Donor-acceptor solids [(C6Me6)2Me2+][iso-C4(CN)62-].MeNO2 (M = Fe, la; M = Ru, 2a) and [(C6Me3H3)2M2+][iso-C4(CN)62“] (M = Fe, 1b; M = Ru, 2b) prepared from (arene)2M2+ and iso-C4(CN)62- are described. Single-crystal X-ray studies show that la crystallizes in the space group P21/c with a = 19.875 (6) Å, b = 10.512 (2) Å, c = 15.981 (4) Å, β = 96.65 (3)°, V = 3316 (3) Å3, p = 1.36 g cm-3, Z = 4, Ru = 0.061, and Rw= 0.080. The ruthenium analogue 2a also crystallizes in the space group P21/c with a = 19.973 (2) Å, b = 10.553 (2) Å, c = 16.144 (1) Å, β = 96.80 (7)°, V = 3378 (3) Å3, p = 1.36 g cm-3, Z = 4, Ru= 0.070, and Rw= 0.068. Both complexes exhibit “zigzag” linear chains of closely spaced alternating cations and anions. Donor-acceptor interactions arise from close intermolecular contacts between the C6Me6 ligands of the dications and nitrogen atoms of the nonplanar dianion with dianions “bridging” the dications via three of its cyano groups. The complexes exhibit strong charge-transfer bands and are best described as donor-acceptor (DA) complexes with nominally doubly charged (D2-A2+) ground states and (D-A+) excited states. The difference between the charge-transfer absorption energies of 1 and 2 is equivalent to the difference in the solution reduction potentials of the isostructural (arene)2M2+ cations. The structure of the 19e (C6Me6)2Fe+ monocation, reported here for the first time, is essentially identical with that of the 18e dication, suggesting that the charge-transfer transitions of these DA complexes can occur without the formation of energetically unfavorable molecular conformations.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry