The Chemical Foundations of Biomagnetism: From Quantum Spin Dynamics to Macromolecular Coordination

Biomagnetism occupies the interface of bioinorganic chemistry, coordination chemistry, and quantum mechanics, addressing how metal-centered electronic and spin states give rise to magnetic phenomena in living systems. This review highlights the recent developments in the field of electronic, coordinative, and spin-state parameters which control the magnetic properties in five different biological systems that are mechanistically interlinked: (i) biomineralization of nanocrystalline forms of iron oxides namely magnetite (Fe3O4), maghemite (γ-Fe2O3), and ferrihydrite core inside ferritin and magnetosomes associated proteins; (ii) coordination chemistry of paramagnetic agents used as contrast agents for magnetic resonance imaging (MRI); (iii) quantum chemistry of radical pairs responsible for avian magnetoreception through cryptochromes; (iv) processes controlling the formation of ferrihydrite core and iron storage inside ferritin proteins; and (v) role of biomagnetic field in the chemistry of free radicals and reactive oxygen species (ROS). Analysis based on the experimental results obtained by spectroscopy, magnetometry, and computation between 2020 and 2026 illustrates how changes in covalent bonding, spins of electrons, and orbital symmetries result in observable phenomena in magnetic fields that are weak (µT) and strong (T-scale). The discussion is restricted to naturally occurring and biomimetic coordination environments, deliberately excluding industrial synthetic methodologies, in order to foreground the intrinsic coordination chemistry governing these biomagnetic systems.