Binary systems of non-mesogens with naphthalene derivatives

Article abstract of DOI:10.1080/15421406.2020.1856503

Binary mixtures with both the components are non-mesogenic becomes an interesting and enlighten feature when they exhibit mesomorphism at ambient temperature. In the present study, we report five binary systems where two non-mesogenes exhibit smectic and/or nematic mesophases at ambient temperature over a certain range of concentration. All the binary systems contain one non-mesogenic naphthalene derivative. The study provides many binary systems of non-mesogens which exhibit mesophases at ambient temperatures. The terminal nitro chain is found to be responsible for the induction of both the nematogenic and smectogenic tendency in the present investigation of binary systems with two ‘compatible' component.

Full text of DOI:10.1080/15421406.2020.1856503

Molecular Crystals and Liquid Crystals
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gmcl20
Binary systems of non-mesogens with
naphthalene derivatives
Yong fang Yao, H. N. Patel, Ashish Kumar Prajapati, Chetan B. Sangani &
Yong-Tao Duan
To cite this article: Yong fang Yao, H. N. Patel, Ashish Kumar Prajapati, Chetan B. Sangani &
Yong-Tao Duan (2020) Binary systems of non-mesogens with naphthalene derivatives, Molecular
Crystals and Liquid Crystals, 712:1, 31-42, DOI: 10.1080/15421406.2020.1856503
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MOLECULAR CRYSTALS AND LIQUID CRYSTALS
2020, VOL. 712, NO. 1, 31–42
https://doi.org/10.1080/15421406.2020.1856503
Binary systems of non-mesogens with naphthalene
derivatives
Yong fang Yaoa,b,c, H. N. Pateld, Ashish Kumar Prajapatie, Chetan B. Sanganid, and
Yong-Tao Duana
aHenan Provincial Key Laboratory of Pediatric Hematology, Children’s Hospital Affiliated to Zhengzhou
b
University, Henan Children’s Hospital, Zhengzhou Children’s Hospital, Zhengzhou, China; School of
c
Pharmaceutical Science, Zhengzhou University, Zhengzhou, Henan, China; Ministry of Education of
China, Key Laboratory of Advanced Drug Preparation Technologies (Zhengzhou University), Zhengzhou,
d
China; Shri Maneklal M. Patel Institute of Sciences & Research, kadi sarva vishwavidyalaya,
e
Gandhinagar, Gujarat, India; Chemistry Department, Faculty of Science, The M.S. University of Baroda,
Vadodara, India
KEYWORDS
ABSTRACT
Binary mixtures;
Binary mixtures with both the components are non-mesogenic
becomes an interesting and enlighten feature when they exhibit meso-
morphism at ambient temperature. In the present study, we report
five binary systems where two non-mesogenes exhibit smectic and/or
nematic mesophases at ambient temperature over a certain range of
concentration. All the binary systems contain one non-mesogenic
naphthalene derivative. The study provides many binary systems of
non-mesogens which exhibit mesophases at ambient temperatures.
The terminal nitro chain is found to be responsible for the induction
of both the nematogenic and smectogenic tendency in the present
investigation of binary systems with two ‘compatible’ component.
component; naphthalene;
nematogenic; non-
mesogenic; smectogenic
Introduction
“Liquid crystals with low crystal-mesophase transition temperatures and with wide
phase length have been the primary goal of organic chemists in recent years. Since the
occurrence of a single component, room temperature liquid crystal with a wide meso-
phase range is rare. It is necessary to mix two or more low melting materials which
may give room temperature mesomorphic mixture with wide mesophase length.
In general binary systems exhibiting mixed mesomorphism can be of three types: (i)
where both the components are mesomorphic, (ii) Where only one component is meso-
morphic and (iii) Where both the components are non-mesomorphic. Several workers
[1–8] studied these types of mixed mesomorphism and discussed the structure-proper-
ties relationship in binary mixtures. Mesogenic binary systems of swallow-tailed and a
double swallow-tailed compound [9], swallow-tailed and laterally branched liquid crys-
tals [10], bi-swallow-tailed and a terminally-polar compound [11], as well as double-
swallow tailed and calamitic electron acceptor compounds [12], are also appeared in the
CONTACT H. N. Patel
hemant_2patel@yahoo.co.in
Shri Maneklal M. Patel Institute of Sciences & Research, kadi
sarva vishwavidyalaya, Gandhinagar, Gujarat, India
ß 2021 Taylor & Francis Group, LLC

32
Y. F. YAO ET AL.
literature. Kramarenko et al. [13–15] presented a phase diagram with a wide TGB phase
region for certain binary liquid crystalline systems and then established the influence of
the chiral dopant molecular structure on the type of phase diagram and the TGB
regions. Dabrowski and Brodzik [16] discussed the influence of aliphatic chain length
on the induction of smectic - A phase in polar bicomponent mixtures.
Good numbers of research papers are reported on binary mixtures in which induced
mesophases are exhibited because of intermolecular hydrogen bonding [17–29]. It is
well known that hydrogen bonds may be formed between carboxyl (-C ¼ O-) and amide
(-NH-) groups in poly (amides). Hydrogen bond formation between a carboxylate
acceptor and a urea donor, and in some similar systems, was also reported
recently [30–33].
Early studies on binary mixtures have suggested the formation of mixed mesomor-
phism from the pairs of compounds which are non-mesogenic by them [34–36]. Bennet
and Jones [37] reported that 4-methoxy benzoic acid and 4-ethoxy benzoic acid which
are non-mesogenic, do exhibit nematic mesophase in their binary mixtures. Lohar [38]
has confirmed this result and showed that mixtures of the two acids exhibit mixed
mesomorphism over a small range of temperature and concentration. Gupta and Vora
[39] have reported a few binary mixtures where both the components are non-meso-
genic exhibit mesomorphism with the non-linear tendency of the transition temperature
curve. Vora et al. [40] observed the induced mesomorphism in the binary mixture were
both the components belong to different homologous series. One of the components
possesses a nitro group while another component is an ester with -CH3 or -COOC4H9
terminal group. Physical properties of individual mesogens may or may not undergo
modifications in their mixtures. Sometimes, the modifications become characteristic,
thereby making the study of mixtures important. Earlier studies [40–46] have suggested
the formation of mixed mesomorphism by mixing compounds where none, one, or
both of them are mesogens. The emergence of the mesophase [47], increase or decrease
in the mixed mesomorphic ranges and thermal stabilities and study of the factors that
influence the modifications have received a greater attention. The binary mixtures of
mesogens have provided better formulations for applications in the different field [48].
Dave & Patel re-reported binary systems of structurally similar and dissimilar mesogens
and nonmesogens. They also reported four binary systems consisting of structurally dis-
similar mesogens and the study of their effect on mixed mesomorphism, arising due to
the differences in structural characteristics of these components. Further, Dave et al.
reported four binary systems consisting of azo-ester mesogens with nonmesogenic and
mesogenic carboxy esters to examine the properties of mixed mesophases [49].
Prajapati et al. reported [50] the induction of smectic mesophase in the binary mix-
tures of esters having terminal broken alkyl chain in one of the components. Mahajan
et al. [29] have reported induction of mesophases by intermolecular hydrogen bonding
in a few binary mixtures were both the components are non-mesogenic by themselves.
Recently, Prajapati and Pandya have reported [51] six binary systems where two non-
mesogens exhibit smectic and/or nematic mesophase at ambient temperature over a
wide range of concentration. With the continuation of previous work in naphthalene
derivative; the series of 20-Napthayl-4-n-alkoxy benzoates, there was methoxy to penty-
loxy derivatives exhibit non-mesogenic same in 4-n octyloxy and hexadecyloxy phenyl

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
33
Scheme 1. Synthetic route to compound (i) to compound (vi).
azo-2’methalene. So above combination of non-mesogenus were prepared. They exhib-
ited mesophase in present reported work.
Binary mixtures with both the components are non-mesogenic becomes an interesting
and enlighten feature when they exhibit mesomorphism at ambient temperature. In the
present study, we report few binary systems where two non-mesogenes exhibit smectic
and/or nematic mesophases at ambient temperature over a certain range of concentra-
tion. All the binary systems contain one non-mesogenic naphthyl derivative.

34
Y. F. YAO ET AL.
Experimental
Preparation of compounds
The Scheme 1 shows the detail of the synthetic route for the preparation of following
present compounds.
i. 2-Naphthyl-4’-n-propyloxybenzoate (3 BN).
ii. 2-Naphthyl-4’-n-butyloxybenzoate (4 BN).
iii. 2-Naphthyl-4’-n-pentyloxybenzoate (5BN).
iv. 4-(4’-n-Butyloxybenzoyloxy) nitrobenzoate (4 BNB).
Were synthesized by the condensation of respective 4-n-alkoxy benzoic acid with 2-
naphthol [compound (i) - (iii)], 4-nitro phenol [compound (iv)] respectively by follow-
ing the procedure described by Dave and Vora [52].
i. 4-n-Octyloxy phenyl azo-2’-naphthalene (8PN).
ii. 4-n-Hexadecyloxyphenylazo-2’naphthalene (16PN).
Were synthesized [53] by alkylation of 4-hydroxyphenylazo-2’naphthalene which in
turn is obtained by diazotization and coupling of 20-amino naphthalene with phenol.
20-Naphthyl-4-n-pentyloxybenzoate:[5BN]
IR spectrum (KBr) ꢀꢀm1ax/cmꢀ1: 2919, 1726 (-COO-), 1600, 1470, 1428, 1312, 1240,
1170, 840, 825, 735 cm
.
4-(40-n-Butyloxybenzoyloxy) nitrobenzoate [4 BNB].
IR spectrum (KBr) ꢀmax/cmꢀ1: 2918, 1724 (-COO-), 1602, 1510 (-NO2)1472, 1428,
ꢀ1
1311, 1241, 1176, 842, 824, 738 cm
.
4-n-Octyloxy phenylazo-20-naphthalene (8PN).
. IR spectrum (KBr) ꢀmax/cmꢀ1: 2950, 2835, 1610 (-N ¼ N-) 1590, 1505, 1470, 1415,
ꢀ1
1270, 1150, 875, 830, 755 cm
Preparation of binary mixtures
Both the components were weighed accurately in known proportion and melted
together in fusion tubes. The mixtures were thoroughly mixed to obtain a homogeneous
mixture. The melt was quenched and the solid obtained was ground finely and was
used for determining transition temperatures.
The transition temperatures were determined by using a Leitz Laborlux 12 POL
microscope provided with a heating stage. The transition temperatures were determined
on heating as well as cooling.
Results and discussion
System No.
Component A
Component B
I
II
III
IV
V
3BN
4BN
5BN
8PN
16PN
þ
þ
þ
þ
þ
4BNB
4BNB
4BNB
4BNB
4BNB

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
35
Plate 1.1. Photomicrograph of system III for 37.92 mole% at 51 ꢁC.
Plate 1.2. Photomicrograph of system IV for 08.66mole% at 52 ꢁC.
Table 1. Transition temperatures (ꢁC) for system–I.
Mole % of A
Cr
N
I
00.00
06.89
14.20
23.89
30.76
39.99
50.00
60.87
72.73
85.71
100.00
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
60
65
67
79
77
80
86
95
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
56)
61)
65)
63)
64)
108
118
122
Values in the parenthesis indicate monotropy.

36
Y. F. YAO ET AL.
Table 2. Transition temperatures (ꢁC) for the system–II.
Mole % of A
Cr
N
I
00.00
06.61
13.74
21.45
29.82
38.93
48.88
59.80
71.83
85.16
100.00
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
60
70
76
83
92
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
54)
56)
60)
64)
68)
98
106
110
114
116
120
Table 3. Transition temperatures (ꢁC) for system–III.
Mole % of A
Cr
SmA
N
I
00.00
06.35
13.24
20.74
28.93
37.92
47.81
58.76
70.96
84.61
100.00
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
60
64
47
57
55
85
90
92
94
95
96
ꢂ
(ꢂ
ꢂ
61)
67
74
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
75
(ꢂ
57)
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
71)
70)
68)
65)
61)
Values in the parenthesis indicate monotropy.
The following ten binary mixtures having both the components non-mesogenic
are studied.
The transition temperatures of the system I-V are given in Tables 1–5 respectively,
the plots of transition temperatures versus mole percent are given in Figures 1–5.
System I: 3BN þ 4BNB

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
37
Table 4. Transition temperatures (ꢁC) for system–IV.
Mole % of A
Cr
N
I
00.00
08.66
17.94
27.27
36.84
46.66
56.75
67.12
77.77
87.73
100.00
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
60
63
69
72
87
89
90
92
94
95
109
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
56)
62)
70)
84)
85)
85)
85)
86)
86)
Values in the parenthesis indicate monotropy.
Table 5. Transition temperatures (ꢁC) for system–V.
Mole % of A
Cr
N
I
00.00
06.90
14.29
22.24
30.79
40.02
50.02
60.89
72.74
85.72
100.00
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
60
65
73
78
80
86
87
88
90
92
95
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
(ꢂ
63)
70)
76)
78)
83)
85)
85)
85)
86)
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
(ꢂ
Values in the parenthesis indicate monotropy.

38
Y. F. YAO ET AL.
Figure 1. Phase behavior of system I.
Figure 2. Phase behavior of system II.
Figure 3. Phase behavior of system III.
Reference to binary phase diagram (Figure 1) exhibits an induced monotropic nem-
atic phase between 06.89 to 39.99 mole percentage concentrations of 3BN. The nematic
isotropic transition temperature curve is extrapolated on the side where monotropic

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
39
Figure 4. Phase behavior of system IV.
Figure 5. Phase behavior of system V.
nature is observed up to certain concentration range [36,37, 54–57]. The latent transi-
tion temperature obtained by extrapolation for 4BNB is 51 ꢁC.
System II: 4BN þ 4BNB
Reference to binary phase diagram (Figure 2) exhibits an induced monotropic nem-
atic phase between 06.61 to 38.93 mole percentage concentrations of 4BN. The nematic
isotropic transition temperature curve is extrapolated on the side where monotropic
nature is observed up to certain concentration range [36,37, 54–57]. The latent transi-
tion temperature obtained by extrapolation for 4BNB is 52 ꢁC.
System III: 5BN þ 4BNB
Reference to binary phase diagram (Figure 3) exhibits an induced monotropic nem-
atic phase between 06.35 to 84.81 mole percentage concentration of 5BN and mono-
tropic smectic A appears only at 37.92% concentration of 5BN. The latent transition
temperature obtained by extrapolation for 4BNB is 51 ꢁC.
System IV: 8PN þ 4BNB

40
Y. F. YAO ET AL.
Reference to binary phase diagram (Figure 4) shows that the system is non-mesogenic
when the concentration of 8PN is low but the monotropic nematic phase is induced
from 08.6 to 87.73 mole percentage concentration of 8PN. The latent transition tem-
perature obtained by extrapolation for 4BNB is 52 ꢁC.
System V:16PN þ 4BNB
Reference to binary phase diagram (Figure 5) shows that the system is non-mesogenic
when the concentration of 16PN is low but the monotropic nematic phase is induced
from 06.90 to 85.72 mole percentage concentration of six PN. The latent transition tem-
perature obtained by extrapolation for 4BNB is 50 ꢁC.
Conclusion
The study provides several binary systems of non-mesogens which exhibit mesophases
at ambient temperatures.
The terminal nitro chain is found to be responsible for the induction of both the
nematogenic and smectogenic tendency in the present investigation of binary systems
with two ‘compatible’ component i. e. one with an ester central linkage with naphtha-
lene moiety and the other with an ester central linkage having a nitro chain. In the pre-
sent work, even though the two components are ‘compatible’ i.e. one having central azo
linkage and other with an ester central linkage induced nematic/smectic phase in the
binary system IV and V binary system. The study provided the few binary systems of
non-mesogens which exhibited liquid crystalline properties at ambient temperatures.
Values in the parenthesis indicate monotropy.
Funding
This work was supported by National Natural Science Foundation of China (Project
No. 81903623 and 22007086), the China Postdoctoral Science Foundation (No. 2019M652586
and 2020M670083ZX), Henan science and technology key project (No. 202102310148) and
Henan Medical Science and Technology Program (No. 2018020601 and SBGJ202003051).
Authors are thankful to Kadi SarvaVishwavidhyalaya for providing laboratory facility.
Refrences
[1] A. Bogojawalensky, and N. Winogradow, Z. Phys. Chem. 64, 229 (1908).
[2] J. S. Dave, and M. J. S. Dewar, J. Chem. Soc., 4616 (1954). J. Chem. Soc. 4305 (1955). doi:
10.1039/jr9540004616
[3] J. S. Dave, and J. M. Lohar, Proc. Nat. Acad. Sci., India, 29A, 35 (1960). J. Chem. Soc, A.
2A, 1473 (1967). doi:10.1039/j19670001473
[4] J. S. Dave, and K. L. Vasant, Pramana. Supp. No. 1 2, 125 (1976). 415 (1975).
[5] J. S. Dave, and R. A. Vora, Liquid Crystals and Plastic Crystals, Vol. 2, Physico-chemical
Properties and Methods of Investigation, edited by G. W. Gray and P. A. Winsor
(Chichester, England, Ellis, Harwood Ltd., 1974), p. 161.
[6] G. W. Smith, Mol. Cryst. Liq. Cryst. 30 (1–2), 101 (1975). 49, 27 (1978). doi:10.1080/
15421407508082845
[7] B. Ziemnicka et al., Mol. Cryst. Liq. Cryst. 132 (3–4), 289 (1986). doi:10.1080/
00268948608079549

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
41
[8] M. E. Neubert, K. Leung, and A. Saupe, Mol. Cryst. Liq. Cryst. 135 (3–4), 283 (1986). doi:
10.1080/00268948608084815
[9] H. Stettin, H. Kresse, and W. Weissflog, Mol. Cryst. Liq. Cryst. 162 (2), 139 (1988). doi:10.
1080/00268948808084454
[10] S. Heinemann, H. Kresse, and W. Weissflog, Cryst. Res. Technol. 28 (1), 131 (1993). doi:
10.1002/crat.2170280123
[11] S. Haddawi et al., Liq. Cryst. 17 (2), 191 (1994). doi:10.1080/02678299408036559
[12] I. Letko et al., Liq. Cryst 19, 535 (1995).
[13] N. L. Kramarenko et al., Liq. Cryst 37, 1266 (1992). (in Russian); 17, 351 (1994).
[14] N. L. Kramarenko et al., Zhurn. Fiz. Khikii. 68, 1008 (1994).
[15] N. Kramarenko et al., Liq. Cryst. 22 (5), 535 (1997). doi:10.1080/026782997208910
[16] R. Dabrowski, and M. Brodzik, Liq. Cryst. 18 (1), 61 (1995). doi:10.1080/
02678299508036591
[17] T. Kato, and J. M. J. Frechet, J. Am. Chem. Soc. 111 (22), 8533 (1989). doi:10.1021/
ja00204a044
[18] U. Kumar et al., Angew. Chem. Int. Ed. Engl. 31 (11), 1531 (1992). doi:10.1002/anie.
199215311
[19] H. Kresse et al., Mol. Cryst. Liq. Cryst 238 (1), 13 (1994). doi:10.1080/10587259408046912
[20] T. Kato et al., Liq. Cryst. 14 (5), 1311 (1993). doi:10.1080/02678299308026444
[21] H. Kresse et al., Mol. Cryst. Liq. Cryst. 257 (1), 19 (1994). doi:10.1080/10587259408033758
[22] T. Kato and J. M. J. Frecher, Macromol. Symp. 98 (1), 311 (1995). doi:10.1002/masy.
19950980127
[23] Y. Tian et al., Liq. Cryst. 19 (6), 743 (1995). doi:10.1080/02678299508031093
[24] H. Kresse et al., SPIE 222 (1995), (2372).
[25] H. Bernhardt, W. Weissflog, and H. Kresse, Angew. Chem. Int. Ed. Engl. 35 (8), 874
(1996); Mol. Cryst. Liq. Cryst 301 (1997). doi:10.1002/anie.199608741
[26] A. Treybig et al., Mol. Cryst. Liq. Cryst. 300 (1), 127 (1997). doi:10.1080/
10587259708042343
[27] J. J. Price et al., J. Mater. Chem. 7 (6), 883 (1997). doi:10.1039/a700575j
[28] Y. Tian et al., Mol. Cryst. Liq. Cryst. 309 (1), 19 (1998). doi:10.1080/10587259808045514
[29] R. Mahajan, H. Nandedkar, and V. Suthar, Mol. Cryat. Liq Cryst. 330 (1), 511 (1999). doi:
10.1080/10587259908025628
[30] G. Maier and T. Gribet, Poly. Mater. Sci. Eng. 84, 297 (2001).
[31] B. J. B. Folmer et al., Adv. Mater. 12 (12), 874 (2000). doi:10.1002/1521-
4095(200006)12:12<874::AID-ADMA874>3.0.CO;2-C
[32] A. J. Myles, and N. R. Branda, J. Am. Chem. Soc. 123 (1), 177 (2001). doi:10.1021/
ja002733p
[33] M. Li, C. Guo, and Y. Wu, Liq. Cryst. 29 (8), 1031 (2002). doi:10.1080/
02678290210156696
[34] D. Vorlander and A. Gahren, Ber. Dtsch. Chem. Ges. 40 (2), 1966 (1907). doi:10.1002/cber.
190704002100
[35] A. Bogojawlensky and N. Winogradow, Z. Phys. Chem. 60, 433 (1907); 64, 229
[36] R. Walter, and D. Ber, Ber. dtsch. Chem. Ges. A/B. 58 (10), 2303 (1925). doi:10.1002/cber.
19250581011
[37] G. M. Bennett, and B. Jones, J. Chem. Soc. , 420 (1939). doi:10.1039/jr9390000420
[38] J. M. Lohar and J. De. Phys, Colleq, Cl., 36, Cl-399 (1975).
[39] R. A. Vora and R. Gupta, Mol. Cryst. Liq. Cryst. 106, 147 (1983).
[40] R. A. Vora, R. Gupta, and K. Patel, Mol. Cryst. Liq. Cryst. 209 (1), 251 (1991). doi:10.
1080/00268949108036200
[41] J. S. Dave and K. L. Vasanth, Mol. Cryst. Liq. Cryst. 2, 125 (1966).
[42] J. S. Dave, P. R. Patel, and K. L. Vasanth, Mol. Cryst. Liq. Cryst. 8 (1), 93 (1969). doi:10.
1080/15421406908084900
[43] J. S. Dave, M. R. Menon, and P. R. Patel, Mol. Cryst. Liq. Cryst. 392 (1), 83 (2003). doi:10.
1080/15421400390193927

42
Y. F. YAO ET AL.
[44] A. K. Prajapati, N. S. Patel, and V. G. Lad, Mol. Cryst. Liq. Cryst. 348 (1), 41 (2000). doi:
10.1080/10587250008024794
[45] R. A. Vora, and S. J. Rajput, Mol. Cryst. Liq. Cryst. 209 (1), 265 (1991). doi:10.1080/
00268949108036201
[46] T. N. Govindaiah et al., Mol. Cryst. Liq. Cryst 548, 55 (2011).
[47] J. M. Lohar and J. S. Dave, Mol. Cryst. Liq. Cryst. 103 (1–4), 181 (1983). doi:10.1080/
00268948308071049
[48] M. Hird, J. W. Goodby, and K. J. Toyne, Mol. Cryst. Liq. Cryst 360 (1), 1 (2001). doi:10.
1080/10587250108025694
[49] (a.) J. S. Dave et al., H. Mol. Cryst. Liq. Cryst 587, 80 (2013).
[50] A. K. Prajapati, R. A. Vora, and M. Patel, J. M. S. Univ. Baroda 46 and 47 (3), 87 (1999
and 2000).
[51] A. K. Prajapati and H. M. Pandya, Mol. Cryst. Liq. Cryst 365 (1), 43 (2001). doi:10.1080/
10587250108025280
[52] J. S. Dave and R. A. Vora, Pranama (1), 447 (1975).
[53] H. N. Patel and A. K. Prajapati, Mol. Cryst. Liq. Cryst. 643 (1), 106 (2017). doi:10.1080/
15421406.2016.1262712
[54] J. S. Dave et al., Mol. Cryst. Liq. Cryst 4, 505 (1996); 8, 93 (1966).
[55] J. S. Dave and M. J. S. Dewar, J. Chem. Soc. 4617 (1954), 4305 (1955). doi:10.1039/
jr9550004305
[56] J. M. Lohar and D. S. Shah, Mol. Cryst. Liq. Cryst. 28 (3–4), 293 (1974). doi:10.1080/
15421407408082826
[57] J. S. Dave and K. L. Vasanth, Ind. J. Chem. 7498 (1986).