The influence of different cations on the structure and spectral properties of Ln3+ tetrakis-complexes with the CAPh-type ligand dimethyl-N-trichloroacetylamidophosphate

Abstract

Lanthanide coordination compounds NMe₄[LnL₄], NEt₄[LnL₄] and PPh₄[LnL₄] (Ln³⁺ = Eu, Gd, Tb) with the carbacylamidophosphate (CAPh) ligand dimethyl-N-trichloroacetylamidophosphate (HL= Cl₃CC(O)N(H)P(O)(OMe)₂) were synthesized. These complexes are characterized using infrared, ultraviolet diffuse reflection, and luminescence spectroscopy as well as through elemental and X-ray analyses. The effect of changing the cation type on the structure and luminescence properties of the tetrakis-complex [LnL₄]⁻ was analyzed. TD-DFT calculations reveal cation-specific contributions to the excited states in tetrakis complexes, with [PPh₄]⁺ playing a central role in both singlet and triplet states. This leads to longer donor–acceptor distances compared to NMe₄[LnL₄] and NEt₄[LnL₄]. Additionally, intramolecular energy transfer (IET) calculations for Eu³⁺ and Tb³⁺ tetrakis compounds reveal Tb³⁺ sensitization via S₁ and Eu³⁺via the typical T₁ state.