Synthesis of N-cyanoalkyl-functionalized imidazolium nitrate and dicyanamide ionic liquids with a comparison of their thermal properties for energetic applications

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PAPER

Synthesis of N-cyanoalkyl-functionalized imidazolium nitrate and

dicyanamide ionic liquids with a comparison of their thermal properties

for energetic applicationsw

David M. Drab,^aMarcin Smiglak,^aJulia L. Shamshina,^aSteven P. Kelley,^a

Stefan Schneider,^bTommy W. Hawkins^band Robin D. Rogers*^a

Received (in Gainesville, FL, USA) 10th November 2010, Accepted 20th April 2011

DOI: 10.1039/c0nj00889c

The synthesis of 10 N-alkyl-N-cyanoalkyl-functionalized imidazolium (N-methyl- and N-butyl-N-

((CH₂)_nCN)imidazolium; n = 1–4) nitrate and 11 N-alkyl-N-cyanoalkyl-functionalized

imidazolium (N-methyl-N-((CH₂)_nCN)imidazolium; n = 1–6, N-(2-cyanoethyl)-N-

((CH₂)_nCN)imidazolium; n = 1,3–6) dicyanamide salts was achieved via N-alkylation of

substituted imidazoles with commercially available haloalkylnitriles followed by anion exchange.

Based on their observed melting points, all dicyanamide salts and all but one nitrate salt

(1-cyanomethyl-3-methylimidazolium nitrate) had melting points o100 1C, as did 13 of the

17 halide precursors also reported here. Diﬀerential scanning calorimetry data indicated that

melting points decreased by increasing the N-alkyl or N-cyanoalkyl chain length or by exchanging

with the dicyanamide anion, which produced the lowest melting points in comparison to

analogous halide or nitrate salts. Thermogravimetric analyses indicated that thermal stability

increased for longer N-cyanoalkyl substituent lengths and decreased signiﬁcantly for nitrates and

more so for dicyanamides bearing short-chain N-cyanoalkyl substituents (e.g., N-cyanomethyl,

N-(1-cyanoethyl), and N-(2-cyanoethyl)) in comparison to halide precursors. Furthermore, for

many of the N-cyanoalkyl-substituted salts (especially the dicyanamides), there was a signiﬁcant

production of thermally-stable char – presumably due to by-products formed from the reaction of

either N-cyanoalkyl substituents, dicyanamide anion, or both, which resulted in thermally-stable

polymers or cycles.

their physical and chemical properties can be carefully tuned

Introduction

via the choice of the component ions to target speciﬁc

There exists a high demand for the development of new

performance properties.

and improved energetic materials (EMs) for application as

As a result of the initial interest of the Air Force in energetic

propellants, fuels, and explosives, as traditional EMs face

ionic liquids (EILs), intense research eﬀorts have been made in this

direction.^5–7Promising results have appeared in the preparation of

problems related to environmental and safety concerns during

stages of synthesis, transport, and storage.¹The U. S. Air

EILs with speciﬁc properties of interest to the Air Force – for

example, high density,^8–11high heats of formation,^12–14optimal

Force, in particular, is interested in potential replacements of

oxygen balance,^15–18and hypergolicity.^19–23However, there are

traditional energetic materials, and has recognized that ionic

liquids (ILs, salts which have melting points o100 1C)²are

not many strategies available to access these properties in a

valuable materials in energetic applications.^3,4ILs often

predictable manner.

possess broad liquid ranges, negligible vapor pressures, high

Work in our group has been focused not on the synthesis of

heats of formation, are thermally stable, and have signiﬁcantly

EMs per se but, rather, on the understanding of IL chemistry

reduced sensitivity and toxicity characteristics. Additionally,

at a deeper level. It has long been an interest to identify IL

structural patterns with the goal of accessing targeted properties

^aDepartment of Chemistry and Center for Green Manufacturing,

The University of Alabama, Tuscaloosa, AL 35487, USA.

in a systematic and predictable fashion. Previously, we have

synthesized azole-based ILs with energetic substituents (e.g.,

nitro-, amino-, cyano- groups) to identify the eﬀect of azole

type and ring substituents on thermal properties of resultant

ILs.^24–26In another study, we established a strategy to

incorporate energetic functional groups into either cation or

E-mail: rdrogers@as.ua.edu

^bAir Force Research Laboratory, 10 East Saturn Boulevard,

Building 8451, Edwards Air Force Base CA, USA.

E-mail: Tommy.Hawkins@edwards.af.mil

w CCDC reference numbers 801102–801105. For crystallographic data

in CIF or other electronic format see DOI: 10.1039/c0nj00889c

c

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anion, with the consequence that electron-withdrawing nitro-

and cyano- groups were observed to deactivate azoles toward

formation of cations.^{13,19,27–29}

focus of the work was to investigate how the properties of the

nitrate and dicyanamide salts are aﬀected by changing the

N-cyanoalkyl substituent, the uniformity of the halide anion in

the synthesis of 4-20[X] was not considered essential and was

established by the availability of commercial haloalkylnitriles.

Minor changes were implemented in the published reactions.

The syntheses of 4[Cl], 11[Cl], and 16[Cl] were conducted at

room temperature to avoid the thermal degradation of the

substrates. In addition, 8[Br], 9[Br], and 17-20[X] were all

prepared using ethyl acetate as solvent to allow for easy

product phase separation from the solvent layer. Upon washing

4-20[X] with ethyl acetate or acetone, and subsequent removal

of residual solvent under high vacuum overnight, the halide

salts were obtained in fair to excellent yields (82–97%)

with the exception of 11[Cl] (yield = 57%) and 14[Cl]

(yield = 45%, as a result of inadvertent loss of sample when

removing residual starting materials).

Continuing the above eﬀorts, in this paper, we report

systematic studies of thermal properties for two series of

N-cyanoalkyl-functionalized imidazolium salts. Although there

have been reported examples of N-cyanoalkyl-functionalized

imidazolium halides,^30,31nitrates,³²and dicyanamides,^29,31,33

to the best of our knowledge these classes have not been

examined systematically or comparatively with respect to

homologous changes in structure.

Three types of systematic modiﬁcations to N-cyanoalkyl-

functionalized imidazoliums have been made here. First, we

believed that the length and branching of the alkyl chains in

the N-cyanoalkyl-functionalized imidazolium cation would

inﬂuence the liquid state, as others have reported melting

point reduction as alkyl length increases.³⁴We also hypothe-

sized that the melting points of N-cyanoalkyl-functionalized

imidazolium salts would be higher when compared with

1,3-dialkylimidazolium analogs, due to possible intra- and

intermolecular organization from the p-electron system and

lone pair electrons available in the cyano group.²⁶

Many of the intermediate halide salts have been synthesized

previously including, 4[Cl],^30,425[Br],⁴³6[Cl],³⁰7[Cl],³⁰

12[Br],⁴⁴and 16[Cl].³⁸Since these compounds were typically

only used as intermediates in further IL synthesis, important

data such as melting points, glass transition temperatures,

thermal stability, and synthetic yields were frequently not

reported. Here, we report all of the thermal properties and

yields for these intermediates and, where possible, compare

them with the literature. To the best of our knowledge,

the nitrate (4–7, 10-15[NO₃]) and dicyanamide (4, 5, 7–9,

16-20[N(CN)₂]) salts were not previously reported, with the

exception of 6[N(CN)₂].³¹

Secondly, for the same reason, we varied the N-alkyl

substituent on the imidazole ring to probe for trends similar

to those reported in the literature, where melting points

typically decrease and thermal stabilities remain largely

unaﬀected from N-methyl to N-butyl substitution.^34,35Lastly,

we investigated the eﬀect of diﬀerent energetic anions—nitrate

and dicyanamide. Nitrate was chosen because of the oxidizing

nature of the [NO₃]^Àanion, which facilitates thermal decom-

position of the salt.³⁶In turn, dicyanamide anions were

expected to decrease melting points and increase thermal

stability when compared to halide analogs.³⁷In addition, the

nitrate and dicyanamide anions were selected for their reputed

IL-forming abilities and physicochemical properties suitable

for EILs. These nitrile-functionalized salts are also excellent

precursors to novel mixed heterocyclic species, as we have

recently illustrated.³⁸

Nitrate salts 4–7, 10-15[NO₃] were prepared from the halide

precursors using the strongly basic anion exchange resin

BioRad AG 1-X8 (100–200 mesh with 8% divinylbenzene

copolymer cross-linkage). The resin has an exchange capacity

of 2.6 meq/g dry resin and an appropriate amount of resin was

prepared to exchange 3.2 to 6.4 mmol of halide precursor. The

commercially available chloride resin was converted to

(NO₃)^À-form following the manufacturer’s protocol,^45,46

where the resin was loaded into a column (1 cm diameter Â

10 cm tall) and washed with 5 bed volumes of 0.5 N sodium

nitrate solution. To check for the completeness of the nitrate

exchange, the presence of halide in the eluted solution was spot

checked frequently with a 1.0 M silver nitrate solution. When

no halide was indicated as evident by the lack of white, cloudy

precipitate, ﬁnal conditioning of the nitrate-exchanged resin

column was completed by washing with 2 bed volumes of

deionized water.

With the (NO₃^À)-form of the resin in hand, halide samples

were dissolved in 100 mL of deionized water and eluted

through the column followed by an additional 2 bed volumes

of deionized water in the ﬁnal rinse. For both nitrate loading

and sample elution, the linear ﬂow rate was maintained at

approximately 2 cm min^À1through the bed volume. Each of

the eluted fractions was qualitatively screened for the presence

of halide by spot-testing each eluted fraction with 1.0 M silver

nitrate solution. Once separated, the ‘halide-free’ fractions

were then puriﬁed by removal of water from the nitrate salts

using an air stream followed by ﬁnal drying under high

vacuum for 24 h. The ﬁnal 10 products 4–7, 10-15[NO₃] were

obtained in fair to excellent yields (76–95%).

Synthesis

The starting halide salts were obtained by alkylating commercially

available methyl-, butyl-, or 2-cyanoethyl-substituted imidazole

(Scheme 1: 1, 2, 3, respectively)³⁹with haloalkylnitriles via a

classical quaternization reaction. Given the wide variety of

commercially available haloalkylnitriles, this was considered a

logical starting point for the synthesis of imidazolium salts

with variable N-cyanoalkyl side-chain lengths as described

here.⁴⁰The N-cyanoalkyl-functionalized imidazolium nitrate

(4–7, 10-15[NO₃]), and dicyanamide (4–9, 16-20[N(CN)₂]) salts

were prepared by metathesis of the analogous halides

(4-20[X]), either by using an ion exchange resin (nitrate salts)

or a silver salt (dicyanamide salts).

The 17 N-cyanoalkyl-functionalized imidazolium halide

salts (4-20[X]) were synthesized according to literature

protocols,^41,42where 1-alkylimidazole starting materials

(1–3) were alkylated with haloalkylnitriles generally under

solvent-free conditions at 70 1C for 48 h in a sealed,

high-pressure vial (except as noted below). Since the main

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Scheme 1 Synthesized N-cyanoalkyl-functionalized imidazolium halide (4-20[X]), nitrate (4–7, 10-15[NO₃]), and dicyanamide (4–9, 16-20[N(CN)₂])

salts.

The dicyanamide salts 4–9, 16-20[N(CN)₂] were obtained by

metathesis using silver dicyanamide (prior attempts to obtain

dicyanamide salts using sodium dicyanamide by literature

protocols failed to achieve satisfactory yields⁴⁷) which was

prepared by methods reported in the literature.^19,33Each of

the halide precursors (4–9, 16-20[X]) was combined with a

10% excess of AgN(CN)₂in deionized water and heated at

50 1C for 1 h. At the end of the metathesis reaction, the silver

halide by-product was ﬁltered, and subsequent evaporation of

water from the ﬁltrate using an air stream resulted in the 11

dicyanamide salts in fair to good yields (75–92%). One of

these compounds, 6[N(CN)₂], has been previously reported,³¹

and the published data is discussed below in the comparison of

all compounds.

salt 4[N(CN)₂]. Single crystals were obtained by recrystallization

from methanol solutions with slow-vapor diﬀusion using

diethyl ether. The crystallographic details can be found in

the Electronic Supplementary Information (ESI).w

The asymmetric units for each of the solved structures are

shown in Fig. 1, where each structure is oriented perpendicular

with respect to the plane of the imidazolium ring. The bond

lengths and angles are all typical for the imidazolium ring,

although the bonds involving C2 in 4[N(CN)₂] (Fig. 1D) are

signiﬁcantly shorter than the others, and there is variability of

the C–CN bond among the structures. All imidazolium rings

are fairly planar, although 10[Br] (Fig. 1B) has the least

planar ring.

The overall packing in 5[Br] is salt-like (Fig. 1A), but the

nitrile groups do not participate in short contacts. Crystal

structures of 1-(2-cyanoethyl)-3-methylimidazolium salts

have not yet been reported in the literature, but in three

similar salts, the nitrile groups participate in a variety of close

contacts with the cation such as parallel ‘stacking’ with the

imidazolium ring,³⁰contacts with other parallel nitrile

groups, and contacts to hydrogen atoms on the cation.⁵⁴

Nitrile-imidazolium short contacts are observed in the other

3 structures reported here (Fig. 1B, C and D), and together

these observations imply that it is unusual that the nitrile

groups in 5[Br] do not participate in short contacts. The

cations do interact via edge-to-edge p–p stacking between

the C4 and C5 positions (C4Á Á ÁC5 = 3.413(2) A). The

anions interact through hydrogen bonds to hydrogen atoms

at the C2 and C4 positions, but do not appear to reside in

the coloumbically favorable positions above and below the

imidazolium ring.¹⁹

To check purity at each stage of the synthesis, ¹H NMR

analysis conﬁrmed the structure of all cations (4–20) and

served as a check for the presence of organic starting materials

in 4–7, 10-15[NO₃] and 4–9, 16-20[N(CN)₂], which were found

to be below detection limits (o1 mol%).⁴⁸FT-IR spectro-

scopy was used to identify the characteristic intense absorption

band for the free nitrate anion (n_max(N–O) = 1350–1360 cm^{À1 49}

)

in 4–7, 10-15[NO₃], as well as those observed for the dicyanamide

anion (n_max(CRN) region around 2250 (m), 2220 (m), and

2150 (s) cm^À1).⁵⁰Spot-testing the eluted nitrate salt fractions

with silver nitrate solution served to qualitatively conﬁrm the

absence of halide in the ﬁnal product with the complete anion

exchange of halide for nitrate (o100 ppm).⁵¹Determination

of halide impurity in the dicyanamide samples was attempted

following a literature method^52,53that used silver nitrate

titration in the presence of a potassium chromate indicator,

however, this did not conclusively indicate halide in the

samples obtained.

10[Br] also shows salt-like packing with alternating anion

and cation layers. There are short contacts between cations

involving the nitrile group and hydrogen atoms, as well as

pi-stacked cation dimers with C4 on one ring approaching C5

on another at a distance of 3.559(3) A, with the rings parallel.

The anions participate in three diﬀerent interactions with

Single crystal structures by X-ray diﬀraction

Crystallographic analyses were performed on the halide salts

5[Br] and 10[Br], the nitrate salt 4[NO₃], and the dicyanamide

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Fig. 1 ORTEP illustrations (50% probability ellipsoids) of the formula units (illustrating the closest cation–anion approach) and packing

diagrams for 5[Br] down c (A), 10[Br] down a (B), 4[NO₃] down a (C) , and 4[N(CN)₂] down a (D). Crystallographic axes are color-coded: a is red,

b is green, and c is blue.

cations: a hydrogen bond to the hydrogen at the C2 position, a

hydrogen bond to a hydrogen atom at the C5 position, and an

out-of-plane interaction with the C2 carbon atom from one

side of the ring.

hydrogen bonds: a very short, bifurcated contact between the

oxygen atoms and the hydrogen atom on C2, a bifurcated

hydrogen bond to the hydrogen atom at C5, and short

contacts to the methylene hydrogen atoms and C7. There is

also an out-of-plane interaction between the anion and C2.

4[N(CN)₂] also shows eﬃcient salt-like packing with

separate anion and cation layers. This structure has only one

cation–cation short contact, which is between the nitrile group

and the methylene hydrogen atoms. The anion exhibits several

types of interactions, with each atom participating diﬀerently.

One of the terminal nitrogen atoms, N14, makes a hydrogen

bond to H2A on one cation, a short contact to the methyl

4[NO₃] has two symmetry-independent formula units,

however, the environment and packing is the same for both

of them. Packing seems to be dominated by cation–anion

interactions with the side-chains oriented to maximize hydrogen

bonding to the nitrile group, where all anions and imidazolium

rings are roughly parallel. Cation-cation short contacts occur

between the hydrogen atom at C4 and nitrile groups on two

cations (a bifurcated contact). The anion makes three in-plane

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group on a second cation, and is situated above the C2

position of a third cation. N10 makes a hydrogen bond to a

ring hydrogen atom at C5. C11 makes short contacts to a

methyl group on one cation and C2 on another cation. The

carbon atoms in the dicyanamide anion behave as hydrogen

bond acceptors as was reported for other related crystal

structures.^19,50,55

Diﬀerential scanning calorimetry

The observed thermal behavior of the N-cyanoalkyl-functionalized

salts was often complex, and phase transitions were classiﬁed

according to one of four diﬀerent observations. Fig. 2

compares the ﬁrst and second heating cycles were for

representative compounds 16[N(CN)₂], Class I; 6[Cl], Class II;

12[Br], Class III; and 4[NO₃], Class IV.

The most common trend in the DSC data (Fig. 2, Class I)

featured a reversible glass transition followed by an additional

liquid–liquid transition during the second and third consecutive

heating cycles. Compounds of this type include 7[Cl], 8[Br],

9[Br], 11[Cl], 13[Cl], 14[Cl], 15[Br], 17[Cl], 18[Cl], 19[Br],

20[Br]; 6, 7, 11-15[NO₃]; and 5–9, 16-20[N(CN)₂]. Structural

features common to this class include the N-butyl-substituted

nitrate salts, most of the dicyanamide ILs (Class II 4[N(CN)₂]

is an exception), and the halide salts featuring longer

N-cyanoalkyl functional groups.

Thermal and sensitivity investigations

Most of the 41 compounds synthesized and reported here are

ILs by deﬁnition (i.e., mp o100 1C), with the exception of

4[Cl], 5[Br], 6[Cl], 4[NO₃], 5[NO₃], and 4[N(CN)₂] which are all

crystalline solids. Phase transition temperatures were obtained

by DSC (Table 1) and include crystallization and melting

transition temperatures (T_crystand T_m, respectively), as well

as glass and liquid–liquid transition temperatures (T_gand T_lÀl

,

Those compounds in Class II did not show melting on

the ﬁrst heating cycle but, rather, featured a reversible,

low-temperature glass transition, crystallization on heating

from a super-cooled phase, and a subsequent melting transition.

This class of thermal behavior was observed for compounds

4[Cl], 6[Cl], 10[Br], 5[NO₃], 10[NO₃], and 4[N(CN)₂] (Fig. 2,

Class II), which featured short N-cyanoalkyl chain lengths

(e.g., N-cyanomethyl, N-(1-cyanoethyl), and N-(2-cyanoethyl)),

with the exception of 6[Cl] that was functionalized with the

N-(3-cyanopropyl) group.

respectively). T_gand T_lÀlwere determined from the second

heating cycle after initially heating the material from ambient

temperature to an upper limit based upon the thermal stability

of the compound as determined by TGA. Phase transitions

determined after the ﬁrst heating cycle were considered to be

generally more accurate, where there is evidence for improved

surface contact between the sample and the DSC sample pan

in subsequent heating cycles.⁵⁶

We have observed liquid–liquid transitions for ILs fairly

often, particularly in our work with pharmaceutical ionic

liquids.⁵⁷The recent work of Tanaka et al.^58,59suggests our

observed results are indicative of diﬀering liquid states and

that such transitions are expected to be common for ionic

liquids.

There were also a few examples for which the thermal

behavior diﬀered signiﬁcantly from the above. For example,

in three cases melting occurred in the ﬁrst heating cycle but

only a reversible glass transition prior to a liquid–liquid

transition was observed for the next consecutive heating

cycles. This small class of compounds consists of all halide

salts featuring the N-(2-cyanoethyl) functional group (Fig. 2,

Class III, compounds 5[Br] 12[Br], and 16[Cl]).

Crystallization was taken as the onset for an exothermic

peak in the second heating cycle (with the exception of 4[NO₃],

which showed T_cryst= 43 1C as an exothermic peak during

each cooling cycle) and these are typical for transformations of

super-cooled liquids to crystalline solids.⁶⁰T_mvalues were

measured from the onset of a sharp, endothermic peak on

heating, and T_gvalues were identiﬁed from the onset of

small shifts in heat ﬂow arising from the transition between

amorphous glassy to liquid states when heating.

Finally, in a single case melting was observed for each

heating cycle, as well as crystallization for each cooling cycle

(Fig. 2, Class IV, 4[NO₃]). For this compound, there was

no glass transition observed. The melting point for 4[NO₃]

(T_m= 103 1C) was the highest observed for all nitrates and

dicyanamide salts, presumably from the more eﬃcient packing

of the smallest cation (4) of the nitrate salt. However, several

halides with short N-cyanoalkyl groups were observed to have

signiﬁcantly higher melting points (T_m= 174 1C, 4[Cl];

143 1C, 5[Br]; 131 1C, 10[Br], 120 1C, 16[Cl]), which results

from the small size of both cation and anion.

The thermal stabilities (by TGA) for all prepared

compounds are presented in Table 1 as the onset of thermal

decomposition for the ﬁrst 5% weight loss (T_5%onset). The

value for T_5%onsetwas considered a more accurate assessment

of thermal stability than the onset of thermal decomposition

(T_onset, included for comparison in parentheses in Table 1) that

is more commonly reported in the literature.⁶¹All compounds

were heated to 600 1C at a rate of 5 1C min^À1with an

isothermal hold at 75 1C for 30 min.

Sensitivity testing for all dicyanamide salts 4–9, 16-20[N(CN)₂]

was conducted using an Olin-Mathieson drop weight tester,

and the values obtained are reported in the last column

of Table 1. In addition, the same compounds were tested

for sensitivity to friction using a Julius Peters apparatus, as

well as sensitivity to electrostatic discharge (ESD) using an Air

Force Research Laboratory ESD test apparatus with initial

sample test level at 5000 V with capacitance set to deliver

0.25 J.

Class I compounds did not exhibit well-deﬁned melting

temperatures, which is consistent with the suggestion that

the relatively high viscosity of ILs (compared to molecular

liquids) can inhibit crystallization during the timeframe of the

DSC experiment.⁶²Our group has observed similar thermal

behavior previously for a series of protonated ILs,⁶³and it was

proposed that the varying degree of inclination in the onset of

the T_lÀlsignal might indicate variation of crystallization

attempts for the ILs. Fig. 3 compares the second heating

cycles for four of the Class I compounds, where the variation

in slope of the T_lÀlonset varies signiﬁcantly in both the

exothermic rise as well as the endothermic trough.

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Table 1 Thermal and sensitivity characterization of halide, nitrate, and dicyanamide salts with cations 4–20

[X]^À

[NO₃]^À

[N(CN)₂]^À

T_g

(T_lÀl

T_m

(T_cryst

T_g

(T_lÀl

T_m

(T_cryst

T_g

(T_lÀl

T_m

(T_cryst

(1C)

)

T_5%onset

)

T_5%onset

(T_onset) (1C) (1C)

)

T_5%onset

Impact

[X] (1C)^a(1C)^a

(T_onset) (1C)^b(1C) (1C)

(T_onset) (1C) (kg cm)^c

Cation

Cation# R₂CN

4

CH₂CN

Cl^À36

174

206

—

103

(43)

183

(195)

À60

67

(12)

210

(234)

4200

Lit.

(251)

(Lit.

221³⁸

205

(241)

258

170³⁴

(114)

143

)

5

6

(CH₂)₂CN

(CH₂)₃CN

Br^ÀÀ21

À47 62

(1.9)

166

À67

12

161

(173)

244

(260)

(Lit. T_d

= 278³¹

)

172

170

(198)

223

(270)

Cl^ÀÀ35

96

À56

—

À80

—

Lit.

Lit. 90³⁰(290)

(38)

Lit.

À34³⁰(21)

(Lit. T_d

= 255³⁰

À72³¹

(Lit.

)

(50)

26³⁰

)

7

(CH₂)₄CN

Cl^ÀÀ51

Lit. 32³⁰224

(262)

À56

—

266

(294)

À74

—

247

(273)

170

(45)

(52)

(47)

8

(CH₂)₅CN

(CH₂)₆CN

Br^ÀÀ44

(50)

—

248

(284)

257

(280)

219

(254)

n.s.

168

À78

(59)

À77

(46)

n.s.

—

264

(287)

266

(289)

n.s.

170

n.s.

9

Br^ÀÀ48

—

(49)

10

CH(CH₃)CN Br^ÀÀ3.1

131

(76)

À58 42

n.s.

(À9.7) (209)

11

12

13

14

15

CH₂CN

Cl^ÀÀ22

(114)

—

86

—

186

(213)

227

(259)

243

(279)

240

(278)

211

(246)

À43

(46)

À52

(63)

À59

(48)

À59

(42)

À50

(50)

—

168

(179)

180

(202)

258

(292)

263

(291)

157

(214)

n.s.

(CH₂)₂CN

(CH₂)₃CN

(CH₂)₄CN

Br^ÀÀ31

(52)

Cl^ÀÀ36

(40)

Cl^ÀÀ39

(50)

CH(CH₃)CN Br^ÀÀ12

(132)

16

17

18

19

20

CH₂CN

Cl^À0.26

(49)

120

—

196

(222)

196

(210)

190

(221)

202

(241)

161

(221)

n.s.

À43

(50)

À62

(72)

À61

(51)

À66

(53)

À66

(58)

—

148

(162)

164

(182)

170

(178)

165

(192)

157

(192)

176

174

170

(CH₂)₃CN

(CH₂)₄CN

(CH₂)₅CN

(CH₂)₆CN

Cl^ÀÀ27

(95)

Cl^ÀÀ36

(51)

Br^ÀÀ42

(52)

Br^ÀÀ42

(58)

a

Melting point (T_m) and/or glass transition temperatures (T_g) were measured from the onset of transition and determined by DSC from the second

heating cycle at a ramp rate of 5 1C min^À1after initially melting then cooling the samples to À100 1C, unless otherwise indicated. Salts meeting the

b

deﬁnition of ionic liquids (mp o100 1C) are in bold. Reported decomposition temperatures were obtained by TGA, heating at 5 1C min^À1under

dried air atmosphere and are reported as (i) onset to 5 weight% loss of mass (T_5%onset) and (ii) onset to total mass loss (T_onset

c

)

(in parentheses). Impact sensitivity analysis was carried out on an Olin-Mathieson drop weight tester where a small sample (20 mg) was placed

in a standard sample cup (liquid or solid cell employed as appropriate), and a multi-kilogram mass was dropped vertically from measured heights

d

upon the closed sample. n.s. = not synthesized.

For the example 5[N(CN)₂] (Fig. 3A), the observed sharp

exothermic increase might signify the start of crystallization.

However, the plateau of the signal maxima and broad endo-

thermic trough are not characteristic of typical crystallization/

melt curves as found, for example, in Class II compounds. The

other compounds shown in Fig. 3 also indicated increasingly

glass-like transitions from a super-cooled phase (compare

Fig. 3B–C), where changing heat ﬂow both in the onset and

oﬀset of the signal diﬀered from the characteristic shift of glass

transitions. Further DSC study of these materials at slower

DSC scan rates may provide a greater understanding of this

complex thermal behavior, where others have interpreted

similar thermal behavior as a result of conformational

disorder,^56,64,65or plastic crystalline behavior as extensively

reported by MacFarlane and co-workers.^66–69

Without exception, the T_gfor salts of the same cation

structure decreased in the order of [X]^À4 [NO₃]^À

4

[N(CN)₂]^À. In addition, compounds that showed melting

behavior also followed this trend (N-cyanomethyl-functionalized:

T_m= 174 1C, 4[Cl]; 103 1C, 4[NO₃]; 67 1C, 4[N(CN)₂];

N-(2-cyanoethyl)-functionalized: T_m= 143 1C, 5[Br]; 62 1C,

5[NO₃]; 12 1C, 5[N(CN)₂]). Increasing proton aﬃnity and

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Fig. 2 Comparison of ﬁrst and second heating cycle DSC data

exemplifying diﬀerent classes of thermal behavior: 16[N(CN)₂]

(Class I), 6[Cl] (Class II), 12[Br] (Class III), and 4[NO₃] (Class IV).

Fig. 4 Comparison of glass transition (T_g) and liquid–liquid transition

(T_lÀl) trends in DSC data for N-cyanomethyl- (bottom) and N-(4-cyano-

butyl)-functionalized (top) chloride salts with diﬀerent N-alkyl

substituents (N-methyl, N-butyl, and N-(2-cyanoethyl)).

liquid-state properties at lower temperatures.³⁷In Fig. 4,

the observed trends in thermal behavior with changing

N-cyanoalkyl and N-alkyl substituent lengths are illustrated

for a selection of the chloride salts reported here.

A higher T_gwas observed for N-methyl-substituted 4[Cl]

compared to analogous N-butyl 11[Cl] (Fig. 4, bottom), where

less eﬃcient packing of N-butyl- vs. N-methyl-substituted

cations has been reported to promote the liquid state at

lower temperatures.²Higher T_gvalues were observed for

N-(2-cyanoethyl)-substituted imidazolium halides (16[Cl]

and 18[Cl], Fig. 4), and it has been suggested that the lone

pair- and p-electrons of the nitrile functional group are capable

of inter-ion interactions (as seen in the crystal structures of

10[Br], 4[NO₃], and 4[N(CN)₂]) which may contribute to

higher T_gvalues.²⁰The cation–cation contacts observed in

the crystal structures of the N-cyanoethyl-substituted 5[Br]

reinforces this claim, where such organization of the IL

structure though hydrogen bonding can result in elevated T_g

values. Finally, T_gvalues are generally lower for longer

N-cyanoalkyl-functionalized salts (e.g., N-(4-cyanobutyl), Fig. 4,

top) in comparison with shorter analogs (e.g., N-cyanomethyl,

Fig. 4, bottom), similar to the N-alkyl chain-length eﬀect

previously described.²

Fig. 3 Selected DSC traces showing varying degrees of curvature in

T_lÀltransition from a super-cooled liquid state on the second heating

cycle.

diﬀusivity of the negative charge in the anion, in part, may

explain the lower T_gobserved for nitrate and dicyanamide

salts, respectively.^70,71These factors can also aﬀect the hydrogen-

bonding interactions of the anion and, thus, inﬂuence the

molecular packing and the observed melting points for the

compounds.⁷²Other factors such as diﬀerences in the anion

size ([X]^Ào [NO₃]^Ào [N(CN)₂]^À) have also been found to

correlate with decreasing melting points in ILs.⁷³

As with the halide series, several N-methyl-substituted

nitrate salts with shorter N-cyanoalkyl chains showed melting

transitions (T_m= 103 1C, 4[NO₃]; 62 1C 5[NO₃]; 42 1C,

10[NO₃]), again, presumably due to the more eﬃcient packing

of N-methyl- vs. N-butyl-substituted cations.¹⁷Also similar to

the halide series, the glass transitions for nitrate salts were

found to decrease with increasing N-cyanoalkyl chain length

(considering nitrates, N-methyl: T_g= À47 1C, 5[NO₃] vs. À56 1C,

6[NO₃]; N-butyl: T_g= À43 1C, 11[NO₃]; À52 1C, 12[NO₃];

À59 1C, 13[NO₃]). However, in contrast to halides, no

signiﬁcant diﬀerences were found for changes in chain length

for longer N-cyanoalkyl-functionalized nitrate salts (compare

T_g= À56 1C, 6[NO₃], À56 1C, 7[NO₃], and T_g= À59 1C,

Shorter N-cyanoalkyl-substituted halide salts with the

N-methyl group showed high temperature melting transitions

(T_m= 174 1C, 4[Cl]; 143 1C, 5[Br], 96 1C, 6[Cl]), whereas only

one case of an N-butyl-substituted halide salt was found to

have a melting transition (T_m= 86 1C, 12[Br]). This behavior

has been attributed to the less eﬃcient packing of ions for

longer N-alkyl and N-cyanoalkyl substituents, resulting in

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13[NO₃], À59 1C, 14[NO₃]), and only small diﬀerences were

observed in glass transitions with variation between N-methyl-

and N-butyl-substituted compounds.

(e.g., T_5%onset= 168 1C, 10[NO₃]; 157 1C, 15[NO₃]) in

comparison with N-cyanoalkyl-functionalized cations in the

same series with longer chain lengths. Thus, N-cyanoalkyl-

functionalized salts appear to be less stable in the nitrate form

compared with analogous halides for shorter N-cyanoalkyl-

functional groups. It is postulated that the proximity of the

nitrile group to the formal charge of the imidazolium ring may

have an activating eﬀect for the decomposition pathway

involving the nitrate anion that is not observed for halides.

Increasing the proximity of the electron-withdrawing nitrile

group to the imidazolium core may result in destabilization

similar to that observed when nitrile groups are directly

appended to the imidazolium core.²⁶

One of the most visible trends in the DSC data resulted from

a variation of the anion, where there was a high coincidence of

low temperature T_gvalues for all N-(2-cyanoalkyl)-functionalized

imidazolium dicyanamide salts (T_g= À67, 5[N(CN)₂]; À62 1C,

17[N(CN)₂]; À61 1C, 18[N(CN)₂]; À66 1C, 19[N(CN)₂];

À66 1C, 20[N(CN)₂]). Interestingly, the N-methyl-substituted

compounds 4-9[N(CN)₂] showed much lower T_gwhen

compared with analogous N-(2-cyanoethyl)-substituted

products 16-20[N(CN)₂]. It seems that the introduction of a

second N-cyanoalkyl substituent in combination with the

cyano groups present on the dicyanamide anion may have a

synergistic eﬀect for increasing T_g, possibly by increasing the

interactions between ions through available p and lone-pair

electrons from a total of four cyano groups per ion pair. In

comparison to analogous halide and nitrate salts, however, ILs

featuring the dicyanamide anion show the lowest T_gvalues

reported here. This is in agreement with the literature, where

dicyanamide-based ILs exhibit some of the lowest glass transition

temperatures and broadest liquid ranges to date.³⁷

N-(2-cyanoethyl)-substituted imidazolium halides 16-20[X]

were generally more stable than their N-methyl and N-butyl

analogs (compare T_5%onset= 196 1C, 16[Cl]; 206 1C, 4[Cl];

186 1C, 11[Cl]). However, thermal stability is greatly reduced

when comparing N-methyl to N-(2-cyanoethyl)-functionalized

dicyanamide salts (4100 1C diﬀerence, see Fig. 7).

Considering the similarity of the T_5%onsetvalues for the

N-(2-cyanoethyl) salts 16-20[N(CN)₂] (Fig. 7, right) with

the 1-(2-cyanoethyl)-3-methylimidazolium dicyanamide salt,

5[N(CN)₂] (Fig. 7, left), we can then consider the possibility

that the 2-cyanoethyl substituent has a key role in the thermal

degradation of the material. This same functional group is

known as a facile leaving group in the deprotection step for the

synthesis of 1-cyanoalkylimidazoles using heat under basic

conditions,³⁹and all N-(2-cyanoethyl)-N-cyanoalkyl-substituted

dicyanamide salt thermal stabilities coincide with that found

Thermogravimetric analysis

In agreement with previous reports,^34,35there was not a

signiﬁcant diﬀerence observed for the thermal stabilities of

halides or nitrates when comparing N-methyl and N-butyl-

substituted compounds within each series (4–7, 10-15[X] and

4–7, 10-15[NO₃], respectively). To illustrate this, the TGA

traces for N-methyl and N-butyl-substituted salts are compared

below in Fig. 5 and 6.

for N-(2-cyanoethyl)-functionalized 5[N(CN)₂] (T_5%onset

=

161 1C). Thus, without the N-(2-cyanoethyl) substituent

(e.g., N-methyl analogs), a more thermally-stable material

results that shows initial mass loss at much higher temperatures.

Halides featuring the N-(2-cyanoethyl) functionality showed

low, uniform decomposition temperatures across the series.

This observed uniformity is also found for the N-(2-cyano-

ethyl)-functionalized dicyanamide compounds, however,

the T_5%onsetvalues are much lower when compared with

analogous halides (T_5%onset(range): 148–170 1C, see Table 1).

As can be noted from the comparative TGA plots provided

here (Fig. 5–7), there are some ILs that did not completely

decompose under the conditions of the TGA experiment.

From analysis of the data in Fig. 5 and 6, the thermal

stability for both N-methyl and N-butyl-substituted salts are

also found to be similar for halide and nitrate analogs with

longer N-cyanoalkyl chains; compare 6, 7, 13, 14[NO₃] and

[X], where all T_5%onsettemperatures are ca. 250 1C as reported

in Table 1. However, as the N-cyanoalkyl chain is shortened,

there is a signiﬁcant decrease in thermal stability observed for

the nitrate salts (e.g., compare T_5%onset= 183 1C, 4[NO₃]; 166 1C,

5[NO₃] (N-methyl) and T_5%onset= 168 1C, 11[NO₃]; 180 1C,

12[NO₃] (N-butyl)). Additionally, the N-(1-cyanoethyl)-

substituted nitrate salts also showed reduced thermal stability

Fig. 5 Comparison of TGA data for N-methyl- (4–7, 10[X], left) and N-butyl-substituted (11-15[X], right) halide salts.

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Fig. 6 Comparison of TGA data for N-methyl- (4–7, 10[NO₃], left) vs. N-butyl-substituted (11-15[NO₃], right) nitrate salts.

Fig. 7 Comparison of TGA plots for N-methyl- (4-9[N(CN)₂], left) vs. N-(2-cyanoethyl)-substituted (16-20[N(CN)₂], right) dicyanamide salts.

For the halide salts, those featuring short N-cyanoalkyl-

functionalized cations (e.g., 4, 5, 10, 11, 15[X]) all showed a

two-step decomposition pattern. Upon initial onset (as reported

in Table 1), decomposition continued gradually from about

300 1C until reaching nearly 10–40% of original mass near 500 1C.

For nitrate salts, all but the N-(2-cyanoethyl)-functionalized

compounds (5, 12[NO₃]) showed this trend, with around

10–30% of initial mass remaining. Char formation was

especially pronounced for N-cyanomethyl (4, 11[NO₃]) and

N-(1-cyanoethyl)-functionalized (10, 15[NO₃]) nitrate salts.

Finally, the highest production of thermally stable material is

evident for the dicyanamide salts, where all salts were found to

result in char formation (30–80% mass). Upon visual inspection

of the material in the TGA pan, the material appeared as a light-

weight foam with a dark gray, metallic sheen.

matter. Schnick^76,77and MacFarlane⁶¹have indicated similar

cyclization and polymerization of cyanamide and dicyanamide

anions. The high productivity for char in all dicyanamide salts

seems to be additive, where the nitrile groups from both

N-cyanoalkyl, as well as the dicyanamide anion are available

for reaction. As the weight percent of the carbonaceous

material is variable depending on the type of cation, as well

as the identity of the anion, there is potential application for

these ﬁndings as a modular system for the design of porous

materials for numerous applications.

Impact, friction, and electrostatic discharge sensitivity

All dicyanamide salts (4–9, 16-20[N(CN)₂]) were found to be

very insensitive (Table 1, last column). Drop-hammer testing

results indicated a range of 170–200 kg cm and, when

compared to impact sensitivity values of other known energetic

materials such as TNT (98 kg cm), RDX (28 kg cm) and DNB

(28 kg cm),⁷⁸the salts reported here are considered to be

insensitive to impact.

There have been reports in the literature for similar formation

of carbonaceous char from nitrile-functionalized imidazolium

salts in the temperature ranges reported above, where cyclization

of nitrile into carbonitride or nitrogen-doped graphene have

found utility as microporous and mesoporous materials for

catalyst support or chemical separation membranes.^74,75The

absence of char formation for 5[NO₃] and 12[NO₃] implies

that, under the temperature and atmosphere of the TGA

experiment, these nitrate salts preferentially undergo complete

thermal decomposition rather than forming carbonaceous

The results from both friction testing (no response at greater

than 211 Newtons for the Julius Peters test) and electrostatic

discharge testing (negative response at 1 Joule determined

from use of Air Force Research Laboratory ESD apparatus)

also provide evidence that these dicyanamide salt structures

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exhibit low sensitivities. These properties would be appreciated in

applications where non-sensitive liquids are desired (e.g., fuels,

lubricants).

As such, the N-cyanoalkyl-substituted imidazolium salts

studied here suggest potential use as building blocks for

porous mesoscale materials that can be further functionalized

to provide a versatile scaﬀold for numerous applications

(e.g., heterogeneous catalysis, chemical separations, etc.).

Conclusions

The focus for this work was to explore the synthesis of new

1-alkyl-3-cyanoalkylimidazolium ILs and to examine the eﬀects

of diﬀerent cation substituent lengths (N-alkyl, N-cyanoalkyl),

as well as energetic anions (nitrate, dicyanamide) on the

observed thermal properties for each salt reported. Most of

the 41 compounds prepared were ILs by deﬁnition (melting

point below 100 1C). DSC analyses indicated several distinct

classes of thermal behavior, including liquid–liquid transitions

from failed attempts for the salt to crystallize from a super-

cooled phase within the timeframe of the DSC experiment.

This thermal behavior was most frequently observed for

compounds with long N-alkyl and N-cyanoalkyl chain lengths,

as well as for most dicyanamide salts.

Experimental

Materials and methods

Reagents were used as obtained from commercial sources

(Sigma-Aldrich, Milwaukee, WI) unless otherwise noted. All

solvents were ‘solvent grade’ and used as received without

additional puriﬁcation. BioRad AG 1-X8 (100–200 mesh with

8% divinylbenzene copolymer cross-linkage) strongly basic

anion exchange resin was converted to (NO₃)^À-form from the

commercially available (Cl)^À-form following the manufacturer’s

protocol,^45,46where the resin was loaded into a glass chromato-

graphic column (1 cm diameter Â 10 cm tall), washed with

5 bed volumes of 0.5 N sodium nitrate solution, and the eluted

solution was spot-checked for completeness of chloride

removal with a 1.0 M silver nitrate solution. Final conditioning

of the nitrate-exchanged resin column was completed by

washing with 2 bed volumes of deionized water.

Melting transitions were observed mainly for short-chain

N-cyanoalkyl-functionalized cations, and the trends for T_g

were generally the same with changing N-cyanoalkyl chain

lengths. Nonetheless, the eﬀects of N-alkyl chain length on T_g

in general often depended on the type of anion present, where

halides often showed a greater decrease in glass transition

temperature than nitrates when comparing N-methyl versus

N-butyl analogs. The dicyanamide salts had uniformly lower

T_gvalues than analogous halides and nitrates, and the

N-methyl-substituted dicyanamide ILs exhibited lower T_g

values than N-(2-cyanoethyl)-functionalized salts.

1

The H and ¹³C NMR spectra were recorded using Bruker

AV-360 and AV-500 (Karlsruhe, Germany) spectrometers

operating at 500 or 360 MHz and 90 or 125 MHz, respectively.

Infrared (IR) analyses were obtained by direct measurement of

the neat samples by utilizing a Perkin-Elmer 100 FT-IR

instrument, Perkin-Elmer (Shelton, CT) featuring an attenuated

total reﬂection (ATR) force gauge, and spectra were obtained

There appeared to be considerably diﬀerent trends in the

observed T_5%onsetvalues obtained by TGA with respect to

changes in the N-alkyl substituent, the N-cyanoalkyl chain

length, and the class of anion present. Halide salts with short

N-cyanoalkyl substituents were less stable than the N-butyl

analogs. Although the diﬀerence between N-methyl and

N-butyl analogs of nitrate salts did not diﬀer signiﬁcantly, there

was a much lower stability in short N-cyanoalkyl-functionalized

nitrates in comparison with longer chain analogs.

in the range of n_max= 650–4000 cm^À1

.

Thermogravimetric Analyses (TGA) were performed using

a TGA 2950, TA Instruments, Inc. (New Castle, DE). These

experiments were conducted under air atmosphere and

measured in the dynamic heating regime. Samples between

5–15 mg were heated from 30–600 1C under constant heating

ramp of 5 1C min^À1with a 30 min isotherm at 75 1C.

Temperatures reported for the decomposition proﬁles for

all materials were established as the onset temperature for

decomposition of the ﬁrst 5% of the sample (T_5%onset).

For the dicyanamide-based ILs, all N-methyl substituted salts

seemed to be very thermally stable in comparison with halides

and nitrates. However, an exception to this was 5[N(CN)₂] which

showed a T_5%onsetmuch lower than the others in the series.

Recognizing the similarity in thermal decomposition behavior

of 5[N(CN)₂] with other N-(2-cyanoethyl)-functionalized

compounds (16-20[N(CN)₂]), it is concluded that the cyanoethyl

functionality may have a profound inﬂuence on the thermal

decomposition pathway observed in the TGA experiment for

these compounds. Furthermore, the prevalence of carbonaceous

char for all compounds seemed to follow the anion trend

[X]^Ào [NO₃]^Ào [N(CN)₂]^À, where all shorter N-cyanoalkyl-

functionalized ILs for halides and nitrates exhibited a character-

istic 2-step decomposition pattern. The exception to this was

for N-(2-cyanoethyl)-functionalized nitrate salts (5[NO₃] and

12[NO₃]), which showed complete decomposition without any

residual material remaining.

Melting point/glass transition analyses were performed by

Diﬀerential Scanning Calorimetry (DSC) using a DSC 2920

Modulated DSC, TA Instruments, Inc. (New Castle, DE)

cooled with a liquid nitrogen cryostat. The calorimeter was

calibrated for temperature and cell constants using indium

(T_m= 156.61 1C; C = 28.71 J g^À1). Data were collected at

atmospheric pressure, where samples were initially heated at a

rate of 5 1C min^À1to a temperature not to exceed 50 1C below

the measured T_5%onset(obtained from TGA). The sample was

then held for a 5 min isotherm prior to two cycles of cooling

and heating (back to upper temperature limit from ﬁrst

heating) at a rate of 5 1C min^À1spaced by 5 min isothermal

holding at lower (T = À100 1C, unless otherwise stated) and

upper (as indicated above) endpoint temperatures. Samples

between 5–15 mg were used in aluminum sample pans (sealed,

then perforated with a pin-hole to equilibrate pressure resulting

from potential expansion of evolved gases). The DSC was

adjusted so that zero heat ﬂow was between 0 and À0.5 mW,

Finally, in the case of the dicyanamide salts, the most char

production was clearly evident, where up to 80% of the

original weight was found to remain up to nearly 500 1C.

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and the baseline drift was less than 0.1 mW over the temperature

range of 0–180 1C. An empty sample pan served as the

reference. Temperatures reported for the glass transition (T_g)

and melting (T_m) were established as the onset temperature for

the endothermic change in heat ﬂow measured through the

material and as the onset temperature for the exothermic

change in heat ﬂow measured in the case of observed crystall-

ization (T_cryst).

Caution. Chloroacetonitrile is

a

hazardous irritant/

lachrymator potentially tumorigenic/teratogenic/mutagenic.

Protective clothing/gloves and a properly ventilated work-

space should be utilized when handling this material. Besides,

this material is combustable as liquid or vapor, and scaled-up

exothermic reactions with bases should be controlled by

cooling. Please refer to Material Safety Data Sheet (MSDS)

for further details (CAS # 107-14-2).

Impact sensitivity testing was performed at the Air Force

Research Laboratory (Edwards Air Force Base, CA). Analysis

was carried out on an Olin-Mathieson drop weight tester,

where a small sample (20 mg) was placed in a standard sample

cup (liquid or solid cell employed as appropriate), and a

multi-kilogram mass was dropped vertically from measured

heights upon the closed sample.^79–81The drop height in

centimetres was recorded, and the point was determined at

which 50% of impacts were positive. A sample of water

was used as a standard calibration for liquid samples, and

1,3,5-trinitroperhydro-1,3,5-triazine was used for calibration

for solid samples.

1-Cyanomethyl-3-methylimidazolium chloride (4[Cl]). Compound

4[Cl] was prepared from 1 (2.870 g, 35 mmol). White solid, water

soluble (90%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.56

(s, 1H), 8.00 (t, 1H), 7.87 (t, 1H), 5.82 (s, 2H), 3.92 (s, 3H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 138.3, 124.8, 123.0, 115.3,

37.2, 36.6. FT-IR (n_maxin cm^À1): 3392 (w), 3032 (s), 2977 (s), 2906

(s), 1575 (s), 1565 (s), 1439 (m), 1337 (m), 1254 (s), 1168 (s),

915 (m).

1-Butyl-3-cyanomethylimidazolium chloride (11[Cl]). Compound

11[Cl] was prepared from 2 (2.612 g, 20 mmol). Amber liquid

(57%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.70 (s, 1H), 8.04

(d, 1H), 7.99 (d, 1H), 5.83 (s, 2H), 4.27 (t, 2H), 1.75 (pent, 2H),

1.23 (hex, 2H), 0.88 (T, 3H); ¹³C NMR (125 MHz, DMSO-d₆)

d ppm 137.2, 123.0, 122.6, 114.7, 48.8, 36.7, 31.1, 18.6, 13.1; FT-IR

(n_maxin cm^À1): 3370 (b), 3135 (w), 3064 (m), 2960 (s) 2934 (s), 2874

(m), 1638 (w), 1558 (s), 1463 (m), 1420 (w), 1337 (w), 1251 (w),

1209 (w), 1163 (s), 1115 (w), 1030 (m), 926 (w), 872 (w), 755 (s),

708 (w), 662 (w).

For friction testing,

a Julius-Peters friction tester was

employed whereby a small amount of sample (20 mg) was placed

on a small ceramic square plate and a steel pin was pushed across

the sample under a known load. Any evidence of discoloration,

odor, smoke, or spark was considered a positive test. All samples

tested were insensitive to friction, showing negative response at

greater than 211 Newton. Sensitivity to electrostatic discharge

(ESD) was determined using the AFRL ESD test apparatus with

initial sample test level at 5000 V with capacitance set to deliver

0.25 J. Each of the samples was determined to be insensitive

to ESD, as they all showed negative response under 1 Joule

when tested.

General procedure to prepare 5-10, 12-15[X]. Compounds

5-10, 12-15[X] were obtained under solvent-free conditions as

with 4[Cl] and 11[Cl], but with the addition of heat during the

reaction. Yields and reaction times were not optimized, and

the following serves as a general procedure. To a 20 mL Ace

Glass high temperature vial ﬁtted with a Teﬂon screw-cap, the

appropriate haloalkylnitrile (10% molar excess) was added to

1-alkylimidazole (1 or 2). Upon fastening the screw-cap on the

vial, the mixture was stored in a furnace set to 70 1C for 48 h.

As exceptions to this procedure, compound 5[Br] was

inadvertently left for 20 days in the furnace at 70 1C, and

compound 12[Br] was obtained from ﬁrst preparing 1-(2-cyano-

ethyl)imidazole, 3, by literature methods (see 3, below),³⁹

which was then alkylated with 1-bromobutane in 10% molar

excess. After each reaction was ﬁnished, the reaction mixtures

were washed with ethyl acetate or acetone (4 Â 5 mL) prior to

drying ﬁrst by rotary evaporation followed by removal of

residual solvent by high vacuum for 24 h at room temperature.

Single-crystal X-ray diﬀraction data were collected for

compounds 5[Br], 10[Br], 4[NO₃], and 4[N(CN)₂] on a Bruker

SMART diﬀractometer equipped with a CCD area detector

using graphite-monochromated Mo-Ka (l = 0.71073 A)

radiation. Crystals were cooled to À100 1C during data

collection. The structures were solved using the SHELXTL

software package⁸²and the absorption corrections were made

with SADABS.⁸³The structures were reﬁned by full-matrix

least-squares on F². Non-hydrogen atoms were located from

the diﬀerence map and reﬁned anisotropically. Hydrogen atoms

were constrained to idealized positions except methyl hydrogen

atoms which were reﬁned using a riding rotating model.

Synthetic protocols

N-Cyanoalkyl-functionalized imidazolium halides (4-20[X])

General procedure to prepare 4[Cl] and 11[Cl]. Compounds

4[Cl] and 11[Cl] were each prepared based on a previous

method.⁴²Yields and reaction times were not optimized, and

the following serves as a general procedure. In a 50 mL round

bottom ﬂask with a magnetic stirbar, chloroacetonitrile

(10% molar excess) was slowly added to 1-alkylimidazole

(1 or 2, respectively). The mixture was stirred at room

temperature overnight, and the resulting product was washed

with ethyl acetate (4 Â 5 mL) and dried by rotary evaporation

prior to ﬁnal removal of residual solvent by high vacuum at

room temperature for 24 h.

1-(2-Cyanoethyl)imidazole (3). Compound 3 was prepared

by combining imidazole (5.301 g, 100 mmol) with acrylonitrile

(6.799 g, 110 mmol) in toluene (20 mL) and then adding

triethylamine (1 mL). With the addition of a magnetic Teﬂon

stir bar, the reaction mixture was stirred and heated to 50 1C

and maintained at this temperature for 30 h when the product

separated as a lower liquid phase from the toluene solution.

Puriﬁcation of 3 was achieved by removing the solvent from

the lower product phase by ﬁrst decanting and then washing

the product phase of residual solvent and starting materials

with 3 Â 10 mL of acetone. After removal of residual solvent

by rotary evaporation, ﬁnal puriﬁcation involved further

c

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drying under high vacuum at room temperature for 24 h prior

to use. Amber liquid (71%); ¹H NMR (500 MHz, DMSO-d₆) d

ppm 7.69 (s, 1H), 7.23 (t, 1H), 6.92 (t, 1H), 4.26 (t, 2H), 3.04

(t, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.3, 128.7,

119.2, 118.5, 41.6, 19.5; FT-IR (n_maxin cm^À1): 3551 (m), 3473

(m), 3413 (w), 3240 (m), 3078 (w), 2966 (w), 2252 (w), 1616 (s),

1538 (m), 1410 (m), 1374 (m), 1376 (m), 1275 (m), 1231 (m),

1181 (m), 1116 (w), 1034 (w), 907 (m), 758 (m), 705 (m).

(n_maxin cm^À1): 3381 (b), 3141 (w), 3060 (m), 2936 (m), 2864

(w), 2242 (w), 1571 (s), 1459 (m), 1426 (m), 1362 (w), 1336 (w),

1167 (s), 1094 (w), 1029 (w), 835 (w), 755 (m), 697 (w).

1-(6-Cyanohexyl)-3-methylimidazolium bromide (9[Br]). Com-

pound 9[Br] was prepared from 1 (1.483 g, 18 mmol). Amber

1

liquid (92%); H NMR (500 MHz, DMSO-d₆) d ppm = 9.23

(s, 1H), 7.82 (s, 1H), 7.74 (s, 1H), 4.18 (t, 2H), 3.87 (s, 3H), 2.50

(t, 2H), 1.80 (pent, 2H), 1.55 (pent, 2H), 1.37 (pent, 2H), 1.27

(pent, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm = 137.0,

124.1, 122.7, 121.1, 49.1, 36.2, 29.5, 27.8, 25.1, 24.9, 16.5; FT-IR

(n_maxin cm^À1): 3417 (b), 3141 (w), 3059 (m), 2934 (m), 2861 (w),

2242 (w), 1731 (w), 1570 (s), 1459 (m), 1426 (m), 1365 (w), 1337

(w), 1297 (w), 1246 (w), 1164 (s), 1088 (w), 1046 (w), 1020 (w),

829 (m), 756 (m), 697 (w).

Caution. Acrylonitrile is a very hazardous irritant and

permeator for skin and eyes, and requires protective clothing

and a properly ventilated workspace. Prolonged exposure

should be avoided, as there may be carcinogenic/teratogenic/

mutagenic eﬀects, as well as toxicity related to target organs

including blood, liver, central nervous system, and kidneys.

Additionally, explosive mixtures can be formed when vapors

are allowed to mix with air, and accumulation of evaporated

material is to be avoided. Please refer to Material Safety Data

Sheet (MSDS) for further precautionary details (CAS #107-13-1).

1-(1-Cyanoethyl)-3-methylimidazolium bromide (10[Br]). Com-

pound 10[Br] was prepared from 1 (0.615 g, 7.4 mmol). Yellow

powder (85%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.53

(s, 1H), 8.12 (s, 1H), 7.79 (s, 1H), 6.17 (q, 1H), 3.90 (s, 3H), 1.90

(d, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.5, 125.1,

121.4, 117.5, 45.7, 36.7, 19.5; FT-IR (n_maxin cm^À1): 3172 (w),

3150 (w), 3170 (w), 3043 (s), 3012 (s), 2882 (m), 2847 (w), 2618

(w), 2556 (w), 2249 (w), 1776 (w), 1735 (w), 1654 (w), 1580 (m),

1552 (s), 1448 (m), 1419 (m), 1381 (w), 1324 (w), 1302 (m), 1260

(w), 1182 (s), 1168 (s), 1100 (s), 1020 (m), 989 (w), 892 (w), 863

(s), 843 (m), 768 (s), 717 (m), 674 (w).

1-(2-Cyanoethyl)-3-methylimidazolium bromide (5[Br]). Com-

pound 5[Br] was prepared from 1 (4.621 g, 38 mmol). Yellow

solid (86%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.31 (s, 1H),

7.88 (s, 1H), 7.80 (s, 1H), 4.53 (t, 2H), 3.90 (s, 3H), 3.25 (t, 2H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.5, 124.4, 122.8,

118.2, 44.9, 36.5, 19.2; FT-IR (n_maxin cm^À1): 3139 (w), 3082 (s),

3042 (s), 2958 (w), 2845 (w), 2250 (w), 1780 (w), 1761 (w), 1727

(w), 1676 (w), 1575 (m), 1559 (w), 1448 (w), 1426 (w), 1401 (w),

1359 (w), 1341 (w), 1280 (w), 1199 (w), 1160 (s), 1092 (w), 1022

(w), 892 (w), 864 (s), 789 (s), 741 (s), 652 (m).

1-Butyl-3-(2-cyanoethyl)imidazolium bromide (12[Br]). Com-

pound 12[Br] was prepared by alkylation of 3 (1.521 g, 12 mmol)

with 1-bromobutane (2.125 g, 15 mmol). Yellow solid (86%);

¹H NMR (500 MHz, DMSO-d₆) d ppm 9.43 (s, 1H), 7.92 (d,

1H), 7.91 (d, 1H), 4.53 (t, 2H), 4.23 (t, 2H), 3.28 (t, 2H), 1.78

(pent, 2H), 1.24 (hex, 2H), 0.89 (t, 3H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm 136.4, 122.6, 122.3, 117.5, 48.6, 44.3, 31.1,

18.5, 18.5, 13.1; FT-IR (n_maxin cm^À1): 3378 (b), 3134 (w), 3055

(m), 2960 (m), 2935 (m), 2875 (w), 1707 (m), 1640 (w), 1557 (s),

1463 (w), 1421 (w), 1362 (m), 1223 (w), 1160 (s), 1115 (w), 1020

(w), 925 (w), 871 (w), 754 (s), 708 (w).

1-(3-Cyanopropyl)-3-methylimidazolium chloride (6[Cl]). Com-

pound 6[Cl] was prepared from 1 (3.610 g, 44 mmol). Yellow

solid (92%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.42 (s, 1H),

7.87 (t, 1H), 7.78 (t, 1H), 4.28 (t, 2H), 3.86 (s, 3H), 2.61 (t, 2H),

2.14 (pent, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.9,

123.5, 122.2, 119.5, 47.4, 35.6, 25.2, 13.4; FT-IR (n_maxin cm^À1):

3435 (s), 3371 (s), 3244 (w), 3126 (w), 3109 (w), 3063 (m), 2971

(w), 2938 (w), 2915 (w), 2839 (w), 2244 (m), 2186 (w), 2111 (w),

1731 (w), 1655 (w), 1619 (m), 1574 (s), 1562 (s), 1453 (m), 1425

(m), 1391 (w), 1344 (w), 1334 (w), 1325 (w), 1266 (w), 1160 (s),

1092 (s), 1017 (m), 867 (s), 850 (w), 774 (s), 723 (w), 665 (m).

1-(3-Cyanopropyl)-3-butylimidazolium chloride (13[Cl]). Com-

pound 13[Cl] was prepared from 2 (4.969 g, 40 mmol). Amber

liquid (45%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.44

(s, 1H), 7.87 (s, 1H), 7.85 (s, 1H), 4.28 (t, 2H), 4.17 (t, 2H),

2.61 (t, 2H), 2.15 (pent, 2H), 1.78 (pent, 2H), 1.28 (sext, 2H), 0.90

(t, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.3, 122.4,

122.3, 119.5, 48.5, 47.6, 31.1, 25.0, 18.7, 13.4, 13.2;

FT-IR (n_maxin cm^À1): 3372 (b), 3134 (w), 3049 (m), 2959 (m),

2935 (m), 2873 (w), 2245 (s), 1639 (w), 1561 (s), 1370 (w), 1335

(w), 1163 (s), 1115 (w), 1054 (w), 1021 (w), 949 (w), 852 (m),

753 (m).

1-(4-Cyanobutyl)-3-methylimidazolium chloride (7[Cl]). Com-

pound 7[Cl] was prepared from 1 (1.232 g, 15 mmol). Amber

1

liquid (95%); H NMR (500 MHz, DMSO-d₆) d ppm = 9.24

(s, 1H), 7.82 (t, 1H), 7.75 (t, 1H), 4.24 (t, 2H), 3.86 (s, 3H), 2.57

(t, 2H), 1.87 (pent, 2H), 1.53 (pent, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 137.1, 124.1, 122.7, 120.9, 48.3, 36.3, 29.0,

22.0, 16.2; FT-IR (n_maxin cm^À1): 3372 (b), 3143 (w), 3058 (m),

2952 (w), 2869 (w), 2242 (w), 1637 (w), 1571 (s), 1458 (m), 1427

(w), 1385 (w), 1335 (w), 1293 (w), 1161 (s), 1091 (w), 1020 (w),

843 (w), 760 (m), 697 (w).

1-(4-Cyanobutyl)-3-butylimidazolium chloride (14[Cl]). Com-

pound 14[Cl] was prepared from 2 (1.870 g, 15 mmol). Amber

liquid (97%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.62

(s, 1H), 7.91 (d, 1H), 7.90 (d, 1H), 4.27 (t, 2H), 4.20 (t, 2H),

2.59 (t, 2H), 1.89 (pent, 2H), 1.78 (pent, 2H), 1.53 (pent, 2H),

1.24 (sext, 2H), 0.89 (t, 3H); ¹³C NMR (125 MHz, DMSO-d₆)

d ppm 136.2, 122.4, 122.3, 120.2, 48.7, 31.1, 28.3, 21.4, 18.6, 15.5,

13.1; FT-IR (n_maxin cm^À1): 3372 (b), 3131 (w), 3046 (m), 2957

(s), 2934 (s), 2872 (m), 2242 (w), 1638 (w), 1561 (s), 1458 (s), 1370

1-(5-Cyanopentyl)-3-methylimidazolium bromide (8[Br]). Com-

pound 8[Br] was prepared from 1 (1.724 g, 21 mmol). Amber

1

liquid (94%); H NMR (500 MHz, DMSO-d₆) d ppm = 9.31

(s, 1H), 7.85 (s, 1H), 7.77 (s, 1H), 4.21 (t, 2H), 3.87

(s, 3H), 2.52 (t, 2H), 1.83 (pent, 2H), 1.59 (pent, 2H), 1.33 (pent,

2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm = 136.8,

123.8, 122.5, 120.8, 48.6, 36.0, 28.8, 24.7, 24.3, 16.3; FT-IR

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(w), 1333 (w), 1259 (w), 1160 (s), 1116 (w), 1050 (w), 1022 (w),

949 (w), 879 (m), 753 (s).

1290 (w), 1234 (w), 1158 (s), 1108 (w), 1083 (w), 1051 (w), 1033

(w), 915 (w), 826 (m), 754 (m), 660 (w).

1-(6-Cyanohexyl)-3-(2-cyanoethyl)imidazolium bromide (20[Br]).

Compound 20[Br] was prepared from 3 (1.067 g, 8.8 mmol).

Amber liquid (86%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.36

(s, 1H), 7.89 (d, 2H), 4.52 (t, 2H), 4.23 (t, 2H), 3.25 (t, 2H), 2.51

(t, 2H), 1.81 (pent, 2H), 1.54 (pent, 2H), 1.35 (pent, 2H), 1.26

(pent, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.0, 123.3,

123.0, 121.1, 118.2, 49.4, 44.9, 29.4, 27.8, 25.0, 24.9, 19.2, 16.5;

FT-IR (n_maxin cm^À1): 3409 (b), 3135 (w), 3058 (m), 2838 (s),

2863 (m), 2244 (w), 1628 (w), 1561 (s), 1455 (s), 1422 (m),

1358 (w), 1340 (w), 1234 (w), 1161 (s), 1107 (w), 1052 (w),

1033 (w), 914 (w), 824 (w), 757 (s), 659 (w).

1-Butyl-3-(1-cyanoethyl)imidazolium bromide (15[Br]). Com-

pound 15[Br] was prepared from 2 (2.755 g, 22 mmol). Amber

liquid (87%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.71

(s, 1H), 8.19 (s, 1H), 8.04 (s, 1H), 6.27 (q, 1H), 4.24 (t, 2H),

1.90 (d, 3H), 1.79 (pent, 2H), 1.27 (sext, 2H), 0.88 (t, 3H); ¹³C

NMR (125 MHz, DMSO-d₆) d ppm 136.4, 123.3, 121.0, 117.0,

48.9, 46.2, 31.0, 18.7, 13.2; FT-IR (n_maxin cm^À1): 3126 (w), 3046

(s), 2959 (s), 2934 (s), 2873 (m), 2251 (w), 1691 (w), 1569 (m),

1551 (m), 1458 (m), 1381 (w), 1337 (w), 1315 (w), 1260 (w), 1210

(w), 1165 (s), 1115 (w), 1088 (w), 1021 (w), 983 (w), 948 (w), 842

(w), 752 (m).

N-Cyanoalkyl-functionalized imidazolium nitrates (4–7,

9-15[NO₃])

1-(2-Cyanoethyl)-3-cyanomethylimidazolium chloride (16[Cl]).

Compound 16[Cl] was obtained from 3 (2.423 g, 20 mmol).

1

White solid (87%); H NMR (500 MHz, DMSO-d₆) d ppm

Preparation of nitrate-form of anion exchange resin. Strongly

basic anion exchange resin (BioRad AG 1-X8, chloride form)

was converted to nitrate form by successive washes of a loaded

column (B8 cm³bed volume) with 1 N sodium nitrate

solution. Each eluted fraction was tested with 0.1 M silver

nitrate solution to visually indicate when the resin had been

fully exchanged (e.g., no silver chloride precipitate formed).

Final conditioning of the nitrate resin column included

washing with 2 bed volumes of deionized water.

7.82 (s, 1H), 4.51 (t, 2H), 3.14 (t, 2H), 2.74 (s, 2H); ¹³C NMR

(125 MHz, DMSO-d₆) d ppm 146.0, 122.2, 118.3, 43.6, 18.6,

10.0; FT-IR (n_maxin cm^À1): 3327 (s), 3276 (s), 3167 (w), 3140

(w), 3126 (w), 3068 (m), 3036 (s), 2986 (m), 2954 (w), 2855 (w),

2254 (m), 1808 (w), 1693 (w), 1678 (w), 1651 (m), 1574 (w),

1561 (s), 1511 (w), 1449 (m), 1418 (m), 1404 (m), 1367 (w),

1349 (m), 1289 (m), 1238 (w), 1161 (s), 1113 (m), 1051 (w),

1020 (w), 1000 (w), 952 (w), 925 (m), 914 (m), 907 (m), 863 (s),

797 (s), 750 (m), 661 (s).

General procedure for the exchange of halides for nitrate

anion and product isolation, 4-7, 9-15[NO₃]. A solution of

N-cyanoalkyl imidazolium halide salt (4–7, 9-15[X]) was

prepared based upon the calculated ‘dry weight’ capacity of

the resin being used (2.6 meq/g dry resin). All halide salts were

eluted as solutions in 100 mL of water though a prepared

column of the nitrate-exchanger resin. All collected fractions

were spot-tested with 0.1 M silver nitrate solution to conﬁrm

the absence of halide (e.g., no precipitate shown) prior to

combining and removing water, ﬁrst by evaporation under air

stream and then further drying under high vacuum overnight.

1-(3-Cyanopropyl)-3-(2-cyanoethyl)imidazolium chloride (17[Cl]).

Compound 17[Cl] was prepared from 3 (1.824 g, 15 mmol).

1

Amber liquid (91%); H NMR (500 MHz, DMSO-d₆) d ppm

9.59 (s, 1H), 7.97 (s, 1H), 7.95 (s, 1H), 4.55 (t, 2H), 4.33 (t, 2H),

3.28 (t, 2H), 2.62 (t, 2H), 2.16 (pent, 2H); ¹³C NMR

(125 MHz, DMSO-d₆) d ppm 137.5, 123.2, 123.1, 120.1,

118.2, 48.3, 44.9, 25.7, 19.1, 14.0; FT-IR (n_maxin cm^À1):

3370 (b), 3140 (w), 3058 (m), 2963 (w), 2906 (w), 2845 (w),

2248 (w), 1705 (w), 1638 (w), 1563 (s), 1450 (m), 1420 (m),

1358 (w), 1342 (w), 1229 (w), 1163 (s), 1109 (w), 1076 (w), 1050

(w), 1021 (w), 910 (w), 847 (w), 826 (w), 762 (s).

1-Cyanomethyl-3-methylimidazolium nitrate (4[NO₃]). Com-

pound 4[NO₃] was prepared from 4[Cl] (1.063 g, 6.5 mmol).

White solid (81%); ¹H NMR (500 MHz, DMSO-d₆) d ppm

9.26 (s, 1H), 7.89 (t, 1H), 7.79 (t, 1H), 5.59 (s, 2H), 3.89

(s, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.7, 124.3,

122.4, 114.6, 36.7, 36.0; FT-IR (n_maxin cm^À1): 3431 (b), 3154 (w),

3130 (w), 3088 (m), 3035 (m), 3011 (m), 2966 (w), 1789 (w),

1748 (w), 1662 (w) 1581 (m), 1561 (m), 1472 (w), 1457 (w),

1425 (m), 1413 (m), 1387 (m), 1328 (s), 1275 (s), 1166 (s),

11 087 (w), 1090 (w), 1041 (w), 1020 (w), 953 (w), 921 (w), 900

(s), 827 (m), 783 (m), 775 (m), 749 (m), 725 (w) 708 (w), 673 (w).

1-(4-Cyanobutyl)-3-(2-cyanoethyl)imidazolium chloride (18[Cl]).

Compound 18[Cl] was prepared from 3 (2.445 g, 20 mmol).

1

Amber liquid (61%); H NMR (500 MHz, DMSO-d₆) d ppm

9.20 (s, 1H), 7.81 (s, 1H), 7.73 (s, 1H), 4.17 (t, 2H), 2.51 (t, 2H),

1.80 (pent, 2H), 1.55 (pent, 2H), 1.37 (pent, 2H), 1.27 (pent, 2H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.0, 124.1, 122.7,

121.1, 49.1, 36.2, 29.5, 27.8, 25.1, 16.5; FT-IR (n_maxin cm^À1):

3376 (b), 3137 (w), 3054 (m), 2958 (s), 2246 (w), 1639 (w), 1561

(s), 1455 (m), 1423 (m), 1363 (w), 1340 (w), 1236 (w), 1161 (s),

1052 (w), 1033 (w), 914 (w), 871 (w), 828 (w), 759 (s), 660 (w).

1-(2-Cyanoethyl)-3-methylimidazolium nitrate (5[NO₃]). Com-

pound 5[NO₃] was prepared from 5[Br] (1.281 g, 5.9 mmol).

Yellow solid (84%); ¹H NMR (500 MHz, DMSO-d₆) d ppm

9.28 (s, 1H), 7.82 (t, 1H), 7.76 (t, 1H), 3.89 (s, 3H),

3.21 (t, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.0,

123.9, 122.2, 117.6, 44.3, 35.8, 18.5; FT-IR (n_maxin cm^À1): 3156

(w), 3126 (w), 3088 (m), 3040 (m), 2258 (m), 1746 (w), 1664 (w),

1579 (m), 1566 (m), 1450 (w), 1426 (w), 1363 (m), 1332 (s), 1301

(m), 1176 (s), 1084 (w), 1042 (w), 1029 (w), 1016 (w), 943 (w),

888 (m), 877 (m), 827 (m), 775 (s), 748 (m), 706 (w), 657 (m).

1-(5-Cyanopentyl)-3-(2-cyanoethyl)imidazolium bromide (19[Br]).

Compound 19[Br] was prepared from 3 (1.273 g, 10 mmol).

1

Amber liquid (97%); H NMR (500 MHz, DMSO-d₆) d ppm

9.39 (s, 1H), 7.91 (d, 2H), 4.53 (t, 2H), 4.25 (t, 2H), 3.26 (t, 2H),

2.51 (t, 2H), 1.84 (pent, 2H), 1.59 (pent, 2H), 1.34 (pent, 2H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.0, 123.3, 123.0, 121.0,

118.2, 49.1, 45.0, 28.9, 24.5, 19.2, 16.5; FT-IR (n_maxin cm^À1):

3401 (s), 3140 (w), 3078 (m), 2940 (m), 2867 (w), 2246 (w), 1628

(m), 1561 (s), 1509 (w), 1458 (m), 1421 (m), 1363 (w), 1340 (w),

c

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New J. Chem., 2011, 35, 1701–1717 1713

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1-(3-Cyanopropyl)-3-methylimidazolium nitrate (6[NO₃]).

Compound 6[NO₃] was prepared from 6[Cl] (1.062 g,

5.7 mmol). Amber liquid (76%); ¹H NMR (500 MHz,

DMSO-d₆) d ppm 9.18 (s, 1H), 7.80 (t, 1H), 7.73 (t, 1H),

4.24 (t, 2H), 3.84 (s, 3H), 2.58 (t, 2H), 2.13 (pent, 2H); ¹³C

NMR (125 MHz, DMSO-d₆) d ppm 136.8, 123.6, 122.2, 119.5,

47.5, 35.6, 25.1, 13.3; FT-IR (n_maxin cm^À1): 3151 (w), 3101

(m), 2960 (w), 2247 (w), 1745 (w), 1633 (w), 1576 (m), 1566

(m), 1451 (w), 1425 (w), 1327 (s), 1166 (s), 1084 (w), 1024 (w),

847 (w), 830 (m), 756 (m), 699 (w).

122.3, 119.5, 48.5, 47.7, 31.1, 25.0, 18.7, 13.3, 13.1; FT-IR

(n_maxin cm^À1): 3140 (w), 3096 (w), 2961 (w), 2934 (w), 2875

(w), 2246 (w), 1744 (w), 1564 (m), 1459 (w), 1330 (s), 1162 (s),

1114 (w), 1084 (w), 1040 (w), 1026 (w), 949 (w), 852 (w), 830 (w),

753 (m), 708 (w).

1-(4-Cyanobutyl)-3-butylimidazolium nitrate (14[NO₃]). Com-

pound 14[NO₃] was prepared from 14[Cl] (1.298 g, 5.4 mmol).

1

Amber liquid (79%); H NMR (500 MHz, DMSO-d₆) d ppm

9.25 (s, 1H), 7.82 (d, 1H), 7.81 (d, 1H), 4.21 (t, 2H), 4.17 (t, 2H),

2.56 (t, 2H), 1.88 (dt, 2H), 1.79 (dt, 2H), 1.54 (dt, 2H), 1.26 (dt,

2H), 0.90 (t, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.0,

122.4, 122.3, 120.2, 48.5, 47.9, 31.1, 28.3, 21.5, 18.7, 15.5, 13.1;

FT-IR (n_maxin cm^À1): 3139 (w), 3093 (w), 2961 (w), 2934 (w),

2874 (w), 2244 (w), 1744 (w), 1564 (s), 1459 (m), 1330 (s),

1217 (w), 1160 (s), 1114 (w), 1084 (w), 1039 (w), 1026 (w),

949 (w), 857 (w), 830 (w), 753 (m), 707 (w).

1-(4-Cyanobutyl)-3-methylimidazolium nitrate (7[NO₃]). Com-

pound 7[NO₃] was prepared from 7[Cl] (0.644 g, 3.2 mmol).

1

Amber liquid (83%); H NMR (500 MHz, DMSO-d₆) d ppm

9.17 (s, 1H), 7.78 (t, 1H), 7.72 (t, 1H), 4.21 (t, 2H), 3.85 (s, 3H),

2.54 (t, 2H), 1.87 (dt, 2H), 1.54 (dt, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm 136.6, 123.6, 122.1, 120.2, 47.8, 35.6, 28.4,

21.4, 15.5; FT-IR (n_maxin cm^À1): 3147 (w), 3100 (w), 2955 (w),

2244 (w), 1744 (w), 1574 (s), 1458 (w), 1426 (w), 1330 (s), 1216

(w), 1163 (w), 1084 (w), 1039 (w), 1024 (w), 854 (w), 830 (m), 754

(m), 698 (w).

1-Butyl-(1-cyanoethyl)imidazolium nitrate (15[NO₃]). Com-

pound 15[NO₃] prepared from 15[Br] (1.673 g, 6.5 mmol). Amber

liquid (89%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.49

(s, 1H), 8.12 (t, 1H), 7.95 (t, 1H), 6.01 (q, 1H), 4.21 (t, 2H),

1.90 (d, 3H), 1.79 (pent, 2H), 1.28 (sext, 2H), 0.90 (t, 3H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.4, 123.3, 121.0,

116.9, 49.0, 42.2, 31.0, 18.8, 18.7, 13.1; FT-IR (n_maxin cm^À1):

3253 (s), 3156 (m), 3118 (m), 3083 (m), 2878 (w), 1754 (w), 1587

(m), 1550 (m), 1470 (s), 1335 (m), 1309 (m), 1280 (m), 1162 (w),

1007 (s), 933 (m), 855 (w), 828 (w), 754 (w), 715 (w), 666 (w).

1-(1-Cyanoethyl)-3-methylimidazolium nitrate (10[NO₃]). Com-

pound 10[NO₃] was prepared from 10[Br] (1.314 g, 6.1 mmol).

Yellow solid (95%); ¹H NMR (500 MHz, DMSO-d₆) d ppm 9.44

(s, 1H), 8.09 (s, 1H), 7.85 (s, 1H), 6.05 (q, 1H), 3.89 (s, 3H), 1.89

(d, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 137.0, 124.5,

120.8, 116.9, 45.1, 36.0, 18.8; FT-IR (n_maxin cm^À1): 3149 (w),

3097 (w), 2951 (w), 1747 (w), 1631 (w), 1581 (m), 1557 (m), 1452

(w), 1330 (s), 1261 (w), 1170 (s), 1090 (m), 1041 (w), 1021 (w), 984

(w), 842 (w), 829 (m) 755 (m), 718 (w).

N-Cyanoalkyl-functionalized imidazolium dicyanamide salts

(4–9, 16-20[N(CN)₂])

General procedure to prepare 4–9, 16-20[N(CN)₂]. To a tared

100 mL round-bottom ﬂask, halide precursor salts 4–9,

16-20[X] (2.8 to 18.7 mmol) were each dissolved in 40 mL

deionized water. Silver dicyanamide was prepared by a

literature method,⁸⁴where sodium dicyanamide (15.290 g,

161 mmol) was added to an aqueous solution of silver nitrate

(24.937 g, 147 mmol) at room temperature, and the mixture

was stirred overnight in darkness. The solids were ﬁltered and

washed several times with water, and the washes were then

combined with the ﬁltrate prior to concentrating under air

stream overnight and then further dried under high vacuum

for 24 h. The prepared silver dicyanamide (1.1 equivalents)

was added at room temperature to an aqueous solution of 4–9,

16-20[N(CN)₂] and homogenized using a magnetic Teﬂon

stirbar prior to being brought to 50 1C in darkness and stirred

for 1 h. The resulting yellowish/white solids were ﬁltered and

washed several times with water, and then the aqueous ﬁltrate

was concentrated under an air stream prior to ﬁnal drying on

high vacuum for 48 h at 60 1C. In addition to the routine

characterization by NMR, FT-IR, TGA, and DSC, all

dicyanamide samples were tested for impact and friction

sensitivity.

1-Butyl-3-cyanomethylimidazolium nitrate (11[NO₃]). Com-

pound 11[NO₃] was prepared from 11[Cl] (1.336 g, 6.5 mmol).

1

Amber liquid (76%); H NMR (500 MHz, DMSO-d₆) d ppm

9.39 (s, 1H), 7.93 (t, 1H), 7.91 (t, 1H), 5.61 (s, 2H), 4.22 (t, 2H),

1.77 (pent, 2H), 1.26 (hext, 2H), 0.89 (t, 3H); ¹³C NMR

(125 MHz, DMSO-d₆) d ppm 137.3, 123.1, 122.7, 114.6, 48.9,

36.8, 31.1, 18.7, 13.2; FT-IR (n_maxin cm^À1): 3142 (w), 3100 (w),

2963 (w), 2937 (w), 2875 (w), 2430 (w), 1789 (w), 1560 (w), 1325

(s), 1163 (s), 1115 (m), 1041 (w), 1033 (w), 1021 (w), 926 (w), 832

(s), 754 (m), 708 (w).

1-Butyl-3-(2-cyanoethyl)imidazolium nitrate (12[NO₃]). Com-

pound 12[NO₃] was prepared from 12[Br] (1.544 g, 6.0 mmol).

1

Amber liquid (94%); H NMR (500 MHz, DMSO-d₆) d ppm

9.34 (s, 1H), 7.88 (t, 1H), 7.86 (t, 1H), 4.51 (t, 2H), 4.22 (t, 2H),

3.23 (t, 2H), 1.77 (pent, 2H), 1.26 (sext, 2H), 0.88 (t, 3H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.5, 122.8, 122.4,

117.7, 48.7, 44.4, 31.2, 18.6, 18.5, 13.2; FT-IR (n_maxin cm^À1):

3140 (w), 3096 (w), 3038 (w), 2962 (w), 2935 (w), 2875 (w), 2252

(w), 1745 (w), 1631 (w), 1563 (m), 1459 (m), 1335 (s), 1163 (s),

1113 (w), 1041 (w), 1023 (w), 949 (w), 914 (w), 854 (w), 829 (w),

754 (w).

1-(3-Cyanopropyl)-3-butylimidazolium nitrate (13[NO₃]). Com-

pound 13[NO₃] was prepared from 13[Cl] (1.305, 5.8 mmol).

1-Cyanomethyl-3-methylimidazolium dicyanamide (4[N(CN)₂]).

Compound 4[N(CN)₂] prepared from 4[Cl] (2.510 g, 16 mmol).

White solid (87%); ¹H NMR (500 MHz, DMSO-d₆) d ppm =

9.24 (s, 1H), 7.88 (t, 1H), 7.78 (t, 1H), 5.58 (s, 2H), 3.98 (s, 3H);

¹³C NMR (125 MHz, DMSO-d₆) d ppm = 137.6, 124.2, 122.5,

119.0, 114.6, 36.7, 36.0; FT-IR (n_maxin cm^À1): 3681 (m), 3493

1

Amber liquid (83%); H NMR (500 MHz, DMSO-d₆) d ppm

9.28 (s, 1H), 7.83 (s, 1H), 7.82 (s, 1H), 4.26 (t, 2H), 4.17 (t, 2H),

2.59 (t, 2H), 2.15 (pent, 2H), 1.78 (pent, 2H), 1.26 (sext, 2H), 0.90

(t, 3H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm 136.3, 122.5,

c

1714 New J. Chem., 2011, 35, 1701–1717

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(w), 3149 (m), 3088 (m), 2953 (s), 2867 (w), 2230 (s), 2195 (m),

2125 (s), 1712 (w), 1612 (w), 1577 (w), 1558 (m) 1419 (w), 1410

(w), 1305 (s), 1218 (w), 1170 (s), 1111 (w), 1055 (m), 1033 (m),

933 (w), 906 (w), 857 (m), 745 (s); Impact sensitivity: 4200 kg cm.

35.6, 29.0, 27.3, 24.6, 24.4, 15.9; FT-IR (n_maxin cm^À1): 3667

(w), 3490 (w), 3149 (w), 3104 (w), 2938 (m), 2865 (w), 2230 (s),

2194 (m), 2125 (s), 1625 (w), 1573 (m), 1460 (w), 1425 (w), 1308

(s), 1167 (s), 1055 (m), 1033 (w), 903 (w), 842 (w), 753 (m);

Impact sensitivity: 170 kg cm.

1-(2-Cyanoethyl)-3-methylimidazolium dicyanamide (5[N(CN)₂]).

Compound 5[N(CN)₂] prepared from 5[Br] (3.591 g, 15 mmol).

Amber liquid (74%); ¹H NMR (500 MHz, DMSO-d₆)

d ppm = 9.11 (s, 1H), 7.80 (t, 1H), 7.48 (t, 1H), 4.50

(t, 2H), 3.89 (s, 3H) 3.19 (s, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 136.9, 123.9, 122.2, 119.0, 117.6, 43.3,

35.8, 18.5; FT-IR (n_maxin cm^À1): 3681 (m), 3494 (w), 3150 (w),

3108 (m), 2967 (m), 2865 (w), 2229 (s), 2192 (m), 2119 (s), 1577

(m), 1562 (m) 1455 (w), 1420 (w), 1306 (s), 1165 (s), 1108 (w),

1053 (m), 1033 (m), 904 (w), 844 (m), 750 (m); Impact

sensitivity: 172 kg cm.

1-(2-Cyanoethyl)-3-cyanomethylimidazolium

dicyanamide

(16[N(CN)₂]). Compound 16[N(CN)₂] was prepared from

16[Cl] (1.487 g, 7.5 mmol). Amber liquid (88%); ¹H NMR

(500 MHz, DMSO-d₆) d ppm = 9.38 (s, 1H), 7.96 (t, 1H), 7.91

(t, 1H), 5.63 (s, 2H), 4.56 (t, 2H), 3.21 (s, 2H); ¹³C NMR

(125 MHz, DMSO-d₆) d ppm = 138.3, 123.7, 123.6, 119.6,

118.1, 115.1, 45.3, 37.6, 19.0; FT-IR (n_maxin cm^À1): 3427 (w),

3145 (w), 3114 (w), 3015 (w), 2981 (w), 2233 (s), 2195 (m), 2125

(s), 1692 (w), 1623 (w), 1562 (m), 1457 (w), 1418 (w), 1310 (s),

1233 (w), 1164 (s), 1107 (w), 1080 (w), 1027 (w), 909 (w), 846

(w), 747 (m); Impact sensitivity: 176 kg cm.

1-(3-Cyanopropyl)-3-methylimidazolium dicyanamide (6[N(CN)₂]).

Compound 6[N(CN)₂] prepared from 6[Cl] (1.560 g, 7.2 mmol).

Amber liquid (93%); ¹H NMR (500 MHz, DMSO-d₆) d ppm =

9.11 (s, 1H), 7.76 (s, 1H), 7.70 (s, 1H), 4.23 (t, 2H), 3.84

(s, 3H), 2.57 (t, 2H), 2.13 (m, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 136.7, 123.6, 122.2, 119.5, 47.6, 35.7,

25.1, 13.4; FT-IR (n_maxin cm^À1): 3681 (m), 3428 (m), 3152 (w),

3108 (w), 3010 (w), 2966 (m), 2866 (w), 2233 (s), 2196 (m),

2125 (s), 1632 (w), 1575 (m), 1565 (m) 1454 (w), 1425 (w), 1309

(s), 1166 (s), 1054 (m), 1033 (m), 1015 (w), 905 (w), 843 (w),

751 (m); Impact sensitivity: 170 kg cm.

1-(3-Cyanopropyl)-3-(2-cyanoethyl)imidazolium dicyanamide

(17[N(CN)₂]). Compound 17[N(CN)₂] was prepared from

17[Cl] (4.823 g, 18 mmol). Amber liquid (92%); ¹H NMR

(500 MHz, DMSO-d₆) d ppm = 9.26 (s, 1H), 7.85 (t, 1H), 7.84

(t, 1H), 4.50 (t, 2H), 4.29 (t, 2H), 3.19 (t, 2H), 2.58 (t, 2H), 2.15

(m, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm = 136.7,

122.7, 122.5, 119.4, 119.0, 117.6, 47.8, 44.4, 25.1, 18.5, 13.4;

FT-IR (n_maxin cm^À1): 3491 (w), 3144 (w), 3108 (w), 3015 (w),

2967 (w), 2229 (s), 2193 (m), 2125 (s), 1624 (w), 1564 (m), 1504

(w), 1452 (w), 1420 (w), 1306 (s), 1233 (w), 1161 (s), 1108 (w),

1079 (w), 1047 (w), 1023 (w), 906 (w), 844 (w), 750 (m); Impact

sensitivity: 176 kg cm.

1-(4-Cyanobutyl)-3-methylimidazolium dicyanamide (7[N(CN)₂]).

Compound 7[N(CN)₂] prepared from 7[Cl] (0.563 g,

2.8 mmol). Amber liquid (83%); ¹H NMR (500 MHz,

DMSO-d₆) d ppm = 9.10 (s, 1H), 7.76 (t, 1H), 7.71 (t, 1H),

4.20 (t, 2H), 3.85 (s, 3H), 2.55 (q, 2H), 1.87 (m, 2H), 1.55

(m, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm = 136.5,

123.6, 122.1, 120.2, 119.0, 47.8, 35.7, 28.4, 21.4, 15.6; FT-IR

(n_maxin cm^À1): 3681 (m), 3489 (w), 3149 (w), 3104 (w), 3011

(w), 2950 (m), 2867 (w), 2227 (s), 2192 (m), 2125 (s), 1623 (w),

1574 (m), 1456 (w), 1425 (w), 1305 (s), 1163 (s), 1055 (m), 1033

(w), 1017 (w), 903 (w), 842 (w), 749 (m); Impact sensitivity:

170 kg cm.

1-(4-Cyanobutyl)-3-(2-cyanoethyl)imidazolium dicyanamide

(18[N(CN)₂]). Compound 18[N(CN)₂] was prepared from

18[Cl] (1.541 g, 6.0 mmol). Amber liquid (91%); ¹H NMR

(500 MHz, DMSO-d₆) d ppm = 9.25 (s, 1H), 7.84 (s, 2H), 4.50

(t, 2H), 4.26 (t, 2H), 3.20 (t, 2H), 2.55 (t, 2H), 1.89 (m, 2H),

1.55 (m, 2H); ¹³C NMR (125 MHz, DMSO-d₆) d ppm =

136.5, 122.7, 122.5, 120.2. 119.0, 117.6, 48.1, 44.4, 28.4, 21.4,

18.5, 15.6; FT-IR (n_maxin cm^À1): 3697 (w), 3665 (w), 3488 (w),

3144 (w), 2981 (m), 2939 (m), 2923 (m), 2866 (m), 2844 (m), 2233

(s), 2195 (m), 2125 (s), 1631 (w), 1563 (m), 1509 (w), 1455 (w),

1420 (w), 1310 (s), 1239 (w), 1159 (s), 1107 (w), 1055 (s), 1033 (s),

1016 (s), 908 (w), 827 (w), 748 (m); Impact sensitivity: 174 kg cm.

1-(5-Cyanopentyl)-3-methylimidazolium dicyanamide (8[N(CN)₂]).

Compound 8[N(CN)₂] prepared from 8[Br] (2.299 g, 8.9 mmol).

Amber liquid (84%); ¹H NMR (500 MHz, DMSO-d₆) d ppm =

9.11 (s, 1H), 7.77 (t, 1H), 7.71 (t, 1H), 4.18 (t, 2H), 3.86 (s, 3H),

2.51 (t, 2H), 1.82 (m, 2H), 1.60 (m, 2H), 1.34 (m, 2H); ¹³C NMR

(125 MHz, DMSO-d₆) d ppm = 136.4, 123.5, 122.1, 120.4, 119.0,

48.3, 35.6, 28.4, 24.4, 23.9, 15.8; FT-IR (n_maxin cm^À1): 3681 (w),

3491 (w), 3149 (w), 3104 (w), 3011 (w), 2941 (m), 2866 (w), 2227 (s),

2192 (m), 2125 (s), 1624 (w), 1574 (m), 1460 (w), 1425 (w), 1304 (s),

1168 (s), 1055 (m), 1033 (w), 1017 (w), 903 (w), 841 (w), 751 (m);

Impact sensitivity: 170 kg cm.

1-(5-Cyanopentyl)-3-(2-cyanoethyl)imidazolium dicyanamide

(19[N(CN)₂]). Compound 19[N(CN)₂] was prepared from

19[Br] (2.247 g, 7.6 mmol). Amber liquid (85%); ¹H NMR

(500 MHz, DMSO-d₆) d ppm = 9.26 (s, 1H), 7.85(s, 2H),

4.50 (t, 2H), 4.24 (t, 2H), 3.21 (t, 2H), 2.49 (t, 2H), 1.84 (m,

2H), 1.60 (m, 2H), 1.36 (m, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 136.4, 122.7, 122.4, 120.4, 119.0, 117.6,

48.5, 28.4, 24.4, 23.9, 18.6, 15.9; FT-IR (n_maxin cm^À1): 3707

(w), 3681 (w), 3488 (w), 3144 (w), 2981 (m), 2967 (m), 2939

(m), 2866 (m), 2844 (m), 2229 (s), 2193 (m), 2125 (s), 1563 (m),

1509 (w), 1455 (w), 1420 (w), 1345 (m), 1308 (s), 1160 (s), 1055

(s), 1033 (s), 1016 (s), 906 (w), 826 (w), 749 (m); Impact

sensitivity: 174 kg cm.

1-(6-Cyanohexyl)-3-methylimidazolium dicyanamide (9[N(CN)₂]).

Compound 9[N(CN)₂] was prepared from 9[Br] (1.973 g,

7.2 mmol). Amber liquid (87%); ¹H NMR (500 MHz,

DMSO-d₆) d ppm = 9.10 (s, 1H), 7.76 (s, 1H), 7.69 (s, 1H),

4.16 (t, 2H), 3.85 (s, 3H), 2.48 (t, 2H), 1.80 (m, 2H), 1.56

(m, 2H), 1.40 (m, 2H), 1.34 (m, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 136.4, 123.5, 122.1, 120.5, 190.0, 48.6,

1-(6-Cyanohexyl)-3-(2-cyanoethyl)imidazolium dicyanamide

(20[N(CN)₂]). Compound 20[N(CN)₂] was prepared from

20[Br] (1.401 g, 4.5 mmol). Amber liquid (85%); ¹H NMR

c

This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientiﬁque 2011

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(500 MHz, DMSO-d₆) d ppm = 9.25 (s, 1H), 7.85(q, 2H), 4.49

(t, 2H), 4.21 (t, 2H), 3.21 (t, 2H), 2.49 (t, 2H), 1.80 (m, 2H),

1.54 (m, 2H), 1.36 (m, 2H), 1.22 (m, 2H); ¹³C NMR (125 MHz,

DMSO-d₆) d ppm = 136.4, 122.7, 122.4, 120.5, 119.0,

117.6, 48.8, 44.4, 28.9, 27.2, 24.5, 24.3, 18.6, 15.9; FT-IR

(n_maxin cm^À1): 3697 (w), 3681 (w), 3489 (w), 3144 (w),

2966 (m), 2939 (m), 2866 (m), 2844 (m), 2231 (s), 2194 (m),

2125 (s), 1624 (w), 1563 (m), 1508 (w), 1455 (w), 1421 (w),

1308 (s), 1162 (s), 1055 (s), 1033 (s), 1017 (s), 906 (w), 825 (w),

752 (m); Impact sensitivity: 170 kg cm.

26 A. R. Katritzky, H. Yang, D. Zhang, K. Kirichenko, M. Smiglak,

J. D. Holbrey, W. M. Reichert and R. D. Rogers, New J. Chem.,

2006, 30(3), 349.

27 M. Smiglak, N. J. Bridges, M. Dilip and R. D. Rogers, Chem.–Eur. J.,

2008, 36, 11314.

28 M. Smiglak, C. C. Hines, T. B. Wilson, S. Singh, A. S. Vincek,

K. Kirichenko, A. R. Katritzky and R. D. Rogers, Chem.–Eur. J.,

2010, 16, 1572.

29 Y. Gao, H. Gao, C. Piekarski and J. M. Shreeve, Eur. J. Inorg.

Chem., 2007, 4965.

30 D. B. Zhao, Z. F. Fei, R. Scopelliti and P. J. Dyson, Inorg. Chem.,

2004, 43, 2197.

31 Q. Zhang, Z. Li, J. Zhang, S. Zhang, L. Zhu, J. Yang, X. Zhang

and Y. Deng, J. Phys. Chem. B, 2007, 111, 2864.

32 S.-K. Fu and S.-T. Liu, Synth. Commun., 2006, 36, 2059.

33 F. Mazille, Z. Fei, D. Kuang, D. Zhao, S. M. Zakeeruddin,

Acknowledgements

¨

M. Gratzel and P. J. Dyson, Inorg. Chem., 2006, 45, 1585.

34 J. G. Huddleston, A. E. Visser, W. M. Reichert, H. D. Willauer,

G. A. Broker and R. D. Rogers, Green Chem., 2001, 3, 156.

35 J. D. Holbrey and K. R. Seddon, J. Chem. Soc., Dalton Trans.,

1999, 2133.

This research was supported by the Air Force Oﬃce of

Scientiﬁc Research (Grant FA9550-10-1-0521).

36 C. Oommen and S. R. Jain, J. Hazard. Mater., 1999, 67, 253.

37 D. R. MacFarlane, J. Golding, S. Forsyth, M. Forsyth and

G. B. Deacon, Chem. Commun., 2001, 1430.

References

38 D. M. Drab, J. L. Shamshina, M. Smiglak, C. C. Hines,

D. B. Cordes and R. D. Rogers, Chem. Commun., 2010, 46, 3544.

39 A. Horvath, Synthesis, 1994, 1, 102.

1 T. M. Klapotke and G. Holl, Green Chem., 2001, 3, G75.

¨

2 P. Wasserscheid and W. Keim, Angew. Chem., Int. Ed., 2000, 39,

3772.

40 H. Olivier-Bourbigou and F. Favre, in Ionic Liquids in Synthesis,

ed. P. Wasserscheid and T. Welton, Wiley-VCH, New York, 2008,

2nd edn, pp. 490–491.

41 P. B. Hitchcock, K. R. Seddon and T. Welton, J. Chem. Soc.,

Dalton Trans., 1993, 2639.

42 W. A. Herrmann, L. J. Goossen and M. Spiegler, Organometallics,

1998, 17, 2162.

43 G. Tao, M. Zou, X. Wang, Z. Chen, D. G. Evans and Y. Kou,

Aust. J. Chem., 2005, 58, 327.

44 S.-M. Gong, H.-Y. Ma, X.-H. Wan, Y.-F. Zhao, J.-Y. He and

Q.-F. Zhou, Gaodeng Xuexiao Huaxue Xuebao, 2006, 27, 761.

45 AG 1, AG MP-1 and AG 2 Strong Anion Exchange Resin:Instruction

Manual, BioRad Laboratories: Hercules, CA (LIT212 Rev C;

accessed online August 17, 2010; http://www.biorad.com/web

root/web/pdf/lsr/literature/9114_AG_1.pdf).

3 J. M. Tishkoﬀ and M. R. Berman, 40th AIAA Aerospace Sciences

Meeting & Exhibit, Reno, NV, 2002.

4 G. W. Drake, T. Hawkins, A. Brand, L. Hall, M. Mckay, A. Vij

and I. Ismail, Propellants, Explos., Pyrotech., 2003, 28, 174.

5 R. P. Singh, R. D. Verma, D. T. Meshri and J. M. Shreeve, Angew.

Chem., Int. Ed., 2006, 45, 3584.

6 M. Smiglak, A. Metlen and R. D. Rogers, Acc. Chem. Res., 2007,

40, 1182.

7 G. Steinhauser and T. M. Klapotke, Angew. Chem., Int. Ed., 2008,

47, 3330.

¨

8 S. Trohalaki, R. Pachter, G. W. Drake and T. Hawkins, Energy

Fuels, 2005, 19, 279.

9 H. Xue and J. M. Shreeve, Adv. Mater., 2005, 17, 2142.

10 D. D. Zorn, J. A. Boatz and M. S. Gordon, J. Phys. Chem. B, 2006,

110, 11110.

46 I. Dinares, C. Garcia de Miguel, A. Ibanez, N. Mesquida and

E. Alcalde, Green Chem., 2009, 11, 1507.

11 C. Ye and J. M. Shreeve, J. Phys. Chem. A, 2007, 111, 1456.

12 J. C. Galvez-Ruiz, G. Holl, K. Karaghiosoﬀ, T. M. Klapotke,

¨

47 N. Gathergood, M. T. Garcia and P. J. Scammells, Green Chem.,

2004, 6, 166.

48 B. Clare, A. Sirwardana and D. R. MacFarlane, Top. Curr. Chem.,

2009, 290, 1.

K. Loehnwitz, P. Mayer, H. Noeth, K. Polborn, C. J. Rohbogner,

M. Suter and J. J. Weigand, Inorg. Chem., 2005, 44, 4237.

13 H. Xue, Y. Gao, B. Twamley and J. M. Shreeve, Inorg. Chem.,

2005, 44, 5068.

49 G. W. Drake, K. Tollison, L. Hall and T. Hawkins, in Ionic Liquids

III: Fundamentals, Progress, Challenges and Opportunities,

ed. R. Rogers and K. Seddon, American Chemical Society,

Washington, DC, 2005.

14 M. W. Schmidt, M. S. Gordon and J. A. Boatz, J. Phys. Chem. A,

2005, 109, 7285.

15 P. F. Pagoria, G. S. Lee, A. R. Mitchell and R. D. Schmidt,

Thermochim. Acta, 2002, 384, 187.

50 B. V. Lotsch and W. Schnick, Chem. Mater., 2005, 17, 3976.

51 G. Svehla, Vogel’s Qualitative Inorganic Analysis, Longman

Scientiﬁc & Technical, Essex, UK, 1987, 6th edn, pp. 174–178.

16 H. Gao, C. Ye, O. D. Gupta, J.-C. Xiao, M. A. Hiskey,

B. Twamley and J. M. Shreeve, Chem.–Eur. J., 2007, 13, 3853.

17 T. M. Klapotke and J. Stierstorfer, Dalton Trans., 2009, 643.

¨

52 A. R. Toral, A. P. de los Rıos, F. J. Hernandez, M. H. A. Janssen,

´ ´

R. Schoevaart, F. van Rantwijk and R. A. Sheldon, Enzyme

Microb. Technol., 2007, 40, 1095.

18 S. Date, N. Itadzu, T. Sugiyama, Y. Miyata, K. Iwakuma, M. Abe,

K. Yoshitake, S. Nishi and K. Hasue, Sci. Technol. Ener. Mater.,

2009, 70, 152.

53 H. Zhao, G. A. Baker, Z. Song, O. Olubajo, L. Zanders and

S. M. Campbell, J. Mol. Catal. B: Enzym., 2009, 57, 149.

54 S. Tang and A. V. Mudring, Eur. J. Inorg. Chem., 2009, 1145.

55 A. J. Seeber, M. Forsyth, C. M. Forsyth, S. A. Forsyth, G. Annat

and D. R. MacFarlane, Phys. Chem. Chem. Phys., 2003, 5,

2692.

56 T. Endo and K. Nishikawa, J. Phys. Chem. A, 2008, 112, 7543.

57 W. L. Hough, M. Smiglak, H. Rodriguez, R. P. Swatloski,

S. K. Spear, D. T. Daly, J. Pernak, J. E. Grisel, R. D. Carliss,

M. D. Soutullo, J. J. H. Davis and R. D. Rogers, New J. Chem.,

2007, 31(8), 1429.

19 S. Schneider, T. Hawkins, M. Rosander, G. Vaghjiani,

S. Chambreau and G. Drake, Energy Fuels, 2008, 22, 2871.

20 S. D. Chambreau, S. Schneider, M. Rosander, T. Hawkins,

C. J. Gallegos, M. F. Pastewait and G. L. Vaghjiani, J. Phys.

Chem. A, 2008, 112, 7816.

21 H. Gao, Y.-H. Joo, B. Twamley, Z. Zhou and J. M. Shreeve,

Angew. Chem., Int. Ed., 2009, 48, 2792.

22 Y.-H. Joo, H. Gao, Y. Zhang and J. M. Shreeve, Inorg. Chem.,

2010, 49, 3282.

23 Y. Zhang, H. Gao, Y. Guo, Y.-H. Joo and J. M. Shreeve,

Chem.–Eur. J., 2010, 16, 3114.

58 R. Kurita and H. Tanaka, Science, 2004, 306, 845.

59 K. Murata and H. Tanaka, Nature Commun., 2010, 1, 16.

60 C. P. Fredlake, J. M. Crosthwaite, D. G. Hert, S. N. V. K. Aki and

J. F. Brennecke, J. Chem. Eng. Data, 2004, 49, 954.

61 T. J. Wooster, K. M. Johanson, K. J. Fraser, D. R. MacFarlane

and J. L. Scott, Green Chem., 2006, 8, 691.

24 A. R. Katritzky, S. Singh, K. Kirichenko, J. D. Holbrey,

M. Smiglak, W. M. Reichert and R. D. Rogers, Chem. Commun.,

2005, 868.

25 A. R. Katritzky, S. Singh, K. Kirichenko, M. Smiglak,

J. D. Holbrey, W. M. Reichert, S. K. Spear and R. D. Rogers,

Chem.–Eur. J., 2006, 12, 4630.

c

1716 New J. Chem., 2011, 35, 1701–1717

This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientiﬁque 2011

View Article Online

62 I. Krossing, J. M. Slattery, C. Daguenet, P. J. Dyson,

A. Oleinikova and H. Weingartner, J. Am. Chem. Soc., 2006,

128, 13427.

63 M. Smiglak, PhD Dissertation, The University of Alabama, 2007.

64 S. Jayaraman and E. J. Maginn, J. Chem. Phys., 2007, 127,

214504.

74 P. Kuhn, A. Forget, D. Su, A. Thomas and M. Antonietti, J. Am.

Chem. Soc., 2008, 130, 13333.

75 J. S. Lee, X. Wang, H. Luo, G. A. Baker and S. Dai, J. Am. Chem.

Soc., 2009, 131, 4596.

76 E. Irran, B. J. Jurgens and W. Schnick, Chem.–Eur. J., 2001, 7,

5372.

¨

65 K. Nishikawa, S. Wang, H. Katayanagi, S. Hayashi,

H. Hamaguchi, Y. Koga and K. Tozaki, J. Phys. Chem. B, 2007,

111, 4894.

77 W. Schnick, J. Am. Chem. Soc., 2003, 125, 10288.

78 M. H. Keshavarz and H. R. Pouretedal, J. Hazard. Mater., 2005,

A124, 27.

66 D. R. MacFarlane, J. Huang and M. Forsyth, Nature, 1999, 402,

792.

67 D. R. MacFarlane and M. Forsyth, Adv. Mater., 2001, 13, 957.

68 J. M. Pringle, P. C. Howlett, D. R. MacFarlane and M. Forsyth,

J. Mater. Chem., 2010, 20, 2056.

69 J. M. Pringle, J. Adebahr, D. R. MacFarlane and M. Forsyth,

Phys. Chem. Chem. Phys., 2010, 12, 7234.

70 R. Lungwitz and S. Spange, New J. Chem., 2008, 32, 392.

71 E. I. Izgorodia, M. Forsyth and D. R. MacFarlane, Aust. J. Chem.,

2007, 60, 15.

79 Test methods according to the UN Recommendations on the

Transport of Dangerous Goods, Test 3, 3rd edn, United Nations,

New York and Geneva, 1999.

80 ASTM Method D 2540-70, Standard Method for Drop-Weight

Sensitivity of Liquid Monopropellants, American Society for

Testing and Materials: Philadelphia, PA.

81 Data Bulletin # 61770: Technoproducts Drop-Weight Tester

Procedure for Testing Solids, Technoproducts, Inc., Saratoga, CA.

82 G. M. Sheldrick, SHELXTL version 5.05, Siemens Analytical

X-ray Instruments, Inc., 1996.

72 D. Kun, Z. Suojiang, W. Daxi and Y. Xiaoqian, J. Phys. Chem. A,

2006, 110, 9775.

73 F. Endres and S. Z. Abedinw, Phys. Chem. Chem. Phys., 2006, 8,

2101.

83 G. M. Sheldrick, Program for Semiempirical Absorption Correction of

Area Detector Data, University of Gottingen, Germany, 1996.

¨

84 D. R. MacFarlane, S. A. Forsyth, J. Golding and G. B. Deacon,

Green Chem., 2002, 4, 444.

c

This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientiﬁque 2011

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Article Doi

Synthesis of N-cyanoalkyl-functionalized imidazolium nitrate and dicyanamide ionic liquids with a comparison of their thermal properties for energetic applications

DOI: 10.1039/c0nj00889c

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