Core-level spectroscopic probing of the heteromolecular H-bonding interaction in cyanuric Acid/Melamine 2D networks

The preparation of complex molecular architectures routinely exploits the directionality and cooperative strength of hydrogen bonding interactions, which can be used for a reversible control of molecular self-assembly of simple organic molecules. Cyanuric acid (CA) and Melamine (M) are two such examples of simple organic molecules which can assemble in well-ordered two-dimensional networks on solid surfaces. Their CA*M adduct is a prototypical molecular system exhibiting two complementary NH center dot center dot O and NH center dot center dot N hydrogen bonds. In this work we exploit the initial state locality of K-shell core-electron excitation/ionization process to get a detailed information on the electronic structure modification which characterizes the long-range order of the heteromolecular H-bonding motif of the CA*M adduct as compared to the homomolecular CA and M extended structures. Both of N 1s X-Ray Photoelectron spectroscopy (XPS) and N K-shell Near Edge X-Ray Absorption Fine-Structure (NEXAFS) spectroscopy and are used to get complementary information on the prototypical CA*M heteromolecular system characterizing both the H-donor/H-acceptor nature of the molecular constituents and the extent of heteromolecular H-bond formation, due to the quenching of sigma*(N-H) resonances.