Table 3. Geometry of the intermolecular hydrogen bonds O1H1o1N1 and O2H1o2N2 at different temperatures corresponding to the FE-I, FE-IC and FE-II phases, respectively.

Interatomic distances are given in and bond angles in degrees. (Maxmin) provides the difference between the maximum (max) and minimum (min) separation depending on the phase t of the modulation in the FE-IC phase. The mean gives the value averaged over t. Standard uncertainties are given in parentheses.

	170 K†	139K		100K‡
	Distance	Distance	Maxmin	Distance
O1H1o1	1.02(4)	1.44(2) (mean)	0.25	0.943(15) (A)
		1.32(2) (min)		1.609(15) (B)
		1.57(2) (max)		1.066(14) (C)
				1.467(14) (D)
O2H1o2	0.73(2)	0.91(2) (mean)	0.06	0.863(15) (A)
		0.88(2) (min)		0.796(15) (B)
		0.94(2) (max)		0.840(14) (C)
				0.815(13) (D)
H1o1N1i	1.66(4)	1.320(14) (mean)	0.42	1.879(15) (A)
		1.11(2) (min)		1.027(15) (B)
		1.53(2) (max)		1.700(14) (C)
				1.205(14) (D)
H1o2N2ii	2.15(2)	1.945(2) (mean)	0.05	1.908(14) (A)
		1.92(2) (min)		2.121(14) (B)
		1.97(2) (max)		1.944(14) (C)
				2.084(14) (D)
O1N1i	2.6446(16)	2.629(2) (mean)	0.07	2.6976(14) (A)
		2.586(2) (min)		2.5736(14) (B)
		2.672(2) (max)		2.5974(42) (D)
				2.6726(14) (C)
O2N2ii	2.7722(16)	2.763(2) (mean)	0.09	2.7086(15) (A)
		2.715(3) (min)		2.8251(15) (B)
		2.811(3) (max)		2.7264(15) (C)
				2.8062(15) (D)
O1H1o1N1i	159(3)	144.8(15) (mean)	9.9	143.8(11) (A)
		139.5(14) (min)		154.4(11) (B)
		149.7(16) (max)		149.3(10) (C)
				152.6(10) (D)
O2H1o2N2ii	145(2)	149.2(18) (mean)	5.4	153.7(11) (A)
		146.4(17) (min)		147.5(12) (B)
		152.0(18) (max)		154.5(11) (C)
				147.60(12) (D)

Symmetry codes for N1 and N2 in the structure model at T = 139K are: (i) ; (ii) .

^†From Gotoh et al. (2007 ▶).

^‡From Noohinejad et al. (2014 ▶); the labels A, B, C and D refer to the four molecular chains, which have become independent in the crystal structure at low temperatures.