Synthesis and phase behavior of dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid with different functional groups in focal point

Article abstract of DOI:10.1007/s12039-015-0945-4

A number of dendrons of various chain lengths derived from the esters of 3,4,5-tris(tetradecyloxy)benzoic acid were synthesized. These esters were used as building blocks in the design of polyester molecules. Intermediate products, such as branched compou

Full text of DOI:10.1007/s12039-015-0945-4

c
J. Chem. Sci. Vol. 127, No. 10, October 2015, pp. 1801–1810. ꢀ Indian Academy of Sciences.
DOI 10.1007/s12039-015-0945-4
Synthesis and phase behavior of dendrons derived from
3,4,5-tris(tetradecyloxy)benzoic acid with different functional groups
in focal point
MATVEY GRUZDEVa,∗, ULYANA CHERVONOVAa, OLGA AKOPOVAb
and ARKADIY KOLKERa
aG A Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo 153045, Russia
bNanomaterials Research Institute, Ivanovo State University, Ivanovo 153025, Russia
e-mail: gms@isc-ras.ru
MS received 18 February 2015; revised 12 May 2015; accepted 20 July 2015
Abstract. A number of dendrons of various chain lengths derived from the esters of 3,4,5-tris(tetrade-
cyloxy)benzoic acid were synthesized. These esters were used as building blocks in the design of polyester
molecules. Intermediate products, such as branched compounds with variation of functional groups in focal
point (aromatic acids and their benzyl esters, aldehydes of different generation) were obtained. The structure
and purity of all the compounds were determined by elemental analysis, FT-IR, NMR spectroscopy, mass spec-
trometry (MALDI-ToF). The phase behavior was investigated by differential scanning calorimetry and con-
firmed by polarized optical microscopy. Consequently, it was established that the liquid-crystalline properties
of this series of dendrons arise from the degree of branching. This behavior can be explained by the formation
of hydrogen bonds, as well as microsegregation processes of the links of the macromolecule.
Keywords. Dendron; building block; derivatives of benzoic acids; liquid crystalline properties; branching
degree; microsegregation.
1. Introduction
Commonly, branched oligomers can be described as
calamitic molecules with disturbed linearity. One of
the factors which promotes the development of meso-
morphic properties, along with formation of dimers by
hydrogen bonds,15 is microsegregation16 of the flexible
nonpolar periphery and the rigid structure of the polar
focal point of the dendron. Indeed, lateral substituents,
such as CnH2n+1, abruptly reduce the clearing point
with increasing length, and influence the stability of
mesophase by suppressing it existence.17 Previously we
synthesized mesomorphic aldehydes comprizing a long
alkyl residue, which acted as building blocks in the pro-
duction of iron (III) metallocomplexes which showed
spin-crossover properties.18,19
The purpose of the present research is the synthesis
of monodendrons with different degrees of branching,
derived from 3,4,5-tris(tetradecyloxy)benzoic acid, and
determination of the dependence of phase behavior on
molecular structure. Thus prepared dendrons are used
as precursor to Schiff bases in complexation reaction
of spin-cross over metal containing systems.20 Recent-
ly, magnetic properties of a new den−drimeric spin
crossover Fe(III) complex, [Fe(L)2]+PF6 , where L =
3,5-di[3,4,5-tris(tetradecyloxy)benzoyloxy]benzoyl-4-
salicylidene-N-ethyl-N-ethylenediamine, was reported
Dendrimers and dendrons are highly branched globu-
lar macromolecules with precise structures, prepared
through iterative synthesis.1 Current architectures that
enable the elaboration of self-assembling dendrons that
provide supramolecular dendrimers which are able
to self-organize in periodic arrays2 are elaborated
from dendrons containing anisotropic mesogenic repeat
units,3–5 mesogenic dendrons and dendrimers,6 amor-
phous or liquid dendrimers containing mesogenic
groups on their periphery and from polymer back-
bones dendronized with self-assembling dendrons.7,8 It
is known that altering the end group functionality,9,10
as well as other structural modifications,11 influence
the thermal properties of the dendritic molecules. The
thermotropic liquid crystal mesophases of dendritic
molecules containing 3,4-bis-dodecyloxybenzoic acid,
3,5-bis-dodecyloxybenzoic acid or 3,4,5-trisubstituted
benzyl ether monodendrons moieties, in the periph-
ery and as monodendrons, and other feasible mon-
odendrons, have been studied extensively by Percec
et al.10,12–14
∗For correspondence
1801

1802
Matvey Gruzdev et al.
(M++Na). CHNO analysis (%): Calcd. for C49H90O5:
C 77.52; H 11.94; O 10.54. Found: C 76.78; H 12.59;
O 10.63. 1H NMR (CDCl3, TMS, δ, ppm): 0.81 (t, 9H,
CH3-Alk, J=7.32 Hz); 1.19 (m, 54H, -CH2-Alk); 1.41
(t, 6H, Alk-CH2-CH2-O-, J=6.71 Hz); 1.68 (m, 6H, -
CH2-Alk); 1.75 (m, 6H, -CH2-Alk); 3.95 (m, 6H, Alk-
CH2-O); 7.19 (s, 2H, Ph-H); 11.98 (s, 1H, COOH).
13C NMR (CDCl3, TMS, δ, ppm): 14.11 (CH3-), 22.69
(CH3-CH2-), 26.06 (CH3-CH2-CH2-), 29.70 (CH2-Alk),
31.92 (O-CH2-CH2-CH2-), 69.14 (O-CH2-Alk), 73.52
(O-CH2-CH2-), 108.47 (CHarom), 123.58 (Carom), 143.10
(Carom), 152.82 (Carom), 171.87 (C(O)OH). FT-IR (KBr)
νmax/cm−1: 4326, 4250 (intermolecular hydrogen bond),
3418 (OH), 3081 (aromatic vibrations of C-H), 2921-
2850 (-CH2-), 2637-2530 (-CH3-), 1688 (C=O), 1130
(-C-O-C-), 989-969 (flat deformational C-H vibrations
of 1,3,4,5-substituted aromatic ring), 936 (-OH), 866
(non-planar deformational C-H vibrations of 1,3,4,5-
substituted aromatic ring).
for the first time.20 EPR studies show that this com-
pound undergoes a gradual spin transition in the
temperature range 70–300 K and has antiferromagnetic
ordering below 10 K. Mössbauer spectroscopy at 5 K
confirms the presence of magnetic ordering in the
dendrimeric iron complex.
2. Experimental
2.1 Materials and Methods
All the reagents and solvents were of chemically pure
grade and were used without further purification. Ben-
zyl ester of 3,5-dihydroxybenzoic acid was synthesized
by the method in reference.21 FT-IR spectra of com-
pounds were recorded on a Bruker Vertex 80V device in
the region of 7500-370 cm−1 in KBr pellets. The NMR
spectral studies on the nuclei 1H (500.17 MHz) and 13C
(125.76 MHz) were recorded on a Bruker Avance-500
spectrometer. Elemental analysis of crystalline com-
pounds was carried out on a FlashEA 1112 analyzer.
The standard error of measurement is plus or minus
0.9%. Mass-spectra were obtained using the MALDI-
ToF method on a Bruker Daltonics Ultraflex mass-
spectrometer in the positive ion-mode using reflection
option; the matrix was 2,5-dihydroxybenzoic acid. Thin
layer chromatography was performed on the chromato-
graphic plates PolyGRAM, Sil G/UV 254; the eluent
was chloroform. Thermopolarization microscopy was
performed on a MIN-8 microscope with a heating plate
of a custom design. Differential scanning calorimetry
measurements were carried out on a NETZCH DSC
204 F1 device in aluminium capsules, the weight of the
sample ≈ 10 mg, the heating rate was 10◦C/min in N2
atmosphere.
2.2b 3,4,5-Tris(tetradecyloxy)benzoyloxy-2-hydroxy-
benzaldehyde (2): A weighed sample of compound
(1) (6.00 g; 7.9 mmol) was dissolved in dichlormethane.
2,4-Dihydroxybenzaldehyde (1.09 g; 7.9 mmol) was
added and the mixture was stirred until complete
dissolution of the components. Then a sample of dicy-
clohexylcarbodiimide (2.25 g; 10.9 mmol) was added.
The reaction mixture was stirred for 30 min. After
that, a catalytic amount of dimethylaminopyridine was
added and the mixture was stirred for 12 h. Precipi-
tated urea was filtered off on a glass filter. The solvent
was removed on a rotary evaporator. The residue was
chromatographed on silica gel by chloroform. The
product was freeze dried from benzene. Yield: 5.61 g
(80.6%). MS MALDI-ToF (m/z): found 902.33, cal-
culated 902.36 (M++Na). CHNO analysis (%): Calcd.
for C56H94O7: C 76.49; H 10.77; O 12.74. Found: C
2.2 Synthesis of the dendrons
1
75.93; H 11.17; O 12.70. H NMR (CDCl3, TMS,
2.2a 3,4,5-Tris(tetradecyloxy)benzoic acid (1): The δ, ppm): 0.81 (t, 9H, CH3-, J=6.10 Hz); 1.28-1.19
batches of tetradecyl bromide (20.22 g; 72.92 mmol) (m, 54H, -CH2-Alk); 1.41 (t, 6H, Alk-CH2-CH2-O-,
and ethyl ester of 3,4,5-trihydroxybenzoic acid (4.89 g; J=6.10 Hz); 1.69 (m, 6H, -CH2-Alk); 1.76 (m, 6H,
28.74 mmol) were dissolved in 200 mL acetone. Then -CH2-Alk); 3.97 (m, 6H, Alk-CH2-O); 6.83-6.79 (d,
4% NaOH in C2H5OH was added, and the mixture was 2H, Ph-H, J=7.93 Hz); 7.19 (s, 1H, Ph-H); 7.56-7.54
refluxed for 8 h. The reaction was monitored by thin- (d, 2H, Ph-H, J=8.54 Hz); 9.82 (s, 1H, OH-); 11.19
layer chromatography (TLC). The reaction mixture was (s, 1H, COH). 13C NMR (CDCl3, TMS, δ, ppm):
poured out into 1 M solution of HCl. After two days the 14.15 (CH3-), 22.72 (CH3-CH2-), 26.09 (-CH2-), 29.41
solid residue was filtered off and the solvent was dis- (-CH2-), 29.72 (-CH2-), 29.74 (-CH2-), 30.37 (-CH2-),
tilled in vacuum. The product was dissolved in diethyl 31.96 (CH3-CH2-CH2-), 69.30 (-O-CH2-Alk), 73.64
ether and this solution was purified by chromatogra- (-O-CH2-Alk), 108.64 (CHarom), 110.98 (CHarom),
phy on aluminum oxide. The solvent was removed 114.18 (CHarom), 118.69 (Carom), 123.06 (Carom), 134.97
on a rotary evaporator. Yield: 15.00 g (80%). MS (CHarom), 143.39 (Carom), 153.04 (Carom), 157.82 (Carom),
MALDI-ToF (m/z): found 781.94, calculated 782.25 163.21 (Carom-OH), 164.06 (C(O)O), 195.52 (CHO).

Dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid
1803
FT-IR (KBr) νmax/cm−1: 4329, 4253 (intermolecular
hydrogen bond), 3433 (OH), 3091 (aromatic CH vibra-
tions), 2919-2848 (CH2-), 1727 (C=O), 1386 – 1274
(Ph-CHO), 1193 (Alk-C-O-C(Ph)), 982 (flat deforma-
tional C-H vibrations of 1,3,4,5-substituted aromatic
ring), 873 (OH).
with hydrogen in a steel hydrogenation reactor. After
that, a solution of 8.46 g of compound (3) in 100 mL of
dioxane was added and the reaction mixture was stirred
at 50◦C under hydrogen (4 atm) until the necessary
amount of hydrogen was consumed. The reaction mix-
ture was twice filtered through a glass filter, and solvent
was removed on a rotary evaporator. The residue was
dissolved in benzene and freeze dried to obtain a white
solid product. Yield: 5.01 g (62.5%). MS MALDI-ToF
(m/z): found 1657.06, calculated 1659.59 (M++Na).
CHNO analysis (%): Calcd. for C105H182O12: C 77.06;
H 11.21; O 11.73. Found: C 76.65; H 12.10; O 11.25.
1H NMR (CDCl3, TMS, δ, ppm): 0.80 (m, 18H, Alk-
CH3); 1.18 (m, 54H, -CH2-Alk); 1.42 (s, 12H, O-CH2-
CH2-Alk); 1.69 (m, 12H, -CH2-Alk); 1.77 (m, 12H,
-CH2-Alk); 3.97 (m, 12H, O-CH2-Alk); 7.33 (s, 4H, Ph-
H); 7.35 (s, 1H, Ph-H); 7.81 (d, 2H, Ph-H, J=1.83 Hz).
13C NMR (CDCl3, TMS, δ, ppm): 14.15 (CH3-), 22.71
(CH3-CH2-), 26.11 (-CH2-Alk), 29.41-29.77 (-CH2-
Alk), 30.37 (-O-CH2-CH2-), 31.96 (CH3-CH2-CH2-),
69.29 (-O-CH2-Alk), 73.63 (-O-CH2-Alk), 108.57
(CHarom), 123.48 (Carom), 143.29 (Carom), 152.97 (Carom),
164.48 (C(O)OH). FT-IR (KBr), νmax/cm−1: 4334, 4249
(intermolecular hydrogen bond), 3414 (OH), 3088 (aro-
matic vibrations of C-H), 2920-2852 (-CH2-), 2632
(-CH3-), 1751 (C=O), 1122 (-C-O-C), 999 (flat defor-
mational C-H vibrations of 1,3,4,5-substituted aromatic
ring), 924 (-OH), 856 (non-planar deformational C-H
vibrations of 1,3,4,5-substituted aromatic ring).
2.2c Benzyl ester of 3,5-di[3,4,5-tris(tetradecyloxy)
benzoyloxy]benzoic acid (3): A weighed sample of
compound (1) (13.11 g; 17.27 mmol) was dissolved in
dichlormethane. Benzyl ester of 3,5-dihydroxybenzoic
acid (2.11 g; 8.64 mmol) was added and the mixture was
stirred until complete dissolution of the components.
Then a sample of dicyclohexylcarbodiimide (3.02 g;
14.63 mmol) was added and the reaction mixture was
stirred for 30 min. After that, a catalytic amount of
dimethylaminopyridine was added and the mixture was
stirred for 12 h. Precipitated urea was filtered off on
a glass filter. The solvent was removed on a rotary
evaporator. The residue was chromatographed on sil-
ica gel by chloroform. The product was recrystallized
from a 1:1 acetonitrile–chloroform mixture and fil-
tered off. Yield: 13.21 g (88.53%). MS MALDI-ToF
(m/z): found 1748.22, calculated 1749.71 (M++Na).
CHNO analysis (%): Calcd. for C112H188O12: C 77.91;
H 10.97; O 11.12. Found: C 77.41; H 11.84; O 10.75.
1H NMR (CDCl3, TMS δ, ppm): 0.89 (t, 18H, Alk-
CH3, J=5.49 Hz); 1.34-1.26 (m, 108 H, -CH2-Alk);
1.49 (s, 12H, -CH2-Alk); 1.76 (m, 12H, -O-CH2-Alk);
1.83 (m, 12H, -CH2-Alk); 4.04 (m, 12H, Alk-CH2-O-
); 5.38 (s, 2H, O-CH2-Ph); 7.32 (s, 2H, Ph-H); 7.36
(s, 2H, Ph-H); 7.39 (m, 4H, Ph-H); 7.44 (s, 2H, Ph-
H); 7.83 (s, 2H, Ph-H). 13C NMR (CDCl3, TMS, δ,
ppm): 14.14 (CH3-), 22.71 (CH3-CH2-), 26.09 (-O-
CH2-CH2-CH2-), 29.41 (CH3-CH2-CH2-CH2-), 29.66
(-O-CH2-CH2-), 30.37 (-CH2-Alk), 31.95 (CH3-CH2-
CH2-), 67.31 (-CH2-), 69.27 (-O-CH2-Alk), 73.61
(-O-CH2-Alk), 108.57 (CHarom), 120.64 (CHarom),
123.16 (CHarom), 128.45 (CHarom), 128.67 (CHarom),
132.34 (CHarom), 135.56 (Carom), 143.26 (Carom), 151.42
(Carom), 153.02 (Carom), 164.51 (C=O), 164.84 (C=O).
FT-IR (KBr), νmax/cm−1: 4321, 4253 (intermolecular
hydrogen bond), 3414 (OH), 3069 (aromatic vibra-
tions of C-H), 2922-2849 (-CH2-), 2631 (-CH3-), 1729
(C=O), 1228-1194 (flat deformational C-H vibrations
of 1,3,4,5-substituted aromatic ring), 1115 (-C-O-C-),
890-856 (non-planar deformational C-H vibrations of
1,3,4,5-substituted aromatic ring).
2.2e 3,5-Di[3,4,5-tris(tetradecyloxy)benzoyloxy]ben-
zoyl-4-oxy-2-hydroxybenzaldehyde (5): Compound
(5) was obtained from (4) similar to (2) described
earlier. The product was recrystallized from the 1:1
acetonitrile–chloroform mixture and filtered off. Yield:
1.37 g (63.63%). MS MALDI-ToF (m/z): found
1778.19, calculated 1779.69 (M++Na). CHNO analy-
sis (%): Calcd. for C112H186O14: C 76.58; H 10.67; O
1
12.75. Found: C 76.48; H 11.15; O 12.37. H NMR
(CDCl3, TMS, δ, ppm): 0.81 (t, 18H, CH3-Alk, J=6.71
Hz); 1.18-1.29 (m, 108H, -CH2-Alk); 1.42 (m, 12H,
-O-CH2-CH2-Alk); 1.69 (m, 12H, -CH2-Alk); 1.77 (m,
12H, -CH2-Alk); 3.98 (m, 12H, -O-CH2-Alk); 6.79 (s,
1H, Ph-H); 6.83 (m, 1H, Ph-H); 7.19 (s, 1H, Ph-H);
7.34 (m, 4H, Ph-H); 7.39 (s, 1H, Ph-H); 7.56 (s, 2H,
Ph-H); 7.89 (m, 2H, Ph-H); 7.93 (s, 1H, Ph-H); 9.83
(s, 1H, OH); 11.19 (s, 1H, COH). 13C NMR (CDCl3,
TMS, δ, ppm): 14.09 (CH3-), 22.67 (CH3-CH2-), 26.06
(-CH2-), 29.26-30.33 (-CH2-), 31.91 (CH3-CH2-CH2-),
2.2d 3,5-Di[3,4,5-tris(tetradecyloxy)benzoyloxy] ben- 69.25 (-O-CH2-Alk), 73.59 (-O-CH2-Alk), 108.57
zoic acid (4): The calculated amount of catalyst 5% (CHarom), 114.01 (CHarom), 120.92 (Carom), 121.94
Pd/C (0.56 g) was mixed with dioxane and activated (CHarom), 122.91 (CHarom), 130.72 (Carom), 134.92

1804
Matvey Gruzdev et al.
(CHarom), 143.37 (Carom), 145.63 (Carom), 151.65 (Carom), 14.39 (CH3-), 22.66 (CH3-CH2-), 26.02 (-CH2-), 26.07
152.99 (Carom), 163.17 (Carom-OH), 164.46 (C(O)O), (-CH2-), 29.28 (-CH2-), 29.35 (-CH2-), 30.31 (-CH2-),
195.48 (CHO). FT-IR (KBr), νmax/cm−1: 4326, 4253 31.89 (CH3-CH2-CH2-), 69.24 (-O-CH2-Alk), 73.58
(intermolecular hydrogen bond), 3420 (-OH), 3103 (-O-CH2-Alk), 108.55 (CHarom), 120.88 (CHarom),
(aromatic vibrations of CH), 2910-2850 (-CH2-), 120.94 (CHarom), 122.97 (CHarom), 130.74 (Carom),
1738 (C=O), 1393–1288 (Ph-CHO), 1196 (Alk-C- 131.19 (Carom), 143.29 (Carom), 149.48 (Carom), 151.61
O-C(Ph)), 984 (flat deformational C-H vibrations of (Carom), 152.99 (Carom), 164.44 (C(O)O), 167.14
1,3,4,5-substituted aromatic ring), 873 (OH).
(COOH). FT-IR (KBr), νmax/cm−1: 4326, 4266 (inter-
molecular hydrogen bond), 3328 (OH), 3094 (aro-
matic vibrations of CH-), 2929-2850 (-CH2-), 1738
(C=O), 1117 (-C-O-C-), 1003 (flat deformational C-H
vibrations of 1,3,4,5-substituted aromatic ring), 892
(OH).
2.2f Benzyl ester 3,5-di[3,5-bis(3,4,5-tris(tetradecy-
loxy) benzoyloxy)benzoyloxy]-benzoic acid (6): Com-
pound (6) was obtained from (4) similar to (3).
Yield: 6.38 g (70.58%). MS MALDI-ToF (m/z): found
3494.08/3509.17, calculated 3499.39 (M++NH4)/
3504.39 (M++Na). CHNO analysis (%): Calcd. for
2.2h 3,5-Di[3,5-bis(3,4,5-tris(tetradecyloxy)benzoy-
loxy)benzoyloxy]-benzoyloxy-benzaldehyde (8): Com-
pound (8) was obtained from (7) similar to (2). Yield:
2.51 g (68.39%). MS MALDI-ToF (m/z): found
3519.97, calculated 3511.37 (M++NH4). CHNO anal-
ysis (%): Calcd. for C224H370O28: C 76.62; H 10.62;
O 12.76. Found: C 77.13; H 10.63; O 12.24. 1H
NMR (CDCl3, TMS, δ, ppm): 0.81 (t, 36H, CH3-Alk,
J=3.05 Hz); 1.19-1.29 (m, 216H, -CH2-Alk); 1.42 (m,
24H, -O-CH2-CH2-Alk); 1.69 (m, 24H, -CH2-Alk);
1.76 (m, 24H, -CH2-Alk); 3.98 (m, 24H, -O-CH2-Alk);
7.19 (s, 2H, Ph-H); 7.30 (s, 4H, Ph-H); 7.34 (s, 8H,
Ph-H); 7.40 (m, 2H, Ph-H); 7.48 (s, 1H, Ph-H); 7.89 (s,
1H, Ph-H); 7.92 (s, 2H, Ph-H); 9.83 (s, 1H, OH); 11.19
(s, 1H, COH). 13C NMR (CDCl3, TMS, δ, ppm): 14.09
(CH3-), 22.68 (CH3-CH2-), 26.07 (-CH2-), 29.35-30.68
(-CH2-), 31.91 (CH3-CH2-CH2-), 69.29 (-O-CH2-Alk),
73.59 (-O-CH2-Alk), 108.61 (CHarom), 117.67 (CHarom),
121.13 (Carom), 122.98 (Carom), 143.36 (Carom), 151.63
(Carom), 153.03 (Carom), 164.44 (C(O)O), 199.33 (CHO).
FT-IR (KBr), νmax/cm−1: 4326, 4253 (intermolecular
hydrogen bond), 3315 (OH), 3103 (aromatic vibrations
of CH-), 2951-2859 (-CH2-), 1738 (C=O), 1393–1279
(Ph-CHO), 1187 (Alk-C-O-C(Ph)), 1003 (flat deforma-
tional C-H vibrations of 1,3,4,5-substituted aromatic
ring), 883 (OH).
C
224H372O26: C 77.28; H 10.77; O 11.95. Found: C
1
76.77; H 11.29; O 11.94. H NMR (CDCl3, TMS, δ,
ppm): 0.80 (m, 36H, CH3-Alk); 1.18-1.29 (m, 216H,
-CH2-Alk); 1.42 (m, 24H, -O-CH2-CH2-Alk); 1.69 (m,
24H, -CH2-Alk); 1.77 (m, 24H, -CH2-Alk); 3.98 (m,
24H, -O-CH2-Alk); 5.31 (s, 2H, -O-CH2-Ph); 7.19 (s,
1H, Ph-H); 7.27-7.29 (d, 2H, Ph-H, J=7.32 Hz); 7.34
(d, 8H, Ph-H, J=14.04 Hz); 7.37-7.39 (d, 4H, Ph-H,
J=8.54 Hz); 7.79 (s, 2H, Ph-H); 7.90 (s, 3H, Ph-H).
13C NMR (CDCl3, TMS, δ, ppm): 14.11 (CH3-), 22.68
(CH3-CH2-), 26.07 (-CH2-), 29.37 (-CH2-), 29.69
(-CH2-), 30.33 (-CH2-), 31.91 (CH3-CH2-CH2-), 67.36
(-CH2-Ph), 69.24 (-O-CH2-Alk), 73.58 (-O-CH2-Alk),
108.53 (CHarom), 121.14 (CHarom), 122.96 (CHarom),
128.41 (CHarom), 128.65 (CHarom), 130.92 (Carom),
143.28 (Carom), 150.99 (Carom), 151.61 (Carom), 162.99
(C(O)O), 164.44 (C(O)O). FT-IR (KBr), νmax/cm−1:
4335, 4253 (intermolecular hydrogen bond), 3420
(OH), 3094 (aromatic vibrations of C-H), 2929-2850
(-CH2-), 2666 (CH3-), 1738 (C=O), 1187 (flat defor-
mational C-H vibrations of 1,3,4,5-substituted aromatic
ring), 1127 (-C-O-C-), 892 (non-planar deformational
C-H vibrations of 1,3,4,5-substituted aromatic ring).
2.2g 3,5-Di[3,5-bis(3,4,5-tris(tetradecyloxy)benzoy-
loxy)benzoyloxy]-benzoic acid (7): Compound (7)
was obtained from (6) similar to (4). Yield: 3.81 g
(70.41%). MS MALDI-ToF (m/z): found 3406.23,
3. Results and Discussion
calculated 3409.30 (M++NH4). CHNO analysis (%): 3,4,5-Tris(tetradecyloxy)benzoic acid (1) was selected as
Calcd. for C217H366O26: C 76.86; H 10.88; O 12.27. the initial compound, and was synthesized in compli-
1
Found: C 76.27; H 10.99; O 12.74. H NMR (CDCl3, ance with a standard method.22 For the regular branching,
TMS, δ, ppm): 0.80 (m, 36H, CH3-Alk); 1.18-1.29 (m, the method of doubling molecular size was employed,
216H, -CH2-Alk); 1.42 (m, 24H, -O-CH2-CH2-Alk); using the benzyl ester of 3,5-dihydroxybenzoic acid23,24
1.69 (m, 24H, -CH2-Alk); 1.76 (m, 24H, -CH2-Alk); (scheme 1). The benzyl ester of 3,5-dihydroxybenzoic
3.98 (m, 24H, -O-CH2-Alk); 7.19 (s, 4H, Ph-H); 7.34 acid, employed as a protecting block in the esterifi-
(s, 8H, Ph-H); 7.39 (s, 2H, Ph-H); 7.82 (s, 1H, Ph-H); cation, was prepared by means of alkylation of the
7.91 (s, 2H, Ph-H). 13C NMR (CDCl3, TMS, δ, ppm): carboxyl group of 3,5-dihydroxybenzoic acid with

Dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid
1805
C14H29
O
C14H29
O
O
O
DCC, DMAP
CHCl3
O
H
O
C14H29
O
O
H
HO
C14H29
O
+
OH
C14H29O
OH
C14H29O
OH
(2)
(1)
C14H29
C14H29
O
O
O
O
C14H29
O
O
HO
DCC, DMAP
C14H29
O
O
O
O
O
O
C14H29
O
+
2
OH
C
H2
C14H29
O
C
H2
CH2Cl2
C14H29
HO
O
O
C14H29
O
(1)
(3)
C14H29
O
50 oC
Pd/C
H2
4 atm
C14H29
C14H29
C14H29
O
1,4-dioxane
O
O
O
O
HO
HO
C14H29
C14H29
O
O
C14H29
O
O
O
O
C14H29
O
O
C
H2
O
O
C14H29
C14H29
O
O
O
C14H29
O
O
O
O
OH
C14H29
O
O
O
O
O
C
H2
DCC, DMAP
CH2Cl2
C14H29
O
(4)
C14H29
O
O
O
C14H29
O
C14H29
O
O
(6)
C14H29
C14H29
C14H29
O
DCC
DMAP
O
O
H
HO
O
O
CH2Cl2
OH
O
C14H29
O
40 oC
Pd/C
H2
4 atm
O
O
C14H29
O
1,4-dioxane
C14H29
O
O
O
O
H
C14H29
O
C14H29
O
C14H29
O
O
O
O
C14H29
O
OH
C14H29
O
O
C14H29
O
(5)
C14H29
C14H29
O
O
O
O
O
C14H29
O
O
O
C14H29
O
O
C14H29
C14H29
C14H29
O
OH
O
C14H29
O
O
O
O
HO
O
H
C14H29
O
O
O
OH
O
C14H29
C14H29
C14H29
O
DCC
DMAP
O
C14H29
C14H29
O
O
O
O
O
O
CH2Cl2
O
O
C14H29
O
O
O
O
(7)
C14H29
O
O
O
H
C14H29
O
O
O
OH
C1H29
O
O
C14H29
C14H29
C14H29
O
O
O
(8)
O
O
Scheme 1. Synthesis of compounds (1)–(8).

1806
Matvey Gruzdev et al.
benzyl bromide in dry DMF.25 The hydroxyl groups
location in the structure of the benzyl ester of 3,5-
dihydroxybenzoic acid are sterically favorable for fur-
ther molecular growth. The protecting group is easily
introduced into the molecule, and selectively removed
without any alterations in the structure of the formed
compound. Additionally, the protecting group is stable
in the presence of a large number of reagents used for
further reactions.
The esterification was carried out by interaction
between the carboxyl and hydroxyl groups with the aid
of dicyclohexylcarbodiimide in dichloromethane. The
benzyl group was selectively removed by hydrogenol-
ysis using 5% Pd-C as catalyst in dry 1,4-dioxane26
(scheme 1). The aldehydes (2), (5) and (8) were obtain-
ed by means of esterification of the corresponding acid
and para-hydroxysalicylic aldehyde.
signal of –CH2–Ph at 5.38 and 5.31 ppm, respectively.
Mass-spectra of compounds (3) and (6) demonstrate
doubling of molecular mass from 1748 [M++Na] (3) to
3498 [M++NH4] (6).
In the NMR spectra of compounds (2), (5), and (8),
the signal of the –COH proton is located in the weak
field range at 9.8 ppm, and the signal at 11.19 ppm
refers to the –OH proton. The mass-spectra of the alde-
hydes show molecular ions which are stabilized by
sodium and ammonium ions. The values are doubled in
series from (2) to (5) and from (5) to (8).
The thermal stability and phase behavior of com-
pounds (1)-(8) were studied by differential scanning
calorimetry and polarized optical microscopy. Conse-
quently, it was established that liquid crystalline prop-
erties are detected with increasing branching degree in
a homologous series, summarized in table 1.
Thus, 3,4,5-tris(tetradecyloxy)benzoic acid (1) turns
into an isotropic liquid at Tiso = 70–71◦C in the heating
cycle without forming a mesophase. Cooling of the
sample initially leads to the growth of needle-shaped
crystals. The data of DSC experiments confirm the
results of polarized microscopy, table 1. Lengthening
of compound (1) to (2) does not promote the formation
of a mesophase. For this sample, a “solid-solid” type
phase transition at T = 31.96◦C (ꢀH = 10.02 kJ/mol)
and formation of an isotropic liquid at Tiso = 64–65◦C
are characterized in the heating cycle. Cooling of the
sample is accompanied by the growth of crystals, start-
ing from Tcr = 34◦C. Data of DSC experiments confirm
the results of microscopy.
In comparison with samples (1) and (2), compound
(3) has a more branched structure and does not have
terminal polar groups, which leads to the occurrence
of enantiotropic mesomorphism (figure 2). After exam-
ination of sample (3) by polarized microscopy, it was
established that a mesophase appears after reheat-
ing, i.e. upon second heating (figure 2c). Sample (3)
flows anisotropically by pressing at T = 30–48◦C. Upon
cooling, the sample becomes too cold, and anisotropy
appears at T = 17◦C as a nongeometric (planar) texture
(figure 2a). Data of POM agrees with the differential
scanning calorimetry data (figure 2b). As stated above,
the feature in these kinds of esters is a protected active
functional group which promotes the formation of a
mesophase at the expense of microsegregation of the
molecules. Upon first heating, the mesophase is difficult
to detect because the system is very viscous and the
compound is similar to an oligomer. After first heating
and cooling, the sample is ordered, and this leads to
the occurrence of a mesophase upon reheating (second
heating). The exothermic peak in the heating process
just before the peak at T = 48.48◦C corresponds to
The structure of the compounds was established by
FT-IR, NMR, MALDI-ToF mass-spectrometry (matrix-
assisted laser desorption/ionization) and elemental
analysis. To aid identification of the products, reference
markers were used. This allowed us to determine the
structure and the extent of the reactions.
The results of NMR spectroscopy showed that the
integrated intensity of the alkyl fragments of acids (1),
(4) and (7) increases with generation number. The R–
CH2–O– fragments in the 3,4,5-position of gallic acid
are used as reference signals which characterize the
molecular growth, i.e. the ratio of protons in R–CH2–
O– to acids (1)/(4)/(7) is 6/12/24, respectively.
For acids (1), (4) and (7), it was found that the molecu-
lar ions are stabilized by sodium and ammonium ions.
The data of MALDI-ToF analyses are given in figure 1.
The mass of the molecular ions increased exponentially.
For esters (3) and (6), the formation of product after
introducing the benzyl fragment was confirmed by the
Figure 1. MS MALDI-ToF spectra of acids (1), (4), and (7).

Dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid
1807
Table 1. The phase transition temperatures of compounds 1–8 according to DSC, during heating and cooling cycles.
Peak phase-transition temperatures [◦C]
Compound
Thermal cycle
(transition enthalpies [kJ/mol])
C49H90O5 (1)
C56H99O7 (2)
1st heating
1st cooling
1st heating
1st cooling
2nd heating
2nd cooling
1st heating
1st cooling
2nd heating
2nd cooling
2nd heating
2nd cooling
1st heating
1st cooling
1st heating
1st cooling
Cr 72.69 (84.43) → Iso
Iso 47.11 (-84.51) → Cr
Cr 31.96* (10.02)* → Cr 64.51 (99.02) → Iso
Iso 34.11 (-80.11) → Cr
C
112H188O12 (3)
105H182O12 (4)
Cr 30.69 (72.18) → Mes 48.48 (12.61) → Iso
Iso 17.61 (-88.99) → Mes 1.67 (-1.21) → Cr
C
Cr 47.61 (33.88) → Mes 50.68 (-21.49) → Cr 82.34 (102.45) → Iso
Iso 30.89 (-67.75) → Mes -66.14 (-2.41)[a] → Cr [a]
Cr 31.96 (26.53) → Mes 55.49 (20.03) → Iso
Iso 40.44 (-8.43) → Mes 20.34 (-25.47) → Cr
Cr 49.51 (218.28)* → Mes 59.98 (*) → Iso
Iso 34.32 (-107.82) → Mes [a]
C112H182O14 (5)
224H370O28 (6)
C
C217H366O26 (7)
C224H370O28 (8)
Cr 60.37 (4.07) → Iso
Iso 55.35 (-24.76) → Mes 14.29 (-51.55) [b]
Cr 50.01 (11.24) → Iso
Iso 36.52 (-31.53) → Mes 17.53 (-66.36) → Cr [a]
Note: * - total area under curve; Cr - crystalline phase; Mes - mesophase; Iso - isotropic liquid. [a] Transition only observed
after several day at room temperature. [b] Isotropic liquid at room temperature. No DSC peaks were detected below room
temperature
some restructuring process in the development of the mesomorphism, but under the condition that samples
mesophase under heating.
must be orientated. Unfortunately, such investigations
Removal of the protective benzene group from com- are impossible owing to high viscosity. When we ob-
pound (3) leads to an increase in the mesophase thermo tained the microphotos, we encountered complications
stability of compound (4), and an extention of the tem- owing to the considerable viscosity of the samples and
perature region of its existence (figure 3). Microscopic difficulty in obtaining samples with a large domain
observations of sample (4) show that the mesophase texture.
with an uncharacteristic texture arises at Tmes = 50◦C
Extention of compound (4) on the phenyl ring, and
during the heating cycle (texture is nonrelevant), and the presence of two polar groups in the ortho-position
it turns into an isotropic liquid at Tiso = 80◦C via a leads to a small decrease in the mesophase thermal sta-
mesophase transition (table 1). This process of crys- bility (compound (5)). Characteristic texture mesophase
tallization is possible explained by aggregation of (4) of aldehyde (5) was not observed under first heat-
which reaches a plateau after Tcr = 50◦C within the ing. A mesophase was observed only upon reheating.
investigated range of 49–71◦C.27 These aggregates are Anisotropy appears in the sample after 20–30 min. follo-
stable until further warming to Tiso. Upon cooling, the wing cooling cycle.
sample becomes too cold and anisotropic parts appear
Further modification of compound (4) to compound
at room temperature only after a long time of exposure (6) leads to a reduction of the mesophase thermal sta-
of the sample. Figure 3a shows an acinous fine domain bility, as compared with (4) (figure 4). Transition to an
texture, and against the background are large domains isotropic liquid is observed at Tiso = 59.98◦C (figure 4c).
of mesophase which appear as a helical track. In addi- The texture of a mesophase is more characteristic upon
tion, two phase transitions during the heating cycle are reheating. During cooling, anisotropy appears as a non-
registered on the DSC curve (figure 3b). The thermo- geometric texture, figure 4a, for the thick sample, and
grams of compounds (3) and (4) (by themselves) are not as oily striations to the thin sample, figure 4b. Such
indicative of a mesophase, but the description of micro- behavior can denote a chirality of the mesophase.
scopic observation gives evidence for enantiotropic
Removal of the protective group from compound (6)
mesomorphism. Unfortunately, characteristic textures are impairs the conditions for development of mesomor-
not observed upon heating, but a mesophase is revealed phism in compound (7), which turns into an isotropic
by the fluidity of the compound upon pressure and a liquid upon melting (Tiso = 60◦C). During cooling, a tex-
change of the rotation of crossed polarizers at 45 and ture with a great number of anisotropic points which
90 degrees. Undoubtedly, investigation of the com- lengthen, move, and change simultaneously were ob-
pounds by X-ray diffraction might to help us to confirm served. The sample shows monotropic mesomorphism.

1808
Matvey Gruzdev et al.
(a)
(b)
Tmes=30.69 oC
ΔH=72.18 kJ/mol
Tiso=48.48 oC
ΔH=12.60 kJ/mol
2nd heating
1st cooling
Tmes=17.61 oC
ΔH= -89.09 kJ/mol
0
25
50
75
100
125
T, oC
(c)
Figure 2. (a) Nongeometric texture of compound (3), heating cycle, T = 47◦C; (b) DSC curves of
compound (3) in heating and cooling cycle. (c) DSC curves of compound (3) at 1st and 2nd heating.
Introduction of a phenyl ring with two polar groups a non-geometric texture (figure 5). Subsequent cooling
into compound (7) yields compound (8), which vitrifies leads to the appearance of a coloured anisotropic pat-
from the mesophase. Compound (8) melts at T = 44◦C tern which does not change under shear stress, which
and turns into an isotropic liquid at Tiso = 50◦C. Upon characterizes anisotropic glass (Tg = −10.41◦C, ꢀCp
cooling, a mesophase is formed at Tmes = 36◦C with = 0.45 J/(g*K)).
(a)
(b)
°
T
C
iso= 82.34
ΔH = 101.79 kJ/mol
°
C
Tmes= 47.60
ΔH = 33.88 kJ/mol
1st heating
1st cooling
°
C
Tmes= 30.89
ΔH = -67.75 kJ/mol
0
25
50
75
100
125
T, oC
Figure 3. (a) Fine domain texture of compound (4), cooling cycle, T = 29◦C;
(b) DSC curves of compound (4) in heating and cooling cycles.

Dendrons derived from 3,4,5-tris(tetradecyloxy)benzoic acid
1809
(a)
(b)
(c)
Tmes= 49.51 oC
T
iso= 59.98 oC
2nd heating
1st cooling
ΔH = 218.28 kJ/mol
T = 34.32 oC
ΔH = -107.57 kJ/mol
0
25
50
75
100
125
T, oC
Figure 4. (a) Nongeometric texture of the thick sample (6) in cooling cycle,
T = 49◦C; (b) oily striations texture of the thin sample (6), T = 20◦C, cooling
cycle; (c) DSC curves of the sample in heating and cooling cycles.
acid (1) at 1688 cm−1 assigned to the C=O stretching
of the carboxylic acid shifted to 1751 cm−1 (4) and
1738 cm−1 (7), (figure 6), indicating that the carboxylic
acids (1), (4) and (7) are quantitatively formed the
hydrogen bond by formation of symmetrical and asym-
metrical dimers at lengthening of molecules.
In conclusion, we have synthesized a new series of
compounds derived from the esters of 3,4,5-tris(tetra-
decyloxy)benzoic acid (2)-(8). It was found that starting
from ester (3), mesomorphic properties are revealed, and
they depend on the presence of polar terminal groups in
compounds(2), (4), (5), (7)and(8)which take part in the
formation of hydrogen bonds. For compounds (3) and
(6), a mesophase is formed primarily by microsegrega-
tion. Increasing the molecular mass in series from (2) to
(8) leads to anisotropic vitrification of compound (8).
The IR measurement of all compounds demonstrates
the formation of complementary hydrogen bonds bet-
ween fragments of polar groups in the case of carbox-
ylic acid, aldehydes and esters. The IR absorption of
This situation is further supported by the fact that the
H-stretching peaks in the IR spectrum appears in the
Figure 6. Fragments of FT-IR spectra of acids (1), (4) and
Figure 5. Texture of mesophase, cooling cycle, T = 36◦C. (7) in the H-bonded region.

1810
Matvey Gruzdev et al.
H-bonded region (below 3400 cm−1).28 In particular,
compound (1)–(8) have been found to interact in dimers
by double intermolecular H-bonds and by intramolecu-
lar H-bonds.29
5. Meier H and Lehmann M 1998 Angew. Chem. Int. Ed.
37 643
6. Cameron J H, Facher A, Lattermann G and Diele S 1997
Adv. Mater. 9 398
7. Tian Y Q, Kamata K, Yoshita H and Iyoda T 2006 Chem.
Eur. J. 12 584
8. Frauenrath H 2005 Prog. Polym. Sci. 30 325
9. Turrin C-O, Maraval V, Leclaire J, Dantras E,
Lacabanne C, Caminade A-M and Majoral J-P 2003
Tetrahedron 59 3965
4. Conclusions
A new series of compounds derived from esters of
3,4,5-tris(tetradecyloxy)benzoic acid were synthesized. 10. Ropponen J, Tamminen J, Lahtinen M, Linnanto J,
Rissanen K and Kolehmainen E 2005 Eur. J. Org. Chem.
2005 73
11. Ropponen J, Tuuttila T, Lahtinen M, Nummelin S
and Rissanen K 2004 J. Polym. Sci. Part A. 42
5574
12. Percec V, Cho W-D, Ungar G and Yeardley D J P 2001
J. Am. Chem. Soc. 123 1302
It was established that liquid-crystalline properties of
this series of dendrons arise from of the degree of
branching. This behavior can be explained by the for-
mation of hydrogen bonds, as well as processes of
microsegregation of the links of the macromolecule.
13. Percec V, Won B C, Peterca M and Heiney P A 2007 J.
Am. Chem. Soc. 129 11265
Supplementary information (SI)
14. Percec V, Peterca M, Dulcey A E, Imam M R, Hudson
S D, Nummelin S, Adelman P and Heiney P A 2008 J.
Am. Chem. Soc. 130 13079
15. Grebenkin M F and Ivaschenko A V 1989 In Liquid
crystalline materials (Moscow: Khimiya) p. 228
16. Tschierske C 2001 J. Mater. Chem. 11 2647
17. Pegenau A, Hegmann T, Tschierske C and Diele S 1999
Chem. Eur. J. 5 1643
All additional information pertaining to characterization
of the compounds using NMR spectra, FT-IR spectra
and mass-spectra are given in the supporting informa-
tion. The electronic supporting information can be seen
in www.ias.ac.in/chemsci.
18. Chervonova U V, Gruzdev M S, Kolker A M, Manin
N G and Domracheva N E 2010 Rus. J. Gen. Chem. 80
1954
19. Chervonova U V, Gruzdev M S and Kolker A M 2011
Rus. J. Gen. Chem. 81 1853
20. Vorobeva V E, Domracheva N E, Pyataev A V, Gruzdev
M S and Chervonova U V 2015 Low Tem. Phys.
41 15
Acknowledgements
This work was supported by the grant of Russian Foun-
dation for Basic Research No. 14-03-31280-mol_a and
the grant of the President of the Russian Federation
(No. MK-70.2014.3). Dr. Akopova O.B. is thankful for
the grant of Ministry of education and science RF (No.
4.106.2014K). EA, NMR, FT-IR spectroscopy and DSC 21. Chervonova U V, Gruzdev M S and Kolker A M 2011
Rus. J. Gen. Chem. 81 2288
22. Schaz A, Valaityte E and Lattermann G 2005 Liq. Cryst.
32 513
23. Tully D C, Wilder K, Fréchet J M J, Trimble A R and
Quate C F 1999 Adv. Mater. 11 314
analysis were carried out by the equipments of Interlab-
oratory scientific center «Verhnevolzhskij region center
of physicochemical researching». The authors would
like to thank Dr. Simon Dalgleish (Nagoya University)
for useful discussion.
24.
Saudan C, Balzani V, Gorka M, Lee S-K, Maestri M,
Vicinelli V and Vögtle F 2003 J. Am. Chem. Soc. 125
4424
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