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oai:figshare.com:article/34020461 2026-09-29T02:05:47Z category_1 category_4 category_12 category_14 category_15 category_19 category_21 category_873 category_39 category_64 category_135 portal_63 item_type_6 month_year_09_2026

Hydrogen Bonds Regulate Paramagnetic Spin Delocalization in Ferric Hemes Paulami Chakraborty (24604779) Tzu-Hsien Tseng (23269639) Poulomi Pramanik (25133753) Sreya Sasmal (25133756) Peter P.-Y. Chen (19353059) Sankar Prasad Rath (1655494) Biophysics Biochemistry Cell Biology Molecular Biology Neuroscience Pharmacology Biotechnology Chemical Sciences not elsewhere classified Ecology Cancer Computational Biology primary coordination sphere facilitate electronic communication coordinate biphenolato fe spin communication beyond spin communication across responsive spin relays controlling spin propagation defined noncovalent framework biological redox centers mediated spin delocalization measurable spin delocalization systematically varied hydrogen paramagnetic iron center hydrogen bonds provide hydrogen bonding functions bonded distal environment 19 </ sup 1 </ sup spin delocalization experimental spin noncovalent interface metal centers tunable pathway tunable conduit systematic control synthetic system surrounding environment subtle secondary strong correlation porphyrin complexes paramagnetic systems may operate density distributions combine experiment Hydrogen bonds in metalloprotein active sites regulate reactivity and facilitate electronic communication between metal centers and their surrounding environment. However, systematic control over hydrogen-bond-mediated spin delocalization has not been achieved in a synthetic system. Here, we combine experiment and theory to demonstrate that hydrogen bonds provide a tunable pathway for spin delocalization from a paramagnetic iron center into the distal secondary coordination sphere. Using a series of five-coordinate biphenolato Fe(III) porphyrin complexes with systematically varied hydrogen-bond strengths, we establish a well-defined noncovalent framework for controlling spin propagation. Paramagnetic ¹H and ¹⁹F NMR spectroscopy reveals pronounced hyperfine shifts within the hydrogen-bonded distal environment, whereas no measurable spin delocalization is detected in analogous complexes lacking hydrogen bonds. Complementary DFT calculations reproduce the experimental spin-density distributions and show that hydrogen bonding functions as an effective ON/OFF switch for spin communication across a noncovalent interface. The strong correlation between hydrogen-bond strength, experimentally observed hyperfine shifts, and calculated spin densities establishes hydrogen bonding as a reversible and tunable conduit for spin communication beyond the primary coordination sphere. These findings provide direct insight into how subtle secondary-sphere interactions govern magnetic communication in paramagnetic systems and may operate as environment-responsive spin relays in biological redox centers. 2026-09-28T00:00:00Z Text Journal contribution 10.1021/acs.inorgchem.6c03997.s001 https://figshare.com/articles/journal_contribution/Hydrogen_Bonds_Regulate_Paramagnetic_Spin_Delocalization_in_Ferric_Hemes/34020461 CC BY-NC 4.0