Hybridization between Periodic Mesoporous Organosilica and a Ru(II) Polypyridyl Complex with Phosphonic Acid Anchor Groups

A new method for the hybridization of a ruthenium­(II) polypyridyl complex ([Ru­(bpy)₂((CH₂PO₃H₂)₂-bpy)]²⁺ (<b>RuP</b>_<b>2</b>^<b>2+</b>: bpy =2,2′-bipyridine; (CH₂PO₃H₂)₂-bpy =2,2′-bipyridine-4,4′di­(metylphosphonic acid)) with biphenylene-bearing periodic mesoporous organosilica <b>(Bp–PMO</b> made from 4,4′bis­(triethoxysilyl)­biphenyl [(C₂H₅O)₃Si-(C₆H₄)₂-Si­(OC₂H₅)₃]) was developed. Efficient and secure fixation of the ruthenium­(II) complex with methylphosphonic acid groups (<b>RuP</b>_<b>2</b>^<b>2+</b>) in the mesopores of <b>Bp–PMO</b> occurred. This method introduced up to 660 μmol of <b>RuP</b>_<b>2</b>^<b>2+</b> in 1 g of <b>Bp–PMO</b>. Two modes of adsorption of <b>RuP</b>_<b>2</b>^<b>2+</b> in the mesopores of <b>Bp–PMO</b> were observed: one is caused by the chemical interaction between the methylphosphonic acid groups of <b>RuP</b>_<b>2</b>^<b>2+</b> and the silicate moieties of <b>Bp–PMO</b> and the other is attributed to aggregation of the <b>RuP</b>_<b>2</b>^<b>2+</b> complexes. In the case of the former mode, adsorbed <b>RuP</b>_<b>2</b>^<b>2+</b> (up to 80–100 μmol g^–1) did not detach from <b>Bp–PMO</b> after washing with acetonitrile, dimethylformamide, or even water. Emission from the excited biphenylene (Bp) units was quantitatively quenched by the adsorbed <b>RuP</b>_<b>2</b>^<b>2+</b> molecules in cases where more than 60 μmol g^–1 of <b>RuP</b>_<b>2</b>^<b>2+</b> was adsorbed, and emission from <b>RuP</b>_<b>2</b>^<b>2+</b> was observed. Quantitative emission measurements indicated that emission from approximately 100 Bp units can be completely quenched by only one <b>RuP</b>_<b>2</b>^<b>2+</b> molecule in the mesopore, and photons absorbed by approximately 400 Bp units are potentially accumulated in one <b>RuP</b>_<b>2</b>^<b>2+</b> molecule