摘要：

A series of (oligo)pyrroles featuring redox-active terminal ferrocenyl groups (Fc(2)-((C4H2NPh)-C-c)(n) (4, n = 1; 9, n = 2; 16, n = 3; 20, n = 4)) has been prepared using a Negishi C,C cross-coupling reaction protocol. The bi-, ter-, and quaterpyrrole wire moieties have been built up by C,C cross-coupling reactions of trimethylsilyl-protected pyrrole units in the presence of [Pd(CH2C(CH3)2(P)((C4H9)-C-t)(2))(mu-Cl)](2) as precatalyst. The structural properties of the title compounds were investigated by spectroscopic means and single-crystal X-ray diffraction studies (9, 16, and 20). The influence of the increasing number of N-phenylpyrrole units on the electronic interaction between the iron centers was studied using electrochemistry (cyclic (CV) and square wave voltammetry (SWV)) as well as spectroelectrochemistry (in situ UV/vis/near-IR spectroscopy). With the exception of the diferrocenyl quaterpyrrole 20, the application of [(NBu4)-Bu-n][B(C6F5)(4)] as electrolyte allows the discrete oxidation of the ferrocenyl termini (Delta E degrees' = 450 mV (4), Delta E degrees' = 320 mV (9), Delta E degrees' = 165 mV (16)) in cyclic and square wave voltammograms. However, the iron centers of 20 were oxidized simultaneously, generating dicationic 20(2+). Additionally, one (9) or two (16 and 20) pyrrole-related well-defined reversible one-electron-redox processes were observed. The cyclic voltammetry data reveal that the splitting of the ferrocene-based redox couples, Delta E degrees', decreases with increasing oligopyrrole chain length and, hence, a greater metal-metal distance. The trends in Delta E degrees' with oligopyrrole structure also map to the electronic coupling between the ferrocene moieties, as estimated by spectroelectrochemical UV/vis/near-IR measurements. Despite the fact that there is no direct metal-metal interaction in diferrocenyl quaterpyrrole 20, a large absorption in the near-IR region is observed arising from photoinduced charge transfer from the oligopyrrole backbone to the redox-active ferrocenyl termini. These charge transfer absorptions have also been found in the dicationic oxidation state of the mono-(4), bi- (9), and terpyrroles (16). Within this series of diferrocenyl(oligo)pyrroles this CT band is shifted bathochromically with increasing chain length of the backbone motif.

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