Kass-controlled Hg2+ transport from Crystal Violet Lactone to Fluoran

Article abstract of DOI:10.1016/j.dyepig.2011.07.017

We have investigated the Hg²⁺ transport from Crystal Violet Lactone to Fluoran dye based on the association constant, K_ass. Upon addition of Hg²⁺, the Crystal Violet Lactone shows a new peak at around 603 nm, and the color of the solution changed from colorless to blue. With the addition of Fluoran dye in this solution containing Crystal Violet Lactone and Hg²⁺, the absorption intensity of Fluoran dye at 447 nm and 586 nm was all increased. So the color of solution gradually became black from blue color. From the changes of the ratio A₅₈₆/A₄₄₇, it is apparent that the Hg²⁺ in Crystal Violet Lactone-Hg ²⁺ was transported to colored Fluoran. The Hg²⁺ transport from Crystal Violet Lactone to Fluoran dye was also carried out by the calculation of the association constant: the binding ability for the complex formation of Fluoran dye and Crystal Violet Lactone-Hg²⁺ is much greater in CH₃CN solution (K_ass = 3.0 × 10 ⁴ M^-1) than that of the Crystal Violet Lactone with Hg²⁺ (K_ass = 1.2 × 10³ M^-1).

Full text of DOI:10.1016/j.dyepig.2011.07.017

Dyes and Pigments 92 (2012) 1058e1061
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Kass-controlled Hg2þ transport from Crystal Violet Lactone to Fluoran
,b,
Eun-Mi Lee a, Seon-Yeong Gwon a, Byung-Chul Ji a, Sung-Hoon Kim a
*
a Department of Advanced Organic Materials Science and Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea
b School of Chemistry Science & Technology, Zhanjiang Normal University, Zhanjiang 524048, PR China
a r t i c l e i n f o
a b s t r a c t
We have investigated the Hg2þ transport from Crystal Violet Lactone to Fluoran dye based on the
association constant, Kass. Upon addition of Hg2þ, the Crystal Violet Lactone shows a new peak at around
603 nm, and the color of the solution changed from colorless to blue. With the addition of Fluoran dye in
this solution containing Crystal Violet Lactone and Hg2þ, the absorption intensity of Fluoran dye at
447 nm and 586 nm was all increased. So the color of solution gradually became black from blue color.
From the changes of the ratio A586/A447, it is apparent that the Hg2þ in Crystal Violet LactoneeHg2þ was
transported to colored Fluoran. The Hg2þ transport from Crystal Violet Lactone to Fluoran dye was also
carried out by the calculation of the association constant: the binding ability for the complex formation
Article history:
Received 19 April 2011
Received in revised form
3 June 2011
Accepted 26 July 2011
Available online 8 August 2011
Keywords:
Ion transport
of Fluoran dye and Crystal Violet LactoneeHg2þ is much greater in CH3CN solution (Kass ¼ 3.0 ꢀ 104 Mꢁ1
)
Crystal violet lactone (CVL)
Fluoran
than that of the Crystal Violet Lactone with Hg2þ (Kass ¼ 1.2 ꢀ 103
M
ꢁ1).
Hg2þ sensing
Ó 2011 Elsevier Ltd. All rights reserved.
One dye black (ODB)
Association constant (Kass
)
1. Introduction
CVL shows bluish violet (lmax ¼ 603 nm), but is not fast to light. Oda’s
group observed a significant increase in the photostability of CVL by
adding of various counterions [8,9]. Our group recently reported the
ionochromic properties of CVL with metal cations [10]. It shows
a good selectivity and sensitivity for Hg2þ. Fluoran dyes are well
known as leuco dyes or colored cationic dyes for thermosensitive
recording papers and have equilibrium between the colorless lactone
form and the colored zwitterion form. The colored form of Fluoran
has two distinctive absorption maxima in visible region. The two
colors are complementary, and fortunately the two absorption
maxima are nearly the same in absorbancy. As a result, a black hue
can be obtained by the use of only one chromophore. That’s why this
compound is called One Dye Black (ODB). A new chromogenic che-
mosensor based on Fluoran derivatives was developed by Kim et al.
[11,12]. It shows an extreme selectivity for Fe2þ and Fe3þ. The ion
transport process plays an important role in the hosteguest chem-
istry and molecular-level machine, the transfer of a guest ion from
one host to another [13,14]. In the present paper, we demonstrate the
active Hg2þ transport mediated by CVL and ODB system based on the
The leuco triphenylmethanes are generally stable substance. The
formation of colored materials from leuco bases such as Crystal Violet
Lactone (CVL) and Fluoran is accomplished by treatment with acids
such as acid clay, bisphenol A, acetic acid, or silicagel. CVL is one of
most important phthalide dyes and extensively used in the pressure-
sensitive or the carbonless copy as color formers and other digital
printing outlet [1]. The process of the color formation using CVL
consists of a ground-state dissociation of the CeO bond in the lactone
ring (in the presence of a proton donor) resulting in the formation of
the Crystal Violet cation [2]. The lability of the CeO bond under
various influences makes CVL very attractive for various applications,
such as a photopolymerization initiator [3,4] and the active ingre-
dient in thermochromic coatings [5,6]. Although there are wide-
spread uses of CVL, only a few studies have been carried out toward
understanding the fundamental photophysics and the photochem-
istry of CVL and other phthalide-based color formers. The existing
reports [7] give, however, incomplete or even misleading [3] insights
into CVL spectroscopy. Therefore, fundamental studies on the pho-
tophysical properties of CVL and its derivatives are still crucial for the
exploration of new functions and applications in CVL dye chemistry.
absorption titration and the value of the association constant, Kass
.
2. Experimental
2.1. General
* Corresponding author. Department of Advanced Organic Materials Science and
Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea.
Tel.: þ82 53 950 5641; fax: þ82 53 950 6617.
CVL was purchased from Aldrich. The other chemicals were of
the highest grade available and were used without further
E-mail address: shokim@knu.ac.kr (S.-H. Kim).
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.07.017

E.-M. Lee et al. / Dyes and Pigments 92 (2012) 1058e1061
1059
purification. Absorption spectra were recorded on Agilent 8457
UVevis spectrophotometer using 1-cm quartz cell. Mass spectra
1.0
0.8
0.6
0.4
0.2
0.0
a
were recorded on a Shimadzu QP-1000 spectrometer using elec-
tron energy of 70 eV and the direct probe EI method. 1H NMR, 13
C
3 eq.
NMR spectra were recorded using a Varian Inova 400 MHz FT-NMR
spectrometer with TMS as internal standard. Spectroscopic titra-
tions were carried out according to the literature [10e12].
2+
0 [Hg ]
2.2. Determination of binding ratio and association constant
In our present experiments, Hg(ClO4)2 was gradually added into
the solution of CVL as a mercury source, and the coordination
abilities of CVL with Hg2þ were investigated by UVevis spectros-
copy. The binding stoichiometry of CVL with Hg2þ ions was deter-
mined by using Job plot [15,16] according to the method of
continuous variations. For Job plot analysis, a series of solutions with
varying mole fraction of Hg2þ were prepared by maintaining the
total CVL and Hg2þ ion concentration constant (1 ꢀ 10ꢁ4 molLꢁ1),
and the molar fraction of Hg2þ varied from 0.0 to 1.0. The association
constant (Kass) of CVLeHg2þ and CVLeHg2þeODB were calculated
by the linear BenesieHildebrand expression [15,16] with the good
linear correlation coefficient (R ¼ 0.9934 for CVLeHg2þ and 0.9980
for CVLeHg2þeODB) as shown in Fig. 2.
450
500
550
600
650
700
Wavelength(nm)
0.6
0.5
0.4
0.3
0.2
0.1
0.0
b
2.3. Synthesis of ODB (Scheme1)
ODB was synthesized according to the litþerature method [17].
Yield: 58%, m.p. 187 ꢂC; mass (m/z) 532(M ); 1H NMR (400 MHz,
DMSO-d6):
d
(ppm) 7.93 (d, J ¼ 7.56, 1H), 7.76 (t, J ¼ 7.56, 1H), 7.66
(t, J ¼ 7.36, 1H), 7.41 (s, 1H), 7.26 (t, J ¼ 7.84, 1H), 7.22(s, 1H), 6.99
(t, J ¼ 7.84, 2H), 6.62 (t, J ¼ 7.04, 1H), 6.55 (d, J ¼ 7.6, 2H), 6.49
(d, J ¼ 8.08, 2H), 6.43 (s, 1H), 6.41 (d, J ¼ 9.08, 1H), 3.25 (t, J ¼ 7.6,
4H), 2.21 (s, 3H), 2.07(s, 1H),1.48(m, 4H), 1.29(m, 4H), 0.87(t, 6H).
0.0
0.2
0.4
0.6
0.8
1.0
13C NMR (400 MHz, DMSO-d6):
d (ppm), 13.78, 17.84, 19.63,
[Hg2+] / [Hg2+]+[CVL]
28.86, 30.59, 49.89, 83.55, 96.98, 104.1, 108.5, 114.63, 116.99, 118.32,
118.53, 119.49, 123.92, 124.45, 126.24, 128.59, 128.77, 129.94, 134.92,
135.40, 136.85, 145.25, 146.58, 149.63, 152.43, 152.49, 168.66.
Fig. 1. (a) Changes in UVeVis spectra of CVL (1 ꢀ10ꢁ5 molLꢁ1 in CH3CN) upon addition
of Hg2þ. (b) Job plot of Hg2þ versus CVL ([Hg2þ] þ [CVL] ¼ 1 ꢀ 10ꢁ4 molLꢁ1).
3. Results and discussion
1
1
1
h
i
¼
þ
Upon addition of Hg2þ the CVL showed a new peak at around
603 nm in its absorption spectra, and the color of solution changed
from colorless to blue (Fig. 1).
KassðAmax ꢁ A0Þ Hg2þ
A ꢁ A0
Amax ꢁ A0
In this equation, A0 is the absorbance of CVL, A is the absorbance
obtained with Hg2þ, AN is the absorbance obtained with excess
amount of Hg2þ, Kass is the association constant (Mꢁ1), and [Hg2þ] is
the concentration of Hg2þ added (M). According to the linear Benesie
Hildebrand expression, the measured absorbance [1/(A ꢁ A0)] at
603 nmvaried as the function of 1/[Hg2þ] in a linear relationship. The
binding mode of CVL with Hg2þ from the results of absorption
titration spectra (Fig. 1) was 1:1 with the binding constant of
1.2 ꢀ 103 Mꢁ1 (error limits <10%) (Fig. 2(a)).
CVL showed a good selectivity for Hg2þ over the other metal
cations. No significant absorption intensity changes were observed
on the addition of Fe3þ, Cu2þ, Fe2þ and Al3þ, which makes it
promising application in Hg2þ sensor [10]. The stoichiometry and
association constant of the complex are established by use of the
BenesieHildebrand method [15,16]. When assuming a 1:1 associ-
ation between CVL and Hg2þ, the BenesieHildebrand expression is
given as follows:
O
COOH
N
O
CH3
H
N
H3CO
N
H
C4H9
O
N
OH
C
C4H9
O
1
2
ODB
Scheme 1.

1060
E.-M. Lee et al. / Dyes and Pigments 92 (2012) 1058e1061
2.5
5
4
3
2
1
0
a
A586
2 eq.
2.0
1.5
1.0
A447
0 [ODB]
Linear Regression:
y = A + B*x
y = 0.1774 + (1*E )*x
R = 0.9934
2+
CVL+Hg
-4
0.5
0.0
3
Kass = 1.2*10
300
400
500
600
700
0
10000
20000
30000
40000
50000
Wavelength(nm)
1 / [Hg2+]
Fig. 4. Changes in UVevis spectra of ODB (1 ꢀ10ꢁ5 molLꢁ1 in CH3CN) upon addition of
Hg2þ to the solution of CVLeHg2þ
.
b
1.5
1.0
0.5
0.0
The recognition between ODB and Hg2þ was investigated by
UVevis spectroscopy in the CH3CN solution. From the absorption
spectrum of ODB in the CH3CN solution, it was not found that an
absorption band appeared in visible region, ODB solution was
colorless. Fig. 3 shows the UVevis spectra of ODB (1.0 ꢀ 10ꢁ5 molLꢁ1
)
upon addition of Hg2þ, in CH3CN solution. Upon addition of Hg2þ, we
found new absorption bands appeared including the absorption at
wavelength peaked at 447 nm and 586 nm. The color changed from
colorless to black. The color of 447 nm is complementary to the color
of 586 nm. As a result, the black color hue can be obtained by use of
only one dye molecule.
Linear Regression:
y = A + B*x
-5
y = -0.3393 + (2.03 E )*x
R = 0.9980
4
Kass = 3.0 * 10
The Hg2þ transport ability of ODB containing CVL and Hg2þ was
investigated in the CH3CN solution (Fig. 4).
0
10000
20000
30000
40000
50000
Fig. 4 shows the absorption band at lmax ¼ 603 nm for solution
1 / [ODB]
containing CVL and Hg2þ
. While upon addition of ODB to
Fig. 2. BenesieHildebrand plot of (a) CVL with Hg2þ and (b) CVLeHg2þ with ODB
lmax ¼ 603 nm for (a) and 586 nm for (b), correlation coefficient; (a) R ¼ 0.9934, (b)
R ¼ 0.9980).
CVLeHg2þ
, we also found new absorption bands appeared
(
including the absorption at wavelength peaked at 447 and 586 nm,
which is similar to Fig. 3.
Direct evidence for the decoloration of CVL and the coloration of
ODB was obtained by plotting A586/A447 (Fig. 5). As the ODB
concentration increases, the ratio A586/A447 decreases, the solution
changing from blue to black solution. The A586/A447 reached to 1.1
which is similar value with the ratio A586/A447 of ODBeHg2þ
Job plot analysis of the UVevis titration carried out in CH3CN
revealed a maximum at 50% mole fraction, in accord with the
proposed 1:1 binding mode (Fig. 1(b)).
ODB was synthesized from 2-(4-(dibutylamino)-2-hydroxy
benzoyl) benzoic acid 1 and 4-methoxy-2-methyl-N-phenylben
zenamine 2 as starting materials using H2SO4 as catalyst (Scheme 1).
50
1.8
1.4
A586/A447 = 1.1
1.6
40
2 eq.
1.2
A586
1.4
A447
30
1.0
1.2
1.1
0.8
2+
0 [Hg ]
20
10
0
0.0
0.5
1.0
1.5
2.0
2.5
0.6
[ODB] / [CVL-Hg2+
]
0.4
0.2
0.0
1.1
0.0
0.5
1.0
1.5
2.0
2.5
300
400
500
600
700
[ODB] / [CVL-Hg2+]
Wavelength(nm)
Fig. 3. Changes in UVevis spectra of ODB (1 ꢀ 10ꢁ5 molLꢁ1 in CH3CN) upon addition
Fig. 5. Changes in absorption intensity ratio A586/A447 obtained from absorption
titration of ODB to CVLeHg2þ
of Hg2þ
.
.

E.-M. Lee et al. / Dyes and Pigments 92 (2012) 1058e1061
1061
Acknowledgments
This work was supported by Basic Science Research Program
through the National Research Foundation (NRF) grant funded by
the Korea government (MEST) (No. 2011-0001084). This research
was supported by a grant from the Fundamental R&D Program for
Core Technology of Materials funded by the Ministry of Knowledge
Economy, Republic of Korea (2010).
References
[1] NationalCash Register. 3,3-bis(4-dimethylaminophenyl)6-dimethylaminophenyl
phthalide. US Patent 2417897; 1945.
[2] White MA. The chemistry behind carbonless copy paper. Journal of Chemical
Education 1998;75:1119e20.
[3] Kaneko Y, Neckers DC. Simultaneous photoinduced color formation and
photoinitiated polymerization. Journal of Physical Chemistry A 1998;102:
5356e63.
[4] Nag AK. Photopolymerization of methyl methacrylate using crystal violet
lactoneenitrobenzene complex as initiator. Indian Journal of Chemistry,
Section A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical Chem-
istry 1994;33:658e60.
[5] Ma Y, Zhu B, Wu K. Preparation and solar reflectance spectra of chameleon-
type building coatings. Solar Energy 2001;70:417e22.
[6] Ma Y, Zhang X, Zhu B, Wu K. Research on reversible effects and mechanism
between the energy-absorbing and energy-reflecting states of chameleon-
type building coatings. Solar Energy 2002;72:511e20.
[7] Allen NS, Hughes N, Mahon P. Photochemical fading and photostabilization of
the crystal violet lactone color former system. Journal of Photochemistry
1987;37:379e90.
Fig. 6. Coloration and decoloration of CVL and ODB and their proposed Hg2þ ion
transport.
[8] Oda H, Kitao T. Contribution of counterions to the photofading of crystal violet
lactone and related colorants. Journal of the Society of Dyers and Colourists
1989;105:257e61.
[9] Oda H, Kitao T. Photostabilisation of colorants for imaging and data recording
systems: effect of metal carboxylates on the light fastness of colour formers.
Dyes and Pigments 1991;16:1e10.
[10] Wang S, Hwang IJ, Gwon SY, Kim SH. Ionochromism of crystal violet lactone
triggered by metal cations. Fibers and Polymers 2010;11:1198e200.
[11] Wang S, Gwon SY, Son YA, Matsumoto S, Hwang IJ, Kim SH. Highly selective
colorimetric signaling of iron cations based on fluoran dye. Molecular Crystals
and Liquid Crystals 2009;504:155e63.
[12] Wang S, Gwon SY, Kim SH. A highly selective and sensitive coloriletric che-
mosensor for Feþ2 based on fluoran dye. Spectrochimica Acta, Part A:
Molecular and Biomolecular Spectroscopy 2010;76:293e6.
[13] Echegoyen L, Kaifer AE, editors. Physical supramolecular chemistry. London:
Kluwer academic publishers; 1996.
binding up to 2 equiv of ODB. In order to understand the nature of
Hg2þ transport ability from CVL to ODB, as well as binding mode of
ODB with Hg2þ in the present system, the calculation of the asso-
ciation constant was carried out (Fig. 2(b)). From the absorption
titration the association constant of ODB in CH3CN with CVLeHg2þ
was calculated to be 3.0 ꢀ 104 Mꢁ1, showing the high affinity of ODB
than CVL for Hg2þ. It is apparent that the Hg2þ transport can be
rationalized on the basis of the Kass between CVLeHg2þ and
CVLeHg2þeODB. Fig. 6 shows the coloration and decoloration of
CVL and ODB and their proposed Hg2þ ion transport.
4. Conclusions
[14] Müller TJJ, Bunz UHF, editors. Functional organic materials. Weinheim: Wiley-
VCH; 2007.
In summary, the Hg2þ transport ability from CVL to ODB was
investigated based on the absorption titration and association
constant. By adding of ODB to the solution containing CVL and
Hg2þ, the color of the solution changed from blue to black. As the
ODB concentration increases, the ratio A586/A447 decreases to 1.1
[15] Kim HJ, Park JE, Choi MG, Ahn S, Chang SK. Selective chromogenic and fluo-
genic signaling of Hg2þ ions using a fluorescein-coumarin conjugate. Dyes and
Pigments 2010;84:54e8.
[16] Jadhav JR, Bae CH, Kim HS. Fluorescence sensing of H2POꢁ4 by a imidazolium-
based cholestane receptor. Tetrahedron Letters 2011;52:1623e7.
[17] Yanagita M, Aoki I, Tokita S. New fluoran leuco dyes having a phenylenedi-
amine moiety at the 6-position of the xanthene ring. Dyes and Pigments 1998;
36:15e26.
which is the inherent A586/A447 value of ODB with Hg2þ
.