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Cis-trans isomer and polymorphism of 9-(4-(4-nitrostyryl)phenyl)-9H-carbzole (Dye 1 ) were obtained unexpectedly. Each isomer has two polymorphs, which was characterized by X-ray single crystal diffraction. Polymorphs T1 and T2 are trans -configuration and both crystallize in monoclinic space group P 21/c. Polymorphs C1 and C2 are cis -configuration and crystallize in triclinic space group P -1 and monoclinic space group P 21/c, respectively. Trans -isomer shows better stability and higher density than that of cis -isomer, but cis -isomer displays better solubility than that of trans -isomer. The molecular structures and packing arrangements of the four kinds of crystals show different features. The twisted conformation of cis -isomer effectively avoids π-π interactions and close packing. Both the trans and cis isomers show remarkable aggregation-induced emission effect in the acetonitrile/water mixture. In addition, fluorescence cell imaging experiment proves the potential application of the two isomers of dye 1 . [ABSTRACT FROM AUTHOR]

Two Schiff base derivatives based on diaminomaleonitrile were synthesized and characterized. Both of the two compounds displayed a highly selective UV and off-on type fluorescent response to Cu 2+ in acetonitrile solution. The mixtures of Cu 2+ with 1 or 2 showed great potential application in bioimaging. Two different polymorphs of compound 1 were obtained from ethanol and ethyl acetate, respectively, which exhibit obvious differences in the wavelength and intensity of the fluorescence emission. This interesting phenomenon may originate from the tightness of packing and π–π interactions in the stacking structure. Compound 2 was aggregation-enhanced emission (AEE)-active in tetrahydrofuran (THF)/water mixtures. Moreover, compound 2 in a solid amorphous state was collected though special methods, which showed completely different fluorescence compared with that of the crystal due to the irregular molecular aggregation pattern. [ABSTRACT FROM AUTHOR]

Abstract: Two novel soluble chemosensors based on Schiff-base diaminomaleonitrile derivatives which were modified by an aza-crown ether moiety have been synthesized. These chemosensors were fully characterized by 1H NMR, 13C NMR spectroscopy, mass spectrometry, IR, DSC and single crystal X-ray diffraction. The recognition abilities of the sensors with a range of metal ions were evaluated and their photophysical properties have been systematically investigated. DFT theoretical calculations were employed to understand the behavior of the sensors toward the Cu(II). The sensing mechanism was derived through experimental and theoretical calculations. The results consistently indicated that the monoaza-10-crown-5 species was the ideal sensor, which can be utilized to monitor Cu(II) in solution over a wide pH range. [Copyright &y& Elsevier]