Ferromagnetic End-to-End Azides and Tetrahedral Cobalt: Unusual Findings in the M-BPA-Pseudohalide₂ System

Abstract

Two novel unusual compounds [Co(NCO)2(bpa)] (1) and [Cu(N3)2(bpa)] (2) with cyanate and azide pseudohalides are shown in this work. These compounds have been characterized by X-ray diffraction measurements, Fourier transform-infrared (FT-IR) and UV−visible spectroscopies, thermogravimetric studies, electron spin resonance (ESR) spectroscopy, and magnetic measurements. Compound 1 shows a one-dimensional (1D) structure with the cobalt atoms bridged by bpa ligands and with the metal atoms showing an unusual tetrahedral coordination sphere. Compound 2 shows a two-dimensional (2D) structure, where the copper(II) ions are bridged by double 1,3-azido ligands to form chains that are joined through single bpa bridges to give the global 2D structure. Magnetic measurements show predominance of spin−orbit coupling for the cobalt compound (1), while ferromagnetic interactions, unusual for the 1,3-azido bridging, are observed in compound 2. This compound represents the first example of copper-double (μ1,3-azido)-bridged chain exhibiting ferromagnetic interactions through this kind of bridging.