Spin-orbit effect on the magnetic shielding constant using the ab initio UHF method. Electronic mechanism in the aluminum compounds, A1X4− (X = H, F, Cl, Br and I)

✍ Scribed by H. Nakatsuji; M. hada; T. Tejima; T. Nakajima; M. Sugimoto

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 384 KB
• Volume: 249
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)01359-8

✦ Synopsis

The 27A1 NMR chemical shifts of the compounds AIX~ (X = H, F, C1, Br and I) are studied theoretically by the ab initio UI-lF/finite perturbation (FP) method including a previously proposed spin-orbit (SO) interaction. When the SO interaction is included, the calculated chemical shifts agree well with experiment. The SO effects become large in the heavier halogen compounds, A1Br~-and Ally. The paramagnetic term and the SO term are important in the chemical shifts of these compounds. The paramagnetic term is governed by the AI valence p electron mechanism and the SO term arises from the Fermi contact interaction in the A1 valence s-orbital. The twofold halogen dependences, namely the normal halogen dependence and the inverse halogen dependence, observed for these compounds arise from the SO effect and the p-electron mechanism, respectively.