Unusual π-π interactions directed by the [{(C6H6)Ru}2W8O30(OH)2]6- hybrid anion

The [{(C6H6)Ru}(2)W8O30(OH)(2)](6-) hybrid (organometallic-POM) anion was used as a pH-tunable building block to create special conditions for realizing pi-pi interactions in the crystal structure. Changing the pH of an aqueous solution of Na-6[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 16H(2)O (1) results in isolation of a series of new compounds with different Na+/H+ ratios in the cationic composition: Na5.5H0.5[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 15H(2)O (2), Na5H[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 22H(2)O (3), Na4H2[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 24H(2)O (4), Na3H3[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 23H(2)O (5), and NaH5[{(C6H6)Ru}(2)W8O28(OH)(2)]center dot 9H(2)O (6). All complexes were characterized by single crystal X-ray diffraction (SCXRD) analysis and ICP-AES. The presence of pi-pi stacking was detected for moderate-to-highly protonated 3-6. The energy of such interactions was calculated to increase in the following order: 6 (5.0 kJ mol(-1)) < 5 (7.6 kJ mol(-1)) < 3 (10.0 kJ mol(-1)). 1 was studied for its electrochemical behavior in 0.5 M Li2SO4 and as a paste electrode component in methanol. Catalytic activity in methanol oxidation was detected.

Automated summary

The study utilized a pH-tunable [{(C6H6)Ru}(2)W8O30(OH)(2)](6-) hybrid anion to create new compounds with different Na+/H+ ratios, demonstrating the presence of pi-pi stacking in moderately to highly protonated complexes. Single crystal X-ray diffraction (SCXRD) analysis and ICP-AES were used for characterization, and the energy of the interactions was found to increase in the order of compounds 6, 5, and 3. Catalytic activity in methanol oxidation was observed for compound 1.