Effect of pH on the self-assembly of three Cd(II) coordination compounds containing 5-(4-pyridyl)tetrazole: syntheses, structures, and properties

<div><p>Hydrothermal reactions of CdSO₄, 4-cyanopyridine, and sodium azide yield three metal coordination compounds via controlling the pH, [Cd₂(4-ptz)(SO₄)(OH)(H₂O)₂](H₂O) (<b>1</b>) [Cd₂(4-ptz)(SO₄)(OH)(H₂O)]_n (<b>2</b>), and known [Cd₂(4-ptz)₂(H₂O)₄](H₂O)₂ (<b>3</b>) (4-ptz = 5-(4-pyridyl)tetrazole). The <i>in situ</i> [2 + 3] cycloaddition reaction of nitrile and azide in the presence of Cd(II) produces the multidentate 4-ptz in these compounds. X-ray diffraction results indicate that metal centers in <b>1</b> are linked by 4-ptz^–, , and OH⁻ in their respective <i>μ</i>₅-, <i>μ</i>₂-, <i>μ</i>₃-bridging modes, forming a 3-D coordination polymer. For <b>2</b>, although the same raw materials are used, the component anions are linked to Cd(II) centers in completely different ways, i.e. for 4-ptz⁻ in <i>μ</i>₃−, in <i>μ</i>₅-, and OH⁻ in <i>μ</i>₃-bridging modes, forming another 3-D coordination network. Thermal stabilities and photoluminescent properties of <b>1</b> and <b>2</b> have also been investigated.</p>