Synthesis, structure, and urease inhibitory activities of three binuclear copper(II) complexes with protocatechuic acid derivative

<div><p>Three Cu(II) complexes, [Cu<sup>II</sup><sub>2</sub>(L<sub>1</sub>)<sub>4</sub>(L<sub>2</sub>)<sub>2</sub>] (<b>1</b>), [Cu<sup>II</sup><sub>2</sub>(L<sub>1</sub>)<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>]·HL (<b>2</b>), and [Cu<sup>II</sup><sub>2</sub>(L<sub>1</sub>)<sub>3</sub>(L<sub>3</sub>)<sub>2</sub>]ClO<sub>4</sub> (<b>3</b>), with a ligand derived from protocatechuic acid (HL<sub>1</sub> = C<sub>9</sub>H<sub>8</sub>O<sub>4</sub>=2,3-dihydrobenzo[<i>b</i>][1,4]dioxine-6-carboxylic acid, L<sub>2</sub> = C<sub>7</sub>H<sub>9</sub>N=<i>o</i>-toluidine, L<sub>3</sub> = C<sub>6</sub>H<sub>16</sub>N<sub>2</sub>=N,N-diethylethylenediamine) were synthesized and characterized by C, H, and N elemental analysis and single-crystal X-ray diffraction, which revealed that the three complexes have similar binuclear structures. Complexes <b>1</b> and <b>3</b> crystallized in triclinic space group <i>P</i>-<i>1</i> and <b>2</b> in orthorhombic space group <i>P2</i><sub><i>1</i></sub><i>2</i><sub><i>1</i></sub><i>2</i><sub><i>1</i></sub>. The urease inhibitory activities of the three complexes were tested. All three complexes showed strong inhibitory activity against <i>jack bean</i> urease with an IC<sub>50</sub> value of 6.8, 5.5, and 3.5 μM compared with the acetohydroxamic acid (IC<sub>50</sub> = 7.5 μM), which was a positive control.</p></div>