A phosphorescent molecular "butterfly" that undergoes a photoinduced structural change allowing temperature sensing and white emission

A butterfly-like phosphorescent platinum(II) binuclear complex can undergo a molecular structure change in which the Pt-Pt distance shortens upon photoexcitation, which leads to the formation of two distinct excited states and dual emission in the steady state, that is, greenish-blue emission from the high-energy excited state at the long Pt-Pt distance and red emission from the low-energy excited state at the short Pt-Pt distance. This photoinduced molecular structure change has a strong dependence on the molecule's surrounding environment, allowing its application as self-referenced luminescent sensor for solid-liquid phase change, viscosity, and temperature, with greenish-blue emission in solid matrix and rising red emission in molten liquid phase. With proper control of the surrounding media to manipulate the structural change and photophysical properties, a broad white emission can be achieved from this molecular butterfly.