Ye-Xin Li

A differentially selective probe based on diketopyrrolopyrrole with fluorescence turn-on response to Fe3+, and dual-mode turn-on and ratiometric response to Au3+, and its application in living cell imaging

A diketopyrrolopyrrole-based probe DPP-PyR was able to recognize Fe(3+) and Au(3+) with fluorescent turn-on response via different emission modes with relatively low detection limit. Moreover, DPP-PyR exhibited preferential second mode of selectivity for Au(3+) as it ratiometrically displaced Fe(3+) from the [DPP-PyR+Fe(3+)] complex. Furthermore, the imaging experiments indicated that this probe was cell-permeable and could be used to detect Fe(3+) and Au(3+) ions within living cell. To the best of our knowledge, it was the first probe for detection Fe(3+) and Au (3+) at the same time ever reported.

Effects of substitution position on crystal packing, polymorphism and crystallization-induced emission of (9-anthryl)vinylstyrylbenzene isomers

Three (9-anthryl)vinylstyrylbenzene (ASB) position isomers were synthesized and compared. Substitution position affects temperature-induced polymorphism, crystal packing and crystallization-induced emission (CIE) properties. Different from 1,2-ASB and 1,4-ASB, 1,3-ASB undergoes a crystal-to-crystal phase transition upon heating. The crystal structure of a new phase (1,3-ASB-β) was successfully solved. Thus, the solid emission of 1,3-ASB could be tuned by polymorphism. In contrast, the solid emission of 1,4-ASB is controlled by its crystallinity. In the crystal structures of 1,2-ASB and 1,3-ASB-β, the adjacent interacting anthryls are inclined to adopt an edge-to-face configuration with C–H⋯π interactions. In contrast, the adjacent anthracene rings in the 1,4-ASB crystals are parallel to each other with π⋯π interactions. Furthermore, multiple intermolecular interaction modes such as C–H⋯π and H⋯H interactions coexist in the crystal structure of 1,4-ASB, which collectively results in a closer packing. Interestingly, 1,4-ASB displays CIE behaviour. In contrast, the emission of the other two isomers is quenched in the solid state. The effect of substitution position on the photophysical properties is systematically studied.

Conformation twisting induced orientational disorder, polymorphism and solid-state emission properties of 1-(9-anthryl)-2-(1-naphthyl)ethylene

Polymorphism is important to study the structure–property relationship with a minimum number of variables. Compound 1-(9-anthryl)-2-(1-naphthyl)ethylene (ANE) can form three polymorphs by controlling the crystallization conditions, which belong to the P212121 space group for ANE-a, P21/c space group for ANE-b and P space group for ANE-c, respectively. Orientational disorder was found in ANE-b and ANE-c polymorphs. The emission maximum of the three polymorphs are 496, 470 and 490 nm, respectively. Each is blue-shifted from that of a concentrated solution. The formation of orientational disorder and the blue-shift behavior in emission are closely related to the degree of conformational twisting. A large dihedral angle between the anthracene and naphthalene rings is helpful to induce orientational disorder and blue-shift in the solid emission maximum. The emission efficiency of ANE solution and polymorphs is 42% (CH2Cl2 solution), 28% (ANE-a), 22% (ANE-b) and 47% (ANE-c), respectively. The ANE-c polymorph emits even more efficiently than the solution. This is attributed to the different packing environments, which produce distinct PL decay dynamics. For the three polymorphs, the decay behaviors are all double-exponential and the fluorescence efficiency is enhanced as the proportion of the short-lived component increases. This study shows that compound ANE is a kind of tunable solid-state fluorescent material and the molecular conformation plays an important role in the orientational disorder, aggregate packing and solid-state emission.

Highly selective ratiometric fluorescent probe based on diketopyrrolopyrrole for Au3+: an experimental and theoretical study

A diketopyrrolopyrrole-based fluorescent probe 1 was explored as a ratiometric probe for selective detection of Au3+, with the detection limit of 18 nM. The probe displayed an absorption maximum at 528 nm and a strong red fluorescence at 610 nm. In the presence of Au3+, the absorption and emission band blueshifted to 488 and 555 nm, respectively. Correspondingly, the color of the probe solution changed from orange to flesh color, and the fluorescence changed from orange to yellow-green. NMR and HRMS spectral analysis demonstrated that the selective ratiometric fluorescence response of probe 1 with Au3+ involved a selective Au3+-mediated hydrolyzation and oxidization reactions using a catalytic amount of Au3+. In addition, the ratiometric response of probe 1 was rationalized by DFT and TDDFT calculations.

A diketopyrrolopyrrole-based fluorescence turn-on probe for the detection of Pb2+ in aqueous solution and living cells

A diketopyrrolopyrrole-based fluorescent probe DPP-HBT bearing a benzothiazole hydrazone motif exhibited an obvious fluorescent turn-on response toward Pb2+ ions with a low detection limit of 2.3 × 10−10 M in aqueous solution. Furthermore, the imaging experiments indicated that this probe was cell-permeable and could be used to detect Pb2+ ions within living cells.

A single-state fluorescent with bright white-light emission in the solid station and aggregation-induced emission enhancement compound for Pd0 detection

A single-state molecule compound with phenanthrene-imidazole as fluorescent core was synthesized. The compound emitted white light in solid state and exhibited aggregation induced emission enhancement (AIEE) characteristic in solution state. From photophysical properties, it was presumably that π-π stacking caused by the excimer, which generated between solid molecules, led to the emitting white light. In addition, in the solution state, with the increasing fraction of the poor solvent, the rotation of the compound molecule was inhibited, which led to the luminescence enhancement induced by aggregation. In the aspect of Pd0 response, compound 6 had a sensitive detection of Pd0. The bathochromic shift of emission peak from around 390nm to around 425nm and remained saturated within 30min. Compound 6 was stable at pH of 6-9 and the detection limit for metallic palladium was as low as 2.7nM.

TBET-based ratiometric fluorescent probe for Hg2+ with large pseudo-Stokes shift and emission shift in aqueous media and intracellular colorimetric imaging in live Hela cells

The detection of Hg2+ in biological systems and its imaging is of highly importance. In this work, a novel ratiometric fluorescence probe is developed based on through-bond energy transfer (TBET) with a 2-(2-hydroxyphenyl)benzoxazole (HBO) as donor and a Rhodamine derivative-Hg conjugate (RDM-Hg) as acceptor. Hg2+ weakens the fluorescence of HBO at 430 nm and meanwhile interacts with Rhodamine B derivative to form a fluorescent conjugate (RDM-Hg) giving rise to emission at 597 nm with a 167 nm red-shift. Further, the difference 282 nm between the donor absorption (315 nm) and the accepter emission (597 nm) for 1+Hg2+ is comparable to the highest value of the Stokes shift (282 nm) reported earlier for other reported TBET-based cassette. Through-bond energy transfer from HBO to RDM-Hg is triggered by Hg2+ resulting in concentration-dependent variation of fluorescence ratio I597/I430. A linear calibration of I597/I430versus Hg2+ concentration is obtained within 0-5 μM, along with the lowest detection limit being found to be as low as 1.31 × 10-9 mol·L-1 (~ 0.26 ppb) for Hg2+. This feature is further demonstrated by colorimetric imaging of test strip and intracellular Hg2+. On the other hand, the HBO/RDM TBET sensing system is characterized by a combination of high sensitivity and selectivity. The present study provides an approach for further development of ratiometric probes dedicated to selective in vitro or in vivo sensing some species of biologically interest.