The use of nitric oxide (NO) for therapeutic treatment is a well known option in cardiovascular, neurological, and immune response systems. Gaining new and comprehensive knowledge on FeNO-corrole systems towards photo-dissociation is a missing piece in the understanding of potentially new designs of photo-NORMs that are used for photo-therapeutic delivery of NO to specific tissue sites. The assignment of the electronic states of FeNO corroles, however, is a longstanding debate and yet unresolved issue. Recent studies using UV-vis and infrared data with broken-symmetry DFT calculations now assign it as {FeNO}7 with a non- innocent corrole ligand. Complete active space self-consistent field (CASSCF) and density matrix renormalization group (DMRG) calculations support the picture of {FeNO}7-corrole•2– rather than {FeNO}6-corrole3–. However, a detailed experimental understanding of the nature of the {FeNO}7 center has not been reached. In this study, we will investigate this issue by a combination of multiple X-ray experiments and multiconfigurational calculations to simulate the experimental spectra. A series of FeNO corroles with different substitutes at corrole meso and β positions will be studied to probe the substituent effects on the corrole non-innocence. The combined experimental and theoretical data performed in this study will reliably characterize the ground state of FeNO-corrole which is the fundamental part in understanding photo-dissociation, which will be specifically investigated in a follow up study.