Molecular assemblies driven by non-covalent interactions have sparked enormous interest in the last decade, due to their high versatility, flexibility, and recoverability. To figure out the interplay of the non-covalent interactions, such as hydrogen bonding (HB), electrostatic interaction, stacking, metal–organic coordination, van der Waals (vdW) forces, etc., intensive attention has been focused on the sophisticated systems composed of multiple components that are balanced by multiple non-covalent interactions.

Theoretical investigations have been carried out with an extended semiempirical atom superposition and electron delocalization (ASED+, Atom Superposition, and Electron Delocalization), based on the extended Hückel molecular orbital theory. Calculated STM images were obtained within the EHMO-ESQC method (Extended Hückel Molecular Orbital–Elastic-Scattering Quantum Chemistry), which describes the electronic scattering between the substrate and the tip by modeling the chemical structure of the tunnel gap (substrate, molecule, tip apex, and tip substrate).

Molecular Landers are a distinctive family of molecules, with bulky functional groups acting as the legs to lift up the aromatic molecular board. When the compounds are adsorbed on surfaces, only the legs are in contact with the surface, while the molecular board is decoupled from the substrate. To align these Landers into extended and well-ordered arrangements, different routes have been employed. In our previous work, we have demonstrated that one-dimensional (1D) and two-dimensional (2D) well-ordered assemblies of Landers can be observed not only between the same compounds, but also between hetero-Landers. However, all these interactions occurred when the molecular boards have an identical or comparable height, while the possibility of bonding between Landers and legless molecules remains unknown. Moreover, besides the two routes mentioned above, guest–host chemistry has been recognized as another fascinating way to align molecules on surfaces.

Arranging plasmonic nanomaterials in a certain way can create materials with special optical properties, such as having anisotropy with refractive indices of simultaneously opposite signs for opposite light polarization. This type of material can be based on doping a liquid crystal system with nanoparticles with the indicated properties. Gold nanorods (AuNRs) are rod-shaped nanoparticles with size-dependent optical responses, and because of their plasmonic properties, they are used in imaging and fluorescent enhancement.

In our work, we investigated the influence of gold nanorods on the phase transitions and optical properties of the liquid crystal 8CB, known for its thermotropic behaviour. Gold nanorods were synthesized using a seed-mediated approach to obtain nanoparticles with the desired dimensions (aspect ratios: 5,6; 8,2; 10,8), which were observed and measured using transmission electron microscopy. Different concentrations of AuNRs were added to the 8CB samples, which were then inserted into liquid crystalline cells. All the samples were observed under a polarized light microscope equipped with a heating stage. At each concentration of the AuNRs, different optical structures were observed in both the nematic and smectic phases. The temperatures of the phase transitions also differed depending on the amount of the AuNR dopant in the system. The observed changes obtained by doping 8CB-based systems with nanoparticles may lead to the design of new metamaterials.

Introduction. Hexadentate N₆ macrocycles could be adequate for obtaining lanthanoid complexes with coordination number 8 and axial hexagonal bipyramidal geometry. However, achieving this is not straightforward, as the geometry of these complexes is strongly influenced not only by the flexibility of the macrocycle but also by the features of the selected ancillary donors, as indicated by some prior findings using chloride and nitrate as auxiliary ligands in macrocyclic lanthanoid complexes.

Synthesis and methods. With the intention of delving deeper into this issue, we present here the result of the synthesis and crystallographic characterization of the dysprosium complex [DyL(OAc)₂]OAc·7H₂O, arisen from the interaction of dysprosium acetate tetrahydrate and a macrocyclic hexaazatetramine ligand, derived from diacetylpyridine (L = 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane) in a 1:1 molar ratio in chloroform. Its crystal structure was solved using standard methods of single-crystal X-ray diffraction.

Results. Despite the desired trans disposition of the acetate anions, with the macrocycle L in a rather plane disposition, the dysprosium atom is deca-coordinate, as both acetate complexes behave as bidentate chelating donors, forming a mutual angle of 72.6 °. The spatial arrangement of the ligand leads to a bicapped square antiprism calculated geometry, but with a significant distortion to a sphenocorona.

Conclusion. Despite achieving a desired trans disposition for the ancillary ligands, the substitution of acetate as an auxiliary donor, instead chloride or nitrate, has not allowed us to obtain an axial octacoordinate Dy³⁺ complex, but a decacoordinate one.

Selective dimerization of 2-cyclopenten-1-one, which proceeds through the [2+2]-cycloaddition mechanism, was successfully carried out under soft UV irradiation with a reagent trapped within the pores of a metal–organic framework. Such an approach allowed us to achieve very high (up to 98%) selectivity in the formation of the head-to-tail anti-dimer, among other possible diastereomeric dimers, while a similar selectivity rarely exceeds 60% using other known approaches [Photochem. Photobiol. Sci., 2002, 1, 991] The metal–organic framework used, [Eu₂(DMF)₄(ttdc)₃] (DMF = N,N-dimethylformamide; H₂ttdc – trans-thienothiophene-2,5-dicarboxylic acid), containing regular nano-sized pores, acted as a matrix—a “reaction vessel”—which adsorbed the reagent molecules. The highly ordered arrangement of 2-cyclopenten-1-one molecules in the MOF pores, facilitated by the host–guest hydrogen bonds, predetermined the geometry of its dimer at the molecular level and subsequently the extremely high selectivity of its formation, as confirmed by ¹H NMR spectroscopy. The stability and geometric rigidity of the porous coordination network structure exclude the formation of other possible product isomers in the reaction. The crystal structure o the inclusion compound of the target product with the MOF was determined by single-crystal X-ray diffraction analysis, providing unambiguous confirmation of the reaction occurring distinctively within the voids of the coordination framework and additional insights into the reaction selectivity in terms of the host–guest interactions. Similar results were obtained for 2-methyl-2-cyclopenten-1-one, while for the 3-methylated derivative, its diastereoselective [2+2] dimerization was found to be impeded due to the different guest orientation in the MOF pores, which did not facilitate a specific product-like pre-organization of the reagent molecules [Chem. Commun., 2023, 59, 9380].

This work was supported by the Russian Science Foundation, Project № 19-73-20087.

In this research work, we conduct extensive Monte Carlo simulations to investigate the factors that affect the isotropic-to-nematic transition [1,2] of hard colloidal polymers in bulk and under various conditions of confinement. Polymers are represented as linear chains of tangent hard spheres of uniform length, with the stiffness being controlled by a bending potential leading to rod-like configurations [3]. Confinement is realized through the presence of flat, parallel and impenetrable walls in one, two or three dimensions [4], and periodic boundary conditions are applied in the unconstrained dimensions. All simulations are performed through the Simu-D software, composed of conventional and advanced, chain-connectivity-altering Monte Carlo algorithms [5].

The local and global structure of the computer-generated system configurations are gauged through the Characteristic Crystallographic Element (CCE) norm [6] and the long-range (nematic) order parameter [1]. Distinct factors, including chain length and stiffness, confinement and packing density are found to profoundly affect the isotropic-to-nematic transition at the level of chains, and the establishment of close-packed crystallites at the level of monomers.

[1] D. Andrienko, J. Mol. Liq. 267, 520 (2018).

[2] S. A. Egorov, A. Milchev, and K. Binder, Polymers 8, 296 (2016).

[3] D. Martínez-Fernandez et al., Polymers 15, 551 (2023).

[4] P. Ramos et al., Polymers 13, 1352 (2021).

[5] M. Herranz et al., Int. J. Mol. Sci. 22, 12464 (2021).

[6] P. M. Ramos et al., Crystals 10, 2073 (2020).

Point and complex defects and doping play important roles in the mechanical, physical properties and functionality of crystalline materials such as carbides. First-principle calculations of defects/doping based on density functional theory have been widely used as an effective tool for studying the influence of defect and doping elements, which is important for understanding the evolution of precipitated carbides and the development of high-performance carbides. In this study, first principle method is adapted to establish data for two typical carbides - Ni4C and Mo2C in 2D and 3D structures. A systematic approach has been developed for studying and analyzing the effects of a range of doping elements and different types of defects on the mechanical, electronic and magnetic properties.

Calculations show that there is an enhancement in magnetism of Mo2C structure when dopped with Co and Mn, which may be due to the doping elements of changing the electronic structure of Mo2C, introducing local magnetic moments. Data with Co and Mn doping in Ni4C also indicates an increase of the magnetic moment and enhancement of the magnetic performance. In addition, change of magnetic data of Mo2C is observed with some types of vacancy defects and asymmetric structure. The comparative analysis of data for 2D and 3D structures of Mo2C show that the 2D structure has different characteristics from the 3d structure when doped. These results further contribute to the understanding of effects of defects and doping elements on the mechanical and physical properties in particular magnetism of carbides. The potential link between the data to the understanding of carbide formation and their use in new emerging areas is analysed. The issues and use of the data in integrated approaches combining modelling, experimental and data analysis is discussed.

Photonic liquid crystal (LC) phases, such as blue phases (BPs) and the cholesteric phase (ChP), have contributed to a variety of photonic devices due to their three-dimensional and one-dimensional photonic band gaps (PBGs), respectively. These phases exhibit a helical periodic structure, which functions as a PBG that selectively reflects circularly polarized light (CPL). Tuning the PBG by adjusting its pitch length and extending the thermal stability and design applications of these phases have been significant research objectives over the last decade. Recently, a promising approach for thermally stabilizing blue phases and tuning the PBG to fabricate novel devices involve dispersing nanoparticles (NPs) into liquid crystal hosts that exhibit BPs and ChPs. In this study, various nanoparticles, including Al₂O₃, BaTiO₃, C60, and cellulose nanocrystals (CNCs), were dispersed into two liquid crystal hosts, a thermochromic mixture (TLC) and mixtures of cholesteryl nonanoate (CN) with nematic MBBA at different concentrations, to investigate their effects on the thermal stability and tunability of the PBG. The results demonstrate clear evidence of the extension of the BPs' thermal stability and the tuning of their PBG pitch. Notably, BPs exhibited greater thermal stability during cooling than during heating, which is an indication of increased supercooling effects. Furthermore, an increased cooling rate proportionally enhanced the thermal stability of the BPs, likely because of supercooling phenomena. Additionally, although BPs do not require alignment, their selective reflection wass enhanced by introducing planar alignment. Moreover, enhanced tuning of the pitch length was observed when NPs were added to the BPs and ChP compared to the pure LC host. The thermal stability improvements and enhanced tuning of the PBG suggest potential for developing more robust photonic devices, particularly for lasing and smart window applications.

Through extensive Monte Carlo simulations, we study the phase behavior of systems composed of freely jointed, hard-sphere polymers and monomers at different number fractions. This work is inspired by the fact that, despite their similarities in crystallization, the melting point of hard-sphere chains [1] is higher than that of their monomeric counterparts [2].

System configurations are generated, equilibrated, and successively analyzed through the Simu-D software [3]. The equilibration part is primarily based on chain-connectivity-altering [4] and identity-exchange Monte Carlo algorithms, especially designed for mixtures of chains and monomers of the same chemical constitution. The structural identification of the computer-generated system configurations is performed through the characteristic crystallographic element (CCE) norm descriptor [5].

We systematically study how both the packing density and the relative number fraction affect the ability of the systems to crystallize. We further identify the entropic origins of the phase transition and the difference in the local environment between spheres belonging to chains and individual ones. Depending on the simulation conditions, different morphologies are established ranging from predominantly amorphous packings to crystal morphologies of mixed hexagonal close-packed (HCP) and face-centered cubic (FCC) character. Extensions of the present work include the molecular simulation of athermal mixtures based on semi-flexible polymers.

[1] N. C. Karayiannis, K. Foteinopoulou, and Manuel Laso, Phys. Rev. Lett 103, 045703 (2009).

[2] B. J. Alder, and T. E. Wainwright, J. Chem. Phys. 27, 1208 (1957).

[3] M. Herranz et al., Int. J. Mol. Sci. 22, 12464 (2021).

[4] P. M. Ramos, N. C. Karayiannis, and M. Laso, J. Comput. Phys. 375, 918 (2018).

[5] P. M. Ramos et al., Crystals 10, 2073 (2020).

The crystallization and precipitation of calcium carbonate minerals is the subject of intensive research due to the existence of its polymorphic and morphological varieties in geological and biological systems, as well as due to its application both in industrial fields, in particular, in the production of plastics, rubbers, and paper production, and for the creation of biomedical implants and drug delivery systems.

The existence of a new polymorphic modification of calcium carbonate, monoclinic aragonite CaCO₃, has been experimentally discovered [1]. Its crystal structure has been solved and its crystal structure has been discussed. It was found that, unlike the previously known modification, orthorhombic aragonite with cell parameters a = 4.961 Å, b = 7.967 Å, and c = 5.740 Å, the new polymorph belongs to monoclinic symmetry, crystallizes in the space group P2₁/c, and has cell parameters a = 12.732 Å, b = 5.740 Å, c = 9.378 Å, and b =96.91°.

The crystal cell of the new polymorph is formed by three Ca²⁺ cations and three carbonate anions occupying general positions. In the structure, carbonate anions form stacks along the b axis, in which they are arranged in a mutually overlapping manner. The stacks are surrounded by Ca²⁺ cations coordinated by nine oxygen ions. The new monoclinic polymorph has pseudohexagonal symmetry, and this effect is observed only along the b direction of the cell and is absent in the direction of other axes. As in the case of vaterite, the existence of a supercell can be assumed in the structure of the new aragonite, resulting in the high R-factor.

A three-dimensional set of diffraction reflections was obtained for a single crystal at room temperature using a Rigaku OD XtaLAB Synergy-S single-crystal diffractometer on MoK_α radiation (λ = 0.71073 Å). The experimental data were processed using the CrysAlisPro v. 1.171.39.46 software package. The crystal structure was determined based on direct methods using the SHELX [2] software package.

Poly(3-hydroxybutyrate) (PHB) is a storage compound synthesized by the bacteria Azotobacter chroococcum. This semi-crystalline polymer is both biodegradable and biocompatible, making it an ideal compound for tissue engineering materials. The key determining factor of the physical and mechanical properties of materials based on PHB is the distribution of amorphous and crystalline phases. Our research aims to further the understanding of how these phases arise and how they interact with each other. Five PHB samples with molecular masses ranging from 384 kdA to 1095 kdA were used for the current study. Raman spectroscopy and surface-free energy calculations were carried out. From our experiments, it was found that samples had similar surface-free energies. Three different boxes of molecular dynamics simulations representing three different hypotheses were set up: a box according to a classical theory of nucleation, a box with shear flow, and a box with heightened hydrophobic interactions. Our simulations show that a box according to the classical theory of nucleation shows the smallest amount of self-organization while the heightened hydrophobic interactions give rise to configurations that resemble reality the most. From our results, we can conclude that for semi-crystalline biological polymers such as PHB, hydrophobic interactions play a significant role in self-organization during the crystallization process.