Reversible geometry reorganisations are demonstrated by cis-3,5-diamino-trans-hydroxycyclohexane (cis,trans-DAHC) copper(ii) fluoride complexes, with the concentration of water in the mother liquor controlling interconversion between blue crystals of 5-coordinate syn-[Cu(DAHC)(2)F](F).2CH(3)OH.H(2)O and red crystals of 4-coordinate anti-[Cu(DAHC)(2)](F)(2).2H(2)O.