title: Stability and isomerization of complexes formed by metal ions and cytosine isomers in aqueous phase.
abstract: We present a systematic study of the stability of the formation of complexes produced by four metal ions (M(+/2+)) and 14 cytosine isomers (Cn). This work predicts theoretically that predominant product complexes are associated with higher-energy C4M(+/2+) and C5M(+/2+) rather than the most stable C1M(+/2+). The prediction resolves successfully several experimental facts puzzling two research groups. Meanwhile, in-depth studies further reveal that direct isomerization of C1↔C4 is almost impossible, and also that the isomerization induced by either metalation or hydration, or by a combination of the two unfavorable. It is the single water molecule locating between the H1(-N1) and O2 of the cytosine that plays the dual roles of being a bridge and an activator that consequently improves the isomerization greatly. Moreover, the cooperation of divalent metal ion and such a monohydration actually leads to an energy-free C1←C4 isomerization in the gas phase. Henceforth, we are able to propose schemes inhibiting the free C1←C4 isomerization, based purely on extended hydration at the divalent metal ion.
authors.affiliation: Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, School of Chemistry and Chemical Engineering, University of Jinan, Jinan City 250022, People's Republic of China. chm_aihq@ujn.edu.cn
authors.forename: Hongqi
authors.initials: H
authors.lastname: Ai
authors.forename: Jingjing
authors.initials: J
authors.lastname: Liu
authors.forename: Kwaichow
authors.initials: K
authors.lastname: Chan
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002413:Cations, Divalent; D002414:Cations, Monovalent; D056831:Coordination Complexes / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D007536:Isomerism; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D011188:Potassium / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D056831:Coordination Complexes; D014867:Water; D003596:Cytosine; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium