Synthesis and Crystal Structure of a New Dinuclear Holmium(III) Complex with a Bulky Anthracene-Based Carboxylate Ligand

Abstract  

The reaction of Ho(NO₃)₃ with the bulky anthracene-9-carboxylic acid (HL) and 1,10-phenanthroline (phen) in the presence of 2,6-dimethylpyridine afforded a dinuclear Ho^III complex [Ho₂(L)₆(phen)₂] (1) (L = anthracene-9-carboxylate), which was characterized by elemental analysis and single-crystal X-ray diffraction analysis (triclinic system, space group Pī, with a = 12.4994(3), b = 13.3556(3), c = 14.9751(3) ?, α = 110.7630(1), β = 103.0680(1), γ = 106.8530(1)°, V = 2080.59(9) ?³, and Z = 1). Complex 1 has a centrosymmetric binuclear cage structure in which two Ho^III atoms are both nine-coordinated and bridged by four bulky anthracnene-9-carboxylate (L) ligands with a non-bonding Ho∙∙∙Ho separation of 3.9076 (2) ?. The anthracene-9-carboxylate groups coordinate each Ho^III atom in three different ways. The adjacent discrete dinuclear subunits are arranged into a one-dimensional (1D) chain along the [111] direction by intermolecular π···π stacking interactions, with the centroid–centroid separation of 3.724(2) ?.