Mono-, di-, and trinuclear phosphonate oxygen-bridged copper(II) complexes: syntheses, structures, and properties

<p>Reactions of copper salts, zoledronic acid, and 2,2′-bipyridine/1,10-phenanthroline in aqueous ethanolic solutions afforded four phosphonate oxygen-bridged copper complexes, Cu(bipy)(H<sub>4</sub>zdn)(HSO<sub>4</sub>) (<b>1</b>), [Cu<sub>2</sub>(bipy)<sub>2</sub>(H<sub>2</sub>zdn)(H<sub>2</sub>O)(Cl)]·4H<sub>2</sub>O (<b>2</b>), [Cu<sub>2</sub>(phen)<sub>2</sub>(H<sub>2</sub>zdn)(H<sub>2</sub>O)(Cl)]·2.5H<sub>2</sub>O (<b>3</b>), and [Cu<sub>3</sub>(bipy)<sub>3</sub>(H<sub>4</sub>zdn)(H<sub>2</sub>zdn)(SO<sub>4</sub>)]·5H<sub>2</sub>O (<b>4</b>) (H<sub>5</sub>zdn = zoledronic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The copper centers of <b>1</b>–<b>4</b> have square pyramidal coordination geometries. The Cu(II) ions are coordinated to bipy/phen, zoledronate, and HSO<sub>4</sub><sup>−</sup>/Cl<sup>−</sup> forming mononuclear units for <b>1</b>, dinuclear for <b>2</b> and <b>3</b>, and trinuclear for <b>4</b>. These building units are further extended into 3-D supramolecular networks via multiple hydrogen bond interactions. Temperature-dependent magnetic properties of <b>2</b> and <b>4</b> suggest weak antiferromagnetic coupling (<i>J</i> = −4.53(8) cm<sup>−1</sup> for <b>2</b>, <i>J</i> = −1.69(4) cm<sup>−1</sup> for <b>4</b>). The antitumor activity of <b>2</b> was evaluated against the human lung cancer cell line and indicates effective time- and dose-dependent cytotoxic effects.</p>