AUTHOR=Wei Wei , Ren Wenhui , Jian Wei , Xia Baohui , Zhang Hongxing , Bai Fu-Quan , Li Wei 

TITLE=Stability, Aromaticity, and Photophysical Behaviors of Macrocyclic Molecules: A Theoretical Analysis

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 8 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.00776

DOI=10.3389/fchem.2020.00776

ISSN=2296-2646

ABSTRACT=The macrocyclic molecules with terthiophene isomers unit exhibit intriguing properties in terms of aromaticity, stability, and absorption. In this work, we theoretically designed of a series of macrocyclic molecules featured with terthiophene (TTH) and dithienothiophene (DTT) π-conjugated building units which are used to permute pyrrole unit in porphyrin skeleton. Density functional theory (DFT) and time-dependent DFT (TD-DFT) methods are used to evaluate the performance of the designed molecules. Our simulations show that molecules 1-3 exhibit excellent optoelectronic performance. Specifically, the molecule with the DTT unit is more stable than the one with TTH unit in terms of aromaticity and aromatic stabilization energy. This is because DTT unit enhances the coplanarity of the molecular, facilitating electronic communication. Calculation of vertical electronic excitations suggests the absorption feature of these molecules is mainly contributed by the electronic excitations of HOMO→LUMO+1 and HOMO-1→LUMO. Judging from the key parameters determining the overall performance, 3 stands out due to its good planarity, large HOMO-LUMO gap, and stronge aromaticity among all molecules. Interestingly, molecule 1 has the current density flow distributes around the outer section of TTH unit; in contrast, molecule 3 with DTT unit has the current density flow locates at the inner section of DTT, which is beneficial for stability and aromaticity. Second order perturbation energies are calculated to rationalize this observation. We expect that these research results can provide valuable insights into the rational design of novel molecular materials for a variety of applications.