Intrinsic Carrier Doping in Antiferromagnetically Interacted Supramolecular Copper Complexes with (Pyrazino)tetrathiafulvalene (Pyra-TTF) as the Ligand, [Cu^IICl₂(pyra-TTF)] and (Pyra-TTF)₂[Cu^I₃Cl₄(pyra-TTF)]

New supramolecular copper complexes with pyrazinotetrathiafulvalene (pyra-TTF) as the ligand, [Cu^IICl₂(pyra-TTF)] (1) and (pyra-TTF)₂[Cu^I₃Cl₄(pyra-TTF)] (2), have been synthesized by the diffusion method. Complex 1 is a black block crystal with a three-dimensional (3-D) supramolecular network; the linear chain [−Cu^IICl₂−(pyra-TTF)−]_n extends along the b axis, where the coordinated pyra-TTF donors are stacked in a head-to-tail and ring-over-bond configuration to construct two-dimensional (2-D) sheets, and between the sheets, there are C···Cl⁻ or H···Cl⁻ contacts. Even though the electron spin resonance (ESR) measurement reveals the nearly Cu^II state, complex 1 is a semiconductor with σ_RT = 1.0 × 10⁻⁴ S cm⁻¹ and E_a = 0.33 eV. The high-frequency conductivity measurement also confirmed the intrinsic slight carrier doping from Cu^II to the pyra-TTF donor. This slight doping enhances not only the real and imaginary dielectric constants but also the antiferromagnetic interaction between Cu^II spins following the 2-D Heisenberg model with 2J = −20 K. In contrast, complex 2 is a very thin black needle. This needle crystal has two crystallographically independent pyra-TTF molecules, which are coordinated and noncoordinated donors. The coordinated donors composed a supramolecular chain [Cu^I₃Cl₄(pyra-TTF)⁰]_n, whereas the noncoordinated donors formed conducting α′′-type pyra-TTF^+0.5 sheets. This complex is semiconducting with σ_RT = 0.1 S cm⁻¹ and E_a = 0.15 eV. Both complexes 1 and 2 demonstrate that the pyra-TTF molecule works not only as an oxidized donor by Cu^II to construct conducting sheets but also as a ligand coordinated to a Cu cation to form supramolecuar chains.