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© IBNU SINA INSTITUTE FOR FUNDAMENTAL SCIENCE STUDIES 2013

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ii

Novel Supramolecular Amphiphilic Benzene for Nanosensors of Nitro Anions

Juan Matmin1, Leny Yuliati2 and Hendrik O. Lintang2*

1Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia, 2Ibnu Sina Institute for Fundamental Science Studies,

Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia

*E-mail: hendrik@ibnusina.utm.my (Hendrik Oktendy Lintang) Tel: (60)-7-5536274, Fax: (60)-7-5536080

ABSTRACT

Development of novel nanosensors with high sensitivity and selectivity, quick response time, as well as easy to handle and re-use are currently drive most

of researcher for developing high performance of chemosensors. Although mesoporous silica materials have been reported for detection of nitro anions by

post-grafting and co-condensation of chromophores in the surface or pore of the porous silica, non-homogeneous distribution and low loadings volume of chromophores are the main problems to significantly decrease of the chemosensor performance. Herein, we report the first example of self-assembled

benzene–1,3,5–tricarboxamide bearing amphiphilic amino decoxy triethylene glycol side chains as a specific receptor for detection of nitro anions. The

benzene–1,3,5–tricarboxamide was synthesized by Schotten-Baumann reaction using 1,3,5–benzenetricarbonyl trichloride and amphihilic 1–aminodecoxy triethylene glycol in the presence of triethylamine in dry tetrahydrofuran (THF) under inert condition for overnight. Nuclear Magnetic Resonance (NMR)

and Fourier Transform Infrared spectroscopy (FT–IR) have proved the successful isolation of the amphiphilic benzene-1,3,5–tricarboxamide using column

chromatography to give 38% in yield as yellow oily liquid.

| Benzene-1,3,5-tricarboxamide | Supramolecular amphiphilic | Chemosensors | Nanosensors | Nitro anions |

® 2013 Ibnu Sina Institute. All rights reserved.

1. INTRODUCTION

Nanoporous silica such as silica nanoparticles,

microporous, and mesoporous materials have been

functionalized with organosilane bearing organic

chromophores using post-synthetic grafting and co-

condensation methods [1]. These two methods can be used

to develop different kinds of chemsensors by tuning the

functional groups according to the types of analytes [1-3].

However, the main drawbacks of both methods are non-

homogeneous distribution of chromophores in the silica

wall or surface [4-5] and low loadings volume of

chromophores which will significantly reduce the

performance of nanosensors. Since the pioneering work

reported by Aida and Tajima [6], Brinker et al. [7] and

Kimura et al. [8] in 2001, where they have independently

found functional amphiphiles as templates for the sol–gel

synthesis of mesoporous silica, a variety of organic

functionalities can be densely incorporated into the

hexagonal silicate nanochannels.

Recently, Lintang et al. in 2010 have reported that

trinuclear gold(I) pyrazolate complex has been used as an

amphiphilic surfactant for templating the sol–gel synthesis

of mesoporous silica. The resulting mesoporous silica

composite contains long–range one dimensional (1D)

columnar assembly of gold(I) pyrazolate complex in the

silicate nanochannels [9]. This thin film of nanocomposite

has been used for sensing of Ag+ into the channel of

mesoporous silica by utilizing weak Au(I)-Au(I)

metallophilic interaction for color change from red to

green due to formation of Au(I)-Ag(I) heterometallic

interaction [11]. On the other hand, development of high

performance sensor for nitrite and nitrate anions has been

a subject of intense research interest due to their

carcinogenic agents to effect human health and pollutants

in environments [10]. Here we report the synthesis of

benzene–1,3,5–tricarboxamide bearing amphiphilic amino

decoxy triethylene glycol side chains that will self-

assemble to dense filling in the silica nanochannel.

Moreover, the

synthesized amphiphilic version of benzene–1,3,5–

tricarboxamide can be utilized for the formation of

columnar assembly via the weak hydrogen bonding

interaction and used it as a specific receptor for detection

of nitro anions. Nevertheless, the amphiphilic benzene–

1,3,5–tricarboxamide can be used as a tuneable functional

template in the sol-gel synthesis of mesoporous silica to

give novel chemosensor nanocomposites. Therefore, this

is a novel example to utilize hydrogen bonding as a weak

non-covalent supramolecular interaction in the channel of

mesoporous silica for mesoporous for sensing of nitrite

and nitrate anions.

2. EXPERIMENTAL 2.2 Characterizations

Bruker Ultra ShieldTM

model proton (1H–) NMR

300 MHz and carbon (13

C–) NMR 75 MHz with its spectra

were recorded in chloroform (CDCl3) where chemical

shifts were determined with respect to non–deuterated

residue chloroform (CHCl3) at δ of 7.24 ppm for 1H–NMR

spectroscopy and at δ of 77.0 ppm for 13

C–NMR

spectroscopy as internal standards. FT–IR spectra were

recorded on NICOLET iS50, Thermo Scientific using

Nujol mull and KBr for method preparations depending on

sample conditions. Mass spectra were recorded on a AB

Sciex MALDI- TOF/TOF™ 5800 Spectrometry system

PROCEEDING OF 4TH ICOWOBAS-RAFSS 2013

4th ICOWOBAS-RAFSS 2013

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with ion positive ionization and reflection mode. Dithranol

(1,8,9- antracenetriol) was used as a matrix in CHCl3.

2.3 1-Aminodecoxy triethylene glycol (2)

1’-(2-(2-(2-methoxyethoxy)ethoxy) ethoxy)-10-

phthalamide decane (1). Amphiphilic 1 was synthesized

via Gabriel synthesis under Mitsunobu condition [12]

from the mixture of 10’-(2-(2-(2 methoxyethoxy)ethoxy)

ethoxy) decan-1-ol precursor as-synthesized according to

literature [8] and phthalamide. Dry THF (180 mL) was

added to this mixture of phthalamide (8.1 g, 20.0 mmol)

and triphenylphosphine (PPh3; 12.6 g, 24.0 mmol) in two

neck round–bottom flask under inert condition until

completely dissolved and followed by the addition of

diisopropyl azodicarboxylate (DIAD; 25.8 mL) in 40%

dry toluene at 0 ºC. Finally, 10’-(2-(2-(2

methoxyethoxy)ethoxy) ethoxy) decan-1-ol (12.8 g, 20.0

mmol) was added using syringe and the mixture was

allowed to react for 12 hours in room temperature. The

reaction was monitored by thin layer chromatography

(TLC) plate using hexane/ ethyl acetate (Hex/ AcOEt)

(1:1) before quenching with dry ethanol (EtOH; 80 mL)

and then evaporated. Afterwards, addition of 40 mL Hex/

AcOEt (1:1) was needed to promote white suspension. At

this point, the mixture was heated to 40 ºC with constant

stirring for 1 hour. The mixture was filtered off from

insoluble substances and evaporated to dryness. The

residue was chromatographed on silica gel with AcOEt/

Hex (40:1) as an eluent. The third fraction was collected,

evaporated to dryness and dried under reduce pressure to

give 1’-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-10-

phthalamide decane (1) as a yellow transparent oily

substance in 80% yield (7.4 g, 16.0 mmol). NMR δH

(CDCl3) ppm: 7.81-7.78 (m, 2H, ArH), 7.71-7.61 (m, 2H,

ArH), 3.64-3.51 (m, 14H, -OCH2CH2),), 3.43-3.39 (t, 2H,

-OCH2), 3.35 (s, 3H, -OCH3), 1.65-1.26 (m, 16H, -(CH2)8-

); NMR δC (CDCl3) ppm: 168.12, 131.99-133.58, 122.86,

71.22-69.83, 60.04, 58.66, 37.77, 33.55-28.32; IR νmax

(nujol) cm-1: 2853, 1773, 1719, 1460, 1376, 1113, 721;

MS: m/z 472 [M+Na+, C25H39NO6].

1–aminodecoxy triethylene glycol (2). Compound

2 was synthesized via Gabriel synthesis in the presence of

hydrazine monohydrate and followed by acid work–up

[13]. Firstly, 2 (7.4 g, 16.0 mmol) and hydrazine

monohydrate (90 μL, 18.4 mmol) were added to a 3 neck

round–bottom flask, fitted with a condenser and anhydrous

CaCl2 tube, containing of extra dry ethanol (EtOH; 50

mg), and the reaction mixture was refluxed for 5 hours

under inert nitrogen (N2) condition. The resulting mixture

was allowed to cool down to room temperature, before

drop wise addition of concentrated hydrochloric acid

(HCl; 3.5 mL) to form more white precipitate, and reflux it

further for 1 hour. The mixture was then filtered off from

insoluble substances, and evaporated to dryness, before

adding 30 mL of double distilled water. Basic work–up by

using sodium hydroxide (NaOH; 1 N) was carried out by

maintaning the mixture at pH 11. The residue was then

subjected to column chromatography with CHCl3/

Methanol (MeOH) (40:1) as an eluent. The third fraction

was collected and evaporated to dryness under reduce

pressure to give 1–aminodecoxy triethylene glycol (2) as a

yellow oily gel like-liquid in 78% yield (4.0 g, 12.5

mmol). NMR δH (CDCl3) ppm: 3.64-3.51 (m, 12H,

OCH2CH2), 3.43-3.39 (t, 2H, -OCH2), 3.11 (s, 3H, -

OCH3), 2.95 (m, 2H, NH2CH2-) 1.77-1.25 (m, 16H, -

(CH2)8-); NMR δC (CDCl3) ppm: 71.74-69.84, 58.85,

39.92 (a), 29.42-29.15, 28.84, 27.47, 26.42, 25.87; IR νmax

(nujol) cm-1: 2852, 1917, 1461, 1376, 1302, 1214, 1200,

1115, 907, 760, 735; MS: m/z 342 [M+Na+, C17H37NO4].

2.4 Benzene-1,3,5-tricarboxamide (3)

Amphiphilic benzene–1,3,5–tricarboxamide (3).

Compound 3 was synthesized by Schotten-Baumann

amidation reaction [14] using 2 and 1,3,5–

benzenetricarbonyl trichloride. In this reaction, 2 (1.32 g,

3.98 mmol) was vacuum for 15 minutes before replace air

by purified N2 gas and before 1,3,5–benzenetricarbonyl

trichloride (0.36 g, 1.37 mmol) was added. The mixture

was added and dissolved with dry THF (20 mL) before dry

distilled triethylamine (1.66 mL, 11.94 mmol) was added

using syringe. The reaction was left to stir homogently

under inert condition at room temperature for overnight.

The resulting mixture was washed consecutively with

acetone (5 mL), double distilled water (50 mL), and

MeOH (10 mL) before purified using silica

chromatography. The desired product was successfully

isolated from silica column with CHCl3/ MeOH (50:1) as

eluent and then evaporated and dried under reduce

pressure by using vacuum pump under reduce pressure at

room temperature to give benzene–1,3,5–tricarboxamide

(3) which is yellow oily liquid in 38% yield (0.58 g, 0.52

mmol). NMR δH (CDCl3) ppm:1.64-1.24 (31H, CH2CH2-

C7H14-CH2CH3), 1.67-1.53 (13H, CH2CH2-C7H14-

CH2CH3), 3.64-3.51 (45H, -OCH2CH2-), 3.43-3.34 (3H, -

OCH2-), 3.11 (s, 3H, -OCH3), 8.35 (s, 3H, Ar-H). IR νmax

(nujol) cm-1: 3554, 2926, 2854, 1725, 1654, 1540, 1459,

1376, 1289, 1199, 1111, 944, 851, 722; MS: m/z 1151

[M+Na+, C61H113N3O5].

3. RESULTS & DISCUSSION

3.1 1Aminodecoxy triethylene glycol (2)

Scheme 1 illustrates the detailed synthetic route of

(3). There are three stepwise reactions in order to synthesize

3 from 10’-(2-(2-(2 methoxyethoxy)ethoxy) ethoxy) decan-

1-ol with phthalamide via Mitsunobu reaction followed by

Gabriel synthesis with hydrazine and finally reacted with

4th ICOWOBAS-RAFSS 2013

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benzenetricarbonyl trichloride via Schotten-Baumann

amidation reaction respectively. 1–Aminodecoxy triethylene

glycol (2) was prepared from cleaved reaction of 1’-(2-(2-

(2-methoxyethoxy)ethoxy) ethoxy)-10-phthalamide decane

(1) by hydrazine. 1H–NMR spectra of 2 in Fig. 1a showed

absence of chemical shift at 7.81-7.78 (m, 2H, ArH) for

phthalamide groups and at 7.71-7.61 (m, 2H, ArH) for

benzene ring. The shifting of chemical shift to upfield signal

shift from from 3.11 ppm to 2.85 in Fig. 1a for proton

adjacent to amino group (–NH2) also indicate the successful

cleavage of phthalamide group. The results were in good

agreement with 13

C–NMR spectra by disappearance of

chemical shift at 131.98 ppm for cyclic carbon structure and

168.12 ppm for carbonyl of phthalamide group. In addition,

IR spectra of 1–aminodecoxy triethylene glycol did not

show any vibrational bands at both 1460 and 1376 cm-1

which are contributed by aromatic rings stretch of

phthalamide group. The successful synthesis of 2 was also

supported by mass spectrum of C17H37NO4 and molecular

weight [ M+Na+] of 342 (Cald.:319.27 for [M

+]).

.

3.2 Benzene-1,3,5-tricarboxamide (3)

Fig. 1 showed 1H–NMR spectra of the reactants; 1–

aminodecoxy triethylene glycol (2) in Fig. 1a and 1,3,5–

benzenetricarbonyl trichloride in Fig. 1b as well as the

desired product of benzene–1,3,5–tricarboxamide (3) in

Fig. 1c. Benzene–1,3,5–tricarboxamide was synthesized

from amidation reaction under basic condition via Schotten-

Baumann reaction. In this reaction, triethylamine was used

as base to drive the equilibrium in the formation of amides

from amines and acid chlorides. The chemical shift of 1–

amino decoxy triethylene glycol at initial 2.96 ppm (t, 2H,

Ha = NH2CH2-) in Fig. 1a was shifted to 3.36 ppm (3H, Ha

= -NHCH2-) which overlapped with 3.34-3.43 (m, 3H, -

OCH2-) in compound 3 of Fig. 1c due to successful bonding

of amino to carbonyl to form carboxamide group. The

bonding formation was supported by vibration bands at

1199 cm-1 in Fig. 2c attributed to C-N of carbonyl to amide

which was not appear in 1–aminodecoxy triethylene glycol

(2). Moreover, the chemical shift of 1,3,5–

benzenetricarbonyl trichloride from 8.95 ppm in Fig. 1b

was shifted to 8.35 ppm (s, 3H, He = Ar-H) in Fig. 1c of 3,

indicating attachment of benzene ring to alkyl amide

chains. Nevertheless, the increasing numbers of proton to

three times are significant characteristic for the successful

trisubstituted benzene ring with 1–aminodecoxy triethylene

glycol (2) in Fig. 1c at 1.67-1.24 ppm (45H, Hb = -CH2-

(CH2)10-CH3) and 3.64-3.51 ppm (45H, -OCH2CH2-).

1,3,5-Benzene tricarbonyl trichloride

Triethly amine

THF

RT, 18 hours

STEP 3

HOO

OO

O

PPh3

DIAD

RT,12 hoursTHF,

Phthalamide

1) N2H4 . H2O, 5 hours

2) conc. HCl aq, 1 hours

EtOH refluxN

OO

OO

H

H

STEP 1

STEP 2

2

1

N

O

O

OO

OO

O N

O

H

O

O

O

O

N O

NH

H

O

OO

OO

O

O

O

3

+

N

O

O

H

10'-(2-(2-(2 methoxyethoxy)ethoxy) ethoxy) decan-1-ol

Scheme 1 Synthetic scheme of Benzene–1,3,5, –tricarboxamide (3).

4th ICOWOBAS-RAFSS 2013

24

The 1H–NMR spectra was in good agreement with

the IR spectra as in Fig. 2 that showed vibration spectra for

(a) 1-aminodecoxy triethylene (in nujol), (b) 1,3,5–

benzenetricarbonly chloride (in KBr), and (c) benzene–

1,3,5–tricarboxamide liquid (in nujol). The IR spectrum for

1,3,5–benzenetricarbonyl chloride in Fig. 2b shows

prominent vibration bands at finger print region from 1000

to 1500 cm-1 which indicate lacks of long alkyl chains

presence as supported by only singlet of the benzene ring

with chemical shift for 1H–NMR spectra in Fig. 2b at 9.08.

Moreover, both strong vibrational peaks at 1467 and 1508

cm-1 are characteristic for stretching of benzene. On the

other hand, a vibrational band of 1–aminodecoxy

triethylene glycol in Fig. 2a showed strong vibration peak

at 2852 cm-1 due to stretching of alkyl. In addition, the

desired product of benzene-1,3,5-tricarboxamide (3) in Fig.

2c shows prominent peaks at 2926 and 2854 cm-1 attributed

to stretching of symmetric and asymmetric alkyl

respectively, while peaks at 1540 and 1459 cm-1 are due to

present of aromatic ring group. The presence of benzene

ring in 3 was supported by single downfield chemical shift

at 8.95 by 1H–NMR spectra in Fig. 2c. The successful

synthesis of 3 was also strongly supported by mass

spectrum of C61H113N3O5 and molecular weight [M+Na+] of

1151 (Cald.:1127.82 for [M+]).

a

a)

N

O

O

O

O

H

H

Ha

Hb

Hc

Hd

11 10 9 8 7 6 5 4 3 2 1 ppm

7.239

9.064

3.00

NAME Juan-Hendrik-Trimesoyl chloride(std3)-CDCl3

EXPNO 1

PROCNO 1

Date_ 20130515

Time 15.28

INSTRUM spect

PROBHD 5 mm PABBO BB-

PULPROG zg30

TD 65536

SOLVENT CDCl3

NS 16

DS 2

SWH 8223.685 Hz

FIDRES 0.125483 Hz

AQ 3.9846387 sec

RG 406

DW 60.800 usec

DE 6.50 usec

TE 300.0 K

D1 1.00000000 sec

TD0 1

======== CHANNEL f1 ========

NUC1 1H

P1 6.00 usec

PL1 -6.00 dB

SFO1 400.1324710 MHz

SI 32768

SF 400.1300183 MHz

WDW EM

SSB 0

LB 0.30 Hz

GB 0

PC 1.00

9.05 ppm

9.064

3.000

O

O

O

Cl Cl

Cl

HeHe

He

b)

He Hc Hd Ha Hb

He

c)

Hc

Ha

Hb

O N

O

H

O

O

O

O

N O

NH

H

R

R

Ha

Hb

Hc

Hd

He

He He

Fig. 1 1H-NMR spectra of (a) 1–aminodecoxy triethylene glycol (2), (b) 1,3,5–benzenetricarbonyl trichloride, and (c) Benzene–1,3,5–

tricarboxamide (3) using CDCl3 as a solvent.

4th ICOWOBAS-RAFSS 2013

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4. CONCLUSION

Amphiphilic benzene–1,3,5–tricarboxamide (3) as

yellow oily liquid in 38% yield (0.58 g, 0.52 mmol) was

successfully synthesized by using 1–aminodecoxy

triethylene glycol (2) and 1,3,5–benzenetricarbonyl

trichloride undergoes Schotten-Baumann amidation

reaction. This amphiphilic benzene–1,3,5–tricarboxamide

(3) will be used as a surfactant in the sol-gel synthesis to

form mesoporous silica nanocomposites and then will be

used to evaluate the chemosensor performance towards

nitro anions.

ACKNOWLEDGEMENT

The authors thank the Department of Chemistry,

Faculty of Science and Ibnu Sina Institute, Universiti

Teknologi Malaysia, Johor for facilities as well as to

Ministry of Higher Education (MOHE) through

Research University Grant Scheme (Flagship 2011, Vote

No. J130000.2426.00G07) and Fundamental Research

Grant Scheme (FRGS, Vote No. J130000.7809.4F194),

Malaysia for the financial support. Juan Matmin also

acknowledges the financial support from MOHE through

MyPhD Postgraduate Scholarship.

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[2] F Mancin, E. Rampazzo, P. Tecilla, and U. Tonellato, Chem. A Euro. J., 12 (2006) 1844–1854.

[3] J.B. Melde, J.B. Johnson, and T.P. Charles, Sensors, 8 (2008)

5202–5228. [4] L. Zhang, T. Sun, and J.Y. Ying, Chem. Comm., 12 (1999)

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[5] W.X. Xiao, D. Xiao, J. Xia, and Z. Chen, Microchim. Act., 173 (2011) 73–78.

[6] T. Aida, and K. Tajima, Angew. Chem. Int. Ed., 40 (2001) 3803–3806.

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[10] M.G. Almeida, A. Serra, C.M. Silveira, and J.J.G. Moura, Sensors, 10 (2010) 11530–11555.

[11] H.O. Lintang, K. Kinbara, K. Tanaka, T. Yamashita, and T.

Aida, Chem. Asian J., 7 (2012) 2068–2072. [12] O. Mitsunobu and M. Yamada, Bull. Chem. Soc. Jap., 40 (1967)

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1000200030004000

Fig. 2 FTIR spectra of (a) 1-aminodecoxy triethylene glycol (2), (b) 1,3,5-benzenetricarbonyl trichloride, and (c) Benzene-1,3,5-tricarboxamide (3).

4th ICOWOBAS-RAFSS 2013

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