Synthesis, characterization, and spectroscopy of 4,7,12,15-[2.2]paracyclophane containing donor and acceptor groups: impact of substitution patterns on through-space charge transfer

This paper reports the synthesis of 4,7,12,15-tetra(4'-dihexylaminostyryl)2.2]paracyclophane (1), 4-(4'-dihexylaminostyryl)-7,12,15-tri(4' '-nitrostyryl)2.2]paracyclophane (2), 4,7-bis(4'-dihexylaminostyryl)-12,15-bis(4' '-nitrostyryl)-2.2]paracyclophane (3), 4,7,12-tris(4'-dihexylaminostyryl)-15-(4' '-nitrostyryl)2.2]paracyclophane (4), 4,15-bis(4'-dihexylaminostyryl)-7,12-bis(4' '-nitrostyryl)2.2]paracyclophane (5), and 4,12-bis(4'-dihexylaminostyryl)-7,15-bis(4' '-nitrostyryl)2.2]paracyclophane (6). These molecules represent different combinations of bringing together distyrylbenzene chromophores containing donor and acceptor groups across a 2.2]paracyclophane (pCp) bridge. X-ray diffraction studies show that the lattice arrangements of 1 and 3 are considerably different from those of the parent chromophores 1,4-bis(4'dihexylaminostyryl)benzene (DD) and 1,4-di(4'-nitrostyryl)benzene (AA). Differences are brought about by the constraint by the pCp bridge and by virtue of chirality in the "paired" species. The absorption and emission spectra of 1-6 are also presented. Clear evidence of delocalization across the pCp structure is observed. Further, in the case of 2, 3, and 4, emission from the second excited state takes place.