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Coordination network–based magnets composed of uncommon Kramers ions (Nd(III) and Sm(III)) exhibit emissive properties and may realize diverse magneto–optical applications. Herein we characterize cyanido-bridged robust networks possessing lanthanide ions combined...

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Self-assembly Fe II complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4'-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [Hg II (XCN) 4 ] 2À (X = S or Se) formed six new highdimensional frameworks with the general formula of 4; and L = Tmp, m/X = 1/Se, 4-Se). 1, 3, and 3-Se show an intense subterahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the Fe II ions and crystallization organic molecules. In addition, crystals of 1, 4, and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal Fe II À Hg II systems are promising platforms to construct sub-THz absorbers.

Research on isomers is highly desirable due to their prospective role in better understanding of physicochemical properties of similar systems and further development of multifunctional molecular materials. Iron(II) and tetra(thiocyanato)mercury(II) ions self-assembled in the presence of 2-acetylpyridine (2-acpy) excess to form two {[Fe(2-acpy)][Hg(μ-SCN)4]} n isomers: two-dimensional (2D) centrosymmetric layers with folded ring structural motifs (1) and three-dimensional (3D) chiral networks with right- or left-handed {···Fe-NCS-Hg-SCN···}∞ helixes (2). New methods of designing and synthesizing functional thiocyanate-bridged materials have been proposed. In addition, the similarity between 1 and 2 allowed for the description of subtle changes in IR and UV–visible spectra. Moreover, 2 shows spontaneous resolution, and it crystallizes in the noncentrosymmetric space group P21, leading to the occurrence of nonlinear optical activity in circular dichroism studies and second harmonic generation (SHG). At room temperature, the SH susceptibility for powder sample 2 reached 6.0 × 10–11 esu. Ab initio calculations indicated the electric polarization vector and the crystallographic twofold screw axis pass through the aromatic ring. Magnetic studies for 1 and 2 revealed high-spin iron(II) with zero-field splitting at low temperatures. Analysis of magnetic data gave |D| = 37.45 cm–1, |E/D| = 5.59 cm–1, and ⟨g⟩ = 2.15 for 1, |D| = 36.78 cm–1 , |E/D| = 4.92 cm–1, and ⟨g⟩ = 2.18 for 2, and information about the orientation of magnetic anisotropy vectors for both compounds.

The design and synthesis of high-dimensional materials based on secondary building blocks (SBUs) play a pivotal role in the further development of functional molecular materials. Herein, the self-assembly of Cu­(II) ions, pyrazole (Hpz), and octacyanidometallate­(IV) anions in the presence of water produced two new isostructural three-dimensional systems {[Cu3(μ3-OH)­(μ-pz)3(H2O)3]2[M­(CN)8]}·nH2O (M = W, 1, and Mo, 2). 1 and 2 consist of trinuclear triangle copper­(II) (TTC) SBUs and octacyanidometallates­(IV). At room temperature, both assemblies display strong antiferromagnetic interactions within the TTC entities with an average CuII···CuII isotropic magnetic coupling constant of about −145 cm–1. Moreover, a detailed analysis of magnetic data revealed the presence of spin frustration with antisymmetric magnetic exchange-coupling constants of around +32 and +46 cm–1 for 1 and 2, respectively. Finally, quantum chemical calculations explained their magnetic and optical properties.

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The spin‐crossover (SCO) and charge‐transfer (CT) phenomena, the switching processes between two distinguishable magnetic states, are promising for developing materials capable of sophisticated memory and sensing functionalities. The majority of SCO systems are based on iron(II) complexes. However, cobalt(II)‐2,2′:6′,2′′‐terpyridine (terpy) systems emerge as a promising alternative. In this work, new complex salts [CoII(terpy)2]2[MoIV(CN)8] ⋅ 15H2O, Co2Mo(H2O), and [CoII(terpy)2]3[WV(CN)8]2 ⋅ 12H2O, Co3W2(H2O) were synthesized and physiochemically characterized. Structural studies for both compounds revealed [Co(terpy)2]2+ layers pillared by octacyanidometallate anions and completed with water molecules between them. Magnetic studies confirmed that the (de)solvated phases of both complexes exhibit partial SCO on the cobalt(II) centers: CoII−LS (SCo(II)‐LS=1/2)↔CoII−HS (SCo(II)‐HS=3/2). Moreover, handling dehydrated samples in a high‐humidity environment leads to partial recovery of previous magnetic properties via humidity‐induced SCO for Co2Mo: CoII−HS→CoII−LS, and the new phenomenon of isothermal humidity‐activated charge‐transfer‐induced spin transition, which we define here as HACTIST, for Co3W2: CoII−HS⋅⋅⋅WV (SCo(II)‐HS=3/2 and SW(V)=1/2)→CoIII−LS⋅⋅⋅WIV (SW(IV)=0 and SCo(III)‐LS=0). These comprehensive studies shed light on the water‐solvation‐dependent spin transitions in Co(II)‐octacyanidometallate(IV/V) complexes.