The binding conformations of bidentate ligand DABCO(1,4-diazobicyclo [2,2,2]octane) to a series of p/p type zinc porphyrin dimers covalently linked with flexible alkoxy chain -O(CH2)nO- (n=2～10) are described by 1H NMR and UV-vis spectroscopy. DABCO can bind inside the cavities of porphyrin dimers and form a ternary sandwich complex as the alkoxy chain length is long enough. The thermodynamic parameters which control the binding behavior are investigated.