Radical-Doped Crystalline Lanthanide-Based Photochromic Complexes: Self-Assembly Driven by Multiple Interactions and Photoswitchable Luminescence.

Stimuli-responsive functional materials, especially the light stimulation color change and tunable fluorescent materials, have received considerable attention because of their broad applications in smart materials. Herein, a series of lanthanide-based [Ln = Nd(III) (1), Sm(III) (2), Eu(III) (3), Gd(III) (4), Tb(III) (5), Yb(III) (6), and Lu(III) (7)] crystalline complexes were attained by simply adding the aqueous lanthanide nitrate solution to the water-soluble naphthalenediimide derivative. The obtained lanthanide-based crystalline materials not only show significant photochromism but also possess reactive organic radicals under ambient conditions. Intriguingly, photoswitchable near-infrared (NIR) fluorescence was realized in the crystalline complex 1. The structures of these crystalline materials were systematically studied to clarify the weak interaction-assisted charge-transfer process. The underlying multiple-interaction-assisted supramolecular self-assembly, the radical-doped nature, and the corresponding photochromic mechanism were thoroughly unearthed by single-crystal X-ray diffraction, in situ solid-state UV-vis diffuse reflectance, and electron paramagnetic resonance spectrometric analysis.

H/F substitution achieves high piezoelectricity in enantiomeric molecular crystals.

Here, we successfully synthesized a pair of enantiomeric molecular piezoelectric materials by H/F substitution strategy. These compounds show a large piezoelectric coefficient d33 value of 25 pC N-1 measured by the quasi-static method. A simple energy harvesting device was fabricated based on this crystal, showing great potential in piezoelectric mechanical energy harvesters.

Organic Ferroelastic with Dual-Channel Manipulation Obtained by H/F Substitution.

Ferroelastic materials with high phase transition temperature have broad application prospects in information conversion and storage, shape memory, energy conversion, hyperelasticity, etc. However, most of the current reports focus on inorganic ferroelastic materials. Inorganic ferroelastic materials have the disadvantages of high energy consumption and harmful metals, which limit their application in practical work. In contrast, organic ferroelastic materials have the advantages of structural adjustability, environmental protection, easy processing, low cost, mechanical flexibility, and so on, which have great development potential in new ferroelastic materials. Here, we have successfully designed and synthesized a pair of homochiral enantiomers [(R/S)-4-fluorobenzoic acid-2-amino-2-phenylethanol] (R- and S-F) using the chemical design strategy of H/F substitution. Compared with the non-F substitution [(R/S)-benzoic acid-2-amino-2-phenylethanol] (R- and S-H), they undergo 2F1-type ferroelastic phase transitions at 370 K. Notably, the ferroelastic domains of R/S-F can be controlled through two physical channels that are temperature and stress, showing great potential in dual-channel switches.

Modulating the ferroelectric phases in cholesteryl-based organic compounds with perfluoroalkyl tail engineering.

Here, we synthesized a series of cholesteryl-based compounds, whose phases and their transformation can be modulated by temperature and the chain length of the fluoroalkyl moieties. To our knowledge, this is the first time that the phase transition could be modulated with perfluoroalkyl tail engineering in organic single-component ferroelectric crystals.