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Study on the Color Development of Anthracene Diindolyl Methane Oxide
- Oct 17, 2019 -

In the field of chemistry and life science, the study of anion recognition is a major focus that people often pay attention to. Since the first synthesis of the main compounds for anion recognition in 1968, the design and synthesis of artificial analog receptors with selective recognition of anions have made great progress. Anion recognition can take many different ways, such as electrostatic action, hydrogen bond, ion dipole interaction. Among them, deproton reaction under the action of anions has attracted wide attention due to its high color sensitivity. In the synthesis of many ion sensors, people connect light signal chromophore with anion receptor through covalent connection, because the sensor molecules can selectively combine with anions, so that it can absorb or emit. The structure of the oxidized diindolylmethane compounds is novel. These compounds contain an acidic H-bond donor and an alkaline H-bond acceptor, which can not only give out protons, but also have the binding point of protons, so it is easy to adjust the charge transfer within the molecule and produce large color changes. In this paper, Allium group with high fluorescence quantum yield was introduced into the oxidized diindolylmethane, and the binding site with Allium group was changed in the way of introduction, so as to investigate the changes of spectral behavior of these compounds in solution and their ability to recognize anions. Some interesting results were obtained.

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In the design and synthesis of oxidized diindolylmethane, onion group with high fluorescence quantum yield was introduced, and onion group with different action sites was introduced to investigate the change of emission spectrum characteristics of these compounds. Unfortunately, there was no obvious fluorescence emission of compounds 2-anbim and 9 anbim in various solvents at room temperature. At 77K, they were excited in ether solution at 420nm. The maximum emission peaks are about 570nm (2-anbim) and 516nm (9-anbim) respectively, both of which belong to intramolecular charge transfer state (ITC).

In compound 2-anbim and 9anbim, although there is a certain angle between onion plane and diindon noise plane, there is a considerable degree of co effect. The carbon atom at β position of indole ring and the carbon atom connecting onion ring and indon noise ring are all SP2 hybrid, so the whole molecule has a certain degree of CO planarity. At 77K, due to the significant weakening and disappearance of various non radiation inactivation processes, the two have a great deal of CO planarity. At room temperature, the excited state 1 is converted into 2 and 3 by resonance, and 4 can be obtained by proton transfer, while the carbon atom at the β position of one heterocycle of 4 is converted into SP3 and loses the joint with onion ring and the heterocycle on the other side, and the degree of coplanarity of the whole molecule is greatly reduced, thus losing the luminescent ability.

To sum up, compounds 2-anbim and 9 anbim contain acid H-bond donor and basic H-bond receptor, which are the basic reasons for the color change of these compounds due to their sensitive response to medium polarity, pH and anion. Therefore, these compounds should be color sensors. Both the concentration effect and H-NMR evidence show that there are molecules based on hydrogen bond in CCH. Interaction. Compared with the absorption behavior in other aprotic solvents, the nature of red shift phenomenon of compounds in CCl4 is not clear. The selective absorption of anions by compounds in acetonitrile system makes these compounds can be used for the identification of f-plant ions or other limited anions (such as CT and AC ions) in acetonitrile system. The rapid proton transfer process in excited state can It can reduce the degree of coplanarity and coplanarity of the molecules, so that the two compounds have no obvious fluorescence emission at room temperature. In the frozen state (77K), the fast proton transfer process is restrained, and all the compounds show ICT fluorescence emission. Because of the good planarity of 2-anbim, the fluorescence emission of 2-anbim at 77K has a considerable red shift and a larger luminous intensity than that of 9-anbim.

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