Photoinduced Nitrosyl Linkage Isomers Uncover a Variety of Unconventional Photorefractive Media

Abstract

The ongoing search for new photorefractive materials offering a high photosensitive flexibility is triggered by the limited tuning ability of conventional photorefractive materials, such as electro-optic crystals, photopolymers, or liquid crystals. One of the latest discovered photorefractive materials is Na 2 [Fe(CN) 5 NO] · 2H 2 O, in which metastable linkage isomers of the nitrosyl group can be generated by light irradiation resulting in huge changes of the refractive index up to Dn ∼ 10 -2 .Here we show that this type of photorefraction is a general property arising from the generation of linkage isomers and can thus be found in many compounds containing [ML 5 NO] m± complexes, where M is a transition metal, L a ligand, and m the formal charge of the anion/cation. The benefit of this generality is reflected in the tailoring properties of the photorefractive response such as the spectral sensitivity simply by selecting different representatives of the [ML 5 NO] m± compounds.Conventional photorefractive materials, [1] where the lightinduced modulation of the refractive index is caused by the linear electro-optic effect (Pockels effect), are widely applied in nonlinear optics.[2] They feature reversible photorefractivity without chemical processing allowing for dynamical holography, [3] and the kinetics of hologram formation is described by the well-known Kiev equations. [4] In recent years a second class of reversible photorefractive media for dynamical holography has been established, the unconventional photorefractive materials. Here an optical bistability is at the origin of photorefraction and the kinetics show a characteristic transient behavior.[5] The unique properties of this class were com-

Two‐Color Reversible Switching in a Photochromic Ruthenium Sulfoxide Complex

“…[10] For example, sodium nitroprusside and many of its derivatives feature isomerization of the bound nitrosyl ligand, but only in the solid state at low temperature. [17,18] Heilweil, Webster, Burkey and co-workers have reported one such example in their studies of ultrafast photochromic organometallic compounds. [19] Picosecond transient absorption data for the S-bonded isomer are shown in Figure 2.…”

Photoinduced nitrosyl linkage isomers in complexes based on the photochromic cation [RuNO(NH3)5]3+ with the paramagnetic anion [Cr(CN)6]3− and the diamagnetic anions [Co(CN)6]3− and [ZrF6]2−

“…Here the NO-ligand can be transferred by light irradiation into two metastable isomers [1][2][3][4]. The generation of these NO linkage isomers is connected with a large change of the refractive index of the material, thus rendering these compounds as promising candidate materials for photorefractive applications such as optical switching or fast holography [5]. Starting from the ground state (GS) nitrogen bound configuration M-N-O the oxygen-bound isonitrosyl configuration M-O-N (state SI) can be generated by irradiation with light in the blue-green spectral range.…”

Neutron photocrystallography: simulation and experiment

“…In this manner structures and chemical complexes become accessible which cannot be realized by standard synthetic methods. Static neutron diffraction experiments investigating lightinduced structural changes were started on the optically switchable system Na 2 [Fe(CN) 5 NO]2H 2 O (SNP) [6] which is of interest due to its outstanding photorefractive properties [7]. In SNP two metastable linkage-isomers, labelled SI and SII, of the NO-ligand are generated by light irradiation in the blue-green spectral range as illustrated in Fig.…”