Spin-peierls transition in dimerized stacks of anion-radical salt (N-Me-2,5-di-Me-Pz)(TCNQ)2, (Pz is pyrazine)

An anion-radical salt (ARS) (N-Me-2,5-di-Me-Pz)(TCNQ)2, where Pz is pyrazine, was synthesized and its crystal structure was resolved. X-ray diffraction experiments on single crystals were performed. Heat capacity was measured in the temperature range from 2 to 300K. Magnetisation and magnetic susceptibility were measured in the temperature range from 2 to 300K and the low-temperature part was measured in magnetic fields from 5mT to 5T. The experimental results were explained in terms of dimerized Heisenberg spin 12 chain model. Numerical calculations were performed and compared with experimental data.