Ab Initio Calculations of 31P NMR Chemical Shielding Anisotropy Tensors in Phosphates: Variations Due to Ring Formation †

International Journal of Molecular Sciences

关键词: NMR;    ab initio;    ³¹P;    GIAO;    Chemical shielding anisotropy;    CSA;    Tensor;    Hartree-Fock;    Phosphates;    Rings;    Cyclization;   

DOI  :  10.3390/i3080888

来源: mdpi

【 摘 要 】

Ring formation in phosphate systems is expected to influence both the magnitude and orientation of the phosphorus (³¹P) nuclear magnetic resonance (NMR) chemical shielding anisotropy (CSA) tensor. Ab initio calculations of the ³¹P CSA tensor in both cyclic and acyclic phosphate clusters were performed as a function of the number of phosphate tetrahedral in the system. The calculation of the ³¹P CSA tensors employed the GAUSSIAN 98 implementation of the gauge-including atomic orbital (GIAO) method at the Hartree-Fock (HF) level. It is shown that both the ³¹P CSA tensor anisotropy, and the isotropic chemical shielding can be used for the identification of cyclic phosphates. The differences between the ³¹P CSA tensor in acyclic and cyclic phosphate systems become less pronounced with increasing number of phosphate groups within the ring. The orientation of the principal components for the ³¹P CSA tensor shows some variation due to cyclization, most notably with the smaller, highly strained ring systems.

【 授权许可】

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