p-Diethynylbenzene-based molecular wires, Fe–Ctriple bond; length of mdashC-p-C6H2X2–Ctriple bond; length of mdashC–Fe [Fe = Fe(η5-C5Me5)(dppe)]: Synthesis, substituent effects and unexpected formation of benzodifuran complex

A series of p-diethynylbenzene-based molecular wires, Fe–Ctriple bond; length of mdashC-p-C6H2X2–Ctriple bond; length of mdashC–Fe (3) (Fe = FeCp∗(dppe)), is prepared and their wire-like performance is estimated on the basis of the KC and Vab values. It has been revealed that electron-donating substituents (X) improve the performance. The benzodifuran complex 4 unexpectedly formed from the derivative with X = OH shows the performance comparable to 3.