Synthesis,Properties And Interaction With DNA Of A₂B Type Metallocorroles

Corroles,as an 18 ? conjugated porphyrin derivatives,are typical building blocks of several natural products such as VB12. In coordination chemistry, corroles could be used as strong ligands to stabilize high-valence metal-center. A2B type corrole derivatives with lower symmetric molecular framwork, novel molecular and electronic structure,show their potential application in a wide range of fields especially in DNA modification. DNA molecule acting as the carrier of genetic information becomes the main target molecule for most of small molecules which can interact with and damage the template function of DNA, break the chains of nucleic acids and therefore misleading the gene regulation and expression. Corroles are often used as drugs and medicine recently; hence their uncertainty to human body is quite an important concerning.This work aims to investigate the A2B type corroles and their metallocomplexes,in particular their synthetic routes, their electronic structure and the interaction nature with DNA. To this end, twenty-six corroles and metallocorroles were systematically designed and their properties were characterized by a variety of techniques including spectroscopy, electrochemistry, spectroelectrochemistry and TD-DFT calculations.The electronic structure of the investigated molecules and its function in affecting the catalytic and/or bonding efficiencies were thoroughly investigated. The main findings are shown below:1. Seven halogen-substituted A2B type corrole free bases were synthesized in H2O-MeOH solution. Spectral and TD-DFT studies indicated that the modulation on electronic structure could be achieved through changing solvent polarities. The NH tautomerism changed as the solvent polarity varied. In particular, a red-shift of the main absorption was observed as increasing the solvent polarity, which was attributed to an intramolecular charge transfer led by the NH tautomerism.2. Seven halogen substituted cobalt corroles were successfully synthesized and purified via the reaction of cobalt salt with their corresponding free base corroles.Their molecular structures were supported by NMR measurements and crystallographic analysis. The electronic structure could be simply modulated by tailoring even only one meso-substituent in these compounds. Essentially, a unique two-step modulation of hydrogen evolution reaction (HER) through one meso-substituent was firstly verified, and the relationship between the electronic structure and catalytic efficiency were also investigated by spectroscopy,electrochemistry and TD-DFT calculations.3. m-Nitrophenyldipyrromethane was introduced to synthesize a series of copper corroles containing zero-to-five fluorine atoms. A blue-shifted absorption was observed as the increment of fluorine atom numbers in these synthesized compounds.This is due to the fact that the larger numbers the fluorine atom, the more electron-deficient the electronic structure. The HER efficiency was also enhanced by increasing the fluorine atom numbers, which possibly suggested that the electron-deficient molecules possess promising electrocatalyzed hydrogen evolution activity.4. Four copper corroles with push-pull meso-substituents were successfully synthesized. Supported by the electronic structure investigation, introducing moieties with both electron donating (push) and withdrawing (pull) abilities decreased the energy gaps between HOMO and LUMO significantly, red-shifting their main absorption spectra to NIR region. In addition, the HER efficiency of the molecules was also influenced by the push-pull effect.5. Four mangaese corroles with push-pull meso-substituents were further synthesized. As compared to traditional manganese corroles, these compounds exhibited novel electronic structure with a broadened absorption to NIR region. An evaluation on the interaction between Mn-Corroles and ctDNA revealed that Mn-Corroles can quench the fluorescence of EB-DNA, and more interestingly, the quenching dynamic could be systematically modulated by tuning the meso-substituents.In conclusion, 26 different corroles and metallocorroles were successfully prepared and these compounds with novel molecular structure, electronic structure,have interesting properties in the spectroscopic, electrochemical,spectroelectrochemical investigations. These findings suggested that the A2B type corroles and their metallocomplexes could be used as successful electrocatalysts in the HER and sensitive probe molecules with DNA interaction.