Structural characterization of vanillin derivatives with long alkyl chain and investigation of their electrochemical and thermal properties

Article abstract of DOI:10.1016/j.molstruc.2019.127018

This manuscript describes the synthesis, characterization and thermal properties of the two vanillin derivatives containing a long alkyl chain. Two vanillin derivatives 4-(heptyloxy)-3-methoxybenzaldehyde (L¹) and 4-(decyloxy)-3-methoxybenzalde

Full text of DOI:10.1016/j.molstruc.2019.127018

Journal of Molecular Structure 1199 (2020) 127018
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Structural characterization of vanillin derivatives with long alkyl chain
and investigation of their electrochemical and thermal properties
*
€
Mehmet Tümer, Ferhan Tümer , Muhammet Kose
Chemistry Department, K.Maras Sütcü Imam University, 46100, K. Maras, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
This manuscript describes the synthesis, characterization and thermal properties of the two vanillin
Received 30 April 2019
Received in revised form
15 August 2019
Accepted 2 September 2019
Available online 6 September 2019
derivatives containing
a
long alkyl chain. Two vanillin derivatives 4-(heptyloxy)-3-
methoxybenzaldehyde (L1) and 4-(decyloxy)-3-methoxybenzaldehyde (L2) were obtained from the re-
action of the vanillin with 1-bromoheptane or 1-bromodecane in DMF reaction media, respectively. The
vanillin derivatives L1 and L2 have been characterized by the 1He13C NMR, FTIR and mass spectral
techniques. Single crystals suitable for X-ray diffraction studies were grown by recrystallization of a
chloroform solutions of the compounds. There are phenyl-phenyl stacking (edge to edge) interactions
within the structures. Thermal analysis data (DSC) revealed that compounds do not show any liquid
crystalline character. The electrochemical behaviours of the organic compounds L1 and L2 were inves-
tigated and all redox processes in the 100e1000 mV/s scan rates are irreversible.
Keywords:
Vanillin
X-ray structure
Electrochemistry
DSC
© 2019 Published by Elsevier B.V.
Emission
1. Introduction
chalcones containing the alkyloxy vanillin ether derivatives have
been investigated and it has been found that the stability and the
Vanilla has processed as a flavour a kind of pre-Columbian
Mesoamerican community. In Central America, people have been
used the vanilla as a flavour in chocolate. The people's of Europe
discovered both chocolate and vanilla in the 1520s [1]. Previously,
the natural vanillin has been extracted from the seeds of the Vanilla
planifolia plant. But nowadays, Madagascar, an African country, is
the largest producer of natural vanillin. The vanillin compound is
widely used in many areas. These are in the producing of phar-
maceuticals, cosmetics, and other fine chemicals [2]. In addition,
vanillin is also used in perfumes, flavor and aromatic masking in
medicines, miscellaneous user and cleaning products, and livestock
foods [3]. Vanillin is a aromatic aldehyde, and it contains the
aldehyde, hydroxyl, and ether functional groups on the phenylene
ring. Several ether derivatives containing aliphatic long chains of
the vanillin have been synthesised and characterized [4,5]. In these
studies, the hexyloxy-, heptyloxy- and many other long chain
containing vanillin based on ether compounds were obtained and
their properties were investigated. In another study, the liquid
crystalline properties of the unsymmetrical compounds based on
range of the mesophases increased with the length of the chain in
the compounds [6].
Some substances have the intermediate state of matter with
molecular arrangement in among that of the traditional crystalline
solid and isotropic liquid phases. These substances are called liquid
crystal (LC) or mesomorphic state. This state of the matter is an
anisotropic liquid. Molecular shape of the materials has a prepon-
derant effect on the presence of the liquid crystalline properties.
The materials having LC properties are beneficial in the electronic
apparatus (LCDs), medical thermographic devices, photo-
conductors and semiconductor materials, pharmaceutical pre-
paredness and the textile industry [7]. The beginning necessity to
stimulate the liquid crystalline properties in a material are the
molecular stiffness and flexibility [8e11].
In this paper, two vanillin derivatives 4-(heptyloxy)-3-
methoxybenzaldehyde
(L1)
and
4-(decyloxy)-3-
methoxybenzaldehyde (L2) were obtained and characterized by
the analytical and spectroscopic techniques. Thermal stabilities and
phase transitions of the compounds L1 and L2 were investigated by
the thermogravimetry (TGA) and differential scanning calorimetry
(DSC). The molecular structures of the L1 and L2 were determined
by the single crystal X-ray diffraction studies. The redox and pho-
tophysical properties of the compounds were investigated.
* Corresponding author.
E-mail address: ftumer@ksu.edu.tr (F. Tümer).
https://doi.org/10.1016/j.molstruc.2019.127018
0022-2860/© 2019 Published by Elsevier B.V.

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
2. Experimental
structures [13]. Crystallographic diffraction data for L1 were ob-
tained at 150(2) K. A single crystal of L2 was mounted on a fiber and
nitrogen cryostream was adjusted to 150(2) K. However, the crystal
lost crystallinity and became white powder at this temperature.
Therefore, the data for L2 were collected at room temperature with
no problem. The structures were solved by direct methods and
refined on F2 using all the reflections [13]. All the non-hydrogen
atoms were refined using anisotropic atomic displacement pa-
rameters and hydrogen atoms bonded to carbon atoms were
inserted at calculated positions using a riding model. Details of the
crystal data and refinement are given in Table 1. Bond distances and
angles for compounds are given in the supplementary documents
(Tables S1 and S2).
2.1. Materials and measurements
All reagents and solvents were of reagent-grade quality and
obtained from commercial suppliers (Aldrich or Merck). Elemental
analyses (C,H,N) were performed using a LECO CHNS 932. Infrared
spectra were obtained using KBr disc (4000-400 cmꢀ1) on a Per-
kinElmer Spectrum 100 FT-IR. The electronic spectra in the
200e900 nm range were obtained on a PerkinElmer Lambda 45
spectrophotometer. Mass spectra of the ligands were recorded on a
LC/MS APCI AGILENT 1100 MSD spectrophotometer. 1H and 13C
NMR spectra were recorded on a Bruker 400 MHz instrument. TMS
was used as internal standard and CDCl3 as solvent. The thermal
analysis studies of the compounds were performed on a Perki-
nElmer STA 6000 simultaneous Thermal Analyzer under nitrogen
atmosphere at a heating rate of 10 ꢁC/min. The DSC analysis of the
synthesised compounds were performed on DSC (PerkinElmer
DSC-8000) using continuous heating and cooling under a pure ni-
trogen (N2) atmosphere. The samples (about 2 mg) are accurately
weighed by using a precision balance and the weighed samples
were sealed in aluminium pans. The samples were heated up to the
estimated clearing temperature at heating rate of 10 ꢁC/min and
stayed at its isotropic temperature for 4 min to reach thermal
stability.
2.3. General procedure for the synthesis of 4-(heptyloxy)-3-
methoxybenzaldehyde (L1) and 4-(decyloxy)-3-
methoxybenzaldehyde (L2)
A mixture of 4-hydroxy-3-methoxybenzaldehyde (1 mmol), 1-
bromoheptane (1 mmol) and K2CO3 (3 mmol) in N,N-dimethyl
formamide (25 mL) was stirred at room temperature for 4 h. The
reaction was monitored by TLC. After the completion of reaction,
the product was extracted into ether layer and it was dried over
anhydrous
Na2SO4
to
obtain
4-(heptyloxy)-3-
methoxybenzaldehyde (L1). Similar procedure except using 1-
bromodecane rather than 1-bromoheptane was followed up to
obtain 4-(decyloxy)-3-methoxybenzaldehyde (L2).
The single-photon fluorescence spectra of the vanillin based
compounds L1 and L2 were collected on a PerkinElmer LS55 lumi-
nescence spectrometer. All samples were prepared in spectropho-
tometric grade solvents and analysed in a 1 cm optical path quartz
cuvette. The solutions of ligands (1.0 ꢂ 10ꢀ3 mol Lꢀ1) were prepared
in DMF solvent.
L1: C15H22O3: Yield: 98%, color: Dirty white, melting point:
38e40 ꢁC. Elemental Analysis (%): Found (Calcd.): C, 72.02 (71.97%);
H, 8.81 (8.86%). 1H NMR (
d, ppm; CDCl3): 9.85 (1H, s, eHC]O),
7.43e7.45 (1H, dd (j: 1.8, 8.1 Hz), AreH), 7.41 (1H, d (j: 1.8 Hz),
AreH), 6.96e6.98 (1H, d (j: 8.1 Hz), AreH), 4.12 (2H, t, OeCH2-),
3.93 (3H, s, OeCH3), 1.92 (2H, p, OeCeCH2-), 1.49e1.32 (8H, m,
A stock solution in the 1 ꢂ 10ꢀ3 M concentration of the vanillin
based compounds L1 and L2 was prepared in DMF for electro-
chemical studies. Cyclic voltammograms were recorded on a
Iviumstat Electrochemical workstation equipped with a low cur-
rent module (BAS PAe1) recorder. The electrochemical cell was
equipped with a BAS glassy carbon working electrode (area
4,6 mm2), a platinum coil auxiliary electrode and a Agþ/AgCl
reference electrode filled with tetrabutylammonium tetra-
floroborate (0.1 M) in DMF and DMF solution and adjusted to 0.00 V
vs SCE. Cyclic voltammetric measurements were made at room
temperature in an undivided cell (BAS model C-3 cell stand) with a
platinum counter electrode and an Agþ/AgCl reference electrode
(BAS). All potentials are reported with respect to Agþ/AgCl. The
solutions were deoxygenated by passing dry nitrogen through the
solution for 30 min prior to the experiments, and during the ex-
periments the flow was maintained over the solution. Digital
simulations were performed using DigiSim 3.0 for windows (BAS,
Inc.). Experimental cyclic voltammograms used for the fitting
process had the background subtracted and were corrected elec-
tronically for ohmic drop. Mettler Toledo MP 220 pH meters was
used for the pH measurements using a combined electrode (glass
electrode reference electrode) with an accuracy of 0.05 pH.
Eclipse E200, Nikon Japan Polarised optical microscope (POM)
equipped with the digital camera was used. Temperature of sample
was controlled with heating stage LTS 120, with PE95 LinkPad ac-
curacy of 0.1 C from LinkamScientific Instrument, Ltd., England.
POM studies carried out not only to observe the morphological
texture of prepared samples but also to monitor phase transitions.
aliphatic-CH2), 0.88(3H, t, eCH3). 13C NMR (
d, ppm; CDCl3):
14.05e31.71 (Aliphatic -CH2-, -CH3), 56.02 (OCH3), 68.99 (OCH2-),
109.18e154.30 (AreC), 190.70 (-HC]O). FTIR (KBr, cmꢀ1): 2927
n(CeH)alph, 1677
n(C]O), 1393 n(CeO)phenolic, 781 n(out of plane
CeH).
L2: C18H28O3: Yield: 82%, color: Dirty white, melting point:
52e55 ꢁC. Elemental Analysis (%): Found (Calcd.): C, 73.97 (73.93);
H, 9.68 (9.65%). 1H NMR (
d, ppm; CDCl3): 9.86 (1H, s, eHC]O), 7.44
(1H, dd (j: 1.8, 8.1 Hz), AreH), 7.43 (1H, d (j: 1.8 Hz), AreH), 6.99 (1H,
Table 1
Crystallographic data for the compounds.
Identification code
L1
L2
Empirical formula
Formula weight
Temperature(K)
Crystal system
Space group
C15H22O3
250.33
150(2)
C18H28O3
292.40
293(2)
Monoclinic
P2(1)/c
Triclinic
P1
Unit cell
a (Å)
b (Å)
c (Å)
a
b
g
8.4137 (18)
9.939 (2)
17.509 (4)
102.404 (3)
94.736 (3)
101.260 (3)
1390.6 (5)
4
22.131 (3)
9.3398 (13)
8.5515 (12)
90
93.341 (2)
90
1764.6 (4)
4
1.101
(ꢁ)
(ꢁ)
(ꢁ)
Volume (Å3)
Z
Calculated density(g/cm3)
1.196
0.082
Abs. coeff. (mmꢀ1
)
0.073
2.2. X-ray crystallography for compounds L1 and L2
Refl. collected
5756
15312
R1, wR2 [I > 2
s
(I)]
0.0472,0.1339
0.0889,0.1641
0.762
0.0419,0.1216
0.0818,0.1527
1.008
R1, wR2 (all data)
Goodness-of-fit on F2
CCDC
Data were collected on a Bruker ApexII CCD diffractometer using
Mo-K
a
radiation (
l
¼ 0.71073 Å). Data reduction was performed
1062277
1062278
using Bruker SAINT [12]. SHELXTL was used to solve and refine the

M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
3
d (j: 8.1 Hz), AreH), 4.13 (2H, t, OeCH2-), 3.94 (3H, s, OeCH3), 1.93
(2H, p, OeCeCH2-), 1.50e1.29 (14H, m, aliphatic-CH2), 0.91(3H, t,
4-(decyloxy)-3-methoxybenzaldehyde (L2)] were synthesised by
the reaction of vanillin and 1-bromoheptane or 1-bromodecane in
DMF. The electrochemical and thermal properties of the com-
pounds have been investigated. Also, single crystals of both com-
pounds were grown from slow evaporation of CHCl3 solution of the
compounds. The solubility of the compounds is very high in the
polar and apolar organic solvents.
eCH3). 13C NMR (
-CH3), 56.03 (OCH3), 69.20 (OCH2-), 109.20e154.30 (AreC), 190.89
(-HC]O). FTIR (KBr, cmꢀ1): 2928
(CeH)alph, 1682 (C]O), 1402
(CeO)phenolic, 804 (out of plane CeH).
d, ppm; CDCl3): 14.09e31.73 (Aliphatic -CH2-,
n
n
n
n
All spectroscopic data for the compounds L1 and L2 have been
given in the experimental section. The FTIR spectra of the com-
3. Results and discussion
pound L1 and L2 are presented in Fig. 1 &S1. The aliphatic
n(CeH)
vibration bands resulting from long chains in the compounds are
In this paper, two vanillin-based ether compounds (Scheme 1)
L1 and L2 have obtained and characterized by using the elemental
analyses, 1He13C NMR, FTIR, UVeVis., emission and mass spectra.
The compounds [4-(heptyloxy)-3-methoxybenzaldehyde (L1) and
observed at about 2927 cmꢀ1 as a sharp peak. The bands at 1677 for
L1 and 1682 cmꢀ1 for L2 come from the vibration
n(C]O) of the
carbonyl group on the vanillin ring. The presence of characteristic
Scheme 1. The synthesis reaction of the compounds L1 and L2.
Fig. 1. FTIR spectrum of the compound 4-(heptyloxy)-3-methoxybenzaldehyde (L1).

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
Fig. 2. The UVevis, emission and excitation spectra of the compounds L1 and L2 in the 1.0 ꢂ 10ꢀ3 M DMF solution.

M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
5
Fig. 3. The 1H and 13C NMR spectra of L2 in CDCl3.

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
Fig. 4. The cv curves of the compounds L1 and L2 in the 1.0 ꢂ 10ꢀ3 M DMF solution and 100e1000 mV/s scan rates.

M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
7
bands in the FTIR spectra of the compounds confirms their
structure.
methoxy group on the vanillin ring were observed at 3.93 for L1 and
3.94 for L2 ppm as a singlet signal. The aliphatic chain methyl and
methylene (eCH2e, eCH3) hydrogen atoms were found in the
0.88e1.93 ppm range as multiplets. In the 13C NMR spectra of the
compounds L1 and L2, the carbon atom signals of the carbonyl
group was seen at 190.70 and 190.89 ppm, respectively. The signals
in the 109.18e154.30 ppm range can be attributed to the aromatic
ring carbon atoms. The signals of methoxy and methylenoxy carbon
atoms were observed in the 56.02e69.20 ppm range. The signals of
the aliphatic carbon atoms are in the 14.05e31.73 ppm range.
The electrochemical properties of the compounds L1 and L2
were investigated by using 1.0 ꢂ 10ꢀ3 M DMF solution and in the
range 100e1000 mV/s scan rates. The cyclic voltammograms (cv) of
the compounds have been given in Fig. 4. In the cv curve of the L1, a
very weak cathodic peak at ꢀ0.70 V arises from the reduction of the
aldehyde group to the alcohol group. In the L2, this reduction peak
has become more apparent and shown at about 0.25 V. Depending
on the number of the chain long in the L2 compound, the reduction
process was more difficult than the L1. In the anodic scanning, the L1
compound has three oxidation processes in the ꢀ1.90-0.75 V range.
These reactions are the oxidation from the alcohol to aldehyde and
etheric oxygens to ketones (Fig. 5) [14,15]. Similar redox reactions
were also observed in the L2 compound. However, the anodic peak
values in this compound are in the range ꢀ1.0e0.28 V. Depending
on the increasing of the scan rate, although the peak potential
values did not change, the peak current values increased.
The UVeVis., emission and excitation properties of the com-
pounds L1 and L2 were investigated in DMF solution (10ꢀ3 M) and
their spectra are given in Fig. 2. The compounds showed similar
absorption bands in DMF. In the UVevis spectra of the compounds,
there are two absorption bands in the 340-250 nm range. While the
bands at the longer wavelengths are result from the n- * transi-
p
tions, the bands at 290-250 nm range are due to the p-p* transi-
tions. It can be seen from the UVeVis spectra that the length of the
aliphatic chain does not have a significant effect in the absorption
wavelengths, yet higher absorption intensities were observed for
the longer aliphatic chain (L2). In the emission and excitation
spectra of the compounds L1 and L2, there are two bands and while
the intensity of one of them is very low but another is high. It has
been determined that the increasing of the aliphatic chain number
has not changed the emission and excitation wavelengths of the
compounds.
The 1He13C NMR spectra of the compounds were investigated
and obtained spectral data are given in the experimental section.
The 1He13C NMR spectra of the compound L2 are shown in Fig. 3
and 1He13C NMR spectra of the compound L1 is given in the sup-
plementary documents (Fig. S2). In the 1H NMR spectra of the
compounds L1 and L2, the signals at 9.85 and 9.86 ppm can be
attributed to the hydrogen atom of the carbonyl group (HC]O),
respectively. The aromatic ring hydrogen atoms were seen in the
6.98e7.45 ppm range as multiplet. The hydrogen atoms of the
Fig. 5. Redox processes in the vanillin at the scanning regions in 1.0 ꢂ 10ꢀ3 M DMF solution.

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
3.1. X-ray structures of L1& L2
compounds L1& L2 are shown in Fig. 6a and b. Asymmetric unit of L1
contains two independent molecules differing by the position of
the aldehyde group, the aldehyde oxygen(O3) atom in molecule B is
disordered with respect to C13 and it was modelled as 70:30
(O3:O3’) occupancy over the two positions. In both compounds, the
formyl group bond distances are within the range of C]O bond
distances.
Single crystals of the compounds were obtained from slow
evaporation of chloroform solutions of the compounds. Molecular
structures of two vanillin derivatives are closely similar differing
only in the number of carbon atoms in the alkyl chain; L1 contains
seven carbon atoms (heptyl) in the chain while L2 has ten carbon
atoms (decyl) in the alkyl chain. Molecular structures of the
In the structure of L1, two independent molecules in the
Fig. 6. a) Asymmetric unit of L1 with thermal ellipsoid (30% probability), the aldehyde oxygen atom in molecule A is disordered and it was modelled 70:30 (O3:O3’) occupancy over
the two positions. b) Asymmetric unit of L2 with thermal ellipsoid (30% probability).
Fig. 7. Packing plot of L2 viewing down c axis showing interdigitation in the decyl chain of the molecules. Hydrogen atoms are omitted for clarity.

M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
9
asymmetric unit are linked by weak hydrogen bond type CHphe-
nyl$$$$Oaldeyhde interactions (Fig. 6a). In structure of L2, the alkyl
chain is in trans conformation except for the bond from the carbon
atom connected to the phenol unit and the second carbon of the
alkyl chains. In L1, the heptyl group of two molecules is interdigi-
tated (head to tail) forming a non-polar region (Fig. S3). The heptyl
group of the molecule is aligned to phenyl group of an adjacent
molecule which restricts cycle stacking between the phenyl rings.
However, the extension of the alkyl chain from seven to ten
(compound L2) results in fully interdigitation of the alkyl chains
(head to tail) forming a non-polar domain. The phenyl ring of two
neighbouring molecules showed phenyl-phenyl stacking in-
teractions resulting in zipper-like chains along the c axis (Fig. 7).
Hirshfeld surfaces for the compounds L1 and L2 were drawn to
Fig. 8. Finger print plots for L1 and L2 showing different intermolecular contacts.
Fig. 9. Relative contribution of different intermolecular contacts to overall stability of the crystal structures of L1 and L2.

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
elucidate the intermolecular interactions of the polar and nonpolar
moieties of the molecules with their neighbouring molecules.
Hirshfeld surface analysis represent a clear visualization of poten-
tial van der Waals interactions between the alkyl group of adjacent
molecules which may form an interdigitation in the crystal packing
(H$$$$H contacts). As shown in Fig. 8, the 2D fingerprint plots of the
compounds L1 and L2 are very similar and indicated high intensities
for di and de values between 1.2 and 1.8 Å, indicating the high de-
gree of hydrophobic interactions. The relative contribution of
intermolecular contacts for both compounds is given in Fig. 9. The
main contribution for both compounds comes from H$$$$H con-
tacts followed by O$$$$H/H$$$$O and C$$$$H/H$$$$C contacts. The
longer carbon chain in compound L2 resulted in higher degree of
hydrophobic interactions (H$$$$H) between the molecules. In both
structures, the closer intermolecular O$$$$H/H$$$$O contacts were
observed as red-spots in the dn surfaces of the compounds (Fig. S4).
Fully interdigitation of decyl chain in L2 allowed phenyl-phenyl
stacking interactions (Fig. S5).
peak (Tmax:
242 ꢁC). Compound L2 has shown two thermal
decomposition steps. The mass loss of the compound starts at
around 100 ꢁC. In the first decomposition step, ~10% of the total
mass was removed from sample in the 100e170 ꢁC followed by an
endothermic peak at 147 ꢁC (Tmax). In the second step, rest of the
organic moiety of the compound decomposed at 170e290 ꢁC
leaving no residue.
The mesomorphic behaviours of the synthesised two vanillin
derivatives [4-(heptyloxy)-3-methoxybenzaldehyde (L1) and 4-
(decyloxy)-3-methoxybenzaldehyde (L2)] were investigated by
differential scanning calorimetry (DSC) and polarizing optical mi-
croscope via a heating/cooling stage. The DSC thermograms for the
compounds are shown in Fig. 11. On the DSC measurement, com-
pound L1 an endothermal peak at 38 ꢁC and this peak is assigned to
the melting of the compound. The melting of L1 can be clearly seen
by polarizing optic microscopy (POM) in which the compound
melted to isotropic liquid at 38 ꢁC. The melting peak of L1 is narrow
with the enthalpy change of 22.37 J/g showing a clear crystalline
state [16]. In the cooling scan of DSC measurement indicated that
compound L1 crystallized directly from the isotropic liquid at
11.9 ꢁC. Both DSC measurements and polarizing optic microscopy
showed no mesophase transition on the heating or cooling cycle for
compound L1. On the heating cycle, compound L2 showed one
endothermal peak at 52.88 ꢁC (Tmax) which was due to the melting
of the compound which can be seen in POM image given in Fig. S6.
The melting of the compound was accompanied by an enthalpy
change of 323.86 J/g. On the cooling scan, isotropic liquid / crys-
tallisation peak was observed in the 0e10 ꢁC. The increasing the
alkoxy chain of the compound L2 has caused an increase in the
melting point of the compound. This may be due to fully inter-
digitation of the alkoxy chain resulting in higher lattice energy [17].
The interdigitation of the alkyl chains in L2 was confirmed by single
3.2. Thermal properties
Thermal properties of the compounds L1 and L2 have investi-
gated by using thermogravimetric (TG) and differential thermal
analysis (DTA) methods in the 25e900 ꢁC temperature range under
nitrogen atmosphere at a heating rate of 10 ꢁC/min. TGA and DTA
curves of the compounds L1 and L2 have been given in Fig. 10. The
compounds show the different decomposition processes. The
compound L1 undergoes to mass loss in only one step. In
170e240 ꢁC range, the compound showed a sharp mass los and 93%
of the total mass was lost. The rest of the organic moiety was lost up
to the higher temperatures leaving no residue in the samples. In
DTG curve of the L1, this mass loss corresponds to the endothermic
Fig. 10. Thermal curves for L1 and L2.

M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
11
Fig. 11. DSC thermograms of L1 and L2 on heating/cooling stage.
crystal X-ray crystallography.
decyloxy groups have been prepared. The solid-state structures of
the compounds were investigated by single crystal X-ray diffraction
studies. The X-ray data revealed that fully interdigitation occurred
when decyloxy group present in the structure of L2. Thermal be-
haviours of the compounds were investigated under inert
4. Conclusion
In this work, two vanillin derivatives containing heptyloxy or

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M. Tümer et al. / Journal of Molecular Structure 1199 (2020) 127018
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Acknowledgement
The authors are thankful to the Scientific & Technological
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Appendix A. Supplementary data
Supplementary data to this article can be found online at
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