Luminescence of lanthanide complexes designed the molecular helicity and chirality

Abstract

Luminescent lanthanide (Ln) compounds are already applied for fingerprint recognition for security codes and bioprobes because the luminescence colors remain steady because of their quite stable electronic transitions related to the inner-core of Ln. However, the ff emission of rare earth ions is originally weak because it is parity-forbidden. The light emitting efficiency is remarkably increased by the antenna effect of the π-electron organic ligand because the ff emission of the Ln ion appears as narrow bands because of the inner-core transitions being shielded from the outer-sphere. Also, the introduction of helicity into the molecular structure breaks the symmetry of the molecule and allows electronic transitions. Introduced here is a luminescent rare-earth complex that introduces chirality into its helical molecular structure. We compared circularly polarized luminescence properties of two kinds of rare earth complexes stably existing in solution, and clarified the correlation between their molecular structures and luminescence properties.