Lanthanide complexes with phosphorylated 2-naphthylsulfonamides ligands as electromagnetic radiation converters

Abstract

The lanthanide complexes of the type Na[Ln(L)4] (LnL1) (Ln = Nd3+, Eu3+, Tb3+, Yb3+), with di(4-methylphenyl) (2-naphthyl)sulfonylamidophosphate (HL1), as well as sodium salt (NaL), were synthesized. Single-crystal X-ray diffraction, IR, absorption and emission spectroscopies at 300, 77 and 4 K were used to characterize the compounds. The ligand-to-metal energy transfer processes were analyzed. The dominant role of the ligand singlet state in intramolecular energy transfer processes was discussed and the main channels of the ligand-to-metal energy transfer for EuL1 are proposed as S1→ 5G3, 5G6, 5D4,5L6 with a fast contribution and S1 → T1 → 5D1 with a slow contribution. The calculations of nonradiative rates of energy transfer covered the higher lying excited levels of Eu3+ (5DJ, 5LJ, 5GJ).The participation of both the multipolar and exchange mechanisms was considered. The number of parameters determined for LnL1 such as: experimental intensity parameters (Ωλ), radiative (Arad) and non-radiative (Anrad) decay rates, emission lifetimes (τ), theoretical and experimental quantum yields were compared with the data for lanthanide complexes with dimethyl (2-naphthyl)sulfonylamidophosphate (LnL2). The strong temperature dependence of the excited 5D4 level lifetime of TbL1 was recorded in the range of 30 μs – 2 ms, in the temperature range 300–77 K. This phenomenon could be used in chemical thermometry.