Framework Complexes of Group 2 Metals Organized by Homochiral Rods and π···π Stacking Forces: A Breathing Supramolecular MOF

Abstract

The reactions of the potassium salts of the ligands (S)-2-(1,8-naphthalimido)propanoate (KL(ala)), (S)-2-(1,8-naphthalimido)-3-hydroxypropanoate (KL(ser)), and (R)-2-(1,8-naphthalimido)propanoate (KL(ala)*), enantiopure carboxylate ligands containing a 1,8-naphthalimide π···π stacking supramolecular tecton, and, in the case of L(ser)(-), an alcohol functional group with calcium or strontium nitrate under solvothermal conditions produce crystalline [Ca(L(ala))2(H2O)]·(H2O) (1); [Ca(L(ser))2]·(H2O)2 (2); [Sr(L(ala))2(H2O)]·(H2O)3 (3); [Sr(L(ala)*)2(H2O)]·(H2O)3 (3*); and [Sr(L(ser))2(H2O)] (5). Placing 3 under vacuum removes the interstitial waters to produce [Sr(L(ala))2(H2O)] (4) in a single-crystal to single-crystal transformation; introduction of water vapor to 4 leads to the reformation of crystalline 3. Each of these new complexes has a solid-state structure based on homochiral rod secondary building unit (SBUs) central cores. Supramolecular π···π stacking interactions between 1,8-naphthalimide rings link adjacent rod SBUs into three-dimensional structures for 1, 3, 4, and 5 and two-dimensional structure for 2. Compounds 1 and 3 have open one-dimensional channels along the crystallographic c axis that are occupied by disordered solvent. For 3, these channels close and open in the reversible single-crystal conversion to 4; the π···π stacking interactions of the naphthalimide rings facilitate this process by rotating and slipping. Infrared spectroscopy demonstrated that the rehydration of 4 with D2O leads to 3d8, and the process of dehydration and rehydration of 3d8 with H2O leads to 3, thus showing exchange of the coordinated water in this process. These forms of 3 and 4 were characterized by (1)H, (2)H, and (13)C solid-state NMR spectroscopy, and thermal and luminescence data are reported on all of the complexes.

Cyclic aromatic imides as a potential class of molecules for supramolecular interactions

“…In these complexes π-stacking interactions between 1,8-naphthalimide rings link adjacent rod-like units of secondary building blocks into two-and three-dimensional structures. 78 Interestingly, group 1 and group 2 metal ions bound to the carbonyl oxygen atoms of the naphthalimide unit contribute to the formation of complex structures. In all such cases, strong π⋯π interactions dominate in constructions of supramolecular architecture.…”

Green conversion of a three‐dimensional organometallic coordination polymer to a three‐dimensional organometallic supramolecular polymer upon mechanochemical 2‐aminopyridine addition

“…To further promote our comprehension of supramolecular architecture, it is challenging to continue the investigations on the solid‐state structural transformations of CPs . Solid‐state structural transformations involving CPs induced by light, heat, guest removal, uptake or exchange, expansion of coordination numbers, oxidation of metal centers, condensation or reactions between the ligands are very fascinating, and one of the hot topics in solid‐state chemistry . Structural transformations of CPs in the solid‐state are involving the formation and breakage of at least a chemical bond .…”

“…[17] Solid-state structural transformations involving CPs induced by light, heat, guest removal, uptake or exchange, expansion of coordination numbers, oxidation of metal centers, condensation or reactions between the ligands are very fascinating, and one of the hot topics in solid-state chemistry. [18][19][20][21][22][23][24][25][26] Structural transformations of CPs in the solid-state are involving the formation and breakage of at least a chemical bond. [27] The research for environmentally friendly and efficient chemical processes has brought forward alternative synthetic strategies, including sonochemistry, microwave reactions and reactions induced by mechanical force, also known as mechanochemical reactions.…”

A new copper(II) supramolecular coordination polymer and a dinuclear compound with multifunctional 2-amino-5-sulfobenzoic acid and flexible N-donor ligands: synthesis, structure and characterization

“…Supramolecular coordination polymers (SCPs) are assembled by noncovalent van der Waals forces, such as hydrogen bonding andstacking interactions. SCPs have aroused interest because they often share the characteristics of conventional covalent-bonded polymers and the properties originating from noncovalent interactions, such as dynamic behaviour and high degrees of internal ordered supramolecular assemblies (Reger et al, 2014 In the field of crystal engineering, organic linkers play an indispensible role in controlling the structure and tuning the functional properties of the coordination compounds (Zhou & Kitagawa, 2014;Du et al, 2013). So far, many aromatic carboxylic acids have been rationally designed and successfully applied in the construction of numerous complexes with novel structures, as well as excellent functional properties (Lin et al, 2017;Gong et al, 2017;Xu et al, 2015).…”