Tuning White Light Emission in Dinuclear Phenoxo Bridged Dy^III Complexes

Abstract

A new series of dinuclear dysprosium­(III) complexes, [Dy2(LCH3 )2(NO3)2(MeOH)2] (I), [Dy2(LCH3 )2(NO3)2(DMF)2]·2DMF (II), [Dy2(LCl)2(NO3)2(DMF)2]·2DMF (III), and [Dy2(LCH3O)2(NO3)2(DMF)2] (IV), with 2,2′-[[(2-pyridinylmethyl)­imino]­di­(methylene)]­bis­(4-R-phenol), where R = CH3, Cl, and CH3O, were investigated as potential white light emitters. All octacoordinated dysprosium­(III) are phenoxo-bridged species and have a similar coordination environment. Nevertheless, I has a MeOH ligand molecule, while for II–IV a DMF ligand replaces that of MeOH. The nature of the coordinated solvent molecule plays an important role in the behavior of the thermal dependence of the Y/B (yellow/blue) emission ratio of the DyIII complexes (Y: 4F9/2 → 6H13/2, yellow and B: 4F9/2 → 6H15/2, blue transitions),, since for I the variation of this ratio is significant, while for the other DyIII complexes with DMF as ligand the ratio remains constant within experimental error. At room temperature the CIE (Commission International d’Eclairage) color coordinates for the DyIII complexes, I (0.286, 0.317), III (0.302, 0.324), and IV (0.322, 0.348) are close to the NTSC (National Television System(s) Committee) standard value for white color. Varying the temperature from 16 to 300 K the CIE coordinates for I change from the blueish to white region of the chromaticity diagram, while those of II present an inverse thermal dependence as compared to I. The CCT (Correlated Color Temperature) values at room temperature for I (8384 K), II (17235 K), and IV (5948 K) permit us to consider these complexes as candidates for white cold light emitters, the high value of II being uncommon. For I and II the CCT values vary strongly with temperature, showing a decrease with increasing temperature for I, and an increase with increasing temperature for II, thus making evident the influence on the photophysical properties of the nature of the coordinated solvent molecule in these complexes.

Field-Induced Single Molecular Magnetism and Photoluminescence in Rare Cocrystals of Isomorphic Lanthanide(III) Coordination Compounds with Fully Substituted Pyridine-4-carboxamide Ligand

“…70 Recent literature reports show that Dy(III) compounds are capable of producing white light as one component. 70 In terms of colour purity compound 3 displays very low colour purity which is essential for good white light emitter. 71 In general, the accepted CCT values should be greater than (> 5000 K) and (< 5000 K), for cold and warm light emission, respectively 72 The CCT value observed for 3 is 6942 K hence it may serve as a cold, white light emitter in lighting applications.…”

Four Dinuclear and One-Dimensional-Chain Dysprosium and Terbium Complexes Based on 2-Hydroxy-3-methoxybenzoic Acid: Structures, Fluorescence, Single-Molecule-Magnet, and Ab Initio Investigation

“…The organic ligand of H 2 MBA and complexes [Y 2 (HMBA) 2 (MBA) 2 (H 2 O) 2 (DMF) 2 ]·6H 2 O and [NH 4 ]­[Y­(HMBA) 4 ] exhibit an emissive peak around about 430 nm under UV-light excitation (Figure S4). According to this experiment, the energy of the lowest triplet state of the H 2 MBA ligand is equal to ∼23809 cm –1 , which is higher than the energy levels of 4 F 9/2 (∼20960 cm –1 , Dy 3+ ) and 5 D 4 (∼20430 cm –1 , Tb 3+ ). ,,− Therefore, Dy­(III)/Tb­(III) based on H 2 MBA can be luminescent by H 2 MBA through population of the 4 F 9/2 and 5 D 4 resonant levels of the emitting lanthanides. The emission spectra diagram for solid-state luminescence at room temperature and CIE 1931 chromaticity coordinates for 1 – 4 are shown in Figure .…”

A Hybrid Materials Approach for Fabricating Efficient WLEDs Based on Di‐Ureasils Doped with Carbon Dots and a Europium Complex

“…[12] The most widely investigated materials are Ln 3+ -based organic-inorganic hybrids, [13,14] including metalorganic frameworks (MOFs), [15] because of their structural variety and stability. The primary blue component originates either from the organic ligands, or from Ln 3+ ions (alone, e.g., Dy 3+ [16] , or combined, Eu 3+ /Gd 3+ , [17] Eu 3+ /Tb 3+ , [18] Eu 3+ /Tb 3+ /Gd 3+ , [19] and Eu 3+ /Tb 3+ /La 3+ [20] ). However, WLEDs in which white light is generated from a single phase rather than by multiple emitting components (i.e., several layers comprising distinct phosphors), are the most desirable ones, as reabsorption of light is minimized, color alteration and a decrease of luminous efficiency are avoided, and the device is simplified.…”