Time-Dependent Solvent-Driven Solid-State Fluorescence-based Numeric Coding.

Controllable solid-state transformations can provide a basis for novel functional materials. Herein, we report a series of solid-state systems that can be readily transformed between amorphous, co-crystalline, and mixed crystalline states via grinding or exposure to solvent vapors. The present solid materials were constructed using an all-hydrocarbon macrocycle, cyclo[8](1,3-(4,6-dimethyl)benzene) (D4d-CDMB-8) (host), and neutral aggregation-caused quenching dyes (guests), including 9,10-dibromoanthracene (1), 1,8-naphtholactam (2), diisobutyl perylene-3,9-dicarboxylate (3), 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), 4,7-di(2-thienyl)-benzo[2,1,3]thiadiazole (5), and 4-imino-3-(pyridin-2-yl)-4H-quinolizine-1-carbonitrile (6). Seven co-crystals and six amorphous materials were obtained via host-guest complexation. Most of these materials displayed turn-on fluorescence emission (up to 20-fold enhancement relative to the corresponding solid-state guests). The interconversion between amorphous, co-crystalline states, and crystalline mixtures could be induced by exposure to solvent vapors or by subjecting to grinding. The transformations could be monitored readily by means of single-crystal and powder X-ray diffraction analyses, as well as solid-state fluorescent emission spectroscopy. The externally induced structural interconversions resulted in time-dependent fluorescence changes. This allowed sets of privileged number array codes to be generated.

A Mild Silica Gel Promoted Synthesis and Initial Functional Study of Tetrapyridyl Tetrahydropyrrolopyrrolones.

A one-pot strategy with yields up to 82% was reported to generate 2-(pyridin-2-yl)-2-(3,3a,6-tris(5-pyridin-2-yl)-5-oxohexahydropyrrolo[3,2-b] pyrrol-2(1H)-ylidene)acetonitrile 1a and its derivatives 1b-d. Silica gel promoted quantitative conversion from stable intermediate to 1a within 30 min at room temperature. Finally, four chemical σ bonds and two chiral carbons with high diastereoselectivity were achieved. Compound 1a can act as a novel high selective UV-vis and fluorescence "turn-on" probe for Zn2+ and Cd2+, respond to proton, and show dual-state emission (DSE) characteristics.

One-Pot Synthesis of 3-Substituted 4H-Quinolizin-4-ones via Alkyne Substrate Control Strategy.

Three-substituted 4H-quinolizin-4-ones were obtained via a facile method with good selectivity and high efficiency. On the basis of alkyne substrate control, the mild and cost-efficient reaction has a broad substrate scope (20 examples, up to 93% yield) and is also easy to scale up. Active sites on the products allow for further modifications. The alkyne substrate control strategy could be further extended to achieve more complex three-substituted 4H-quinolizin-4-one skeletons.

A DNA small molecular probe with increasing K+ concentration promoted selectivity.

DNA small molecular probe study was considered as a promising approach to achieve DNA related disease diagnosis. Most related reports were performed under specific salinity. Herein, 4-imino-3-(pyridin-2-yl)-4H-quinolizine-1-carbonitrile (IPQC) was generated via a facile procedure with high yield (85%). It is found that IPQC could act as a universal probe for most tested ssDNA, dsDNA and G4 DNA in low [K+] concentration (less than 20 mM). However, IPQC showed highly selective G4 DNA binding via UV-vis and fluorescence response in increasing [K+] (e.g., 150 mM) conditions. The ion atmosphere effects are instructive for DNA probe exploration. This provides guidance for the design, selection and optimization of the probes for target DNA sensing.