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{[ff]-4,4',7,7'-tetraphenyl}diindeno[1,2,3-cd: 1',2',3'-lm]perylene (4). Crystal data for 4: triclinic space group <P(1)over bar>, a = 10.569(2) Angstrom, b = 11.565(4) Angstrom, c = 13.001(3) Angstrom, alpha = 95.05(2)degrees, beta = 111.24(1)degrees gamma = 100.53(1)degrees, Z = 1, R(F) = 0.075%. Compounds 3 and 4 are both highly fluorescent in solution and display relative fluorescence quantum yields of phi(F) = 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 3 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 similar to 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.