Abstract
The complexation of (3aR,7aR)-N-(3,5-bis(trifluoromethyl)phenyl)octahydro-2H-benzo[d]imidazol-2-imine (BTI), as a guest, to ethane-bridged bis(zinc octaethylporphyrin), bis(ZnOEP),as a host, has been studied by means of ultraviolet-visible (UV-Vis) and circular dichroism (CD)absorption spectroscopies, single crystal X-ray diffraction, and computational simulation. The forma-tion of 1:2 host-guest complex was established by X-ray diffraction and UV-Vis titration studies. Twoguest BTI molecules are located at the opposite sides of two porphyrin subunits of bis(ZnOEP) host,which is resting in theanti-conformation. The complexation of BTI molecules proceed via coordina-tion of the imine nitrogens to the zinc ions of each porphyrin subunit of the host. Such supramolecularorganization of the complex results in a screw arrangement of the two porphyrin subunits, inducinga strong CD signal in the Soret (B) band region. The corresponding DFT computational studies are ina good agreement with the experimental results and prove the presence of 1:2 host-guest complex asthe major component in the solution (97.7%), but its optimized geometry differs from that observedin the solid-state. The UV-Vis and CD spectra simulated by using the solution-state geometry andthe TD-DFT/ωB97X-D/cc-pVDZ + SMD (CH2Cl2) level of theory reproduced the experimentallyobtained UV-Vis and CD spectra and confirmed the difference between the solid-state and solutionstructures. Moreover, it was shown that CD spectrum is very sensitive to the spatial arrangement ofporphyrin subunits.