Pressure-induced emission enhancement of a series of dicyanovinyl-substituted aromatics: pressure tuning of the molecular population with different conformations.
A series of dicyanovinyl-substituted aromatic compounds (Ar-DCV; Ar=9-anthracenyl, 1-naphthyl, 1-pyrenyl) with dual fluorescence are prepared, and their emission properties--when molecularly dispersed in a polymer medium--are investigated under pressure perturbation. The total emission intensity is enhanced drastically from ambient pressure up to 70 kbar. Emission 30-107 times more intense than that at ambient pressure is observed at higher pressure. In dual emission, the enhancement of the local excited state (LE state) is significantly different from that of the intramolecular charge-transfer state (ICT state). The intensity of the ICT emission increases faster (30-370 times) than that of the LE emission (less than 20 times). In accordance with spectroscopic data, emission dynamics at different pressures, and computational studies on the molecular conformations of these compounds, a kinetic model is proposed to explain the effect of pressure on the emissive properties of the Ar-DCV compounds from the point of view of pressure-dependent populations of the species in the ground state.
Wang
Qian
Q
Beijing National Laboratory for Molecular Sciences, Key laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China.
Li
Shayu
S
He
Liming
L
Qian
Yan
Y
Li
Xiuping
X
Sun
Wenhao
W
Liu
Min
M
Li
Juan
J
Li
Yi
Y
Yang
Guoqiang
G