Electronic-State Fingerprints of Protonation in Crystalline and Amorphous Molecular Solids

Resolving protonation-dependent electronic states in molecular solids remains a fundamental challenge, particularly in disordered materials where conventional structural methods fail to provide molecular-level insight. Here, we establish sulfur K-edge X-ray absorption near-edge spectroscopy (XANES) as an atom-specific probe that captures electronic-state fingerprints of protonation and intermolecular interactions in sulfonyl-containing molecular solids. Using glyclopyramide as a representative sulfonylurea compound, crystalline salts, cocrystals, and coamorphous phases were systematically investigated to elucidate how proton transfer modulates local electronic structure. Distinct S K-edge spectral features are highly sensitive to electronic changes in the sulfonylurea moiety, enabling clear discrimination between molecular and ionic states. Notably, these electronic-state fingerprints persist in coamorphous phases, demonstrating that protonation-dependent electronic structures can be resolved even in the absence of long-range order. Correlation of the spectral signatures with supramolecular synthons further reveals a clear relationship between local electronic structure and supramolecular organization across crystalline and amorphous phases. In contrast, Cl K-edge spectra primarily report local chemical environments, highlighting the unique electronic sensitivity of sulfur K-edge analysis. These findings establish electronic-state fingerprints as a robust descriptor of proton-transfer-driven interactions, providing a general framework for understanding and designing crystalline and amorphous molecular materials.s electronic changes in the sulfonylurea moiety, enabling clear discrimination between molecular and ionic states. Notably, these electronic-state fingerprints persist in coamorphous phases, demonstrating that protonation-dependent electronic structures can be resolved even in the absence of long-range order. Correlation of the spectral signatures with supramolecular synthons further reveals a clear relationship between local electronic structure and supramolecular organization across crystalline and amorphous phases. In contrast, Cl K-edge spectra primarily report local chemical environments, highlighting the unique electronic sensitivity of sulfur K-edge analysis. These findings establish electronic-state fingerprints as a robust descriptor of proton-transfer-driven interactions, providing a general framework for understanding and designing crystalline and amorphous molecular materials.