Supramolecular Isomerism and Polyrotaxane-Based Two-Dimensional Coordination Polymers

Abstract

Different types of structural connectivities, topologies, and geometrical variations are possible for a given formula unit in coordination polymers (CPs) and metal–organic frameworks (MOFs) structures. This is termed supramolecular isomerism, similar to the isomerism observed in coordination complexes and organic molecules. The supramolecular isomers may exhibit different physical properties and chemical reactivities. Herein a bent dicarboxylate (sdb), a long dipyridyl spacer ligand (bpeb), and Co­(II) have been used to construct two-dimensional (2D) sheets made of wheels and axles. Depending upon the experimental conditions used, seven CPs (1–7) which have the same repeating unit [Co2(bpeb)­(sdb)2] based on a paddlewheel structure have been isolated: a non-interpenetrated 2D sheet (1), two distortional supramolecular isomers (2 and 3), one mutually inclined interpenetrated three-dimensional structure (4), two other compounds isotypical to 2 but with two different guest solvents (5 and 6), and finally 7, a polymorph of 2. It is rather intriguing that such a simple composition can exhibit such diverse solid state structures. The magnetic properties of 2 and 3 have been discussed.

Humidity-Induced Structural Transformation in Pseudopolymorph Coordination Polymers

“…The solvent is another key factor that can change the crystal structure. Solvents can accept several roles in the structure of CPs, for example, ligand, guest, both ligand and guest, or template. − Acceptance of these roles by solvents not only affects the final structure but also affects the morphology, coordination environment of the metal center, dimension and topology, − conformation of the ligand, , pore size of the structure, , and formation of supramolecular isomers. , …”

Synthesis, structures and magnetic properties of isoreticular polyrotaxane-type two-dimensional coordination polymers

“…This polyrotaxane entanglement has been observed in several 2D structures before. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] By virtue of X-ray crystallographic symmetry, bpy ligand is at the centre of this square cavity. The total potential solvent accessible area volume as calculated by PLATON in 1 is 288.3Å 3 which is 7.6% of the unit cell volume 3809.5Å 3 despite two-fold interpenetration.…”

“…[19][20][21][22][23][24][25] Recently, we reported several supramolecular isomers in polyrotaxane-type CPs of Zn(II) and Co(II) using a bent ligand, 4,4 0 -sulfonyldibenzoate (sdb, Scheme 1) and a long linear spacer ligand, 1,4-bis[2-(4 0 -pyridyl)ethenyl]benzene (bpeb). 26,27 The polyrotaxane-type Co(II) CPs show typically antiferromagnetic behaviour due to the long spacer ligand bpeb which prevents the neighbouring paddlewheel Co(II) coming closer in the solid state structures. Hence we have employed shorter bipyridyl spacer ligands namely 4,4 0 -bipyridyl (bpy) and 4,4 0 -bipyridyl ethylene (bpe) to synthesize similar polyrotaxane CPs and investigated their magnetic behaviour (Scheme 1).…”

The Impact of Charge‐Distribution on Photochromic Properties in 1D Coordination Polymers

“…For example, Kim and co‐workers reported an example of controlling the position of targeted functional groups in the porous coordination framework based on ligand‐originated isomerization, which can be fine‐tuning of the adsorption properties through varying the spatial orientation of the substituent groups . However, most examples have dealt with topologies of structure and modulation the adsorption properties …”