Syntheses and crystal structures of four lanthanide complexes based on two tri-protonated hexacarboxylic acids of 1,2,3,4,5,6-cyclohexane-hexacarboxylic acid and mellitic acid
Four lanthanide complexes with two tri-protonated hexacarboxylic acids [1,2,3,4,5,6-cyclohexane-hexacarboxylic acid (H6chhc) and mellitic acid (H6Mel)], [Pr(H3chhc)(DMF)3(H2O)]·H2O (1), Nd(H3chhc)(DMF)3 (2), [Er(H2O)8]·(H3Mel)·9(H2O) (3), and [Yb(H2O)8]·(H3Mel)·8.5(H2O) (4), have been synthesized in solution at room temperature and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal structures of 1 and 2 are made up of a (44, 62) 2-D network extended infinitely parallel to the (1 0 0) plane. The H3chhc3− anions assume a cis-e,a,e,a,e,a-conformation with the central ring in chair-shaped configuration. In 3 and 4, the H3Mel3− as counter ions are interconnected by hydrogen bonds to form 2-D organic supramolecular layers. The coordination modes and abilities of H6chhc and mellitic acid are discussed and compared. The luminescences of 1–4 have been investigated.