Five-Order-of-Magnitude Reduction of the Triplet Lifetimes of N-Heterocycles by Complexation to a Trinuclear Mercury Complex

Abstract

The complexation of N-methylcarbazole and N-methylindole by trimeric perfluoro-o-phenylene mercury (1), which can be readily observed in CH2Cl2 solution, leads to the formation of [1.N-methylindole] (2) and [1.N-methylcarbazole] (3) as solid adducts. The solid-state photoluminescence spectra of these adducts show intense emission bands attributed to monomer phosphorescence of N-methylindole and N-methylcarbazole, respectively, with microsecond lifetimes. Remarkably, the triplet lifetimes of the heterocycles in 2 and 3 are shortened by 5 orders of magnitude when compared to those of the free heterocycles. These results are rationalized by invoking the combined external and internal spin-orbit coupling perturbation provided by the mercury and nitrogen atoms.

Phosphorescence sensitization via heavy-atom effects in d10 complexes

“…Because non-fluorinated coinage metal trimers are electron-rich, particularly gold compounds (Figs. 4, 5, 6), [4][5][6][7][8][9][11][12][13][14][15][16][17] such Au 3 species can complex and sensitize the triplet emission of electron-poor organic molecules such as perfluorinated arenes [8,9,11]. The color chromaticity can be easily improved in phosphors synthesized by the strategies in this section because the emission of the binary adducts is essentially the unperturbed T 1 emission of the arene.…”

“…New adducts have been synthesized which contain an organic aromatic (arene) component and a heavy-metal inorganic component with an opposite p acid-base or donor-acceptor character [4][5][6][7][8][9]. The resulting adducts exhibit sensitized phosphorescence characteristic of the organic aromatic component owing to external HAE of the heavy-metal component in the vicinity of the arene.…”

“…For biphenyl and fluorene, fluorescence quenching experiments could not be carried out because of a large overlap between the absorption spectrum of the mercury trimer quencher and the excitation spectrum of the arene. Synergy between the internal and external heavy-atom effects can be achieved by changing the aromatic substrates to either N-heterocycles (e.g., N-methylindole; N-methylcarbazole) [5] or 1-halonaphthalenes [6]. In comparison to the phosphorescence of the arene alone without the Hg trimer, the triplet lifetimes of the binary adducts are reduced by up to five orders of magnitude.…”

“…The phosphorescence sensitization mechanism involves excitation to a charge-transfer (CT) state before intersystem crossing to the arene T 1 state (Fig. 3) [4][5][6][7].…”

Arene‐Sandwiched Silver(I) Pyrazolates

“…The most widely explored trinuclear d 10 p acid in arene chemistry concerns a Hg II complex [{(o-C 6 F 4 )Hg} 3 ]. [15][16][17][18][19] The research group of Gabbaï has demonstrated its use in the isolation of a series of one-dimensional organometallic polymers (type A) which contain arene donors such as benzene, naphthalene, and pyrene. [20][21][22] During the synthesis of 1, [14] we observed that it was difficult to remove the aromatic solvent from the final product.…”