool to modify the optical properties of Ir(ppy)₃ films, which can be used in many important applications such as high capacity communication network.     

苯乙烯化苯酚的密度泛函研究

以苯乙烯化苯酚(SP-2)为研究对象,采用密度泛函理论的M06-2X/6-311g(d,p)方法,进行了分子结构优化.在此基础上,对其分子轨道、能级、最高占据轨道(HOMO)和最低空轨道(LUMO)、红外光谱(IR)、核磁共振谱(NMR)、紫外-可见吸收光谱(UV-Vis)进行了模拟计算.根据能级和分子轨道计算结果,主要讨论了苯乙烯化苯酚的最高占据轨道(HOMO)和最低空轨道(LUMO)的特点;获得了红外光谱(IR)、核磁共振谱(NMR)、紫外-可见吸收光谱(UV-Vis)计算结果,并对谱图数据进行了分析讨论.