Lanthanide shift reagents. A novel method for fitting the pseudocontact shielding equation to experimental induced shifts

✍ Scribed by J.W. ApSimon; H. Beierbeck

• Publisher: Elsevier Science
• Year: 1973
• Tongue: French
• Weight: 198 KB
• Volume: 14
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)95851-4

✦ Synopsis

It is generally accepted l-9 that chemical shifts induced by lanthanide shift reagents are predominantly or entirely due to a dipolar shielding mechanism. Assuming axial symmetry lo the dipolar shifts Ai are given by the McConnell-Robertson equation (1)11 where C is a proportion-Ai = C(I -3cos2ei)/Ri3 (I) ality constant, Ri is the vector from the metal to the i'th nucleus and ei is the angle between the principal axis of the chelate and Ri. The principal axis of the complex is usually taken 12 to be colinear with the metal-ligand bond . Structural information is extracted from the induced shifts by fitting the pseudocontact equation (1) to the experimental hi, usually by incremental variations of the proportionality constant C and the lanthanide metal coordinates