Anion-dependent thermo-responsive supramolecular superstructures of Cu(ii) macrocycles

Abstract

This investigation highlights the role of counter anion towards the formation of thermo-responsive supramolecular assemblies of pre-defined discrete molecular Cu(ii) macrocycles. A new heteroditopic ligand (L) composed of two terminal triazolyl-pyridine units and a central pyridine-2,6-carboxamide unit connected via ethylene spacers predominantly forms dinuclear Cu(ii) macrocycles [L2Cu2]X4 (X = ClO4-, NO3-, Cl-) in the presence of respective monoanion-based Cu2+ salts. In contrast, dianionic SO42--based Cu2+ salt produces a mixture of both dinuclear [L2Cu2(SO4)2] and mononuclear [LCu(SO4)] Cu(ii) macrocycles. Importantly, detailed molecular structure determinations revealed the presence of multiple secondary interactions of the different counter anions with the corresponding macrocycles. The field emission scanning electron microscopy (FESEM) studies confirmed the ability of the individual macrocycles to further assemble upon slow evaporation of the solvent. Morphologically pure rod, sphere, and sheet-like superstructures were obtained for ClO4-, NO3-, and Cl- monoanion-based macrocycles, respectively. In contrast, a mixture of linear ribbon and microflower-like assemblies were obtained for SO42--based macrocycles. Moreover, it was found that upon heating, the rod-like assembly of [L2Cu2](ClO4)4 was gradually transformed into nanoparticles through a microparticle formation, which regenerated the rod-like assembly upon standing at room temperature. This was established from the FESEM, atomic force microscopy (AFM), and dynamic light scattering (DLS) studies.

Adaptable 2,5-bis((1,2,3-triazol-4-yl)methoxy)pyrazine ligands for the simple self-assembly of homoleptic 1D coordination polymers

“…Binucleating ligands used for supramolecular architectures have included 1,2,3-triazoles as part of the chelation domain, where copper-catalysed azide-alkyne cyclisation, CuAAC chemistry, affords a synthetically accessible route under mild conditions. [14][15][16][17] The CuAAC reaction allows the ready incorporation of functionality that can either tune the properties of the materials 18,19 or permit further functionalisation by post-synthetic modification. 20,21 Therefore, triazole incorporating ligands can be used to assemble a functionalisable backbone, for new materials that can be systematically tuned.…”

A fourfold interpenetrating three-dimensional cadmium(II) coordination polymer: synthesis, crystal structure and physical properties

“…In recent years, the design and synthesis of coordination polymers (CPs) has been extensively investigated due to the significant potential of these compounds in various fields, such as small molecule separation, gas storage/separation, luminescence, sensing, catalysis and photocatalytic degradation (Fan et al, 2021;Kobielska et al, 2018;Lu & Astruc, 2020;Parmar et al, 2020;Schoedel et al, 2016). It has now been well documented that many factors, such as the organic ligands, temperature, pH values, reaction conditions, hydrogen bonding and aromatic stacking interactions, solvents and synthetic methods, have a great influence on the final structures and properties of CPs (Fan et al, 2020b;Lee et al, 2019;Naskar et al, 2018;Pushkarev et al, 2016). However, among the many factors mentioned above, organic bridging ligands as connectors play a crucial role in the formation of functional CPs (Marshall et al, 2015).…”

A Self‐Assembling Ligand Switch That Involves Hydroxide Addition to an sp2 Hybridised Phosphorus Atom – A System Allowing OH– Mediated Uptake of [MCl2] (M = Pd, Pt) Centres

“…Molecules that respond to external stimuli can allow fine control over both coordination chemistry and catalysis,, thus providing the potential to create sophisticated structures such as molecular muscles, switched rotors, pumps, compressors etc , . Redox, photochemical and p H toggles are regularly employed; of these, p H‐based switches can potentially be very attractive if the hydroxide ion is incorporated directly into the system, thus conferring significant electronic changes upon the conjugate product as it triggers the switch.…”