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.

A new chiral fluorescent BINOL boronic acid 1 has been synthesized. The chiral recognition properties of 1 are drastically different from BINOL boronic acid c. Sensor 1 shows improved enantioselectivity as well as chemoselectivity toward sugar alcohols, such as D-sorbitol and D-mannitol.The enantioselectivity of sensor 1 toward D-sorbitol (KR/KS) is 1:35 (pH 9.0), and the chemoselectivity for D-sorbitol/D-mannitol is 20:1

The X-ray diffraction (XRD) studies of a coumarin based hydrazone (receptor 1) have revealed self assembled pseudo double helix architecture involving closed shell O-O interactions besides other supramolecular interactions. The receptor (1) an intramolecular charge transfer (ICT) probe detected acetate, benzoate and dihydrogenphosphate through naked-eye in DMSO. The 1:1 stoichiometry was confirmed for all the anions. The 1H NMR studies indicated classical and non-classical hydrogen bonding through- NH and Ar-H protons of the receptor, respectively, during recognition process of the acetate through receptor (1). The theoretical studies through density functional theory (DFT) using B3LYP exchange functional with the basis set 6-311G** supported the UV-vis and 1H NMR studies. The time dependent density functional theory (TDDFT) computations of UV-vis excitations for the receptor (1) and receptor-acetate complex agreed well with our experimental findings. The cyclic voltammetric studies also supported formation of receptor–acetate complex.