Crystal structure and carrier transport properties of a new 3D mixed-valence Cu(I)-Cu(II) coordination polymer including pyrrolidine dithiocarbamate ligand

A novel mixed-valence Cu(I)-Cu(II) coordination polymer having an infinite three-dimensional (3D) structure, {[(Cu4Cu2Br4)-Cu-I-Br-II(Pyr-dtc)(4)]center dot CHCl3}(n) (1) (Pyr-dtc(-) = pyrrolidine dithiocarbamate), has been prepared and structurally characterized via X-ray diffraction. This complex consists of 1D Cu(I)-Br chains and bridging mononuclear copper(II) units of Cu-II(Pyr-dtc)(2), which form an infinite 3D network. A magnetic study indicates that this complex includes copper(II) ions exhibiting a weak antiferromagnetic interaction (theta = -0.086 K) between the unpaired electrons of the copper(II) ions present in the diamagnetic Cu(I)-Br chains. The carrier transport properties of 1 are investigated using an impedance spectroscopy technique and flash-photolysis time-resolved microwave conductivity measurement (FP-TRMC). The impedance spectroscopy reveals that this complex exhibits intriguing semiconducting properties at a small activation energy (E-a = 0.29 eV (bulk)). The sum of the mobilities of the negative and positive carriers estimated via FP-TRMC is Sigma mu similar to 0.4 cm(2) V-1 s(-1).