Rational design of spiro[fluorene-9,9′-xanthene] based molecule for aggregation induced emission (AIE) and mechanochromism (MC): synthesis and theoretical investigation

Abstract

The development of novel organic fluorescent materials with strong luminescence in the aggregate state as well as stimuli response under external forces is of great importance for practical applications in the solid state. It is established that triphenylethylene and tetraphenylethylene are propeller-type aromatic molecular structures present in the majority of organic emitters with aggregation-induced emission (AIE) properties to prevent aggregation-caused quenching (ACQ). In this study, we have incorporated a spiro-xanthene (SFX) core for the first time to design a new donor–π–acceptor–π–donor 4,4′-((3′,6′-dibutoxyspiro[fluorene-9,9′-xanthene]-2,7-diyl)bis(thiophene-5,2-diyl))bis(N,N-diphenylaniline) (SP-TH) luminescent material with aggregation induced emission (AIE) and mechano-responsive properties. DFT calculations were carried out to study the electronic properties of SP-TH. The photophysical and electrochemical properties of SP-TH were systematically investigated. The photophysical (UV-Vis and PL spectroscopies) studies indicate that SP-TH has AIE features. In addition, the mechano-stimuli response of SP-TH was also investigated, and a hypsochromic shift (yellowish green to bluish green) was observed upon grinding the SP-TH sample and was analyzed using PXRD.