The high-resolution solution structure and dynamics of a cofacially aligned porphyrin−phenylene−quinone compound have been determined using 1H NMR spectroscopy and simulated annealing calculations. Members of this class of π-stacked assemblies feature a 1,8-naphthyl pillaring motif that enforces sub van der Waals interplanar separations between juxtaposed porphyryl, aromatic bridge, and quinonyl components of the donor−spacer−acceptor compound; this structural motif gives rise to a comprehensive set of structurally significant NOE signatures that can be used as constraints in quantitative structural calculations. Examination of such data using ab initio simulated annealing analytical methods shows that 5-8‘-(4‘ ‘-8‘ ‘‘-(2‘ ‘‘ ‘,5‘ ‘‘-benzoquinonyl)-1‘ ‘‘-naphthyl-1‘ ‘-phenyl)-1‘-naphthyl-10,20-diphenylporphyrin displays an unusual degree of conformational homogeneity in the condensed phase, and represents a rare example where such an analysis determines unequivocally a single unique structure in solution.