The cation-directed self-assembly process has emerged as a fascinating approach for constructing supramolecular architectures and manifested a diverse range of assembly related applications. Herein, we synthesized a macrocyclic structure containing bis-amidopyridine and photopolymerizable diacetylene template, PyMCDA. Owing to the metal coordination affinity of bis-amidopyridine and the π−π stacking characteristic of diacetylene template and complementary to the cyclic molecular framework, Cs + -directed organic nanotubes are generated via unidirectional selfassembly of PyMCDA. The monomeric PyMCDA nanotubes are transformed into the covalently cross-linked chromogenic polydiacetylene nanotubes (PyMCPDA-Cs + ) by UV-promoted topochemical polymerization. The result of a metal−ligand coordination characteristic, geometric parameters in solid-state assemblies, and topochemical polymerization behavior reveals a generation of Cs + ion inserted nanotubes. Interestingly, PyMCDA-Cs + nanotubes display thermochromic property with a brilliant blue-to-red color transition.
Since the pioneering discovery by
Wagner, polydiacetylenes (PDAs)
and their solvatochromic properties (typically blue-to-red or purple
transitions) have been the subject of extensive research efforts.
Without exception, PDAs have been found to undergo irreversible solvent-induced
color changes, and no cases exist in which initial blue states of
the PDAs are regenerated after solvent removal. Herein, we describe
the first example of a reversibly solvatochromic PDA that is derived
from a macrocyclic diacetylene (MCDA) containing four carboxylic acid
moieties. Infrared spectroscopic studies confirmed the synergetic
interplay of intra- and intermolecular hydrogen-bonding interactions
to control the reversibility. The weak intramolecular hydrogen bonds
allowed a solvent-induced distortion of the PDA backbone (purple state)
by releasing unpolymerized monomers, while the strong and networked
intermolecular hydrogen-bonding interactions ensured the rigidity
of the tubular channels and served as the driving forces for the recovery
of the initial conformation (blue state).
Polydiacetylenes (PDAs) present excellent chromogenic characteristics and have been extensively utilized as a sensory polymeric material to design and fabricate colorimetric sensor systems. Herein, we describe a Ni 2+ -ion-directed reversibly solvatochromic tubular PDA based on macrocyclic diacetylene (MCDA). A dimeric MCDA complex was formed through Ni 2+intercalated coordinative binding with carboxyl groups, which later transform into blue-phase PDA upon UV irradiation. Infrared spectral analysis confirmed the presence of structural water molecules coordinating to central Ni 2+ , which predicted to fulfill the octahedral geometry. Spectroscopic studies for the reversible blue−red chromatic behavior revealed a very unusual and unprecedented chromatic switching mechanism originating due to localized structural disruption at the Ni 2+ coordination site that leads to torsion in the π-conjugated backbone for chromatic changes, in contrast to the typical residual monomeric dissolutioninduced mechanism. This unusual behavior can be attributed to the coordinating water molecules, which presents an attractive advantage by creating a hydrophilic pocket at the coordination site and allows interactions with hydrophilic solvents causing structural distortion.
A new flexible layered material was generated from macrocycles containing functional, flexible, and intercalating units. The layered macrocycles exhibit thermoresponsive color changes in a wide temperature range.
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