Si(IV) complexes of 10,20-diaryl-5,15-diazaporphyrin and 5,10,20-triaryl-5,15-diazaporphyrinoids: Evaluation of charge effect on the optical, redox, and magnetic properties

The central metals in group 14 metalloporphyrins significantly influence the optical, redox, and magnetic properties of the porphyrin [Formula: see text]-electron systems. This study reports the first examples of Si(IV) complexes of 10,20-diaryl-5,15-diazaporphyrin (Ar 2 DAP) and 5,10,20-triaryl-5,15-diazaporphyrin (Ar 3 DAP), designed to explore the effects of meso-nitrogen atoms and net charge on these fundamental properties of the porphyrin ring. Reacting the free base of Ar 2 DAP with HSiCl 3 , followed by metathesis of axial ligands, yielded the corresponding Si(IV) complexes (Ar 2 DAPSiX 2 ; X [Formula: see text] OH, F). Copper-catalyzed [Formula: see text]-phenylation of Ar 2 DAPSiF 2 and subsequent redox reactions produced 18[Formula: see text]- and 19[Formula: see text]-electron derivatives of Ar 3 DAPSiF 2 . Nuclear magnetic resonance spectroscopy, cyclic voltammetry, and density functional theory calculations revealed that the diatropic ring-current effects derived from the aromatic 18[Formula: see text]-electron systems of Ar 2 DAPSiX 2 and Ar 3 DAPSiF 2 strongly depend on the net charge and dipole moment of the DAP ligand. All Si(IV) complexes exhibited fluorescence, with Stokes shifts of 120–310 cm[Formula: see text]. Measurements of fluorescence quantum yields and lifetimes indicated that [Formula: see text]-phenylation primarily reduced the nonradiative decay rate constant. These findings provided insights into the influence of net charge on the aromatic character, as well as the optical and redox properties, of six-coordinate Si(IV) complexes of DAP derivatives.