Isomerism in double-pillared-layer coordination polymers – structures and photoreactivity

Abstract

The existence of isomerism in coordination polymeric structures offers opportunities to understand structure-function relationships. Herein the serendipitous isolation is reported of two isomeric double-pillared-layer coordination polymeric structures arising from two different types of carboxylate bonding of benzene-1,4-dicarboxylate ligands to zinc(II), which constitutes a new type of structural isomerism. The different bonding modes not only alter the shape and size of the pores, but also the nature of interpenetration and photoreactivity. Although two trans,cis,trans-bpeb ligands with conjugated olefin bonds are aligned in close proximity in both of the structures, one isomer undergoes a double [2 + 2] cycloaddition reaction and the second isomer only offers an incomplete single cycloaddition product. This work demonstrates how small changes in the structural connectivity can have an impact on the overall structural, physical and chemical properties of such materials.

Solvent‐Mediated Synthesis of Cyclobutane Isomers in a Photoactive Cadmium(II) Porous Coordination Polymer

“…[17][18][19][20][21][22][23][24][25] Frameworks that undergo photodimerization through cycloaddition have also displayed favorable gas separation, fluorescence-switching and nitrosensing properties. [26][27][28][29][30][31] Thel igand 1,4-bis[2-(4-pyridyl)ethenyl]benzene (bpeb, Scheme 1) is often used in the synthesis of photoactive MOFs since it has two C=Colefinic bonds.T wo bpeb ligands can align in either an out-of-phase or an in-phase fashion. [20] If Schmidtst opochemical postulates are satisfied in ac rystal containing either arrangement, this could result in the formation of either one or two cyclobutane ring units, respectively,a nd thus lead to the synthesis of two isomeric cycloaddition products (Scheme 2).…”

“…[14][15][16] Metalorganic frameworks (MOFs) and coordination polymers (CPs) have been widely used to control the arrangement of organic molecules in the solid state due to their versatile but highly predictable geometries. [26][27][28][29][30][31] Thel igand 1,4-bis[2-(4-pyridyl)ethenyl]benzene (bpeb, Scheme 1) is often used in the synthesis of photoactive MOFs since it has two C=Colefinic bonds.T wo bpeb ligands can align in either an out-of-phase or an in-phase fashion. [26][27][28][29][30][31] Thel igand 1,4-bis[2-(4-pyridyl)ethenyl]benzene (bpeb, Scheme 1) is often used in the synthesis of photoactive MOFs since it has two C=Colefinic bonds.T wo bpeb ligands can align in either an out-of-phase or an in-phase fashion.…”

Disappeared supramolecular isomer reappears with perylene guest

“…On the other hand, supramolecular isomerism, a phenomenon which is quite distinct from polymorphism, exists in coordination polymers (CPs) and metal-organic frameworks (MOFs) (Hennigar et al, 1997;Moulton & Zaworotko, 2001). Since described by Zaworotko in 1997, a number of examples for various types of supramolecular isomerism have been reported (Zhang et al, 2009;Park et al, 2014cPark et al, , 2015Park et al, , 2018Park et al, , 2016Park et al, , 2019Karmakar et al, 2017;Barnett et al, 2002;Hu et al, 2012;Blake et al, 2001;Manna et al, 2008;Poplaukhin & Tiekink, 2010;Panda et al, 2013;Ju et al, 2016). Interestingly, a 'disappearing supramolecular isomer' in CPs and MOFs is not known, unlike disappearing polymorphs in organic solids.…”

“…1(a) and 1(b)]. Further, two more isomers are possible for the double-pillared-layer compounds arising from the bdc ligand coordination modes in the [Zn(bdc)] layers (Park et al, 2018).…”

Photochemical cycloaddition and temperature-dependent breathing in pillared-layer metal–organic frameworks

“…To keep olefin bonds in close proximity while still maintaining the high porosity of the materials, designing pillared-layer MOFs in which the cycloaddition reactions happen between the pillars, has been proved to be a viable strategy. Recently, significant progress has been made by smartly using pillar pair, rather than single pillar, for porous MOF construction and functionalizing them photochemically with exquisite control [25][26][27][28][29]. The MOFs after 100% photodimerization are still in single crystal form, providing a precise platform to study the materials' properties in gas separation [28] and sensing [30,31], etc.…”