Unsymmetrical Bipyrrole-Derived β-Tetraalkylporphycenes and C–H···Br–C Interaction Induced 2D Arrays of the 2:1 Supramolecular Sandwich Complex of Their cis-/trans-Dibromo Isomers

Abstract

Two novel stable β-tetraethylporphycenes (TEPos), namely, trans-TEPo (1T) and its unsymmetrical isomer cis-TEPo (1C), were synthesized by reductive McMurry coupling of an unsymmetrical bipyrrole dialdehyde and were isolated through recrystallization. Both isomers showed interesting photophysical properties. Their corresponding dibromo derivatives obtained through bromination of a mixture of 1C and 1T, however, could not be separated in pure form. Interestingly, they were found to form an unprecedented 2:1 supramolecular sandwich complex through π–π stacking interactions, and in addition, only strong C–H···Br–C interactions among the oppositely oriented cis isomers led to the formation of 2D arrays in the solid state.