Table 2. Selected bond lengths (Å) in compounds (I)–(III).

	Compound	(I)	(II)	(III)
Ln—O bond lengths involving bpydo ligands
	Ln1—O1ii	2.5464 (11)	2.5360 (12)	2.526 (2)
	Ln1—O2	2.5192 (11)	2.5009 (12)	2.488 (2)
	Ln1—O3	2.4685 (11)	2.4558 (11)	2.451 (2)
	Ln1—O4i	2.4692 (11)	2.4554 (12)	2.448 (2)
	Average Ln—O distances	2.501	2.487	2.478
Ln—O bond lengths involving chelating nitrate anions
	Ln1—O5	2.5929 (13)	2.5750 (13)	2.555 (2)
	Ln1—O6	2.6573 (13)	2.6443 (14)	2.640 (2)
	Ln1—O8	2.6004 (12)	2.5832 (13)	2.573 (2)
	Ln1—O9	2.6428 (12)	2.6242 (13)	2.615 (2)
	Ln1—O11	2.6231 (12)	2.6036 (12)	2.585 (2)
	Ln1—O12	2.6333 (11)	2.6147 (12)	2.597 (2)
	Average Ln—O distances	2.625	2.608	2.594

Symmetry codes: (i) x − , −y + , z − ; (ii) x, y − 1, z.