Chlorido-bridged chain complexes of dinuclear ruthenium benzoate analogues, [Ru23,4,5-(CmH2m+1O)3C6H2CO2}4Cl]n (mCl) (m = 3, 5–7, 9, 11, 13, 15, 17), were synthesised and the crystal structure of 3Cl · 2nH2O was revealed. The magnetic measurements for a series of the complexes mCl (m = 2–18) revealed that all the complexes show an antiferromagnetic interaction between the dinuclear unit, with a fastener effect giving the stronger interaction as the alkyl-chain length m increases.