Synthesis, structure and tuneable white-light emission of dinuclear Eu(III),Tb(III)-mixed Schiff base complexes

Abstract

A new family of lanthanide-Schiff base complexes have been synthesized and fully characterized from the novel Schiff base ligand: H 2 L 1 (acetic acid 2-hydroxy-benzylidene-hydrazide). The single crystal X-ray structure and mass spectroscopy reveal the isostructural dinuclear complexes: [Ln 2 L 1 (HL 1 ) 3 (NO 3 )] where Ln = Sm, Eu, Gd and Tb. Upon excitation of the Ln III complexes in solution, their luminescence spectra display the broad ligand centred (LC) band at~470 nm as well as the narrow f-f transitions. In Eu III complex, the LC emission is efficiently quenched, because of the better triplet state energy match to the Eu III -5 D 4 excited states. Doping methods of Eu III with Tb III into the complexes: [Eu x Tb 1-x (L 1 )(HL 1 ) 3 (NO 3 )], x = 0.5 (A), 1.0 (B) and 1.5 (C); in MeOH/DCM (1:10), have revealed variable colours. By careful control of the amounts of Eu III and Tb III in the dinuclear mixed EuTb-complexes, white-light emission is obtained from blue LC band, green Tb III luminescence and red Eu III luminescence. Such behaviour is attributed to the efficient sensitization of Eu III by the ligand and the metal to metal energy transfer from Tb III to Eu III excited 4f states.

An efficient pink luminescent Eu(iii) coordination polymer excited on a blue LED chip

“…From the 77 K phosphorescence spectrum of Gd1 , T 1 of the DHTP is calculated which is equal to 21 800 cm −1 (458 nm) and is comparable to that of related terephthalate ligands reported previously. 38 The energy gap (Δ E ) between T 1 and 5 D 0 falls within the range suggested by Latva's rule, 39,40 Δ E = 4500 cm −1 , highlighting the efficiency of Eu-CPs. Moreover, according to Reinhoudt's empirical rule, 41 the intersystem crossing (ISC) process becomes effective if the energy difference, Δ E (S 1 – T 1 ), is around 5000 cm −1 .…”

Phenothiazine and triphenylamine-based fluorescent Schiff bases for the dual application of white light generation and H2O2 sensing

“…White light-emitting organic fluorophores (OFs) have garnered pivotal research interest because of their potential application in the fields of organic light-emitting diodes (OLEDs), backlighting sources and full-color panel displays. 1–3 White light emission (WLE) in the case of OFs is obtained either by the tandem combination of different components exhibiting the three primary colors (red, blue and green) simultaneously or by a single moiety that covers the entire visible spectrum. 4–7 Nevertheless, according to Kasha's rule, the brute force emission of the entire visible spectrum by a single OF is extremely challenging.…”

Triazine based Mn (II) and Mn (II)/Ln (III) complexes: Synthesis, characterization and catecholase activities

“…The coordination compounds are also used as model compounds for the active sites of the various enzymes . On the other hand, lanthanide (III) complexes have received considerable attention due to relevance of these compounds in applied research in wide variety of science ranging from chemistry to material science . Due to their versatile properties, lanthanide complexes have found applications in the design of advance materials such as Ln‐doped semiconductors, magnetic, catalytic, nonlinear optical, magnetic resonance imaging (MRI) materials and fluorescent sensors …”