Semiconducting Coordination Polymers Based on the Predesigned Ternary Te-Fe-Cu Carbonyl Cluster and Conjugation-Interrupted Dipyridyl Linkers

A series of semiconducting cluster-incorporated Cu-based coordination polymers, namely, 1D zigzag polymers [{TeFe₃(CO)₉Cu₂}(L)]_n (L=1,2-bis(4-pyridyl)ethane (bpea), 1; L=1,2-bis(4-pyridyl)ethylene (bpee), 5), 2D honeycomb-like polymers [{TeFe₃(CO)₉Cu}Cu(L)_2.5]_n (L=bpea, 2; L=bpee, 6), and 2D wave-like cation–anion polymer [{Cu₂(L)₄}({TeFe₃(CO)₉Cu}₂(L))]_n (L=1,3-bis(4-pyridyl)propane (bpp), 4), as well as the macrocycle [{TeFe₃(CO)₉Cu₂}₂(bpp)₂] (3) have been quantitatively synthesized via the liquid-assisted grinding from the pre-designed cluster [TeFe₃(CO)₉Cu₂(MeCN)₂] with conjugated or conjugation-interrupted dipyridyl linkers. Notably, the most conjugation-interrupted bpp-bridged polymer 4 exhibited extraordinary semiconducting characteristics with an ultra-narrow bandgap of 1.43 eV and a DC conductivity of 1.5×10⁻² Ω⁻¹ cm⁻¹, which violates our knowledge, mainly attributed to the through-space electron transport via non-classical C−H⋅⋅⋅O(carbonyl) hydrogen bonds and aromatic C−H⋅⋅⋅π interactions. The incorporated Te-Fe-CO anions can not only provide numerous possibilities for secondary interactions within these Cu-based polymers but also serve as a redox-active coordination ligand to promote their conductivities. The intriguing structure–property relationships were studied by X-ray and DFT analyses and further demonstrated by significant change in the oxidation state of Cu atoms by XPS and Cu K-edge XANES.