Table 5. Ring Structure Related to O–H···O Bonds in Mg-cyclo-N₅^– Corresponding to Figure 4c.

type of rings		type of H2O involved	HB involved (Å)
no Mg participation	① O–H···O–H···O–H···O–H···O	two fa-H2O; two c-H2O	b′/h′	2.40
			e′/i′	1.67
Mg participation	② Mg–O–H···O–H···O···H–O–Mg	one fa-H2O; one fn-H2O; two c-H2O and one Mg	a′/f′	1.66
			d′	1.71
			g′	1.74
	③ Mg–O···H···O–Mg	one fa-H2O; two c-H2O; and one Mg	b′/h′	2.40
			c′	1.97