om201007g_si_001.pdf (1.54 MB)
Amide-Linked Heterobi- and Heterotermetallocenes with Very Low HOMO–LUMO Gaps
journal contribution
posted on 2012-01-09, 00:00 authored by Hannah Huesmann, Christoph Förster, Daniel Siebler, Teuta Gasi, Katja HeinzeThe novel heterobi- and heterotermetallocenes [Fc-NHCO-Cc]+ (1) and [Fc-NHCO-Cc-CONH-Fc]+ (2) have been prepared by amide coupling of aminoferrocene
and cobaltocenium carboxylic acid or 1,1′-cobaltocenium dicarboxylic
acid. Very small differences of the redox potentials, ΔG0 ≈ 1 V, were observed due to the electron-donating
and electron-withdrawing nature of the substituents at the ferrocene
and cobaltocenium units, respectively. In accordance with this small
zero-level energy difference, ΔG0 is the low-energy MM’CT absorption that extends into the
near-infrared spectral region. Large solvatochromic shifts were observed
for 1 and 2 due to the pronounced difference
in ground-state and excited-state dipole moments. The low-energy optical
transitions were assigned as MM’CT transitions by DFT-PCM and
TDDFT-PCM approaches, and the experimental negative solvatochromic
effect has been reproduced by the TDDFT-PCM calculations.