ABSTRACT
A series of tetranuclear silver(I) chalcogenide complexes [Ag4^ -dppm )4(p4-E)]2+ [E = S (41a), Se (41b), Те (41c)] have been isolated and characterized in our laboratory [117]. The structures of these complexes are analogous to the tetranu clear copper(I) chalcogenides 12a-c [68-70]. The similarity of the structures of these complexes enables comparison of the photophysical properties of this class of complexes. The UV-Vis absorption spectra of these tetranuclear silver(I) chal cogenides reveal a high-energy intraligand (dppm) absorption at around 246256 nm and a lower energy absorption in the 350-to 460-nm region. Excitation of the complexes in the solid state and in fluid solutions results in long-lived green to orange luminescence. The photophysical data are summarized in Table 9. Similar to the related copper chalcogenide complexes, the emission of these silver(I) complexes has been assigned to be associated with a 3LMCT [E2~ —> Ag4], mixed with a metal-centered (ds/dp) triplet state. The solid-state emission energy of [A g ^ -d p p m ^ ^ -E )]2* follows the order 41a (516 nm) > 41b (527 nm) > 41c (574 nm). The emission spectra are shown in Fig. 7. This energy trend is in line with the ionization energies of the chalcogens and lends further support to the excited state assignment of large LMCT character. Besides, the small blue shift of around 0.27 eV in emission energy from [Cu4(p-dppm)4^ 4E)]2+ to [Ag4(p-dppm)4(p4-E)]2+ (E = S, Se) disfavors the assignment of an MLCT state, for which the shift should be more significant.
