Evaluation of potential ferromagnetic coupling units: the bis(TMM) [bis(trimethylenemethane)] approach to high-spin organic molecules

• DOI: 10.1021/ja00058a020
• Publication Date: 2005-03-19T01:55:14Z
• Authors: S. Joshua Jacobs; David A. Shultz; Rakesh Jain; Julie Novak; Dennis A. Dougherty
• Keywords: 500; 540; 01 natural sciences; 0104 chemical sciences

Four new hydrocarbon tetraradicals, 1-4, each composed of two triplet trimethylenemethane (TMM) subunits linked by a potential ferromagnetic coupling unit (FC), were synthesized and characterized by variable-temperature electron paramagnetic resonance (EPR) spectroscopy. Simulation of the EPR powder spectra and a priori calculation of the zero-field splitting parameters aided spectral assignment. The Heisenberg Hamiltonian appears to quantitatively model relative spin-state energies in 1-4. In three cases ferromagnetic coupling was achieved, as evidenced by quintet ground states in the resulting tetraradicals. In one case, strong evidence for antiferromagnetic coupling was obtained.