The Tm values for 1-Ln complexes studied are all similar, around the 1 μs mark. These are ample to allow further investigation of the complexes by multipulse microwave sequences. In order to quantify the weak hyperfine interactions between the electron spin(s) and surrounding 1 H and C nuclei, we employed two-dimensional hyperfine sub-level correlation (HYSCORE) spectroscopy, which uses a four-pulse spin echo envelope modulation sequence; π/2 -τ -π/2 -t1 -π -t2 -π/2 -echo, with t1 and t2 independently varied. In the HYSCORE experiment the first two π/2 pulses generate nuclear coherences, which are then transferred between electron spin states by the π pulse. In the 2D frequency domain spectrum, cross-peaks appear for weakly-coupled nuclei (2|νn| > |A|) in the (+, +) quadrant straddling the nuclear Larmor frequencies (νn). Ridges in the spectra are due to the anisotropic hyperfine couplings. X-band HYSCORE spectra measured at static magnetic fields corresponding to orientations in the molecular xy plane for 1-Nd and 1-Ce (B0 = 353.0 and 348.2 mT, respectively) reveal signals from C and 1 H nuclei (Figure ). HYSCORE signals for 1-Sm were too weak to detect when measured under similar conditions; this does not appear to be relaxation limited given the similar Tm (see above), and may be a function of the very low effective g-values. The 13 C features for 1-Nd and 1-Ce are similar, consisting of a ridge extending beyond the C Larmor frequency by ca. ± 1 MHz. The 1 H features are also similar, with a ridge extending νn ± 2.5 MHz.