Probing the Conformational Behavior of a Seven Hetero-Spin Supramolecule

Abstract The synthesis and crystal structure of a 7-spin supramolecular poly-rotaxane is reported. The [4]rotaxane structure involves a trigonal thread centred on a {CrNi2} core, with each of the three arms terminated by Cu(II) centres and bearing a {Cr7Ni} metallocycle. The macromolecule brings together three distinct electron spin centers. Continuous-wave electron paramagnetic resonance spectroscopy confirms the molecule remains intact in solution, with the three types of spin center each uniquely addressable. Orientation-selective Double Electron Electron Resonance (DEER) and Relaxation Induced Dipolar Modulation Enhancement (RIDME) spectroscopies are used to selectively probe the different spin-spin interactions in the frozen solution phase and to define differences from the solid-state crystal structure.