Enhanced Host‐Guest Association and Fluorescence in Copolymers from Copper Salphen Complexes by Supramolecular Internalization of Anions

• Published in: ChemPlusChem (Weinheim, Germany) Vol. 88; no. 3; pp. e202200310 - n/a
• Main Authors: Hernández‐Pacheco, Paulina, Zelada‐Guillén, Gustavo A., Romero‐Ávila, Margarita, Cañas‐Alonso, Roberto Carlos, Flores‐Álamo, Marcos, Escárcega‐Bobadilla, Martha V.
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 01.03.2023
• Subjects: anion binding; Chemistry; Chemistry, Multidisciplinary; coordination chemistry; fluorescence; Physical Sciences; polymers; Science & Technology; supramolecular chemistry; OPTICAL CHEMOSENSORS; BUILDING-BLOCKS; IONS; fluorescence; AGGREGATION-INDUCED EMISSION; QUADRUPLEX DNA; coordination chemistry; MOLECULAR RECOGNITION; SALEN; CHEMISTRY; anion binding; RADICAL POLYMERIZATION; polymers; RECEPTORS; supramolecular chemistry
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.202200310

We describe the synthesis, crystallographic characterization of a new Cu−Salphen compound and its use as a host Lewis‐acid against guest anions in two versions: a) free molecule, b) copolymerized with methyl methacrylate:n‐butyl acrylate (1 : 4‐wt.) as protective co‐monomers. Higher contents in Cu−Salphen yielded larger and more homogeneous polymer sizes. Polymer size together with glass transitions, heat capacity, thermal degradation, guest‐saturation degrees and host‐guest species distribution profiles from spectrophotometric titrations explained growths of up to 630‐fold in K11 and 180000‐fold in K12 for the host's binding site attributable to a solvophobic protection from the macromolecular structure. Spectrofluorimetry revealed blue‐shifted×13–16 larger luminescence for Cu−Salphen in the polymers (λem=488–498 nm) than that of the non‐polymerized counterpart (λem=510–543 nm) and “turn‐on” blue‐shifted enhanced fluorescence upon guest association. We propose a cooperative incorporation of the guests occurring from the outer medium toward internally protected binding site pockets in the random coil polymer conformations. One‐color cached light beacons. Fluorescence performance of a new Cu−Salphen coordination compound showed blue‐shifted turn‐on one‐order of magnitude higher luminescence when protected by copolymerization to acrylic monomers in chains of different sizes. Higher light emission levels and up to five‐orders of magnitude larger association constants were possible upon host‐guest binding for the polymerized metal complex, after internalization of anion guests into the protective polymer random coils.