Consecutive Planar and Spherical Aromatic Arrays: Shielding Cone Behavior in Multiple Planar-Spherical Aromatics from Phenyl and Carboranes Motifs

The design and rational formation of extended molecular materials require a delicate selection of stable and persistent building blocks, favoring further controlled modification of the overall properties. In this report, the behavior involving five consecutive aromatic building units alternating both planar (2D) and spherical (3D) motifs obtained in 1,4-bis-(2′-phenyl-ortho-carboran-1′-yl)-benzene (1) and its fluorinated counterpart with a 2,3,5,6-tetrafluoro (2) 1,4-bridge is accounted for. These results expose the orientation-dependent character of the aromatic 2D units, enabling a shielding cone under a perpendicular external field, contrasting to the aromatic 3D units, which is enabled from different orientations, leading to an enhancement of the shielding effect at common regions. Upon reduction to −2 and −4 charged species, the phenyl rings are shifted from a conjugated to a quinoidal character, decreasing the aromaticity at such fragments selectively. Interestingly, from neutral to charged species, the carborane cages (B₁₀C₂) evolve from 2n + 2 to 2n + 3 skeletal electrons, leading to marked elongation of the C─C bonds, retaining spherical aromatic properties. Hence, the alternate connection of planar and spherical aromatic units favors envisaging further cluster-phenyl-based extended networks, where aromatic units retain a well-defined structure that can be modified reversibly by electrochemical methods.