Ab initio molecular dynamics study of the structure and supramolecular organization in mesogenic lanthanum(III) complexes with β‐diketones and Lewis bases

Abstract

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.

Quantum-chemical study of luminescence efficiency and excited state structures of some mesogenic europium(III) complexes with β­diketones and Lewis bases

“…Furthermore, the more rigid geometry of Phen ligand compared to Bpy 17-17 increases the emission efficiency of complexes with Phen by minimizing the contribution of nonradiative deactivation to the energy transfer process. At the same time, complexes 1 and 3 with Bpy 17-17 have the highest anisotropy parameters above the LC properties demonstration threshold [8,9,11,27] due to alkyl substituents in Lewis base and βdiketones.…”

“…Ligands with long alkyl substituents increase this ratio for LC Ln(III) complexes in comparison with other Ln(III) complexes to maximum value of 3.5. [8,9,11,27] According to our earlier studies and calculations, [8,9,11,27] the minimum value of the anisotropy parameter at which mesogenic Ln(III) complexes have LC properties equals 2.5. In this study, the anisotropy of geometry equals According to experimental studies of these compounds, [9,30,56] only complexes with Bpy One of the pioneer studies of mesogenic rare-earth complexes with Schiff base ligands [57] showed that the chain length in ligands has a little influence on the first coordination sphere of Ln(III) ion but determines the packing of complexes in the crystal structure.…”

“…The geometry optimization of mesogenic Eu(III) complexes in the ground state was performed by the DFT method using the Prirоdа 06 software. [28,29] According to our previous studies [8,9,11,27,30] we used generalized gradient approximation with the Perdew-Burke-Ernzerhof (PBЕ) exchange-correlation functional. [31] Relativistic basis sets rL11 for Eu(III) and rL1 for other atoms within the scalar relativistic approximation were used.…”

“…The presence of a heavy Eu(III) ion and a large number of atoms results in a high computational costs especially when optimizing the geometry of excited states. The geometry optimization of eight isomers for each of the studied Eu(III) complexes with different arrangement of β-diketones relative to the plane formed by the Eu(III) ion and the Lewis base [8,9,11,27] was made. According to the calculations, the isomers with the crosswise arrangement of βdiketones have the lowest energy.…”

“…In our recent work ab initio molecular dynamics together with DFT were used to study inter-and intramolecular interactions in mesophases, the supramolecular organization and LC behavior of La(III) complexes. [27] In this work, we studied mesogenic Eu(III) complexes that show specific LC behavior, low viscosity smectic and nematic mesophases in a wide temperature range in combination with unique photophysical and magnetic properties. [7][8][9]11] We optimized the geometry of complexes in the ground and triplet excited states.…”