μ‐Oxo Dimers of Silicon Porphyrazines and Their Interlayer Interactions

Abstract μ‐Oxo dimers of octaaryl‐substituted silicon porphyrazines (SiPzs) were synthesized for the first time. The steric congestion due to the peripheral aryl groups attenuated the rotation of the SiPz units around the Si–O–Si axis, resulting in the fixed D 4 symmetric conformations with the torsion angle of ∼23° at room temperature or lower, which were unambiguously elucidated by the single‐crystal X‐ray diffraction analysis and variable‐temperature NMR studies. The interlayer molecular orbital interactions between the stacked SiPz units perturbed UV/vis absorption spectra and electrochemical properties of the dimers. In addition, the hetero‐type dimer, bearing electron‐donating and electron‐withdrawing aryl‐substituents on each SiPz unit, showed a large two‐photon absorption cross‐section based on the reverse saturable absorption mechanism mediated by the intramolecular charge transfer interactions.