One-Dimensional Single-Chain Molecular Magnet with a Cross-Linked π-π Coordination Network [{CoII(Δ)CoII(Λ)}(ox)2(phen)2]n

A one-dimensional single-chain molecular magnet [{Co-II(Delta)Co-II(Lambda)}(ox)(2)(phen)(2)](n) with a cross-linked pi-pi coordination network has been synthesized hydrothermally and investigated for its structural and magnetic properties. Oxalate (ox) ligands bridge the paramagnetic Co-II metal ions, whereas phenanthroline (phen) ligands exhibit pi-pi coordination networks. The compound has been thoroughly investigated using room-temperature X-ray and neutron diffraction, infrared spectroscopy, dc magnetization, and reverse Monte Carlo (RMC) simulation methods. Rietveld refinement of the powder X-ray and neutron diffraction patterns at room temperature confirms the single-phase formation of the compound in the monoclinic structure with a space group P2(1). Structural analysis reveals that the compound assembles in the form of a one-dimensional zigzag chain-like structure. Chains consist of two asymmetric Delta- and Lambda-Co-II ions and a pi-pi coordinating network bridged by ox and phen ligands, respectively. The chain lies in the crystallographic ac plane, infinite in length with the absence of interchain pi-pi overlap. dc magnetization data fitted over the high-temperature regime (T > 5 K) using the Ising chain model reveals the one-dimensional magnetic nature of the compound with alternately spaced magnetic Co-II sites with two different Lande g factors and exchange coupling constant values. Different Lande g factors (2.5 and 2.1) and negative exchange coupling constant values (-108 and -20 K) at two alternating Coll sites indicate a ferrimagnetic behavior of this chain compound. In the low-temperature regime (T < 5 K) the compound exhibits spontaneous magnetization and hysteresis at 1.6 K, due to the occurrence of long-range three-dimensional (3-D) magnetic ordering. A prominent clustering of the C atoms around the Co atoms is ascertained by RMC analysis of diffuse scattering in the neutron diffraction pattern. The pair correlations distances between Co-Co, Co-C, Co-N, and Co-O atoms are found to be 5.0, 2.2, 2.5, and 2.4 angstrom, respectively, for the compound.