Quantum chemical investigation on complexation of palladium with iminopyridyl ligands: Structural,thermochemical, and electronic aspects

The main purpose of this research is to investigate computationally the structural, thermochemical and electronic properties in complexation process of dichloride {N-[(5-methylthiophen-2-yl)methylidene]?2-(pyridine-2-yl)ethanamine-κ²N,N′}palladium(II) complex. In the first step, we have concentrated on comparative survey of ability of density functional theory (DFT) and also semi-empirical approaches to reproduce the crystal structure of palladium(II) complex. Comparison of our calculated structural parameters of aforementioned complex with the available crystallographical data reveals that both functionals (B3LYP and M06) can well-reproduce x-ray structure of the complex with a near accuracy while PM6-D2 semi-empirical calculated values are not in a reliable agreement with the crystallographical data.

In the next step, we have shown the thermodynamical superiority in using THF as a polar solventin complexation reaction via polarized continuum model (PCM) computations which is in confirmation with experimental observations. Additionally, the bond orders of some selected key bonds in C₁₃H₁₄N₂Sligand andPdCl₂(C₁₃H₁₄N₂S) complex have been evaluated comparatively to analyze the electronic behavior of coordination.

Finally, we focused on topological analysis of electron density function via quantum theory of atoms in molecules (QTAIM) approach to explore the strength and nature of metal-ligand interactions on bond and ring critical points (BCPs).Strictly speaking, QTAIM calculations have been performed to determine the electronic density, its Laplacian and other electronic energy density indicators on some key BCPs to interpret the electronic features of complexation.     

Theoretical Study of Xanthenone and Phenothiazine Derivatives for Blue TADF Emitter

Two novel thermally activated delayed fluorescence (TADF) materials (PTZ-XTN and 2PTZ-XTN), with phenothiazine (PTZ) as an electron donor and xanthenone derivatives (XTN) as electron acceptors, were designed and theoretically investigated as blue OLED emitters. We used density functional theory (DFT) and time dependent DFT (TD-DFT) calculations to determine the electron distribution of HOMO and LUMO and the energy of the lowest singlet (S₁) and the lowest triplet (T₁) excited states. The large dihedral angle between the electron donor and the electron acceptor imparted a small spatial overlap between HOMO and LUMO in all the materials. This charge separation of the HOMO and LUMO leads to a small energy gap between the S₁ state and T₁ state, thereby leading to TADF emission. Among the materials studied, PTZ-XTN has the most suitable properties for a blue TADF OLED emitter, even though 2PTZ-XTN has the smallest energy gap between the S₁ and T₁ states.     

Role of sublattices in the formation of electron density in metal nitrites

The self-consistent valence electron densities of NaNO₂, AgNO₂, and their constituent sublattices are calculated on the basis of the theory of the local-density functional. The quantity characterizing the relation between different sublattices is introduced as the difference density resulting from the subtraction of the densities of the individual sublattices from the total electron density. The role of metal in the formation of electron density is established, and, in particular, it is shown that, in AgNO₂, anionic bonds have the covalent component formed at the expense of the electron density of the cation. It is also shown that, qualitatively, the difference density in NaNO₂ corresponds to the experimental deformation density.     

Urbach rule in photoelectron emission from surface states of low-sized silica

Spectral and temperature dependences of photoelectron emission from surface (interface) states of SiO₂ films and nanocompacts in the near UV region were studied. They were interpreted in terms of ‘frozen phonons’ conception and modified three-stage electron emission model. The electron emission analog of optical Urbach rule for low-sized silica was proposed. Optical absorption stage was recognized as the dominant phase of electron emission process. The structure and energy parameters of studied samples were obtained. It was revealed that thin and thick SiO₂ films have similar structure parameters while their effective potential barriers differ because of different electron transport conditions. High value of static structural disorder in compacted SiO₂ nanopowders is attributed to peculiarities of their ultradispersed structure.     

Structural,electrochemical and optical properties of 4′-n-alkyl-4-cyanobiphenyl (nCB) – A computational approach

The structures of nCB (n = 6 & 7 where n is the number of carbon atoms in the alkyl chain) have been optimized using the Becke3-Lee-Yang-Parr (B3LYP) hybrid functional with 6–31G+(d) basis set using the crystallographic geometry as input. The electronic structures of the dimer molecules have been computed using the optimized geometries. The spectra of the dimer molecules have been calculated by employing the DFT method. The features of electronic transitions and excited states have been calculated via configuration interaction singles (CIS) with the semiempirical Hamiltonian Zerner intermediate neglect of differential overlap (ZINDO). The photo sensitivity of liquid crystalline alkyl cyanobiphenyl has been presented on ultraviolet (UV) absorption based approach through Density functional theory (DFT) calculations. The structural and electrochemical properties such as HOMO (H), LUMO (L), and energy gap (Eg = E_L – E_H) have been investigated. A comparison of dimers during the different modes of interactions suggests an absorption maxima at longer wavelength for 7CB, indicating the high photo sensitivity. Further, the 6CB dimers exhibit a lower band gap; hence its conductivity is high in comparison with the 7CB dimers.     

Low temperature photoluminescence studies on semiorganic tris thiourea copper (I) chloride single crystal

Semiorganic tris thiourea copper (I) chloride (TTCC) single crystals have been synthesized from copper (II) chloride via slow evaporation technique. The stoichiometry of the grown anhydrous complex crystal has been confirmed by elemental CHNS (C, H, N and S) and atomic absorption spectrophotometric (AAS) analysis. The crystal structure with space group has been confirmed by single crystal and powder X‐ray diffraction (XRD) studies. The FTIR study assigned the presence of functional groups and confirmed the co‐ordination of metal ions with thiourea. It also confirmed the transition from Cu²⁺ to Cu⁺ when thiourea combined with Copper (II) chloride. The optical transparency of the crystal has been studied by UV‐Vis spectrum and deduced the energy gap. The room temperature Photoluminescence (PL) spectrum reported maximum emission line at 410.92 nm and Stokes shift has been determined as 75 nm or 16.5 eV. Low temperature luminescence study from 300 K to 77 K exhibited three blue emission peaks and one green emission peak. The green emission band has been assigned to recombination of an electron in a shallow trap and Cu²⁺. Blue emission has been attributed to S^2‐ vacancies. The interesting hysteresis loop has been exhibited by the variation of energy gap with low temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Characteristics of EDTA's Transition Metal Complexes (III) The d-d Transition Spectrum and Structure Characteristic of [Pb.Ni(HEDTA)H2O] Cl Crystal

The electronic absorption spectrum of crystals of the title compound [Pb.Ni(HEDTA) H₂O] Cl was recorded and discussed quantitatively. Using ligand field theory and the radial wave function of bound Ni(II) ion, the d-d transition energy levels of crystals of [Pb.Ni(HEDTA) H₂O] Cl, Ca [Ni(EDTA)] · 4H₂O, [Li.Ni(HEDTA) H₂O], [NiH₂EDTA)H₂O] were calculated. The different structure characteristics of EDTA's metal complexes are evidently shown in their d-d transition spectra.     

Optical and morphological properties of porous diamond-like-carbon films deposited by magnetron sputtering

Porous diamond-like-carbon (PDLC) thin films obtained on silicon substrate by DC low energy magnetron sputtering have been investigated by photoluminescence, transmission and reflection spectroscopy, photoacoustic and spectroscopic ellipsometry. The absorption features observed for these films show similarities with those of porous silicon (PS) as well as in the performed gradient structural pattern classification of the SFM porosity, by means of the computational GPA-flyby environment on PS and PDLC samples. The dielectric function is also calculated for the bulk diamond-like carbon using the full-potential linearized augmented plane wave method within the framework of local density approximation to density functional theory. From the measurement a low real dielectric constant of about 4.5 at 0.8 eV was found whereas the calculated e₁(0) for the bulk diamond has a value of 5.5.     

Influence of temperature on the microcrystalline structure of thermally evaporated Sb2S3 thin films

Thin films of antimony trisulfide (Sb₂S₃) were prepared by thermal evaporation under vacuum (p=5×10^–5 torr) on glass substrates maintained at various temperatures between 293 K and 523 K. Their microstructural properties have obtained by transmission electron microscopy (TEM). The electron diffraction analysis showed the occurrence of amorphous to polycrystalline transition in the films deposited at higher temperature of substrates (523 K). The polycrystalline thin films were found to have an orthorhombic structure. The interplanar distances and unit‐cell parameters were determined by high‐resolution transmission electron microscopy (HRTEM) and compared with the standard values for Sb₂S₃. The surface morphology of Sb₂S₃ thin films was investigated by scanning electron microscopy (SEM). The optical transmission spectra at normal incidence of Sb₂S₃ thin films have been measured in the spectral range of 400–1400 nm. The analysis of the absorption spectra revealed indirect energy gaps, characterizing of amorphous films, while the polycrystalline films exhibited direct energy gap. From the photon energy dependence of absorption coefficient, the optical band gap energy, E_g, were calculated for each thin films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The d-d Transition Spectra of Copper (II) Complexes in Different Coordination Environment. Study on Cu(TTA)2 and Cu2(sacch)4(Im)4

The d-d transition spectra of Cu(TTA)₂ and Cu₂(sacch)₄(Im)₄ complexes crystals have been determined. Using the crystal structure data, their d-d transition energy levels are calculated by the program which we used for the calculation of field theory. The calculated values are in good accordance with the experimental results. Compared to the copper(II) complexes in various coordination environments, their d-d transition spectra have an evident difference.     

Theoretical Design Study on the Electronic Structures and Phosphorescent Properties of Four Iridium(III) Complexes

The geometry structures, electronic structures, absorption, and phosphorescent properties of four Ir(III) complexes have been investigated using the density functional method. Calculations of ionization potential (IP) and electron affinity (EA) were used to evaluate the injection abilities of holes and electrons into these complexes. The result also indicates that the –CF₃ substituent group on the ligand not only change the character of transition but affect the rate and balance of charge transfer. The lowest energy absorption wavelengths are located at 428 nm for 1a, 446 nm for 1b, 385 nm for 2a, and 399 nm for 2b, respectively, in good agreement with the energy gap (ΔE_L-H) trend because the HOMO–LUMO transition configurations are predominantly responsible for the S₀→S₁ transition. 2b has the 433 nm blue emission, which might be a potential candidate for blue emitters in phosphorescent dopant emitters in organic light emitting diodes (OLEDs). The study could provide constructive information for designing novel OLEDs materials in the future.

[Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.]     

On the morphology of BaMoO4 crystals: A theoretical and experimental approach

BaMoO₄ crystals were obtained by a co‐precipitation method, and their structures were characterized by X‐ray diffraction and Rietveld refinement techniques. Field emission scanning electron microscopy was utilized to investigate the morphology of the as‐synthesized aggregates.‐ Through systematic first principle calculations within the density functional theory method at the B3LYP level, we investigated the structure; the surface stability of the (001), (101), (110), (100), (111), and (112) surfaces; and the morphological transformations of BaMoO₄. The relative surfaces energies were further varied to predict a complete map of the available morphologies through a Wulff construction approach. This revealed that the obtained experimental and theoretical morphologies coincided when the surface energy values of the (001) surface decreased while those of the (100) and (101) facets increased simultaneously. Analysis of the surface structures showed that the electronic properties were associated with the presence of undercoordinated [BaO_x] (x = 4, 5, and 6) and [MoO_y] (y = 3) clusters. The presented results provide a comprehensive catalog of the morphologies most likely to be present under realistic conditions, and will serve as a starting point for future studies on the surface chemistry of BaMoO₄ crystals.     

Thermally activated delayed fluorescence host materials based on triphenylphosphine oxide derivatives

Abstract

Novel thermally activated delayed fluorescence (TADF) host molecules for blue electrophosphorescence were developed by combining the electron donor acridine derivatives with the electron acceptor triphenylphosphine oxide unit in a single molecule based on density functional theory. We obtained the energies of the first excited singlet (S₁) and triplet (T₁) states of the TADF materials by performing procedures in accordance with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to the ground state using dependence on the charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. Using DFT and TD-DFT calculations, the significant separation between the HOMO and LUMO caused a small difference in energy (ΔE_ST) between the S₁ and T₁ states. The host molecules retained high triplet energy and showed great potential for use in blue phosphorescent organic light-emitting diodes. The results also showed that these molecules are promising TADF host materials because they demonstrate a low barrier to hole and electron injection, balanced charge transport for both holes and electrons, and small ΔE_ST.     

不同位置Mg掺杂ZnO电荷转移和光学性质的第一性原理研究

基于密度泛函理论计算了本征氧化锌、6.25%Mg以及同位、邻位、间位12.5%Mg原子掺杂氧化锌晶体的几何结构、原子轨道电子布居、静电势和电子结构特征;探究了Mg原子掺杂对氧化锌能带结构、态密度以及对应的光学性质和电学性质的影响。结果表明Mg掺杂会导致氧化锌晶体的晶格体积变大,载流子迁移率降低和吸收边蓝移;邻位双原子掺杂(ZnO+2Mg-ac、ZnO+2Mg-ad)可以显著降低氧化锌的光吸收系数和反射率,提升对太阳光的透过率;Mg掺杂氧化锌晶体适用于制作高质量光学透射膜。     

2 μm spectroscopic investigation of Tm3+-doped tellurite glass fiber

TmF₃ doped TeO₂–ZnO–La₂O₃ (TZL) glasses and fibers have been prepared by the conventional melt-quenching and suction casting methods, respectively. 2 μm emission properties and energy transfer mechanisms of the TZL glasses and fibers have been analyzed and discussed. The oscillator strength, Judd–Ofelt parameters, radiative transition probability and radiative lifetime of Tm³⁺ have been calculated based on the absorption spectra and Judd–Ofelt theory. The maximum emission cross-section of Tm³⁺ is 6.9 × 10^?21 cm² near 2 μm. Emission spectra have been obtained from both TZL fibers and bulk glass when excited with a 794 nm pump. The results of 2 μm emission spectra indicate that the line width of Tm³⁺ measured in fibers is narrower than that in the bulk glass sample. The peak position of the emission spectra shifts to longer wavelength with increment of the fiber length.     

Phase Resolution Method of PA Spectra in Copper(II)-EDTA Complexes

The complexes crystals of Cu(H₂EDTA) · H₂O and CaCu(EDTA) · 4 H₂O were synthesized and their photoacoustic spectra were determined in the region of 300–800 nm at room temperature. A method used to directly monitor both position and strength of the absorption bands of respective electronic states were proposed. With the amplifier and phase spectra all absorption peaks of different electronic states could be distinguished. The PA spectra were also explained by the 3d orbit radial scaling theory. All the d-d transition absorption peaks calculated are in good agreement with the experimental values. In addition, the non-radiative relaxation process and the relaxation time of excitation electron were discussed with the PA spectra.     

Growth and Optical Properties of Doped LiTaO3 Single Crystals

Single crystals of lithium tantalate (LiTaO₃) doped with Pr, Nd + Yb and Tm were grown by the Czochralski method. A thermal system with 50 mm diameter iridium crucible and two different afterheaters (active and passive) was checked with respect to temperature distribution in a pulling region. The obtained crystals were up to 20 mm in diameter and up 50 mm in length. Crystals were poled, and the Curie temperature was determined for specimens cut of from different parts of single crystals. The polarized absorption spectra, time resolved emission spectra and emission lifetime of Pr³⁺ doped LiTaO₃ crystals were measured. An intense emission from the ³P₀ level was observed. Optical properties of the Yb³⁺ ions excited by energy transfer from Nd3+ ions have been researched for LiTaO₃:Nd, Yb crystals.     

Synthesis,structural characterization,Hirshfeld surface analysis,and theoretical investigations of bis(benzene-1,2-dicarboxylato)bis(4-methylbenzohydrazide)zinc

Single crystals of bis(benzene-1,2-dicarboxylato)bis(4-methylbenzohydrazide)zinc (ZPTH), a novel Zn(II) complex of phthalic acid and hydrazide, were grown from aqueous solution by slow evaporation solution growth technique. The compound C₃₂H₃₀N₄O₁₀Zn crystallizes in triclinic system with centrosymmetric space group Pī. Its structure is built up from octahedral (ZnO₄N₂) linked to each other through the phthalate and hydrazide groups. The good crystallinity of the as-grown specimen is confirmed by the powder X-ray diffraction pattern. The band gap energy is estimated using diffuse reflectance data by the application of Kubelka–Munk algorithm. ZPTH exhibits fluorescent emission at 401?nm in the solid state at room temperature. Theoretical calculations were performed using density functional theory (DFT) method. Experimental observations are well supported by theoretical studies.GRAPHICAL ABSTRACT     

Optical properties and synthesis of CuInSe2 thin films by selenization of Cu/In layers

In this paper, we report the effect of annealing temperature on the properties of copper indium diselenide (CuInSe₂) thin films. The CuInSe₂ thin films were fabricated at 500 °C for 2 h by annealing Cu‐In layers (as precursors) selenized in a glass tube with pure selenium powder. The structural and morphological properties of the CuInSe₂ thin films were characterized respectively by means of x‐ray diffraction (XRD) and field‐emission scanning electron microscope (FE‐SEM). The type of CuInSe₂ thin film has been identified as direct allowed and the band gap value was determined. The study of UV/Visible/NIR absorption shows that the band gap value of CuInSe₂ thin film is about 1.07 eV, which is within an optimal range for harvesting solar radiation energy. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)