NMR spectroscopy of the phenyl derivative of germanium(IV) 5,10,15-tritolylcorrole

A thoroughly structural characterization of (TTC) GePh (TTC = 5,10,15-tritolylcorrole; Ph = phenyl) in solution has been carried out through a combination of 2D NMR (H-1-H-1 COSY, H-1-H-1 ROESY, H-1-C-13 HSQC and H-1-C-13 HMBC) experiments and density functional theory (DFT) calculations of the molecular and electronic structure and the shielding constants. The H-1 and C-13 chemical shifts computed at DFT-S12g and DFT-SAOP levels of theory nicely reproduce the experimental values, the agreement between theory and experiment being especially good for the DFT-S12g results. The calculations prove to be able to capture the fine details of the NMR spectra and to resolve some assignment ambiguities related to the inherent conformational flexibility of the macrocycle. The calculations also provide an explanation of the observed chemical shift trends in terms of diamagnetic and paramagnetic components of the shielding tensor.