Solvent‐Mediated Transformation from Achiral to Chiral Nickel(II) Metal–Organic Frameworks and Reassembly in Solution

Abstract

Reactions of 5-nitroisophthalic acid (NO2 -H2 ip), 1,4-bis(imidazol-1'-yl)butane (bimb), and Ni(NO3 )2 ⋅6 H2 O gave rise to four metal-organic frameworks (MOFs), [Ni2 (NO2 -ip)2 (bimb)1.5 ]n (1), [Ni4 (NO2 -ip)3 (bimb)2 (OH)2 (H2 O)]n ⋅(CH3 CH2 OH)0.5 n (2), [Ni(NO2 -ip)(bimb)1.5 (H2 O)]n ⋅(H2 O)n ⋅(CH3 CH2 OH)0.5 n (3), and [Ni(NO2 -ip) (bimb)(μ-H2 O)]n ⋅(H2 O)n (4). The metal/ligand ratio, pH value, and solvent exerted a subtle but crucial influence on the formation of complexes 1-4, which possess different visual color and crystal structures. Complex 1 exhibits a twofold interpenetrating 3D pillared bilayer framework composed of binuclear and mononuclear Ni(II) units, whereas complex 2 is a 3D chiral network that consists of asymmetric tetranuclear Ni(II) units. Complexes 3 and 4 are 3D layer-pillared frameworks that consist of mononuclear Ni(II) ions and a 3D six-connected network of μ-water-bridged dinuclear Ni(II) units, respectively. Interestingly, achiral 4 can be transformed into chiral 2 by using a solvent-mediated single-crystal-to-single-crystal process without any chiral auxiliary. Magnetic analyses of 2 and 4 show the occurrence of antiferromagnetic interactions. Complex 3 is difficult to obtain directly as a single solid phase, but it can be homogeneously formed by solvent-mediated transformations from 1, 2, and 4.

Multistep Structural Transformation of a Magnetic Metal–Organic Framework: Possible Transformation Mechanism, Form Evolution, and Magnetic Properties

“…In comparison with DRST, the SSST process is more often observed in MOFs, and most of the transformation is trigged by experimental physical or chemical stimuli, such as light, − heat, − pressure, − solvent-molecule exchange or loss, ,− postsynthesis modification, ,,,− and oxidation/reduction. ,− Unlike SSST, which usually causes slight structural changes, a DRST transformation is usually accompanied by the breaking and forming of coordinate bonds as well as the formation of several intermediates. This makes it very difficult to study the mechanism of structural transformation, especially one that involves multistep structural transformation. − …”

A Family of Metal–Organic Frameworks with a New Chair-Conformation Resorcin[4]arene-Based Ligand: Selective Luminescent Sensing of Amine and Aldehyde Vapors, and Solvent-Mediated Structural Transformations

“…This transformation is proposed to probably be a solvent-induced structural transformation, which may involve the dissolution of 4 and recrystallization of 3 in DMF. Very recently, a striking single-crystal-to-single-crystal (SCSC) transformation associated with the dissolution and recrystallization process from the achiral [Ni­(NO 2 -ip)­(bimb)­(μ-H 2 O)] n ­· (H 2 O) n to chiral [Ni 4 (NO 2 -ip) 3 ­(bimb) 2 (OH) 2 ­(H 2 O)] n ­· (CH 3 CH 2 OH) 0.5 n (NO 2 -H 2 ip = 5-nitroisophthalic acid and bimb = 1,4-bis­(imidazol-1′-yl)­butane) has been observed . It should be mentioned that no single crystals of 3 were achieved when raw materials were treated in DMF at 120 °C.…”

Recent Progress in Asymmetric Catalysis and Chromatographic Separation by Chiral Metal–Organic Frameworks

“…The INligands associated with the adjacent 1D secondary building units (SBUs) resulted in a three-dimensional (3D) chiral MOF with a pcu framework containing irregular channels. A few more new studies on spontaneous resolution have been reported [75][76][77][78][79].…”