# Effects of Isomorphous Substitution on Photophysical and Magnetic Properties of Complexes [Ln1‐ x Dy x (MeDPQ)2Cl3] (Ln = Y3+, Ho3+, and Er3+)

## TL;DR

This study explores how substituting Dy3+ ions in coordination compounds affects their magnetic and optical properties, revealing multifunctional materials with light absorption and emission across multiple ranges.

## Contribution

The paper introduces new insights into the effects of isomorphous substitution on the photophysical and magnetic behavior of lanthanide-based complexes.

## Key findings

- Dilution of Dy3+ with Y3+ ions altered magnetic and photophysical properties, showing paramagnetic behavior in substituted complexes.
- Ho3+ and Er3+ complexes exhibited f–f emission in visible and NIR ranges, with additional ligand-based emission bands observed.
- The substituted complex [Er0.5Dy0.5(MeDPQ)2Cl3] showed thermal stability similar to individual complexes, starting to oxidize at 410°C.

## Abstract

This work encompasses the study of magnetic, optical, and structural properties of the coordination compounds [Ln(MeDPQ)2Cl3] (Ln ─ Ho3+, Er3+, Dy3+, and Y3+; MeDPQ − 2‐methyldipyrido‐[3,2‐f:2′,3′‐h]‐quinoxaline) and substituted complexes [Ln1‐

x
Dy
x
(MeDPQ)2Cl3] (Ln = Ho3+, Er3+, and Y3+) based on them. Magnetic measurements within the range 5–300 K revealed single ion anisotropy in [Dy(MeDPQ)2Cl3], with the Curie‐Weiss temperature θ being −3.69 ± 0.03 K. Complexes of Ho3+ and Er3+ exhibited f–f emission in the visible range, while the latter was also emissive in the NIR. Dilution of the Dy3+ complex with diamagnetic Y3+ ions resulted in alterations of magnetic and photophysical properties. The substituted complexes Y0.5Dy0.5 and Y0.9Dy0.1 demonstrated paramagnetic behavior, with θ being 3.06 ± 0.12 K and 9.64 ± 0.23 K, respectively. In both cases, the emission decay times of Dy3+ changed insignificantly, 21.02 ± 0.41 µs and 14.56 ± 0.22 µs, respectively, compared to the value (18.92 ± 0.03 µs) of the individual Dy3+ complex. Additional ligand‐based emission bands were observed in the Ho3+ and Er3+ complexes at room temperature and 77 K and in the substituted complexes Ho0.5Dy0.5 and Er0.5Dy0.5 at room temperature, which were assigned to the exciplex states. The thermal stability of [Er0.5Dy0.5(MeDPQ)2Cl3] was determined to be the same as for the individual complexes, starting to oxidize at 410°C.

We present the research on the coordination compounds [Ln(MeDPQ)2Cl3] with Dy3+, Ho3+, and Er3+ ions and the solid solutions [Ln1‐

x
Dy
x
(MeDPQ)2Cl3] based on them. The investigated materials exhibited multifunctionality: they absorb light in the UV, visible, and NIR range; emit in the visible and NIR range; demonstrate weak magnetic interactions; and possess exceptional thermal stability.