om6b00049_si_001.pdf (2.53 MB)
Ditopic N‑Heterocyclic Pincer Carbene Complexes Containing a Perylene Backbone
journal contribution
posted on 2016-02-16, 00:00 authored by Susanne Langbein, Hubert Wadepohl, Lutz H. GadeA new class of ditopic perylene-based
N-heterocyclic pincer ligands,
tetrakis(phosphinomethyl)-1,2,3,8,9,10-hexahydrobenzo[1,2,3-gh:4,5,6-g′h′]diperimidine
derivatives (TPHDP), were synthesized via a one-pot reaction from
3,4,9,10-tetraaminoperylene either directly with the corresponding
phosphine and paraformaldehyde or with the phosphonium salt and triethylamine
as base. In this way the diphenyl-, dicyclohexyl-, and isopropylphosphinomethyl-functionalized
protioligands were obtained (1a–1c). Reaction of 1a–1c with [RhCl(PPh3)3] led to a double geminal C–H activation
and coordination of the ditopic PCP pincer to the rhodium centers,
yielding the rhodium(I)chloro complexes (2a–2c) of all three ligands. These were found to be suitable
starting materials for further ligand exchange of the chloride. Reaction
with lithium phenylacetylide or the abstraction of the chloride ligand
with thallium(I) hexafluorophosphate in the presence of neutral donors
gave the corresponding alkynyl complexes 3a and 3b or the ionic complexes [Rh(Ph3P)]2-Ph-TPHDP (4a) and [Rh(C5H5N)]2-iPr-TPHDP (4b). The most characteristic
feature in the absorption spectra of all compounds is the intense
band of the π* ← π transition of the aromatic (perylene)
core with its partially resolved vibrational progression. The fluorescence
quantum yields (ϕ) of compounds 1a–1c were found to be between 72% and 86%. Upon coordination
to rhodium, the intraligand transition in the absorption spectra is
only slightly shifted, whereas the fluorescence is almost completely
quenched.