Supramolecular encapsulation of hexaaquacobalt(ii) cations in a hydrogen-bonded framework for slow magnetic relaxation and high proton conduction

Abstract

The supramolecular assembly of hexaaquacobalt(II) nitrate and a tetradentate carboxylate ligand resulted in an isolation of a cobalt hydrogen-bonded organic framework (HOF). Variable-temperature X-ray diffraction experiments reveal high thermal stability...

Metalo Hydrogen-Bonded Organic Frameworks Self-Assembled by Charge-Assisted Synthons for Ultrahigh Proton Conduction

“…To our knowledge, high-temperature single crystal measurements for HOFs, MHOFs, and supramolecular frameworks are extremely rare. 8−10 Consequently, together with the cobalt HOF, 32 the present results provide a family of rare HOFs having single crystal structures at 373 K.…”

“…Selected bond angles and lengths and possible hydrogen bonds calculated by PLATON are summarized in Tables S3 36 In comparison with the Co 2+ HOF, 32 as can be seen, the main difference is the distinct H bonds around the core cations, which leads to a dramatic change of the supramolecular networks. The previously reported Co(II) HOF is an ultramicroporous pillared-layer framework while the nonporous solids of 1 and 2 are viewed from the crystal structures (Figure 3b Although shorter H bonds, the stability is relatively weaker, revealing that supramolecular architecture plays a significant role in the thermal stability of HOF materials.…”

“…In addition, by taking advantage of the charge of metalo synthons, charge-assisted H-bonds between inorganic cations and organic anions will lead to a strengthening of the entire structure . Recently, we reported the supramolecular self-assembly of hexaaquacobalt­(II) cations and 1,2,4,5-benzenetetracarboxylic acids (H 4 tcba), giving rise to an ultra-microporous charge-assisted hydrogen-bonded organic-cobalt framework . Interestingly, the compound was found to be a bifunctional material showing field-induced single-ion magnet behavior and high proton conductivity.…”

“…30 Recently, we reported the supramolecular selfassembly of hexaaquacobalt(II) cations and 1,2,4,5-benzenetetracarboxylic acids (H 4 tcba), giving rise to an ultra-microporous charge-assisted hydrogen-bonded organic-cobalt framework. 32 Interestingly, the compound was found to be a bifunctional material showing field-induced single-ion magnet behavior and high proton conductivity. 33 Nevertheless, the remaining physical, chemical, and functional properties were not explored.…”

“…HOFs are natural supramolecular architectures constructed by the hydrogen bonds between synthons, resulting in a great advantage for proton conductivity. Due to the weak strength of hydrogen bonds, however, the thermal and water stability of these supramolecular molecular materials are weak. , To solve this problem for practical application, several approaches can be employed to construct stable HOFs, such as creating multiple hydrogen bonds, taking advantage of π–π interactions, and avoiding residual hydrogen donors/acceptors after self-assembly. , By these methods, an increasing number of functional HOFs with considerable chemical and thermal stability have been achieved. − Besides these mentioned approaches, recently, the incorporation of metal-containing synthons into the synthesis of MHOFs has also received notable interest. ,− The combination of metal inertness and extensive hydrogen bonds not only provides enhanced stability but also affords a chance for new functions, such as spin-cross-over behaviors and single-molecule magnetism . In addition, by taking advantage of the charge of metalo synthons, charge-assisted H-bonds between inorganic cations and organic anions will lead to a strengthening of the entire structure .…”