Syntheses and 1H NMR spectroscopy of rigid, cofacially aligned, porphyrin-bridge-quinone systems in which the interplanar separations between the porphyrin, aromatic bridge, and quinone are less than the sum of their respective van der Waals radii

Unusually rigid pi-stacked porphyrin-spacer-quinone systems have been synthesized using an approach that enables extensive control over the nature of electronic interactions between donor, aromatic spacer, and acceptor. This new class of porphyrin-based structures is distinct from related assemblies designed to probe electronic interactions between cofacial pi-stacked, aromatics: the donor (D), spacer (Sp), and acceptor (A) components of the assembly are held fixed at sub van der Waals contact distances, restricting severely the range of dynamical processes that modulate typically the magnitude of inter-ring separation and the extent of the lateral shift between juxtaposed aromatic units in the condensed phase. NMR spectroscopic studies demonstrate that these structures manifest disparate shielding environments which distribute uniformly the aromatic H-1 resonances for these diamagnetic D-Sp-A compounds over spectral windows that exceed 9.0 ppm.