[N'-(5-Chloro-2-oxidobenzyl-κO)-2,4-dihy-droxy-benzohydrazidato-κN',O](methanol-κO)dioxidomolybdenum(VI)-4,4'-bipyridine (1/1).

In the title co-crystal, [Mo(C(14)H(9)ClN(2)O(4))O(2)(CH(3)OH)]·C(10)H(8)N(2), the deprotonated Schiff base O,N,O'-chelates to the Mo(VI) atom, the three atoms involved in chelation comprising the fac sites of the octa-hedron surrounding the methanol-coordinated metal atom. The methanol mol-ecule forms an O-H⋯N hydrogen bond to an N atom of the 4,4'-bipyridine solvent mol-ecule; the hy-droxy group of the Schiff base forms an O-H⋯N hydrogen bond to the other N atom of another mol-ecule. The two hydrogen bonds leading to the formation of a helical chain running along the b axis.