Molecular Logic Circuits Based On The Structure Conversions Of Fluorescein Derivatives

In this thesis, we designed and synthetized two logical molecular BHF+ and QHF+, based on the bifunctional molecular(fluorescein and hemicyanine). Their structures were confirmed by 1H NMR, 13 C NMR, ESI-HRMS and elemental analysis. We utilize the phenolic hydroxy and spirolactone group, which are sensitive to the p H. On the other hand, the water addition reaction to the C=N+ come up the strong basic condition. We study the compounds photophysical properties in depth, the research result list as follows:First, we investigated the optical properties of the compounds BHF+ and QHF+ via UV-absorption spectra in details. In strong acidic media, the protonation of the fluorescein fluorophore occurred immediately, which led the characterized absorption the protonated of fluorescein moiety(~430 nm). With the weaken the acidity, the deprotonation was occured on the stucture of quinoid, the compounds form are located in the mono-cation BHF+ and QHF+, and the moiety of fluorescein be in the equilibrium of the open/close ring. The absorption peak show the moiety of fluorescein open state(~480 nm)and the moiety of hemicyanine(~530 nm).With the enhancement of the basicity, the spiro lactone group was broken and recover the xanthene system. The strong absorption arise the moiety of fluorescein open state(~480 nm)and the moiety of hemicyanine(~530 nm), the predominate form of the compound of the neutral and mono-anion. At high basic conditions, a characteristic di-anion form is attained by water addition reaction breaks the dye’s conjugate of the moiety of hemicyanine, and only reflect the moiety of fluorescein open state(~490 nm). By the investigate of the absorption under various of the p H values, the compounds BHF+ and QHF+ take shape the five ionization states: di-cation, cation, zwitterion, anion and di-anion after water adduct.We make use of the five ionization states inversion and their absorption signal of BHF+ and QHF+, we take advantage of the same concentration acid and base solution as the inputs of the logical operations, the relevant wavelength absorption or transmittance as the outputs of the logical operations.We design three logic circuits of two input/two output—half-adder; half-subtractor; digital comparator. At the same condition, the half-subtractor and digital comparator is carried out the logical operation, so the two logical circuits put to use cooperatively in order to enhance the accuracy of logic circuits. Also, we investigate the reproducibility and reset to the initial state of the logic operation, which account for the practical potentiality and value.Under this condition, we introduce the third input signal to extend the three inputs logic gate: full-adder, full-subtractor. We illustrate that the relationship of the half-adder(half-adder) and half-subtractor(full-subtractor). As for the comnpound BHF+, two types full-adder are design in order to joint each other, and then develop a Carry Ripple Adder(CRA), its advantages primarily enhance the molecular circuits integration level and continuity, for the practical application provide a possibility.