title: Metal-organic frameworks as hosts for photochromic guest molecules.
abstract: Several metal-organic framework compounds (MOF-5, MIL-68(Ga), MIL-68(In), MIL-53(Al)) were loaded with azobenzene (AZB), as confirmed by XRPD measurements and elemental analysis. By IR spectroscopy, it was shown that the light-induced trans/cis isomerization of AZB in these hybrid host-guest compounds is improved compared to that of solid AZB. A population of the excited cis state up to 30% has been obtained for AZB0.66@MIL-68(In). However, no light-induced trans/cis isomerization was observed for AZB0.5@MIL-53(Al). Structural models obtained from high-resolution synchrotron powder diffraction data show that AZB molecules are densely packed within the channels of MIL-53(Al) so that no trans/cis isomerization can occur. A different situation was observed for AZB in the larger channels of MIL-68(Ga). Thus, this investigation shows the influence of the host material on the switching behavior of the embedded AZB molecules.
authors: Department of Chemistry, University of Cologne, Greinstr. 6, 50939 Cologne, Germany.
authors: D
authors: D
authors: Hermann
authors: H
authors: H
authors: Emerich
authors: R
authors: R
authors: Lepski
authors: D
authors: D
authors: Schaniel
authors: U
authors: U
authors: Ruschewitz
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry*; D005708:Gallium / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D055668:Photochemical Processes
chemical_list: D001391:Azo Compounds; D009942:Organometallic Compounds; D007204:Indium; D005708:Gallium; D000535:Aluminum; C009850:azobenzene