Electrochemical saccharide recognition by a phenylboronic acid-terminated redox active self-assembled monolayer on a gold electrode

Article abstract of DOI:10.1246/cl.2000.940

Phenylboronic acid-terminated viologen-carrying alkyl disulfide (1) and a reference compound 2 were designed and synthesized. Self-assembled monolayers of 1 on gold electrodes were found to function as a highly sensitive saccharide sensor in aqueous solut

Full text of DOI:10.1246/cl.2000.940

940
Chemistry Letters 2000
Electrochemical Saccharide Recognition by a Phenylboronic Acid-Terminated
Redox Active Self-Assembled Monolayer on a Gold Electrode
Hiroto Murakami, Hiromi Akiyoshi, Takanari Wakamatsu, Takamasa Sagara, and Naotoshi Nakashima*
Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, 1-14 Bunkyo, Nagasaki 852-8521
(Received May 8, 2000; CL-000432)
Phenylboronic acid-terminated viologen-carrying alkyl
A mirror-polished polycrystalline gold disk electrode (BAS
Co., geometrical area: 2.01 mm2) was immersed in 1.0 mmol
dm–3 of 1 (or 2) in methanol for 24 h and then rinsed with
methanol and then with 0.1 mol dm–3 potassium hexafluo-
rophosphate aqueous solution. Cyclic voltammogram (CV)
measurements (BAS-100BW) for the obtained electrodes (1-
SAM/Au and 2-SAM/Au) were carried out in 0.1 mol dm–3
potassium hexafluorophosphate aqueous solution (pH 10.5)
containing given concentration of a saccharide at 23 1 °C in
argon atmosphere using a gold wire and a saturated calomel
electrode (SCE) as the counter and the reference electrodes,
respectively.
Typical CVs for a 1-SAM/Au electrode is shown in Figure
1. A 2-SAM/Au electrode gave similar CVs (data not shown).
The formal potentials for the first reduction/reoxidation of the
viologen moiety in 1 and 2 obtained from the CVs were –495
and –500 mV, respectively. Both cathodic and anodic peak
current of the CVs for 1-SAM/Au (Figure 1) and for 2-
SAM/Au (data not shown) at a scan range of 25–200 mV/s
increased linearly with the increase of scan rates, indicating that
the electron transfer of the surface confined species with the
electrode governs the electrochemistry. The surface coverage
of 1 and 2 calculated from the CVs were (1.3 0.2) × 10–10 and
(1.4 0.2) × 10–10 mol cm–2, respectively.8
disulfide (1) and a reference compound 2 were designed and
synthesized. Self-assembled monolayers of 1 on gold elec-
trodes were found to function as a highly sensitive saccharide
sensor in aqueous solution.
The interaction of phenylboronic acids and compounds
with vic-diols can be detectable in water by several methods
including fluorescence spectroscopy1 and an electrochemical
technique2. Our goal is to design and construct self-assembled
monolayers of a phenylboronic acid-carrying electroactive
compound on an electrode that performs electrochemical com-
munication with saccharides in aqueous solution. For this pur-
pose, we synthesized 1,1"-(dithiodi-6,1-hexanediyl)bis[1'-(4-
dihydroxyboryl)phenylmethyl-4,4'-bipiridinium] tetrakis(hexa-
fluorophosphate) (1). Recently, Olliff and co-workers3 pre-
pared a self-assembled monolayer (SAM) of a phenylboronic
acid-terminated alkanethiol on a gold electrode and examined
the response to nicotinamide adenine dinucleotide by means of
surface plasmon resonance measurements. Kitano and co-
workers4 described sugar recognition by a phenylboronic acid-
carrying SAM on a gold colloid or a gold electrode detected,
respectively, by UV–vis absorption change and by cyclic
voltammetry using an electroactive marker. Here we describe
first electrochemical saccharide sensing with a redox active
phenylboronic acid-terminated SAM on a gold electrode.
The synthesis of 1 is as follows. 4-(1,3-Dioxa-2-boranyl)
benzyl bromide5 was reacted with 4,4'-bipyridyl in CH3CN at
refluxed temperature for 13 h to produce 4-(4-pyridyl)-N-(4-
(1,3-dioxa-2-boranyl)benzyl)pyridinium bromide, which was
reacted with 6-thiobenzoyloxy-1-bromohexane in DMF at 60
˚C for 48 h, followed by hydrolysis with concd HCl and then
ion exchange with potassium hexafluorophosphate. Compound
16 was obtained as a white solid. 1,1"-(Dithiodi-6,1-hexa-
nediyl)bis(1'-benzyl-4,4'-bipiridinium) tetrakis(hexafluorophos-
phate), 27, a reference compound of 1, was synthesized by a
similar procedure.
Figure 2 shows CVs for a 1-SAM/Au in the absence or
presence of 0.1 mol dm–3 xylose in aqueous solution. The pres-
ence of xylose causes the shift of the formal potential to nega-
tive direction by 18 mV. This shift might be explained by the
Copyright © 2000 The Chemical Society of Japan

Chemistry Letters 2000
941
methylglucoside. iii) The electrode had a response to methyl-β-
xylopyranoside, a compound that has no binding site with
phenylboronic acid, at the relatively higher concentrations.
Possible hydrogen bonding between the phenylboronic acid
moiety in 1 with the 2,3-and 4-hydroxy moieties in methyl-β-
xylopyranoside may explain the shift.
In conclusion, we have found, for the first time, that
phenylboronic acid-terminated redox active SAMs on gold
electrodes respond to a variety of saccharides at relatively low
concentration (ppm order). Intense effort is currently underway
in our laboratory to reveal fully the characteristics of 1-
SAMs/Au electrodes including the mechanism of the observed
potential shift in the CVs and explore potential applications of
the electrodes as highly sensitive sensors for biological oligo-
and poly(saccharides).
This work was supported in part by the Nagasaki
Advanced Technology Development Council (for H. M.).
References and Notes
1
a) S. Shinkai and M. Takeuchi, NATO ASI Ser., Ser. C,
527, 157 (1999). b) T. D. James, K. R. A. Samankumara
Sandanayake, and S. Shinkai, Angew. Chem., Int. Ed.
Engl., 35, 1911 (1996).
stronger binding of the saccharide with the oxidized form of 1
than the reduced form. On the contrary, no such shift in the for-
mal potential was observed for a 2-SAM/Au electrode. CVs at
1-SAM/Au electrodes were measured in the presence of given
concentrations of galactose, fructose, mannose, glucose, xylose,
α-methylglucoside and methyl-β-xylopyranoside, and the
observed shifts in E0’ were plotted as a function of saccharide
concentration in Figure 3. Interesting features observed are as
follows. i) 1-SAM/Au electrodes exhibited a response for
xylose, mannose and fructose at the concentration range of
10–6–10–3 mol dm–3. ii) CV response of the electrode was also
occurred to α-methylglucoside, a compound possessing no 1,2-
diol moiety. This might be due to the binding of the phenyl-
boronic acid moiety in 1 with the 4- and 6-hydroxy groups in α-
2
3
a) A. Ori and S. Shinkai, J. Chem. Soc., Chem. Commun.,
1995, 1771. b) N. J. Moore and D. D. M. Wayner, Can. J.
Chem., 77, 681 (1999).
K. D. Pavey, C. J. Olliff, J. Baker, and F. Paul, Chem.
Commun., 1999, 2223.
N. Kanayama and H. Kitano, Langmuir, 16, 577 (2000).
S. Arimori, H. Murakami, M. Takeuchi, and S. Shinkai, J.
Chem. Soc., Chem. Commun., 1995, 961.
mp >300 ˚C. Anal. Found: C, 40.10; H, 4.01; N, 4.02%.
Calcd for C46H56N4O4B2F24P4S2: C, 39.6; H, 4.04; N,
4.02%. IR (KBr): 3400 (OH), 3058 (CH, Ar), and 2942
(CH) cm–1. 1H NMR (200 MHz, CD3CN, TMS); δ 1.3–1.8
(m, 16H, SC(CH2)4CN+), 2.70 (m, 4H, SCH2), 4.60 (t, 4H,
CH2N+), 5.84 (s, 4H, N+CH2Ph), 6.43 (s, 4H, OH), 7.49
(d, 4H, ArH), 7.88 (d, 4H, ArH), 8.37 (m, 8H, PyH), 8.89
(d, 4H, PyH), 8.98 (d, 4H, PyH).
4
5
6
7
mp >300 °C. Anal. Found: C, 38.93; H, 4.31; N, 4.41%.
Calcd for C46H54N4F24P4S2·5.7H2O: C, 39.19; H, 4.68;
N,3.97%. IR (KBr): 3139 (CH, Ar), and 2931 (CH) cm–1.
1H NMR (200 MHz, DMSO-d6, TMS); δ 1.30 (m, 8H, SC2
(CH2)2C2N+), 1.63 (m, 4H, SCCH2C4N+), 1.95 (m, 4H,
SC4CH2CN+), 2.70 (m, 4H, SCH2), 4.65 (t, 4H, CH2N+),
5.94 (s, 4H, N+CH2Ph), 7.47 (d, 6H, ArH), 7.61 (d, 4H,
ArH), 8.75 (m, 8H, PyH), 9.36 (d, 4H, PyH), 9.52 (d, 4H,
PyH).
8
The surface roughness factor determined by the anodic oxi-
dation of chemisorbed iodine on bare Au electrodes was
ca. 1.4, whose value was used to calculate the surface cov-
erage. Detailed for the anodic oxidation of chemisorbed
iodine, see: J. F. Rodriguez, T. Mebrahtu, and M. P.
Soriaga, J. Electroanal. Chem., 233, 283 (1987).