Interligand Charge Transfer in a Complex of Deprotonated cis-Indigo Dianions and Tin(II) Phthalocyanine Radical Anions with Cp*Ir III .

A diamagnetic complex, {(cis-indigo-N,N)2- (Cp*IrIII )} (1), in which deprotonated cis-indigo dianions coordinate an iridium center through two nitrogen atoms was obtained. By employment of the ability of the iridium center in 1 to coordinate an additional ligand, the complex [(Bu4 N+ )2 {[SnII (Pc•3- )](cis-indigo-N,N)2- Cp*IrIII }•- 2 ·0.5(H2 Indigo)·2.5C6 H4 Cl2 (2), which has two functional ligands coordinating an IrIII center, was obtained. This complex has a magnetic moment of 1.71 μB at 300 K, in accordance with an S = 1/2 spin state. The spin density is mainly delocalized over the Pc•3- macrocycle and partially on (cis-indigo-N,N)2- . Due to an effective π-π interaction, a thermally activated charge transfer from [SnII (Pc•3- )]•- to (cis-indigo-N,N)2- is observed, with an estimated Gibbs energy (-ΔG°) of 9.27 ± 0.18 kJ/mol. The deprotonation of indigo associated with the coordination of IrIII by the indigo releases H+ ions, which protonate noncoordinating indigo molecules to produce leuco cis-indigo (H2 Indigo). One H2 indigo links two (cis-indigo-N,N)2- dianions in 2 to produce strong N-H···O═C and O-H···O═C hydrogen-bonding interactions.