https://doi.org/10.1140/epjs/s11734-026-02176-3
Regular Article
Phase behaviours, spectroscopic, and DFT analysis of a complementary hydrogen bond liquid crystal complex with enhanced NLO properties
1
Department of Physics, Gobi Arts and Science College, 638453, Gobichettipalayam, Tamil Nadu, India
2
Department of Physics, Condensed Matter Research Laboratory (CMRL), Research Park, Bannari Amman Institute of Technology, 638401, Sathyamangalam, Tamil Nadu, India
3
Department of Physics, Anna University Regional Campus, 625019, Madurai, Tamil Nadu, India
4
UGC-DAE Consortium for Scientific Research, Kalpakkam Node, 603104, Kokilamedu, Tamil Nadu, India
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Received:
10
November
2025
Accepted:
27
January
2026
Published online:
24
February
2026
Abstract
Hydrogen bond liquid crystal (HBLC) complex is obtained from 1,2,3-Propanetricarboxylic acid (PTA; non-mesogen) and 4-(Heptyloxy)benzoic acid (7OBA; mesogen) through a complementary hydrogen bond (H-bond) interaction method. Differential scanning calorimetric analysis is performed to examine the thermal behaviour of PTA + 7OBA (1:3 molar ratio) HBLC complex, and the polarized optical microscopic technique is employed to investigate the induced mesogenic textures. The sequence of phase transitions observed during the endothermic and exothermic cycles are crystal (Cry.) ↔ Smectic F (Sm F) ↔ Smectic C (Sm C) ↔ Nematic (N) ↔ Isotropic (I), exhibiting weakly first-order transitions. The complementary H-bond interaction is validated via FTIR analysis, as evidenced by the observation of bathochromic shift in the hydroxyl (O–H) and carbonyl (C=O) functional groups. UV–visible spectroscopic analysis reveals the complex’s optical transparency throughout the visible region, along with an optical band gap energy of 4.22 eV. In addition, theoretical calculations (based on density functional theory) are used to establish the framework of the PTA + 7OBA complex based on its energy-minimized molecular geometry, quantum theory of atoms in molecules, and molecular electrostatic potential studies. Subsequently, the different molecular interactions such as H-bonding, van der Waals and steric effect are analysed using interaction region indicator analysis. Further, the independent gradient model based on Hirshfeld partition (IGMH) analysis is used to examine the weak noncovalent interactions (δginter) in the HBLC complex. Observed NLO properties of the HBLC are higher than those of the standard reference urea, signifying its potential efficacy in NLO-based photonic applications.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
