Controlling molecular chirality by external stimuli is of great significance in both fundamental research and technological applications. Herein, we report a high-temperature (384 K) molecular ferroelectric of a Cu(II) complex whose spontaneous polarization can be switched associated with flipping of molecular chirality. In this two-dimensional perovskite structure, the inorganic layer is separated by (NH3(CH2)2SS(CH2)2NH3)2+ organic cations skewed in a chiral conformation (P- or M-helicity in an individual crystal). As the stereodynamic disulfide bridge determines the molecular dipole moment along the polar axis, the chiral organic cation can be converted to its enantiomer as a consequence of an electric field-induced shift of the S–S moiety relative to its screw axis during the ferroelectric switching. The variation of the molecular chirality is examined with single-crystal X-ray diffraction and circular dichroism spectra. The simultaneous switching of molecular chirality and spontaneous polarization in this perovskite ferroelectric may lead to novel chiral electronic phenomena.

Prussian Blue analogues (PBAs) with unusual properties such as spin 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, {[CoII(TPA)]3­[FeIII(CN)6]­[CoIII(CN)6]}­3DMF·7H2O (1·S) and {[CoII(TPA)]3­[FeIII(CN)6]­[CoIII(CN)6]}­2DMF·1H2O (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 (1·S) showed reversible thermochromism accompanied by metal-to-metal electron transfer (MMET). Compound 1·S crystallizes in the monoclinic space group P21/c with a = 17.2227(8), b = 23.1538(10), c = 22.5074(12) Å, β = 90.388(5)°, V = 8975.17(7) Å3, and Z = 4. Compound 2·S crystallizes in the tetragonal space group P4/nnc with a = b = 33.1374(5), c = 31.7381(10) Å, V = 34851.2(15) Å3, and Z = 16. In both isomers, the 3D structures are constructed with heptanuclear heterometallic units, {[CoII(TPA)]6­[FeIII(CN)6]}9+, which are interconnected by [Fe­(CN)6]3– and [Co­(CN)6]3– anions in the trans μ-bridge mode. This work may provide a new perspective for the design of functional PBAs materials.

A tetradentate ligand 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (TPPE) was adopted to construct a two-dimensional coordination polymer that incorporated valence tautomerism and luminescence, and the synergistic effect arising from energy transfer from TPPE to...

Two iron(II) compounds with the general formula of [Fe(phen‐TPE)2(NCX)2] ⋅ Y (phen‐TPE=3‐(tetraphenylethylene)‐1,10‐phenanthroline; X=S and Y=2DMF for 1 ⋅ 2DMF; X=Se and Y=DMF for 2 ⋅ DMF) were synthesized and characterized by single‐crystal X‐ray crystallography and magnetic measurements. Both compounds exhibited thermal‐induced complete one‐step spin‐crossover (SCO) behavior with the critical transition temperatures of 210 K and 260 K for 1 ⋅ 2DMF and 2 ⋅ DMF, respectively. The SCO behavior of these two isomorphic compounds depended significantly on robust intermolecular π⋅⋅⋅π interactions, NCX− groups and solvent molecules.