Study on spectral properties and active sites of glucose and fructose based on density functional theory

Abstract

• Based on density functional theory and time-dependent density functional theory, we systematically studied the infrared spectra, ultraviolet spectra, electron hole, active sites and total transition dipole moments of glucose and fructose molecules • The optical rotation properties of glucose and fructose are explained in detail. • The theoretical study on the molecular structure and properties of glucose and fructose is of great significance for drug research and development, the preparation of biofuels and the protection of related metals. Glucose and fructose are closely related to people's life and production. Based on density functional theory, the B3LYP/6-311++G(d, p) and B3LYP/6-311 + G(d, p) levels of theory are adopted to optimize the structure and calculate the frequency of glucose and fructose molecules by adding B3LYP-D3(BJ) dispersion correction in this paper. The first 50 excited states of glucose and fructose molecules are calculated in SMD solvent model by using time-dependent density functional theory and B3LYP / def2-TZVP level of theory. It is verified that the selected method and basis set are reasonable by comparing the theoretical spectrum with the experimental spectrum. It is found that the plane structure of glucose molecule is more distorted than that of fructose molecule. The stretching vibration of C O bond of fructose is more intense than that of glucose. The absorption peak of fructose at 209.70 nm is characterized by n → σ* transition and is in the tail absorption band, other absorption peaks are all in the far ultraviolet absorption band, and it shows the transition characteristics of σ → σ*. According to the electron-hole analysis, the excitation of the 27th, 34th, 36th and 46th excited states belongs to local excitation, the excitation of the 29th excited state belongs to Rydberg excitation, and the other excited states belong to charge transfer excitation. The optical rotation mechanism of sugar molecules is explained by the direction of the transition dipole moment. O16 of glucose and O24 of fructose were electrophilic site respectively. The active product is 5-hydroxyethyl furfural (5-HMF) by oxidation of 5-hydroxymoms. This study could provide a theoretical basis for drug development, biofuel preparation and metal protection.