Trihexyltetradecylphosphonium chloride

Trihexyltetradecylphosphonium
chloride ([P₆₆₆₁₄]Cl, 97.7 wt %, CAS: 258864-54-9) was
procured from IoLiTec,
and benzimidazole (98 wt %, CAS: 51-17-2) was purchased from Sigma–Aldrich.
[P₆₆₆₁₄][Benzim] was prepared using a two-step synthesis
method reported previously.^{18 (link)} The halide
content was determined to be <5 ppm by a silver nitrate test.^{31 (link)} The water content was measured to be <0.1
wt % using a Metrohm 787 KF Titrino Karl Fischer machine. The structure
and purity of the IL, after synthesis and post-absorption, were analyzed
by ¹H NMR and ¹³C NMR with a Bruker Avance II
400 MHz Ultra shield Plus and carried out as neat ILs in the presence
of a glass capillary insert containing a deuterated solvent (DMSO-d₆, purchased from Cambridge Isotope Laboratories
Inc., CAS: 2206-27-1). Gases were obtained from BOC; argon (99.998%,
CAS: 7440-37-1); carbon dioxide (99.99%, CAS: 124-38-9); nitrogen
dioxide (1% in argon, CAS: 10102-44-0).

Trihexyltetradecylphosphonium chloride (97.7
wt %, CAS: 258864-54-9) was obtained from IoLiTec; benzimidazole (98
wt %, CAS: 51-17-2) and tetrazole (CAS: 288-94-8) were purchased from
Sigma-Aldrich. [P₆₆₆₁₄][Superbase] was prepared using a
previously reported two-step synthesis method.^{27 (link)} The structure and purity of the ILs, after synthesis and
post-exposure, were analyzed using ¹H NMR and ¹³C NMR with a Bruker AVANCE II 500 MHz Ultra shield Plus spectrometer
and carried out as neat ILs in the presence of a glass capillary insert
containing DMSO-d₆, purchased from Cambridge
Isotope Laboratories Inc. (CAS: 2206-27-1). The halide content was
determined to be <5 ppm using a silver nitrate test, and water
content was measured to be <0.1 wt % using a Metrohm 787 KF Titrino
Karl Fischer machine. The following gases were obtained from BOC:
argon (99.998%, CAS: 7440-37-1), carbon dioxide (99.99%, CAS: 124-38-9),
and sulfur dioxide (1% in argon, CAS: 7446-09-5).
The IL samples
post exposure to the gases were stored in an argon-filled glovebox
before analysis. Elemental analysis was carried out using a Thermo
Scientific Flash 2000 elemental analyzer.