Magnetic Metal–Organic Framework Exhibiting Quick and Selective Solvatochromic Behavior along with Reversible Crystal-to-Amorphous-to-Crystal Transformation

Abstract

By utilizing a flexible tetrapyridinate ligand, tetrakis(4-pyridyloxymethylene) methane(L), a novel multifunctional soft porous framework, [Co(NCS)(L)]·2HO·CHOH (1), was constructed. This framework exhibits quick and selective solvatochromic and vapochromic behavior during a reversible crystal-to-amorphous-to-crystal (CAC) transformation. Importantly, the rapid CAC transition can selectively be triggered by methanol molecules, even at low concentrations of liquid or gaseous methanol. This reproducible transition can be monitored by single-crystal and power X-ray analysis, IR, and UV-vis, which all powerfully illustrate the selectivity and sensitivity of this system. In addition, the typical magnetic behavior of single ion magnets (SIMs) has been successfully introduced into this 3D framework, and the modified dynamic relaxations have been investigated via experimental and theoretical analysis. The consistent observations of both experimental and theoretical results support that the distortions of the metal coordination environments should be responsible for the finely tuned SIM behavior.

A Two-Dimensional Metal-Organic-Framework Formed From a Cobalt(II) Ion and a Bifunctional Ligand Exhibiting Thermochromic Behavior

“…Hence, the reversible conversion of compound 1 (crystalline phase) to 2 (amorphous) through 1R (crystalline phase), can be described to occur in a crystal-to-amorphous-to-crystal (CAC) transformation process. This kind of structural transformations (i.e., CAC) were reported in the literature (Tian et al, 2014;Hu et al, 2018). The TGA curve of the parent compound 1 shows a two-step degradation, where the first step is owing to the loss of water molecules, followed by the loss of DMF molecules in the second step.…”

Thermodynamics and Electronic Properties of Heterometallic Multinuclear Actinide-Containing Metal–Organic Frameworks with “Structural Memory”

“…The “structural memory” effect makes the considered framework containing a metal in the +4 oxidation state distinct from the widely used Zr­(IV) analogs. We experimentally observed structural flexibility and dynamism of the Th-MOFs involving crystalline-to-amorphous-to-crystalline transformations upon solvent treatments. , Through single-crystal X-ray diffraction, we demonstrated that capping linker installation went through a unique intermediate, which has never been detected for any framework to date. In light of the extreme importance of proper radioactive waste administration, we envision that our studies are the first steps in attaining insights for utilizing An-based MOFs as a unique platform where chemical interactions between actinide-containing species can be fundamentally understood and expanded upon.…”

A Highly Symmetric Bimetallic-Tetracarboxylate Framework: Two-Step Crystallization and Gas Separation Properties

“…Various factors including temperature, light, solvent exchange, ,, ligands exchange/insertion, sorption of metal ions/metal clusters, ,, and pressure effect have been widely studied. Due to the existence of the cleavage and formation of metal–ligand bonds simultaneously in the solid state structure, the stepwise synthesis process is generally accompanied by the appearance of recrystallization, single-crystal-to-single-crystal (SCSC), − and even crystal-to-amorphous-to-crystal (CAC) transitions. At the same time, the crystal structure before and after the initial crystallization shows not only 0D-to-2D, 1D-to-2D, and 2D-to-3D , but also 3D-to-3D conversions.…”