In this work, we elucidate the electronic charge redistributions that occur within the cyanuric acid (CA) and melamine (M) molecules upon formation of the triple H-bond between the imide group of CA and the diaminopyridine group of M. To achieve this, we investigated 2D H-bonded assemblies of M, CA and CA*M grown on the Au(111) surface, using X-ray photoemission (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopies. Compared to the homomolecular networks, the spectra of the mixed sample reveal core level shifts in opposite directions for CA and M, indicating a nearly complementary charge accumulation on the CA molecule and a charge depletion on the M molecule. These findings were further confirmed by theoretical simulation of the ionization potentials (IPs), which were computed using unsupported models of the H-bonded networks. A natural bond orbital (NBO) analysis performed on the three systems helped to rationalize the net charge transfer form M to CA. Finally, we observed that intramolecular interactions (electron delocalization effects) contribute progressively to the charge redistributions inside the two molecules when going from the homomolecular to the heteromolecular networks.
Inter- and Intra-Molecular Charge Redistributions in H-Bonded Cyanuric Acid*Melamine (CA*M) Networks: Insight From Core Level Spectroscopy and Natural Bond Orbital Analysis / Toffoli, D.; Costantini, R.; Bernes, E.; Nardi, L. D.; Balducci, G.; Viola, E.; Fronzoni, G.; Cossaro, A.; Lanzilotto, V.. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - 31:(2025), pp. 1-9. [10.1002/chem.202403782]
Inter- and Intra-Molecular Charge Redistributions in H-Bonded Cyanuric Acid*Melamine (CA*M) Networks: Insight From Core Level Spectroscopy and Natural Bond Orbital Analysis
Viola E.;Lanzilotto V.
2025
Abstract
In this work, we elucidate the electronic charge redistributions that occur within the cyanuric acid (CA) and melamine (M) molecules upon formation of the triple H-bond between the imide group of CA and the diaminopyridine group of M. To achieve this, we investigated 2D H-bonded assemblies of M, CA and CA*M grown on the Au(111) surface, using X-ray photoemission (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopies. Compared to the homomolecular networks, the spectra of the mixed sample reveal core level shifts in opposite directions for CA and M, indicating a nearly complementary charge accumulation on the CA molecule and a charge depletion on the M molecule. These findings were further confirmed by theoretical simulation of the ionization potentials (IPs), which were computed using unsupported models of the H-bonded networks. A natural bond orbital (NBO) analysis performed on the three systems helped to rationalize the net charge transfer form M to CA. Finally, we observed that intramolecular interactions (electron delocalization effects) contribute progressively to the charge redistributions inside the two molecules when going from the homomolecular to the heteromolecular networks.File | Dimensione | Formato | |
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