Architectural Isomerism in the Three-Dimensional Prussian Blue Analogue {[Co-II(TPA)](3)[Fe-III(CN)(6)][Co-III(CN)(6)]}: Synthesis, Crystal Structures, and Magnetic Properties

Prussian Blue analogues (PBAs) with unusual properties such as spill crossover (SCO) and metal-to-metal electron transfer (MMET) are of great interest. However, the construction of new three-dimensional (3D) PBAs is a formidable challenge. Herein, two mixed-valence 3D PBAs, {[Co-II(TPA)](3)-[Fe-III(CN)(6)][Co-III(CN)(6)]}3DMF center dot 7H(2)O (1.S) and {[Co-II(TPA)](3)[Fe-III(CN)(6)]-[Co-III(CN)(6)]}2DMF center dot 1H(2)O (2.S) (TPA = tris(2-pyridylmethyl)amine, DMF = N,N-dimethylformamide), were synthesized by a solvothermal method. Complexes 1 and 2 are architectural isomers with different crystal structures, electronic absorption spectra, and magnetic properties, one of which (FS) showed reversible thermochromism accompanied by metal-to-metal electron transfer (MMET). Compound 1.S crystallizes in the monoclinic space group P2(1/c) with a = 17.2227(8), b = 23.1538(10), c = 22.5074(12) angstrom, beta = 90.388(5)degrees, V = 8975.17(7) angstrom(3), and Z = 4. Compound 2.S crystallizes in the tetragonal space group P4/nnc with a = b = 33.1374(5), c = 31.7381(10) angstrom, V = 34851.2(15) angstrom(3), and Z = 16. In both isomers, the 3D structures are constructed with heptanuclear heterometallic units, {[Co-II(TPA)](6)[Fe-III(CN)(6)])(9+), which are interconnected by [Fe(CN)(6)](3-) and [Co(CN)(6)](3-)anions in the trans mu-bridge mode. This work may provide a new perspective for the design of functional PBAs materials.