Fluorescent Chemosensors And Logic Gates Based On Dicyanomethylene-4H-pyran And Cyanine Derivatives

The development of highly sensitive and selective chemosensors has become an active area in supramolecular chemistry, especially in the biology and microenviroment. The remarkable progress in the development of molecular logic gates has brought chemists closer to the realization of molecular-scale calculator since the first report of molecular AND logic gate based on chemosensors by de Silva et al. Compared with the modern semiconductor IT industry, molecular logic gates can be viewed as computational devices that process physical or chemical "inputs" to generate "outputs" based on a set of logical operators. The molecular logic systems can also make themselves to convenient reconfiguring, especially for application in the life sciences. The "bottom-up" method exhibits a distinct advantage over conventional semiconductor counterparts. As a consequence, molecular logic function can be designed in chemical and intracellular sensing, small object recognition and intelligent diagnostics.Molecular fluorescence has many remarkable advantages, such as high sensitivity down to the single molecule, easy detection and wide dynamic ranges. With further understanding molecular recognition and increasing skills in molecular design, several Donor-Ï€-Acceptor (D-Ï€-A) chemosensors based on dicyanomethylene-4H-pyran and cyanine derivatives were synthesized for the detection of cations and anions, and successfully constructed as memory keypad and half-substractor with comparator function. The main contents and results are outlined as follows:In Chapter 1, the major sensing principles of optical chemosensors are introduced, and the progress of molecular switches and logic gates performing distinct signalling output is reviewed.In Chapter 2, a novel fluorescent probe DCPP possessing both DCMP and 2,6-bis(amiomethyl)pyridine moieties was designed for detecting Hg2+and Cu2+. The characteristic fluorescence of Hg+-selective OFF-ON and Cu+-selective ON-OFF can be monitored, and controlled reversibly by the sequence and ratio of Hg2+and Cu2+inputs, which has been successfully constructed as a keyboard capable of crossword puzzles and logic memory at the molecular level based on the above logic operation. It provides a characteristic signaling pattern which can perform distinct algebraic operations solely in the fluorescence mode with the same excitation wavelength and be detectable in fluorescence for straightforward "reading" of the arithmetic results. The concept of such crossword puzzle based on fluorophores can be expected to greatly develop the combinatorial logic operations in sequential logic circuits with memory function.In Chapter 3, a V-shaped molecule of DADPP was designed, containing two receptors such as an aromatic unit possessing bis(2-pyridyl-methyl)amine (DPA) moiety and a phenolic moiety, via double bonds as bridges to incorporate a dicyanomethylene-4H-pyran unit as chromophore. A half-subtractor with a combination of comparator has been constructed based on intramolecular charge transfer (ICT) process resulting from hosting two different guests with the binding of Zn2+and the deprotonation of phenolic hydroxyl group in a unimolecular system. The corresponding spectral shifts in absorption and a variation in fluorescence intensity were well elucidated. An XOR (exclusive OR) logic gate generates the difference digit of half-subtractor reading at 445 run, and two INHIBIT logic gates are achieved for the borrow digit of half-subtractor when the output signals are monitored at 400 and 525 nm, respectively. Taken together, the comparison and subtraction operations are practically performed in parallel without mutual interference due to the same inputs and different outputs within the same molecule system.In Chapter 4, a novel thermometer fluorescent sensor poly(NIPMAM-co-DCPDP) consisting of N-isopropyl methacrylamide as a thermoresponsive unit and dicyanomethylene-4H-pyran derivative as a dipolar-sensitive fluorophore unit was designed. Poly(NIPMAM-co-DCPDP) performs fluorescence quenching merely by coordination with Cu2+ions or increasing temperature in neutral or acid aqueous solution.The ON-OFF fluorescence response of poly(NIPMAM-co-DCPDP) is driven by a temperature-induced phase transition from coil to globule and the capture of Cu2+ions resulting in a decrease of the ICT efficiency in neutral solution. The combinational serial NOR logic operation as well as two INHIBIT logic gates was constructed with three inputs:various pH, temperature change, and Cu2+ions. The proposed combinational logic circuits play a key role in mimicking comprehensive arithmetic operations at the nano-scale level.In Chapter 5, a new strategy of incorporating ion-sensitive fluorescent unit to form hydrophilic copolymer poly(HEMA-co-MCPDP) has been developed as film sensor for Cu2+ and PPi.2-hydroxyethyl methacrylate (HEMA) as a neutral hydrophilic chain segment is chosen as monomer for its high hydrophilicity to improve ion permeability into the polymer matrix. Using the ensemble method, the related metal complex, poly(HEMA-co-MCPDP)-Cu2+, shows turn-on fluorescence and high sensitivity for PPi both in solution and thin film over other anions such as adenosine triphosphate (ATP) and phosphate (Pi). The low-cost hydyophilic copolymer film of poly(HEMA-co-MCPDP)-Cu2+ exhibits high sensitivity and rapid response to PPi with turn-on orange-red fluorescence, showing an ideal hydrophilic film strategy for low-cost anion chemosensors or chips to the on-line monitor and high-throughput bio-processing in continuous system.In Chapter 6, three tricarbocyanine derivative dyes (IR-897, IR-877, and IR-925) with different isothiocyanate substituents as dosimeter units via the specific Hg2+-induced desulfurization have been synthesized for developing near-infrared (NIR) colorimetric and ratiometric chemodosimeters to mercury ion. The distinct response is dependent upon the electron-donating effect of isothiocyanate substituents, that is, the stronger in the electron-donating capability of isothiocyanate substituents, the faster in the Hg2+-promoted cyclization. IR-877 and IR-897 with Hg2+exhibit large red shifts in absorption (176 and 162 nm, respectively), fully meeting "naked-eye" colorimetric changes and successfully developed as Hg2+and MeHg+indicator paper. Moreover, measuring either a single emission with two excitation sources (excitation spectra mode) or dual emission with an isosbestic absorption point as single excitation source, these chemodosimeters can be successfully constructed as the first NIR ratiometric Hg2+sensors, allowing for fast and accurate measurements with eliminating the influence of dye concentration and microenvironmental fluctuations in pH, refractive index and photobleaching.In chapter 7, a series of novel Aggregation-induced Emission (AIE) luminescent materias (DECM, DDCM, DECP and DDCP) were designed and synthesized. The structure is a typical D-Ï€-A structure containing quinoline unit as electron-receptors, N,N-dimethylaniline and triphenylamine unit as electron-donor. Their AIE effects were fully studied with absorption and fluorescence spectra. Moreover, the potential application was done for detection of anionic surfactants.In addition, some other synthetic work was introduced. A new series of DCM derivatives based on dicyanomethylene-4H-chromene with different receptors was designed.