Keywords: Bioinorganic chemistry / Manganese / DNA cleavage / Artificial nucleases / Cooperative effects / Magnetic propertiesThe potential synergy between metal centers makes multinuclear metal complexes promising candidates for artificial nucleases. However, few multinuclear mimics have shown higher DNA cleavage efficiencies than their mononuclear analogues. By using 1,8-naphthalene dicarboxylic acid (1,8-H 2 ndc) and 1,10-phenanthroline (phen) ligands, one mononuclear complex [Mn(1,8-ndc)(phen) 2 (H 2 O)]·CH 3 OH·2H 2 O (1), two dinuclear complexes [Mn(1,8-Hndc)(phen) 2 ] 2 ·2ClO 4 · 4H 2 O (2) and [Mn(1,8-ndc)(phen)(H 2 O) 2 ] 2 ·CH 3 OH·H 2 O (3), and one hexanuclear complex [Mn(1,8-ndc)(phen)(H 2 O) 2 ] 6 · 11H 2 O (4) were synthesized and structurally characterized by single-crystal X-ray analysis. Complexes 2-4 have closedring structures bridged by 1,8-ndc ligands that adopt a peculiar μ 2 -η 1 :η 1 bridging mode, which has never been reported before. Circular dichroism and fluorescence studies show [a]