Isotope and Temperature Dependence of Dual Emission in a Mononuclear Ruthenium(II) Polypyridyl Compound

Abstract

Detailed photophysical measurements on a series of [Ru(bpy)2(L)] n + complexes, which are deuterated to varying degrees are reported, where bpy is 2,2‘-bipyridyl and L is 3-(pyrazin-2-yl)-1,2,4- triazole (Hpztr) or 3-(pyridin-2-yl)-1,2,4-triazole (Hpytr). For the pyridinyltriazole complexes, deuteration of bpy leads to a doubling of the emission lifetime, while deuteration of the triazole ligand has no effect on the emission lifetime. For the complex containing the protonated pyrazinyltriazole ligand, deuteration of bpy does not affect the emission lifetime, but the lifetime is strongly affected by the deuteration of the triazole-containing ligand. These observations indicate that in the pyridinyltriazole complexes the emitting state is bpy based, while for the complex containing the protonated pyrazinyltriazole ligand the emission is pyrazine based. For the compound containing the deprotonated pyrazinyltriazole ligand a remarkable insensitivity of the emission lifetime to deuteration is observed. Time-resolved resonance Raman data clearly indicate that the emitting triplet state is bpy based at room temperature when the triazole is deprotonated and switches to being pyrazine based on protonation. Variable temperature emission studies on the deprotonated complex reveal a remarkable dual emission between 120 and 200 K. The two emitting states exhibit different lifetime dependences on temperature. It is proposed that the presence of these two, weakly coupled emitting states, one bpy and one pyrazine based, is responsible for the relative insensitivity of the emission lifetime of the deprotonated pyrazinyltriazole complex to deuteration.

Engineering Tunable Single and Dual Optical Emission from Ru(II)–Polypyridyl Complexes through Excited State Design

“…There is experimental evidence for the 124PZAZ complex ion, 30,31 which supports this hypothesis and shows that the second emission band is associated with a structural relaxation within the X ligand. Therefore, it is important to understand the molecular geometry and Table S5.…”

“…[18][19][20][21][22][23][24][25][26] The further design and control of optical materials based on Ru-polypyridyl will require an explanation and predictive prescription for, perhaps, their most intriguing optical aspect -the observation of single and dual optical emission. [27][28][29][30][31][32][33][34][35][36][37][38] In general, dual emission properties in organometallic complexes may arise from two different 3 MLCT states involving different ligands, from types of states e.g. 3 MLCT, 3 IL or 3 LL'CT or based on different metals in dissymmetric bimetallics complexes.…”

“…30 temperature (620 nm) and dual emitter at low temperature (590 and 700 nm). The dual emission properties of 124PZAZ are described in Scheme 1 which helps to explain the temperature dependence of the second emission band 30,31 ; therefore, the 124PZAZ complex ion serves as a reference compound in our study.…”

So-called “dual emission” for 3MLCT luminescence in ruthenium complex ions: What is really happening?

“…Another possibility for species that might go unrecognized, are tautomeric species that involve proton transfer or species that may be protonated or deprotonated. Those have been described as showing dual emission [27]. More commonly, "switchable" luminescence is not of dual character, but simply of "on-off" behavior, frequently involving photoisomerization.…”

Effect of Isotopic Substitution on Elementary Processes in Dye-Sensitized Solar Cells: Deuterated Amino-Phenyl Acid Dyes on TiO2

“…Here, we study how deuteration-the most readily achievable type of isotopic substitution [31][32][33]can change the nuclear dynamics effect on light absorption, electron injection, and recombination in NK1 and NK7 dyes on TiO 2 . The paper is organized as follows: in Section 2, theoretical and computational methods are described, Section 3 presents the results of comparative studies of the dynamical effects in deuterated and non-deuterated dyes, and Section 4 concludes.…”