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Chinnaiyan Selvarasu and Palaninathan Kannan
– 6.95 (m, 16H), 4.04 (t, 4H, J = 6.5 Hz), 1.80 (q, J Calculated for C48H52N4O2S C 76.96 N 7.48 H 6.99%;
= 6.5 Hz, 4H), 1.42 – 1.23 (m, 28H), 0.85 (t, 6H, J = found C 76.88 N 7.33 H 6.85%.
5.9 Hz).13C NMR (100 MHz, CDCl3); 14.2, 22.5, 25.6,
2.3g N,Nꢁ-((1,3,4-thiadiazole-2,5-diyl)bis(4,1-pheny-
lene))bis(1-(4-(decyloxy)phenyl) methanimine)(6c): FT-
IR (KBr, cm−1): 1596 (C=N), 1606 (CH=N), 1418 (1,
29.3, 31.9 (aliphatic), 68.6 (methoxy), 114.1, 121.4,
127.5, 128.3, 129.6, 131.8, 149.2 (aromatic), 160.2
(CH=N), 161.3, 164.1 (1,3,4-oxadiazole). Elemental
Analysis: Calculated for C48H60N4O3 C 77.80 N 8.15
H 7.56%; found C 77.76 N 8.10 H 7.52%.
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3,4-thiadiazole), 2941 (-Csp -H). H-NMR (400 MHz,
CDCl3): δ 8.65 (s, Ar-CH=N-, 2H), 7.73 – 6.54 (m,
16H), 4.04 (t, 4H, J = 6.5 Hz), 1.82 (q, J = 6.0 Hz,
4H), 1.42 – 1.22 (m, 28H), 0.84 (t, 6H, J = 5.7 Hz).
13C NMR (100 MHz, CDCl3); 14.0, 22.5, 25.4, 29.2,
31.9 (aliphatic), 68.6 (methoxy), 114.2, 121.6, 127.7,
128.4, 129.5, 131.8, 149.4 (aromatic), 160.1 (CH=N),
161.3, 164.4 (1,3,4-thiadiazole). Elemental Analysis:
Calculated for C48H60N4O2S C 76.14 N 7.40 H 7.98%;
found C 76.10 N 7.34 H7.88 %.
2.3d N,Nꢁ-((1,3,4-oxadiazole-2,5-diyl)bis(4,1-pheny-
lene))bis(1-(4-(dodecyloxy)phenyl) methanimine) (5d):
FT-IR (KBr, cm−1): 1591 (C=N), 1610 (CH=N),
1420 (1,3,4-oxadiazole), 2952 (-CSP3-H). 1H NMR
(400 MHz, CDCl3): δ 8.97 (s, Ar-CH=N-, 2H), 7.84
– 6.97 (m, 16H), 4.06 (t, 4H, J = 6.6 Hz), 1.83 (q, J
= 6.4 Hz, 4H), 1.41 – 1.26 (m, 36H), 0.85 (t, 6H, J =
5.9 Hz). 13C NMR (100 MHz, CDCl3); 14.1, 22.6, 25.4,
29.0, 31.9 (aliphatic), 68.4 (methoxy), 114.1, 121.5,
127.8, 128.4, 129.7, 131.9, 149.3 (aromatic), 160.2
(CH=N), 161.2, 164.2 (1,3,4-oxadiazole). Elemental
Analysis: Calculated for C52H68N4O3 C 78.34 N 8.59
H 7.02%; found C 78.03 N 8.52 H 7.0%.
2.3h N,Nꢁ-((1,3,4-thiadiazole-
2,5-diyl)bis(4,1-pheny-
lene))bis(1-(4-(dodecyloxy)phenyl) methanimine) (6d):
FT-IR (KBr, cm−1): 1591 (C=N), 1606 (CH=N),
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1423 (1,3,4-thiadiazole), 2935 (-Csp -H). 1H-NMR
(400 MHz, CDCl3): δ 8.66 (s, Ar-CH=N, 2H), 7.72–
6.89 (m, 16H), 4.03 (t, 4H, J = 6.3 Hz), 1.83 (q, J
= 6.3 Hz, 4H), 1.42–1.24 (m, 36H), 0.83 (t, 6H, J =
5.8 Hz). 13C NMR (100 MHz, CDCl3); 14.0, 22.5, 25.4,
29.3, 31.9 (aliphatic), 68.7 (methoxy), 114.3, 121.4,
127.9, 128.5, 129.6, 131.7, 149.5 (aromatic), 160.4
(CH=N), 161.2, 164.3 (1,3,4-thiadiazole). Elemental
Analysis: Calculated for C52H68N4O2S C 79.01 N 6.88
H 8.42%; found C 79.0 N 6.79 H 8.37%.
2.3e N,Nꢁ-((1,3,4-thiadiazole-2,5-diyl)bis(4,1-pheny-
lene))bis(1-(4-(hexyloxy)phenyl) methanimine) (6a):
The similar procedure was adapted to synthesis of
1,3,4-thiadizole compounds (6a-6d; scheme 1) with
yield: 6a 51%, 6b 56%, 6c 49% and 6d 53%.
6a: FT-IR (KBr, cm−1): 1591 (C=N), 1607 (CH=N),
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1428(1,3,4-thiadiazole), 2936 (-Csp -H). 1H NMR
(400 MHz, CDCl3): δ 8.67 (s, Ar-CH=N-, 2H), 7.74 –
6.94 (m, 16H), 4.05 (t, 4H, J = 6.4 Hz), 1.82 (q, J =
6.1 Hz, 4H), 1.40 – 1.25 (m, 12H), 0.84 (t, 6H, J =
5.8 Hz). 13C NMR (100 MHz, CDCl3); 14.2, 22.6, 25.3,
29.0, 31.8 (aliphatic), 68.4 (methoxy), 114.2, 121.5,
127.7, 128.4, 129.6, 131.8, 149.2 (aromatic), 160.1
(CH=N), 161.3, 164.1 (1,3,4-thiadiazole). Elemental
Analysis: Calculated for C40H44N4O2S C 74.50 N 8.68
H 6.87%; found C 74.28 N 8.56 H 6.74%.
3. Results and Discussion
3.1 Mesophase characterization and thermal
properties
The liquid crystal properties of the compounds 5a-5d
and 6a-6d were studied using DSC. Further, liquid crys-
tal textures were confirmed using HOPM. The com-
pounds 5a–5d and 6a-6d were found to exhibit meso-
morphism and their transition temperatures associated
enthalpy values are summarized in table 1. The phase
transition temperatures observed by polarising opti-
2.3f N,Nꢁ-((1,3,4-thiadiazole-2,5-diyl)bis(4,1-pheny-
lene))bis(1-(4-(octyloxy)phenyl) methanimine)(6b): FT-
IR (KBr, cm−1): 1595 (C=N), 1602 (CH=N), 1423 (1, cal microscopy were in good agreement with the cor-
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3,4-thiadiazole), 2932 (-Csp -H). H-NMR (400 MHz, responding DSC thermograms. Microphotographs of
CDCl3): δ 8.64 (s, Ar-CH=N-, 2H), 7.72 – 6.96 (m, observed textures of 5a-5d are tabulated in figure 1.
16H), 4.05 (t, 4H, J = 6.2 Hz), 1.82 (q, J = 6.2 Hz, Among them, R = 4 was reported earlier by Luminita
4H), 1.42 – 1.25 (m, 20H), 0.85 (t, 6H, J = 5.9 Hz). Marin et al., and it was repeated for comparison needed
13C NMR (100 MHz, CDCl3); 14.1, 22.3, 25.4, 29.2, for the present study.28 The synthesized compounds in
31.9 (aliphatic), 68.5 (methoxy), 114.1, 121.4, 127.8, series I, 5a-5d with varying terminal alkyl chain length
128.3, 129.6, 131.7, 149.4 (aromatic), 160.3 (CH=N), (R = 6, 8, 10 and 12) did not render liquid crys-
161.4, 164.3 (1,3,4-thiadiazole). Elemental Analysis: talline phase, while increase in terminal alkyl chain