TY  - JOUR
A1  - Titov, Evgenii
T1  - On the low-lying electronically excited states of azobenzene dimers
BT  - Transition density matrix analysis
JF  - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2  - Azobenzene-containing molecules may associate with each other in systems such as self-assembled monolayers or micelles. The interaction between azobenzene units leads to a formation of exciton states in these molecular assemblies. Apart from local excitations of monomers, the electronic transitions to the exciton states may involve charge transfer excitations. Here, we perform quantum chemical calculations and apply transition density matrix analysis to quantify local and charge transfer contributions to the lowest electronic transitions in azobenzene dimers of various arrangements. We find that the transitions to the lowest exciton states of the considered dimers are dominated by local excitations, but charge transfer contributions become sizable for some of the lowest pi pi* electronic transitions in stacked and slip-stacked dimers at short intermolecular distances. In addition, we assess different ways to partition the transition density matrix between fragments. In particular, we find that the inclusion of the atomic orbital overlap has a pronounced effect on quantifying charge transfer contributions if a large basis set is used.
KW  - azobenzene
KW  - dimer
KW  - transition density matrix
KW  - exciton
KW  - charge transfer
KW  - excited states
KW  - TD-DFT
KW  - ADC(2)
Y1  - 2021
U6  - https://doi.org/10.3390/molecules26144245
SN  - 1420-3049
VL  - 26
IS  - 14
PB  - MDPI
CY  - Basel
ER  -