Attaching Gold and Platinum to the Rim of Pyrene: A Synthetic and Spectroscopic Study

Abstract

A series of pyrenyl complexes containing one or two AuPPh3 or Pt(PEt3)2Br groups have been synthesized to probe the effects of metal on the absorption and emission properties of the organic molecule. The absorption spectra of the complexes showed perturbation of the metal centers on the pyrenyl ring, as manifested by a red shift of the π → π* transitions of pyrene and intensification of the forbidden 1Lb band. The perturbation increased with the number of metal ions attached to the pyrenyl ring. The Pt ion was stronger than the Au ion in perturbing the electronic structure of the pyrenyl ring. All pyrenyl complexes displayed fluorescence and phosphorescence in degassed solutions. The heavy-atom effect of the metal ions enhanced the phosphorescence. The quantum yield of phosphorescence was sensitive to the positions of metalation.

Dual ligand-based fluorescence and phosphorescence emission at room temperature from platinum thioxanthonyl complexes

“…Thus the energy gap of the π→π*-transition is lowered. 78 As follows from our quantum chemical calculations (vide infra) the (relatively) weak low-energy band corresponds to the HOMO → LUMO transition while several individual transitions contribute to the stronger, structured UV absorption. The energy of the low-energy band remains nearly unchanged upon substitution of the Br − ligand by I − or Cl − while it is shifted by 370 cm −1 to higher energy for the cyanido complex.…”

Palladium‐Catalyzed Pentannulation of Polycyclic Aromatic Hydrocarbons

“…In case of the twofold annulation of 1,6-and 1,8-dibromopyrene (7, 8), both starting materials were synthesized via direct bromination of pyrene according to the procedure of Yip et al [26] This reaction results in 1,6-dibromopyrene (7) and 1,8-dibromopyrene (8) in equal amounts and the separation of 7 and 8 is known to be difficult. [27] When using the mixture for the pentannulation, the desired products 7 a and 8 a were also formed in a 1:1 ratio as expected, but in this case the purification of the isomers was considerably easier.…”

Observation of Room‐Temperature Deep‐Red/Near‐IR Phosphorescence of Pyrene with Cycloplatinated Complexes: An Experimental and Theoretical Study

“…Similar fluorescence emission was previously observed for pyrene-derived Pt II or Au I complexes. [16,22] The emission intensity of the peak at 471 nm is nearly unaffected by O 2 , which is characteristic of fluorescent emissions; the insensitivity to oxygen is due to the singlet manifold and the short luminescent lifetime of the emission. [10] In contrast to Pt-1, the pyrene unit of Pt-2 is not directly cycloplatinated.…”

“…These results contrast those of a previous report that the phosphorescence of pyrene requires direct cyclometallation. [16,22] In the case of new complex Pt-2, intense pyrene-derived r.t. phosphorescence was observed without direct cyclometallation of the pyrene moiety. In addition to the phosphorescence bands in the near-IR range, emissions at higher energy were observed for Pt-1, Pt-2 and Pt-3.…”