Photoluminescence of Mn<sup>2+</sup> in the Borosulfate Zn[B<sub>2</sub>(SO<sub>4</sub>)<sub>4</sub>] : Mn<sup>2+</sup>—A Tool to Detect Weak Coordination Behavior of Ligands
Lukas M. Träger, Leonard C. Pasqualini, Hubert Huppertz, Jörn Bruns, Markus Suta
Abstract
Abstract The impact of the surrounding ligand field is successfully exploited in the case of Eu 2+ to tune the emission characteristics of inorganic photoactive materials with potential application in, e.g., phosphor‐converted white light‐emitting diodes (pc‐wLEDs). However, the photoluminescence of Mn 2+ related to intraconfigurational 3d 5 –3d 5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal‐ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer‐like borosulfate ligand in the Mn 2+ ‐containing solid solutions Zn 1‐ x Mn x [B 2 (SO 4 ) 4 ] ( x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B 2 (SO 4 ) 4 ]:Mn 2+ shows orange narrow‐band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn 2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn−O bonds with values close to the Racah parameters of the free Mn 2+ ion. Overall, this strategy demonstrates that electronic control of the metal‐ligand bond can be a tool to make Mn 2+ a potent alternative emitter to Eu 2+ for inorganic phosphors.