Chiral Self-assembly of Zinc and Magnesium Porphyrins with Enantiopure Cyclohexanohemicucurbiturils in Solution and in Solid-State

Chiral self-assembled supramolecular networks have high potential for the synthesis of new chiral materials. We present here the highly predictable self-assembly of metalloporphyrins with chiral cyclohexanohemicucurbit[n]urils (cycHC[6] and cycHC[8]), where the chirality of cycHCs is imprinted onto achiral porphyrins in both solution and the solid-phase. Diverse coordination environments, influenced by solvents and porphyrin substituents, led to the characterization of 32 novel complexes by single crystal X-ray diffraction. All complexes are based on metal-urea coordination centers, while their structural variability—ranging from discrete complexes to 1D-, helical 1D-, and 2D-square-grid coordination polymers—is governed by the shape and binding strength of cycHCs, as well as induced dipole - interactions of the porphyrins. In solution, the binding strength of the complexes varied significantly, from 690 to 1,840,000 M⁻¹, while the g-factors of electronic circular dichroism (ECD) remained consistent across porphyrins. Solid-state measurements revealed a ten-fold increase in the induced ECD intensity in the Soret band region compared to solution, attributed to chiral aggregation and interporphyrin exciton coupling. Vibrational circular dichroism studies demonstrated chirality induction in the infrared absorbance range, with the g-factor of cycHC[6] carbonyl signals increasing ten-fold upon complexation. This work highlights the robustness of hemicucurbituril–metalloporphyrin chiral supramolecular systems for the development of advanced sensing applications.