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A series of functionalized ferrocene derivatives carrying electron-donor and electron-withdrawing (hetero)aromatic substituents has been designed as potential alternative electrolyte redox couples for dye-sensitized solar cells (DSSC). The compounds have been synthesized and fully characterized in their optical and electrochemical properties. A general synthetic approach that implies the use of a microwave assisted Suzuki coupling has been developed to access a significative number of compounds. The presence of different electron-rich and electron-poor substituents provided fine tuning of optical properties and energy levels. HOMO and LUMO energy values showed that the substitution of one or two cyclopentadienyl rings of ferrocene can be successfully exploited to increase the maximum attainable voltage from a standard DSSC device using TiO2 as a semiconductor, opening the way to highly efficient, non-toxic, and cheap redox shuttles to be employed in solar energy technologies.

Thiocyanate-free Ru(II) complexes as photosensitizers for dye-sensitized solar cells (DSSCs) are presented. These classes of complexes have gained in recent times increasing interest due to their more favorable long-term stability compared to conventional thiocyanate-based complexes such as benchmark dyes N719 and Z907. Here two classes of thiocyanate-free ruthenium(II) complexes have been reviewed: (a) bis-bipyridyl complexes bearing an ancillary cyclometallated bidentate ligand; (b) bipyridyl complexes bearing non-cyclometallated bidentate ancillary ligands. The article briefly outlines design strategies and optical and photovoltaic properties of these two families of ruthenium dyes. Although their photovoltaic performances is not as high as that of N719, recent increasing efforts by many research groups have allowed to achieve favorable light harvesting abilities, device photocurrents, and top-ranked power conversion efficiencies in combination with superior long-term stabilities, paving the way to efficient solar devices endowed with long-term chemical and thermal stability for viable large-scale commercialization of DSSCs.

We report on a series of novel homologous push-pull compounds, in which identical donor (a dimethylamino) and acceptor (a malonate ester) functionalities endcap crescent PPV fragments, bearing, respectively, 1, 2 and 3 p-phenylenevinylene units in direct linear conjugation (compounds 7-9). The three compounds exhibit striking differences in their linear and nonlinear optical properties. The shorter compound 7 exhibits aggregation-induced emission with a strong luminescence in the solid state (blue emission, photoluminescence quantum yield 38%), and it is nonemissive in solution; the more extended conjugated systems 8 and 9 show classical aggregation-caused quenching in the solid state, while high quantum yield photoluminescence (21 and 93% in toluene) is restored in diluted solutions, through mechanisms involving intramolecular charge transfer in the excited states. EFISH measurements in solutions demonstrate a strong solvent and concentration dependence. As rationalized with the aid of molecular modelling, compounds 8 and, more markedly, 9 aggregate in stable centrosymmetric dimers in solution. © 2013 the Owner Societies.

A new general synthetic access to carboxylated quaterpyridines (qpy), of interest as ligands for panchromatic dye-sensitized solar cell organometallic sensitizers, is presented. The strategic step is a Suzuki-Miyaura cross-coupling reaction, which has allowed the preparation of a number of representative unsubstituted and alkyl and (hetero)aromatic substituted qpys. To bypass the poor inherent stability of 2-pyridylboronic acid derivatives, we successfully applied N-methyliminodiacetic acid (MIDA) boronates as key reagents, obtaining the qpy ligands in good yields up to (quasi)gram quantities. The structural, spectroscopic (NMR and UV-vis), electrochemical, and electronic characteristics of the qpy have been experimentally and computationally (DFT) investigated. The easy access to the bis-thiocyanato Ru(II) complex of the parent species of the qpy series, through an efficient route which bypasses the use of Sephadex column chromatography, is shown. The bis-thiocyanato Ru(II) complex has been spectroscopically (NMR and UV-vis), electrochemically, and computationally investigated, relating its properties to those of previously reported Ru(II)-qpy complexes.

The first examples of thiocyanate-free thiophene-substituted Ru(II) cyclometalated complexes, based on thiophene-derived 2-(2,4-difluorophenyl)pyridine ligands, are presented and investigated as photosensitizers in DSCs. Upon thiophene substitution the complexes presented enhanced optical properties compared to the reference dye with no thiophene substitution. DSCs based on the dithienyl-derived dye showed power conversion efficiencies up to 5.7%, more than twice that containing the complex without the thiophene substitution.

A chiral ditopic polyammonium receptor featuring two [9]aneN3 moieties separated by a (S)-BINOL linker is able to selectively bind and sense in water (S,S)-tartaric acid over its (R,R)/meso forms. © 2012 The Royal Society of Chemistry.

Two families of thiophene-based 2-arylpyridines, in which aryl is phenyl and 2,4-difluorophenyl, have been developed. The pyridine ring of the new compounds is substituted at the 4-position with π-conjugated electron-rich and electron-poor thiophene-based fragments to tune the optical and energetic properties. The high-yielding synthetic access, which consists of two sequential Suzuki coupling reactions, the first of which is completely regioselective, is of wide applicability and allows access to a large variety of derivatives. The absorption/emission and redox features, as well as the HOMO and LUMO energy levels, have been investigated; the results show that the optical and electronic properties can be tuned over a broad range. The diversity of the characteristics may be effectively exploited by using the thiophene-substituted 2-arylpyridines as ligands in cyclometalated sensitizers for dye-sensitized solar cells and other optoelectronic applications. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We report the design, synthesis and computational investigation of a class of Ru(II)-dyes based on mixed bipyridine ligands for use in dye-sensitized solar cells. These dyes are designed to preserve the optimal anchoring mode of the prototypical N719 sensitizer by three carboxylic groups, yet allowing for tunable optimization of their electronic and optical properties by selective substitution at one of the 4-4' positions of a single bipyridine ligand with pi-excessive heteroaromatic groups. We used Density Functional Theory/Time Dependent Density Functional Theory calculations to analyze the electronic structure and optical properties of the dye and to investigate the dye adsorption mode on a TiO2 nanoparticle model. Our results show that we are effectively able to introduce three carboxylic anchoring units into the dye and achieve at the same time an enhanced dye light harvesting, demonstrating the design concept. As a drawback of this type of dyes, the synthesis leads to a mixture of dye isomers, which are rather tedious to separate. (C) 2013 Elsevier B.V. All rights reserved.