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.