Tuning of Ratiometric Optical Thermometry in the Family of Magnetic {Nd<sub>1–<i>x</i></sub><sup>III</sup>Yb<sup>III</sup><i><sub>x</sub></i>[Cu<sub>2</sub><sup>I</sup>(CN)<sub>5</sub>]} Frameworks Showing the Large SHG Response
Yue Xin, Kunal Kumar, Jakub J. Zakrzewski, Szymon Chorąży, Koji Nakabayashi, Olaf Stefańczyk, Shin‐ichi Ohkoshi
Abstract
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 [Nd 1– x III Yb III x (2,2′-bpdo) 2 (H 2 O)][Cu 2 I (CN) 5 ]·5H 2 O ( 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 Yb 3+ 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.