Structure and stability of complexes of macrocyclic ligands bearing2-hydroxycyclohexyl groups. Structure of thecopper(II) complex of1-(2-hydroxycyclohexyl)-1,4,7,10-tetraazacyclododecane and thestrontium(II) complex of7,16-bis(2-hydroxycyclohexyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane