No abstract

Abstract15‐MC‐5 complexes associate in the solid state to form chiral compartments capable of binding guests. Using small molecular yardsticks, we are able to assess the size restrictions of these structures. Dicarboxylate guests that are too short to span the GdIII ions are stabilized by solvates that hydrogen bond to the uncoordinated carboxylate, while guests that are too long destroy the weakly associated structure. We also demonstrate that all that is required for guest encapsulation is unsaturation of the chain connection carboxylates rather than necessitating the presence of aromaticity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The reaction of L-phenylalanine hydroxamic acid (H(2)L-pheHA) with copper(II) and lanthanide(III) salts yields 15-Metallacrown-5 structures of the general composition Ln(X)n[Cu(II)(L-pheHA)](5)((3-n)+) where X can represent a wide variety of anions. With five copper ions and one central lanthanide ion, the Ln[15-MC-5] complexes have multiple positions where these anionic guests may bind to the metallacrown host. In addition, these metallacrowns are amphiphilic, containing one face that is primarily hydrophobic (due to the five benzyl side chains which are oriented upon the same face of the molecule) and a face that is hydrophilic which has no impediment to solvent access. While it has been known that aromatic carboxylates bind preferentially to the hydrophobic face and short chain aliphatic carboxylates bind preferentially to the hydrophilic face, there have been no quantitative assessments of the stability of these host-guest complexes. Using Isothermal Calorimetry (ITC) we have determined the binding constants for several carboxylate anions to a variety of metallacrown complexes. The affinities of anions that coordinate to the lanthanide ion on the hydrophobic face are related to the hydrophobicities of the guests, with higher binding strength observed for the more hydrophobic carboxylates. Central metal such as La(III) or Nd(III) which are nine coordinate are able to accommodate two guests on the hydrophobic side; however, central metals such as Gd(III) or Dy(III) which are eight coordinate are limited to encapsulating one guest into the hydrophobic pocket. A second guest, bound to the hydrophilic face is often observed with these 8-coordinate lanthanides. The significantly weaker second binding constant between benzoate and Gd(III)[15-MC-5] supports the model that the second benzoate binds to the central metal through the hydrophilic side. Unlike the Gd(III)[15-MC-5], the higher binding constant of the second benzoate with La(III)[15-MC-5] is consistent with the crystallographic model which shows that the second guest binds to the hydrophobic side.

Iodide redox (3I À /I 3 À ), polysulfide redox (S 2À /S x 2À ), organic redox [TMTU/TMFDS 2+ : tetramethylthiourea/tetramethylformaminium-bis(trifluoromethanesulfonyl)imide], ferrocene redox (Fc/Fc + ), nickel redox [Ni(II)/Ni(III)], and cobalt redox [Co(II)/Co(III)] hole conducting electrolytes were systematically investigated to determine their suitability for use in Sb 2 S 3 -sensitized photoelectrochemical solar cells. A long-term stability test and UV-visible spectral analyses revealed that Sb 2 S 3 -sensitized photoelectrochemical solar cells worked stably with Co(II)(o-phen) 3 (TFSI) 2 /Co (III)(o-phen) 3 (TFSI) 3 [TFSI: bis(trifluoromethanesulfonyl)imide] as the redox mediator.

In modern society, advanced technology has facilitated the emergence of multifunctional appliances, particularly, portable electronic devices, which have been growing rapidly. Therefore, flexible thermally conductive materials with the combination of properties like outstanding thermal conductivity, excellent electrical insulation, mechanical flexibility, and strong flame retardancy, which could be used to efficiently dissipate heat generated from electronic components, are the demand of the day. In this study, graphite fluoride, a derivative of graphene, was exfoliated into graphene fluoride sheets (GFS) via the ball-milling process. Then, a suspension of graphene oxide (GO) and GFSs was vacuum-filtrated to obtain a mixed mass, and subsequently, the mixed mass was subjected to reduction under the action hydrogen iodide at low temperature to transform the GO to reduced graphene oxide (rGO). Finally, a highly flexible and thermally conductive 30-μm thick GFS@rGO hybrid film was prepared, which showed an exceptional in-plane thermal conductivity (212 W·m–1·K–1) and an excellent electrical insulating property (a volume resistivity of 1.1 × 1011 Ω·cm). The extraordinary in-plane thermal conductivity of the GFS@rGO hybrid films was attributed to the high intrinsic thermal conductivity of the filler components and the highly ordered filler alignment. Additionally, the GFS@rGO films showed a tolerance to bending cycles and high-temperature flame. The tensile strength and Young’s modulus of the GFS@rGO films increased with increasing the rGO content and reached a tensile strength of 69.3 MPa and a Young’s modulus of 10.2 GPa at 20 wt % rGO. An experiment of exposing the films to high-temperature flame demonstrated that the GFS@rGO films could efficiently prevent fire spreading. The microcombustion calorimetry results indicated that the GFS@rGO had significantly lower heat release rate (HRR) compared to the GO film. The peak HRR of GFS@rGO10 was only 21 W·g–1 at 323 °C, while that of GO was 198 W·g–1 at 159 °C.