Influence of the linker length on the host–guest properties of alkoxy- and polypyridine-bridged molecular rectangles of formulae {[Re(CO)3(OC5H11)]4(L)2}, with L = 4-pyridinealdazine and 4,4′-azobis(pyridine)

A new series of alkoxy- and polypyridine-bridged rhenium molecular rectangles of formulae {[Re(CO)3(OC5H11)]4(L)2}, with OC5H11 = 1-pentoxy, L = PCA (4-pyridinecarboxaldehyde azine) and 4,4′-azpy (4,4′-azobis(pyridine)), were synthesized and characterized by spectroscopic and diffraction techniques. Quenching of fluorescence of aromatic hydrocarbons by these complexes was studied by stationary and dynamic techniques. The quenching mechanism proved to be predominantly static and the Stern–Volmer constants indicated a decrease of the extent of C–H⋯π interactions with decreasing length of the linkers that form the molecular rectangles.