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Synthesis and Chiroptical Properties of Hexa‐, Octa‐, and Deca‐azaborahelicenes: Influence of Helicene Size and of the Number of Boron Atoms

2016; Wiley; Volume: 23; Issue: 2 Linguagem: Inglês

10.1002/chem.201604398

1521-3765

Chengshuo Shen, Monika Srebro‐Hooper, Marion Jean, Nicolas Vanthuyne, Loïc Toupet, J. A. Gareth Williams, Alexis R. Torres, Adrian J. Riives, Gilles Muller, Jochen Autschbach, Jeanne Crassous,

Organoboron and organosilicon chemistry

Four members of a new class of cycloborylated hexa-, octa-, and deca-helicenes (1 a-d) have been prepared in enantiopure form, along with two cycloplatinated deca-helicenes (1 d', 1 d1 ), further extending the family of cycloplatinated hexa- and octa-helicenes reported previously. The azabora[n]helicenes display intense electronic circular dichroism and large optical rotations; the dependence of the optical activity on the size of the helix (n=6, 8, 10) and the number of boron atoms (1 or 2) has been examined in detail both experimentally and theoretically. The photophysical properties (nonpolarized and circularly polarized luminescence) of these new fluorescent organic helicenes have been measured and compared with the corresponding organometallic phosphorescent cycloplatinated derivatives (1 a1 -d1 ).