Synthesis And Application Of Quinolin2-methenyl Malonic Acids And Their Esters

Thiols are an important class of molecules in biological systems and chemical science. Several aliphatic thiols including Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play essential roles in many physiological processes, abnormal levels of cellular thiols are associated with many human diseases. As a result, detection of thiol compounds is of great significance in biological field. In this paper, several quinolin2-methenyl malonic acid (QMA) were designed and applied to detect thiol as fluorescent probe both in the solution and cell environment, meanwhile, they are also utilized to construct molecular arithmetic systems.In the chapter2, the fluorescent probe, hydroxyl substituted quinolin2-methenyl malonic acid (QMA), was synthesized, which could react with thiols via Michael reaction with great fluorescence enhancement. The probe only reacts with thiols in acidic solutions (pH<7), as comparison, its ester derivative (QME) was obtained and reveals a contrary pH sensing behavior like reported probes. The new sensing reaction of QMA carries out the unprecedented sensing mechanism via an intra-and intermolecular H-bond activated Michael addition under acidic conditions. Selectivity experiment indicates QMA only respond to thiols. Furthermore, the fluorescence images for cellular thiols exhibit that QMA can detect thiols specificly in the acidic compartments of cells such as lysosomes, and QME can detect biothiols in the slightly alkaline cytosol.In the chapter3, QMA was further modified with amine and ester groups to yield QMAE, it’s utilized as fluorescent probe for detecting bio-thiols selectively and quantitatively with ratiometric fluorescence signaling response. The probe functions via Michael addition reaction on the base of ICT-tuning mechanism, which has been rationally confirmed by DFT calculation and solvent effect. Thiol imaging in live cells were performed on QMAE and the probe displayed excellent fluorescence transformation as expected under both one-and two-photon excitation conditions.In the chapter4, two compounds with pH-sensitive functional groups,2-quinolin-2-ylmethylene-malonic acids (QMA-1and QMA-2), have been prepared for molecular algebraic operations. These compounds can exist in several ionization forms (cations, neutral and anions), each of which has distinct spectral properties, and be applied in the construction of "four-state" molecular switch and following acid/base-boosted molecular Boolean arithmetic functions including half-subtractor, half-adder, full-subtractor and full-adder. These systems are resettable after each separate arithmetic operation.In the chapter5, we prepared two classes of model compounds, covalently N-linked dimer-(1) or oxetane-carbazole (2) compounds. Under light irradiation, the dimer or the oxetane unit of model compounds can be sensitized by carbazole moiety to split by the carbazole via an intramolecular electron transfer. The splitting reaction of dimer or oxetane unit in model compounds is strongly solvent-dependent. In non-polar solvents, no fluorescence quenching of the carbazole moiety of model compounds relative to N-methylcarbazole was observed, and thus no splitting occurred. In polar solvents, two classes of model compounds reveal two reverse solvent effects on the splitting quantum yield. The solvent effect is an inverse relation between the quantum yield and polarity of the solvent for dimer-model systems, and a normal relation for oxetane-model systems. Based on Marcus theory and thermodynamic data, it has been rationalized that the two reverse solvent effects derive from back electron transfer in the splitting process, which lies in the different Marcus regions.