Since the establishment of dye-sensitized solar cells in the early '90s, both the efficiency and stability of these third generation photovoltaics have been greatly enhanced. Nevertheless, there still exist many unwanted processes that impede operation of dye-sensitized solar cells, encumbering the achievement of the maximum theoretical power conversion efficiency and decreasing the devices' long-term operation. These processes include charge recombination, dye aggregation, dye desorption, and high protonation degrees of the semiconductor's surface. This Minireview focuses on a powerful strategy developed to address these problems, namely the use of co-adsorbents. All types of co-adsorbents utilized thus far are categorized in terms of the chemical identity of their anchoring group; in addition their operational mechanisms are presented and the properties that a functional molecule should possess to be applied as an efficient co-adsorbent are discussed.

A series of RuII‐based photosensitizers were synthesized and extensively characterized. The ligand utilized to coordinate ruthenium was a pyridine–quinoline hybrid bearing an anthracene moiety, and it was combined with commercially available 2,2′‐bipyridine (bpy) for the heteroleptic complexes. The produced bichromophoric complexes show very strong and wide UV/Vis absorption bands. The ability of these complexes to act as triplet photosensitizers in the production of singlet oxygen was thoroughly studied by utilizing the photooxidation of 1,3‐diphenylisobenzofuran as the test reaction. The most efficient photosensitizer in this new family of RuII complexes affords singlet oxygen quantum yields and production‐rate efficiencies up to two times higher than those of the benchmark [Ru(bpy)3]2+ parent complex.

Heteroleptic ruthenium(II) sensitizers DV42 and DV51, encompassing a novel unsymmetrical pyridine-quinoline hybrid ligand with extended π-conjugation, were synthesized, characterized, and utilized in nanocrystalline dye-sensitized solar cells. Due to the extended conjugation of DV42 and DV51, the absorption of the corresponding sensitized TiO2 films extends into the red spectral range, shifted by 30-40 nm relative to the absorption of TiO2 films sensitized with the standard Z907 ruthenium(II) dye. Contact angle measurements of DV42- and DV51-sensitized TiO2 films suggest that these films are hydrophilic with contact angle values commonly observed upon sensitization with the standard N3 ruthenium(II) dye. Electrochemical studies of the novel ruthenium(II) dyes show that their first oxidation potentials lie well below the I(-)/I3(-) redox potential allowing easy regeneration. The excited-state oxidation potentials of both dyes lie above the TiO2 conduction band, permitting efficient electron injection from the excited dye molecules into the semiconductor conduction band. Liquid electrolyte dye-sensitized solar cells incorporating DV42- or DV51-sensitized TiO2 photoelectrodes afford overall power conversion efficiencies of 3.24 or 4.36% respectively. These efficiencies are up to 56% of the power conversion efficiencies attained by TiO2 photoelectrodes sensitized by the benchmark Z907 ruthenium(II) dye under similar experimental conditions.

Photocatalysis is a rapidly evolving area of research in modern organic synthesis. Among the traditional photocatalysts, metal-complexes based on ruthenium or iridium are the most common. Herein, we present the synthesis of two photoactive, ruthenium-based complexes bearing pyridine-quinoline or terpyridine ligands with extended aromatic conjugation. Our complexes were utilized in the atom transfer radical addition (ATRA) of haloalkanes to olefins, using bromoacetonitrile or bromotrichloromethane as the source of the alkyl group. The tailor-made ruthenium-based catalyst bearing the pyridine-quinoline bidentate ligand proved to be the best-performing photocatalyst, among a range of metal complexes and organocatalysts, efficiently catalyzing both reactions. These photocatalytic atom transfer protocols can be expanded into a broad scope of olefins. In both protocols, the photocatalytic reactions led to products in good to excellent isolated yields.

Surface functionalization of CNTs (SWCNTs or MWCNTs) with dendronized alkoxy terpyridine‐Ru(II)‐terpyridine complexes has been accomplished using either the “grafting to” or the “grafting from” approaches. Different sets of easily processable hybrid metallo‐CNTs composites have been efficiently synthesized bearing either monomeric or polymeric side chain tpy‐Ru(II)‐tpy dicomplexes. Their characterization through TGA, UV‐Vis, and Raman techniques revealed various modification degrees depending on the methodology employed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2551–2559, 2009