Synthesis of Intrinsically Dual-Emissive Aliphatic Conducting Polymer and ESIPT-Associated Switching of Amide-Aggregate to Imidol-Aggregate for Sensing of Cr(III) and Fe(III)

Abstract

The design, synthesis, and optimization of excited-state intramolecular proton transfer (ESIPT)-associated dual-emissive aliphatic conductive polymer is one of the very challenging tasks, and has not been reported to date. Herein, aliphatic fluorescent conducting polymers (FCPs) are synthesized by polymerizing N-(monomethylol)­acrylamide (MMA), acrylic acid (AA), and in situ-generated 3-N-(monomethylolacrylamido)­propanoic acid (NMMAPA). Of different FCPs, the maximum population of heteroatomic nontraditional luminophores, i.e., secondary amide (−CONH), imidol (−CN­(OH)), tertiary amide (−CON), and carboxylic acid (−COOH), in FCP4 is supported by the spectroscopic analyses, thermal profiles, fluorescence enhancements, and computational calculations. Thus, further investigations are made on FCP4 to explore the photophysical properties, check the suitability in dual metal ion sensing, and study the proton conductivity. The ESIPT-associated dual light emissions at 436 nm (λem1) and 573/617 nm (λem2) originate from FCP4 (amide)/FCP4 (amide)-aggregate and FCP4 (imidol)/FCP4 (imidol)-aggregate, respectively, and are supported by concentration-dependent emissions, time-correlated single photon counting studies, solvent polarity effects, and computational measurements. Regarding this, the high fluorescence quantum yields of 0.68 and 0.18 at λem1 and λem2, respectively, confirmed the ESIPT-associated strong dual emissions of FCP4. The UV spectrum within 264–300 nm, FTIR peak at 2165 cm–1, binding energies of −CN(OH)/–CN­(OH) at 399.0/533.4 eV, and computational studies indicate the coexistence of FCP4 (amide)/FCP4 (amide)-aggregate and FCP4 (imidol)/FCP4 (imidol)-aggregate forms of FCP4. In FCP4, −CONH/–CN­(OH)/–CON/–COOH/–CH2OH-associated dipolar and hydrogen-bonding interactions, n−π* transitions, and N-branching-associated rigidity contribute to ESIPT-associated amide–imidol phototautomerism, aggregation-enhanced emissions, dual light emissions, metal ion sensing, and conductivity. The strong coordinations of Fe­(III) and Cr­(III) with FCP4 (amide) and FCP4 (imidol), respectively, are supported by spectroscopic, thermal, and computational studies. The strong quenching efficiencies of Fe­(III) and Cr­(III) are indicated by the very low limits of detection of 0.1142 and 0.0534 ppb, respectively. The I–V and ac impedance spectroscopy data of FCP4 having 0.28 cm thickness and 1.72 cm2 area indicate high proton conductivities of 3.53 × 10–5 and 3.22 × 10–5 S cm–1 at pH = 7.0 and 8.0, respectively.

Synthesis of Semisynthetic Dual-State Fluorescent Polymers and Roles of Starch/Pectin on AIET-Assisted Dual-Emission, Conductivity, and Metal-Ion Sensing

“…Additionally, the trapped interlayer water molecules within these polymeric networks together with the hydrogen-bonded dipolar functionalities paved the hydrophilic channels for proton movements facilitating proton jump in SAML3/PAML4 . The I – V measurements of AML4, SAML3, and PAML4 exhibited non-Ohmic variations ascribed to the generation of local fields involving different aggregates of AML4, SAML3, and PAML4 (Figure c, f, and i) . Apart from the proton conductivity, the strong aggregation in SAML3/PAML4 was anticipated to confer the significant electrical conductivity by the enhanced through space π → π* transitions .…”

Synthesis and Characterization of a Temperature-Sensitive Microcapsule Gelling Agent for High-Temperature Acid Release

“…Through the analysis of the aforementioned series of experiments, combined with the molecular structural characteristics of microcapsule polymers, the underlying principles governing the controlled release effect of microcapsule gelatinizer under high temperatures are elucidated: − (1) for enhancing the rigidity of the molecular main chain: increasing the rigidity of the molecular main chain, such as by increasing the number of carbon atoms polymerized on the main chain or introducing cyclic structures (e.g., benzene rings, polyatomic rings); (2) for introducing strongly polar functional groups in side chains: incorporating strongly polar functional groups in side chains to facilitate hydrogen bonding within and between molecules, thereby enhancing the ability to form a network structure and improving thermal resistance; (3) for increasing molecular complexity through cross-linking: utilizing cross-linking and similar mechanisms to increase the complexity of the molecular chain, thereby reducing molecular thermal motion and enhancing thermal resistance. In the synthesis of GLE-1, the introduction of cross-linking agents results in a more complex molecular structure.…”

Exploring Diverse Amino Acid-Polyol Interactions Prevailing in Aqueous Systems at Different Temperatures by Physicochemical Contrivance Simultaneously Optimized by DFT

“…To recognize the charge-transfer events between the AA and D-mannitol, maps of molecular electrostatic potential (MESP) have been created at the same theoretical level. 52 Additionally, the adsorption energies or binding energies (ΔE ads ) for those studied systems have been evaluated by the following expression 53 = E E E E ads system AA Mannitol…”

“…The Multiwfn 2.6 suite has analyzed index plots of the reduced density gradient (RDG or s) vs molecular density at the ground state geometries. To recognize the charge-transfer events between the AA and D -mannitol, maps of molecular electrostatic potential (MESP) have been created at the same theoretical level . Additionally, the adsorption energies or binding energies (Δ E ads ) for those studied systems have been evaluated by the following expression normalΔ E ads = E system − E AA − E Mannitol where E system , E AA , and E Mannitol are the total energy of the structure-optimized system, free AA, and the D -mannitol molecule, respectively.…”