Photophysical processes for phenanthroline-menthol ligand and its Eu(III) and Tb(III) complexes in solution

Abstract Time resolved luminescence, nanosecond laser flash photolysis, and quantum chemical calculations were used to study the photophysical processes for new chiral ligand ( L ) containing phenanthroline (Phen) and menthol moiety and Eu L 2 (NO 3 ) 3 and Tb L 2 (NO 3 ) 3 complexes. The absorption and luminescence spectra of free L in acetonitrile are shifted to the red at 10 nm with respect to Phen. The lifetime and quantum yield of luminescence of L are significantly increased (τ = 2.5 ns φ f  = 0.059) as compared with Phen (τ = 0.51 ns φ f  = 0.0087 [1]). As a result of intersystem crossing (ISC) ligand L goes to the triplet state (quantum yield φ T  = 0.092). The triplet-triplet absorption spectrum of L is a broad band with maximum at 450 nm. The protonation of L leads to the appearance of LH + form which has a broad luminescence band with a maximum at 482 nm and a lifetime of 38 ns. The Eu L 2 (NO 3 ) 3 complex exists in solution at a high concentration and exhibits a characteristic red luminescence. However, as the concentration of Eu L 2 (NO 3 ) 3 decreases, the complex dissociates and the bands of free L ligand and protonated LH + form appear in the absorption and luminescence spectra. Quantum-chemical calculations allow to calculate the geometry and absorption spectra of free and protonated ligands and Eu L 2 (NO 3 ) 3 complex.