Effects of Isomorphous Substitution on Photophysical and Magnetic Properties of Complexes [Ln 1‐ x Dy x (MeDPQ) ₂ Cl ₃ ] (Ln = Y ³⁺ , Ho ³⁺ , and Er ³⁺ )

This work encompasses the study of magnetic, optical, and structural properties of the coordination compounds [Ln(MeDPQ) 2 Cl 3 ] (Ln ─ Ho 3+ , Er 3+ , Dy 3+ , and Y 3+ ; MeDPQ − 2‐methyldipyrido‐[3,2‐f:2′,3′‐h]‐quinoxaline) and substituted complexes [Ln 1‐ x Dy x (MeDPQ) 2 Cl 3 ] (Ln = Ho 3+ , Er 3+ , and Y 3+ ) based on them. Magnetic measurements within the range 5–300 K revealed single ion anisotropy in [Dy(MeDPQ) 2 Cl 3 ], with the Curie‐Weiss temperature θ being −3.69 ± 0.03 K. Complexes of Ho 3+ and Er 3+ exhibited f – f emission in the visible range, while the latter was also emissive in the NIR. Dilution of the Dy 3+ complex with diamagnetic Y 3+ ions resulted in alterations of magnetic and photophysical properties. The substituted complexes Y 0.5 Dy 0.5 and Y 0.9 Dy 0.1 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 Dy 3+ 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 Dy 3+ complex. Additional ligand‐based emission bands were observed in the Ho 3+ and Er 3+ complexes at room temperature and 77 K and in the substituted complexes Ho 0.5 Dy 0.5 and Er 0.5 Dy 0.5 at room temperature, which were assigned to the exciplex states. The thermal stability of [Er 0.5 Dy 0.5 (MeDPQ) 2 Cl 3 ] was determined to be the same as for the individual complexes, starting to oxidize at 410°C.