Five related mononuclear pentacoordinate complexes of the formula [CoL³Cl2] show slow magnetic relaxation under small applied DC field; L³ – a tridentate N-donor ligand based upon dipyrazolpyridine with an alkyl tail. All of them exhibit a supramolecular assembly, either forming dimers or chains via π–π stacking. Moreover, they display two relaxation branches, one being typical for single molecule magnets of this class, τ ∼ 10−6 s, and the second one as slow as τ ∼ 0.5 s at T = 1.9 K.