Theoretical Study On Excited Hydrogen Bond For Biological Molecules And Metal-organic-frameworks Materials

Hydrogen bond as a weak interaction Hydrogen bond exists in many kinds of systems, as a weak interaction, which is significant to the characteristics of a material. In the excited states, hydrogen bond becomes more important to photochemistry and photophysical properties of the system. For example, fluorescent molecules will be quenched in protonic solvents. The main reason is the modification effect of hydrogen bond between solute and solvent molecules. For some sorption process, hydrogen bond is the dominant effect. Quantam chemistry calculation could provide profound and incisive analysis for experimental results, and even finish some work that is unachievable by experiment. That’s why it has been applied in research more and more widely.As we all know, most biomolecules only carry out their functional in solution. Theorfore, it’s very essential to investigate the interaction between them. Deoxyribonucleic acid (DNA), as the carrier of gene, is one of the most important components for life. In this work, the influence of hydrogen bond weak interaction between deprotoned deoxyadenosine monophosphate ([dAMP-H]-) anion and water molecules, which is one of the minima unit for DNA molecule, on its photochemical and photophysical properties were studied by density functional theory (DFT) method. It’s indicated that the excited state of [dAMP-H]’anion changes from an intramolecular charge transfer (ICT) state to a local excited (LE) state with the increase of water molecules, which is localized on the base moiety. On the other hand, red-shifts of the infra (IR) spectrum is induced by the strengthening of hydrogen bond at base site in the excited state.There’s close relationship between the luminescent mechanism of biological dye molecules and its inactivation process of excited states. Hydrogen bond could monitor the interaction between dye molecules and solvent molecules by its weakening and strengthening in excited state, and then change the proportion of radiation inactivation to irradiation irradiation, at last, decide the photochemical and photophysical properties. Herein, we studied the hydrogen bond dynamics in excited states of luciferin anion (NRO") in aqueous solution by DFT method. It’s observed that hydrogen bond between carboxyl group at peripheral site of the molecule and water molecule is weakened in excited states, which induces the blueshift of its IR spectrum. Metal organic frameworks (MOFs) materials are novel functional material, which is widely used in many fields, such as gas absorption and catalysis. The main interactions for absorption mechanism of small organic molecules sorption are interaction between molecules, π-π stacking and hydrogen bond interaction as the paticularly predominant one. In this work, we provide systematical investigation on the interaction between a MOFs material which is based on Zn4O cluster and small organic molecules (methanal and methanol) by theoretical method. Specific effects of each interaction on different steps of the adsorption curve are discussed. There are mainly three kinds of interactions between them:hydrogen bond, C-H…π interaction and coordination bond like interaction. Moreover, methanol absorption is a two step process; coordination bond like interaction has dominant effect on adsorptive capacity in low pressure; hydrogen bond as a relatively weak interaction is conclusive in high pressure. The predominant effect for methanal absorption is provided by C-H…π interaction.