Synthesis of highly fluorescent and water soluble perylene bisimide

Article abstract of DOI:10.1016/j.cclet.2011.10.017

Designed and synthesized a new highly water soluble N,N′-bis(2-((5- ((dimethylamino)methyl)furan-2-yl)methylthio)ethyl)perylene-3,4,9, 10-tetracarboxylic diimide from 2-((5-((dimethylamino)methyl)furan-2-yl) methylthio)ethanamine and perylene-3,4,9,10-tetracarboxylic dianhydride. The compound was characterized by ¹H, ¹³C, 2D NMR, mass and IR techniques. The compound is highly fluorescent with good solubility in water and other polar solvents.

Full text of DOI:10.1016/j.cclet.2011.10.017

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Chinese Chemical Letters 23 (2012) 149–153
www.elsevier.com/locate/cclet
Synthesis of highly fluorescent and water soluble
perylene bisimide
Gopal Boobalan a, Predhanekar Mohamed Imran b, Samuthira Nagarajan a,
*
a Department of Chemistry, Annamalai University, Annamalainagar 608002, India
b Department of Chemistry, Islamiah College, Vaniyambadi 635752, India
Received 20 July 2011
Available online 23 December 2011
Abstract
Designed and synthesized a new highly water soluble N,N0-bis(2-((5-((dimethylamino)methyl)furan-2-yl)methylthio)ethyl)-
perylene-3,4,9,10-tetracarboxylic diimide from 2-((5-((dimethylamino)methyl)furan-2-yl)methylthio)ethanamine and perylene-
3,4,9,10-tetracarboxylic dianhydride. The compound was characterized by 1H, 13C, 2D NMR, mass and IR techniques. The
compound is highly fluorescent with good solubility in water and other polar solvents.
# 2011 Samuthira Nagarajan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Perylene bisimide; Synthesis; Water soluble; Fluorescent
Perylene tetracarboxylic diimide’s (PTCDI) are highly versatile molecules, which attract a great interest owing to
their applications in diverse fields of organic electronics, such as dye lasers [1] light harvesting arrays [2] and other
electronic devices [3–5]. These compounds have also been widely studied for biochemical and pharmacological
purposes because perylene bisimides are considered as potential antitumor drugs acting as telomerase inhibitors [6,7].
Various types of PTCDI have been extensively studied for applications due to their high molar absorptivity, high
quantum yield of fluorescence with excellent photochemical and thermal stability [8]. Depending on the substituents,
perylene derivatives can exist in a wide range of hues; they provide yellow, orange, red, bordeaux, brown and even
black shades [9]. All these properties of this family of molecules largely depend on the nature and position of
substituents attached to the main perylene board and on the matrix in which they are embedded [10–12]. Various types
of new PTCDI molecules are synthesized for numerous applications in modern electronics. In this article, we designed
and synthesized a new highly fluorescent and water soluble PTCDI molecule namely, N,N0-bis(2-((5-
((dimethylamino)methyl)furan-2-yl)methylthio)ethyl)perylene-3,4,9,10-tetracarboxylic diimide for potential appli-
cation in organic electronics. The compound was characterized using various spectral techniques.
* Corresponding author.
E-mail address: nagarajan.au@gmail.com (S. Nagarajan).
1001-8417/$ – see front matter # 2011 Samuthira Nagarajan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.10.017

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1. Experimental
1.1. Preparation of compounds
2-((5-((Dimethylamino)methyl)furan-2-yl)methylthio)ethanamine 1: In a 250 mL round bottom flask, a mixture of
furfuryl alcohol (0.98 g, 10 mmol), formaldehyde (0.30 g, 10 mmol) and dimethylamine hydrochloride (0.45 g,
10 mmol) was dissolved in 50 mL absolute methanol. The reaction mixture was heated at 70–80 8C for 12 h. After
12 h 2-aminoethanthiol hydrochloride (1.13 g, 10 mmol) was added, stirred and heated at 120–130 8C for additional
7 h. The reaction mixture was cooled and poured into water. The suspension was extracted with chloroform and the
solvent was removed. The product formed as yellow oil (yield 85%). 1H NMR (500 MHz, CDCl3): d 2.16 (s, 2H, NH2),
2.23 (s, 6H, CH3), 2.59 (t, 2H, J = 6.5 Hz, CH2), 2.80 (t, 2H, J = 6.5 Hz, CH2), 3.41 (s, 2H, CH2), 3.68 (s, 2H, CH2),
13
6.11 (s, 2H, CH); C NMR (125 MHz, CDCl3): d 27.4 (C10), 35.1 (C30), 40.1 (C40), 44.2 (C300), 55.1 (C100), 107.3
(C3), 108.7 (C4), 150.5 (C2), 151.1 (C5); MS (CI, m/z): [M+] calcd. for C10H18N2OS, 215.3; found, 215.8.
N,N0-Bis(2-((5-((dimethylamino)methyl)furan-2-yl)methylthio)ethyl)perylene-3,4,9,10-tetracarboxylic diimide 3:
The compound 3 was synthesized following the standard condensation method developed by Langhals [13]. Briefly, in
a 250 mL round bottom flask, 2 (3.7 g, 9.4 mmol), 1 (3.29 g, 23 mmol) and 15 g imidazole were stirred 5 h at 180 8C.
The mixture was cooled to room temperature, taken up in 100 mL ethanol, treated with 400 mL 2 mol/L HCl and
stirred overnight. The dark red precipitate was filtered washed with triethylamine and little dichloromethane. The
filtered product was dried at 130 8C. 1H NMR (500 MHz, DMSO-d6): d 2.72 (s, 16H, CH2 and CH3 (merged)), 3.92 (s,
4H, CH2), 4.00 (s, 4H, CH2), 4.37 (s, 4H, CH2), 6.48 (s, 2H, CH), 6.74 (s, 2H, CH), 7.66–7.38 (m, perylene H); 13
C
NMR (125 MHz, DMSO-d6): d 27.0 (C10), 28.2 (C30), 39.5 (C40), 41.2 (C300), 51.4 (C100), 109.1 (C3), 115.2 (C4),
119.1, 120.7, 126.5, 129.4, 132.1, 134.1 (Ar–C), 144.0 (C2), 153.3 (C5), 161.6 (CO); IR (KBr): n = 3421 (m), 2922
(m), 2853 (m), 1690 (s), 1653 (vs), 1591 (s), 1339 (s), 1160 (m), 1018 (m), 808 (m), 744 (m) cmꢀ1; MS (CI, m/z): [M+]
calcd. for C44H40N4O6S2, 784.9; found, 784.5.UV–vis (MeOH): lmax (e) 459 (18,511), 486 (37,809), 522 nm
(50,993); fluorescence (MeOH): lmax = 534, 572 nm (lexc = 460); yield: 84%.
1.2. Computational details
The molecule was first constructed using Chemcraft programme [Chemcraft, tool for treatment of the chemical
data, version 1.5 (build 286), Zhurko and Zhurko, www.chemcraftprog.com]. This was subjected to Molecular
Mechanics corrections using Discovery Studio Visualizer [www.accelrys.com]. This was done for molecules using
both symmetry point groups, i.e. C2 and Ci. These structures were separately optimized using MOPAC, a semi-
empirical programme. The theoretical NMR calculation was done for the DFToptimized geometry using Gaussian 03
and NMR tensors were viewed with Gaussview.
The fluorescence microscopy image was recorded with a LEICA BM-2500 microscope, which provides excitation
in the range of 450–490 nm; emission >515 nm.
2. Results and discussion
The water soluble PTCDI molecule was designed by incorporating polar tails in the aromatic perylene board. The
starting material 2-((5-((dimethylamino)methyl)furan-2-yl)methylthio)ethanamine 1 was prepared from furfuryl
alcohol, dimethylamine hydrochloride, formaldehyde and 2-aminoethanethiol hydrochloride by refluxing in methanol
at 120–130 8C. The condensation of perylene-3,4,9,10-tetracarboxylic dianhydride 2 and 1 using imidazole as a
solvent resulted in the formation of N,N0-bis(2-((5-((dimethylamino)methyl)furan-2-yl)methylthio)ethyl)perylene-
3,4,9,10-tetracarboxylic diimide 3 (Scheme 1). The compounds 1 and 3 were characterized by mass, IR, 1H, 13C and
2D NMR (1H–1H COSY and 1H–13C COSY) techniques. The 1H NMR spectrum of the compound 3 was recorded in
D2O and DMSO-d6. In D2O the aliphatic proton signals were well resolved and the aromatic perylene protons signals
were observed as a singlet at 7.40 ppm. The absence of coupling in the aromatic protons may be due to the p–p
stacking. In DMSO, the NMR spectrum shows the characteristic aromatic proton peaks. The IR spectrum of 3 in KBr
shows the bands at 2922–2853 (C–H stretching), 1339 (C–N stretching), 1591 (C C stretching) and 1690, 1653 cmꢀ1
( C O stretching). The spectral data are consistent with the proposed structure of the molecule. Table 1 shows the 2D
NMR data of 3.

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151
Scheme 1. Synthesis of compound 3.
Table 1
1H, 13C and 2D NMR (1H–1H COSY, 1H–13C COSY) for compound 3.
Atom position
dH
dC
1H–1H COSY
1H–13C COSY
a
–
161.6
134.1
129.4
119.1
132.1
120.7
126.5
27.0
–
–
b
–
–
–
c
7.66–7.38 (m, 8H perylene)
–
C–c
C–d
–
d
–
e
–
–
f
–
–
–
g
–
–
–
10
30
300
40
2
3.92 (s, 4H)
2.72 (s, 16H)
–
H–40
C–10
C–30
C–300
C–40
–
28.2
41.2
–
4.00 (s, 4H)
–
39.5
H–30
–
144.0
109.1
115.2
153.3
51.4
3
6.48 (s, 2H)
6.74 (s, 2H)
–
H–4
H–3
–
C–3
C–4
–
4
5
100
4.37 (s, 4H)
–
C–100
The compound 3 is soluble in water (1.2 mg/mL), MeOH (0.8 mg/mL), DMF (0.6 mg/mL) and DMSO (1.0 mg/
mL). The absorption spectrum of 3 shows typical monomeric p–p transition band with three pronounced peaks at 522,
486 and 459 nm, which correspond to the 0–0, 0–1 and 0–2 electronic transitions, respectively (Fig. 1a) [14,15]. There
is no shift in lmax position with increasing the concentration of the compound. Fig. 1b shows the fluorescence spectra
Fig. 1. (a) UV–vis absorption; (b) fluorescence spectra of 3 MeOH; (c) UV–vis absorption spectra of 3 in polar solvents.

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G. Boobalan et al. / Chinese Chemical Letters 23 (2012) 149–153
Table 2
UV–visible absorption maxima of 3 in various solvents.
Solvent
l1 (nm)
l2 (nm)
l3 (nm)
MeOH
DMF
522
527
530
563
486
490
492
533
459
461
462
478
DMSO
Water
of 3 in methanol at various concentrations, with lexc = 460 nm. The fluorescence emission peaks appeared at 534 and
572 nm. The fluorescence spectrum depicts the mirror image of the absorption; due to two nitrogen’s position at the
node in p orbitals. The solubility of 3 in polar solvents allowed us to compare its UV–visible spectra in a range of polar
solvents (CH3OH, DMSO, DMF and H2O). The spectra are shown in Fig. 1c and the lmax values are given in Table 2.
The spectral shape is similar in solvents and the spectral shift is not straightly dependent on the solvent polarity. This
may be due to some specific solvent molecule interactions at various solvents. However, solvatochromism was
observed in water as shown by decreased extinction coefficient and a bathochromic shift of absorption peaks. The
observed decrease in molar extinction coefficient of the compound in water with respect to organic solvents may be
due to the self-aggregation despite its water solubility. Similar trends were also reported for the perylene diimide
hydrochlorides and coronene derivatives [16]. Furthermore, the relative intensities of the absorption peaks changed,
with the 0 ! 1 transition (at 533 nm) becoming lmax. Similar behaviour has been reported for tethered oligomers of
perylene diimides as well as concentrated solutions of perylene diimides [17]. The compound 3 is more soluble in
water than organic solvents due to the polar side chain. The greater conformational flexibility of the 2-((5-
((dimethylamino)methyl)furan-2-yl)methylthio)ethyl side chain (compared to alkyl chains) affords sufficient
Fig. 2. Fluorescent microscopic image of 3 coated on glass plate.
Fig. 3. NMR shielding regions of 3 generated by GIAO method.