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Synthesis and spectra of isocytosino-8-trifluoromethylquinolone (1), as well as the gas phase InfraRed Multiple Photon Dissociation (IRMPD) spectra in the fingerprint region of the corresponding deprotonated anion (3), its d3 analogue, the monodeprotonated homodimer (2), and its d7 analogue are reported here. The anions represent nucleobase analogues having the hydrogen bonding pattern ADAAD (where A stands for acceptor and D stands for donor), in which the site of negative charge is unambiguous (as opposed to guanine, which has more than one acidic nitrogen). The match between experimental vibrational spectra and calculation is good, except for the out-of-plane HNH bends of the undeuterated and deuterated monomer anions between 400 and 600 cm−1. The anionic homodimers form in a parallel orientation.

Contains fulltext : 182103.pdf (Publisher’s version ) (Open Access) Evidence is presented for cyclization to yield 2-bora-1,3-diazacycloalkanium cations in the gas phase. While the neutral compounds in solution and solid phase are known to possess an acyclic structure (as revealed by X-ray diffraction), the gaseous cations (from which borohydride BH4(-) ion has been expelled) have a cyclic structure, as revealed by InfraRed Multiple Photon Dissociation (IRMPD) spectroscopy and collisionally activated decomposition (CAD). The IRMPD decomposition of the monocyclic ions proceeds principally via H2 expulsion, although CAD experiments show additional pathways. Pyrolyses of solid monomeric salts and small oligomers produce higher polymers that are consistent with H2 expulsion as the major pathway. Deuterium labeling experiments show that scrambling occurs prior to IRMPD or CAD decomposition in the gas phase.