Tuning of Ratiometric Optical Thermometry in the Family of Magnetic {Nd1–xIIIYbIIIx[Cu2I(CN)5]} Frameworks Showing the Large SHG Response

Three-dimensional (3-D) coordination networks provide a stable framework preferable to designing materials with tunable properties by various chemical modifications, such as solvent exchange, element doping, etc. In this work, we explored extensively the 3-D cyanido-bridged heterometallic assemblies having Nd(III) and Yb(III) centers in combination with polycyanidocuprate(I) ions, that is, the family of [Nd1–xIIIYbIIIx(2,2′-bpdo)2(H2O)][Cu2I(CN)5]·5H2O (x = 0, 0.25, 0.5, 0.75, 1 (1–5); 2,2′-bpdo = 2,2′-bipyridine N,N′-dioxide) coordination networks. To form a lanthanide-incorporating molecule-based matrix, two different types of cuprate(I) moieties are spontaneously formed during crystallization, resulting in trigonal planar tricyanido and tetrahedral tetracyanidocopper(I)-based molecular anions. 1–5 exhibit optical thermometry based on near-infrared (NIR) luminescence. The relative thermal sensitivity of Nd(III)-containing 1 is considerably improved through the preparation of the analogous mixed heterometallic compounds by introducing Yb3+ ions, which also enables tunability over the operating temperature range. Since all 3-D networks crystallize within a non-centrosymmetric Cc space group, they exhibit a second-harmonic generation (SHG) phenomenon, with the signal highest among the materials based on cyanido-bridged metal assemblies (the SHG efficiency of ∼120% of the reference potassium dihydrogen phosphate). Furthermore, 1–5 show field-induced single-molecule magnet (SMM) behavior related to lanthanide(3+) ions, with a slow magnetic relaxation occurring via Raman and direct relaxation processes.