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

2015-06-26T13:44:04Z (GMT) by Hongzhen Xie Guanzhong Lu
<div><p>Four lanthanide complexes with two tri-protonated hexacarboxylic acids [1,2,3,4,5,6-cyclohexane-hexacarboxylic acid (H<sub>6</sub>chhc) and mellitic acid (H<sub>6</sub>Mel)], [Pr(H<sub>3</sub>chhc)(DMF)<sub>3</sub>(H<sub>2</sub>O)]·H<sub>2</sub>O (<b>1</b>), Nd(H<sub>3</sub>chhc)(DMF)<sub>3</sub> (<b>2</b>), [Er(H<sub>2</sub>O)<sub>8</sub>]·(H<sub>3</sub>Mel)·9(H<sub>2</sub>O) (<b>3</b>), and [Yb(H<sub>2</sub>O)<sub>8</sub>]·(H<sub>3</sub>Mel)·8.5(H<sub>2</sub>O) (<b>4</b>), 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 <b>1</b> and <b>2</b> are made up of a (4<sup>4</sup>, 6<sup>2</sup>) 2-D network extended infinitely parallel to the (1 0 0) plane. The H<sub>3</sub>chhc<sup>3−</sup> anions assume a <i>cis</i>-<i>e,a,e,a,e,a</i>-conformation with the central ring in chair-shaped configuration. In <b>3</b> and <b>4</b>, the H<sub>3</sub>Mel<sup>3−</sup> as counter ions are interconnected by hydrogen bonds to form 2-D organic supramolecular layers. The coordination modes and abilities of H<sub>6</sub>chhc and mellitic acid are discussed and compared. The luminescences of <b>1–4</b> have been investigated.</p></div>