Two Mn II coordination polymers based on the flexible bis(benzimidazole) and dicarboxylic acids, namely, [Mn(L1)(bpdc)(H 2 O) 0.5 ] n (1) and [Mn(L2)(Htbi) 2 ] n (2) [L1 = 1,4bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, H 2 bpdc = 4,4Ј-biphenyldicarboxylic acid, L2 = 1,4-bis(5,6-dimethylbenzimidazole)butane, H 2 tbi = 5-tert-butyl isophthalic acid] were hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, as well as single-crystal X-ray diffraction. Both of the complexes crys-* Dr. G. Y. Dong Fax: +86-0315-2592170 E-Mail: tsdgying@126.com [a] College