Periodic Reporting for period 1 - MulArEffect (Theoretical description of the multifaceted aromaticity and resonance effects in the ground- and excited-state molecular systems)
Reporting period: 2018-10-01 to 2020-09-30
In this project we propose a profound paradigmatic change of the concept of aromaticity quantification to reveal its true colors and unearth its real predictive power. The long-term goal of this project is to understand how aromaticity and different resonance effects determine the physicochemical properties in such systems. In the first goal, we developed a novel computational method called the electron density of delocalized bonds (EDDB) that provides both a detailed description of local aromaticity of selected molecular fragments as well as the bird's-eye view on the global aromaticity of nanoscopic-size molecules and assemblies at a reasonable computational cost. The second research goal of the proposal was to use the EDDB method to gain insights into the mechanisms of the resonance-driven phenomena in the multifaceted aromatics that are instrumental in the design of new catalysts, spin-bearing materials, organic field-effect transistors, and many other.
The newly proposed method and the released software was utilized to quantitatively assess the effect of d-orbital conjugation in metallacycle of different size, topology, and type of conjugation (Hückel, Craig-Möbius, hybrid, etc.). Also, the world’s first Baird aromatic all-metal clusters were discovered based on the predictions made by the EDDB method. Moreover, the sophisticated techniques of the EDDB-based partitioning of the molecular electron densities were used to better understand the origins of the so-called adaptive aromaticity in metallapentalenes. Next, we assessed and validated the newly proposed EDDB-based spin-density decomposition scheme for the M10A-type systems, which can be widely applied in π-conjugated spin-bearing materials and thus a correct understanding of their electronic structures is of high importance. Also, we used the EDDB method to deepen the understanding of how aromaticity can be utilized as a feasible design strategy to manipulate the excited state energy levels in CIBA-type systems (which are excellent candidates for singlet-fission materials). Finally, we investigated the interplay between pyrrolic and macrocyclic aromaticity in porphyrins and phthalocyanines determining their conformational flexibility and spectroscopic properties. Interestingly, the results obtained using the EDDB method revealed the close relationship between the frequency shifts observed in the AFM experiment and the pyrrolic and annulenic aromaticities/olefinicities in the macro- and polycyclic aromatic compounds.