SHG-active NIR-emissive molecular nanomagnets generated in layered neodymium(iii)–octacyanidometallate(iv) frameworks

Abstract

Lanthanide(III) single-molecule magnets (Ln-SMMs) offer the fruitful conjunction of magnetic and photoluminescent properties originating from their single-ion anisotropy and emissive f–f electronic transitions. The flexibility of lanthanide(III)-based coordination systems is the most significant prerequisite for the generation of additional physical phenomena, including non-linear optical effects related to the lack of inversion centre. In the quest towards multifunctional molecular nanomagnets, we report heterometallic d–f layered coordination polymers, {[Nd^III₄(H₂O)₁₇(pzdo)₅][M^IV(CN)₈]₃}·9H₂O (M = Mo (1), W (2); pzdo = pyrazine-N,N′-dioxide). They crystallize in the non-centrosymmetric C2 space group due to the spontaneous resolution process, confirmed by the observation of second harmonic generation (SHG) activity. These materials exhibit UV-to-vis-light-induced near-infrared (NIR) Nd^III-centred luminescence sensitized by octacyanidometallates and organic ligand, and slow relaxation of magnetization of Nd^III complexes which was investigated by alternate-current (ac) magnetic measurements and the ab initio calculations. The observed magnetic and optical properties are sensitive to the nature of the d-transition metal centre, namely most of their features are improved upon the replacement of Mo^IV with W^IV centres. In this work, we show the generation of SHG-active NIR-emissive SMMs realized by Nd³⁺ ions inserted into hybrid layers built of inorganic [M(CN)₈]⁴⁻ and organic pzdo linkers.