Quadrupolar interactions of porphyrin bearing two pentafluorophenylethynyl terminals (1) drove the formation of a successive one‐dimensional staircase structure, i.e., J‐aggregates, to yield millimeter‐length needles with a single‐crystalline character in methylcyclohexane solution. In contrast, π‐stacked interactions of porphyrin bearing two nonfluorinated phenyl terminals (2) formed no aggregates in solution. A spin‐cast film of 1 also showed bathochromic shift of the Soret and Q bands, indicating the formation of J‐aggregates. The molecular arrangement of the J‐aggregates was revealed by microbeam glazing‐incidence wide‐angle X‐ray diffraction (GIWAXD), and was in good agreement with the optimized structure generated by density functional theory (DFT) calculations.

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