Molecules design producing circular light that changes color for 3D screens and safety printing

Certain advanced technologies, such as 3D screens, biosensation and safety printing, can use circularly polarized luminescence (CPL), which occurs when specific types of molecules radiate with UV light. The CPL electric field rotates spirally. Mechanical changes in these molecules, such as grinding, can induce a transition that creates a reversible emission color change. This is called typocromic luminescence (MCL).

To improve CPL efficiency after rectification, the researchers tested two easily available compounds to understand how CPL properties changed to the grinding. The results were published in ANGEWANDTE CHEMIE INTERNATIONAL EDITION January 22.

“The polarized luminescence circular (CPL) exhibited by the chiral molecules is very promising for applications in areas such as three -dimensional screens and safety printing., A significant challenge based on the substantial reduction of CPL efficiency when the crystals are loved by mechanical stimuli “Suguru Ito, an associate professor of engineering at the National University of Yokohama in Yokohama, Japan, said.

It has been found that small chiral organic molecules are very beneficial to produce CPL. Quiral means that the molecule cannot overlap in its mirror image. The chirality is important for CPL because it is a light that rotates in a circular way. The chirality of the molecule can help direct the direction of the rotation of light.

Understanding the other molecular properties that can determine CPL behavior could help researchers create better design strategies for chiral organic molecules. An important step is to develop mechanochromic CPL. When mechanical CPL has been studied in the past, the grinding required to induce color change also induced structural changes to the crystals that weakened the CPL.

The researchers used two molecular compounds called pirenylprolinamides Quirals 1 and 2, which exhibit different colors of luminescence in the glass state. Both are designed to include an amino acid that gives the molecule its chiral shape, a pyren R substituent that controls the disposition of the glass state. The first pyrenylprolinamide is a derivative of third-butarbonyl (Boc). The second pyrenylprolinamide is a derivative of 2,2,2-trusoToxicarbonil (TROC).

The results helped identify the best way to design the molecules to produce mechanochromic CPL depending on the desired properties.

“We have demonstrated for the first time that the Excimer chirality rule can be applied to acquire structural information about the exciteers formed in the amorphous state. The most notable, in contrast to the previous reports where CPL almost disappeared after grinding, this study this study It shows that the pyrenos stacked by intermolecular hydrogen bonds, promotes the emission of exciteers even in amorphous states.

Looking towards the future, researchers hope to establish guidelines. “The next step is to establish general design guidelines for molecules that allow the change of CPL in solid state through mechanical stimuli. Our ultimate goal is the generalized implementation of materials with Switching solid state CPL for applications such as three -dimensional screens and printing of printing security”. Ito said.

Other taxpayers include Shin Wakiyama and Hao Chen of the National University of Yokohama; Masato Abekura and Hidehiro Uekusa of the Tokyo Institute of Technology; and Ryoya Ikemura and Yoshitane Imai of the University of Kindai.