Influence of the Steric Factor on the Structure of Indium(III) Iodide Complexes Based on Substituted o-Iminobenzoquinones

Based on a series of substituted o-iminobenzoquinones (6-((2,6-di-iso-propylphenyl)imino)-2,4-bis(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L¹), 4-(tert-butyl)-6-((2,6-di-iso-propylphenyl)imino)-3-methoxycyclohexa-2,4-dien-1-one (L²), and 6-((2,6-di-iso-propylphenyl)imino)-3-methoxy-4-(2,4,4-trimethylpentan-2-yl)cyclohexa-2,4-dien-1-one (L³)), indium(III) iodide complexes were synthesized containing a redox-active ligand in the neutral form. The o-iminobenzoquinone L¹ was synthesized for the first time. It was found that the structure of the obtained complexes depends on the degree of shielding of the carbonyl oxygen atom in the starting o-iminobenzoquinone. The sterically hindered L¹ forms a 1 : 1 adduct with InI₃ (complex (L¹)InI₃ (I)). The absence of a substituent at position 2 of the o-iminobenzoquinone ring promotes the formation of bisligand ionic derivatives {[(L²)₂InI₂]InI₄} (II) and {[(L³)₂InI₂]InI₄} (III). The molecular structure of L¹ and complexes I·0.5 toluene, II·toluene·0.5 hexane was established by X-ray diffraction analysis (CCDC nos. 2440874 (L¹), 2440875 (I·0.5 toluene), 2440876 (II·toluene·0.5 hexane)). The optical and electrochemical properties of the starting o-iminobenzoquinones and their indium(III) complexes were studied. It was shown that complexation significantly enhances the oxidative properties of L¹, L², and L³.