Controlling the Transmission of Stereochemical Information through Space in Terphenyl-Edged Fe4L6 Cages

A series of terphenyl-edged Fe4L6 cages were synthesized from substituted 4,4 ''-diamino-p-terphenyls, 2-formylpyridine, and iron(II). For the parent diaminoterphenyl, all three possible diastereomers, with T, S-4, and C-3 point symmetries, were formed in nearly equal amounts, as determined by H-1 and C-13 NMR. When 2,2 ''-dimethylterphenylenediamine was used, the T-symmetry diastereomer was observed to predominate. The use of 2',3',5',6'-tetramethylterphenylenediamine generated predominantly the S-4 cage diastereomer, whereas 2',5'-dimethylterphenylenediamine produced the C-3-symmetric cage to a greater degree than the other two diastereomers. The factors contributing to the transfer of chiral information between metal vertices were analyzed, and the general principles underlying the delicately balanced thermodynamics were determined.