Abstract

Novel sandwich-type doubledecker and tripledecker cerium complexes, bis[5,15-bis(3,4-dialkoxyphenyl)porphyrinato]cerium(IV) (2: [(C_nO)₄BPP]₂Ce; n = 14), bis[5,10,15,20-tetrakis(3,4-dialkoxyphenyl)porphyrinato]cerium(IV) (5: [(C_nO)₈TPP]₂Ce; n = 8,10,12,14,16,18), and tris[5,10,15,20-tetrakis(3,4-dialkoxyphenyl)porphyrinato]cerium(IV) (6: [(C_nO)₈TPP]₃Ce₂; n = 10), have been synthesized by using the corresponding metal free derivatives, 5,15-bis(3,4-dialkoxyphenyl)porphyrin (1: (C_nO)₄BPPH₂) and 5,10,15,20-tetrakis[3,4-bis(octadecyloxy)phenyl]porphyrins (4: (C_nO)₈TPPH₂) which were previously reported to show a discotic lamellar(D_L) mesophase. The mesophase structures of all these sandwich-type cerium complexes have been characterized in detail by microscopic observation, DSC measurements and temperature-dependent X-ray diffraction studies. We have investigated the critical molecular structure changing from lamellar mesophase-showing porphyrins to columnar mesophase-showing ones. We found that these sandwich-type multideckers may exhibit a columnar mesophase, when the central core is substituted by more than twelve alkoxy chains.