Study of small oligomers based on Ru2(DMBA)4 and meta-phenylene diethynylene

The reactions between Ru2 (DMBA)4(NO3)2 (DMBA = N,N’-dimethylbenzamidinate) and meta-phenylene diethynylenes bearing 5-ester substituents (-CO2iPr, L1; -CO2Bn, L2) in the presence of Et2NH afforded a series of oligomeric compounds with meta-phenylene diethynylene bridge, namely L-[Ru2 (DMBA)4L]m with m as integers. With L1, the compounds with m = 1–3 (1a, 2a and 3a) were separated and fully characterized. With L2, only the compound with m = 1 (1b) was successfully isolated. In addition to routine spectroscopic characterizations, the structures of both compounds 1b and 2a were determined using single crystal X-ray diffraction. For the series of 1a, 2a and 3a, both the voltammetric and absorption spectroscopic characteristics bear close resemblance to those of simple Ru2 (DMBA)4(C2R)2 compounds, indicating the absence of significant inter-unit electronic couplings in the oligomers.