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

Two novel stable β-tetraethylporphycenes (TEPo), namely trans-TEPo (1T) and its unsymmetric isomer cis-TEPo (1C) were synthesized via reductive McMurry coupling of an unsymmetric bipyrrole dialdehyde and isolated through recrystallizations. Both isomers show interesting photophysical properties. Their corresponding dibromo derivatives obtained through bromination of a mixture of 1C and 1T, however could not be separated in pure forms. Interestingly, they 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 two dimensional (2D) arrays in solid state.