Structure and spectral property of 8-(2-(5-(4-methylphenyl)-2-thienyl) vinyl)-10,10-dimethyl-10Hpyrido[1,2-a]indolium perchlorate

Article abstract of DOI:10.1007/s11164-012-0539-4

The title compound 8-(2-(5-(4-methylphenyl)-2-thienyl)vinyl)l-10,10- dimethyl-10H-pyrido[1,2-a]indolium perchlorate (3) has been synthesized by cycloaddition and condensation reactions, and characterized by elemental analysis, IR, ¹H NMR, and single-crystal X-ray diffraction. The crystal structure analysis exhibits that the molecule of 3 possesses good coplanarity, and the three rings (10Hpyrido[1,2-a]indolium, thienyl and phenyl) and vinyl moiety can make up a large conjugated system. Its UV-Vis and fluorescence spectra were measured, and found that it displays larger maximum absorptions and emission wavelengths in comparison with 8-(4-methylphenyl)vinyl analogue. Springer Science+Business Media B.V. 2012.

Full text of DOI:10.1007/s11164-012-0539-4

Res Chem Intermed (2012) 38:2229–2235
DOI 10.1007/s11164-012-0539-4
Structure and spectral property of 8-(2-(5-(4-
methylphenyl)-2-thienyl)vinyl)-10,10-dimethyl-10H-
pyrido[1,2-a]indolium perchlorate
•
Lin Jiang Peng Cao Yulei Zhang Xiezhong Xie
•
•
Received: 17 January 2012 / Accepted: 20 March 2012 / Published online: 10 April 2012
Ó Springer Science+Business Media B.V. 2012
Abstract The title compound 8-(2-(5-(4-methylphenyl)-2-thienyl)vinyl)l-10,10-
dimethyl-10H-pyrido[1,2-a]indolium perchlorate (3) has been synthesized by
cycloaddition and condensation reactions, and characterized by elemental analysis,
1
IR, H NMR, and single-crystal X-ray diffraction. The crystal structure analysis
exhibits that the molecule of 3 possesses good coplanarity, and the three rings (10H-
pyrido[1,2-a]indolium, thienyl and phenyl) and vinyl moiety can make up a large
conjugated system. Its UV-Vis and fluorescence spectra were measured, and found
that it displays larger maximum absorptions and emission wavelengths in com-
parison with 8-(4-methylphenyl)vinyl analogue.
Keywords Synthesis Á 10H-pyrido[1,2-a]indolium perchlorate Á
Crystal structure Á Spectral property
Introduction
Substituted 10H-pyrido[1,2-a]indolium perchlorates can be used as photosensitive
dyes, fluorescent whiteners, and organic light-guide sensitizers [1–3]. Since the first
substituted 10H-pyrido[1,2-a]indolium perchlorate was prepared by Chapman in
1974, many of these types of compounds, such as methyl, phenyl, styryl or furyl-
substituted 10H-pyrido[1,2-a]indolium perchlorates, have been synthesized [4–8].
On the basis of synthesis and spectral property study of this class of compounds, Liu
L. Jiang (&) Á P. Cao Á Y. Zhang Á X. Xie
College of Chemistry and Material Science, Shandong Agricultural University,
Tai’an 271018, China
e-mail: jiangl@sdau.edu.cn
Y. Zhang Á X. Xie
College of Water Conservancy and Civil Engineering, Shandong Agricultural University,
Tai’an, China
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L. Jiang et al.
H3C CH3
H3C CH3
iso-C4H9OH
CHO
CH3
+
+
N
H3C
+
N
CH3
H
ClO4
ClO4
1
2
CHO
H3C CH3
S
H3C
+
N
S
EtOH, piperidine
ClO4
CH3
3
Scheme 1 Synthetic route for the target compound
et al. [9] found that the introduction of a conjugated substituent at the 8-position of
10H-pyrido[1,2-a]indolium ring can yield a significant red shift of the maximum
absorption and maximum emission, and no remarkable change was observed while
the introduction was at the 6-position.
In order to further study the relationship between the structure and maximum
absorption, the crystal structures of three compounds in this family were determined
by single-crystal X-ray diffraction [10–12], and found that the dihedral angle between
10H-pyrido[1,2-a]indolium and substituted phenyl at the 8-position is small, ranging
from 27.2° to 29.8°. Therefore, the two groups are able to make up a conjugated
system, and this is the reason for a significant red shift when a conjugated substituent
was introduced at the 8-position. Considering that thiophene possesses unique optical
properties, and electronic transmission capability [13], herein, we introduced 5-[(4-
methyphenyl)-2-thienyl] vinyl onto the 8-position of 10H-pyrido[1,2-a]indolium and
synthesized the target compound 3, obtaining a compound with large maximum
absorption and maximum emission. The structure was confirmed by elemental
analysis, IR, 1H NMR. The synthetic route is shown in Scheme 1.
Experimental
General
2,3,3-Trimethyl-3H-indolium perchlorate (1) [14] and 8,10,10-trimethyl-10H-pyr-
ido[1,2-a]indolium perchlorate (2) [5] were prepared in our laboratory, respectively.
5-(4-Methylphenyl)-2-thiophene-carbaldehyde was prepared by the application
of Vilsmeier formylation to 5-(4-methyphenyl)-2-thiophene [15, 16]. The other
chemicals were of analytical grade and were distilled before use.
Melting point was determined with an X-5 microscopic melting-point apparatus
and uncorrected. Elemental analyses were performed with a Vario EL III Elemental
Analyzer. IR spectra were recorded in KBr pellet on a Nicolet-6700 infrared
spectrophotometer. 1H NMR spectra were carried out on a Varian Mercury Plus 400
123

Structure and spectral property
2231
spectrometer in DMSO-d6 with TMS as internal standard. UV-Vis and fluorescence
spectra were measured using acetonitrile as solvent (2 9 10-5 M) on a Shimdazu
2450PC UV-Vis a spectrophotometer and RF-5301PC fluorophotometer, respec-
tively. X-ray data were collected on a Bruker Smart APEX CCD diffractometer.
Synthesis
A mixture of 2 (0.37 g, 1.2 mmol) and 5-(4-methyphenyl)-2-thiophenecarbaldehyde
(0.24 g, 1.2 mmol) in anhydrous ethanol (10 mL) was added five drops of
piperidine and was heated to refluxing temperature with stirring. After refluxing for
5 h, the resulting mixture was cooled to room temperature. Then the mixture was
filtered under reduced pressure and the solid residue was recrystallized from
ethanol-acetonitrile (V:V = 2:1), affording compound 3 as a red needle (0.46 g,
yield 78.5%), m.p. 259.1–260.8 °C. Anal. Calcd. (%) for C27H24ClNO4S: C 65.65,
H 4.90, N 2.84; found: C 65.42, H 4.83, N 2.79. IR (KBr pellet, cm-1), 1640.9 (m),
1362.2 (w), 1101.6 (s), 957.3 (s), 620.7 (m). 1H NMR (DMSO-d6, 400 MHz), d1.78
[s, 6H, C(CH3)2], 2.39 (s, 3H, CH3), 7.16 [d, J = 16 Hz, 1H, –CH=CH– (E)],
7.25–7.59 (m, 4H, Ph-H), 7.45–7.50 (m, 2H, thiophene-H), 7.66–8.21 (m, 4H,
indole-H), 8.30 [d, J = 16 Hz, 1H, –CH=CH–(E)], 8.32 (d, J = 6.8 Hz, 1H,
pyridinum-7-H), 8.65 (s, 1H, pyridinum-9-H), 9.66 (d, J = 6.8 Hz, 1H, pyridinum-
6-H). The red single crystal was cultured from a mixture solution of ethanol and
acetonitrile by slow evaporation at room temperature.
Crystal structure determination
A red crystal of the target compound with dimensions of 0.21 9 0.14 9 0.12 mm3 was
selected for X-ray diffraction analysis. The data were collected by a Bruker Smart APEX
CCD diffractometer equipped with a graphite-monochromated MoKa radiation
˚
(k = 0.71073 A) at 298(2) K. A total of 12,381 reflections were collected in the range
of 1.65° B hB25.05° by using a u-x scan mode, among which 4,262 (Rint = 0.0279)
were unique ones. The structure was solved by direct methods and expanded by using
difference Fourier techniques with SHELXS-97 [17]. All the non-hydrogen atoms were
refined anisotropically, while the hydrogen atoms were located geometrically and refined
isotropically. The final full-matrix least-squares refinement gave the final R = 0.0488,
and wR = 0.1257 (w = 1/[r2(Fo2) ? (0.0604P)2 ? 1.3404P], where P = (Fo2 ? 2F2c)/3),
3
˚
(Dq)max = 0.449, (Dq)min = -0.312 e/A . The molecular structure and the packing
diagram in a unit-cell of compound 3 are shown in Figs. 1 and 2, respectively. The
selected bond lengths, bond angles, and torsion angles are listed in Tables 1 and 2.
Results and discussion
Crystal structure
In the crystal structure of compound 3 (Fig. 1), the 10H-pyrido[1,2-a]indolium ring
and a thiophene ring are connected with an E-type C=C bond, which is also
123

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L. Jiang et al.
Fig. 1 Molecular structure of compound 3
Fig. 2 Packing diagram in unit-cell of compound 3
˚
Table 1 Selected bond lengths (A) and bond angles (°) of compound 3
Bond
Dist.
Bond
Dist.
Bond
Dist.
N1–C1
1.431(3)
1.364(3)
1.361(3)
1.402(4)
(°)
C12–C15
1.447(4)
1.328(4)
1.441(4)
1.363(4)
(°)
S1–C17
1.719(3)
1.363(4)
1.468(4)
1.719(3)
(°)
N1–C10
C15–C16
C19–C20
N1–C14
C16–C17
C20–C21
C12–C13
C17–C18
S1–C20
Angle
Angle
Angle
C10–N1–C1
C14–N1–C10
C11–C12–C13
C11–C12–C15
110.6(2)
121.6(2)
117.2(3)
123.0(3)
C16–C15–C12
C15–C16–C17
C16–C17–S1
C18–C17–S1
124.9(3)
125.6(3)
122.2(2)
110.0(2)
C19–C20–S1
C19–C20–C21
C22–C21–C20
C26–C21–C22
109.6(2)
129.5(3)
121.1(3)
116.8(3)
123

Structure and spectral property
2233
Table 2 Selected torsion angles (°) of compound 3
Angle
(°)
179.1(2)
Angle
(°)
C1–N1–C10–C11
C2–C1–C6–C7
C14–N1–C1–C2
-1.0(4)
175.9(3)
-5.6(4)
0.1(5)
179.7(3)
177.3(3)
C15–C16–C17–C18
C15–C16–C17–S1
C19–C20–C21–C22
S1–C20–C21–C22
S1–C20–C21–C26
C7–C10–C11–C12
C11–C12–C15–C16
C12–C15–C16–C17
C13–C12–C15–C16
-11.2(4)
-179.9(3)
168.8(3)
-179.3(2)
-0.5(4)
Fig. 3 UV-Vis spectrum of
compound 3
confirmed by a coupling constant of 16 Hz for the hydrogen atoms attached to the
1
double bond in H NMR spectrum. The single bond lengths of C12–C15 and C16–
˚
C17 are 1.447(4) and 1.441(4) A, respectively, both shorter than the normal C–C
˚
bond (1.540 A) [18], which means both the two single bonds possess a partial
double bond character and the electron density was delocalized among C12, C15,
C16, and C17 atoms. On the other hand, the torsion angles from C15 to C26, S1 are
all near to 0.0° or -180°/180° (Table 2), indicating small dihedral angles between
the rings and vinyl moiety. It is estimated that the dihedral angles between 10H-
pyrido[1,2-a]indolium and vinyl, thiophene and vinyl, thiophene and methylben-
zene moiety are 11.52°, 5.25°, and 2.65°, respectively. Therefore, it is deduced that
the three rings and vinyl moiety in 3 can make up a large conjugated system.
UV-Vis spectral property
There are two absorption bands in compound 3 (Fig. 3), of which k1max and km2 ax are
305.5 and 449.5 nm, respectively. According to the method of Ref. [19], it is
deduced that k2max might be attributed to the p ? p* transition of the whole
conjugated system in the molecule, while k1max may be assigned to the p ? p*
transition of the partial conjugated system related to 10H-pyrido[1,2-a]indolium
moiety. Moreover, k2max undergoes a significant red shift (77.0 nm) in comparison to
123

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L. Jiang et al.
Fig. 4 Fluorescence spectrum
of compound 3
8-(4-methylphenyl)vinyl analogue (kmax = 372.5 nm) [7], resulting from the
introduction of a thiophene ring in compound 3.
Fluorescent spectral property
As shown in Fig. 4, the maximum emission of 3 is 567.0 nm, which also exhibits a
remarkable red shift (99.0 nm) in comparison with 8-(4-methylphenyl)vinyl
analogue (kem = 468.0 nm) [7]. In addition, the fluorescence quantum yield of
the title compound was measured according to Ref. [20], and the value is 0.065.
Conclusions
In conclusion, a novel substituted 10H-pyrido[1,2-a]indolium perchlorate has been
synthesized and characterized by elemental analysis, IR, 1H NMR, and single-
crystal X-ray diffraction. The target compound exhibits good coplanarity, and as a
result, rings and vinyl can make up a large conjugated system. Thus, it possesses
larger maximum absorptions and emission wavelengths, and undergoes significant
red shifts in maximum absorption and emission wavelength in comparison with
8-(4-methylphenyl)vinyl analogue, respectively.
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