Unusual Effects of the Metal Center Coordination Mode on the Photophysical Behavior of the Rhenium(I) and Rhenium(I)-Iridium(III) Complexes.

Binuclear transition-metal complexes based on conjugated systems containing coordinating functions are potentially suitable for a wide range of applications, including light-emitting materials, sensors, light-harvesting systems, photocatalysts, etc., due to energy-transfer processes between chromophore centers. Herein we report on the synthesis, characterization, photophysical, and theoretical studies of relatively rare rhenium(I) and rhenium(I)-iridium(III) dyads prepared by using the nonsymmetrical polytopic ligands ( and ) with the strongly conjugated phenanthroline and imidazole-quinoline/pyridine coordinating fragments.

DFT Study of WS-Based Nanotubes Electronic Properties under Torsion Deformations.

In this study, the influence of torsional deformations on the properties of chiral WS-based nanotubes was investigated. All calculations presented in this study were performed using the density functional theory (DFT) and atomic gaussian type orbitals basis set. Nanotubes with chirality indices (8, 2), (12, 3), (24, 6) and (36, 9) corresponding to diameters of 10.

Current State of Computational Modeling of Nanohelicenes.

This review considers the works that focus on various aspects of the theoretical description of nanohelicenes (other equivalent names are graphene spirals, graphene helicoid, helical graphene nanoribbon, or helical graphene)-a promising class of one-dimensional nanostructures. The intrinsic helical topology and continuous π-system lead to the manifestation of unique optical, electronic, and magnetic properties that are also highly dependent on axial and torsion strains. In this paper, it was shown that the properties of nanohelicenes are mainly associated with the peripheral modification of the nanohelicene ribbon.

Magnetic Properties of Zig-Zag-Edged Hexagonal Nanohelicenes: A Quantum Chemical Study.

The atomic structure and electronic and magnetic properties of two zig-zag-edged hexagonal nanohelicenes of the second type [1.2] and [2.2] were studied by the density functional theory.

Nonsymmetric [Pt(C^N*N'^C')] Complexes: Aggregation-Induced Emission in the Solid State and in Nanoparticles Tuned by Ligand Structure.

Invited for the cover of this issue are the groups of Sergey P. Tunik and his colleagues from St Petersburg University. The image depicts the strong bathochromic shift of the emission wavelength of phosphorescent platinum(II) complexes upon their aggregation in the presence of water.

Nonsymmetric [Pt(C^N*N'^C')] Complexes: Aggregation-Induced Emission in the Solid State and in Nanoparticles Tuned by Ligand Structure.

Five square-planar [Pt(C^N*N'^C')] complexes (Pt1-Pt5) with novel nonsymmetric tetradentate ligands (L1-L5) were synthesized and characterized. Varying the structure of the metalating aromatic systems result in substantial changes in photophysical properties and intermolecular interaction mode of the complexes in solution and in solid state. The complexes are strongly emissive in tetrahydrofuran solution, with the band maxima ranging from 560 to 690 nm.

Spin splitting in monoperiodic systems described by magnetic line groups.

In this paper we report the classification of all the 81 magnetic line group families into seven spin splitting prototypes, in analogy to the similar classification previously reported for the 1651 magnetic space groups, 528 magnetic layer groups, and 394 magnetic rod groups. According to this classification, electrically induced (Pekar-Rashba) spin splitting is possible in the antiferromagnetic structures described by magnetic line groups of type I (no anti-unitary operations) and III, both in the presence and in the absence of the space inversion operation. As a specific example, a group theoretical analysis of spin splitting in CoO (8, 8) nanotube is carried out and its predictions are confirmed bydensity functional theory calculations.

Colossal Spin Splitting in the Monolayer of the Collinear Antiferromagnet MnF.

In this Letter we report on the colossal spin splitting (on the order of several electronvolts) in the collinear antiferromagnetic (AFM) MnF (110) monolayer, which we obtained from first-principles calculations and explain in terms of group-theoretical analysis. This Pekar-Rashba AFM-induced spin splitting with a magnetic mechanism does not require the presence of spin-orbit coupling such as with a traditional Rashba-Dresselhaus electric mechanism. Furthermore, it was observed for all wave vectors, including high-symmetry points of the two-dimensional (2D) Brillouin zone.

Argentophillic interactions in argentum chalcogenides: First principles calculations and topological analysis of electron density.

The plasticity of Ag S and Ag Se crystals important for applications is associated mainly with AgAg metallophilic bonds, which are related to van der Waals interactions and therefore are not directed. This is demonstrated by the first principles DFT M06 LCAO calculations of Ag X (X = S, Se) crystals (periodic model) and hypothetical molecules X Ag (X = S, Se; n = 1, 2, 4) in gas phase (molecular model). A topological analysis of the calculated electron density, was performed both for periodic and molecular models of Ag X (X = S, Se).

Topological analysis of chemical bonding in the layered FePSe upon pressure-induced phase transitions.

Two pressure-induced phase transitions have been theoretically studied in the layered iron phosphorus triselenide (FePSe ). Topological analysis of chemical bonding in FePSe has been performed based on the results of first-principles calculations within the periodic linear combination of atomic orbitals (LCAO) method with hybrid Hartree-Fock-DFT B3LYP functional. The first transition at about 6 GPa is accompanied by the symmetry change from to C2/m, whereas the semiconductor-to-metal transition (SMT) occurs at about 13 GPa leading to the symmetry change from C2/m to .

Luminescent organic dyes containing a phenanthro[9,10-D]imidazole core and [Ir(N^C)(N^N)] complexes based on the cyclometalating and diimine ligands of this type.

A family of diimine (N^N) and cyclometalating (N^C) ligands based on a phenanthro-imidazole aromatic system: 2-pyridyl-1H-phenanthro[9,10-d]imidazole (N^N); 2-R-1-phenyl-1H-phenanthro[9,10-d]imidazole, R = phenyl (N^C4), 3-iodophenyl (N^C5) and 4-nitrophenyl (N^C6) were prepared. It was found that N^C4 and N^C5 show π-π* fluorescence typical of aromatic systems of this sort, whereas the donor-acceptor architecture of N^C6 leads to strong emission solvatochromism and acidochromism, indicating the charge transfer character of the fluorescence observed. Six iridium(iii) complexes (1-6) [Ir(N^C#)2(N^N)]+, where # = 1-6 and N^C1 = 2-phenylpyridine, N^C2 = 2-(benzo[b]thiophen-2-yl)pyridine, and N^C3 = methyl 2-phenylquinoline-4-carboxylate, were also synthesized and characterized.

Functionalized Pt(II) and Ir(III) NIR Emitters and Their Covalent Conjugates with Polymer-Based Nanocarriers.

Two NIR-emitting platinum [Pt(N^N^C)(phosphine)] and iridium [Ir(N^C)2(N^N)] complexes containing reactive succinimide groups were synthesized and characterized with spectroscopic methods (, 1-phenyl-3-(pyridin-2-yl)benzo[4,5]imidazo[1,2-]pyrazine, , 6-(2-benzothienyl)phenanthridine, phosphine-3-(diphenylphosphaneyl)propanoic acid -hydroxysuccinimide ether, and , 4-oxo-4-((1-(pyridin-2-yl)-1-1,2,3-triazol-4-yl)methoxy)butanoic acid -hydroxysuccinimide ether). Their photophysics were carefully studied and analyzed using time-dependent density functional theory calculations. These complexes were used to prepare luminescent micro- and nanoparticles with the "core-shell" morphology, where the core consisted of biodegradable polymers of different hydrophobicity, namely, poly(d,l-lactic acid), poly(ε-caprolactone), and poly(ω-pentadecalactone), whereas the shell was formed by covalent conjugation with poly(l-lysine) covalently labeled with the platinum and iridium emitters.

Origin of pressure-induced insulator-to-metal transition in the van der Waals compound FePS from first-principles calculations.

Pressure-induced insulator-to-metal transition (IMT) has been studied in the van der Waals compound iron thiophosphate (FePS ) using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid Hartree-Fock-DFT B3LYP functional. Our calculations reproduce correctly the IMT at ∼15 GPa, which is accompanied by a reduction of the unit cell volume and of the vdW gap. We found from the detailed analysis of the projected density of states that the 3p states of phosphorus atoms contribute significantly at the bottom of the conduction band.

First-principles comparative study of perfect and defective CsPbX (X = Br, I) crystals.

First principles Density Functional Theory (DFT) hybrid functional PBESOL0 calculations of the atomic and electronic structure of perfect CsPbI3, CsPbBr3 and CsPbCl3 crystals, as well as defective CsPbI3 and CsPbBr3 crystals are performed and discussed. For the perfect structure, decomposition energy into binary compounds (CsX and PbX2) is calculated, and a stability trend of the form CsPbBr3 > CsPbI3 > CsPbCl3 is found. In addition, calculations of the temperature-dependent heat capacity are performed and shown to be in good agreement with experimental data.

First-Principles Calculations of Phonons and Thermodynamic Properties of Zr(Hf)S -Based Nanotubes.

Comparative hybrid density functional calculations on the structure, stability, and phonon frequencies of monolayers and single-walled nanotubes are performed for Zr(Hf)S disulfides. The first-principles calculations of HfS -based nanotubes are made for the first time. The symmetry analysis of infrared and Raman active vibrational modes in ZrS and HfS nanotubes is made using the induced representations of the isogonal point groups of line groups.

The site-symmetry induced representations of layer groups on the Bilbao Crystallographic Server.

The section of the Bilbao Crystallographic Server (http://www.cryst.ehu.

First-Principles Evaluation of the Morphology of WS Nanotubes for Application as Visible-Light-Driven Water-Splitting Photocatalysts.

One-dimensional tungsten disulfide (WS) single-walled nanotubes (NTs) with either achiral, i.e., armchair (, ) and zigzag-type (, 0), or chiral (2, ) configuration with diameters > 1.

First-principles calculations of iodine-related point defects in CsPbI.

We present here first principles hybrid functional calculations of the atomic and electronic structure of several iodine-related point defects in CsPbI, a material relevant for photovoltaic applications. We show that the presence of neutral interstitial I atoms or electron holes leads to the formation of di-halide dumbbells of I (analogous to the well-known situation in alkali halides). Their formation and one-electron energies in the band gap are determined.

Infrared and Raman active vibrational modes in MoS -based nanotubes: Symmetry analysis and first-principles calculations.

The possibility to use the axial point group dynamical representations for the infrared and Raman active modes classification in nanotubes is analyzed. The method proposed allows one to obtain the results of phonon symmetry analysis for nanotubes in Mulliken designations, which are traditional for molecules and crystallographic point groups. The approach suggested is applied to the phonon symmetry analysis in the single-wall carbon and MoS -based nanotubes.

Temperature dependence of thermodynamic properties of MoS monolayer and single-wall nanotubes: Application of the developed three-body force field.

MoS nanostructures, especially mono-, multilayer nanothin films as well as single- and multiwall nanotubes are rather interesting popular objects in nanomaterials chemistry. The thermodynamic properties of inorganic nanotubes, and the temperature dependence of their properties can be efficiently investigated by first-principles and molecular mechanics methods in the framework of harmonic approximation. At the same time, only thin single-wall nanotubes are available for the first-principles calculations.

First-principles calculations of oxygen interstitials in corundum: a site symmetry approach.

Using site symmetry analysis, four possible positions of interstitial oxygen atoms in the α-AlO hexagonal structure have been identified and studied. First principles hybrid functional calculations of the relevant atomic and electronic structures for interstitial O atom insertion in these positions reveal differences in energies of ∼1.5 eV.

First-principles calculations on Fe-Pt nanoclusters of various morphologies.

Bimetallic FePt nanoparticles with L1 structure are attracting a lot of attention due to their high magnetocrystalline anisotropy and high coercivity what makes them potential material for storage of ultra-high density magnetic data. FePt nanoclusters are considered also as nanocatalysts for growth of carbon nanotubes of different chiralities. Using the DFT-LCAO CRYSTAL14 code, we have performed large-scale spin-polarized calculations on 19 different polyhedral structures of FePt nanoparticles in order to estimate which icosahedral or hcp-structured morphology is the energetically more preferable.

Phonon spectra, electronic, and thermodynamic properties of WS nanotubes.

Hybrid density functional theory calculations are performed for the first time on the phonon dispersion and thermodynamic properties of WS -based single-wall nanotubes. Symmetry analysis is presented for phonon modes in nanotubes using the standard (crystallographic) factorization for line groups. Symmetry and the number of infra-red and Raman active modes in achiral WS nanotubes are given for armchair and zigzag chiralities.

First-principles modeling of hafnia-based nanotubes.

Hybrid density functional theory calculations were performed for the first time on structure, stability, phonon frequencies, and thermodynamic functions of hafnia-based single-wall nanotubes. The nanotubes were rolled up from the thin free layers of cubic and tetragonal phases of HfO . It was shown that the most stable HfO single-wall nanotubes can be obtained from hexagonal (111) layer of the cubic phase.

Use of site symmetry in supercell models of defective crystals: polarons in CeO.

In supercell calculations of defective crystals, it is common to place a point defect or vacancy in the atomic position with the highest possible point symmetry. Then, the initial atomic structure is often arbitrary distorted before its optimization, which searches for the total energy minimum. In this paper, we suggest an alternative approach to the application of supercell models and show that it is necessary to preliminarily analyze the site symmetry of the split Wyckoff positions of the perfect crystal supercell atoms (which will be substituted or removed in defective crystals) and then perform supercell calculations with point defects for different possible site symmetries, to find the energetically most favorable defect configuration, which does not necessarily correspond to the highest site symmetry.