Anion sensing and F(-)-induced reversible photoreaction of D-π-A type dye containing imidazole moiety as donor

A new donor-π-acceptor (D-π-A) type dye was synthesized by the condensation reaction between 2-cyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran and 4-imidazolecarboxaldehyde. The chemical structure of the dye was characterized by (1)H NMR, EA and MS. A novel chromogenic dye based on imidazole as donor unit and furan as acceptor unit displayed marked UV-visible absorption changes in the presence of fluoride ion. The levels of energy potential and the electron density distributions of this dye were also simulated and discussed using computational model calculation. The reversible photoreaction of the dye-F(-) complex was studied by time-dependent UV-visible absorption spectra.

Chromogenic sensing of biological thiols using squarylium dye

A new highly selective probe for biothiols, squarylium dye (SQ), was designed and synthesized. The probe displayed a color change from blue to colorless upon reaction with biothilos such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH). The competition experiments revealed that no obvious interference was observed by performing the titration with the mixtures of Cys and other amino acids. The results indicated that SQ was highly selective for Cys detection. Moreover, SQ could also serve as a "naked-eye" probe for Cys with a minimum detectable concentration of approximately 4 μM.

Spectral properties of highly selective chemosensor for Hg2+

A (E)-2-(2-(2-(1H-indol-3-yl)vinyl)-4H-chromen-4-ylidene)malononitrile (dye 1) was synthesized and its cation sensing properties in DMSO were investigated by UV-vis spectroscopy. Upon the addition of Hg2+, the solution of dye 1 showed color change and the absorption band shows a formation of a 1:1 dye 1-Hg2+ coordination complex. The dye 1 exhibited high selectivity for Hg2+ as compared with other cations. Interestingly, the dye 1-F- complex also could be recovered by adding Hg2+. We have investigated the ability of complex formation based on the association constant, Kass; the binding ability for the complex formation of dye 1-F- and Hg2+ is greater than that of the dye 1 with F-.

Fluorescence quenching of carbazole by 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines intermolecular charge-transfer complex

The interaction between carbazole and 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines, (mono-, di-, and triethylamine) charge-transfer complex in DMSO was studied using fluorescence spectroscopy. The positive deviation from linearity has been observed in the Stern-Volmer plots. The experimental results showed that the fluorescence of carbazole was quenched by 2-chloro-3,5-dinitrobenzotrifluoride-ethylamines charge-transfer complex through a combined quenching procedure. The Stern-Volmer quenching constants, K(SV), have been determined and found to be greater quenching efficiency of ethylamine. Carbazole/2-chloro-3,5-dinitrobenzotrifluoride loaded PMMA film was exposed to ethylamine vapor, where the resulting absorption and emission changing properties were clearly monitored.

Hemicyanine-based colorimetric chemosensors: different recognition mechanisms for CN- sensing

Simple hemicyanine dyes were synthesized by a classical condensation reaction. The structures of these dyes were characterized by (1)H NMR spectroscopy, elemental analysis, and FAB-Mass spectrometry. The sensing behavior of the hemicyanines towards a selection of anions was investigated by UV-vis absorption spectroscopy. These structurally simple dyes displayed a rapid response and high selectivity for cyanide ion over other common anions in the DMSO/H(2)O solution. Different sensing mechanism of the dyes to cyanide ion were confirmed by (1)H NMR studies, together with theoretical calculations based on DFT and PPP-MO methods. These dyes show no colorimetric response for other anions investigated.

Squarylium-based chromogenic anion sensors

A squarylium (SQ) dye was synthesized by the reaction between squaric acid and 2,3,3-trimethylindolenine and its anion sensing properties were investigated using absorption and emission spectroscopy. This chemosensor exhibited high selectivity for CN(-) as compared with F(-), CH(3)CO(2)(-), Br(-), H(2)PO(4)(-), Cl(-), and NO(3)(-) in acetonitrile, which was attributed to the formation of a 1:1 squarylium:CN(-) coordination complex, the formation of which was supported by the calculated geometry of the complex.

A colorimetric and fluorescent chemosensor for Ni2+ based on donor-pi-acceptor charge transfer dye containing 2-cyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran acceptor and 4-bis(pyridin-2-ylmethyl)aminobenzene donor

A new designed colorimetric and fluorescent dye chemosensor was synthesized, characterized and computationally calculated using MO theory calculation, which was based on donor-pi-acceptor electron charge transfer system. This particularly designed dye chemosensor displayed the selective Ni2+ ion chemo-sensing effects in optical properties with absorption and fluorescence emission. This dye chemosensor represented clear absorption spectra changes with Ni2+ ion and the dramatic fluorescence quenching effect with Ni2+ ion was determined. However it showed no significant optical spectra changes upon the addition of other metal ions such as Cd2+, Na2+, Mg2+, Pb2+, Fe2+, Fe3+, Ca2+, Cu2+, Hg2+, except Zn2+.

The synthesis and spectral properties of a stimuli-responsive D-π-A charge transfer dye based on indole donor and dicyanomethylene acceptor moiety

A dual mode chemosensor dye 3 for detection of fluoride ion, based on the D-π-A molecular framework by one-step condensation, presents high selectivity and sensitivity both in colorimetric and fluorometric analyses. Upon the addition of F(-) anion, the absorption band shows a remarkable red shift along with fluorescent intensity decreasing. The absorption and fluorescent intensities of the dye 3 can be reversibly selected by deprotonation/protonation of the amine moiety via control of intramolecular charge transfer (ICT), leading to a molecular switch with "on" and "off" states. (1)H NMR titration analysis and DMol(3) calculation were employed to reveal the intermolecular charge transfer system of dye 3-F(-) complex.

The synthesis and spectral properties of a stimuli-responsive D-π-A charge transfer dye

A new donor-π-acceptor (D-π-A) type isophorone dye was synthesized by the condensation reaction between 2-(3,5,5-trimethylcyclohex-2-enylidene)-malononitrile and indole-3-carboxaldehyde. The chemical structure of the dye was characterized by 1H NMR, EA and MS. A novel, chromogenic, fluorescent dye based on indol as donor unit and isophorone as acceptor unit displayed marked UV-visible absorption changes and highly selective fluorescence quenching in the presence of fluoride ion. The dye also exhibited sizeable colour changes when used as a pH-induced molecular switch and as a detector for volatile organic compounds. The absorption and fluorescent intensity of the dye can be reversibly selected by protonation/deprotonation of the amine moiety via control of intramolecular charge transfer (ICT), leading to a molecular switch with "on" and "off" states.

A highly selective and sensitive colorimetric chemosensor for Fe(2+) based on fluoran dye

A highly selective chemosensor based on fluoran dye for Fe(2+), 2'-anilino-3'-methyl-6'-dibuthylamino-N-((2'-(2''-ethylimino) methyl) naphthalen-2-ol) iso-indolin-1-one-fluoran (5), was designed and synthesized. The chemical structures of all the intermediates and the fluoran dye 5 are characterized by (1)H NMR, (13)C NMR, Ms and elemental analysis. Upon addition of Fe(2+), the fluoran dye 5 shows a new peak around 658nm in its absorption spectra, and the color of solution changed from colorless to greenish black. Whereas other ions including Mg(2+), Pb(2+), Ni(2+), Hg(2+), Cd(2+), Fe(3+), Cu(2+), Zn(2+) and Al(3+) and so on induced basically no spectral change, which constituted a Fe(2+) highly sensitive and selective colorimetric chemosensor by "naked eyes".

The photo- and electrophysical properties of curcumin in aqueous solution

An investigation of the photo- and electrophysical properties of curcumin (1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) revealed well-defined color changes upon the addition of Hg(2+) or OH(-). Curcumin exhibited high selectivity for Hg(2+) ions, as compared with Cu(2+), Fe(2+), Fe(3+), Zn(2+), Na(+) and Ni(2+) ions in DMSO/H(2)O (5:1, v/v) which was attributed to the formation of a 4:1 Hg(2+)-curcumin coordination complex. Spectral responses at lambda(max)=434nm revealed that curcumin can function as a NOR logic gate with OH(-) and Hg(2+) as input variables. The electrochromic properties of curcumin were studied using an ITO/curcumin-Bu(4)NClO(4)/ITO cell. The electrochromic cell colored red at 3V, but changed to yellow in open-circuit condition.

Synthesis and property of solvatochromic fluorophore based on D-pi-A molecular system: 2-[[3-cyano-4-(N-ethyl-N-(2-hydroxyethyl)amino)styryl]-5,5-dimethylfuran-2(5H)-ylidene]malononitrile dye

2-[[3-Cyano-4-(N-ethyl-N-(2-hydroxyethyl)amino)styryl]-5,5-dimethylfuran-2(5H)-ylidene]malononitrile styryl dye was prepared by the condensation of 4-[(2-hydroxy-ethyl)-methyl-amino]-benzaldehyde (donor moiety) with 2-cyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (acceptor moiety). The corresponding design, synthesis and solvatochromic characteristics of the intramolecular charge-transfer (ICT) dye chromophore were discussed and determined. Optical properties such as absorption and fluorescence emission spectra were monitored in several solvent media with different polarity. In this determination, the prepared dye chromophore showed positive solvatochromism effect and the resulting solvatochromic characteristics were studied with semiempirical calculations. The energy potentials of this dye chromophore such as HOMO and LUMO values were calculated by computational simulation approaches using Material Studio 4.3. Furthermore, the functions as a molecular switching sensor with pH stimulation of alkali-acid addition were determined in DMSO, which was operated by deprotonation/protonation effects based on intramolecular charge-transfer system.