Accurate measurement of 1 J ( 195 Pt, 14 N) in K[Pt(NH 3 )Cl 3 ] by complete lineshape analysis

Because the 195 Pt triplet due to coupling with 14 N in K[Pt(NH 3 )Cl 3 ] in D 2 O is significantly broadened, 1 J ( 195 Pt, 14 N) determined from the peak separation is not exactly equal to the true coupling constant. It is shown that an accurate value can be determined by a complete lineshape analysis. However, the previously published equation for the lineshape of a spin‐½ nucleus bound to a spin‐1 nucleus is not valid in this case because the intrinsic linewidth of the 195 Pt resonance cannot be ignored. A closed expression for the lineshape is given which accounts for the intrinsic linewidth and gives a value for 1 J ( 195 Pt, 14 N) at 300 K of 235.3±0.2 Hz, in good agreement with the value, 234 Hz, calculated from the published value of 1 J ( 195 Pt, 15 N) and significantly different than the value, 230.4±1.7 Hz, determined from the peak separation. The T 1 of 14 N was measured directly by the inversion‐recovery technique and compared with the values extracted from the lineshape. The lineshape T 1 values were shown to be unreliable unless T 1 ≪ T 2 0 , where 1& sol ; T 2 0 is the intrinsic linewidth of 195 Pt. Also observed was a deuterium isotope effect on the chemical shift of 195 Pt of −2.7 ppm per deuteron bound to N and a temperature variation of 0.74 ppm K −1 for the 195 Pt chemical shift. Copyright © 2001 John Wiley & Sons, Ltd.