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Updated: Sep 29, 2025

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Preparation and Characterization of the Halogen-Bonding Motif in the Isolated Cl-·IOH Complex with Cryogenic Ion
Santino J Stropoli1, Thien Khuu1, Joseph P Messinger1
1Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
Abstract:
In the presence of a halide ion, hypohalous acids can adopt two binding motifs upon formation of the ion-molecule complexes [XHOY]- (X, Y = Cl, Br, I): a hydrogen (HB) bond to the acid OH group and a halogen (XB) bond between the anion and the acid halogen. Here we isolate the X-bonded Cl-·IOH ion-molecule complex by collisions of I-·(H2O) clusters with HOCl vapor and measure its vibrational spectrum by IR photodissociation of the H2-tagged complex. Anharmonic analysis of its vibrational band pattern reveals that formation of the XB complex results in dramatic lowering of the HOI bending fundamental frequency and elongation of the O-I bond (by 168 cm-1 and 0.13 Å, respectively, relative to isolated HOI). The frequency of the O-I stretch (estimated 436 cm-1) is also encoded in the spectrum by the weak v = 0 → 2 overtone transition at 872 cm-1.
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