Ruthenium nitrosyl complexes with NO release capability: the use of fluorene as an antenna

A ruthenium nitrosyl complex of formula [Ru^II(fluorene(C6)CH₂O-terpy)(bipy)(NO)]³⁺ (AC) in which fluorene(C6) is the 9,9-dihexylfluorene, terpy the 2,2';6',2''-terpyridine, and bipy the 2,2'-bipyridine is presented with its related [Ru^II(MeO-terpy)(bipy)(NO)]³⁺ (C) and 9,9-dihexylfluorene 2-hydroxymethylfluorene (A) building blocks. The reference complex C undergoes NO release capabilities under irradiation at λ = 365 nm. The effect of the introduction of the fluorescent A antenna within the resulting AC complex is discussed both experimentally and theoretically. The importance of the encaging parameter defined as ϕAC·IAC, in which IAC is the quantity of light absorbed by AC and ϕAC the quantum yield of NO release is evidenced and found to be concentration dependent. The conditions of optimization of the antenna approach to maximize ϕAC·IAC are discussed. The crystal structure of [Ru^II(fluorene(C6)CH₂O-terpy)(bipy)(NO₂)](PF₆), the last intermediate in the synthesis of AC is also presented.