A series of s-dialkynyl ruthenium complexes showing a D-p-[M]-p-A structure (where [M] ¼ [Ru(dppe) 2 ], dppe ¼ bisdiphenylphosphinoethane) were designed and synthesized for dye-sensitized solar cell (DSSC)applications. The molecular structure of these highly modular organometallic complexes was fine-tuned through the introduction of a bithiophene, rhodanine or benzothiadiazole unit. This original molecular engineering approach combined with convergent synthetic pathways thus afforded efficient photosensitizers with tunable colors across the visible spectrum, ranging from red to purple, blue and blue-green dyes. The optoelectronic properties of the new complexes were fully assessed and the dyes were tested in standard single-dye devices as well as in co-sensitized DSSCs, yielding 7.5% power conversion efficiency in the presence of an iodine-based liquid electrolyte. ; Tel: +33 5 40 00 24 25 † Electronic supplementary information (ESI) available: Materials and methods, synthetic procedures, compound characterization, and theoretical calculation details. See a DE ge ¼ main transition energy. b l ge ¼ calculated l max . c f ge ¼ oscillator strength. d Only the transitions with coefficients higher than 0.15 are given. e L ¼ spatial overlap. f q CT ¼ quantity of transferred charge. g D CT ¼ distance between the barycentres of the density depletion and density increment zones related to the CT excitation. J. Mater. Chem. AThis journal is

The design and preparation of an asymmetric ruthenium-diacetylide organometallic complex was successfully achieved to provide an original donor-π-[M]-π-acceptor architecture, in which [M] corresponds to the [Ru(dppe)2] (dppe: bisdiphenylphosphinoethane) metal fragment. The charge-transfer processes occurring upon photoexcitation of the push-pull metal-dialkynyl σ complex were investigated by combining experimental and theoretical data. The novel push-pull complex, appropriately end capped with an anchoring carboxylic acid function, was further adsorbed onto a semiconducting metal oxide porous thin film to serve as a photosensitizer in hybrid solar cells. The resulting photoactive material, when embedded in dye-sensitized solar cell devices, showed a good spectral response with a broad incident photon-to-current conversion efficiency profile and a power conversion efficiency that reached 7.3 %. Thus, this material paves the way to a new generation of organometallic chromophores for photovoltaic applications.