Reversible Solvatochromism of Polydiacetylenes Based on Extensively Hydrogen-Bonded Tubular Arrays

Abstract

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).

Nickel-Ion-Coordinated Reversibly Solvatochromic Polydiacetylene Based on Tubular Assembly of Macrocyclic Diacetylene

“…A presumptive understanding from earlier reports including those from our lab for solvatochromism is that the color changes are a consequence of the dissolution of unpolymerized residual DA monomers that creates structural cavities in the PDA supramolecular structure and thus results in partial distortion of the π-conjugated backbone . Surprisingly, MCDA-Ni monomers with good solubility in CHCl 3 and CH 2 Cl 2 did not show any colorimetric change at MCPDA-Ni .…”

“…The easy processability of the PDAs makes them suitable for designing devices in different shapes. − In general, PDAs display irreversible colorimetric behavior with blue-to-red color transition, and very few PDAs undergo a reversible color change in response to external stimuli. − Most of the PDAs with reversible chromatic behavior are caused by heat. In our very recent study, we demonstrated the first example of reversibly solvatochromic PDA derived from a tetracarboxylic acid-substituted macrocyclic diacetylene (MCDA) that has an extensively hydrogen-bonded network of tubular arrays …”

“…In our very recent study, we demonstrated the first example of reversibly solvatochromic PDA derived from a tetracarboxylic acid-substituted macrocyclic diacetylene (MCDA) that has an extensively hydrogen-bonded network of tubular arrays. 58 In continuing our efforts on developing PDA-based functional materials, herein, we designed and demonstrated a new reversibly solvatochromic PDA as a follow-up study. In the present study, a coordination-driven self-assembly approach was adopted for the construction of the supramolecular nanotubular architecture.…”

“…A presumptive understanding from earlier reports including those from our lab for solvatochromism is that the color changes are a consequence of the dissolution of unpolymerized residual DA monomers that creates structural cavities in the PDA supramolecular structure and thus results in partial distortion of the π-conjugated backbone. 58 Surprisingly, MCDA-Ni monomers with good solubility in CHCl 3 and To get more mechanistic insights into colorimetric response, we extended the solvatochromic sensing of dehydrated MCPDA-Ni by testing the dehydrated red phase against the same set of solvents. Interestingly, a red-to-yellow color change was observed only for ACE, CHCl 3 , and CH 2 Cl 2 ; on the other hand, the red phase remained intact for dehydrated MCPDA-Ni toward ACN, EtOH, IPA, and MeOH, which earlier had displayed in the blue-phase MCPDA-Ni state (Figure S12).…”

Stimuli-Responsive Polydiacetylene Based on the Self-Assembly of a Mercury-Bridged Macrocyclic Diacetylene Dimer

“…This design concept offers an advantage when applied to macrocyclic DA monomers, which first undergo supramolecular assembly and then UV-induced cross-linking to generate a structurally stable covalently connected tubular morphology. − Typical organic-based nanotubes are responsive to environmental conditions and can deform easily due to noncovalent molecular interaction-promoted assemblies. Results from our studies demonstrate that macrocyclic diacetylenes (MCDA) undergo self-assembly that is enforced by multiple interactions, including a π–π interaction from the acetylenic template, to form perfectly aligned stacks with a favorable polymerizable geometry, which transform into a covalently linked polymer structure via UV-induced polymerization. − …”