Efficient identification of different types of carbons in organic solids by 2D solid-state NMR spectroscopy

An efficient method for identifying different types of carbon groups (CH(3), CH(2), CH, and quaternary carbons) in organic solids is proposed by utilizing the combination of a two-dimensional (2D) (13)C-(1)H polarization inversion spin exchange at magic angle (PISEMA) NMR experiment and numerical simulation results of simple isolated (13)C-(1)H dipolar coupling models. Our results reveal that there is a unique line shape of the (13)C-(1)H dipolar splitting pattern and a corresponding characteristic splitting value for each carbon group, based on which different carbon types can be distinguished unambiguously. In particular, by using this method, the discrimination and assignment of overlapped signals from different types of carbons can be achieved easily. The efficacy of this method is demonstrated on typical solid small molecules, polymers, and biomacromolecules.