Bulk Magnetic Properties and Vibrational Raman Scattering Spectroscopy of Four Boron Imidazolate Frameworks

Metal Organic Frameworks (MOFs), compounds consisting of metal ions connected by organic ligands, offer a possibility for tunable magnetic interactions between magnetic metal ions through ligands, creating an ideal space to explore exotic magnetism in real materials. Four MOFs in the boron imidazolate framework (BIF) family containing various magnetic ions connected with a boron imidazolate organic ligand have been studied by magnetization measurements and Raman scattering spectroscopy . Magnetization data reveal four distinct magnetic behaviors, including spin crossover in a paramagnetic system due to crystal electric field effects and superparamagnetism in single-domain ferromagnetic nanoparticles.The different energy regions of lattice modes, metal environment vibrations, and molecular vibrations are shown to act as a reliable fingerprint of the framework lattice, metal environment, and ligand respectively in room temperature Raman spectra. These results establish an efficient method of understanding and assigning vibrational features in metal-organic framework Raman spectra, and demonstrate the existence of magnetic interactions in these MOFs despite extended superexchange pathways between magnetic metal centers.