Photophysical properties of new terbium (III) organophosphonates

This paper reports on the synthesis, characterization and photophysical properties of the Tb3+ organophosphonates, TbH(O3PR)2, methylphosphonate (R = CH3), ethylphosphonate (R = C2H5), propylphosphonate (R = C3H7), and phenylphosphonate (R = C6H5). The layered Tb3+ organophosphonates were characterized by X-ray diffraction, IR spectroscopy, TG and elemental analysis. The interlayer distances of the Tb3+ organophosphonates evaluated by the X-ray diffractogram were 9.50 Angstrom for TbH(O3PCH3)2, 12.18 Angstrom for TbH(O3PC2H5)2, 14.84 Angstrom for TbH(O3PC3H7)2 and 15.20 Angstrom for TbH(O3PC6H5)2. The Tb3+ luminescence data revealed highly green emissive materials when they were excited at 368 nm, where the characteristic 5D4 --> 7FJ (J=6, 5, 4 and 3) transitions of Tb3+ were observed at 488, 543, 585 and 619 nm, respectively. The lifetime of the Tb(3+ 5)D4 --> 7F5 transition (lambda(exc)=368 nm and lambda(em)=543 nm) for the Tb3+ organophosphonates was evaluated from the decay curves, which values were of 2.88, 2.22, 2.14 and 2.59 ms, respectively for TbH(O3PCH3)2, TbH(O3PC2H5)2, TbH(O3PC3H7)2 and TbH(O3PC6H5)2. TG analysis revealed that these materials are thermally highly stable, with no water molecule in their composition, which makes them potential luminophores.