Synthesis and Magnetic Properties of a Dimerized Trinuclear Ni String Complex, [Ni6Cl2(dpa)8](I5)2·0.25I2 (dpa– = 2,2′-Dipyridylamide Anion)

Metal string complexes, linearly aligned transition metal arrays coordinated with the multidentate organic ligands, have gained much attention both in unique electronic/structural properties and in potential applications as conductive molecular nanowires. Here we report on a dimerized NiII trinuclear complex, [Ni6Cl2(dpa)8]­(I5)2·​0.25I2 (dpa– = 2,2′-dipyridyl­amide anion). X-ray structural analysis revealed that two trinuclear moieties are bridged by a Cl anion to form a dimerized string structure. This is the first example of two Ni string complexes that are connected. In the electronic absorption and Raman spectra, characteristic absorption bands and a vibration mode based on the dimer string structure were observed. In the solid state, dimer complexes align in one dimension in an MMMX­MMMX (M = metal, X = halogen) manner, leading to the intra- and interdimer antiferromagnetic interactions.