Photophysical and photochemical characterization of 1-pyrenemethylamine ion-exhanged into a zirconium phosphate framework

The luminescence probe 1-pyrenemethylamine (PYMA), a cationic derivative of pyrene, was used to study the microenvironment of layered zirconium phosphate (ZrP) using spectroscopic techniques. In addition, the intercalation and photophysical characterization of N,N'-dimethylaniline (DMA), an electron donor to excited pyrene molecules, in ZrP layered material was studied.; The direct intercalation of PYMA into the 10.3 A phase of ZrP, a highly hydrated phase of ZrP, was accomplished. The XRPD patterns for the 10.3 A phase ZrP after PYMA exchange (PYMA-exchanged ZrP), at high PYMA concentration, show an increase in the interlayer distance from 10.3 A in unexchanged 10.3 A phase of ZrP to 23.5 A in PYMA-exchanged ZrP indicating PYMA intercalation. The luminescence spectrum for the PYMA-exchanged ZrP exhibits an excimer band at 458 nm that is absent in the luminescence spectrum of PYMA in aqueous solution at low concentrations. The intensity of the excimer emission increased at low PYMA concentrations. A process in which exchange into ZrP at low PYMA concentrations occurs at external surface sites with clustering promoting excimer formation followed by exchange at high PYMA concentrations occurring at interior sites reducing excimer formation is proposed.; The photolysis of PYMA-exchanged ZrP was studied. The luminescence spectrum for a PYMA-exchanged ZrP colloidal suspension in aqueous solution, after irradiation, shows a rapid decrease of the most intense peak at 376 nm and an increase of the peak at 383 nm of the PYMA molecule. The photolysis of a PYMA aqueous solution proceeds slowly to give a luminescence spectrum similar to that observed upon photolysis of PYMA-exchanged ZrP. Pyrene, 1-hydroxypyrene, 1,6-pyrenedione, and 1,8-pyrenedione were identified as stable photoproducts using steady-state luminescence spectroscopy, high performance liquid chromatography, and ultraviolet-visible spectrophotometry. The XRPD pattern for PYMA-exchanged ZrP, after photolysis, shows that the photoproducts remain entrapped between the layers.; The direct intercalation of DMA into the 10.3 A phase of ZrP was accomplished. The XRPD patterns for the DMA-exchanged ZrP, at high loading levels, show the appearance of a new phase with an interlayer distance of 15.1 A indicating DMA intercalation. The photophysical and IR results for DMA-exchanged ZrP indicate that the physical and chemical characteristics of DMA are maintained and that the structure of the ZrP material is not significantly affected.; Quenching experiments of PYMA and PYMA-exchanged ZrP with DMA were performed. The luminescence decay transients of the probe ion are shown to fit to a single exponential decay model. The Stern-Volmer plots indicate a collisional mechanism of deactivation. The bimolecular quenching rate constant obtained for PYMA and PYMA-exchanged ZrP were similar. While the back electron transfer rate constant determined using laser flash photolysis experiments indicates it is larger for PYMA-exchanged ZrP than for PYMA in solution.