Magnetic force microscopy images of a nanometer-sized purely organic high-spin polyradical

Magnetic force microscopy (MFM) was applied to study both the molecular image and the magnetic response of pi-conjugated, non-Kekule-, and nondisjoint-type poly(1,2-phenylenevinylene) (nondisjoint refers to a molecule in which non-bonding molecular orbitals share the same region in the molecule and a multiplet ground state is significantly stabilized) networks bearing 4-substituted di-tert-butylphenoxyl moities. The polyphenoxyl radicals 1 with molecular weights of 2.6, 9.3, and 32 kDa have a substantial stability even at room temperature and in air, and molecular sizes in the nanometer range of 10, 20, and 35 nm, respectively, with a disk-like shape. The MFM clearly shows a magnetic gradient response exactly on the position of the polyradical molecule dispersed on a graphite surface. The MFM molecular image of polyradical samples with different molecular weights and spin concentrations was examined as a nanoscale and single-molecular-based magnetic dot.