Two Unexpected Temperature-Induced Supermolecular Isomers from Multi-Topic Carboxylic Acid: Hydrogen Bonding Layer or Helix Tube

Under ambient conditions or 160 °C, two supramolecular isomers, namely [(H4PTTA)(H2O)2(DMF)] and [(H4PTTA)(H2O)3]··Guest (1-L and 1-H, H4PTTA = N-phenyl-N′-phenyl bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide tetra-carboxylic acid, Guest = DMF and H2O), were obtained through the reaction of H4PTTA in a mixture of H2O and dimethylformamide. The single crystal structures reveal the temperature-dependent supramolecular isomerism derived from the torsion of semi-rigid of H4PTTA. The 1-L prepared at room temperature is a hydrogen bond based achiral layer, while the hydrothermal synthesized 1-H is isomer resulted in an H-bond-based chiral tubes-packed supramolecular framework.

Polymorphism and Supramolecular Isomerism: The Impasse of Coordination Polymers

The chapter presented hereafter, outlines the narrow link between chemistry and crystallography that impelled the identification of polymorphism and provided a priceless grounding to understand structure-properties relationship. It was initially conceived for organic substances but actually embraced by metal–organic products, especially in the study of coordination polymers. All of the technologic advances have provided profound insights on the control of crystal structures formation revealing that any applied stimulus over a substance can undergo a structural transformation. This has led to the implementation of several methodologies in the industrial and academic segment shedding light on the source of hitherto, not well understood results.

Polymorphs of phenazine hexacyanoferrate(II) hydrate: supramolecular isomerism in a 2D hydrogen-bonded network

The crystal structures of two polymorphs of a phenazine hexacyanoferrate(II) salt/cocrystal, with the formula (Hphen)3[H2Fe(CN)6][H3Fe(CN)6]·2(phen)·2H2O, are reported. The polymorphs are comprised of (Hphen)2[H2Fe(CN)6] trimers and (Hphen)[(phen)2(H2O)2][H3Fe(CN)6] hexamers connected into two-dimensional (2D) hydrogen-bonded networks through strong hydrogen bonds between the [H2Fe(CN)6]2− and [H3Fe(CN)6]− anions. The layers are further connected by hydrogen bonds, as well as through π–π stacking of phenazine moieties. Aside from the identical 2D hydrogen-bonded networks, the two polymorphs share phenazine stacks comprising both protonated and neutral phenazine molecules. On the other hand, the polymorphs differ in the conformation, placement and orientation of the hydrogen-bonded trimers and hexamers within the hydrogen-bonded networks, which leads to different packing of the hydrogen-bonded layers, as well as to different hydrogen bonding between the layers. Thus, aside from an exceptional number of symmetry-independent units (nine in total), these two polymorphs show how robust structural motifs, such as charge-assisted hydrogen bonding or π-stacking, allow for different arrangements of the supramolecular units, resulting in polymorphism.

Self-assembly and supramolecular isomerism in 1D metal-organometallic networks based on transition-metal assemblies from 1,1’-ferrocene-dicarboxylic acid and ancillary nitrogen heterocycle ligands

A series of eight novel 1D metal-organometallic networks of Cu(II)/Co(II)/Cd(II) and Zn(II) bearing bidentate ligands 1,10’-phenanthroline (1,10’-phen), 5,5’-dimethyl-2,2’-bipyridine (5,5’-diMe-2,2’-bipy) and terminal ligand 4-stilbazole (4-Stb) were prepared by hydrothermal synthesis and...

Clues from cocrystals: A ternary solid, polymorphism, and rare supramolecular isomerism involving resveratrol and 5-fluorouracil

We describe a supramolecular synthesis of a ternary cocrystal involving resveratrol and 5-fluorouracil (5-fu) with trans-bis(4-pyridyl)ethylene (bpe). We also have discovered a polymorph of a binary cocrystal involving on 5-fu...

Supramolecular isomerism between cyclodimeric and sinusoidal 1D coordination polymers: competition of tunable argentophilic vs electrostatic interactions

Systematic supramolecular isomerism between metallacyclodimeric species and sinusoidal 1D coordination polymers was observed. Slow diffusion of AgX (X- = NO3-, BF4-, ClO4-, and PF6-) with 1,3-bis(dimethyl(pyridin-4-yl)silyl)propane afforded 28-membered metallacyclodimers [AgL]2(X)2...

Disappeared supramolecular isomer reappears with perylene guest

Among different types of polymorphism, disappearing polymorphism deals with the metastable kinetic form which can not be reproduced after its first isolation. In the world of coordination polymers (CPs) and metal–organic frameworks (MOFs), despite the fact that many types of supramolecular isomerism exist, we are unaware of disappearing supramolecular isomerism akin to disappearing polymorphism. This work reports a MOF with dia topology that could not be reproduced, but subsequent synthesis yielded another supramolecular isomer, a double-pillared-layer MOF. When perylene was added in the same reaction, the disappeared dia MOF reappeared with perylene as a guest in the channels. Interestingly, the photoluminescence of the dia MOF with a perylene guest is dominated by the emission of the guest molecule. The influence of guest molecules on the stabilization of the supramolecular isomers of a MOF opens up a strategy to access MOFs with different structures.