Nanoscale assemblies of gigantic molecular {Mo-154}-rings: (Dimethyldioctadecylammonium)(20)[Mo154O462H8(H2O)(70)]

Akutagawa, T., Jin, R., Tunashima, R., Noro, S., Cronin, L. and Nakamura, T. (2008) Nanoscale assemblies of gigantic molecular {Mo-154}-rings: (Dimethyldioctadecylammonium)(20)[Mo154O462H8(H2O)(70)]. Langmuir, 24(1), pp. 231-238. (doi:10.1021/la701364k)

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Abstract

Clusters based on the mixed-valence gigantic inorganic ring [Mo154O462H14(H2O)(70)](14-) ({Mo-154}-ring) and dimethyldioctadecylammonium (DODA) were combined to form novel molecular assemblies of an inorganic-organic hybrid molecular system as Langmuir-Blodgett (LB) and cast films. (DODA)(20)[MO154O462H8(H2O)(70)] (2) was prepared by cation exchange and was characterized by a combination of thermogravimetry, IR, UV-vis-NIR, H-1 NMR, and XRD measurements. The salt 2 was soluble in common organic solvents, and the chemical stability Of {Mo-154}-ring encapsulated by DODA cationic surfactants in CHCl3 was found to be higher than that of the "native" sodium salt of the {Mo-154}-ring in H2O. Uniform spherical vesicle-like molecular assemblies of (DODA)(20)[Mo154O462H8(H2O)(70)] were observed in dilute THF, whose average diameter of 95 nm and a normalized variance of 5.7% were confirmed by a X-ray small-angle scattering. Deposition of 2 as a cast film showed circular domains with a typical diameter of similar to 100 nm, indicating possible similarities between solution and surface-deposited structures. The resulting LB films of salt 2 were transferred from an acidic buffer subphase with pH = 1.5 onto mica, giving a two-dimensional film surface with a unity transfer ratio. Further, the electronic absorption spectra of the LB multilayer were consistent with the classic type II mixed-valence Mo-V/Mo-VI electronic state well know for molybdenum blue {Mo-154}-ring systems, and it appears that on the surface the plane of the {Mo-154}-ring is approximately parallel to the substrate surface, as indicated by polarized electronic spectra, while the alkyl chains of DODA were relatively normal to the substrate surface. Therefore, the layer between the {Mo-154}-rings and DODA cations was alternately stacked along the direction of film propagation. Finally, it was found that the surface morphology of the cast and LB films was determined by the molecular assembly of (DODA)(20)[Mo154O462H8(H2O)70] in solution and the air-water interface, respectively.

Item Type:Articles
Keywords:ABSORPTION ABSORPTION-SPECTRA AIR-WATER-INTERFACE AQUEOUS-SOLUTION ASSEMBLIES BUILDING-BLOCKS CATION CATIONS CHAIN CLUSTER CLUSTERS DOMAIN ELECTROCHEMICAL PROPERTIES ELECTRON DELOCALIZATION EXCHANGE FILMS HYBRID IR LANGMUIR-BLODGETT LANGMUIR-BLODGETT-FILMS LB film MIXED-VALENCE Molybdenum MOLYBDENUM-BLUE MORPHOLOGY NANOSCALE NMR ORGANIC-SOLVENTS PH PHYSICAL-PROPERTIES RADICAL SALTS RING SALT SCATTERING SEMIAMPHIPHILIC METHOD SIMILARITY SOLVENT SOLVENTS SPECTRA SPECTRUM STABILITY STATE Structure SURFACE SURFACTANT-ENCAPSULATED CLUSTERS SURFACTANTS SYSTEM SYSTEMS X-RAY XRD
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cronin, Professor Leroy
Authors: Akutagawa, T., Jin, R., Tunashima, R., Noro, S., Cronin, L., and Nakamura, T.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Langmuir
ISSN:0743-7463

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