Simultaneous External and Internal Heavy-Atom Effects in Binary Adducts of 1-Halonaphthalenes with Trinuclear Perfluoro-ortho-phenylene Mercury(II):  A Structural and Photophysical Study

Abstract

The 1-halonaphthalenes series has often been used to demonstrate the internal heavy-atom effect provided by the halide. In a continuation of our work on the phosphorescence of arenes induced by π-complexation to trimeric perfluoro-ortho-phenylene mercury (1), we now present a structural and photophysical study of the halonaphthalene adducts [1·1-chloronaphthalene] (2), [1·1-bromonaphthalene] (3), and [1·1-iodonaphthalene] (4). The triplet lifetimes in these adducts are considerably shorter than those for the free 1-halonaphthalenes. Analysis of lifetime data versus temperature affords room-temperature phosphorescence quantum yields of 70%, 64%, and 7% for the solid adducts 2, 3, and 4, respectively, compared to 54% for [1·naphthalene]. The photophysical data suggest that the synergy of the internal and external heavy-atom effects has a sensitizing effect for adducts 2 and 3 but a quenching effect for adduct 4 compared to [1·naphthalene]. The luminescence excitation spectra of the solid binary adducts show intense bands that are significantly red-shifted from the absorptions of the individual molecular components, and thus assigned to charge transfer (CT) states. Excitation bands corresponding to the S0 → T1 direct absorption of the 1-halonaphthalene are also detected, albeit much less intense than the CT absorption. The spectral analyses suggest that CT is the major excitation route that leads to the green phosphorescence of adducts 2−4.

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].…”

Coordination chemistry of mercury-containing anticrowns. Self-assembly of unusual supramolecular aggregates in the interaction of the three-mercury anticrown (o-C6F4Hg)3 with crown ethers in the presence of neutral monodentate oxygenous Lewis bases

“…Macrocyclic multidentate Lewis acids or anticrowns 1 represent a novel class of anion receptors and catalysts (see reviews references 2-8 and references cited in recent papers references [9][10][11][12][13][14][15][16][17].…”