Fluorescent DNA probes with 1,6-hexanediyl as the linker between two pyrenes, phenylpyrenes or phenylethynyl pyrene fluorophores were synthesized (Py-1, Py-2 and Py-3) and their interactions with DNA were studied by UV–vis absorption spectra, fluorescence spectra and viscosity measurements. The probes show red-shifted emission compared with pyrene (up to 20nm). We found the interaction of these probes with DNA can be either intercalation or groove binding. Ratiometric fluorometry (ratio of the monomer and excimer emission intensity versus concentration of DNA) was achieved with these probes for DNA quantification (with limit of detection, LOD, up to 0.1g/mL). We also found that the undesired oxygen sensitivity of the emission intensity of pyrene fluorophore can be greatly suppressed by extending the π-conjugation framework of pyrene (the IAr/Iair value is decreased from 8.10 for pyrene to less than 2.20 for the DNA probes described herein).

Bisboronic acid 3 binds strongly and enantioselectively with six-carbon sugar alcohols but does not bind strongly with five-or four-carbon sugar alcohols or monosaccharides.

1,10-Fused ring phenothiazines were found to be a new kind of fluorescent dyes that strongly fluorescence in protic solvents than in aprotic solvents, with higher fluorescence quantum yields (Φ) and longer emission wavelength than the previously reported dyes that with similar solventsensitivity profile. For example, compound 5 shows a Φ-value of 0.075 in diethyl ether and 0.517 in methanol. Interestingly, a transition from C Cdouble bond (5) to C single bond (4) in the fused ring switch the photophysical properties completely, i.e. the analogue compound 4 demonstrates the opposite sensitivity, for which Φ= 0.099 in diethyl ether but the fluorescence is quenched completely in methanol. Further derivatization of 5 is convenient, demonstrated by the preparation of compound 6, for which the unique solvent sensitivity is reserved and higherΦin protic solvents was observed (Φ= 0.739 in methanol). The solvatochromism of the compounds were analysed with Lippert–Mataga correlation, ENT (30) values and multilinear regressions with Catalán and Kamlet–Taft solvents scales. The aprotic and protic solvents appeared as two isolated domains in the Lippert–Mataga plots, whereas fitting with ENT (30) scales gives a linear regression comprising both aprotic and protic solvents. Kamlet–Taft scales are more appropriate than the Catalán solvent scales for describing the solvatofluorochromism of the compounds. An intermolecular hydrogen bonding mechanism is proposed for the observed switching of the fluorescence with protic solvents.

Bisthiocarbonohydrazones are found to be a class of sensitive, selective, ratiometric, and colorimetric chemosensors for anions such as fluoride (F-) or acetate (Ac-). The sensitivities, or the binding constants of the sensors with anions, were found to be strongly dependent on the substituents appended on the π-conjugation framework, the delocalization bridge CH=N, the aromatic moiety, and the hetero atom in the C=X group (X=O, S) of the sensors. Single-crystal structures and 1H NMR titration analysis shows that the CH=N moiety is a hydrogen- bond donor, and it is proposed that an additional CH…F hydrogen bond is formed for the sensors in the presence F-1. A sensor bearing anthracenyl groups is demonstrated as a switch-on fluorescent chemosensor for F-1 and Ac-1. The recognition of F-1 in acetonitrile (MeCN) by a sensor with nitrophenyl substituents is tolerant to MeOH (MeCN/MeOH=10:1, v/v) and water (MeCN/H2O=30:1, v/v); at these solvent ratios the absorption intensity of the sensor-F-1 complex solution at maximal absorption wavelength was attenuated to half of the original value in pure MeCN.