*2.3. Quantum Theory of Atoms in Molecules (QTAIM)*

Quantum theory of atoms in molecules (QTAIM) was applied to X-ray structures as well as to structures optimized at the *ω*B97XD/def2-TZVP level of theory [85,86] using the Gaussian 16 Rev. C.0.1 suite of programs [87]. The wavefunctions for further elec-

tronic structure analysis were obtained with the same computational setup. This part of the investigations was only performed for the gas phase models. The QTAIM analysis was performed with the assistance of the MultiWFN 3.8 program [88,89]. The graphical presentation of the obtained results was prepared using the VMD 1.9.3 program [81].
