Cycloruthenated complexes of the type [Ru(II)(N^N)2(C^N)](+) (N^N = substituted 2,2'-bipyridine; C^N = substituted 3-(2'-pyridyl)-1,8-naphthalimide ligand) are shown to generate high power conversion efficiencies (PCEs) in the dye-sensitized solar cell (DSSC). It is shown that substitution of the pyridine ring of the C^N ligand with conjugated groups can enhance molar absorption extinction coefficients, while the electron density imparted on the metal center is alleviated by the 1,8-naphthalimide fragment. This latter feature maintains a Ru(III)/Ru(II) redox couple more positive than 0.8 V versus NHE, thereby accommodating regeneration of the oxidized dye by an iodide-based redox mediator. This dye platform can consequently be modulated at various sites to enhance light absorption and suppress recombination between the redox mediator and the TiO2 surface without compromising dye regeneration, thereby maintaining device PCEs as high as 7%. We also introduce a new phosphine-based coadsorbent, bis(2-ethylhexyl)phosphinic acid (BEPA), which is significantly easier to synthesize than the widely used bis(3,3-dimethylbutyl)phosphinic acid (DINHOP) while also facilitating high dye loading.

The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an imidazole or a pyrazole function, dpm-imid and dpm-pz, have been prepared and used as ligands for the synthesis of a series of heteroleptic (acacR)Cu(dpm) complexes (acacH = acetylacetonate; acacCN = 3-cyanoacetylacetonate). The X-ray crystal structures of these complexes revealed that, albeit no particular association mode is observed for the acac capping ligand, one-dimensional networks are formed with the acacCN capping ligand. Whereas the imidazole peripheral ligand is coordinated to the copper center of a neighboring complex in the structure of (acacCN)Cu(dpm-imid), such an interaction is absent for the pyrazole appended derivative, (acacCN)Cu(dpm-pz), leading to an association mode involving the peripheral nitrile group of the acacCN ligand. Upon reaction of the imidazole functionalized complexes, (acac)Cu(dpm-imid) and (acacCN)Cu(dpm-imid), with silver salts, trinuclear species, {[(acacR)Cu(dpm-imid)](2)Ag}(+), are formed as a result of the coordination of the azole nitrogen atom of two copper complexes to the silver ion. As expected, in the case of (acac)Cu(dpm-imid), these species do not self-assemble into an extended network owing to the absence of a peripheral coordinating group. However, for the (acacCN)Cu(dpm-imid) complex, the trinuclear species are equipped with peripheral nitrile groups, thus allowing the binding of metal centers. Consequently, these species self-assemble into one-dimensional polymers with association modes varying with the nature of the anion present in the silver salt.

A strategy for the formation of heterometallic coordination polymers based on novel copper(II) and cobalt(III) heteroleptic complexes (acacCN)Cu(dpm) and (acacCN)Co(dpm)(2) (acacCN = 3-cyanoacetylacetonate; dpm = dipyrrin) is presented. Using dipyrrins appended with a p- or m-pyridyl group, dpm-4py and dpm-3py, four novel copper and cobalt complexes were prepared and characterized both in solution and in the solid state. These two classes of complexes show different electrochemical properties upon investigation by cyclic voltammetry in CH(2)Cl(2). While the copper complexes show only irreversible reduction processes, the voltammogram of the cobalt species reveals the presence of two quasi-reversible reductions. In the solid state, the copper(II) compounds self-assemble to form one-dimensional architectures upon coordination of the peripheral pyridyl group to the copper center, as characterized by single-crystal X-ray diffraction. Owing to the filled coordination sphere of the octahedral cobalt centers, the (acacCN)Co(dpm-py)(2) compounds crystallize as isolated molecules. Upon reaction with silver salts, these complexes form crystalline heterometallic architectures with different organization and dimensionality, depending on the nature of the metal center and the position of the nitrogen atom in the pyridyl group. The two copper complexes lead to the formation of trinuclear species, {[(acacCN)Cu(dpm-py)](2)Ag}(+), resulting from coordination of the pyridyl groups to the silver cations. However, while meta-functionalized complexes self-assemble into an extended architecture via weak interaction of the peripheral nitrile of the acacCN ligand to the Ag(+) cation, this interaction is not present in the para-functionalized analogue. In both networks based on the Ag(BF(4)) salt, coordination of the tetrafluoroborate anion to the silver center in the rather rare chelate mode is observed. Upon assembly of the cobalt metallatectons with silver salts, two-dimensional (2D) coordination polymers are obtained in crystalline form, resulting, however, from different sets of interactions. Indeed, no coordination of the peripheral nitrile of the acacCN ligand is observed in the network incorporating the m-pyridyl-appended dpm; coordination of the pyridyl groups to the silver center and d(10)-d(10) interactions lead to a 2D architecture. In the case of the para analogue, a 2D honeycomb network is observed owing to coordination of the Ag(I) ion to two pyridyl nitrogen atoms and to one peripheral nitrile group of a acacCN ligand. This latter polymer represents a geometrical hybrid of the networks reported in the literature based on homoleptic Co(dpm-4py)(3) and Cr(acacCN)(3) complexes.