Proton Transfers along Hydrogen Bonds in the Tautomerization of Purine

Tautomerization of purine in the water cluster was investigated by the use of DFT calculations. The correlation between the reaction paths and the number of water molecules (<i>n</i>) was examined. For <i>n</i> = 3 and <i>n</i> = 4, concerted reaction paths were obtained. However, for <i>n</i> = 5, a stepwise path including an ion pair intermediate was found with small activation energies. The <i>n</i> = 4 + 3 and <i>n</i> = 4 + 3 + 9 models were calculated to give further small activation energies, where <i>n</i> = 4 constitutes the reaction center and +3 and +3 + 9 denote the number of catalytic water molecules. The combination of the in-plane deprotonation at the N9 site and the out-of-plane protonation at the N7 site makes the <i>n</i> = 4 model probable. Three protonated <i>n</i> = 4 + 3 + 9 routes, a, b, and c, composed of purineH⁺(H₂O)₄₊₃₊₉ were investigated. The <i>n</i> = 4 + 3 moiety is also included in the three routes, and the route c (with the N1 protonation) was found to be most favorable. The purine tautomerization was found to involve the Zundel cation in the ion pair intermediate

School students - Grade 8, Div 1, ca. 1928

Teacher - Tom Aldworth

PCE, FF, J_sc, and V_oc of OPVs fabricated using different additive solvents.

<p>PCE, FF, J_sc, and V_oc of OPVs fabricated using different additive solvents.</p

SEM image of the MoO₃ thin film fabricated by the spin-coating process.

<p>The concentration of MoO₃ aqueous solution was 0.05 wt%.</p

New Access to 2,3-Disubstituted Quinolines through Cyclization of <i>o</i>-Alkynylisocyanobenzenes

o-Alkynylisocyanobenzenes underwent nucleophile-induced intramolecular cyclization to give 2,3-disubstituted quinoline derivatives in high yields. In addition to the oxygen and nitrogen nucleophiles such as methanol and diethylamine, the nucleophilic carbon of the enolate of malonate induced the cyclization effectively. Reaction of 1,4-di(trimethylsilylethynyl)-2,3-diisocyanobenzene with methanol afforded 2,9-dimethoxy-1,10-phenanthroline in good yield

Current-density-voltage characteristics of OPVs incorporating MoO₃ layer fabricated using different concentrations of acetone.

<p>Current-density-voltage characteristics of OPVs incorporating MoO₃ layer fabricated using different concentrations of acetone.</p

OPV characteristics as a function of acetone concentration.

<p>OPV characteristics as a function of acetone concentration.</p

AFM images of MoO₃ thin films fabricated using different concentrations of acetone.

<p>Concentrations were (a) 0, (b) 20, (c) 30, (d) 40, and (e) 50 vol%.</p

Schematic configuration of the ESD setup.

<p>Schematic configuration of the ESD setup.</p

Current-density-voltage characteristics of OPVs with MoO₃ layers fabricated using different additive solvents.

<p>Current-density-voltage characteristics of OPVs with MoO₃ layers fabricated using different additive solvents.</p