Halogen-bonded Liquid Crystals - Halogen Bonding: Fundamentals and Applications - page 175

The structure and packing of the complex with n =8and m =3areshown
in Figs. 14 and 15, respectively ( d N ··· I = 2.746 A ;N

ˆ I-C = 176.99 ◦ ). The for-
mer shows an expected disposition of the stilbazoles and the perfluoroalkyl
entity, while the latter shows an effective segregation of the fluoroalkyl and
stilbazole segments.

···

Fig. 14 Molecular structure of the 2 : 1 complex between 4-octyloxystilbazole and 1,6-di-
iodoperfluorohexane

Fig. 15 Packing in the crystal of the 2 : 1 complex between 4-octyloxystilbazole and 1,6-
di-iodoperfluorohexane. Reproduced from [42] by kind permission of the Royal Society
of Chemistry

The complexes studied had n =8,10and12and m =2and3.Withtheex-
ception of the complex with n =10and m =3,allcomplexesshowedanematic
phase which, in all cases, was monotropic. Thus, melting points were in the
range 95 to 108 ◦ C, with clearing points between 90 and 104 ◦ C.
Another series of trimers was reported ( 15 - n , m ) that consisted of two
stilbazoles halogen bonded to a dimeric iodotetrafluorobenzene unit [43].
Examples were reported for m =2,4,6and8and n =6,8,10and12.Inchar-
acterising the halogen bonds in these complexes, XPS data were examined
and it was reported that the binding energy of the N 1 s level increased by
around 0.9 to 1.1 eV on complexation, while small hypsochromic shifts (typ-