TABLE 3.

Contact distances (Å), the corresponding bond valences, and bond valence sum (BVS) for KDFTFSI and KTFSI.

Compound	Contact atoms	Contact distance (Å)	Bond valence a
KDFTFSI	K1···O	2.746	0.19
	K1···O	2.748	0.19
	K1···O	2.783	0.17
	K1···O	2.840	0.15
	K1···O	2.961	0.11
	K1···O	3.091	0.07
	K1···O	3.192	0.06
	K1···O	3.338	0.04
	K1···N	3.295	0.06
	K1···N	3.365	0.05
			BVS 1.09
	K2···O	2.687	0.22
	K2···O	2.713	0.21
	K2···O	2.727	0.20
	K2···O	2.733	0.20
	K2···O	2.758	0.18
	K2···O	2.791	0.17
	K2···O	2.802	0.16
	K2···O	2.906	0.12
			BVS 1.47
KTFSI b	K1···O	2.697	0.22
	K1···O	2.724	0.20
	K1···O	2.726	0.20
	K1···O	2.742	0.19
	K1···O	2.791	0.17
	K1···O	2.848	0.14
	K1···O	2.882	0.13
	K1···O	2.996	0.10
			BVS 1.35
	K2···O	2.800	0.16
	K2···O	2.873	0.13
	K2···O	2.895	0.13
	K2···O	2.959	0.11
	K2···O	3.113	0.07
	K2···O	3.114	0.07
	K2···O	3.204	0.06
	K2···O	3.343	0.04
	K2···N	3.405	0.05
	K2···N	3.413	0.04
			BVS 0.86

^a Bond valence was calculated by Eq. 1 where R₀ (Å) = 2.132 for K···O, and 2.26 for K···N, B = 0.37, and R (Å) corresponds to the experimental contact distance (Brown and Altermatt, 1985).

^b The crystallographic data were taken from Xue et al. (2002); Matsumoto et al. (2015).