Gold-lead derivatives

The absorption spectrum of the gold-lead complex shows two bands at 290 nm (e = 28598 M-1cm-1) and 385 nm (e = 7626 M-1cm-1), while the emission spectrum in the solid state shows only one band at 752 nm at room temperature. It was assigned to a transition between orbitals that appear as a result of the gold-lead interaction. Thus Fenske-Hall molecular orbital calculations indicated that the HOMO is constituted from the 6pz orbital of gold and 6s orbital of lead and the LUMO is entirely constituted from the 6pz orbitals of these atoms. 

The behavior of this complex in solution is interesting since its emission spectrum shows a strong dependence on the aggregation state and temperature. Thus the emission band in THF solution, which appears at 555 nm (298 K) (t = 57 ns), is shifted to 480 nm in frozen solution (t = 2.3 ps) or appears at 752 

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Figure 19a shows, as an example, single stretching traces and the ID histogram of molecular junctions created between the dinitrile derivative N4, torsion angle p = 44.8, and two gold leads. The predominant peak with a maximum at Gmax = 4 x 10 5 G0 is attributed to the most probable conductance [54]. 

The most common strategy in the synthesis of heteronuclear complexes is the use of bidentate donor ligands bearing different donor centers. In that way both donor atoms can be coordinated selectively to two different metal centers in a consecutive way. If the space between the donor atoms of the ligands is short, interactions between both metals usually appear, normally intramolecular. Sometimes, albeit not very often, the bidentate units bind to one another, leading to extended structures through metallophilic interactions. As we have commented, in the case of gold-silver derivatives the number of luminescent studies of these derivatives is very scarce. 

No simple salts of 2,1 -benzisothiazole have been described in the literature, other than those of amino-substituted derivatives,101 in which the site of protonation is probably the cyclic nitrogen atom, at least in the 3-substituted compounds. The parent compound does, however, form a simple crystalline nitrate 114 which is not very stable. A number of complex salts with platinum, gold, lead, and mercury salts and with picric acid have been described.96,97,116 The picrate is highly crystalline and stable, and is useful for the isolation and characterization of 2,1-benzisothiazole. Many substituted 2,1-benzisothiazoles form similarly useful picrates.106... 

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