Simulation technique for the study of the structural properties and supramolecular organization of mesogenic lanthanum(III) complexes with β‐diketones and Lewis bases with the combination of high‐level quantum chemical methods and ab initio molecular dynamics was proposed and approved. Three representatives of La(III) complexes with ligands of various nature were investigated and relations between their structural properties and liquid‐crystalline (LC) behavior were studied. It has been shown that the structure of β‐diketones and their substitutes mostly define the number and type of LC mesophases. The Lewis base ligand generally determines the appearance of LC properties. Estimated anisotropy of geometry values for two complexes were found above the known threshold value defining the presence of LC phases. Thus, these complexes are expected to exhibit LC properties, while the third complex not, which is in agreement with the experimental data. We also used Voronoi–Dirichlet polyhedral (VDP) approach to analyze the first coordination sphere of the La(III) complexes. Calculated parameters of VDP helped to evaluate the forces of intermolecular interactions. The unitless normalized second moment of inertia for three exemplary La(III) complexes was found to correlate with the number of the LC phases of the corresponding complexes.
Chitosan or its derivatives exhibit lyotropic liquid crystalline mesophases under certain conditions due to its semi-rigid structures. This work describes the development of chitosan-based biocompatible systems that include new components: lactic acid and non-ionic surfactants. Polarized optical microscopy studies revealed that these systems are capable of forming gels or lyotropic liquid crystals (LLCs) in a certain range of chitosan and lactic acid concentrations. According to the viscosity studies, the rheological flow of the LLCs can be accurately described by the Casson flow model. The intermolecular interactions of the LLC components were studied by FTIR spectroscopy. According to the FTIR data, hydrogen bonding is supposed to be responsible for the formation of the LLCs. In the studied systems, this LLC complex exists as the [ChitH+·CH3-CH(OH)-COO−] ion pair. The studied gel and LLCs were shown to possess the most prolonged release capabilities for riboflavin among similar binary LLC systems. The supramolecular organization and rheological characteristics of the studied chitosan-based systems were found to affect the release of riboflavin.
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