Synthesis and Optical Property Modulation of Substituted [2.2]Paracylophanes through Through‐Space Conjugation

Abstract

4,16‐para‐substituted [2.2]paracylophane with naphthalene (PCP⎼NAP), anthracene (PCP⎼ANTH), and tetraphenylethylene (PCP⎼TPE), as new through‐space conjugated dimers, were prepared by the Suzuki–Miyaura cross‐coupling reaction of 4,16‐diboryl[2.2]paracyclophane and the corresponding bromo derivative using Pd(PPh3)4 as a catalyst and KOH as a base. The synthesized compounds were fully characterized by NMR and HR‐MS, and their photophysical and electrochemical properties were studied. The photoluminescence quantum yield of PCP⎼NAP, PCP⎼ANTH were determined to be 0.21, 0.50 and for PCP⎼TPE in aggregated state 0.31, respectively. PCP⎼TPE exhibited aggregation‐induced emission characteristics when the water fraction was greater than 50% in THF/water mixtures. PCP⎼ANTH and PCP⎼TPE were also characterized by X‐ray crystallography, and single crystals of PCP⎼ANTH were obtained from the centrosymmetric monoclinic space group C2/c. A single crystal of PCP⎼TPE crystallizes in the centrosymmetric triclinic space group P⎼1, with one molecule residing at the inversion center. The observed properties of these π‐stacked dimers were compared with respect to through‐space conjugation and conjugation length in the structure.