Absorption Detected Magnetic Resonance (ADMR) for the Investigation of Electronic Interactions in Biological Multichromophoric Systems

Electronic interactions among chromophores govern the photophysical and functional properties of biological multichromophoric systems. Resolving these interactions, however, remains challenging because the spectroscopic signatures of individual chromophores are often obscured by extensive spectral overlap. Absorption-detected magnetic resonance (ADMR) provides a unique approach to addressing this problem by exploiting localized triplet states as selective perturbations of the excitonic manifold. This enables direct investigation of chromophore organization, excitonic coupling, electronic delocalization, and energy-transfer pathways, often revealing interactions that remain inaccessible to conventional optical spectroscopies. In this review, we summarize the principles of ADMR and its application to biological multichromophoric assemblies, with particular emphasis on the unique insights it provides into photosynthetic pigment–protein complexes.