Comparison of Carbazole and Fluorene Donating Effects on the Two‐Photon Absorption and Nitric Oxide Photorelease Capabilities of a Ruthenium–Nitrosyl Complex

A ruthenium–nitrosyl derivative of formula [RuII(CzT)(bipy)(NO)](PF6)3 [CzT = 4′‐(N‐ethylcarbazol‐3‐yl)‐2,2′:6′,2′′‐terpyridine, bipy = 2,2′‐bipyridine] has been synthesized and fully characterized, and compared with the previously reported [RuII(FT)(bipy)(NO)](PF6)3 complex [FT = 4′‐(9,9‐dihexyl‐9H‐fluoren‐2‐yl)‐2,2′:6′,2′′‐terpyridine]. Additionally, the X‐ray crystal structure of [RuII(CzT)(bipy)(NO2)](PF6), the precursor of [RuII(CzT)(bipy)(NO)](PF6)3, is reported. The presence of a tertiary amine in the carbazole unit leads to redshifted charge‐transfer transitions towards the electron‐withdrawing Ru–NO fragment and hence enhanced two‐photon absorption (TPA) properties. In contrast, the quantum yield of the NO· photorelease process is lower for the carbazole‐containing complex. The issue of optimization of the TPA versus NO·‐release capabilities is addressed.