Inclusion Potential, Polymorphism, and Molecular Isomerism of Metal Dibenzoylmethanates Coordinated with 2-Methylpyridine

Abstract

In this study, new complexes of metal(II) (Ni, Zn, Cd) dibenzoylmethanates (DBMs) coordinated with 2-methylpyridine (2-MePy) were prepared and studied for host properties as a function of their structure and molecular isomerism. The novel [Ni(2-MePy)2(DBM)2] complex host exists as the trans isomer in five structurally distinct phases comprising two guest-free polymorphs as well as inclusion compounds with benzene, carbon tetrachloride, chlorobenzene, and toluene. All architectures arise from van der Waals packing, the host materials having guest species located in channels or cages. The stability of inclusions correlates with the shape of the cavity space. For zinc dibenzoylmethanate only one 2-MePy unit coordinates to give the [Zn(2-MePy)(DBM)2] complex that does not exhibit inclusion properties. With cadmium dibenzoylmethanate, two polymorphic forms of the composition [Cd(2-MePy)2(DBM)2] were isolated. A metastable form contains complex molecules in the trans isomeric state, while a stable form contains cis isomers. As earlier, the ability to form clathrates was attributed only to trans-configured molecules of this type; the presence of a more stable cis form, with a trans-to-cis phase conversion enthalpy gain of as much as 17.2(6) kJ/mol, explains the failure to isolate any inclusion compounds of the Cd complex. The precedent of isolating both cis and trans isomers for the same complex of metal dibenzoylmethanate host is discussed in the context of designing novel materials where the potential for inclusion may be switched through molecular-level control of the isomeric state.

Flexible metal-organic framework compounds: In situ studies for selective CO2 capture

“…It is recognized as one of the "DBM"class of MOFs, elegantly described by Soldatov. [71][72][73][74][75][76] Interestingly, both of these materials have nearly identical gate opening pressure responses to CO 2 at 303 K. This coincidence in CO 2 adsorption behavior between two highly contrasted crystallographic structures with very different degrees of freedom available for structure transitions during gas adsorption make these two materials an ideal model system for investigating how structures respond and evolve to the adsorption of guest molecules.…”

“…However, the diffraction peak shape and position of NiBpene is different under the same partial pressures of CO 2 in pure and CO 2 /N 2 mixtures, indicating some degree of co-adsorption of N 2 . These intriguing differences in mechanisms between the two materials with such similar CO 2 adsorption/desorption isotherms offer an opportunity to study the influence of structure on adsorption selectivity in flexible MOFs.We conclude by noting that both NiBpene and NiDBM-Bpy belong to material classes where aspects of the structure can be adjusted in a controllable way [70][71][72][73][74][75][76]. Controllable aspects include the length of the linker d-spacing and consequent size of the void spaces available for CO 2 adsorption, the fineness of the powder grain morphology, and the concentration of synthetically incorporated impurity guest species that reduce the dynamically available space for CO 2 adsorption/desorption.…”

“…The DBM ligands or fragments correspond to the disks (paddle wheels) inFigure 2b. The DBM fragment has a flexible architecture that can be easy converted from one structure to another (can be planar, twisted, or bent depending on the guest molecules present) [71][72][73][74][75][76]79]. The guest species fill the residual pocket space between the DBM fragments and form van der Waals contact with each other and with the host.…”

Different coordination modes and supramolecular aggregations in copper(II) pentane-2,4-dionato compounds with 2-pyridone and 3-hydroxypyridine

“…Metal complexes of b-diketonate ligands are of interest in solid-state supramolecular chemistry mostly owing to their promise as building blocks for the design of porous and supramolecular materials with interesting electronic, magnetic, and optical properties [1][2][3][4]. Furthermore, metal complexes of b-diketonate derivatives can be good precursors in metal-organic chemical vapour deposition (MOCVD) [5].…”

Morpholine adducts of Co, Ni, and Mn benzoylacetonates: isostructurality and C–H···O hydrogen bonding

“…In the earlier times, they have mostly attracted attention due to their applications in synthetic and industrial processes such as extraction of metals, catalytic processes, preparation of metal oxide thin films, etc. Over the past 20 years, they have also attracted ever growing attention as building blocks in crystal engineering [1][2][3][4][5]. There are two main pathways for their use in the rational design of metalorganic solids-the use of functionalised diketones which can further connect into supramolecular architectures [6][7][8][9][10] and the use of metals which remain coordinationaly unsaturated after the formation of a neutral diketonate complex.…”