Mechano-responsive circularly polarized luminescence of organic solid-state chiral emitters
Chem. Sci., 2019,10, 843-847.
Marine Louisa, Ramarani Sethyb, Jatish Kumarb, Shouhei Kataob, Régis Guillotc, Takuya Nakashimab, Clémence Allain*a, Tsuyoshi Kawai*b and Rémi Métivier*a
a PPSM, ENS Cachan, CNRS, Université Paris Saclay, 94235 Cachan, France
b Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
c ICMMO, Université Paris-Sud, CNRS, Université Paris-Saclay, 91405 Orsay, France
Two difluoro-boron β-diketonate complexes bearing chiral amido groups have been synthesized. Their mechano-responsive luminescence and chiroptical properties have been investigated in the solid state. Both compounds display a bright blue-green emission and a significant circularly polarized luminescence (CPL) signal in the crystalline state, with |glum| values as high as 2.2–2.4 × 10−2. A bathochromic shift in emission, together with a decrease of |glum| values to c.a. 3 × 10−3, is induced upon application of a shearing stress. For the DFB-Hex-amide compound, interestingly, sign inversion of the anisotropy factor glum is observed under mechanical stimulation (“mechano-CPL effect”), which can be rationalized by a switching between monomer and excimer emission.
Source : Chem. Sci.