A novel crystal material melts under ultraviolet light

Melts in the light, not in your hand.


The phenomenon of crystal melting by light irradiation, known as a photoinduced crystal-to-liquid transition (PCLT), can dramatically change material properties with high spatiotemporal resolution. However, the diversity of compounds exhibiting PCLT could be much higher.

Recently, scientists from Osaka University reported about a novel material that changes its state when exposed to ultraviolet irradiation. When induced by ultraviolet light, this novel material transitions from a crystal to a liquid and exhibits changes in luminescence.

What’s more interesting, the material changes in its luminescent properties while melting. This is the first organic crystalline material that changes its luminescence and intensity upon ultraviolet light-induced melting.

Autocatalytic conformation change
Autocatalytic conformation change Credit: Yosuke Tani

This new class of photo-responsive crystal compounds, ‘heteroaromatic 1,2-diketones,’ melts because of light irradiation. This phenomenon alters materials’ properties and makes the material ready to be used in several applications, such as photo-responsive, reversible adhesives that can be controlled by light.

While discovering this new class of material. Scientists found that one member of this class, the diketone’ SO,’ shows changes in luminescence during the irradiation-induced melting process. This change signifies that SO was undergoing molecular-level changes in shape during the PCLT process.

Senior author Yosuke Tani said, “We found that the changes in luminescence arise from sequential processes of crystal loosening and conformational changes before melting. These visual indications of the steps of the PCLT process enabled us to advance the current understanding of crystal melting at the molecular level.”

Scientists applied several techniques, such as single-crystal X-ray analysis, thermodynamic property analysis, and theoretical calculations, to determine the mechanism behind the behavior of this new PCLT material. They found a disordered layer in the crystal that plays a vital role in PCLT.

Journal Reference:

  1. Mao Komur, ORCID logo, Hikaru Sotome, Hiroshi Miyasaka, Takuji Ogawa and Yosuke Tani. Photoinduced crystal melting with luminescence evolution based on conformational isomerization †. Chemical Science. DOI: 10.1039/D3SC00838J


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