Molecular Design, Synthesis, and Electron Spin Resonance Detection of a Ground-State Tridecet (S=6) Hydrocarbon as a Model for 2D Organic Ferro- and Superpara-Magnets

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Abstract
The electronic and molecular structures of a high-spin carbene oligomer, hexakiscarbene B, having a two-dimensional spin structure were investigated by single-crystal ESR spectroscopy. B was designed on the basis of π-topological symmetry argument, and generated by the photolysis of the corresponding hexakisdiazo precursor A oriented in benzophenone-d10 host single crystals at 2.3K. The observed ESR spectra from B were well reproduced by an exact diagonalization of the spin Hamiltonian with g=2.003, D= +0.01909 cm-1, E= - 0.00193 cm−1, and S=6, proving B to be in the tridecet (S=6) state. The temperature dependence of the total intensity of the tridecet signals proved the observed tridecet state to be the ground state. A semiempirical calculation of the fine-structure tensor yielded the most probable molecular conformation of B in the host crystal.