Geometrical structure of meta-xylylene based symmetric polyradicals and their magnetic nature: A density functional study.

Quantum chemical investigations on symmetrical polyradicals of meta -xylylene chains are done using unrestricted DFT – broken symmetry formalism, to determine whether the polymers are quasi-linear or helical, and their possible magnetic characteristics. As more radical centers are added, successively placed phenyl rings become twisted in the same direction to form a coiled chain. Each polyradical possesses a high-spin ground state with large adiabatic as well as vertical coupling constants. The adiabatic coupling constant exponentially decays with an increasing number of radical centers. Also, the Heisenberg–Dirac–Van Vleck coupling constants are generally large. The polymers are predicted to be very strong paramagnets. [ABSTRACT FROM AUTHOR]