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.
Subject(s)
Aluminum/chemistry , Azo Compounds/chemistry , Gallium/chemistry , Indium/chemistry , Organometallic Compounds/chemistry , Models, Molecular , Organometallic Compounds/chemical synthesis , Photochemical ProcessesABSTRACT
Transient light-induced absorption in LiNbO3 is observed in the blue-green spectral range after pulsed illumination with 532 nm. Its buildup and decay in Fe-doped LiNbO3 is satisfactorily described by a sum of two stretched exponential functions. For undoped LiNbO3, however, only one stretched exponential decay is observed. These experimental results are explained by the formation of both small Nb(Li)4+ electron polarons and O- hole polarons. The mechanism is discussed on the basis of a proposed band scheme.
ABSTRACT
We discuss the computational results of the "Theoretical study of the photoinduced transfer among the ground state and two metastable states in [Fe(CN)5NO]2-" [J. Chem. Phys. 122, 074314 (2005)] with respect to our previously reported polarized absorption study on the metastable states SI and SII in Na2[Fe(CN)5NO]2H2O [D. Schaniel, J. Schefer, B. Delley, M. Imlau, and Th. Woike, Phys. Rev. B 66, 085103 (2002)].
ABSTRACT
We present extinction spectra of sodium nitroprusside exhibiting holographic light scattering after irradiation with coherent light. A characteristic extinction band appearing in the vicinity of the wavelength of the pump beam was discovered as well as an increase of the extinction coefficient over the whole spectral range. These features are proved to originate from diffraction of the probe beam from parasitic holograms and can be explained within the framework of a simple Ewald construction.