Side‐Chain Engineering of Boron β‐Dialdiminate Homopolymer for Solvent‐Dependent Emission Properties

• Published in: Macromolecular rapid communications. Vol. 46; no. 4; pp. e2400775 - n/a
• Main Authors: Ito, Shunichiro, Sakai, Yuki, Tanaka, Kazuo
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.02.2025
• Subjects: Aggregates; Boron; Boron - chemistry; borzon complex; Chains (polymeric); Chloroform; Chromatography; Dimethylformamide; Emission analysis; Environmental effects; homopolymer; Luminescence; Molecular chains; Molecular Structure; NMR; Nuclear magnetic resonance; Polymers; Polymers - chemical synthesis; Polymers - chemistry; solvatochromism; Solvents; Solvents - chemistry; Stimuli; Triethylene glycol; borzon complex; homopolymer; luminescence; solvatochromism
• ISSN: 1022-1336; 1521-3927; 1521-3927
• DOI: 10.1002/marc.202400775

Luminescent materials that respond to changes in microscopic chemical conditions are essential for visualizing and evaluating molecular environments. Boron complexes are often employed as robust scaffolds for constructing such responsive systems because of their inherent stimuli‐responsive properties. However, in the case of nonresponsive luminophores, the absence of these intrinsic features limits their range of applications. In this study, environment‐responsive luminescent homopolymers based on the boron β‐dialdiminate complex are developed, which is intrinsically less responsive, by introducing optimized side chains. As a key finding, the triethylene glycol‐decorated polymer exhibits more intense luminescence in chloroform but weaker luminescence in N,N‐dimethylformamide. Structural analyses using NMR and size‐exclusion chromatography suggest that this polymer forms larger aggregates in polar solvents because of the solvophobicity of its main chain, while the polar side chains assist in maintaining adequate dispersibility of these aggregates. Photophysical measurements indicate that interchromophore interactions within the aggregates should be responsible for the reduced luminescence in polar solvents. These findings suggest that side‐chain engineering should be an effective strategy for creating stimuli‐responsive polymers from otherwise nonresponsive luminophores. Boron β‐dialdiminate homopolymers exhibit solvent‐dependent emission, driven by the solubility contrast between their main and side chains, even though the monomers themselves show little sensitivity to solvents. The triethylene glycol‐decorated polymer displays stronger emission in chloroform and weaker emission in DMF. In DMF, interchromophore interactions within the uniformly dispersed aggregates likely lead to nonradiative quenching of the excited energy.