Series of Novel 3D Heterometallic Frameworks Based on the Co(II) Coordination Chains and Ln(III) Coordination Layers

A family of novel Co­(II)–Ln­(III) heterometallic coordination polymers [Ln₂Co­(tia)₄(H₂O)₄]_<b>∞</b> (tia^2– = 5-(1<i>H</i>-1,2,3-triazol-1-yl) isophthalate, Ln = La <b>1</b>, Ce <b>2</b>, Pr <b>3</b>, Nd <b>4</b>, Sm <b>5</b>, Eu <b>6</b>, Gd <b>7</b>, Tb <b>8</b>, Dy <b>9</b>) have been synthesized through in situ ligand transformation reactions, in which 5-(4-carboxy-1<i>H</i>-1,2,3-triazol-1-yl) isophthalic acid (H₃ctia) undergoes decarboxylation and double deprotonation to tia^2–. X-ray structural analysis reveals that compounds <b>1</b>–<b>9</b> are isomorphous. The heterometallic Ln³⁺ and Co²⁺ ions are connected by the dianionic linker (tia^2–) to form unique 3D heterometallic frameworks. Moreover, we have systematically investigated the magnetic behaviors and fluorescent properties of these compounds. The out-of-phase ac signals observed for <b>9</b> suggest slow magnetization relaxation, which is unusual in 3D coordination polymers, especially in 3D heterometallic frameworks. In NIR regions, complexes <b>3</b>, <b>4</b>, <b>5</b>, and <b>9</b> show the characteristic luminescence of the corresponding Ln­(III ions