Dibenzotetraphenylperiflanthene: Synthesis, Photophysical Properties, and Electrogenerated Chemiluminescence

Fissure coupling of the fluoranthene adduct
(7,12-diphenyl)benzo[k]fluoranthene
(3) using AlCl3/NaCl,
CoF3/TFA, or Tl(OCOCF3) gave the new
polyaromatic hydrocarbon
dibenzo{[f,f’]-4,4’,7,7’-tetraphenyl}diindeno[1,2,3-cd:1‘,2‘,3‘-lm]perylene
(4). Crystal data for 4:  triclinic space
group P1̄, a = 10.569(2) Å,
b = 11.565(4) Å,
c = 13.001(3) Å, α = 95.05(2)°, β =
111.24(1)°, γ = 100.53(1)°, Z = 1,
RF = 0.075%. Compounds 3 and
4 are
both highly fluorescent in solution and display relative fluorescence
quantum yields of φF = 1.0 and 0.85,
respectively.
The electrochemistry and electrogenerated chemiluminescence (ECL)
of each compound has been investigated. The
cyclic voltammogram of 3 in benzene−acetonitrile (9:1)
shows that the compound undergoes a reversible reduction
and an irreversible oxidation, whereas the cyclic voltammogram of
4 displays the reversible formation of both
singly
and doubly charged cations and anions. Compounds 3 and
4 undergo ECL to yield blue and orange-red
light,
respectively, with an ECL efficiency of ∼2% for 4.
Emission from 4 is observed in the ECL of unstirred
solutions
of 3. This indicates that 4 is produced at
the electrode during the ECL experiment, presumably via an
electrochemical
oxidative coupling process during the anodic potential
steps.