Sb(2)S(3)-sensitized mesoporous-TiO(2) solar cells using several conjugated polymers as hole-transporting materials (HTMs) are fabricated. We found that the cell performance was strongly correlated with the chemical interaction at the interface of Sb(2)S(3) as sensitizer and the HTMs through the thiophene moieties, which led to a higher fill factor (FF), open-circuit voltage (V(oc)), and short-circuit current density (J(sc)). With the application of PCPDTBT (poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)) as a HTM in a Sb(2)S(3)-sensitized solar cell, overall power conversion efficiencies of 6.18, 6.57, and 6.53% at 100, 50, and 10% solar irradiation, respectively, were achieved with a metal mask.

Additional photon-harvesting by hole transporting materials in Sb(2)S(3)-sensitized solar cell is demonstrated through the formation of electron channels in the hole transporter such as P3HT (poly(3-hexylthiophene)) and PCPDTBT(poly(2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)) that can act as both a hole conductor and light absorber. As a result, the short-circuit current density is improved with an increment in overall efficiency. These findings provide new insights into use of light-absorbing conjugated polymers as a hole conductor in the inorganic-organic heterojunction sensitized solar cells.

The equilibria for core Ca2+ replacement by Ln3+ in copper(II) 15-MC-5 complexes have been investigated using a series of visible spectrophotometric titrations of calcium(II) metallacrowns ({CaII[15-MCCuII(N)(L)-5]}2+) with Ln3+ ions (H2L = pheha, (S)-α-phenylalaninehydroxamic acid, or trpha, (S)-α-tryptophanhydroxamic acid). These studies allowed the determination of the equilibrium constants for the reaction {CaII[15-MCCuII(N)(L)-5]}2+ + Ln3+ → {LnIII[15-MCCuII(N)(L)-5]}3+ + Ca2+ in methanol/water 9:1 (Ln3+ = La3+, Gd3+, Dy3+, Er3+) or 99:1 (Ln3+ = La3+, Nd3+, Gd3+, Dy3+, Er3+, Yb3+), respectively. The log K for these reactions decreases with increasing atomic number of the lanthanide(III), ranging from 6.1 to 3.91 in methanol/water 9:1. The same behavior is observed in methanol/water 99:1, although the constants are uniformly lower (log K = 4.09−2.52). A significant thermodynamic selectivity was observed for the later lanthanides (Gd3+−Yb3+) while a smaller selectivity is present throughout the beginning of the series (La3+−Gd3+). This observation has been interpreted on the basis of the size correspondence between the metal ions and the metallacrown cavity. The overall stability of the {CaII[15-MCCuII(N)(L)-5]}2+ in methanol/water 9:1 has been determined by pH-spectrophotometric titrations with HCl. The resulting log K values are 63.46(12) and 65.05(13) for pheha and trpha, respectively (Ca2+ + 5Cu2+ + 5HL− = {CaII[15-MCCuII(N)(L)-5]}2+ +5H+). The stability of both the La3+ and Ca2+ 15-metallacrown-5 complexes in the presence of high Na+ concentrations has also been demonstrated by spectophotometric studies. Based upon these observations, the preference of the 15-MC-5 for Ca2+ complexation compared to crown ethers has been quantitatively demonstrated for the first time.

Twenty crystal structures of the Ln(III)[15-MC(CuII(N)pheHA)-5](3+) complex, where pheHA = phenylalanine hydroxamic acid and where Ln(III) = Y(III) and La(III)-Tm(III), except Pm(III), with the nitrate and/or hydroxide anion are used to assess the effect of the central metal ion on the metallacrown structure. Each Ln(III)[15-MC(CuII(N)pheHA)-5](3+) complex is amphiphilic with a hydrophobic side consisting of the phenyl groups of the pheHA ligand and a side without the aromatic residues. Three general structures are observed for the Ln(III)[15-MC(CuII(N)pheHA)-5](3+) complexes. In the Type 1 structures, the central metal ion does not bind a nitrate anion on the metallacrown's hydrophobic face, and two adjacent metallacrowns dimerize through their phenyl groups producing a hydrophobic compartment. In the Type 2 structures, the central metal ion binds a nitrate in a bidentate fashion on the hydrophobic face. There are two distinct types of Type 2 metallacrowns, designated A and B. Type 2A metallacrowns have a water molecule bound to the central metal ion on the hydrophilic face, while Type 2B metallacrowns have a monodentate nitrate ion bound on the hydrophilic face to the central metal ion. The Type 2 metallacrowns also dimerize via the phenyl groups to form a hydrophobic compartment. In Type 3 structures, the central metal ion binds a nitrate in a bidentate fashion on the hydrophobic side, but instead of forming dimers, the metallacrowns pack in a helical arrangement to give either P or M one-dimensional helices. Regardless of the type of metallacrown, the overall trend observed is that as the Ln(III) ion crystal radius increases, the metallacrown cavity radius also increases while the metallacrown becomes more planar. This conclusion is demonstrated by a decrease in the oxime oxygen distances to the oxime oxygen mean plane and a decrease in the ring Cu(II) distances to the Cu(II) mean plane as the metallacrown cavity radius increases and the lanthanide crystal radius increases. In addition, a decrease in the O(oxime)-Cu(II)-N(oxime)-O(oxime) torsion (dihedral) angles is also observed as the metallacrown cavity radius and the lanthanide crystal radius both increase. These observations help explain the thermodynamic preferences for Ln(III) ions within this class of metallacrowns and may be used to design compartments capable of binding guests in different orientations within chiral, soft solids.

Dimeric Ln(3+)[15-metallacrown-5] compartments selectively recognize carboxylates through guest binding to host metal ions and intermolecular interactions with the phenyl side chains. A systematic study is presented on how the size, selectivity, and number of encapsulated guests in the dimeric containers is influenced by the Ln(3+)[15-metallacrown(Cu(II))-5] ligand side chain and central metal. Compartments of varying heights were assembled from metallacrowns with S-phenylglycine hydroxamic acid (pgHA), S-phenylalanine hydroxamic acid (pheHA), and S-homophenylalanine hydroxamic acid (hpheHA) ligands. Guests that were examined include the fully deprotonated forms of terephthalic acid, isonicotinic acid, and bithiophene dicarboxylic acid (btDC). X-ray crystallography reveals that the side-chain length constrains the maximum and minimum length guest that can be encapsulated in the compartment. Compartments with heights ranging from 9.7 to 15.2 Å are formed with different phenyl side chains that complex 4.3-9.2 Å long guests. Up to five guests are accommodated in Ln(3+)[15-metallacrown(Cu(II))-5] compartments depending on steric effects from the host side chains. The nine-coordinate La(3+) central metal promotes the encapsulation of multiple guests, while the eight-coordinate Gd(3+) typically binds only one dicarboxylate. Electrospray ionization mass spectrometry reveals that the dimerization phenomenon occurs beyond the solid state, suggesting that these containers can be utilized in solid-state and solution applications.