A series of novel pentadentate terpyridine-catechol linked ligands were prepared, in which the terpyridine and catechol moieties were linked together by (CH2)(n) chains of different lengths (n = 4-6). Together with 1-methylimidazole, these ligands formed low-spin, six-coordinate Co(In) complexes. Two of the complexes (n = 4, 5) were characterized by X-ray crystallography [n = 4, monoclinic, P2(1)/c, a = 14.957(7) Angstrom, b = 10.585(9) Angstrom, c = 23.033(7) Angstrom, beta = 106.01(3)degrees, V = 3505(3) Angstrom(3), Z = 4, R = 0.063; n = 5, monoclinic, P2(1)/c, a = 8.848(7) Angstrom, b = 15.78(1) Angstrom, c = 25.455(7) Angstrom, beta = 93.90(5)degrees, V = 3544(3) Angstrom(3), Z = 4, R = 0.056], which revealed similar structures around the Co(III)centers but different conformations for the (CH2)(n) linkers. The (CH2)(4) linker showed a straight, symmetric conformation whereas the (CH2)(5) linker showed a curved conformation that allowed the accommodation of one extra CH2 unit, suggesting that the (CH2)(4) linker presents the "best-fit" length for these complexes.