Persistent high-spin polycarbene (S=3) as studied by 2D-ESTN spectroscopy

Persistent high-spin polycarbene, 1,3,5-tris(ethynyldiphenylmethylene)benzene was studied by Electron Spin Transient Nutation (ESTN) spectroscopy in non-oriented media, 2D-ESTN spectra of the polycarbene were measured in order to identify a molecular spin multiplicity of the high-spin state. The observed nutation frequencies were assigned to those arising from the allowed ESR transitions of the septet ground state (S=3). It indicates that the high-spin state is generated by ferromagnetic interaction between stable bromo-substituted diphenylmethylenes(S=l) through a 2D topological spin coupling unit with C3 symmetry, 1,3,5-tris(ethynyl)benzene. The high-spin polycarbene has survived after annealing of the glass matrix. The stable triplet carbene unit is supposed to serve as a useful building block for extended super high-spin molecular systems and organic superparamagnets