Multi-color solid-state emission of β-iminoenolate boron complexes tuned by methoxyl groups: aggregation-induced emission and mechanofluorochromism. Issue 49 (3rd May 2016)

• Record Type: Journal Article
• Authors: Zhang, Zhenqi; Wu, Zhu; Sun, Jingbo; Xue, Pengchong; Lu, Ran
• Is Part Of: RSC advances. Volume 6:Issue 49(2016)
• Page Start: 43755
• Page End: 43766
• Publication Date: 2016-05-03
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6ra03722d
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : New β-iminoenolate boron complexes bearing benzoxazole were synthesized, and they exhibited strong luminescence in solid states. Abstract : A series of new β-iminoenolate boron complexes modified by methoxyl groups in different positions of the benzene rings were synthesized. They all exhibited AIE behaviours, for example, the emission intensity ofB2B in THF/H2 O (v/v = 1/19) was ca. 91-fold higher than that in THF. Interestingly, the emitting color forB4B changed from green to yellow during the AIE process on account of the different aggregated states. In addition, it was found that the molecular stacking modes enormously affected the solid emission of β-iminoenolate boron complexes.B2B emitted blue light due to the weakest π–π interaction in the crystal.BB, B3B andB24B emitted blue-green light on account of their similar packing modes in crystals, in which moderate π–π interactions were involved. In the case of crystalB4B, π-aggregates were generated directed by strong π–π interactions, leading to yellow emission. On the other hand, B4B exhibited multi-color emission upon stimulation by mechanic forces. WhenB4B was ground into ground powder 1 in a mortar, π-aggregates were damaged and the emitting color changed from yellow to green. If a small amount of ground powder 1 was further ground on a parchment, it was turned into ground powder 2 emitting blue light derived from the isolated molecules. The fluorescence of ground powder 1 could recover to yellow upon exposure to DCM. This meant that the emitting color changes between yellow and green were reversible. Similarly, reversible mechanofluorochromic processes between ground powder 1 and 2 were observed. Although the crystal with yellow emission could be changed into ground powder 2, only green emitting ground powder 1 was gained after treating with DCM. This kind of mechanofluorochromic materials with multi-color emission might have potential applications in anti-fake labels and mechanic sensors.