A one dimensional coordination polymer composed of antiferromagnetically coupled disk-like [Mn7] units

Abstract

The synthesis, characterization by X-ray analysis and magnetic properties of a one dimensional coordination polymer {[Mn₇(OH)₂(dhap)₂(N₃)₃(MeCN)₄(ClO₄)₂]·2(MeCN)·2(ClO₄)}_∞ (1) are reported. The ligand dhapH₄ in the complex is 2,6-bis[N,N-di(hydroxyethyl)aminomethyl]pyridine. This compound crystallizes in the monoclinic space group C2/c. Each [Mn₇(OH)₂(dhap)₂(N₃)₃(MeCN)₄(ClO₄)₂] unit (abbreviated by Mn₇) is linked end-to-end by azido ligands to its neighboring units to form a one dimensional polymer. Magnetic susceptibility measurements indicate that the polymer is composed of S = 8 units with inter-Mn₇-unit antiferromagnetic coupling. The Jahn–Teller axes of the Mn₇ units are arranged in a zigzag manner along the polymer chain which induces spin canting at low temperatures. The slow magnetization relaxation at low temperatures was evidenced by observing out-of-phase signals in ac magnetic susceptibility measurements that give U_eff = 47.5 K and Δ₀ = 2.7 × 10⁻¹³ s. This phenomenon also indicates that this one dimensional coordination polymer functions as a single-chain magnet (SCM).