Arylmethylene-1,3-indandione based molecular glasses: Third order optical non-linearity

Article abstract of DOI:10.1016/j.dyepig.2012.03.011

The synthesis and new optical features of three indan-1,3-dione class structures is reported. The simple arylmethylene-1,3-indandione structure 2-(4-diethylaminobenzylidene)indan-1,3-dione was used to design two linked structures: 1,3-bis-{3-hydroxy-4-[4-diethylamino-1-(1,3-dioxoindan-2- ylmethylene)benzen-3-yloxy]-1-thiabuthyl}benzene and 4,4′-bis-{{3-hydroxy- 4-[4-diethylamino-1-(1,3-dioxoindan-2-ylmethylene)benzen-3-yloxy]-1-thiabutyl} phenyl}sulfide. In contrast to the simple compound, which readily crystallized, the linked derivatives remained in an amorphous phase and are considered as molecular glasses with respective glass transition temperatures 88 and 100°C. For non-linear optical investigations samples were prepared as a guest-host system in polycarbonate matrix (10%). The Maker-fringe technique was used to investigate the third harmonic generation at a wavelength of 355 nm (YAG laser). Third-order non-linear susceptibility χ⁽³⁾ values were extracted 5.75·10^-21 m² V^-2, 8.60·10^-21 m² V^-2, 16.85·10 ^-21 m² V^-2 for these respective indandiones while modeling the experimental results. To evaluate the susceptibility of the indan-1,3-dione derivatives third harmonic generation a comparative experiment for a reference azodye in polycarbonate was performed. The results show an important feature - higher molecular second order hyperpolarizability for the linked structures. NMR, MS, IR, UV-VIS, XRD and elemental analysis were used to structurally characterize the new compounds and ellipsometry was applied to interpret the non-linear optical results.

Full text of DOI:10.1016/j.dyepig.2012.03.011

Dyes and Pigments 95 (2012) 33e40
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Arylmethylene-1,3-indandione based molecular glasses: Third order
optical non-linearity
a
a
,
b
b
c
*
ꢀ ꢁ
ꢀ
ꢀ
_
G. Seniutinas , R. Tomasiunas , R. Czaplicki , B. Sahraoui , M. Daskeviciene ,
c
d
ꢀ
V. Getautis , Z. Balevicius
a
_
Institute of Applied Research, Vilnius University, Sauletekio 10, LT-10223 Vilnius, Lithuania
b LUNAM Université, Université d’Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 2 bd Lavoisier, 49045 Angers cedex, France
c
_
Kaunas University of Technology, Radvilenu pl. 19, LT-50270 Kaunas, Lithuania
d Center for Physical Sciences and Technology, Savanoriu av. 231, 02300 Vilnius, Lithuania
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and new optical features of three indan-1,3-dione class structures is reported. The simple
arylmethylene-1,3-indandione structure 2-(4-diethylaminobenzylidene)indan-1,3-dione was used to
design two linked structures: 1,3-bis-{3-hydroxy-4-[4-diethylamino-1-(1,3-dioxoindan-2-ylmethylene)
benzen-3-yloxy]-1-thiabuthyl}benzene and 4,40-bis-{{3-hydroxy-4-[4-diethylamino-1-(1,3-dioxoindan-
2-ylmethylene)benzen-3-yloxy]-1-thiabutyl}phenyl}sulfide. In contrast to the simple compound, which
readily crystallized, the linked derivatives remained in an amorphous phase and are considered as
molecular glasses with respective glass transition temperatures 88 and 100 ꢀC. For non-linear optical
investigations samples were prepared as a guest-host system in polycarbonate matrix (10%). The Maker-
fringe technique was used to investigate the third harmonic generation at a wavelength of 355 nm (YAG
Received 4 January 2012
Received in revised form
8 March 2012
Accepted 9 March 2012
Available online 28 March 2012
Keywords:
Indan-1,3-dione derivatives
Linked structures
laser). Third-order non-linear susceptibility c(3) values were extracted 5.75$10ꢁ21 m2
V
ꢁ2, 8.60$10
Molecular glass
ꢁ21
m2
V
ꢁ2, 16.85$10ꢁ21 m2 Vꢁ2 for these respective indandiones while modeling the experimental
Third harmonic generation
Third order non-linear susceptibility
Polycarbonate
results. To evaluate the susceptibility of the indan-1,3-dione derivatives third harmonic generation
a comparative experiment for a reference azodye in polycarbonate was performed. The results show an
important feature - higher molecular second order hyperpolarizability for the linked structures. NMR,
MS, IR, UVeVIS, XRD and elemental analysis were used to structurally characterize the new compounds
and ellipsometry was applied to interpret the non-linear optical results.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
[2e4]. Association at high concentration and photo oxidation of
betaines motivated the search for new indandione derivatives.
The development of advanced materials for photonic applica-
tions is still a challenging issue. Among new trends, such as inor-
ganic nanostructures or quasi-crystals, organic non-linear optical
materials deserve special attention due to their variety and flexi-
bility for structural modifications, relative high susceptibilities and
easy integration with optical devices. Frequency conversion is
a very important feature for non-linear optical microscopy, nano-
optic applications. Indandiones are already well-established
materials in photophysics [1]. First manifestation of high optical
non-linearity appeared as second harmonic generation in indan-
dione-1,3 pyridinium betaines, where photoinduced intra-
molecular electron transfer, large change in dipole moment in the
excited state and considerable hyperpolarizability were obtained
Manifesting reduced association within a matrix dimethylamino-
benzylidene-1,3-indandione (DMABI) showed increased optical non-
linearity e second harmonic generation e measured by both all-
optical and corona poling [5,6]. LangmuireBlodgett layers of 2-(p-
N-hexadecyl-N-methylamino)benzylidene-1,3-indandione produced
as alternate chromophore-spacer films having definite orientation to
the surface and generating harmonics revealed a model system for
designing strong non-linear optical complexes [7]. Our task was to
proceed further in the direction of the well-investigated group of
DMABI. The methyl group, used to alkylate the amino group, was
exchanged with an ethyl group since linking two compounds
together with a spacer is more complicated in the first case.
Furthermore, the simple arylmethylene-1,3-indandione structure 2-
(4-diethylaminobenzylidene)indan-1,3-dione was used to design two
linked amorphous structures. This new condition focused our
efforts to investigate their non-linear optical properties. Basically
flat in an unexcited state indan-1,3-dione class molecules have
* Corresponding author.
ꢀ ꢁ
E-mail address: rolandas.tomasiunas@ff.vu.lt (R. Tomasiunas).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.03.011

34
G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
a large dipole moment [6]. The magnitude of the dipole moment
and it’s change under excitation significantly depends on the
substitution pattern. Having more rotational degree of freedom
these molecules manifest torsion motion. Twisting around a single
bound is responsible for relaxation dynamics and fluorescence
properties. It was concluded that linked arylmethylene-1,3-
indandione derivatives prevents or significantly slows down
some non-radiative relaxation pathways [8]. This we valuated as
an advantage for enhancement of non-linear optical properties,
i.e. harmonic generation.
(dd, JMA ¼ 11.2 Hz, JMX ¼ 5.6 Hz, (HM), 1H, another of CH2O protons);
0
0
0
3.47e3.36 (m, 5H, CHO, NCH2); 2.95 (dd, JA M ¼ 4.5 Hz, JA X ¼ 4.5 Hz
0
0 0
(HA ), 1H, one proton of CH2O of oxirane); 2.81 (dd, JM A ¼ 4.5 Hz,
0
0
JM X ¼ 2.7 Hz, (HM ), 1H, another proton of CH2O of oxirane); 1.22 (t,
J ¼ 7.1 Hz, 6H, CH3).
APCI-MS: m/z (%): 250 [M þ H]þ (100).
Elemental analysis. Calcd. for C14H19NO3 (%): C 67.45; H 7.68; N
5.62. Found (%): C 67.38; H 7.59; N 5.42.
In this work we extend our non-linear optical knowledge
about new material e indan-1,3-dione based molecular glasses e
by investigating third order optical non-linearity. Routes of
synthesis, chemical structure investigation using spectroscopy
and X-ray diffraction, experimental third harmonic generation
(THG) e a powerful and almost background free non-linear
optical method e and theoretical modeling are presented. Prob-
lems and ideas concerned with architecture, chemical properties
and physical properties toward higher second order hyper-
polarizability are raised.
2.3. 4-Diethylamino-2-oxiranylmethoxy-1-(1,3-dioxoindan-2-
ylmethylene)benzene (2, C23H23NO4)
1,3-indandione (5.0 g, 34 mmol) and compound 1 (8.56 g,
34 mmol) were dissolved in 90 mL of ethanol. The solution was left
stirring at room temperature over night. Obtained red crystals were
filtered off and washed with 2-propanol and diethyl ether. The yield
was 92% (12 g); m.p.: 148.5e150 ꢀC (THF: 2-propanol, 1:1).
IR (KBr),
n
, cmꢁ1: 3033 (CHarom), 2969, 2962, 2869 (CHaliph),
1708, 1660 (C]O), 1547, 1512 (C]C), 1278, 1252, 1209, 1072
(CeOeC); 810, 742 (CH]CH of 1,2-di- and 1,2,4-trisubstituted
benzenes).
2. Samples
1H NMR (300 MHz, CDCl3,
d
, ppm): 9.34 (d, J ¼ 9.3 Hz, 1H, 6-H
2.1. 2-(4-Diethylaminobenzylidene)-1,3-indandione (ID1,
C20H19NO2)
Ph1,2,4ꢁsubst.); 8.42 (s, 1H, Ph-CH]C); 7.90e7.83 (m, 2H, 5,6-H of
indandione), 7.71e7.63 (m, 2H, 4,7-H of indandione); 6.40 (dd,
J ¼ 9.3 Hz, J ¼ 2.4 Hz, 1H, 5-H of Ph1,2,4ꢁsubst.); 6.13 (d, J ¼ 2.4 Hz, 1H,
3-H of Ph1,2,4ꢁsubst.); 4.39 (dd, JAM ¼ 11.1 Hz, JAX ¼ 3.1 Hz, (HA), 1H,
one of CH2O protons); 4.10 (dd, JMA ¼ 11.1 Hz, JMX ¼ 5.4 Hz, (HM), 1H,
another of CH2O protons); 3.46 (m, 5H, CHO, NCH2); 2.98 (dd,
4-Diethylaminobenzaldehyde (5.0 g, 28 mmol) and 1,3-
indandione (4.1 g, 28 mmol) were dissolved in 90 mL of ethanol.
The solution was left stirring at room temperature. After the
termination of the reaction (TLC, acetone: n-hexane, 5:18) obtained
red crystals were filtered off and washed with 2-propanol and
recrystallized from the mixture (1:1) of THF and 2-propanol. The
yield was 88% (7.6 g); m.p.: 154.5e156 ꢀC (154e155 ꢀC in Ref. [9]).
0
0
0
0
0
JA M ¼ 4.5 Hz, JA X ¼ 4.5 Hz, (HA ), 1H, one of CH2O protons); 2.86
0
0
0
0
(dd, JM A ¼ 4.5 Hz, JM X ¼ 2.7 Hz, (HM ), 1H, another of CH2O
protons); 1.24 (t, J ¼ 7.1 Hz, 6H, CH3).
1H NMR (300 MHz, CDCl3,
d, ppm): 8.52 (d, J ¼ 9.0 Hz, 2H, p-Ph);
APCI-MS: m/z (%): 378 [M þ H]þ (100).
7.95e7.86 (m, 2H, 4,7-H of indandione); 7.76 (s, 1H, CH]);
7.74e7.65 (m, 2H, 5,6-H of indandione); 8.52 (d, J ¼ 9.0 Hz, 2H, p-
Ph); 3.49 (q, J ¼ 7.13 Hz, 4H, NCH2); 1.26 (t, J ¼ 7.13 Hz, 6H, CH3).
Elemental analysis. Calcd. for C23H23NO4 (%): C 73.19; H 6.14; N
3.71. Found (%): C 72.95; H 6.27; N 3.57.
APCI-MS: m/z (%): 306 [M þ H]þ (100).
2.4. 1,3-Bis-{3-hydroxy-4-[4-diethylamino-1-(1,3-dioxoindan-2-
ylmethylene)benzen-3-yloxy]-1-thiabuthyl}benzene (ID2,
C52H52N2S2O8)
Elemental analysis. Calcd. for C20H19NO2 (%): C 78.66; H 6.27; N
4.59. Found (%): C 78.55; H 6.17; N 4.57.
2.2. 4-Diethylamino-2-oxiranylmethoxybenzaldehyde (1,
C14H19NO3)
Epoxy compound 2 (2.0 g, 5.3 mmol) and benzene-1,3-dithiol
(0.35 g, 2.65 mmol) were dissolved in 5 mL of THF. Then 0.14 mL
(1.06 mmol) of triethylamine was added. The mixture was stirred
intensively at the reflux temperature for 20 min. After the termi-
nation of the reaction (TLC, acetone: n-hexane, 7:18) solvent was
evaporated. The residue was purified by column chromatography
using 1:4 acetone: n-hexane as the eluent. The resultant red oil was
dissolved in 15 mL of THF and then poured with intensive stirring
into 200 mL of n-hexane to obtain amorphous product ID2. The
yield was 84% (1.9 g).
2.5 g (12.9 mmol) of 4-diethylamino-2-hydroxybenzaldehyde,
0.36 g (1.29 mmol) of benzyl triethylammonium chloride and 50 mL
(647 mmol) of epichlorohydrin were placed into a round bottom
flask. The reaction mixture was intensively stirred at the reflux
temperature for 15 min. After the termination of the reaction (TLC,
acetone: n-hexane, 1:4), the reaction mixture was treated with
chloroform and washed with distilled water. The organic layer was
dried over anhydrous MgSO4, filtered and solvent and excess of
epichlorohydrin were removed. The residue was treated with
diethyl ether. The obtained crystals were filtered off and washed
with diethyl ether. The yield was 86% (2.5 g); m.p.: 62e63 ꢀC
(diethyl ether).
IR (KBr),
n
, cmꢁ1: 3358 (OH), 3072 (CHarom), 2970, 2927, 2870
(CHaliph), 1707, 1660 (C]O), 1613, 1594, 1543, 1507 (C]C) 1275,
1253, 1154, 1077 (CeOeC), 810, 786, 735 (CH]CH of 1,2-di-, 1,3-di-
and 1,2,4-trisubstituted benzenes).
1H NMR (300 MHz, CDCl3,
d, ppm): 9.26e9.17 (m, 2H, 6-H
IR (KBr),
n
, cmꢁ1: 3104, 3058 (CHarom), 2980, 2957, 2921, 2901,
Ph1,2,4ꢁsubst.); 8.29e8.24 (m, 2H, Ph-CH]C); 7.82e7.52 (m, 8H,
Ar), 7.29e7.12 (m, 4H, Ar); 6.29e6.17 (m, 2H, 5-H of Ph1,2,4ꢁsubst.);
5.90e5.83 (m, 2H, 3-H of Ph1,2,4ꢁsubst.); 4.85e4.40 (m, 2H, OH);
4.28e4.06 (m, 2H, CHO); 4.06e3.88 (m, 4H, OCH2); 3.45e3.21 (m,
8H, SCH2, NCH2); 1.22e1.12 (m, 12H, CH3).
2870 (CHaliph), 1655 (C]O), 1553, 1523 (C]C), 1273, 1243, 1214,
1025 (CeOeC).
1H NMR (300 MHz, CDCl3,
d, ppm): 10.18 (s, 1H, HC]O); 7.72 (d,
J ¼ 9.0 Hz, 1H, 6-H Ph1,2,4ꢁsubst.); 6.31 (dd, J ¼ 9.0 Hz, 2.3 Hz, 1H, 5-H
of Ph1,2,4ꢁsubst.); 6.11 (d, J ¼ 2.3 Hz, 1H, 3-H of Ph1,2,4ꢁsubst.); 4.34
(dd, JAM ¼ 11.2 Hz, JAX ¼ 3 Hz, (HA), 1H, one of CH2O protons); 4.05
APCI-MS: m/z (%): 897 [M þ H]þ (45).

G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
35
Elemental analysis. Calcd. for C52H52N2O8S2 (%): C 69.62; H 5.84;
N 3.12. Found (%): C 69.56; H 5.88; N 3.76.
The course of reactions was monitored by TLC on Merck TLC
aluminum Silica gel 60 F254 sheets and developed with I2 or UV
light. Silica gel (grade 62, 60e200 mesh, 150 Å, Aldrich) was used
for column chromatography. Elemental analyses were performed
with Exeter Analytical CE-440 Elemental Analyzer. Melting points
were determined in capillary tubes on capillary melting point
apparatus Electrothermal MEL-TEMPÒ.
2.5. 4,40-Bis-{{3-hydroxy-4-[4-diethylamino-1-(1,3-dioxoindan-2-
ylmethylene)benzen-3-yloxy]-1-thiabutyl}phenyl}sulfide (ID3,
C58H56N2O8S3)
For refractive index evaluation spectral ellipsometer SOPRA
GES-5 with rotating polarizer was used. Chromophores dispersed
in polycarbonate were deposited on BK7 glass substrate covered
with gold (100 nm) using spin-coating technique. Film thickness
Synthesis of compound ID3 was carried out according to the
procedure described for ID2 except that 3.86 g epoxy compound 1
(10 mmol), 4,40-thiobisbenzenedithiol (1.25 g, 5 mmol) and 0.29 mL
(2 mmol) of triethylamine were used. The yield was 83% (4.2 g).
IR (KBr),
n
, cmꢁ1: 3407 (OH), 3072 (CHarom), 2970, 2928, 2870
4 mm, 4.3 mm and 11.5 mm for ID3, ID2 and ID1, respectively, was
measured by profilometer DEKTAK 150. Ellipsometry measure-
ments were carried out in spectral range from 400 to 1700 nm.
Optical constants were determined from ellipsometry data and
analyzed by SOPRA program Winelli using multi-layer model.
Cauchy function for refraction index:
(CHaliph), 1709, 1661 (C]O), 1613, 1594, 1542, 1507 (C]C) 1275,
1253, 1155, 1077 (CeOeC), 810, 788, 736 (CH]CH of 1,2-di-, 1,4-di-
and 1,2,4-trisubstituted benzenes).
1H NMR (300 MHz, CDCl3,
d, ppm): 9.26 (d, J ¼ 9.3 Hz, 1H, 6-H
Ph1,2,4ꢁsubst. of one diastereomer); 9.23 (d, J ¼ 9.3 Hz, 1H, 6-H
Ph1,2,4ꢁsubst. of other diastereomer); 8.27 (s, 1H, Ph-CH]C of one
diastereoisomer); 8.26 (s, 1H, Ph-CH]C of other diastereoisomer);
7.84e7.72 (m, 4H, Ar), 7.64e7.57 (m, 4H, Ar); 7.35e7.29 (m, 4H, Ar);
7.19e7.13 (m, 4H, Ar); 6.31 (dd, J ¼ 9.3 Hz, J ¼ 2.2 Hz, 2H, 5-H of
Ph1,2,4ꢁsubst.); 5.86 (m, 2H, 3-H of Ph1,2,4ꢁsubst.); 4.34e4.10 (m, 6H,
OCH2CH); 3.44e3.21 (m, 8H, SCH2, NCH2); 2.80e2.25 (m, 2H, OH);
1.21 (t, J ¼ 7.1 Hz, 12H, CH3).
B
C
n ¼ A þ
þ
;
(1)
l2 l4
was used in regression analysis to obtain optical constants
A ¼ 1.831 ꢂ 4.937$10ꢁ3, B ¼ 9.7$10ꢁ3
m
m2 (ID1), A ¼ 1.752
ꢂ 8.751$10ꢁ3, B ¼ 5.7$10ꢁ3 mm2 (ID2) and A ¼ 1.642 ꢂ 3.736$10ꢁ3
,
B ¼ 1.4$10ꢁ2 mm2 (ID3) [10].
Third harmonic generation was measured using Maker-Fringes
technique, which consist of the analysis of THG intensity oscilla-
tions on incidence angle variation from a ‘substrate-film’ structure.
The setup and method used may be found described in Ref. [11].
APCI-MS: m/z (%):1005 [M þ H]þ (38).
Elemental analysis. Calcd. for C58H56N2O8S3 (%): C 69.30; H 5.61;
N 2.79. Found (%): C 69.24; H 5.55; N 2.67.
2.6. Preparation of films composed with polymer matrix
4. Results and analysis
Three different samples of the indan-1,3-dione class molecules
(ID1, ID2, ID3) and DR1 dye (Dispersed Red 1, C16H18N4O3, SIGMA-
ALDRICH, product number 344206) dispersed in polycarbonate
matrix for THG experiments were prepared by spin-coating tech-
nique. It concerned 500 cycles per min for the first 6 s followed up
by 2000 for the next 20 s. Silica glass plates used as substrates were
degreased in ethanol, washed in distilled water and dried. Poly-
carbonate Iupilon Z-200 with Tg ¼ 189 ꢀC was chosen as a matrix
material for these molecules to create guest-host system. In order
to avoid aggregation, 10% (wt%) loading density of chromophores in
all samples was chosen. Finally, drying via two steps (25 min at
room temperature followed up by 45 min at 80 ꢀC) was performed.
Film thickness measurement provided by AFM (BioScope II)
The synthesis route to the arylmethylene-1,3-indandione
derivatives ID1eID3 is shown in Fig. 1. Thus, parent simple
structure 2-(4-diethylaminobenzylidene)indan-1,3-dione (ID1)
was prepared in good yield via condensation of 1,3-indandione
with 4-diethylaminobenzaldehyde, whereas the twin structures
ID2 and ID3 required three steps. In the first step, an intermediate
4-diethylamino-2-oxyranylmetoxybenzaldehyde (1) was produced
by reaction of commercially available 2-hydroxy-4-dieth-
ylaminobenzaldehyde with epichlorohydrin in presence of benzyl
trimethylammonium chloride. During the second step, condensa-
tion of 1 with 1,3-indandione at room temperature even in
the absence of a catalyst led to the derivative 2 containing an
epoxy group. Finally, the desired products 1,3-bis{3-hydroxy-4-[4-
diethylamino-1-(1,3-dioxoindan-2-ylmethylene)benzen-3-yloxy]-
revealed values: w4.5
mm for ID1, w3.5 mm e ID2, w2.6 mm e ID3
1-thiabuthyl}benzene
(ID2)
and
4,40-bis{{3-hydroxy-4-[4-
and w0.8 m e DR1 dye sample.
m
diethylamino-1-(1,3-dioxoindan-2-ylmethylene)benzen-3-yloxy]-
1-thiabutyl}phenyl}sulfide (ID3) were synthesized by reaction of
the oxirane function of 2 with difunctional nucleophilic linking
agents 1,3-benzenedithiol and 4,40-thiobisbenzenedithiol in pres-
ence of a catalytic amount of triethylamine (TEA).
3. Experimental
1H NMR spectra were measured on Varian Unity Inova spec-
trometer (300 MHz) in CDCl3. IR spectra of the samples in KBr
pellets were recorded on a Perkin Elmer Spectrum GX FT-IR System
spectrometer. Mass spectra were recorded on Waters (Micromass)
2Q 200. Absorption spectra of the material THF solutions (10ꢁ4 M)
placed in 1 mm path length microcell were recorded on Perkin
Elmer Lambda 35 UV/VIS spectrometer. Thermal properties were
examined by using Netzsch STA 409 PC Luxx apparatus at heating
rate of 10 K/min under nitrogen atmosphere. Glass transition
temperatures (Tg) were determined from second heating. XRD
analysis was performed using diffractometer DRON-UM2. Diffrac-
tion patterns were recorded at 30 kV and 20 mA in 1 deg/s detector
All our attempts to crystallize ID2 and ID3 were unsuccessful,
while the structure ID1 was crystallized from ethanol. The two
former materials were purified by column chromatography fol-
lowed by precipitation. Chemical structure of the arylmethylene-
1,3-indandione derivatives ID1eID3 were confirmed by IR, 1H NMR,
UV and APCI-MS spectroscopy. Splitting of some individual
downfield peaks in the 1H NMR spectra indicates that isolated
linked compounds ID2 and ID3 containing several stereogenic
centers, were isolated as mixtures of diastereomers, which could
not be separated by purification procedures. The IR spectra of
ID1eID3 are characterized by occurrence of two carbonyl absorp-
tions in the range of 1710e1707 cmꢁ1 and 1662e1660 cmꢁ1. This is
in accordance with the reports in the literature assigning the two
movement speed, intensity was measured every 2
diffracted beam pyrolitic graphite monochromator was used to
remove fluorescent X-rays.
Q
¼ 0.02ꢀ. Flat

36
G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
O
O
O
O
O
ID1
N
N
O
O
O
O
O
O
OH
O
O
EPH
cat.
O
O
N
N
1
2
N
O
N
O
OH
OH
O
O
S
O
S
O
HS-X-SH
TEA
X
ID2, ID3
N
ID2 X =
ID3 X =
,
.
S
Fig. 1. Synthesis route to the arylmethylene-1,3-indandione derivatives ID1eID3.
different signals to symmetrical (higher frequency) and asymmet-
rical (lower frequency) stretching mode of carbonyl groups [12].
In addition, the hydroxyl groups of twin ID2 and ID3 participating
(100 ꢀC) than of ID2 due to thiobisbenzene unit at the linking
fragment.
Electron transition from ground to excited state in ID1eID3
gives the main absorption maxima at ca. 483 nm for the ID1 and at
ca. 490 nm for the linked structures (Fig. 4). The red shift for linked
structures relates to known length effects. Relative absorption
maxima at wavelengths 205, 241 and 249 nm describe the
absorption to higher excited states with different vibrational levels.
in hydrogen bonding give rise to
a broad oscillation at
3600e3100 cmꢁ1
.
Existence of several diastereoisomers, possibility of intermo-
lecular hydrogen bonding and flexibility of aliphatic linking chains
make crystallization in solid state difficult ascribing twin aryl-
methylene-1,3-indandione molecules ID2 and ID3 to low molar
mass compounds with a stable amorphous phase above room
temperature. Such compounds are called molecular glasses or
amorphous molecular materials [13]. They form uniform, trans-
parent amorphous thin films by spin-coating method. In contrast to
crystalline compounds, which show anisotropic properties, these
amorphous materials exhibit isotropic as well as homogeneous
properties due to the absence of grain boundaries. In contrast to
polymers, they are pure materials with well-defined molecular
structure and definite molecular weight without any distribution.
X-ray diffraction pattern of ID2 and ID3 show only broad halos (see
Fig. 2) in contrast to structure ID1.
The formation of a glassy state for ID2 and ID3 was confirmed
by differential scanning calorimetry (DSC). These investigations
revealed that both investigated 2-(4-diethylamino-2-hydroxy-
phenylmethylene)-1,3-indandione based molecular glasses were
found only in the amorphous phase (see Fig. 3). No crystallization
took place at first heating of ID2, only glassing temperature (Tg)
was revealed at 88 ꢀC during the second heating. This is
a common feature for both ID2 and ID3. Tg of ID3 is higher
Fig. 2. X-ray diffraction patterns of ID1 and ID2 molecules.

G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
37
Fig. 3. DSC second heating curves of ID1eID3 molecules (heating rate 10 K/min).
Since ID2 and ID3 contain several isolated p-electron systems, the
total light absorption spectra is a sum of spectra of separate
molecule fragments. The comparison of spectra for compound ID2
with ID3 shows that ID3 gives an extra maxima at ca. 275 nm due to
the lone pairs of sulfur atom between two phenyl groups in the
central linking fragment, i.e. the 4,40-thiobisbenzenethiol. In
the spectra of molecules dispersed in polycarbonate and prepared
as film same characteristic peaks and shifts appeared, however, due
to relative high concentration of chromophores in ID1 sample
larger absorption coefficient and broader spectra was registered.
This higher concentration is an issue of preparing the films, since
for identical loading density of chromophores more than one third
of weight correspond to the spacer in the linked compounds. From
the analysis of ellipsometry data dispersion curves were built, what
gave us the refractive index values for 1,3-indandione based
molecules 1.948 (355 nm) ID1, 2.067 (355 nm) ID2 and 2.067
(355 nm) ID3 (Fig. 5). They were used later as a basis for modeling
Fig. 5. Refractive index dispersion n (
in polycarbonate ID1 (black), ID2 (gray), ID3 (light gray).
l
) for 1,3-indandione based molecules dispersed
where
ꢁ
ꢂ
ꢂ
3
u S
l
c
DjS
DjF
¼
¼
juS
ꢁ
j3S
¼
¼
nSucos QuS ꢁ nSucos Q3S
;
u
u
3
ꢁ
3
u F
l
jFu jF
QF
QF
3
F
ꢁ
nucos u ꢁ nF3ucos
;
3
u
u
c
ꢃ
ꢄ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
cð3Þ
cð3Þ
=
D
D
3
ꢄ
3
F
S
ꢃ
r
¼
;
=
!
3
2nð1Þ$cos Qð1Þ
nð1Þ$cos Qð1Þ þ nuS $cos QSu nu$cos
2nSu$cos QSu
the c(3)
.
T1
¼
$
QS þ nFu$cos QFu
S
u
To determine the third order non-linear optical susceptibility
c(3) a model describing the THG from a structure immersed
between two linear media was used [14]. The THG intensity in our
case from air-substrate-film follows a complex expression:
N3S þ NuS
u
$
;
N3Su þ N3F
u
!
3
2nF3u$cos QF3
n3Fu$cos QF3u þ nð1Þ$cos Qð1Þ
2nð1Þ$cos Qð1Þ
u
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ð3Þꢀ
T2 ¼
$
h
ꢁ
ꢂ
64p4
c
ꢀ
ꢀ
ꢀ
jSuþjS3
ð
e
DjS
u
nð1Þ$cos Qð1Þ þ nuS $cos QuS
i
Þ
I3
¼
T1 1 ꢁ eꢁi
u
c2
D
3
S
N3F þ NuF
ꢀ2
u
ꢁ
ꢂi
$
;
ꢀ
ꢀ
ꢀ
N3Fu þ N3ð1Þ
F
þ
r
T2ei4 eiDj ꢁ 1
ðIuÞ3;
ð2Þ
u
and the indexes (1), S and F refer to air (vacuum), substrate and film,
and 3 e to fundamental and harmonic wave, respectively; c is
the speed of light in vacuum; lu; N ¼ n$cos Dj is the
/c ¼ 2
phase mismatch between the fundamental (lu ¼ 1064 nm) and
third (l3 ¼ 355 nm) harmonic; l is the thickness; is the propa-
u
u
u
p
/
Q;
Q
a
u
gation angle;
D
3
¼
3
u ꢁ
3
u is the dielectric constant dispersion; 4 is
3
the phase of the film susceptibility ðcðF3Þ ¼ jcFð3Þj$ei4Þ; I is the
fluence.
THG intensity as a function of the incidence angle measured in
the silica substrate revealed a symmetric structure of spikes in
a train. Calculation using optical parameters for silica (see Table 1)
shows good agreement with the measurement (Fig. 6), which
proves the model used.
b
We succeeded to get a best fit of THG experimental results for
indan-1,3-dione derivatives (Fig. 7). The offset of THG signal is
defined by c(3) of the film, the fringes - of the substrate, when
the film thickness lF is much less than the coherence length
Lc;F
¼
l
u=½6$ðnF ꢁ nFuÞꢃ [14]. In our case of indan-1,3-dione
u
derivatives the3fringes should appear for both, the film and the
substrate, providing superposition since the condition is not ful-
filled (see Table 1). This may influence the reduced amplitude of
scattering of experimental points. The situation differs for DR1,
Fig. 4. UVeVIS absorption spectra of 1,3-indandione based molecules ID1 (black), ID2
(gray), ID3 (light gray) (THF, c ¼ 10ꢁ4 M) (a) and them dispersed in polycarbonate (b).
Thin lines represent 4,40-thiobisbenzenethiol (a) and polycarbonate itself (b).

38
G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
Table 1
Parameters used for modeling the experimental third harmonic generation for indan-1,3-dione based molecules ID1eID3 and DR1 dye dispersed in polycarbonate and the SiO2
plate (substrate) using Eq. (2).
Sample
lF m]
ID1
ID2
ID3
DR1
SiO2
[
m
4.5
3.5
2.6
0.8
lS[
m
nuS
m]
1000
1.730a
1.849a
1.836a
1.6028b
1.44967c
nuF
n3F
1.993d
2.087d
2.062d
1.658
1.4762e
n3S
u
u
T1
T2
28
1
28
1
28
1
28
1
28
cðF3Þ [m2/V2]
5.75$10ꢁ21
2.25$10ꢁ21f
0.67
8.60$10ꢁ21
3.45$10ꢁ21f
0.73
16.85$10ꢁ21
7.3$10ꢁ21f
0.76
29.6$10ꢁ21
24.70$10ꢁ21
3.2
cðS3Þ [m2/V2]
Lc,S m]
2.0$10ꢁ22e
Lc,F
[m
m]
[m
6.7
a
From ellipsometry data.
b
c
d
e
f
l
¼ 1053 nm, 13 wt% [23].
[21].
From ellipsometry data, adjusted while modeling.
[21].
Calc. using Eq. (3).
where the condition is valid and the amplitude of the fringes is
well expressed. From modeling, 2-to-3 times higher c(3) value for
the linked samples (ID2,ID3) than for the simple compound ID1
sample was obtained. Whereas the samples were equally loaded
by weight (percentage), a larger number of chromophores was
expected for ID1. This would predict less susceptibilty for ID2 and
ID3 since each is composed of two ID1 moieties and a linking
spacer. Interconnected via aliphatic junction the ID1 are treated
non-linearity for linked compounds is the glass transition
temperature. It was confirmed that Tg increase for amorphous
molecular glasses enhances surface relief grating formation
property [19].
Almost twice less c(3) value was obtained when applying
another method proposed by Wang [20] (see Table 1). This
simplified method based on comparison of cðF3Þ between material of
interest and reference (silica):
isolated with their
p-electron conjugated system. Probably, these
sffiffiffiffiffiffiffiffiffi
cðF3Þ
cðS3Þ
evaluations are lacking of one factor e the intramolecular charge
transfer, which could significantly contribute to the cubic non-
linearity [15]. The simple 1,3-indandione compounds having
donor and acceptor group form an ascentric system characterized
by higher second order hyperpolarizability than symmetrically
shaped donoredonor or acceptoreacceptor pairs [16]. The fact of
relative increase of third order susceptibility observed for ID2 and
ID3 samples in our case could be a proof that simple additivity of
second order hyperpolarizabilities within complex systems
couldn’t be sufficient. Moreover, our results indicate that the
longer the spacer the larger increase of susceptibility was
obtained, despite less quantity of chromophores in the sample
ID3. Similar indications noted when measuring charge carrier
drift in similar derivatives: despite the lower concentration of
chromophores, the hole drift mobilities measured in these
molecular glasses exceeded the parameters of the analogous with
higher concentration of photoconductive moieties [17]. Two
possible arguments: close packaging feature and intramolecular
charge transfer contribution to conductivity for multimers were
discussed [18]. Another aspect supporting the increase of optical
Lc;S
lF
I3
I3
2
p
u
;F
;S
¼
$
$
;
(3)
u
where Lc,S is the coherence length and cðS3Þ ¼ 2:0$10ꢁ22m2=V2 [21]
both for the reference; lF is the thickness of film; I3 ,F and I3 are
u
u,S
the third harmonic intensities of the film and the reference,
respectively. The deviation from the first approach may concern
some conditions ignored in Eq. (3) and could be important due to
THG spectra position in our case. Same ratio of deviation was
observed by Sahraoui (see Table 3 in Ref. [11]). Nevertheless, the
result should be valuated as reasonable and supporting the order of
magnitude for the third order optical non-linearity of 1,3-
indandione based molecular glasses.
Using both approaches we should consider the estimated c
(3) for
1,3-indandione derivatives as a lower limit. The task to investigate
frequency conversion at YAG laser third harmonic (wavelength
355 nm) meant the situation “close or within the resonance” for
1,3-indandiones, i.e. the THG quantum energy corresponded to the
transition between the ground and first excited state, and the
ground and higher excited state (see Fig. 4). Together with some
marginal absorption observed in the spectra this may imply also
non-linearity dispersion effects.
In order to rank the optical non-linearity of arylmethylene-1,3-
indandione molecular glasses a reasonable comparison with DR1
dye in polycarbonate was made. Due to the similarity of the
absorption spectra (eg [22].) the same conclusion as made for 1,3-
indandiones about the limit for the c(3) value to DR1 could be
applied. The obtained c(3) for DR1 is almost 1.5 times higher than
for DR1 doped DNA films [22]. However, the twice higher
concentration of chromophores used in our case makes the
approximate balance. Based on that one could conclude that the
third order optical non-linearity of 1,3-indandione derivatives is
quite close to recognized dye molecules. Moreover, the molecular
structure of the presented 1,3-indandione based molecular glasses
prevents crystallization and allows preparation of stable films for
non-linear optics without a binder or with a low binder concen-
tration. Such experiments are currently underway.
Fig. 6. Third harmonic generation for silica plate. Lines are modeling results using Eq.
(2) explained in the text.

G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
39
Fig. 7. Third harmonic generation for 1,3-indandione based molecules ID1 (top, left), ID2 (top, right), ID3 (bottom, left) and DR1 (bottom, right) dye dispersed in polycarbonate.
Lines are modeling results using Eq. (2) explained in the text.
Lee CY-C, editors. NATO ASI series, 3. High technology, vol. 9. Dodrecht:
Kluwer Academic Publishers; 1996. p. 375e92.
5. Conclusions
[2] Rutkis MA, Wistus E, Lindquist SE, Mukhtar E, Liberts G, Zauls V, et al. Lang-
New linked structures 1,3-bis-{3-hydroxy-4-[4-diethylamino-1-
(1,3-dioxoindan-2-ylmethylene)benzen-3-yloxy]-1-thiabuthyl}
benzene (ID2) and 4,40-bis-{{3-hydroxy-4-[4-diethylamino-1-(1,3-
dioxoindan-2-ylmethylene)benzen-3-yloxy]-1-thiabutyl}phenyl}
sulfide (ID3), which appeared as molecular glass featuring glass
transition temperatures 88 ꢀC and 100 ꢀC, respectively, revealed
higher third order optical non-linearity than the model simple
arylmethylene-1,3-indandione structure 2-(4-diethylaminoben-
zylidene)indan-1,3-dione (ID1). Lengthening of linking spacer in
ID2 and ID3 appeared to enhance significantly the molecular
second order hyperpolarizability. Samples prepared as host-guest
system in polycarbonate were investigated by means of third
harmonic generation. Third order non-linear susceptibility
c(3) ¼ 16.85$10ꢁ21 m2/V2 (wavelength 355 nm) obtained for the
linked structure ID3 demonstrated potential for 1,3-indandione
based molecular glasses be applied in organic optoelectronics for
muir-Blodgett films of indandione-1,3 pyridinium betaine. III: linear
dichroism and non-linear optical properties. Adv Mater Opt Electron 1996;6:
39e50.
ꢁ
ꢀ_
[3] Kodis G, Gulbinas V, Valkunas L, Jursenas S. Non-linear luminescence of
dimethylaminobenzylidene-1,3-indandione solids. Adv Mater Opt Electron
1996;6:391e4.
[4] Utinans M, Neilands O. Quantum chemical calculations, synthesis and prop-
erties of novel organic molecules with photoinduced intramolecular electron
transfer and large change in electric dipole moment in the excited state. Adv
Mater Opt Electron 1999;9:19e25.
[5] Vembris A, Apostoluk A, Rutkis M, Tokmakovs A, Muzikante I, Dabos-
Seignon S, et al. All-optical poling of DMABI molecules in a polymer matrix.
Proc SPIE 2005;5946(59460P):1e6.
[6] Rutkis MA, Vembris A, Zauls V, Tokmakovs A, Fonavs E, Jurgis A, et al.
Novel second-order non-linear optical polymer materials containing
indandione derivatives as a chromophore. Proc SPIE 2006;6192(61922Q):
1e8.
[7] Schwartz H, Mazor R, Khodorkovsky V, Shapiro L, Klug JT, Kovalev E, et al.
Langmuir and Langmuir-Blodgett films of NLO active 2-(p -N -Alkyl-N-
methylamino)benzylidene-1,3-indandione-
p/A curves, UVeVis spectra, and
SHG behavior. J Phys Chem B 2001;105:5914e21.
optical frequency conversion. Evaluation of c
(3) was performed via
ꢀ_
[8] Karpicz R, Getautis V, Kazlauskas K, Jursenas S, Gulbinas V. Multicoordina-
tional excited state twisting of indandione-1,3-dione derivatives. Chem Phys
2008;351:147e53.
[9] Khodorkovsky V, Mazor RA, Ellern A. 2-(p -diethylaminobenzylidene)-1,3-
indandione. Acta Cryst 1996;C52:2878e80.
modeling the experimental results and analyzed using two
approaches.
[10] Tompkins HG, Irene EA. Handbook of ellipsometry. Berlin Heidelberg:
Springer; 2005.
Acknowledgments
[11] Sahraoui B, Luc J, Meghea A, Czaplicki R, Fillaut J-L, Migalska-Zalas A.
Nonlinear optics and surface relief gratings in alkynyl-ruthenium complexes.
J Opt A Pure Appl Opt 2009;11(024005):1e26.
This work was partially supported by a grant from the Lithua-
nian State Science and Studies Foundation (project Mulatas 2), by
the Agency of International Science and Technology Development
in Lithuania and by the EU COST Action MP0702. GS acknowledges
the STSM grant Nr.4695. The authors wish to express their appre-
[12] Perjessy A, Hrnciar P. The C¼O stretching bands of 1,3-indandione derivatives.
Tetrahedron 1971;27:6159e69.
[13] Shirota Y. Organic materials for electronic and optoelectronic devices. J Mater
Chem 2000;10:1e25.
[14] Kajzar F, Messier J, Rosilio C. Nonlinear optical properties of thin films of
polysilane. J Appl Phys 1986;60:3040e4.
ꢀ
_
ciation to G.Medeisiene for sample preparation.
[15] Alain V, Rédoglia S, Blanchard-Desce M, Lebus S, Lukaszuk K, Wortmann R,
et al. Elongated push-pull diphenylpolyenes for nonlinear optics: molecular
engineering of quadratic and cubic optical nonlinearities via tuning of intra-
molecular charge transfer. Chem Phys 1999;245:51e71.
References
[16] Martin RE, Gubler U, Boudon C, Bosshard C, Gisselbrecht JP, Günter P, et al.
Synthesis and physical investigation of donoredonor and acceptoreacceptor
[1] Silinsh EA. Photoactive molecular multilayer Langmuir-Blodgett (LB) films of
oriented dipolar betaine type organic molecules. In: Kajzar F, Agranovich VM,

40
G. Seniutinas et al. / Dyes and Pigments 95 (2012) 33e40
end-functionalized monodisperse poly(triacetylene) oligomers. Chem Eur J
2000;6:4400e12.
[17] Getautis V, Daskeviciene M, Gaidelis V, Jankauskas V. Hole-drift mobility in
phenylenediamine derivatives possessing methyl substituents. J Photochem
Photobiol A Chem 2005;175:39e44.
[18] Daskeviciene M, Getautis V, Grazulevicius JV, Stanisauskaite A, Antulis J,
Gaidelis V, et al. Crosslinkable carbazolyl-containing molecular glasses for
electrophotography. J Imag Sci Technol 2002;46:467e72.
[19] Nakano H, Takahashi T, Tanino T, Shirota Y. Synthesis and photoinduced surface
relief grating formation of novel photo-responsive amorphous molecular mate-
rials, 4-[bis(9,9-dimethylfluoren-2-yl)amino]-40-cyanoazobenzeneand4-[bis(9,9-
dimethylfluoren-2-yl)-amino]-40-nitroazobenzene. Dyes Pigm 2010;84:102e7.
[20] Wang XH, West DP, McKeown NB, King TA. Determining the cubic suscepti-
bility c(3) of films or glasses by the Maker fringe method: a representative
study of spin-coated films of copper phthalocyanine derivation. J Opt Soc Am
B 1998;15:1895e903.
[21] eg. Gubler U, Bosshard C. Optical third-harmonic generation of fused silica in
gas atmosphere: absolute value of the third-order nonlinear optical suscep-
tibility c(3) Phys Rev B 2000;61:10702e10
[22] Krupka O, El-ghayoury A, Rau I, Sahraoui B, Grote JG, Kajzar F. NLO properties
of functionalized DNA thin films. Thin Solid Film 2008;516:8932e6.
[23] Samoc A, Samoc M, Luther-Davies B, Kolev VZ, Bagien RK, Luo X, et al. In situ
second harmonic generation in Disperse Red 1-doped polymer and sol-gel
films. Mol Cryst Liq Cryst 2006;446:123e40.