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Article

Low-Temperature Metallomesogen Model Structures and Mixtures as Potential Materials for Application in Commercial Liquid Crystal Devices

by
Hassanali Hakemi
Plastic Liquid Crystal Technology Via Lambro 80, MB, 20846 Macherio, Italy
Physchem 2024, 4(4), 447-457; https://doi.org/10.3390/physchem4040031
Submission received: 27 June 2024 / Revised: 21 October 2024 / Accepted: 22 October 2024 / Published: 5 November 2024
(This article belongs to the Section Physical Organic Chemistry)
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Abstract

:
The present work was the preliminary study of phase diagrams and miscibilities of low-temperature metallomesogen (MOM) model structures based on rod-like palladium (Pd) alkyl/alkoxy-azobenzene metal complexes and their mixtures with commercial liquid crystal materials for potential application. The initial results indicated the accessible temperature range and mesgenic miscibility between parent ligand, MOMs and commercial liquid crystal mixtures. The eutectic ligand/MOM composition with other MOMs and commercial nematic liquid crystal materials exhibited complete mesogenic miscibility and wide low-temperature mesogenic stability for eventual utilization in commercial liquid crystal devices.

1. Introduction

Since their discovery, thousands of liquid crystal compounds with a great variety of molecular shapes, geometries, supramolecular structures and mesophase transitions have been reported. As potential materials for application, due to their supramolecular nature, the rod-like nematic, chiral nematic and smectic liquid crystals have been utilized for decades as the main materials in electro-optical display devices [1]. The metal–organic liquid crystals known as “metallomesogens” (MOMs), which consist of metal-complex centers in organic mesogenic structures, have been studied for decades as potential materials for technological applications. The presence of metal complexation in the chemical structures of liquid crystals could add many physical and optical features not present in the organic mesogenic systems. Such features have been the main driving force for potential application of MOMs in a wide range of electro-optical devices as additional selective absorption, large electrical polarizability, refractive index and birefringence, high order parameter, mesogenic stability and dichroic ratios [2,3,4,5,6,7,8]. Therefore, MOMs could offer the possibility of combining the mesogenic supramolecular order with other additional metal-complexation properties. Due to their photophysical and photochemical behaviors, MOMs have also generated great scientific interests, which have been used for relevant applications.
In spite of many developments regarding the chemical structures of MOMs in the past few decades as the active fields of research, there have been few reports regarding their applications in electro-optical and electro-luminescent displays, smart sensors, encryption systems and fuel cells [2,3,4,5,6,7,8,9,10,11]. In recent years, a great variety of MOM materials have been synthesized, with suggestions on their application as photo-luminescent [12,13,14,15], fluorescent [16,17], electroluminescent [11,18], phosphorescence [18,19], magnetic [20,21] and electric [22,23,24,25] materials.
In this context, the luminescent MOMs may be used as multi-functional materials since they combine the ordering of the fluid mesophase with luminescence properties. This kind of compound has received remarkable interest on the basis of the role that liquid crystals have in traditional liquid crystal displays (LCs), especially evident in cost-saving color liquid crystal digital displays [21]. Another widely proposed field of application for MOMs is the development of chromoactive materials, which currently have attracted high interest due to their potential usefulness in the fabrication of sensors, data recording devices and encryption systems, among others [11,12,25,26,27,28,29].
There are other scientific and patent literature on potential applications of rod-like MOMs, such as dichroic dyes, non-linear optics, thermal recording, thermos-chromism, passive optical filters, photo-sensing, laser addressing, optical and thermal recording, polarizing films, radiation absorbing films, ferroelectricity, ferromagneticity, electroconductivity, reaction catalysts, ink jet and security printing and medicinal components [29,30,31,32,33,34,35,36,37,38,39,40].
In spite of extensive scientific and patent literature on the synthesis and characterization of various chemical structures of MOMs, such materials have not yet been fully developed for commercial application, even for the simplest guest–host display systems. The major reasons are the existing drawbacks of the studied MOMs, including their high transition temperatures, inaccessible and limited mesophase range as well as low chemical stability. In fact, MOMs could offer an interesting opportunity to combine the typical properties of metal complexation (dielectric, magnetism, carrier mobility, etc.) with liquid crystal properties through the supramolecular ordering in their mesophase. Consequently, in order to develop qualified MOMs for application, one requires the development of useful materials by eliminating the above-mentioned drawbacks as well as incorporating additional properties of metal complexation that are absent in the conventional liquid crystalline materials. Among the important solutions for commercial development of MOMs are not only by synthesis of stable chemical structures but by developing low-temperature MOMs with an accessible mesogenic phase and their mixing and miscibility approach to expand mesogenic transition temperatures, similar to commercial eutectic liquid crystal products. With respect to MOMs mixing approach, there are a few early and recent studies regarding the phase transitions of mono- and bi-ligand model MOM mixtures by both physical and chemical mixing methods, which provide some insights on their thermal and mesogenic behavior [41,42,43]. Furthermore, there have been some attempts to study the effect of various MOM structures and their mixtures as dichroic dyes for improving the electro-optical performances in polymer dispersed liquid crystal (PDLC) films and commercial liquid crystal materials [38,44,45,46]. In addition, the mixtures of MOMs with commercial liquid crystal materials could also provide further clues on their viability for commercial applications in electro-optical devices.
Considering the extensive literature studies on MOMs, the lack of existing materials for commercial application and their previously mentioned drawbacks, in this work, we attempt to address the accessible mesogenic behavior in a few low-temperature MOMs. Accordingly, we study the phase transitions in low-temperature mono-ligand MOMs and their mixtures, based on palladium alkyl/alkoxy-azobenzene complex structures. Subsequently, we first provide the transition temperatures and phase diagram of a binary mixture of ligand/MOM with the same terminal groups. Secondly, we utilize the eutectic ligand/MOM mixture and mix it with two low-temperature MOMs having different terminal groups. Thirdly, we study the phase diagrams of the eutectic ligand/MOM mixture with low-temperature and high-temperature commercial liquid crystal materials. The results of these studies are described in the following sections.

2. Materials and Methods

The synthesized ligand and MOMs were based on a common class of mono-ligand palladium alkyl/alkoxy-azobenzene metal complexes, whose general chemical formulas are presented in Figure 1.
The original synthetic procedures of ligand and MOM chemical structures have been reported elsewhere [47]. According to Figure 1, the chemical structures of MOMs were obtained by the ligand incorporated in three Pd alkyl/alkoxy-azobenzene complexes having the following chemical compositions:
HL2: R=C6H13; R’=O(CH2)2CH=CH2
L2Pd-acac: R=C6H13; R’=O(CH2)2CH=CH2
L5Pd-acac: R=C6H13; R’=C6H13
L6*Pd-acac: R=OC7H15; R’=O(CH2)2CH(CH3)-(CH2) 2CH=C(CH3)2
According to Figure 1, the HL2 and L2Pd-acac consist of the same R and R’ terminal groups, whereas the chemical structures of L5Pd-acac and L6*Pd-acac consist of different R and R’ terminal groups than those of HL2 and L2Pd-acac. The details of the synthetic procedures of this class of ligand and mono-ligand MOMs have been mentioned elsewhere [41,44,47]. The utilized commercial liquid crystal materials were eutectic E43 (Merck) and TN10427 (Hoffmann La Roche), whose transition temperatures are mentioned in Table 1.
The studied transition temperatures of the ligand, MOMs, E43 and TN10427 mixtures, including the crystal-mesogenic (Tcm) and mesogenic-isotropic (Tmi) transition temperatures on heating mode as well as the isotropic-mesogenic (Tim) and mesogenic-crystal (Tmc) transition temperatures on cooling mode, were determined by a Perkin Elmer DSC7 Differential Scanning Calorimeter (DSC) method. In addition, the phase transitions and mesophase types of the components and mixtures were carried out by a Nikon Eclipse-50i polarizing optical microscope (POM) equipped with a temperature-controlled Mettler FP5 microscopic hot stage.
The phase diagrams of the mixtures were carried out by direct weighing of the components in a DSC pan and through repeated DSC scanning at a heating rate of 10 °C/min and a cooling rate of 5 °C/min until the mixings were completed with no change in their thermograms. The same DSC mixtures were then utilized to determine their liquid crystalline phases by the POM method.

3. Results

In Table 1, we tabulate the crystal-mesogenic (Tcm) and mesogenic-isotropic (Tmi) transition temperatures on heating mode and isotropic-mesogenic (Tim) and mesogenic-crystal (Tmc) transition temperatures on cooling mode of the synthesized low-temperature HL2 ligand, L2Pd-acac, L5Pd-acac and L6*Pd-acac MOMs as well as those of the utilized commercial E43 and TN10427 liquid crystal materials.
According to Table 1, with respect to mesomorphism, the HL2 exhibits an enantiotropic nematic phase with a nematic stability of 9.5 °C on heating and 33 °C on cooling rate. The L2Pd-acac is a monotropic nematic phase with a nematic stability of 55 °C on cooling rate. The L5Pd-acac also exhibits a monotropic nematic phase with a nematic stability of 15 °C on cooling rate. The L6*Pd-acac exhibits an enantiotropic chiral nematic (cholesteric) phase with a mesophase stability range of 16.5 °C on heating and 30 °C on cooling rate.
Also, according to Table 1, we tabulated the transition temperatures of the eutectic mixtures of commercial E43 and TN10427, which exhibit enantiotropic nematic phases with nematic stabilities of 108 °C and 154 °C on cooling rates, respectively.
According to the data of Table 1, the results of our study on the phase diagrams and transition temperatures of the binary HL2/L2Pd-acac mixture as well as the tertiary HL2/L2Pd-acac/L5Pd-acac, HL2/L2Pd-acac/L6*Pd-acac, HL2/L2Pd-acac/E43 and HL2/L2Pd-acac/TN10427 mixtures are described as follows.

3.1. Binary HL2 Ligand and L2Pd-Acac Mixtures

As a model system, we studied the mixtures of low-temperature HL2 ligand and L2Pd-acac MOM having the same R and R’ terminal groups. Accordingly, in Figure 2, we present the transition temperatures and the whole phase diagram of the HL2/L2Pd-acac mixtures only on cooling mode due to the monotropic nematic phase of L2Pd-acac.
With respect to Figure 2, it is noticed that, as a result of the linear trend of the isotropic-nematic (TIN) transitions within the whole compositions of the phase diagram, these low-temperature mixtures exhibit a complete miscibility of the nematic phase. The phase diagram of this ligand/MOM mixture exhibits a distinct eutectic point of nematic-crystal (TNC) at L2Pd-acac = 62.3% concentration with a wide nematic stability range of 81 °C and a low TIN = 46 °C.
Subsequently, we utilized the eutectic point composition (37.7/62.3 wt%) of the HL2/L2Pd-acac mixture and studied the tertiary phase diagrams described in the following sections.

3.2. Tertiary Eutectic HL2/L2Pd-Acac and L5Pd-Acac Mixtures

In Figure 3, we provide the transition temperatures and phase diagram of the tertiary mixtures consisting of the eutectic HL2/L2Pd-acac mixture (37.7/62.3%wt) and L5Pd-acac MOM complex on the cooling mode. Accordingly, such ligand/MOM/MOM mixtures, as a result of the predominantly linear trend of the TIN transitions, exhibit complete nematic miscibility of the components within the whole compositions of the phase diagram. Although this tertiary system does not exhibit a eutectic point of nematic-glass transitions (TNC), it shows a wide low-temperature nematic stability of approximately 80 °C within −35 °C and 45 °C at a concentration range of up to 50% of L5Pd-acac.

3.3. Tertiary Eutectic HL2/L2Pd-Acac and L6*Pd-Acac Mixtures

In Figure 4, we provide the transition temperatures and phase diagram of the tertiary eutectic HL2/L2Pd-acac (37.7/62.3%wt) and L6*Pd-acac MOM complex mixtures. Also, due to the linear trend of the TN*I transitions, this tertiary ligand/MOM/MOM system exhibits a complete chiral nematic miscibility within the whole phase diagram. The phase diagram of this tertiary system also does not provide a eutectic point at nematic-glass transitions, but it shows a wide low-temperature chiral nematic stability of approximately 80 °C within −35 °C and approximately 45 °C at a concentration range of up to 20% of L6*Pd-acac.

3.4. Tertiary Eutectic HL2/L2Pd-Acac and Commercial Liquid Crystal Mixtures

In order to evaluate the eventual utilization of MOMs for eventual application, we also studied the transition temperatures and phase diagrams of the eutectic HL2/L2Pd-acac mixture (37.7/62.3%wt) with commercial low-temperature E43 and high-temperature TN10427 eutectic nematic liquid crystals. Accordingly, in Figure 5, we provide the transition temperatures and phase diagram of the tertiary mixtures of HL2/L2Pd-acac and E43 liquid crystal on cooling mode. The linear trend of the TNI transition temperatures clearly demonstrates the complete miscibility and nematic stability of 81–108 °C range within the whole phase diagram.
In Figure 6, we provide the transition temperatures and phase diagram of the tertiary mixtures of eutectic HL2/L2Pd-acac (37.7/62.3%wt) and commercial high-temperature TN10427 nematic liquid crystal on cooling mode. Due to the linear trend of the TNI transition temperatures, the phase diagram of HL2/L2Pd-acac/TN10427 also demonstrates total miscibility of their mesophase and nematic stability of 81–155 °C range within the whole concentrations of the phase diagram.

4. Discussion

In the present study, we presented a few low-temperature mono-ligand MOM model structures and determined the transition temperatures and phase diagrams of their binary ligand/MOM and tertiary mixtures of eutectic ligand/MOM with two other low-temperature MOMs as well as two commercial liquid crystals in order to demonstrate their potential utilization, such as application in elecro-optical devices. Accordingly, we showed that it is possible to utilize low-temperature MOMs as additional and alternative materials in commercial liquid crystal display materials.
Additionally, we also demonstrated that, in such low-temperature model MOM mixtures, it is possible to obtain accessible and wide mesogenic stability for eventual utilization in commercial liquid crystal materials. The main outcomes of this work on transition temperatures and phase diagrams of the studied binary HL2/L2Pd-acac and tertiary mixtures of HL2/L2Pd-acac with L5Pd-acac, L6*Pd-acac as well as with commercial E43 and TN10427 liquid crystals are further discussed as follows:
  • According to Table 1, the rod-like HL2 ligand and L2Pd-acac MOM structures based on Pd alkyl/alkoxy-azobenzene complexes with the same terminal groups exhibited low transition temperatures with accessible nematic stability ranges of 33.3 °C and 55.1 °C, respectively. Namely, the presence of the Pd metal complex in L2Pd-acac showed a wider nematic range (−12 °C/+43.1 °C) than that of the HL2 ligand (+14.8 °C/+48.1 °C).
Also, according to Figure 2, due to the linearity trend of the TIN transitions, the HL2 and L2Pd-acac exhibited complete nematic miscibility within the whole compositions of their phase diagram. The HL2/L2Pd-acac phase diagram demonstrated the lowest nematic-crystal (TNC) transition and a distinct eutectic point at approximately 62.3% of L2Pd-acac concentration. At this eutectic point, the nematic range of the mixture is widely expanded to 81 °C, namely between TNC = −35 °C and TIN = +45.9 °C temperature range. Aside from other potential MOM properties to be studied, such a eutectic ligand/MOM mixture would be an interesting material for application in commercial liquid crystal devices.
  • With reference to Table 1, the nematic stability of L5Pd-acac was approximately 15 °C (+23.8 °C/39.1 °C), and the chiral nematic stability of L*6Pd-acac was approximately 30 °C (+33.8 °C/63.6 °C). Such a difference between the transition temperatures and mesophase stabilities of the two MOMs arises from their different terminal groups and the larger R’ flexibility of L*6Pd-acac than that of L5Pd-acac (see Figure 1).
  • According to Figure 3, the tertiary phase diagram of the eutectic HL2/L2Pd-acac and L5Pd-acac mixtures exhibited a complete mesogenic miscibility due to the linear trend of their TIN transitions. However, the TNC transitions of the HL2/L2Pd-acac/L5Pd-acac phase diagram did not exhibit a eutectic point but rather showed a large nematic stability of 70–81 °C range within 0–50 % L5Pd-acac concentrations. At this composition range, such a ligand/MOM/MOM model system will also be interesting for further evaluation for application in commercial nematic liquid crystal materials.
  • With reference to Figure 4, the tertiary phase diagram of the eutectic HL2/L2Pd-acac and L6*Pd-acac mixtures also exhibited a complete mesogenic miscibility due to the linear trend of their TIN* transitions. Also, the HL2/L2Pd-acac/L*6Pd-acac phase diagram did not exhibit a eutectic point but showed a large chiral nematic stability range of 79–81 °C within 0–20% L6*Pd-acac concentration range. At this composition range, such a ligand/MOM/MOM model system could also be considered as chiral nematic materials for application in commercial liquid crystal devices.
  • It should be pointed out that the difference between the phase transitions in the two tertiary ligand/MOM/MOM mixtures were due to differences in the terminal groups and crystalline structures in the L5Pd-acac and L*6Pd-acac structures. Regardless of the lack of eutectic behavior in such ligand/MOM/MOM model mixtures, their wide and accessible mesogenic stabilities will justify such model materials for application upon future investigations on structural properties of metal complexation in MOMs.
  • Subsequently, we also studied the phase diagrams of the tertiary mixtures of eutectic HL2/L2Pd-acac with low-temperature E43 and high-temperature TN10427 commercial nematic materials. In Table 1, we also tabulated the transition temperature and nematic stabilities of the commercial E43 and TN10427 nematic mixtures.
According to Figure 5, the nematic stability in the tertiary eutectic HL2/L2Pd-acac/E43 mixtures was within 81 °C (−35 °C/+45.9 °C) and 101 °C (−30 °C/77.8 °C) temperature range, which is sufficiently wide for utilization of various compositions in their phase diagram. As both HL2/L2Pd-acac and E43 are eutectic, the linear trends of their TIN and TNC transition temperatures within the total compositions of the phase diagram indicated total nematic miscibility of the components.
With reference to Figure 6, the phase diagram of tertiary eutectic HL2/L2Pd-acac/TN10427, we also observed the total nematic miscibility of the components within the whole compositions of the phase diagram. This is also confirmed by the linear trends of the TIN and TNC transition temperatures of this mixture. The phase behavior in the phase diagram of HL2/L2Pd-acac/TN10427 showed higher accessible mesogenic stability than that in the HL2/L2Pd-acac/E43 mixture, which indicated the interesting potential utilization of such a system in high-temperature liquid crystal devices.

5. Conclusions

In conclusion, the results of this preliminary study demonstrated that low-temperature MOMs and their mixtures could be considered as potential guest materials in commercial liquid crystal hosts for electro-optical and optical device applications. The studied HL2 ligand and L2Pd-acac, L5Pd-acac and L6*Pd-acac MOMs exhibit low-temperature mesophase transition temperatures below 70 °C.
It should be mentioned that this preliminary study intended to present potential applications of low-temperature model MOM structures and mixtures based only on their transition temperatures and phase diagram studies. However, their eventual consideration for use in commercial liquid crystal devices will require future systematic investigations through molecular engineering, synthesis, mixing, characterization, evaluation and qualification of appropriate MOM structures having chemical stabilities, accessible transition temperatures, wide mesogenic ranges and thermodynamic miscibility with commercial materials, as well as exploitation of other MOMs chemical, physical and electro-optical properties that are not present in the organic liquid crystals.
Finally, it is worth noting that, although the author is aware of the incompleteness of this work, his intention is to provide a roadmap to pave the way and encourage the interested readers for further applied research on low-temperature MOMs for application on liquid crystal materials and devices.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors would like to thank the Electro-Optical Film Group of Snia Riceche, Snia BPD (Fiat Group), Via Pomarico, Pisticci Scalo (MT), Italy, who sponsored and financed the research and development projects on metallomesogens under collaboration contract with M. Ghedini’s group of the University of Calabria, Rende (CA), Italy, during 1993–1996 period.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Friedel, G. Les Éats Mésomorphes de la Matière. Ann. Phys. 1922, 9, 273–474. [Google Scholar] [CrossRef]
  2. Serrano, J.L. Metallomesogens: Synthesis, Properties and Applications; Wiley VCH: New York, NY, USA, 1996. [Google Scholar]
  3. Donnio, B.; Bruce, D.W. Liquid Crystals II Metallomesogens; Mingos, D.M.P., Ed.; Springer: Berlin/Heidelberg, Germany, 1999; Volume 95. [Google Scholar]
  4. Donnio, B.; Guillon, D.; Deschenaux, R.; Bruce, D.W. Comprehensive Coordination Chemistry II; McCleverty, J.A., Meyer, T.J., Eds.; Elsevier: Oxford, UK, 2003; Volume 6. [Google Scholar]
  5. Date, R.W.; Iglesias, E.F.; Rowe, K.E.; Elliott, J.M.; Bruce, D.W. Metallomesogens by ligand design. Dalton Trans. 2003, 10, 1914–1931. [Google Scholar] [CrossRef]
  6. Bruce, D.W.; Deschenaux, R.; Donnio, B.; Guillon, D. Comprehensive Organometallic Chemistry III; Crabtree, R.H., Mingos, D.M.P., Eds.; Elsevier: Oxford, UK, 2006; p. 195. [Google Scholar]
  7. Bruce, D.W. Cyanobiphenyls and metallomesogens—Where it started and where it went. Liq. Cryst. 2024, 51, 1311–1321. [Google Scholar] [CrossRef]
  8. Porta, B.; Khamsi, J.; Noveron, J.C. Metallomesogens: Supramolecular design via alkane-rich metal complexes. Curr. Org. Chem. 2008, 12, 1298–1321. [Google Scholar] [CrossRef]
  9. Paez, E.B.A.; Curcio, S.; Neme, N.P.; Matos MJ, S.; Correa, R.S.; Pereira, F.J.; Hilário, F.F.; Cazati, T.; Taylor, J.G. Synthesis, photophysical and electrochemical properties of novel and highly fluorescent difluoroboron flavanone β-diketonate complexes. N. J. Chem. 2020, 44, 14615–14631. [Google Scholar] [CrossRef]
  10. Wang, Y.; Shi, J.; Chen, J.; Zhu, W.; Baranoff, E. Recent progress in luminescent liquid crystal materials: Design, properties and application for linearly polarised emission. J. Mater. Chem. C 2015, 3, 7993–8005. [Google Scholar]
  11. Wang, Y.; Fan, J.; Shi, J.; Qi, H.; Baranoff, E.; Xie, G.; Li, Q.; Tan, H.; Liu, Y.; Zhu, W. Influence of integrated alkyl-chain length on the mesogenic and photophysical properties of platinum-based metallomesogens and their application for polarized white OLEDs. Dye. Pigment. 2016, 133, 238–247. [Google Scholar] [CrossRef]
  12. Krikorian, M.; Liu, S.; Swager, T.M. Columnar liquid crystallinity and mechanochromism in cationic platinum (II) complexes. J. Am. Chem. Soc. 2014, 136, 2952–2955. [Google Scholar] [CrossRef]
  13. Cuerva, C.; Cano, M.; Lodeiro, C. Advanced functional luminescent metallomesogens: The key role of the metal center. Chem. Rev. 2021, 121, 12966–13010. [Google Scholar] [CrossRef]
  14. Geng, H.; Luo, K.; Cheng, H.; Zhang, S.; Ni, H.; Wang, H.; Yu, W.; Li, Q. Novel columnar metallomesogens based on cationic platinum(ii) complexes without long peripheral chains. RSC Adv. 2017, 7, 11389–11393. [Google Scholar] [CrossRef]
  15. Cuerva de Alaíz, C. Luminescent Pt(II) metallomesogens in hollow nanoparticles for applications in biomedicine. Ph.D. Thesis, University of Madrid, Madrid, Spain, 2018. [Google Scholar]
  16. Diana, R.; Panunzi, B.; Tuzi, A.; Piotto, S.; Concilio, S.; Caruso, U. An amphiphilic pyridinoyl-hydrazone probe for colorimetric and fluorescence pH sensing. Molecules 2019, 24, 3833. [Google Scholar] [CrossRef] [PubMed]
  17. Zhang, W.; Yu, C.; Yang, M.; Wen, S.; Zhang, J. Characterization of a Hg2+-selective fluorescent probe based on rhodamine B and its imaging in living cells. Molecules 2021, 26, 3385. [Google Scholar] [CrossRef] [PubMed]
  18. Liu, S.-H.; Lin, M.-S.; Chen, L.-Y.; Hong, Y.-H.; Tsai, C.-H.; Wu, C.-C.; Poloek, A.; Chi, Y.; Chen, C.-A.; Chen, S.H.; et al. Polarized phosphorescent organic light-emitting devices adopting mesogenic host–guest systems. Org. Electron. 2011, 12, 15–21. [Google Scholar] [CrossRef]
  19. Yang, X.; Wu, X.; Zhou, D.; Yu, J.; Xie, G.; Bruce, D.W.; Wang, Y. Platinum-based metallomesogens bearing a Pt (4, 6-dfppy)(acac) skeleton: Synthesis, photophysical properties and polarised phosphorescence application. Dalton Trans. 2018, 47, 13368–13377. [Google Scholar] [CrossRef]
  20. Marcos, M.; Romero, P.; Serrano, J.-L. Nematic liquid crystal materials containing nickel(II) or copper(II) atoms. Two different kinds of magnetic behaviour. J. Chem. Soc. Chem. Commun. 1989, 21, 1641–1643. [Google Scholar] [CrossRef]
  21. Akiyoshi, R.; Zenno, H.; Sekine, Y.; Nakaya, M.; Akita, M.; Kosumi, D.; Lindoy, L.F.; Hayami, S.A. A ferroelectric metallomesogen exhibiting field induced slow magnetic relaxation. Chem. Eur. J. 2021, 28, 1–7. [Google Scholar] [CrossRef]
  22. Seredyuk, M.; Muñoz, M.C.; Ksenofontov, V.; Gütlich, P.; Galyametdinov, Y.; Real, J.A. Spin Crossover Star-Shaped Metallomesogens of Iron(II). J. Inorg. Chem. 2014, 53, 8442–8454. [Google Scholar] [CrossRef]
  23. Fitzpatrick, A.J.; Martinho, P.N.; Gildea, B.J.; Holbrey, J.D.; Morgan, G.G. Robust Room Temperature Hysteresis in an FeIII Spin Crossover Metallomesogen. Eur. J. Inorg. Chem. 2016, 2016, 2025–2029. [Google Scholar] [CrossRef]
  24. Ionescu, A.; Godbert, N.; Crispini, A.; Termine, R.; Golemme, A.; Ghedini, M. Photoconductive Nile red cyclopalladated metallomesogens. J. Mater. Chem. 2012, 22, 23617–23626. [Google Scholar] [CrossRef]
  25. Wang, T.J.; Chaung, C.K.; Li, W.J.; Chen, T.J.; Chen, B.Y. Electrically tunable liquid-crystal-core optical channel waveguide. J. Light. Technol. 2013, 31, 3570–3574. [Google Scholar] [CrossRef]
  26. Su, P.Y.S.; Tseng, J.C.W.; Lee, K.-M.; Wang, J.-C.; Lin, I.J.B. Tetranuclear silver (I) clusters showing high ionic conductivity in a bicontinuous cubic mesophase. Inorg. Chem. 2014, 53, 5902–5910. [Google Scholar] [CrossRef] [PubMed]
  27. Su, P.Y.S.; Hsu, S.J.; Tseng, J.C.W.; Hsu, H.-F.; Wang, W.-J.; Lin, I.J.B. Polynuclear Silver(I) Triazole Complexes: Ion Conduction and Nanowire Formation in the Mesophase. Eur. Chem. J. 2016, 22, 323–330. [Google Scholar] [CrossRef] [PubMed]
  28. Chen, H.; Wu, S.-T. Advanced liquid crystal displays with supreme image qualities. Liq. Cryst. Today 2019, 28, 4–11. [Google Scholar] [CrossRef]
  29. Ma, X.; Liu, L.; Wang, J.; Hao, Y.; Xu, X.; Shang, X. The Role of Hydrazine in Colorimetric Probes Based on Ferrocene Derivative. Helv. Chim. Acta 2022, 105, e202200037. [Google Scholar] [CrossRef]
  30. Huitorel, B.; Benito, Q.; Fargues, A.; Garcia, A.; Gacoin, T.; Boilot, J.-P.; Perruchas, S.; Camerel, F. Mechanochromic luminescence and liquid crystallinity of molecular copper clusters. Chem. Mater. 2016, 28, 8190–8200. [Google Scholar] [CrossRef]
  31. Geng, H.; Luo, K.; Zou, G.; Wang, H.; Ni, H.; Yu, W.; Li, Q.; Wang, Y. New phosphorescent platinum (II) complexes: Lamellar mesophase and mechanochromism. New J. Chem. 2016, 40, 10371–10377. [Google Scholar] [CrossRef]
  32. Cuerva, C.; Campo, J.A.; Cano, M.; Lodeiro, C. Multi-stimuli-responsive properties of aggregation-enhanced emission-active unsymmetrical PtII metallomesogens through self-assembly. Chem. Eur. J. 2019, 25, 12046–12051. [Google Scholar] [CrossRef]
  33. Ginord-Godquin, M.; Maitlis, P.M. Metallomesogens: Metal complexes in organized fluid phases. Angew. Chem. Int. Engl. 1991, 30, 375–402. [Google Scholar] [CrossRef]
  34. Bruce, D.W. Metal-Containing Liquid Crystals in Inorganic Materials, 1st ed.; Bruce, D.W., O’Hare, D., Eds.; Wiley & Sons Ltd.: Hoboken, NJ, USA, 1997. [Google Scholar]
  35. Ros, M.B. Metallomesogens—Synthesis, Properties & Applications; Serrano, J.L., Ed.; VCH: Weinheim, Germany; New York, NY, USA; Basel, Switzerland; Cambridge, UK; Tokyo, Japan, 1996; Chapter 11. [Google Scholar]
  36. Binnemans, K. Metal-Containing Liquid Crystals in Inorganic Materials, 2nd ed.; Bruce, D.W., O’Hare, D., Waton, R.I., Eds.; Wiley: Hoboken, NJ, USA, 2010; pp. 61–133. [Google Scholar]
  37. Gimenez, R.; Lydon, D.P.; Serrano, J.L. Metallomesogens: A promise or a fact? Curr. Opin. Solid State Mater. Sci. 2002, 6, 527–535. [Google Scholar] [CrossRef]
  38. Liao, C.-T.; Wang, Y.-J.; Huang, C.-S.; Sheu, H.-S.; Lee, G.-H.; Lai, C.K. New metallomesogens derived from unsymmetric 1, 3, 4-thiodiazoles: Synthesis, single crystal structure, mesomorphism, and optical properties. Tetrahedron 2007, 63, 12437–12445. [Google Scholar] [CrossRef]
  39. Kim, D.-Y.; Kang, D.-G.; Lee, M.-H.; Kim, J.-S.; Lee, C.-R.; Jeong, K.-U. A photo-responsive metallomesogen for an optically and electrically tunable polarized light modulator. Chem. Commun. 2016, 52, 12821–12824. [Google Scholar] [CrossRef] [PubMed]
  40. Gao, H.; Yu, R.; Ma, Z.; Gong, Y.; Zhao, B.; Lv, Q.; Tan, Z.A. Recent advances of organometallic complexes in emerging photovoltaics. J. Polym. Sci. 2021, 60, 865–916. [Google Scholar] [CrossRef]
  41. Roviello, A.; Sirigu, A.; Hakemi, H.; Panunzi, B.; Ghedini, M. 19th International Liquid Crystal Conference 2002 Edinburgh, UK 30 June–5 July 2002. Mol. Cryst. Liq. Cryst. 2004, 409, 7. [Google Scholar] [CrossRef]
  42. Hakemi, H. Eutectic Metallomesogens based on Alkyl/Alkoxy Azobenzene Pd-Complexes as Potential Materials for Guest-Host Electro-Optical Devices. J. Mater. Polym. Sci. 2022, 2, 1–6. [Google Scholar]
  43. Hakemi, H. Phase Behavior of Low-Temperature Metallomesogen and Commercial Liquid Crystal Mixtures. Mater. Sci. 2024, 6, 30. [Google Scholar]
  44. Hakemi, H. On Potential Application of Metallomesogen Materials in Liquid Crystal Displays. J. Nanotechnol. Adv. Mater. 2023, 6, 1–5. [Google Scholar]
  45. Hakemi, H. Metallomesogens as potential materials for improvement of electro-optical properties of commercial liquid crystals. Mat. Sci. Eng. Int. J. 2023, 7, 108–111. [Google Scholar]
  46. Ghedini, M.; Pucci, D.; Neve, F. Mesogenic cyclopentadienyl cyclopalladated azobenzene complexes. Chemical Communications. Chem. Commun. 1996, 137–138. [Google Scholar] [CrossRef]
  47. Ghedini, M.; Pucci, D.; Viñuales, A. Cyclopalladated azo-and azoxybenzene mononuclear complexes. Mol. Cryst. Liq. Cryst. 2007, 465, 59–70. [Google Scholar] [CrossRef]
Physchem 04 00031 g001
Figure 1. General chemical formulas of L2 ligands and three LPd-acac MOMs.
Figure 1. General chemical formulas of L2 ligands and three LPd-acac MOMs.
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Figure 2. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac mixtures.
Figure 2. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac mixtures.
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Figure 3. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and L5Pd-acac mixtures.
Figure 3. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and L5Pd-acac mixtures.
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Figure 4. The isotropic-chiral nematic (orange) and chiral nematic-crystal (blue) phase transitions of L2/L2Pd-acac and L6*Pd-acac mixtures.
Figure 4. The isotropic-chiral nematic (orange) and chiral nematic-crystal (blue) phase transitions of L2/L2Pd-acac and L6*Pd-acac mixtures.
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Figure 5. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and E43 mixtures.
Figure 5. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and E43 mixtures.
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Figure 6. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and TN10427 mixtures.
Figure 6. The isotropic-nematic (orange) and nematic-crystal (blue) phase transitions of L2/L2Pd-acac and TN10427 mixtures.
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Table 1. The transition temperatures of ligand, MOMs materials.
Table 1. The transition temperatures of ligand, MOMs materials.
CompoundTransition Temperature (°C)Mesophase
HeatingCooling
TcmTmiTimTmc
HL241.751.148.114.8Enantiotropic Nematic
L2Pd-acac66.2-43.1−12Monotropic Nematic
L5Pd-acac69.1-39.123.8Monotropic Nematic
L6*Pd-acac52.268.663.633.8Enantiotropic Chiral Nematic
E43n.a.7877.8−30Enantiotropic Nematic
TN10427n.a.114.5114−40Enantiotropic Nematic
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Hakemi, H. Low-Temperature Metallomesogen Model Structures and Mixtures as Potential Materials for Application in Commercial Liquid Crystal Devices. Physchem 2024, 4, 447-457. https://doi.org/10.3390/physchem4040031

AMA Style

Hakemi H. Low-Temperature Metallomesogen Model Structures and Mixtures as Potential Materials for Application in Commercial Liquid Crystal Devices. Physchem. 2024; 4(4):447-457. https://doi.org/10.3390/physchem4040031

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Hakemi, Hassanali. 2024. "Low-Temperature Metallomesogen Model Structures and Mixtures as Potential Materials for Application in Commercial Liquid Crystal Devices" Physchem 4, no. 4: 447-457. https://doi.org/10.3390/physchem4040031

APA Style

Hakemi, H. (2024). Low-Temperature Metallomesogen Model Structures and Mixtures as Potential Materials for Application in Commercial Liquid Crystal Devices. Physchem, 4(4), 447-457. https://doi.org/10.3390/physchem4040031

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