New manganese-scaffolded organic triple-deckers based on quinoxaline, pyrazine and pyrimidine cores

Abstract

The thermolytic coupling of Ph₂CN₂ and (t-Bu)(Ph)CN₂ with doubly cyclomanganated 2,5-diphenylpyrazine and 4,6-diphenylpyrimidine afforded substantial amounts of new triple decker compounds of either C_i and C₂ symmetry respectively containing, in both series, two η³-bonded Mn(CO)₃ fragments which intervene as scaffolds sustaining the helical non-conjugated triaryl backbone. The molecular structures of two pyrazine derivatives show a typical non-parallel stacking of the aromatic rings and the encapsulation of the central pyrazyl fragment with interplanar centroid-to-centroid distances of ca. 3.5 Å. The stacking of the aromatics in the triple-decker pyrimidine derivatives has been assessed by ¹H NMR experiments at low temperature. All the triple-decker-type compounds are electroactive. Pyrimidine triple-deckers can reversibly be electrochemically reduced to the corresponding anions.