A metal–organic framework with three cavities based on three-coloured square tiling derived from a cyclobutane constructed in the solid state

Abstract

The unsymmetrical tetratopic ligand rctt-1,2-bis(3-pyridyl)-3,4bis(4-pyridyl)cyclobutane self-assembles with zinc(II) nitrate to form a 2D metal-organic framework with three distinct cavities.Metal-organic frameworks (MOFs) are one of the most studied class of compounds in the area of materials science and supramolecular chemistry. 1 Tremendous interests in MOFs are attributed to scientific and technological applicability (e.g. gas storage, 2-4 catalysis, 5 anion 6 and guest 7 exchange, drug delivery). [8][9][10] Recent studies have reported biporous MOFs (i.e. MOFs with two distinct pores) being able to accommodate different guest molecules in different channels. 11-18 A very rare example of a triporous MOF supported by calix[4]arenes has just been reported. 19 Indeed, MOFs with more than one type of cavity can be considered to represent an entry to a new generation of MOF-based materials with applications in areas such as separation processes that, in principle, allow the recognition and storage of compounds unable to coexist (e.g. acid/base, oxidizers/ reducers). 11 Understanding how to design molecular building units that self-assemble to form MOFs with more than one cavity type can, thus, be considered to represent an important area of development in the advancing field.In recent years, we have demonstrated how [2 + 2] photodimerisations can be engineered in the organic solid state. 20 Specifically, we have shown that molecular cocrystals can be utilized as reaction media wherein synthetic templates arrange olefins for intermolecular [2 + 2] photodimerisations using principles of hydrogen-bond-driven self-assembly. The cocrystals react to form cyclobutanes lined with pyridyl groups that form stereospecifically, in quantitative yield, and in gram amounts. We have also shown that the resulting cyclobutanes can be utilised as polytopic ligands 21 to form MOFs with up to two different cavities, 15 helical coordination polymers, 22 MOFs with functionalized pores, 23 as well as related metal-organic polygons 24 and polyhedra. [25][26][27] Herein, we report a MOF with three different cavities; 28 namely, [Zn 2 (3,4 0 -tpcb) 2 (NO 3 ) 4 (H 2 O) 4 ] N (1) (where 3,4 0 -tpcb = rctt-1,2-bis(3-pyridyl)-3,4-bis(4-pyridyl)cyclobutane). The ligand 3,4 0 -tpcb has been prepared in a templated solid-state synthesis stereospecifically and in quantitative yield (Scheme 1). 29 In the MOF, the cyclobutane, which is unsymmetrical, binds four

Solid-state polymerisation via [2+2] cycloaddition reaction involving coordination polymers

“…In many cases, they are ended up in higher dimensional structures. [107][108][109][110][111][112][113]…”

Activating [4 + 4] photoreactivity in the solid-state via complexation: from 9-(methylaminomethyl)anthracene to its silver(i) complexes

“…This can in principle be modified and a favourable geometry obtained by coordination to metal ions. Examples can be found in the literature in the case of [2+2] photocycloadditons, 20 but, to the authors' knowledge, this approach has never been tried with anthracene derivatives. We reacted MAMA with silver(I) salts and obtained solids in which, due to coordination to the metal ions, the potentially reactive groups could be locked in place in a favourable geometric arrangement.…”

Features of styryl dye crystal packings and their influence on [2 + 2] photocycloaddition reaction with single crystal retention

“…8,16 Many reactions of cycloaddition are known in organic chemistry, for instance -[2 + 3] cyloaddition, 47 [3 + 4] cycloaddition, 48 [4 + 2] cycloaddition. Many examples of pre-organized dimeric pairs are described in the literature via the coordination of the initial ethylene systems with metal cations 11,30,32,34,38,40,43,50 or the formation of hydrogen bonds between the components, 7,9,10,12,14,15,17,20,21,[23][24][25]29,30,40,41,46,50 as well as entering two structural units in cavitand cavitycyclodextrins, calixarenes, cucurbit [8]uril, nanocages. Whereas, PCA represents a temperature independent process.…”

“…Molecular design is one of several methods to achieve this. Many examples of pre-organized dimeric pairs are described in the literature via the coordination of the initial ethylene systems with metal cations 11,30,32,34,38,40,43,50 or the formation of hydrogen bonds between the components, 7,9,10,12,14,15,17,20,21,[23][24][25]29,30,40,41,46,50 as well as entering two structural units in cavitand cavitycyclodextrins, calixarenes, cucurbit [8]uril, nanocages. 17,35,36,39,40 Another approach to create the "pre-organized" dimeric pair is only possible for the PCA reaction in the solid state.…”