Probing magnetic interactions in columnar phases of a paramagnetic gold dithiolene complex

Abstract

A novel radical gold dithiolene complex exhibits a hexagonal columnar mesophase, as confirmed by optical microscopy, DSC analysis and X-ray diffraction. The extent of delocalization of the spin density in such a complex was analyzed by EPR. Temperature dependent magnetization measurements reveal that the global magnetic moment is remarkably affected at the liquid-crystalline phase transition with a marked hysteresis signature, rare behavior among the few described paramagnetic discotic phases. In addition, these molecules were found to strongly aggregate in solution into one-dimensional fibers with a mean diameter of 60 nm extending over micrometres, leading to the formation of gel-like structures. These fibers are stable and can be isolated on surfaces. The gelation of the system can also be detected by temperature-dependent magnetic measurements.