Search

The acidities of multiple sites in Cu(+)-adenine and Cu(2+)-adenine complexes have been investigated theoretically. To compare, the acidities of adenine (A) and adenine radical cation (A(*+)) have also been included. The results clearly indicate that the acidities of C-H and N-H groups in Cu(+/2+)-adenine are significantly enhanced relative to the neutral adenine. The acidic order for a given site on adenine and adenine derivatives is as follows: Cu(2+)-adenineA(*+)Cu(+)-adenineA. For Cu(+)-adenine and Cu(2+)-adenine, N3-coordination exhibits N9-H acid, and N1- and N7-coordination exhibits N6-H(a) and N6-H(b) acid, respectively. Additionally, it is found that C2-H group is surprisingly acidic in the coordination complexes. Calculations in aqueous solution reveal that our results can be extrapolated to aqueous solution. Analyses of the electronic properties interpret the highest acidity of Cu(2+)-adenine among the adenine derivatives studied. Also, Electrostatic potential calculations of [A(-H(+))](-) and [A(-H(+))](*) indicate that the removal of H(a) or H(b) from the amino group favors the bidentate coordination, which provides a dative bond from the deprotonated N and the original coordination ligand to copper ion besides the electrostatic interaction between them and thereby stabilizes the [A(-H(+))](-)/[A(-H(+))](*). NBO analysis confirms the electrostatic potential result.

A convenient hydrothermal processing followed by a postheat treatment route is proposed to synthesize well-dispersed, branched β-MnO2 multipods from a branched γ-MnOOH precursor. The key steps in our approach are as follows: (1) by controlling the reactant concentration and reaction time, the monoclinic phase of MnOOH with novel branched multipod nanostructures is synthesized via the hydrothermal reaction of MnSO4·H2O and NaClO3 at 160 °C for 200 min; (2) the prepared branched γ-MnOOH multipods are heated under an air atmosphere at 400 °C for 2 h, and the branched β-MnO2 nanostructures can be successfully obtained without changing the precursor morphologies. The new structures presented here enrich the nanoscale community with new basic materials and offer a new approach for increasing structural complexity and enabling greater potential applications. Furthermore, brief discussions about their formation mechanisms provide insight into the formation processing of other transition-metal oxide multipods.