Vibrational spectroscopic study on 2-[2-(4-dipropylamino-phenyl)-vinyl]-1, 3,3-trimethyl-3H-indolium chloride

Article abstract of DOI:10.1016/j.saa.2010.12.007

A new styryl dye were prepared, 2-[2-(4-dipropylamino-phenyl)-vinyl]-1,3,3- trimethyl-3H-indolium chloride (DPPTVI) chloride. Its infrared and Raman were measured. Quantum chemical calculations were computed for both the isolated and the solute cation. Op

Full text of DOI:10.1016/j.saa.2010.12.007

Spectrochimica Acta Part A 78 (2011) 967–980
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Vibrational spectroscopic study on 2-[2-(4-dipropylamino-phenyl)-vinyl]-
1,3,3-trimethyl-3H-indolium chloride
Ferenc Billesa,b,∗, András Szabóc, Yaroslav Studenyakd
a Department of Physical Chemistry and Material Science, Budapest University of Technology and Economics, Budafoki út 8, H-1521 Budapest, Hungary
b Institute for Chemical Technology and Analytik, Vienna University of Technology, Getreidemarkt 9/163, A-1060 Vienna, Austria
c Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budafoki út 8, H-1521 Budapest, Hungary
d Department of Analytical Chemistry, Uzhorod National University, vul. Pidhirna 46, Uzhorod UA-88000, Ukraine
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 June 2010
Accepted 6 December 2010
A new styryl dye were prepared, 2-[2-(4-dipropylamino-phenyl)-vinyl]-1,3,3-trimethyl-3H-indolium
chloride (DPPTVI) chloride. Its infrared and Raman were measured. Quantum chemical calculations were
computed for both the isolated and the solute cation. Optimized geometry, atomic net charges were
calculated. The calculated vibrational frequencies were scaled to the experimental ones. Only 12 scale
factors were used for the scaling of 174 vibrational modes. Based on these results, normal coordinate
analysis were carried out for both the isolated and the solute cations. Infrared and Raman spectra were
simulated. The results for the isolated and the solute cations were compared.
Keywords:
Styryl dye
Vibrational spectra
Quantum chemistry
Normal coordinate analysis
Spectrum simulation
Solvent effect
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
cyanine dyes with one and two vinylydene groups and similarly
investigated also their acid–base properties. Balogh et al. [8] dealt
2-[2-(4-Dipropylamino-phenyl)-vinyl]-1,3,3-trimethyl-3H-
indolium chloride (DPPTVI chloride) is a new dye that seems very
suitable for analytical applications through complexation. In this
way it can be applied for quantitative analytic determination of
organic and inorganic ions.
The literature of styryl dyes is very wide. They are applied for
several purposes. Deligeorgiev et al. [1] in their recent review about
the synthesis and application of styryl dyes during last 15 years
mention several applications of these dyes, e.g. in optics and laser
technique. They are applied in the medical practice [2,3], and as
fluorescent reagents [2,4].
with the pH dependence of Cation Violet. Andruch and coworkers
[9] studied the structure and acid–base properties of the (2-[2-4(-
methoxy-phenylamino)-vinyl]-1,3,3-trimethyl-3H-indolium-ion.
Complexation is applied first of all for the determination of
cations. Determination of magnesium [10–12], mercury, lead [13],
cadmium [13,14] calcium, strontium and barium [11], manganese
[15] is reported. Selenium can be analyzed through an indirect
way, by applying chemical reactions [16]. The determination of
nitrophenols is based on their interaction with the Astrazon Vio-
let 3R dye [17]. Boron is analyzable after its conversion into boron
tetrafluoride anion [18].
One of the broad spheres of application of styryl dyes is ana-
lytical chemistry. Namely, several styryl dyes contain polar groups,
which are capable for complexation. The complexation process was
studied by Druzhinin et al. [5].
The choice of the appropriate compounds depends on their
acid–base properties. Lehman et al. [6] synthesized and studied
these properties of some amphiphylic acidichromic hydroxystil-
bazolium dyes. Osman et al. [7] synthesized oxazine methine
2. Experimental
2.1. Synthesis
Synthesis of the styryl dye, 2-[2-(4-dipropylaminophenyl)-
1-ethenyl]-1,3,3-trimethyl-3H-indolium
achieved through condensation of equimolar amounts of 4-
(dipropylamino)benzaldehyde and proper quaternary ammonium
salt (Fisher base) in an acetic anhydride (with addition of
triethylamine) as depicted in the Scheme 1.
Method of synthesis:
base (1.048 g, 5 mmol), 4-(dipropylamino)benzaldehyde (1.025 g,
5 mmol), acetic anhydride (3 ml) and 2 drops of triethylamine was
chloride
was
∗
Corresponding author at: Department of Physical Chemistry and Material Sci-
A mixture containing salt of Fisher
ence, Budapest University of Technology and Economics, Budafoki út 8, H-1521
Budapest, Hungary. Tel.: +36 1 463 1267; fax: +36 1 463 3767.
E-mail address: fbilles@mail.bme.hu (F. Billes).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.12.007

968
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Scheme 1. Synthesis strategy.
heated under reflux for 5 min. After cooling, the dark crystals with
metallic sheen were filtered, washed with diethyl ether and dried.
The subsequent purification of the synthesized dye was done by
re-crystallization from methanol.
Fig. 1. (a) Optimized geometry of the DPPTVI cation, view a. (b) Optimized geometry
of the DPPVTI cation, view b.
2.2. Spectroscopic measurements
similar coordinates were summed up. Based on the scaled calcu-
lated frequencies and the corresponding calculated intensities the
infrared and Raman spectra were simulated.
The infrared spectra were recorded on a Bruker tensor 37 spec-
trometer in KBr disks, with DTGS detector, in the 4000–400 cm−1
region.
Home-made programs were applied for the elaboration of the
quantum chemical results. This comprises calculation of the inverse
kinetic energy (G) matrix, transformation of the calculated force
constants into the field of the defined internal coordinates, nor-
mal coordinate analysis including the calculation of the potential
energy distributions and simulation of the vibrational spectra.
In order to reveal the effect of water as a solvent on the DPPVTI
properties we simulated the properties of this molecule in aque-
ous solution. Namely, as an analytical reagent, DPPVTI is used in
aqueous solution. The polarized continuum model (PCM) [23–25]
was applied. For the molecule in solution the same quantum chem-
ical calculations were carried out as those for the isolated one. The
further application of the quantum chemical data was also simi-
lar. The optimized scale factors were transferred from the isolated
DPPTVI to the solute one. The results of the two calculations were
compared.
The Raman spectra were measured applying a Jobin-Yvon
Horiba LabRAM spectrometer, in the 4000–200 cm−1 region. A
Wright CCD (256 × 1024) detector was used. The 785 nm laser
band was found as the best one for excitation of the spectra.
Namely, the sample showed strong fluorescence at 532 nm or
633 nm excitation. The integration time was changed from 60 s to
600 s, depending on the spectral region; the SNR was under these
conditions not satisfactory in the CH stretching region, because of
the low quantum efficiency of CCD for NIR photons. The spectra
were base line corrected.
Strong fluorescence of the compound was observed in DMSO
solution. The observed emission maximum was at 611 m [19].
3. Calculations
The overlapping bands were resolved by deconvolution [26].
Quantum chemical calculations were carried out. The DFT
method with the B3P86 hybrid functional [20,21] and the 6-31G*
basis set was chosen for the computations, using the Gaussian 03
program package [22]. The first step of the calculations produced
the optimized molecular geometry, the NBO and Mulliken’s atomic
net charges. The second step gave us the unscaled vibrational fre-
quencies, infrared and Raman intensities with their depolarization
factors and the vibrational force constants.
The inverted kinetic energy matrix (G matrix) was calculated
using the optimized molecular geometry and the atomic mass
values. The quantum chemical results contain the force constant
matrices (F matrix) in atomic units. These were transformed into
SI units and into the internal coordinate system defined by us. The
force constants (the full F matrix) were scaled to the experimental
frequencies through fitting the GF matrix eigenvalues to the exper-
imental frequency data with optimization. Since the cation of the
DPPTVI molecule contains 60 atoms, 174 internal coordinates were
defined. This is also the magnitude of the scaling. However, only 12
independent scale factors were necessary for the scaling, providing
that chemically similar coordinates can have the same scale fac-
tor. The eigenvectors of the GF matrix were used for the potential
energy distribution (PED) matrix. The weights of the chemically
4. Results and discussion
4.1. Molecular geometry
DPPTVI can have several conformers since quasi free rotations
are possible around some single bonds. We have performed calcu-
lations for one of the possible DPPTVI configurations.
Fig. 1 introduces the calculated optimized geometry of the
DPPTVI cation in two views (a and b). Although there is a conjuga-
tive coupling possible between the phenyl and the indole rings, the
two rings are not coplanar. The conjugation can spread through an
N–C bond of the pyrrolidnium ring and the C C bond of the vinyl
group (see also Table 1 ). The numbering of the DPPTVI atoms is
presented in Fig. 2.
The optimized parameters of the DPPTVI ions are listed in
Table 1. As to the solvent effect on the geometric parame-
ters, most of the changes in the bond lengths remain below
´
˚
◦
0.1 A, the changes in the valence angles are all below 1 , the
greater part of the torsion angles (ꢀ) also change within 1◦.
Greater changes are observable in the environments of the nitro-

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 1 (Continued )
969
Table 1
Geometric parameters of the DPPTVI cation.
Parametera
Isolated
Solute
Parametera
Isolated
Solute
Parametera
Isolated
Solute
1.400
Parametera
Isolated
Solute
ϕ (6, 5,57)
ϕ (4, 6, 5)
ϕ (4, 6, 7)
ϕ (5, 6, 7)
ϕ (6, 7, 8)
ϕ (6, 7, 9)
ϕ (6, 7,12)
ϕ (8, 7, 9)
ϕ (8, 7,12)
ϕ (9, 7,12)
ϕ (7, 8,54)
ϕ (7, 8,55)
121.1
119.7
109.0
131.3
111.4
111.8
101.7
110.5
110.4
110.8
109.3
111.2
111.6
107.8
108.1
108.7
111.1
109.5
111.5
108.0
108.5
108.2
121.9
111.2
126.7
108.7
109.4
111.5
108.5
108.9
109.8
109.2
121.8
128.9
128.9
113.2
117.6
126.9
118.6
114.4
119.3
124.4
116.4
122.5
118.8
118.7
121.6
118.4
120.0
121.9
120.0
118.1
120.9
116.6
122.5
123.3
121.1
115.6
121.0
118.5
120.4
114.6
109.1
106.7
110.6
109.5
105.9
114.4
109.5
106.8
110.6
109.3
105.9
114.4
107.0
109.2
110.0
121.0
119.9
109.0
131.1
111.3
111.8
101.6
110.4
110.5
110.9
109.2
111.1
111.3
108.1
108.3
108.7
110.9
109.4
111.3
108.2
108.6
108.3
121.9
111.2
126.8
108.7
109.4
111.2
108.7
109.1
109.7
109.2
121.8
129.0
128.6
113.6
117.7
126.8
119.0
114.1
119.1
124.5
116.5
122.4
118.8
118.8
121.6
117.9
120.4
121.8
120.2
118.0
121.0
116.5
122.5
123.2
121.3
115.5
121.1
118.1
120.8
114.9
109.3
106.8
110.3
109.0
106.2
114.6
109.5
106.7
110.3
109.2
106.2
114.8
106.7
109.3
109.8
ꢀ (13,14,15,16)
ꢀ (13,14,15,18)
ꢀ (46,14,15,16)
ꢀ (46,14,15,18)
ꢀ (14,15,16,21)
ꢀ (14,15,16,45)
ꢀ (18,15,16,21)
ꢀ (18,15,16,45)
ꢀ (14,15,18,17)
ꢀ (14,15,18,43)
ꢀ (16,15,18,17)
ꢀ (16,15,18,43)
ꢀ (15,16,21,19)
ꢀ (15,16,21,42)
ꢀ (45,16,21,19)
ꢀ (45,16,21,42)
ꢀ (19,17,18,15)
ꢀ (19,17,18,43)
ꢀ (44,17,18,15)
ꢀ (44,17,18,43)
ꢀ (18,17,19,20)
ꢀ (18,17,19,21)
ꢀ (44,17,19,20)
ꢀ (44,17,19,21)
ꢀ (17,19,20,22)
ꢀ (17,19,20,23)
ꢀ (21,19,20,22)
ꢀ (21,19,20,23)
ꢀ (17,19,21,16)
ꢀ (17,19,21,42)
ꢀ (20,19,21,16)
ꢀ (20,19,21,42)
ꢀ (19,20,22,24)
ꢀ (19,20,22,40)
ꢀ (19,20,22,41)
ꢀ (23,20,22,24)
ꢀ (23,20,22,40)
ꢀ (23,20,22,41)
ꢀ (19,20,23,25)
ꢀ (19,20,23,38)
ꢀ (19,20,23,39)
ꢀ (22,20,23,25)
ꢀ (22,20,23,38)
ꢀ (22,20,23,39)
ꢀ (20,22,24,27)
ꢀ (20,22,24,36)
ꢀ (20,22,24,37)
ꢀ (40,22,24,27)
ꢀ (40,22,24,36)
ꢀ (40,22,24,37)
ꢀ (41,22,24,27)
ꢀ (41,22,24,36)
ꢀ (41,22,24,37)
ꢀ (20,23,25,26)
ꢀ (20,23,25,34)
ꢀ (20,23,25,35)
ꢀ (38,23,25,26)
ꢀ (38,23,25,34)
ꢀ (38,23,25,35)
ꢀ (39,23,25,26)
ꢀ (39,23,25,34)
ꢀ (39,23,25,35)
ꢀ (22,24,27,28)
ꢀ (22,24,27,29)
ꢀ (22,24,27,30)
ꢀ (36,24,27,28)
ꢀ (36,24,27,29)
ꢀ (36,24,27,30)
ꢀ (37,24,27,28)
ꢀ (37,24,27,29)
ꢀ (37,24,27,30)
ꢀ (23,25,26,31)
ꢀ (23,25,26,32)
ꢀ (23,25,26,33)
ꢀ (34,25,26,31)
ꢀ (34,25,26,32)
ꢀ (34,25,26,33)
−175.9
4.1
−176.8
3.5
r (1, 2)
1.395
1.395
1.085
1.387
1.085
1.397
1.085
1.393
1.417
1.385
1.086
1.508
1.541
1.538
1.526
1.094
1.095
1.094
1.094
1.094
1.094
1.449
1.342
1.091
1.092
1.095
1.402
1.384
1.086
1.416
1.086
1.418
1.418
1.371
1.088
1.369
1.430
1.082
1.086
1.354
1.425
1.464
1.464
1.082
1.529
1.091
1.097
1.529
1.097
1.094
1.523
1.097
1.097
1.524
1.096
1.097
1.096
1.096
1.094
1.094
1.095
1.096
121.2
119.1
119.7
116.9
120.5
122.6
120.7
119.6
119.6
122.8
128.4
108.8
118.7
120.3
ꢀ (3, 1, 2, 4)
0.1
−179.0
179.8
0.7
0.1
−179.3
179.9
0.5
r (1, 3)
r (1,60)
r (2, 4)
r (2,59)
r (3, 5)
r (3,58)
r (4, 6)
r (4,10)
r (5, 6)
r (5,57)
r (6, 7)
r (7, 8)
r (7, 9)
r (7,12)
r (8,54)
r (8,55)
1.399
1.089
1.392
1.087
1.402
1.088
1.396
1.423
1.389
1.089
1.515
1.549
1.546
1.535
1.095
1.095
1.095
1.095
1.095
1.095
1.459
1.346
1.091
1.092
1.095
1.407
1.386
1.087
1.423
1.086
1.421
1.421
1.376
1.090
1.374
1.434
1.083
1.089
1.363
1.429
1.473
1.473
1.083
1.538
1.091
1.097
1.537
1.097
1.094
1.531
1.099
1.098
1.532
1.097
1.097
1.097
1.097
1.095
1.096
1.096
1.097
ꢀ (3, 1, 2,59)
ꢀ (60, 1, 2, 4)
ꢀ (60, 1, 2,59)
ꢀ (2, 1, 3, 5)
ꢀ (2, 1, 3,58)
ꢀ (60, 1, 3, 5)
ꢀ (60, 1, 3,58)
ꢀ (1, 2, 4, 6)
ꢀ (1, 2, 4,10)
ꢀ (59, 2, 4, 6)
ꢀ (59, 2, 4,10)
ꢀ (1, 3, 5, 6)
ꢀ (1, 3, 5,57)
ꢀ (58, 3, 5, 6)
ꢀ (58, 3, 5,57)
ꢀ (2, 4, 6, 5)
1.2
0.3
−178.8
−179.8
0.9
−179.4
−179.7
0.7
0.2
0.2
179.9
−179.5
0.2
179.9
−179.6
0.2
0.1
0.0
−179.2
−179.9
0.8
−179.6
179.9
0.4
−0.7
−0.6
179.4
178.5
−1.5
179.5
178.8
−1.2
0.2
0.2
−179.1
−179.3
ϕ (7, 8,56)
0.1
0.1
−0.1
0.0
ϕ (54, 8,55)
ϕ (54, 8,56)
ϕ (55, 8,56)
ϕ (7, 9,51)
ϕ (7, 9,52)
ϕ (7, 9,53)
−178.2
179.4
1.1
−179.1
179.7
0.6
179.8
−179.8
0.1
179.8
−179.7
0.1
−0.7
−0.6
0.8
0.8
178.6
−179.6
−0.3
179.0
−179.6
0.0
r (8,56)
r (9,51)
r (9,52)
r (9,53)
ꢀ (2, 4, 6, 7)
−179.4
−179.2
0.6
−179.5
−179.3
0.5
ꢀ (10, 4, 6, 5)
ꢀ (10, 4, 6, 7)
ꢀ (2, 4,10,11)
ꢀ (2, 4,10,12)
ꢀ (6, 4,10,11)
ꢀ (6, 4,10,12)
ꢀ (3, 5, 6, 4)
ϕ (51, 9,52)
ϕ (51, 9,53)
ϕ (52, 9,53)
ϕ (4,10,11)
ϕ (4,10,12)
ϕ (11,10,12)
ϕ (10,11,48)
ϕ (10,11,49)
ϕ (10,11,50)
ϕ (48,11,49)
ϕ (48,11,50)
ϕ (49,11,50)
ϕ (7,12,10)
ϕ (7,12,13)
ϕ (10,12,13)
ϕ (12,13,14)
ϕ (12,13,47)
ϕ (14,13,47)
ϕ (13,14,15)
ϕ (13,14,46)
ϕ (15,14,46)
ϕ (14,15,16)
ϕ (14,15,18)
ϕ (16,15,18)
ϕ (15,16,21)
ϕ (15,16,45)
ϕ (21,16,45)
ϕ (18,17,19)
ϕ (18,17,44)
ϕ (19,17,44)
ϕ (15,18,17)
ϕ (15,18,43)
ϕ (17,18,43)
ϕ (17,19,20)
ϕ (17,19,21)
ϕ (20,19,21)
ϕ (19,20,22)
ϕ (19,20,23)
ϕ (22,20,23)
ϕ (16,21,19)
ϕ (16,21,42)
ϕ (19,21,42)
ϕ (20,22,24)
ϕ (20,22,40)
ϕ (20,22,41)
ϕ (24,22,40)
ϕ (24,22,41)
ϕ (40,22,41)
ϕ (20,23,25)
ϕ (20,23,38)
ϕ (20,23,39)
ϕ (25,23,38)
ϕ (25,23,39)
ϕ (38,23,39)
ϕ (22,24,27)
ϕ (22,24,36)
ϕ (22,24,37)
ϕ (27,24,36)
−178.7
−179.1
−6.7
−6.4
1.0
0.6
r (10,11)
r (10,12)
r (11,48)
r (11,49)
r (11,50)
r (12,13)
r (13,14)
r (13,47)
r (14,15)
r (14,46)
r (15,16)
r (15,18)
r (16,21)
r (16,45)
r (17,18)
r (17,19)
r (17,44)
r (18,43)
r (19,20)
r (19,21)
r (20,22)
r (20,23)
r (21,42)
r (22,24)
r (22,40)
r (22,41)
r (23,25)
r (23,38)
r (23,39)
r (24,27)
r (24,36)
r (24,37)
r (25,26)
r (25,34)
r (25,35)
r (26,31)
r (26,32)
r (26,33)
r (27,28)
r (27,29)
r (27,30)
ϕ (2, 1, 3)
ϕ (2, 1,60)
ϕ (3, 1,60)
ϕ (1, 2, 4)
ϕ (1, 2,59)
ϕ (4, 2,59)
ϕ (1, 3, 5)
ϕ (1, 3,58)
ϕ (5, 3,58)
ϕ (2, 4, 6)
ϕ (2, 4,10)
ϕ (6, 4,10)
ϕ (3, 5, 6)
ϕ (3, 5,57)
177.6
173.3
−2.4
177.6
173.6
−2.4
0.2
−0.1
179.8
171.3
−6.7
179.6
171.6
−5.2
−0.4
−0.5
ꢀ (3, 5, 6, 7)
179.8
179.7
0.0
179.9
179.7
0.1
−8.3
−8.1
ꢀ (57, 5, 6, 4)
ꢀ (57, 5, 6, 7)
ꢀ (4, 6, 7, 8)
ꢀ (4, 6, 7, 9)
ꢀ (4, 6, 7,12)
ꢀ (5, 6, 7, 8)
173.8
−0.6
175.1
−0.4
−116.5
119.3
1.1
−116.3
119.6
1.3
177.6
178.9
−2.8
178.7
179.3
−1.6
63.3
63.3
106.8
−17.9
−131.9
−75.2
160.2
46.2
107.3
−17.3
−131.8
−75.7
159.7
45.2
ꢀ (5, 6, 7, 9)
−60.9
−179.1
−63.5
177.5
56.0
−60.7
−179.0
−63.4
177.5
56.2
ꢀ (5, 6, 7,12)
ꢀ (6, 7, 8,54)
ꢀ (6, 7, 8,55)
ꢀ (6, 7, 8,56)
ꢀ (9, 7, 8,54)
ꢀ (9, 7, 8,55)
ꢀ (9, 7, 8,56)
ꢀ (12, 7, 8,54)
ꢀ (12, 7, 8,55)
ꢀ (12, 7, 8,56)
ꢀ (6, 7, 9,51)
ꢀ (6, 7, 9,52)
ꢀ (6, 7, 9,53)
ꢀ (8, 7, 9,51)
ꢀ (8, 7, 9,52)
ꢀ (8, 7, 9,53)
ꢀ (12, 7, 9,51)
ꢀ (12, 7, 9,52)
ꢀ (12, 7, 9,53)
ꢀ (6, 7,12,10)
ꢀ (6, 7,12,13)
ꢀ (8, 7,12,10)
ꢀ (8, 7,12,13)
ꢀ (9, 7,12,10)
ꢀ (9, 7,12,13)
ꢀ (4,10,11,48)
ꢀ (4,10,11,49)
ꢀ (4,10,11,50)
ꢀ (12,10,11,48)
ꢀ (12,10,11,49)
ꢀ (12,10,11,50)
ꢀ (4,10,12, 7)
ꢀ (4,10,12,13)
ꢀ (11,10,12, 7)
ꢀ (11,10,12,13)
ꢀ (7,12,13,14)
ꢀ (7,12,13,47)
ꢀ (10,12,13,14)
ꢀ (10,12,13,47)
ꢀ (12,13,14,15)
ꢀ (12,13,14,46)
ꢀ (47,13,14,15)
ꢀ (47,13,14,46)
61.3
61.4
−74.2
−76.2
−57.6
−179.1
−175.7
65.4
−56.2
−177.0
63.8
−57.7
−179.0
−175.6
65.3
−56.0
−177.4
63.3
50.6
48.3
164.8
107.7
−127.5
−13.3
−63.9
173.9
59.9
162.9
106.8
−128.7
−14.2
−63.7
174.5
60.3
−55.9
−56.4
58.3
58.1
59.9
60.4
−60.9
179.5
−64.4
176.4
56.8
−61.2
179.1
−64.8
175.9
56.2
−62.2
−176.3
176.2
54.1
−59.9
179.3
−58.8
57.1
−61.5
−175.7
176.6
54.8
−59.4
−179.5
−57.9
58.5
−2.5
−2.8
177.8
115.7
−63.9
−121.5
58.9
177.7
115.5
−64.1
−121.7
58.7
55.1
56.4
176.9
−67.2
−61.0
60.8
176.7
178.4
58.5
−62.2
−61.2
179.0
58.3
178.0
−65.6
−59.9
61.7
178.1
179.2
59.4
−61.1
−60.6
179.6
59.1
−23.6
−141.9
96.5
151.3
33.1
−22.2
−140.7
97.9
153.2
34.7
121.2
119.0
119.8
116.9
120.3
122.7
120.7
119.7
119.6
122.7
128.5
108.9
118.6
120.4
−88.6
−86.7
3.1
3.3
−177.3
−172.3
7.3
−177.2
−172.5
7.0
55.0
55.6
−164.5
−164.6
−64.8
174.4
59.8
−60.5
179.6
−61.3
178.4
58.5
−64.2
175.2
59.8
−60.4
179.7
−61.3
178.5
58.6
10.7
11.0
15.9
15.9
−168.8
179.4
2.4
4.4
−172.6
−168.5
179.6
2.5
4.2
−172.8

970
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 1 (Continued )
4.2. Atomic charges
Parametera
Isolated
Solute
Parametera
Isolated
Solute
Both Mulliken’s atomic net charges [29] and the natural
NBO/NPA atomic charges [30,31] were calculated. The results are
listed in Table 2.
The comparison between Mulliken’s net charges and the atomic
natural ones is not an easy task since these two methods have quite
different theoretical background. The results show remarkable dif-
ferences between the Mulliken’s and the NBO charges.
The definition of Mulliken’s charges is based on population anal-
ysis. The Mulliken population analysis provides a partitioning of
either the total charge density or an orbital density. The number
of the electrons in the molecule (N) is the integral of the charge
density over the space. N is partitioned for all atoms, the overlap
population is also considered. According to the theory, the overlap
population of atoms A and B is divided between the two atoms in
half-to-half ratio. This is one weak point of the theory. The other
weak point is its strong dependence on the applied basis set. Our
Mulliken’s atomic net charges are comparable since the same basis
set was used for both the isolated and the solute compounds. The
atomic net charge is the difference between the calculated number
of electrons belonging to the atom in the molecule and the number
of electrons of the isolated atom.
ϕ (27,24,37)
ϕ (36,24,37)
ϕ (23,25,26)
ϕ (23,25,34)
ϕ (23,25,35)
ϕ (26,25,34)
ϕ (26,25,35)
ϕ (34,25,35)
ϕ (25,26,31)
ϕ (25,26,32)
ϕ (25,26,33)
ϕ (31,26,32)
ϕ (31,26,33)
ϕ (32,26,33)
ϕ (24,27,28)
ϕ (24,27,29)
ϕ (24,27,30)
ϕ (28,27,29)
ϕ (28,27,30)
ϕ (29,27,30)
110.0
105.8
111.5
109.0
109.8
110.2
110.1
106.2
111.4
111.5
110.9
107.6
107.6
107.6
110.7
111.6
111.5
107.6
107.3
107.9
109.9
106.0
111.5
109.1
109.9
109.9
109.8
106.5
111.3
111.3
110.9
107.7
107.8
107.7
110.6
111.5
111.4
107.7
107.6
107.8
ꢀ (35,25,26,31)
ꢀ (35,25,26,32)
ꢀ (35,25,26,33)
−178.1
61.6
−58.3
−178.2
61.7
−58.2
a
r: bond lengths, in angstroms; ϕ: valence angles in degrees; ꢀ: torsional angles
in degrees.
´
˚
gen atoms. The N10–C12 bond is increased by +0.1 A or
a
The natural atomic charge is based on the theory of natural popu-
lation analysis. The analysis is carried out with natural bond orbitals
(NBO). They are linear combinations of the natural atomic orbitals.
The derivation of a valence-shell atomic orbital (NAO) involves
diagonalization of the localized block of the full density matrix of
a given molecule associated with basis functions on the atom. A
distinguishing feature of NAOs is that they meet the simultane-
ous requirement of orthonormality and maximum occupancy. In a
polyatomic molecule NAOs mostly retain one-center character, and
thus they are optimal for describing the molecular electron density
around each atomic center. Natural bond orbitals are linear com-
binations of NAOs of two bonded atoms. The natural population
analysis satisfies Pauli’s exclusion principle and solves the basis set
dependence problem of the Mulliken’s population analysis.
As seen from Table 2. we regarded NBO charges more impor-
tant. All carbon atoms are around benzene ring rg1 have negative
charges, however, C6 is the least negative one. An other carbon
atom of the five membered ring C12, has a positive charge. Both
are nearest neighbors of N10. The negative charges of the carbon
atoms of the N(C3H7)2 group increase radically with the increas-
ing distance from the N20 atom, e.g. for C22 the charge is −0.273
atomic charge unit (a.ch.u.), for C26 it is −0.710 a.ch.u. The atom
C19 of the rg2 ring in the vicinity of N20 has positive charge, as well.
The strong electron repulsive inductive effects of the NR3 groups in
the positive ion are clearly observable. One can conclude, that N20
affects stronger on its vicinity than N10. The Mulliken net charge
distributions show similar effects. However, the NBO charge of N10
little more. The C4–N10–C11–H48, the C4–N10–C11–H49 and
the C4–N10–C11–H50 torsion angles increased more than 1◦,
in contrast to other torsion angles of this NCH3 group describ-
´
˚
ing the torsion to the C11–N10 bond, decreasing 0.1 A or a bit
more. The situation is similar around N20. The solvent effects
´
˚
of the N20–C19, N20–C22 and N20–C23 bonds are +0.09 A. The
C21–C19–N20–C23, C19–N20–C23–C25 and C22–N20–C23–H38
torsion angles show positive (1.0–2.5◦, absolute value) solvent
effects, while the C17–C19–N20–C23, the N20–C19–C21–H42, the
C19–N20–C23–H38 and the C19–N20–C23–H39 torsion angles
show negative solvent effects to a similar measure.
Especially interesting is the C4–N10–C12–C13–C14–C15 chain.
The corresponding bond lengths are 1.417, 1.346, 1.402, 1.384 and
´
˚
1.416 A, respectively. According to [27] the single C–C bond length
´
´
˚
˚
is about 1.54 A, that of C C one is 1.34 A, the single N–C bond length
´
˚
is 1.42 A, while the N C double bond length is expected according
´
˚
to [28], to be 1.317 A. That means, the C4–N10 bond is a real C–N
one, the N10–C12 bond length is between those for the single and
the double bond lengths, the C12–C13 bond is similarly partly dou-
ble bond, the C13–C14 bond length is like the one for an aromatic
CC bond (see Table 1, e.g. C1–C2 or C5–C6), while the C14–C15 bond
is again partly double bond. The N10 atom has an effect on the ben-
zene ring of the indole; the bonds closer to this atom are shorter
than the others in the ring. All these facts support the existence of
an extended conjugation between the two aromatic rings.
Fig. 2. Numbering of the DPPTVI atoms and rings.

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
971
Table 2
Atomic charges of the DPPTVI cationa.
Serial number
Atom type
Mulliken net charges
NBO charges
Isolated
number
Atom type
Mulliken netcharges
NBO charges
Isolated PCM
Isolated
PCM
PCM
Isolated
PCM
1
2
3
4
5
6
7
8
C
C
C
C
C
C
C
C
C
N
C
C
C
C
C
C
C
C
C
N
C
C
C
C
C
C
C
H
H
H
−0.172
−0.193
−0.160
0.330
−0.164
−0.193
−0.154
0.325
−0.217
−0.261
−0.225
0.152
−0.215
−0.040
−0.103
−0.683
−0.684
−0.332
−0.504
0.343
−0.350
−0.104
−0.144
−0.161
−0.285
−0.165
0.242
−0.380
−0.289
−0.273
−0.285
−0.493
−0.488
−0.710
−0.713
0.259
−0.226
−0.259
−0.237
0.157
−0.219
−0.040
−0.094
−0.661
−0.662
−0.331
−0.483
0.349
−0.344
−0.091
−0.148
−0.162
−0.289
−0.166
0.237
−0.392
−0.294
−0.259
−0.269
−0.472
−0.468
−0.682
−0.686
0.240
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
0.183
0.175
0.195
0.186
0.178
0.191
0.178
0.194
0.197
0.194
0.202
0.189
0.183
0.189
0.184
0.182
0.178
0.227
0.224
0.226
0.184
0.199
0.199
0.202
0.184
0.200
0.188
0.197
0.192
0.199
0.153
0.153
0.156
0.158
0.156
0.157
0.156
0.178
0.179
0.182
0.179
0.181
0.189
0.179
0.187
0.182
0.180
0.210
0.208
0.215
0.169
0.175
0.172
0.177
0.172
0.173
0.181
0.174
0.192
0.178
0.244
0.239
0.259
0.249
0.245
0.263
0.244
0.247
0.258
0.248
0.259
0.256
0.249
0.257
0.252
0.239
0.253
0.265
0.262
0.258
0.250
0.261
0.261
0.263
0.248
0.261
0.259
0.264
0.258
0.265
0.230
0.230
0.241
0.237
0.238
0.249
0.235
0.243
0.251
0.245
0.251
0.256
0.258
0.257
0.261
0.243
0.256
0.259
0.257
0.256
0.245
0.250
0.249
0.252
0.244
0.249
0.263
0.260
0.266
0.262
−0.226
−0.230
0.101
0.111
−0.147
−0.500
−0.496
−0.589
−0.420
0.417
−0.210
−0.188
0.144
−0.215
−0.208
−0.197
0.391
−0.480
−0.204
−0.225
−0.213
−0.317
−0.323
−0.520
−0.521
0.196
−0.097
−0.455
−0.451
−0.560
−0.367
0.409
−0.208
−0.173
0.148
−0.211
−0.203
−0.201
0.383
−0.476
−0.206
−0.178
−0.168
−0.264
−0.268
−0.456
−0.457
0.154
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
0.177
0.171
0.155
0.152
0.239
0.236
0.230
0.228
a
Atomic charge units.
(−0.332 a.ch.u.) is less negative than N20 (−0.380 a.ch.u.), while in
case of the corresponding Mulliken charges the order is opposite.
Comparison of the NBO charges of the isolated and aqueous
solute ions show positive changes in the N10 environment, e.g. the
C9 charge increases by 0.018 a.ch.u., C21 by 0.021 a.ch.u. The N10
charge remains practically unchanged. All carbon charges in the
N(C3H7)2 group exhibit positive changes between 0.014 and 0.027
a.ch.u. The carbon atoms of the vinylydene group became more pos-
itive but remain negatively charged, although this negative charge
is reduced (C13 and C14). One cannot characterize unambiguously
the changes in other carbon atom charges and the hydrogen atom
charges.
For the Mulliken charges the character of the charge variation
shows similar tendencies but the changes are greater. The calcu-
lated dipole moment of the isolated ion is 1.905 D, while that of the
solute ion increases to 2.874 D.
The energy of the isolated ion decreases in the aqueous solution
by 9.191 kJ/mol.
nates of the benzene ring according to the intentions of Fogarasi
and coworkers [32]. One can follow them also for the full indolene
skeleton. However, in this case the value of the G matrix determi-
nant radically decreases. Following the definitions of the internal
coordinates one find the problem of the second benzene ring. Here
one can define only 12 coordinates (3 × 6–6) but 18 ones are nec-
essary. Six new coordinates should be added. We tried to define
them in several forms, however, only one simple form gave non-
zero G matrix determinant (coordinates 91–108), if the coordinates
of the pyrrolidine ring coordinates (coordinates 25–33) were also
defined in the similar simple way. We have to note that if the coor-
dinates were defined in a different way, the G matrix determinant
of the skeleton was zero. The problem of the choice of coordinates
Infrared spectra of DPPVTI
70
60
50
40
Simulated
30
20
10
0
4.3. Vibrational force constants
νCH
The vibrational force constants provide information about
the interatomic forces in the molecule. However, it is a chal-
lenge to extract this information since the molecules in question
with their 60 atoms have 174 vibrational modes and accord-
ingly the force constant matrices have 174 × 174 elements. Of
course, the full force constant matrix was applied in the GF matrix
eigenvector–eigenvalue calculations. For practical use, only the
diagonal elements are presented (see Table 3).
As mentioned above, the values of the applied 12 scale factors
remained between 0.877 and 0.921 (Table 3).
Here we also have to deal with the problem of the definition of
the internal coordinates. The molecules contain two phenolic rings.
The first problem is the indolene ring. One can define the coordi-
-10
4000 3600 3200
1800 1600 1400 1200 1000 800
Measured
600
400
0.6
0.5
0.4
0.3
0.2
0.1
νCH
4000 3600 3200
1800 1600 1400 1200 1000 800
Wavenumber / cm-1
600
400
Fig. 3. Infrared spectra of the DPPVTI compound and its simulation for the isolated
cation.

972
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 3
Diagonal force constants of the DPPTVI cation.
Internal coordinate
Scale factor
Diagonal forceconstantb
Internal coordinate
Scale factor
Diagonal force constantb
Ser. no.
Definitiona
Isolated
Solute
Ser. no.
Definitiona
Isolated
Solute
1
2
3
4
5
6
7
r (2,1)
r (1,3)
r (3,5)
r (5,6)
r (6,4)
r (4,1)
ϕ (2,3,1)
0.877
0.877
0.877
0.877
0.877
0.877
0.906
12.211
7.017
7.444
7.114
15.321
14.376
4.325
11.803
6.816
7.210
6.919
14.794
13.913
4.283
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
ϑ (47,12,14,13)
r (14,13)
ϕ (14,12,13)
ꢀ (14,13,12,10)
r (46,14)
ϕ (46,13,14)
ϑ (46,15,13,14)
r (15,14)
ϕ (15,13,14)
ꢀ (15,14,13,12)
r (16,15)
ϕ (16,14,15)
ꢀ (16,15,14,13)
r (45,16)
ϕ (45,15,16)
ϑ (45,15,21,16)
r (18,15)
ϕ (18,14,15)
ꢀ (18,15,14,13)
r (43,18)
ϕ (43,15,18)
ϑ (43,17,15,18)
r (17,18)
ϕ (17,15,18)
ꢀ (17,18,15,16)
r (44,17)
ϕ (44,18,17)
ϑ (44,18,19,17)
r (19,17)
ϕ (19,18,17)
ꢀ (19,17,18,15)
r (21,19)
ϕ (21,17,19)
ꢀ (21,19,17,18)
r (42,21)
ϕ (42,19,21)
ϑ (42,16,19,21)
r (20,19)
ϕ (20,21,19)
ꢀ (20,19,21,16)
r (22,20)
ϕ (22,19,20)
ꢀ (22,20,19,17)
r (24,22)
ϕ (24,20,22)
ꢀ (24,22,20,19)
r (27,24)
ϕ (27,22,24)
ꢀ (27,24,22,20)
r (41,22)
ϕ (41,20,22)
ꢀ (41,22,20,19)
r (40,22)
ϕ (40,20,22)
ꢀ (40,22,20,19)
r (36,24)
ϕ (36,22,24)
ꢀ (36,24,22,20)
r (37,24)
ϕ (37,22,24)
ꢀ (37,24,22,20)
r (28,27)
ϕ (28,24,27)
ꢀ (28,27,24,22)
r (30,27)
ϕ (30,24,27)
ꢀ (30,27,24,22)
r (29,27)
ϕ (29,24,27)
ꢀ (29,27,24,22)
r (23,20)
0.908
0.905
0.921
0.898
0.901
0.904
0.908
0.905
0.921
0.898
0.905
0.921
0.898
0.901
0.904
0.908
0.905
0.921
0.898
0.901
0.904
0.908
0.905
0.921
0.898
0.901
0.904
0.908
0.905
0.921
0.898
0.905
0.921
0.898
0.901
0.904
0.908
0.925
0.902
0.897
0.925
0.902
0.897
0.905
0.921
0.898
0.905
0.921
0.898
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.925
0.902
0.897
0.905
0.388
6.747
1.652
0.304
5.129
1.090
0.443
6.032
1.614
0.295
7.991
15.977
0.286
5.071
1.017
0.427
8.761
15.887
0.321
5.128
1.012
0.405
15.135
45.924
3.904
5.252
1.035
0.390
8.451
46.383
7.524
7.535
16.839
4.312
5.267
1.030
0.382
7.387
3.095
0.545
4.648
2.601
0.328
3.983
1.447
0.978
4.193
1.341
0.868
4.722
1.083
0.814
4.939
1.061
0.767
4.741
0.929
0.811
4.726
0.967
0.793
4.873
0.883
0.706
4.798
0.893
0.706
4.824
0.904
0.707
4.667
2.492
0.409
3.971
0.398
6.541
1.658
0.283
5.109
1.116
0.443
5.718
1.652
0.286
7.726
15.663
0.281
4.871
1.023
0.435
8.528
15.601
0.320
4.929
1.036
0.414
14.530
44.491
3.864
5.126
1.052
0.390
8.226
44.955
7.498
7.268
16.617
4.347
5.129
1.048
0.389
6.871
3.140
0.532
4.429
2.652
0.342
3.809
1.453
0.983
4.012
1.331
0.867
4.645
1.089
0.815
4.885
1.078
0.772
4.635
0.929
0.813
4.655
0.969
0.796
4.765
0.880
0.708
4.734
0.896
0.713
4.766
0.900
0.713
4.456
2.540
0.391
3.804
−ϕ (4,1,2)
+ϕ (6,2,4)
−ϕ (5,4,6)
+ϕ (3,6,5)
−ϕ (1,5,3)
2ϕ (2,3,1)
−ϕ (4,1,2)
−ϕ (6,2,4)
+2ϕ (5,4,6)
−ϕ (3,6,5)
−ϕ (1,5,3)
ϕ (1,5,3)
−ϕ (3,6,5)
+ϕ (6,2,4)
−ϕ (4,1,2)
ꢀ (5,3,1,2)
−ꢀ (3,1,2,4)
+ꢀ (1,2,4,6)
−ꢀ (2,4,6,5)
+ꢀ (4,6,5,3)
−ꢀ (6,5,3,1)
ꢀ (5,3,1,2)
−2ꢀ (3,1,2,4)
+ꢀ (1,2,4,6)
+ꢀ (2,4,6,5)
−2ꢀ (4,6,5,3)
+ꢀ (6,7,3,1)
ꢀ (5,3,1,2)
−ꢀ (3,1,2,4)
+ꢀ (2,4,6,5)
−ꢀ (4,6,5,3)
r (57,5)
ϕ (57,3,5)
ϑ (57,3,6,5)
r (58,3)
ϕ (58,1,3)
ϑ (58,1,5,3)
r (60,1)
ϕ (60,2,1)
ϑ (60,2,3,1)
r (59,2)
ϕ (59,1,2)
ϑ (59,4,1,2)
r (7,6)
ϕ (7,4,6)
ꢀ (7,6,5,3)
r (12,7)
ϕ (12,6,7)
ꢀ (12,7,6,5)
r (10,4)
ϕ (10,2,4)
ꢀ (10,4,2,1)
r (8,7)
8
0.906
3.833
3.794
9
0.906
0.871
5.786
0.573
5.722
0.578
10
11
12
0.871
0.871
2.410
1.138
2.438
1.146
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.905
0.921
0.898
0.905
0.921
0.898
0.925
0.902
0.897
0.905
0.921
0.898
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.905
0.921
0.898
5.116
0.959
0.424
5.161
0.987
0.428
5.159
0.989
0.432
5.160
0.963
0.386
10.329
39.232
1.193
5.451
22.581
5.165
7.080
17.969
2.130
3.824
1.402
1.130
4.849
0.890
0.696
4.874
0.894
0.708
4.889
0.900
0.693
3.883
1.363
1.165
4.903
0.969
0.427
4.941
0.975
0.423
4.939
0.978
0.429
4.973
0.983
0.389
9.926
38.146
1.206
5.261
22.226
5.262
6.842
17.706
2.154
3.658
1.459
1.154
4.791
0.903
0.706
4.797
0.899
0.715
4.808
0.904
0.699
3.717
1.400
1.199
ϕ (8,6,7)
ꢀ (8,7,6,4)
r (55,8)
ϕ (55,7,8)
ꢀ (55,8,7,6)
r (54,8)
ϕ (54,7,8)
ꢀ (54,8,7,6)
r (56,8)
ϕ (56,7,8)
ꢀ (56,8,7,6)
r (9,7)
ϕ (9,12,7)
ꢀ (9,7,12,10)
ϕ (23,19,20)
ꢀ (23,20,19,17)
r (25,23)

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
973
Table 3 (Continued)
Internal coordinate
Scale factor
Diagonalforceconstantb
Internal coordinate
Scale factor
Diagonal force constantb
Ser. no.
Definitiona
Isolated
Solute
Ser. no.
Definitiona
Isolated
Solute
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
r (53,9)
ϕ (53,7,9)
ꢀ (53,9,7,12)
r (51,9)
ϕ (51,7,9)
ꢀ (51,9,7,12)
r (52,9)
ϕ (52,7,9)
ꢀ (52,9,7,12)
r (11,10)
ϕ (11,4,10)
ꢀ (11,10,4,6)
r (49,11)
ϕ (49.10.11)
ꢀ (49.11.10.4)
r (50,11)
ϕ (50.10.11)
ꢀ (50.11.10.4)
r (48,11)
ϕ (48,10,11)
ꢀ (48,11,10,4)
r (13,12)
ϕ (13,7,12)
ꢀ (13,12,7,6)
r (47,13)
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.925
0.902
0.897
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.905
0.921
0.898
0.901
0.904
4.891
0.902
0.692
4.860
0.893
0.692
4.872
0.884
0.704
4.969
2.069
0.225
4.931
0.984
0.741
4.820
0.968
0.704
4.995
1.016
0.718
6.269
2.519
0.705
5.113
1.090
4.808
0.905
0.699
4.800
0.903
0.703
4.797
0.892
0.712
4.689
2.130
0.223
4.878
0.988
0.742
4.771
0.970
0.710
4.950
1.030
0.715
5.997
2.557
0.685
5.042
1.126
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
ϕ (25,20,23)
ꢀ (25,23,20,19)
r (26,25)
ϕ (26,23,25)
ꢀ (26,25,23,20)
r (39,23)
ϕ (39,20,23)
ꢀ (39,23,20,19)
r (38,23)
ϕ (38,20,23)
ꢀ (38,23,20,19)
r (34,25)
ϕ (34,23,25)
ꢀ (34,25,23,20)
r (35,25)
ϕ (35,23,25)
ꢀ (35,25,23,20)
r (31,26)
ϕ (31,25,26)
ꢀ (31,26,25,23)
r (33,26)
ϕ (33,25,26)
ꢀ (33,26,25,23)
r (32,26)
0.921
0.898
0.905
0.921
0.898
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
0.901
0.904
0.908
1.322
1.090
4.184
1.200
0.841
4.837
1.105
0.807
4.694
1.038
0.805
4.768
0.948
0.789
4.749
0.951
0.787
4.814
0.906
0.703
4.885
0.877
0.698
4.794
0.902
0.697
1.330
1.064
4.007
1.209
0.852
4.754
1.120
0.811
4.641
1.052
0.809
4.699
0.950
0.791
4.693
0.955
0.789
4.726
0.900
0.708
4.780
0.874
0.701
4.722
0.900
0.705
ϕ (32,25,26)
ꢀ (32,26,25,23)
ϕ (47,12,13)
a
r: stretching; ϕ: in-plane deformation; ꢀ: torsion; ϑ: o.o.p. deformation; for the position of the atoms see Fig. 2.
Units: for stretching coordinates 102 N m−1, for deformation coordinates 10−18 N m.
b
resulted in the values of the diagonal elements of the deformation
distributions of several chemically similar internal coordinates are
summarized. That means, the weights of all CH stretchings (ꢁCH),
in-plane deformations (ˇCH) and out-of-plane deformations (ꢂCH)
are grouped for each vibrational mode, respectively. The skeleton
vibrations are similarly grouped, the internal coordinates belong-
ing to the benzene ring of the indolene part, are presented as rg1
(torsions are labeled as ꢀ), the internal coordinates of the other ben-
zene ring as rg2. The cation contains two nitrogen atoms, N10 and
N20. The coordinates including N10 are summarized under CN1,
those with N20 are found under CN2.
force constants of the mentioned critical parts of the molecules.
These extremely high values reflect the tension generated by the
performed definition of the internal coordinates. Consequently, at
this choice of coordinates some of them are nonlinear. However,
here they were regarded as being linear ones. The solvent slightly
moderated these extreme values (see Table 3 for the definition of
the internal coordinates).
4.4. Characterization of the vibrational modes
Only CH vibrations can be regarded as characteristic ones,
first of all the CH stretchings, some in-plane and out-of-plane
deformations. Besides, some CC torsion modes exist. In the
The measured and calculated vibrational frequencies of the
isolated DPPTVI ion are listed in Table 4 . The potential energy
Raman spectra of DPPVTI
60
40
20
0
simulated
νCH
4000
3600
3200
νCH
2800
2400
2000
1600
1200
800
400
0
20000
15000
10000
5000
0
100
80
60
40
20
0
νCH
measured
(exc.: 785 nm)
-20
-40
-60
3100
3000
2900
2800
2700
2600
2500
4000
3600
3200
2800
2400
2000
1600
1200
800
400
0
Wavenumber / cm-1
Fig. 4. Raman spectra of the DPPVTI compound and its simulation for the isolated cation.

974
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 4
Properties of vibrational modes of the isolated DPPTVI cation.
Frequency (cm−1
Measured
)
Potential energy distributiona (%)
Calculated
3097.6
3097.6
3078.4
3078.4
3051.9
3051.9
3051.9
3051.9
3041.1
3041.1
3020.3
3020.3
3012.8
3012.8
3012.8
2983.7
2983.5
2983.5
2983.5
2983.5
2963.4
2963.4
2963.4
2963.4
2926.7
2926.7
2926.7
2926.7
2926.7
2890.8
2890.8
2890.8
2890.8
1614.7
1601.3
1573.4
1568.8
1524.0
1514.4
1514.4
1479.5
1473.2
1461.9
1461.9
1461.9
1461.9
1461.9
1461.9
1439.8
1439.8
1439.8
1439.8
1439.8
1426.5
1426.5
1426.5
1426.5
1415.6
1402.9
1378.4
1365.2
1365.2
1365.2
1354.7
1354.7
1334.7
1334.7
1334.7
1315.4
1289.5
1289.5
1270.4
1270.4
1270.4
3099.0
3094.8
3077.6
3068.8
3059.8
3057.9
3054.9
3050.7
3043.7
3039.1
3029.7
3003.3
3002.5
3001.9
2999.1
2996.3
2993.9
2992.9
2990.7
2981.4
2979.1
2970.9
2948.4
2943.8
2923.5
2921.5
2919.3
2918.7
2916.6
2910.5
2908.4
2907.1
2906.3
1618.2
1586.8
1575.6
1560.5
1522.7
1514.6
1506.3
1472.9
1470.4
1461.3
1458.4
1456.2
1454.4
1453.7
1452.8
1451.1
1448.1
1446.5
1445.0
1438.7
1435.5
1434.5
1430.8
1430.4
1409.2
1392.2
1379.5
1373.5
1370.2
1366.5
1350.2
1347.4
1337.9
1333.8
1331.0
1324.5
1302.2
1283.6
1278.9
1271.4
1270.0
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ꢁ
ˇ
ꢁ
ꢁ
ꢁ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ꢁ
ˇ
ꢁ
ˇ
ˇ
ꢁ
ˇ
ˇ
ˇ
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
rg2
rg1
rg1
rg1
rg2
rg2
rg2
rg2
rg2
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
rg1
CH
rg1
rg1
CN2
CH
CH
CH
CH
CH
CH
CH
rg1
CH
rg2
CH
CH
rg1
CH
CH
CH
98
99
99
99
99
99
99
99
99
99
99
99
99
99
91
99
99
99
99
99
99
99
99
97
99
99
97
99
99
96
99
93
98
52
57
54
10
13
13
49
12
20
23
25
20
23
27
21
23
13
12
16
19
10
17
13
15
11
60
73
87
95
72
99
54
54
52
31
69
71
10
62
63
64
ꢁ
CC
rg1
CC
13
10
17
13
13
14
19
15
26
60
44
68
69
56
76
72
65
70
70
55
66
81
29
31
41
ˇ
ˇ
ˇ
ꢁ
ꢁ
ꢁ
ˇ
ˇ
ꢂ
CH
CH
CH
CC
18
13
13
34
26
16
14
22
13
ˇ
ˇ
ꢁ
rg2
CN2
CN1
rg2
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
ˇ
ˇ
ꢁ
CH
CH
CC
30
25
10
ꢁ
CC
ˇ
ˇ
ˇ
ˇ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ˇ
ꢂ
ˇ
ˇ
ˇ
CN2
CH
CH
CH
ˇ
CC
15
ꢂ
ꢂ
CH
CH
35
15
ꢂ
ꢂ
CH
CH
48
44
ꢂ
ꢁ
ꢂ
ˇ
ꢂ
CH
CN1
CH
CH
CH
24
13
19
29
10
ˇ
ˇ
CH
CH
14
28
ꢁ
ꢂ
ꢂ
ꢂ
CN1
CH
CH
22
11
12
10
ˇ
CH
11
CH

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
975
Table 4 (Continued)
Frequency (cm−1
Measured
)
Potential energy distributiona (%)
Calculated
1243.3
1243.3
1236.0
1236.0
1219.8
1219.8
1191.4
1174.3
1174.3
1156.2
1132.8
1132.8
1116.3
1116.3
1099.7
1096.7
1096.7
1096.7
1096.7
1042.9
1042.9
1019.7
1019.7
992.9
992.9
975.4
953.6
953.6
953.6
953.6
929.8
929.8
929.8
899.0
899.0
890.2
860.4
860.4
860.4
829.0
829.0
829.0
829.0
788.8
771.0
757.3
757.3
738.1
719.6
719.6
719.6
703.2
692.7
678.4
622.4
591.7
568.6
543.6
543.6
525.7
516.8
516.8
479.4
444.3
444.3
425.3
406.7
406.7
406.7
338.9
338.9
324.3
300.7
300.7
300.7
1261.8
1254.6
1238.8
1231.0
1226.6
1221.1
1191.3
1173.7
1168.8
1160.8
1137.9
1132.8
1118.0
1112.5
1098.8
1097.2
1090.5
1083.9
1075.0
1067.2
1042.2
1022.1
1008.6
1004.3
993.4
987.8
963.4
956.0
950.0
947.4
921.9
919.8
917.7
915.8
907.4
890.1
875.2
860.7
848.0
836.6
831.0
828.5
817.2
794.6
763.7
762.7
755.1
733.3
719.9
717.5
713.5
702.4
689.0
668.3
617.9
604.5
570.0
541.5
539.0
528.6
513.7
510.4
499.1
452.7
447.8
421.5
407.5
391.7
370.7
351.4
345.7
332.1
306.8
305.1
301.1
ꢁ
ˇ
ˇ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢀ
CC
33
67
63
11
10
27
15
12
23
10
18
12
35
50
26
28
73
25
17
34
41
65
12
62
61
74
54
84
10
16
57
16
15
11
89
28
35
21
15
96
84
45
34
11
78
13
28
81
63
24
11
73
12
18
14
35
17
14
44
13
29
31
10
10
48
15
56
23
41
12
32
10
13
16
12
ˇ
ꢂ
ꢂ
ˇ
ˇ
ˇ
ꢁ
ˇ
ˇ
ꢁ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ꢂ
ˇ
ꢁ
ˇ
ˇ
ˇ
ꢁ
CH
CH
CH
CH
CH
CH
CC
CH
CH
CC
CH
CH
CH
CH
CH
CH
CH
CC
45
18
14
64
52
36
27
63
30
19
76
36
37
41
49
49
16
13
16
13
25
16
18
22
19
17
23
CH
CH
rg2
CC
ꢂ
CH
CH
12
33
CC
rg1
rg2
CN2
rg1
rg1
CC
rg2
CC
rg1
rg1
CH
CC
CN2
CC
rg1
CC
rg1
CC
rg1
CH
rg2
CH
CN2
CN2
CH
CC
CH
CC
CH
CC
ˇ
ꢂ
ˇ
CH
CH
18
26
ꢂ
CH
19
ˇ
ꢁ
ꢁ
ꢁ
ˇ
ꢁ
ꢁ
ꢁ
ˇ
ꢁ
ꢁ
ꢁ
ꢁ
ˇ
ꢁ
ꢂ
ꢁ
ꢁ
ꢂ
ꢁ
ˇ
ꢁ
ꢂ
ꢁ
ꢁ
ꢁ
ꢁ
ꢂ
ꢂ
ꢁ
ꢁ
ꢀ
ˇ
ˇ
ˇ
CH
CH
CH
42
41
36
CC
CC
CH
CH
CN1
CH
CH
CH
rg2
ꢁ
CC
19
19
ˇ
CH
26
ˇ
ˇ
ꢂ
ˇ
ˇ
CH
ꢂ
ˇ
CH
CH
57
14
ꢂ
ꢂ
ꢂ
CH
CH
CH
42
40
53
ˇ
ꢂ
ˇ
CH
CH
CH
34
59
11
ˇ
ˇ
ˇ
ˇ
CC
CH
CH
CH
27
36
36
32
ˇ
ꢂ
ꢂ
ꢂ
CH
CH
CH
CH
16
12
23
25
CC
CC
CC
CH
CH
CC
ˇ
ˇ
ꢂ
CH
rg2
CH
12
16
81
ꢂ
ꢁ
CH
CC
28
21
rg2
rg2
CH
CH
rg1
CH
rg1
CH
rg2
rg2
rg1
rg1
rg2
rg1
rg2
CC
rg1
rg1
CN2
rg1
rg1
rg2
rg1
rg2
rg2
rg2
rg2
CN2
CN1
CN1
rg2
CN1
CN2
ꢂ
ˇ
ˇ
ꢂ
ꢀ
ˇ
ˇ
ꢀ
ꢂ
ꢁ
CH
CN1
51
13
ꢁ
CC
15
ˇ
CC
12
ꢀ
ꢂ
ꢁ
CC
CH
CN2
15
65
13
ˇ
CC
14
ꢂ
ꢁ
CH
CC
11
18
ꢁ
ꢀ
ˇ
ꢀ
rg1
rg2
rg2
CC
CN1
CC
CC
rg1
CC
19
14
70
22
15
28
21
12
22
11
25
23
14
33
ˇ
ꢀ
rg2
CC
10
37
ˇ
CC
10
ꢁ
ˇ
ˇ
ꢁ
ꢀ
ꢁ
ˇ
ˇ
ˇ
ꢀ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
ˇ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
CC
30
27
CN1
ˇ
ꢀ
CC
24
15
CC
rg2
CN2
CN1
rg2
ˇ
ˇ
CN2
CC
13
21
CN2
ˇ
ꢀ
ꢀ
ˇ
CC
17
ꢁ
CN2
CN1
CC
10
12
33
11
14
15
15
45
ˇ
ꢀ
CN2
CC
11
20
ˇ
CC
17
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ˇ
CC
ꢀ
ꢀ
ˇ
ꢀ
ꢂ
CC
CC
CC
CC
CH
27
54
29
27
17
ˇ
ꢀ
ꢀ
CN1
CN1
CC
ˇ
CC

976
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 4 (Continued)
Frequency (cm−1
Measured
)
Potential energy distributiona (%)
Calculated
300.7
257.4
257.4
257.4
230.6
230.6
215.4
215.4
215.4
198.2
186.2
159.6
151.6
145.0
135.4
113.0
96.7
80.5
73.0
61.0
52.9
46.1
31.0
20.8
17.5+
280.7
262.0
258.5
249.4
240.9
228.9
222.3
214.2
208.8
188.7
177.3
152.0
144.2
137.8
128.2
107.1
91.7
76.4
69.2
57.9
50.2
43.8
29.6
19.7
16.6
ˇ
ˇ
ˇ
ˇ
ˇ
ꢂ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ˇ
ꢀ
CN2
CC
CC
CC
CC
CH
CN1
CC
12
11
19
17
16
68
17
21
41
20
13
23
56
13
11
15
13
17
37
43
15
78
47
21
47
ˇ
ꢂ
ꢀ
ꢀ
ꢀ
CC
CH
CC
CC
CC
43
62
17
18
13
ꢀ
CC
15
ꢂ
ꢂ
ꢂ
CH
CH
CH
31
13
41
ꢂ
CH
26
ꢂ
ꢂ
ꢂ
ˇ
ꢀ
CH
CH
CH
CC
CN2
CC
44
39
38
23
11
31
CC
rg2
rg2
CC
ꢂ
ꢁ
CH
CC
13
13
ˇ
ꢀ
CC
CC
17
43
ꢀ
CC
19
ꢀ
CC
CN2
rg1
rg1
rg2
CN2
CN2
CN2
CN2
CC
ꢀ
ꢀ
ˇ
ꢀ
ꢀ
ˇ
ˇ
ˇ
CC
CN1
CC
CN2
CC
CC
44
37
10
13
58
10
17
10
ꢀ
ꢀ
ˇ
CC
CC
CC
20
31
13
ꢀ
ꢀ
ꢀ
CC
CC
CC
39
32
62
CC
CC
CC
rg2
rg2
ꢀ
ꢀ
ꢀ
CC
CN2
CC
22
16
38
ꢀ
CC
58
ꢀ
a
Distributions not less than 10%; ꢁ: stretching; ˇ: in-plane deformation; g: out-of-plane deformation; ꢀ: torsion; rg1:benzene ring in indolene; rg2: the other aromatic
ring; N1 N10; N2 N20 (Fig. 2). The mean deviation between the measured and calculated frequencies is 6.78 cm−1 and 1.18%.
1620–1500 cm−1 range two vibrational modes contain about
50 PED% the ꢁrg1 stretching coordinates (measured frequen-
cies 1601.3 and 1573.4 cm−1), and similarly two have about 50
PED % ꢁrg2 stretching modes (measured frequencies 1614.7 and
1514.4 cm−1). There are not characteristic vibrational modes for
CN1 and CN2 type stretchings. These stretching coordinates partic-
ipate by 10–25 PED% in some vibrational modes.
Table 5 contains the calculated fundamental frequencies for
the DPPTVI cation in aqueous solution. For comparison similar
results for the isolated cation are also shown. The deviations
from the isolated cation frequencies are mostly towards lower
frequencies. In the region of the CH stretchings these deviations
are 30–40 cm−1, in the mentioned region of the rg stretchings the
frequencies decease by about 20 cm−1. In general, the weights of
PED contribution of the ring stretching coordinates decreased. The
ꢁrg1 contribution decreased by 17% at the calculated frequency of
1569.9 cm−1 frequency, and the ꢁrg2 contribution – by 8% at the
frequency of 1440.9 cm−1. In case of the frequencies 1593.2 cm−1
and 1556.1 cm−1 this decrease was small, only 3% and 1% for ꢁrg2
and ꢁrg1, respectively (see also Table 4).
were corrected for the excitation wavelength of the experimental
spectrum, according to [33]. The equation for the frequency of ith
vibrational mode (ꢁi) has the following form:
(ꢁ0 − ꢁi)4
Ii = f
Si
ꢁi 1 − exp(−(hcꢁ /kT))
[
]
i
with excitation frequency ꢁ0 (in our case corresponding to ꢃ = 785
nm), temperature T (here 293 K), Planck constant h, Boltzmann con-
stant k and speed of light in vacuum c; f is an arbitrary constant valid
for all vibrational frequencies of the molecule. This correction bring
the calculated spectra closer to the measured ones, however, other
problems are similar to those mentioned for the infrared spectra.
The low sensitivity of the applied CCD detector in the NIR region
causes the very low SNR over 2000 cm−1. Here the deviations in
intensities between the experimental and calculated spectra are
greater than in case of the IR spectra.
80
70
60
50
40
30
20
10
0
Simulated infrared spectra of DPPVTI
4.5. Vibrational spectra
Isolated
Solute
The measured and simulated infrared spectra are presented
in Fig. 3. The intense and more or less characteristic bands are
marked. The resolution of the most intense band showed that the
1514.4 and 1524.0 cm−1 bands overlap in the experimental spec-
trum (see Table 3 and Figs. 3 and 4). The features in the simulated
infrared spectrum differ in intensity and width from the experi-
mental one. The reason is the difference in the conditions. Namely,
the experimental spectra were measured in solid state, in chemical
environment. The quantum chemical calculations refer to isolated
molecule or to aqueous solution (PCM), and are based on the scaled
computed frequencies and the calculated infrared intensities for
the normal modes. Besides, the simulated spectra were calculated
with constant band width for all normal modes.
-10
3000 2800 1600 1400 1200 1000 800 600 400 200
Wavenumber / cm-1
0
The measured and simulated Raman spectra are introduced in
Fig. 4. The quantum chemically calculated Raman intensities (Si)
Fig. 5. Comparison of the simulated infrared spectra of the isolated and the solute
DPPVTI.

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
977
Table 5
Properties of vibrational modes of the DPPTVI cation in aqueous solution.
Frequency (cm−1
Calculateda
)
Potential energy distributionc (%)
Calculatedb
3099.0
3094.8
3077.6
3068.8
3059.8
3057.9
3054.9
3050.7
3043.7
3039.1
3029.7
3003.3
3002.5
3001.9
2999.1
2996.3
2993.9
2992.9
2990.7
2981.4
2979.1
2970.9
2948.4
2943.8
2923.5
2921.5
2919.3
2918.7
2916.6
2910.5
2908.4
2907.1
2906.3
1618.2
1586.8
1575.6
1560.5
1522.7
1514.6
1506.3
1472.9
1470.4
1461.3
1458.4
1456.2
1454.4
1453.7
1452.8
1451.1
1448.1
1446.5
1445.0
1438.7
1435.5
1434.5
1430.8
1430.4
1409.2
1392.2
1379.5
1373.5
1370.2
1366.5
1350.2
1347.4
1337.9
1333.8
1331.0
1324.5
1302.2
1283.6
1278.9
1271.4
1270.0
3059.9
3058.3
3050.5
3027.4
3018.2
3013.4
3008.5
2998.2
2997.7
2989.0
2985.8
2982.8
2980.7
2976.8
2976.1
2974.0
2970.2
2960.3
2960.2
2956.7
2955.4
2945.2
2926.4
2915.3
2911.8
2902.3
2902.0
2899.7
2899.6
2892.6
2890.3
2887.9
2883.3
1593.2
1569.9
1556.1
1539.8
1497.9
1490.9
1483.2
1472.8
1464.0
1458.8
1457.7
1454.9
1453.5
1452.2
1450.7
1450.0
1444.6
1443.3
1439.5
1439.0
1436.3
1433.9
1428.6
1418.8
1403.0
1386.2
1377.0
1370.6
1366.1
1361.6
1354.3
1344.0
1334.1
1327.1
1315.1
1309.4
1302.2
1282.2
1278.8
1274.7
1263.4
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ꢁ
ꢁ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ˇ
ꢁ
ꢁ
ˇ
ˇ
ˇ
ꢁ
ꢁ
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
rg2
rg1
rg1
rg1
rg2
rg2
CN1
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
rg2
CH
CH
CH
rg1
rg1
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
rg2
rg1
CH
CH
CH
CC
97
99
99
99
99
99
99
99
99
99
99
98
98
99
99
99
99
99
99
99
99
99
99
98
99
98
97
99
99
99
97
99
91
49
40
53
10
26
41
13
16
12
20
22
19
17
25
24
20
18
10
12
16
12
18
22
32
60
55
86
84
97
58
99
57
62
72
35
44
58
60
71
13
14
ꢁ
ˇ
ˇ
ꢁ
ꢁ
ˇ
ꢁ
ˇ
ˇ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ˇ
ꢂ
ꢂ
ꢂ
ˇ
ˇ
CC
rg1
CC
rg2
CN2
rg2
CC
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
15
23
18
12
16
12
20
25
19
54
66
63
63
67
65
78
63
70
14
73
75
81
35
46
ˇ
ˇ
ˇ
ꢁ
ˇ
ˇ
ˇ
ꢂ
ꢂ
CH
CN1
CH
CC
CH
CH
CC
21
12
14
28
30
22
17
42
59
ˇ
ˇ
CH
CH
13
35
ˇ
CH
27
CH
CH
ꢂ
ꢂ
CH
CH
59
13
ꢂ
CH
10
ꢂ
ꢂ
ꢂ
ˇ
ꢁ
CH
CH
CH
CH
CN1
22
23
12
10
10
ˇ
ˇ
CH
CH
15
44
ꢂ
ꢂ
ˇ
ꢁ
CH
CH
CH
CN1
10
21
59
18
rg1

978
F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
Table 5 (Continued)
Frequency (cm−1
Calculateda
)
Potential energy distributionc (%)
Calculatedb
1261.8
1254.6
1238.8
1231.0
1226.6
1221.1
1191.3
1173.7
1168.8
1160.8
1137.9
1132.8
1118.0
1112.5
1098.8
1097.2
1090.5
1083.9
1075.0
1067.2
1042.2
1022.1
1008.6
1004.3
993.4
987.8
963.4
956.0
950.0
947.4
921.9
919.8
917.7
915.8
907.4
890.1
875.2
860.7
848.0
836.6
831.0
828.5
817.2
794.6
763.7
762.7
755.1
733.3
719.9
717.5
713.5
702.4
689.0
668.3
617.9
604.5
570.0
541.5
539.0
528.6
513.7
510.4
499.1
452.7
447.8
421.5
407.5
391.7
370.7
351.4
345.7
332.1
306.8
305.1
301.1
1255.9
1251.9
1237.8
1230.2
1226.9
1215.2
1182.8
1165.5
1163.4
1150.0
1130.3
1123.6
1112.0
1102.3
1094.1
1089.9
1087.5
1078.0
1068.9
1058.0
1042.8
1005.4
998.3
995.7
988.0
983.2
959.5
952.1
949.6
939.0
926.6
923.2
918.6
912.3
905.9
884.0
869.0
858.4
845.9
839.2
836.1
817.9
811.2
793.9
768.4
761.2
749.7
731.2
719.0
718.3
709.4
701.5
685.7
667.7
618.8
605.1
570.9
540.9
537.5
525.4
512.3
506.9
499.0
453.2
450.2
420.2
407.8
387.7
369.3
349.1
345.8
332.9
308.0
306.1
299.0
ꢁ
ˇ
ˇ
ꢁ
ˇ
ˇ
ꢁ
ꢁ
ꢁ
ꢁ
ˇ
ꢁ
ˇ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ˇ
ꢁ
ꢁ
ˇ
ꢁ
ꢁ
ꢁ
ꢂ
ꢂ
ꢁ
ꢂ
ꢂ
ꢁ
ꢁ
ꢂ
ꢁ
ꢁ
ꢁ
ꢁ
ꢂ
ꢂ
ꢁ
ꢁ
ꢂ
ꢂ
ˇ
ꢁ
ꢀ
rg1
CH
CH
rg2
CH
10
55
63
16
53
12
12
12
19
10
12
20
33
27
23
15
28
22
17
12
46
11
16
66
74
55
54
89
84
12
83
84
30
21
87
31
31
16
13
89
96
60
34
83
97
22
13
10
56
23
16
74
30
17
14
36
18
45
18
18
30
17
10
24
48
15
53
20
40
14
29
12
14
18
16
ꢁ
CC
CH
CH
CH
CH
CC
CC
CH
CH
CC
CH
CH
CH
CH
CC
CH
CH
CC
CC
CC
CH
CC
CN1
CH
CH
CC
rg2
31
19
15
52
16
33
30
55
35
19
33
75
30
45
10
52
56
14
10
31
22
65
16
14
14
10
24
ˇ
CH
33
ꢂ
ꢂ
ˇ
ꢂ
ꢁ
rg1
rg1
rg2
CN2
rg1
CH
rg1
rg2
CC
rg1
CC
rg1
CC
CN2
CN2
rg1
CN2
rg1
CH
ˇ
ˇ
CH
CH
28
33
ꢂ
CH
10
ꢁ
ˇ
ˇ
ꢁ
ˇ
ˇ
ˇ
ˇ
ꢁ
ˇ
ˇ
ˇ
ꢁ
ꢂ
ˇ
ꢂ
CH
CH
CH
19
26
16
ꢂ
ˇ
CH
CH
11
42
ˇ
ˇ
ˇ
CH
CC
CH
44
11
37
ˇ
ˇ
CH
CH
40
31
ꢁ
ˇ
ꢁ
ˇ
ꢁ
CH
CC
16
15
ꢁ
ꢂ
ˇ
ꢁ
CC
rg1
rg2
CH
CH
rg2
CH
CH
CC
CC
CH
CC
CC
CC
CC
CH
CH
CC
rg2
CH
ˇ
ˇ
CH
CH
16
18
ˇ
ꢁ
CN2
25
ˇ
CH
24
ˇ
ˇ
CH
CC
53
19
ꢂ
ˇ
CH
CH
12
19
ꢂ
CH
10
ˇ
ˇ
ˇ
ˇ
CC
CH
CH
CH
27
33
38
33
ˇ
ꢂ
ꢂ
ꢂ
CH
CH
CH
CH
15
14
29
24
ꢂ
ˇ
CH
rg2
11
16
ꢁ
CC
23
CH
CH
ꢂ
ˇ
ꢂ
ꢀ
ꢂ
ˇ
CH
rg1
CH
CC
CH
rg2
37
21
77
14
60
10
rg1
rg1
rg1
CH
rg1
rg2
rg1
rg1
rg2
rg1
rg2
rg1
CC
rg1
CN2
rg1
rg1
CN2
rg1
rg2
rg2
rg2
rg2
CN1
CN1
CN1
rg2
CN1
CN2
ꢁ
ꢂ
ꢁ
CN1
CH
14
11
13
ꢁ
CC
18
ˇ
ˇ
CC
CC
12
10
ꢀ
ˇ
ˇ
ꢀ
ˇ
ꢀ
ꢁ
ˇ
ˇ
ꢀ
ꢁ
ꢁ
ˇ
ˇ
ꢁ
ˇ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
CN2
ˇ
ꢁ
CC
CC
14
18
ˇ
ꢀ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ꢀ
ꢀ
ˇ
ꢁ
ˇ
ˇ
ˇ
ꢀ
ˇ
ˇ
ˇ
rg2
rg2
rg2
CC
CN1
CN1
CC
CN1
CC
rg2
rg1
CC
CN1
rg2
CC
CN2
CN1
CC
11
14
69
22
12
10
32
30
25
18
14
22
14
35
10
13
11
24
19
14
16
19
42
ꢁ
ꢀ
CN2
CC
11
38
ˇ
ꢀ
CC
CC
29
22
ˇ
CC
20
ꢀ
ꢀ
CN2
rg2
13
19
ˇ
ˇ
CC
CN2
10
12
ˇ
CC
16
ˇ
ꢀ
ꢀ
ꢀ
ꢀ
ˇ
ꢀ
ꢂ
CN2
CC
CC
CC
CC
CC
CC
CH
11
19
19
18
52
28
30
20
ˇ
CC
16
CC
CN1
CN1
CC
ꢀ
ˇ
CC

F. Billes et al. / Spectrochimica Acta Part A 78 (2011) 967–980
979
Table 5 (Continued)
Frequency (cm−1
Calculateda
)
Potential energy distributionc (%)
Calculatedb
280.7
262.0
258.5
249.4
240.9
228.9
222.3
214.2
208.8
188.7
177.3
152.0
144.2
137.8
128.2
107.1
91.7
76.4
69.2
57.9
50.2
43.8
29.6
19.7
16.6
281.0
264.1
258.2
249.8
243.6
228.2
224.2
217.7
208.8
187.7
176.1
151.6
143.5
135.5
124.8
105.3
91.7
77.3
71.3
56.0
50.4
40.6
29.8
18.6
15.2
ˇ
ꢂ
ˇ
ˇ
ˇ
ꢂ
ꢂ
ˇ
ˇ
ꢀ
ˇ
ˇ
ˇ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
CN2
CH
CC
CN2
rg1
CH
CH
CN1
CC
rg2
rg2
CC
13
68
21
10
10
72
64
11
54
23
14
22
12
15
10
18
11
18
38
26
26
80
12
20
43
ˇ
CC
44
ꢀ
CC
14
ꢀ
ˇ
ˇ
CC
CC
CC
22
19
17
ꢂ
ꢀ
ꢀ
CH
CC
CC
20
11
11
ꢂ
ꢂ
CH
CH
47
39
ꢂ
ꢂ
ˇ
ꢀ
ꢀ
ꢀ
ˇ
ꢀ
ˇ
ꢀ
ꢀ
ˇ
ꢀ
CH
CH
CC
CN2
CC
47
25
21
11
31
54
10
32
10
13
54
10
51
18
ꢀ
ꢁ
CC
CC
10
15
ꢂ
ˇ
CH
CC
13
18
ꢀ
CC
17
CC
CC
CN1
rg1
rg1
rg2
CN2
CN2
CN2
CN2
CC
CN2
CN1
CC
CN2
CC
CC
CC
CC
ꢀ
ꢀ
ꢀ
ˇ
CN2
CC
CC
18
29
32
12
ꢀ
ꢀ
CC
CC
36
47
CC
ꢀ
ꢀ
CC
CC
40
43
ˇ
rg2
rg2
rg2
ˇ
ꢀ
ꢀ
CC
CN2
CC
45
18
40
ꢀ
ꢀ
CC
CC
22
55
ꢀ
a
For the isolated DPPTVI cation (for comparison).
For the DPPTVI cation in aqueous solution.
Distributions not less than 10%; ꢁ: stretching; ˇ: in-plane deformation; g: out-of-plane deformation; ꢀ: torsion; rg1: benzene ring in indolene; rg2: the other aromatic
b
c
ring; N1 N10; N2 N20 (Fig. 2).
The simulated infrared spectra of the isolated and the solute
cations are compared in Fig. 5. At the first glance one can observe
that most of the bands are shifted towards lower frequencies.
This fact as well as the great changes in band intensities below
1400 cm−1 are related to the solvent effect. There are several bands
in this region with lower or higher contributions of the NC stretch-
ing and deformation bands sensitive to the effect of the polar
solvent (see Tables 4 and 5).
The simulated Raman spectra of the isolated and solute cations
are presented in Fig. 6. Here the low frequency shifts of the bands
under the solvent effect are also observable. Besides−, 1changes of a
different sort are also revealed. A shoulder 1380 cm is resolved
in the solution, while the twin peaks near 1270 cm−1 merge into
one band due to the solvent effect.
5. Conclusions
The solvent effect on the optimized geometic parameters is
small, it is important only in the environment of the nitrogen atoms.
The optimized geometry proves the conjugation between the two
aromatic systems. In spite of the extended conjugation between
the two aromatic rings they are not coplanar.
The solvent effect caused drastic changes in the atomic net
charges for several atoms, considering both NBO and Mulliken
charges, respectively.
There arose sever problems in the definition of the internal
coordinates since the cation contains two aromatic rings without
common atom. The force constants reflect the definition of the
internal coordinates, their high values point out these difficulties
(internal tensions).
The potential energy distributions show the absence of char-
acteristic skeletal vibrational modes. Only ring stretching modes
have about 50% contribution. This is also reflected in the experi-
mental and simulated spectra. The solvent effect on the simulated
spectra is strong. Both frequency shifts and intensity changes were
calculated.
Simulated Raman spectra of DPPVTI
80
70
60
Isolated
Solute
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50
40
30
20
10
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