Photoprocess of molecules encapsulated in porous solids X: Photosensitization of zeolite-Y encapsulated tris(2,2′-bipyridine– nickel-(II)ion by phenosafranine adsorbed onto the external surface of the nanoporous host

Abstract

Tris-(2,2-bipyridine)-nickel-(II) complex ion encapsulated by zeolite-Y host has been synthesized by ship-in-a-bottle method. Photosensitization of nickel(II) complex (Ni(bpy) 2+ 3) in the zeolite host by surface adsorbed phenosafranine dye was investigated by time-resolved fluorescence and absorption spectral measurements. Formation of nickel (II)-complex in the super cage of the host was ascertained by XRD, FTIR, solidstate NMR, diffuse reflectance UV-visible absorption spectroscopic techniques and ICP-OES measurements. Phenosafranine dye adsorbed on the external surface of zeolite-Y shows a decrease in fluorescence intensity with increased loading of the nickel(II) complex in zeolite-Y. Time-resolved emission studies show two excited state lifetimes for the photoexcited phenosafranine dye. Average fluorescence lifetimes of the dye in this case do not change with increase in the loading of the nickel(II) complex. However, relative contribution of short lifetime component increases when the amount of encapsulated nickel(II) complex is increased. The zeolite-Y host containing only bipyridyl ligand shows a marked decrease in fluorescence intensity. Fluorescence lifetimes of the dye however do not change with increased loading of bipyridyl while relative contribution of short lifetime component increases with an increase in the loading of bipyridyl in the host. This observation is interpreted to be due to electron transfer from the excited state of phenosafranine dye to the bipyridine. Picosecond pump-probe investigations confirm that the photoinduced electron transfer occurs from the surfaceadsorbed phenosafranine in the excited state to the nickel(II) complex within zeolite-Y cavity and also to the Ni(bpy) 2+ 3 complex in contact with the phenosafranine dye co-adsorbed on the external surface of the host.

Photochemistry and Photophysics in Silica-Based Materials: Ultrafast and Single Molecule Spectroscopy Observation

“…The introduction of metal complexes, acting as electron acceptor, into SBMs has also been extensively studied. ,,,− In these hosts, long-lived CS states with lifetimes from nanoseconds to seconds were recorded. ,,, For example, when phenosafranine (PHNS, Scheme ) was adsorbed in the Y-zeolite surface in the presence of caged metal complexes of nickel­(II), (Ni­(bpy) 3 ) 2+ induced intermolecular ET processes in the nanoseconds regime (Figure ). Upon excitation of the composites, the adsorbed PHNS molecules transfer an electron to the Ni complex that is also encapsulated in the Y-zeolite supercage …”

“…Representation of PHNS adsorption on the surfaces of (A) NaY and (B) (Ni­(bpy) 3 ) 2+ NaY. Reprinted with permission from ref . Copyright 2014 Springer.…”

“…The photosensitization of TiO 2 in cages or micro- and mesoporous materials has been used as a strategy for the formation of ET complexes. Several studies of the photophysical properties of PHNS (Scheme ) adsorbed on different zeolites and mesoporous materials that were photosensitized with TiO 2 NPs have been published. ,,− PHNS is an azine derivative that can behave as an electron A and D in both the ground and excited states, which makes it an important molecule in the field of ET. When this dye is trapped within NaY and ZSM-5 supercages, its fluorescence decays are biexponential, with time constants of 0.48 and 1.42 ns (PHNS/NaY) and 0.13 and 0.55 ns (PHNS/ZSM-5), which are similar to those observed when silica nanoparticles were used, reflecting that this molecule mostly interacts with the zeolite surface .…”

Hot-Electron Photodynamics of Silver-Containing Nanosized Zeolite Films Revealed by Transient Absorption Spectroscopy

“…Ultrafast time-resolved spectroscopy is a method of choice to investigate the electronic properties of metal nanoparticles, It is however worth noting that up until now, pump–probe measurements in zeolites have still remained quite seldom and have been performed essentially either on micron-sized crystalline powders − or on colloidal suspensions consisting of nanosized zeolites. ,, The latter approach allows performing transient absorption measurements in transmission but suffers from the lack of control of the metal surrounding in the solution. As an alternative, we are exploring a novel route that consists of performing the transient absorption measurements on transparent zeolite films.…”

Activation of Oxygen Reduction Reaction on Carbon Supported Ni‐Based Complexes

“…In the case of Ni-bimz, as confirmed through XRD, UV-Vis spectra remained the same before and after exposure to KOH. The broad transition at around 320-450 nm in Ni-bpy (both before and after exposing to KOH) is due to metal to ligand charge transfer [51] and one at 537 nm (shown as inset) is due to weak d-d transition [52] (Figure 3b). These results confirm that the primary coordination sphere of these complexes is intact even after exposing to KOH solution.…”