Issue 33, 2012

A mechanistic investigation of mechanochromic luminescent organoboron materials

Abstract

Mechanochromic luminescence (ML) refers to the luminescence color and/or intensity change of solid-state materials induced by mechanical perturbations. For organic molecular solids, this phenomenon is related to the specific packing modes and orientations of individual fluorophores, which could give rise to different excited-state interactions. The molecular solids of difluoroboron dibenzoylmethane (BF2dbm) derivatives were previously found to exhibit reversible ML at room temperature and are promising as self-healing optical materials. In this report, we aim to shed some light on the mechanism of BF2dbm ML by trying to understand the excited-state interactions among solid-state BF2dbm molecules and elucidate how these interactions change upon mechanical stimulation. We first investigated the optical properties of monomeric, dimeric, and polymeric BF2dbm derivatives in optically dilute solutions and demonstrated unambiguously that BF2dbm moieties have a propensity to form H-aggregates. Next, we studied the physical properties of these boron complexes in the solid state including their crystal structures, fluorescence emissions, and mechanochromic luminescence. By correlating solution data with the solid-state characterization results, it was concluded that two coupled processes, force-induced emissive H-aggregate formation and energy transfer to the emissive H-aggregates, are responsible for the observed BF2dbm ML in the solid state.

Graphical abstract: A mechanistic investigation of mechanochromic luminescent organoboron materials

Supplementary files

Article information

Article type
Paper
Submitted
04 May 2012
Accepted
03 Jul 2012
First published
04 Jul 2012

J. Mater. Chem., 2012,22, 17332-17339

A mechanistic investigation of mechanochromic luminescent organoboron materials

X. Sun, X. Zhang, X. Li, S. Liu and G. Zhang, J. Mater. Chem., 2012, 22, 17332 DOI: 10.1039/C2JM32809G

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