Crystal structure and magnetic properties of piperazinium hexadichlorocuprate: A new S=(1/2) antiferromagnetic chain with alternating exchange

The crystal structure of piperazinium hexadichlorocuprate (PHCC) has been determined. In this compound, the Cu(II) ions are arranged in zig-zag chains well separated from each other. As temperature is decreased from the ambient temperature, the magnetic susceptibility exhibits a maximum at T=15 K and then tends to zero. This behavior is in good agreement with the theoretical predictions for an S=1/2 alternating antiferromagnetic chain with J1/k=-12.5 K and an alternation parameter close to 0.6. An orbital interpretation of this behavior is given. © 1986 The American Physical Society.