Precise Molecular Design of a Pair of New Regioisomerized Fluorophores With Opposite Fluorescent Properties

Abstract

Aggregation-induced emission (AIE) has attracted much attention in the past 2 decades. To develop novel AIE-active materials, ACQ-to-AIE transformation via regioisomerization is one of the most straightforward method. However, most of the reported ACQ-to-AIE transformations are achieved by migrating bulky units. In this work, a facile conversion was realized by migrating a small pyrrolidinyl group from para- to ortho-position on the rofecoxib scaffold. As a result, a pair of new isomers named MOX2 and MOX4 exhibited AIE behavior and ACQ activity, respectively. Moreover, MOX2 also showed solvatochromic, mechanochromic, and acidochromic properties with reversible multi-stimulus behavior. Single crystal X-ray analysis of MOX2 revealed that the molecular conformation and its packing mode were responsible for the AIE emission behavior. Further investigation indicated that MOX2 showed high lipid droplets staining selectivity. Taken together, the current work not only provides a new design philosophy for achieving ACQ-to-AIE conversion by migrating a small pyrrolidinyl group but also presents a promising candidate MOX2 for potential applications such as in security ink, optical recording and biological applications.

Large Steric Substituent-Entangled Luminescence Enhancement under High Pressure

“…For the crystal structure of Y7 measured under ambient conditions, one −CN···H distance is 2.644 Å and all the others are longer than 2.955 Å. However, the shortest O···H contact in MOX2 is 2.493 Å, and there are three additional contacts shorter than 2.644 Å . At the same time, the two oxygen atoms of the −SO 2 CH 3 group in MOX2 are more electronegative than the nitrogen atom of the −CN group in Y7.…”

“…MOX2 and Y7 were synthesized as described in our previously published literature and verified by 1 H NMR and 13 C NMR (Figures S1–S4). , All the DACs were built with a pair of 300 or 500 μm type-IIa diamond anvils. T-301 stainless-steel gaskets were prepressed to a thickness of 30–45 μm, and a hole of 180 or 310 μm was laser drilled in the center of the indentation as a sample chamber, with a ruby ball inside for pressure calibration …”

“…Second, MOX2 itself is prone to form hydrogen bonds under high pressure, and the −CN group also can form hydrogen bonds. Third, both of them exhibit aggregation-induced emission (AIE) and mechanochromic luminescent (MCL) effects. , The luminescence properties of MOX2 under high pressure were studied by using in situ fluorescence spectra. In situ infrared (IR) spectra, in situ UV–visible (UV–vis) absorption spectra, and geometric optimization by density functional theory (DFT) were also used to further rationalize the fluorescence shift and enhancement phenomena.…”

One-step facile transformation from rofecoxib to reversible mechanofluorochromic materials with dual-state emission

“…19,25 This balance approach has emerged as an exciting alternative for the exploration and optimization of DSEgens. [26][27][28] Combining with our previous work, the conversion from ACQ to AIE was achieved by migrating the same group from the para-to ortho-position on the rofecoxib scaffold, [29][30][31] and it is possible to explore a balance state between ACQ and AIE, and then find a new simple DSEgen system by minor modification of the rofecoxib scaffold. Although this a Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian hypothesis is an intriguing question without straightforward guidance, it is meaningful to explore.…”

Unraveling the Mechanism of ACQ-to-AIE Transformation of Fluorescein Derivatives

“…The explanation of the AIE phenomenon as mentioned above is the restriction of the intramolecular motion mechanism. − From the perspective of the potential energy surface of the photophysical process, the AIE working mechanism can be described as the restriction of access to a dark state and restriction of access to a conical intersection. , Since ACQ is the opposite phenomenon of AIE, it is typically difficult to convert an ACQ molecule to an AIEgen. Only a few studies have been reported on ACQ-to-AIE transformation − and the design strategies involving the introduction of AIE backbones into the ACQ molecule ,, and tuning the molecular packing mode to suppress π–π interaction by regioisomerization or other methods, − which may require a large change in the molecular structure …”