Substituents In Benzene Ring Research Articles

Kinetics of uptake, translocation, and metabolism of organophosphate esters in japonica rice (Oryza sativa L.): Hydroponic experiment combined with model

Hydroponics combined with fugacity model was employed to investigate the kinetics of uptake, accumulation, and metabolism of organophosphate esters (OPEs) by japonica rice. The time-dependent process for uptake and accumulation of 5 OPEs and their diester-metabolites in both rice root and shoot fitted well with the pseudo-first-order kinetic model. The peak OPE accumulations in rice root and shoot were significantly positively or negatively correlated with their octanol-water partition coefficient (logKow) respectively, but not for their apparent accumulation rates. Root concentration factors (RCFs) and root-to-shoot translocation factors (TFs) of OPEs were found to be positively and negatively correlated with their logKow, respectively. Triphenyl phosphate with benzene ring substituents showed the highest RCF, but the lowest TF, because of its high potential for root adsorption due to the π electron-rich structures. Sterilized root exudates can hinder the root adsorption and absorption of OPEs from solution probably through competitive adsorption of OPEs with root surface. The first-hand transport and metabolism rates were also obtained by generating these rates to fit the dynamic fugacity model with the measurement values. The simulation indicated that the kinetics of OPE accumulation in rice plants may be controlled by multiple processes and physicochemical properties besides Kow.

Novel Tetracyclic Azaphenothiazines with the Quinoline Ring as New Anticancer and Antibacterial Derivatives of Chlorpromazine.

Phenothiazine derivatives are widely studied in various fields such as biology, chemistry, and medicine research because of their pharmaceutical effects. The first compound used successfully in the treatment of psychosis was a phenthiazine derivative, chlorpromazine. Apart from its activity in neurons, chlorpromazine has also been reported to display anticancer and antibacterial properties. In this study, we present the synthesis and research on the activity of A549, MDA, MiaPaCa, PC3, and HCT116 cancer cell lines and of S. aureus, S. epidermidis, E. coli, and P. aeruginosa bacterial strains against a series of new tetracyclic chlorpromazine analogues containing a quinoline scaffold in their structure instead of the benzene ring and various substituents at the thiazine nitrogen. The structure of these novel molecules has been determined by 1H NMR, 13C NMR, and HRMS spectral techniques. The seven most active of the twenty-four new chlorpromazine analogues tested were selected to study the mechanism of cytotoxic action. Their ability to induce apoptosis or necrosis in cancer cells was assessed by flow cytometry analysis. The results obtained confirmed the proapoptotic activity of selected compounds, especially in terms of inducing late apoptosis or necrosis in cancer cell lines A549, MiaPaCa-2, and HCT-116. Furthermore, studies on the induction of cell cycle arrest suggest that the new chlorpromazine analogues exert antiproliferative effects by inducing cell cycle arrest in the S phase and, consequently, apoptosis.

Persulfate catalyst synthesized with waterworks sludge for degrading Safranine T in the presence of boron

ABSTRACT Energy conservation and emission reduction are the general trend of the present world. In this study, a catalyst of 3WSH based on the waste recycle of waterworks sludge (WS) and Chinese herbs was prepared using one-step calcination treatment and then characterized by SEM, XRD, XPS, FTIR and BET. The catalytic performance of 3WSHB for activating potassium persulfate (PDS) was evaluated through the degradation of Safranine T (ST) in the presence of boron powder (B). The effects of vital parameters on ST removal were systematically studied, including PDS concentration, 3WSHB dosage, initial solution pH, B dosage, temperature and coexisting cations. The highest efficiency of ST removal was up to 93.0% under the optimal condition with 1.85 mM of PDS, 0.3 g/L of 3WSHB, 0.35g/L of B, 7 of pH. EPR and free radical quenching experiments demonstrated that •OH was the dominant reactive oxygen species for ST degradation in the PDS/3WSHB/B system. Moreover, the intermediates determined by HPLC-MS indicated that the oxidization of benzene ring substituents in ST and a hydrogen abstraction by electron transfer might occur during ST degradation. The dissatisfied reuse performance of 3WSHB might be attributed to its low Fe content and simple reusing way. The results demonstrate the effectiveness of WS recycling and reuse in the field of pollutant remediation.

Fluorescence of p-hydroxyazobenzocrowns – Tautomeric equilibrium effect

The spectroscopic properties of a series of para-hydroxyazobenzocrowns, including three novel compounds, were investigated using UV–Vis absorption and emission spectroscopy. This study presents, for the first time, determined quantum yield (QY) values for macrocycles of this category, ranging between 0.122 and 0.195. The highest values were obtained for crowns bearing two phenyl substituents in benzene rings. The impact of aromatic ring substituents and macroring size on the spectral characterization (1H NMR and FTIR) of p-hydroxyazobenzocrowns was examined in consideration of the azophenol ⇄ quinone-hydrazone tautomeric equilibrium. Dipole moments of p-hydroxyazobenzocrowns in the ground and excited states have been determined. The alignment between experimental findings and theoretical studies was established.

Activation of xanthine oxidase by 1,4-naphthoquinones: A novel potential research topic for diet management and risk assessment.

Oral intake of 1,4-naphthoquinones could be a potential risk factor for hyperuricemia and gout via activation of xanthine oxidase (XO). Herein, 1,4-naphthoquinones derived from food and food-borne pollutants were selected to investigate the structure and activity relationship (SAR) and the relative mechanism for activating XO in liver S9 fractions from humans (HLS9) and rats (RLS9). The SAR analysis showed that introduction of electron-donating substituents on the benzene ring or electron-withdrawing substituents on the quinone ring improved the XO-activating effect of 1,4-naphthoquinones. Different activation potential and kinetics behaviors were observed for activating XO by 1,4-naphthoquinones in HLS9/RLS9. Molecular docking simulation and density functional theory calculations showed a good correlation between -LogEC50 and docking free energy or HOMO-LUMO energy gap. The risk of exposure to the 1,4-naphthoquinones was evaluated and discussed. Our findings are helpful to guide diet management in clinic and avoid adverse events attributable to exposure to food-derived 1,4-naphthoquinones.

Do Phenyl Substituents Affect the Properties of Azobenzocrown Derivatives?

New products of photo- and thermal rearrangements of 19-membered azoxybenzocrown with phenyl substituents in benzene rings in the para positions to oligooxyethylene fragments are characterized. The yields of photochemical transformations depend on the solvent. Para-hydroxyazocrown is formed with yields over 50% in propan-2-ol. Ortho-hydroxyazobenzocrown is obtained with yields up to 70% in toluene/acetic acid mixture. Macrocyclic Ph-20-ester is obtained in yield 90% under thermochemical rearrangement conditions. Structure of new hydroxyazobenzocrowns and also atypical product of rearrangements, 20-membered ester, was confirmed by X-ray diffraction analysis. Azophenol⇄quinone-hydrazone tautomeric equilibrium of new hydroxyazobenzocrowns and the influence of metal cations on tautomeric equilibrium was investigated using 1H NMR and UV-Vis spectroscopy in acetonitrile. The highest value of stability constant (logK 7.25) was obtained for strontium complex of p-hydroxyazobenzocrown. For the first time p-hydroxyazobenzocrown was used as a chromoionophore in the receptor layer of an optical sensor. Comparative analysis with data obtained previously for series 19-membered analogs have shown the influence of the presence of substituents in benzene rings for the course and products distribution of photo- and thermal rearrangement. The effect of substituents was also discussed against the tautomeric equilibrium and metal cation complexation properties.

EVALUATION OF ANTIBACTERIAL ACTIVITY 5-AMINO-3-METHYLISOXAZOLE-4-CARBOHYDRAZIDE AND 5-AMINOISOXAZOLE[5,4-d]PYRIMIDIN-4-ONE DERIVATIVES

Searching for new compounds with specific biological activity in relation to various bacterial strains due to the increasing number of bacterial infections and the frequently developing antimicrobial resistance (AMR) is a significant problem in healthcare. Based on previous promising research related to the activity of isoxazole-4-carbohydrazide derivatives, we currently examined different substituted isoxazole-4-carbohydrazide derivatives in vitro against a panel of bacterial strains. In this work we evaluated antibacterial activity of 30 derivatives, previously described as mildly antimycobacterial, in 10 bacterial strains (5 Gram-negative (G-) and Gram-postive (G+) bacterias). Based on minimum inhibitory concentration (MIC), the mainly MIC50 and MIC90 values, the tested derivatives generally have shown rather weak and mild antibacterial activity. The most active compounds were 3d and 4d, both with methyl substituent in benzene ring. More detailed examination should be continued but this research increased the library of isoxazole derivatives with broad biological activity.

Complexation mechanism of crown ethers with rubidium and cesium ions using density functional theory

The complexation mechanism of crown ether derivatives (18C6, 21C7, B18C6, B21C7) with metal ions (Li+, K+, Rb+, Cs+) has been studied. Structural optimization was performed at the level of M06-2X/def2SVP. The results show that M+ mainly interacts with oxygen atoms, and CO bonds become longer after complexation. The interactions belong to the electrostatic attractive effect. The electrophilic substitution activity of crown ethers can be improved by benzene ring substituents, while the electrophilic complexing reaction activity decreases. 21C7 has the lowest electrostatic potential minimum, which is −96.0 kcal·mol−1. The complex 21C7-Cs+ and 21C7-Rb+ are more stable than other 21C7 complexes. The binding energy and Gibbs free energy of 21C7-Cs+ are −66.6 and −66.0 kcal·mol−1, respectively. The results can provide theoretical guidance for the design of crown ethers using for the extraction of Rb+ and Cs+ from brines.

Synthesis of Novel Benzenesulfonamide-Bearing Functionalized Imidazole Derivatives as Novel Candidates Targeting Multidrug-Resistant Mycobacterium abscessus Complex.

Infections caused by drug-resistant (DR) Mycobacterium abscessus (M. abscessus) complex (MAC) are an important public health concern, particularly when affecting individuals with various immunodeficiencies or chronic pulmonary diseases. Rapidly growing antimicrobial resistance among MAC urges us to develop novel antimicrobial candidates for future optimization. Therefore, we have designed and synthesized benzenesulfonamide-bearing functionalized imidazole or S-alkylated derivatives and evaluated their antimicrobial activity using multidrug-resistant M. abscessus strains and compared their antimycobacterial activity using M. bovis BCG and M. tuberculosis H37Ra. Benzenesulfonamide-bearing imidazole-2-thiol compound 13, containing 4-CF3 substituent in benzene ring, showed strong antimicrobial activity against the tested mycobacterial strains and was more active than some antibiotics used as a reference. Furthermore, an imidazole-bearing 4-F substituent and S-methyl group demonstrated good antimicrobial activity against M. abscessus complex strains, as well as M. bovis BCG and M. tuberculosis H37Ra. In summary, these results demonstrated that novel benzenesulfonamide derivatives, bearing substituted imidazoles, could be further explored as potential candidates for the further hit-to-lead optimization of novel antimycobacterial compounds.

N-(2-Arylethyl)-2-methylprop-2-enamides as Versatile Reagents for Synthesis of Molecularly Imprinted Polymers.

The paper describes the formation of six aromatic N-(2-arylethyl)-2-methylprop-2-enamides with various substituents in benzene ring, viz., 4-F, 4-Cl, 2,4-Cl2, 4-Br, 4-OMe, and 3,4-(OMe)2 from 2-arylethylamines and methacryloyl chloride in ethylene dichloride with high yields (46–94%). The structure of the compounds was confirmed by 1H NMR, 13C NMR, IR, and HR-MS. Those compounds were obtained to serve as functionalized templates for the fabrication of molecularly imprinted polymers followed by the hydrolysis of an amide linkage. In an exemplary experiment, the imprinted polymer was produced from N-(2-(4-bromophenyl)ethyl)-2-methylprop-2-enamide and divinylbenzene, acting as cross-linker. The hydrolysis of 2-(4-bromophenyl)ethyl residue proceeded and the characterization of material including SEM, EDS, 13C CP MAS NMR, and BET on various steps of preparation was carried out. The adsorption studies proved that there was a high affinity towards the target biomolecules tyramine and L-norepinephrine, with imprinting factors equal to 2.47 and 2.50, respectively, when compared to non-imprinted polymer synthesized from methacrylic acid and divinylbenzene only.

Synthesis, antimicrobial activity and 3D-QSAR study of novel 5-substituted-1,3,4-thiadiazole Schiff base derivatives

In this study, 21 new thiadiazole Schiff base derivatives were synthesized based on the reactive group splicing principle, and the structures of the target compounds were confirmed and characterized by 1H NMR, FT-IR and HRMS. The inhibition activity of the compounds was tested in vitro against Escherichia coli, Staphylococcus aureus, Aspergillus niger, Rhizopus, Penicillium, Botrytis cinerea and Alternaria using mycelial growth rate method. The results showed that most of the compounds exhibited good biological activity at a dose of 50 µg/mL. Among them, compounds 2b, 2r, and 2a exhibited inhibition rates against the tested microbe comparable to that of the control drug Chlorothalonil. A preliminary three-dimensional quantitative conformational relationship (3D-QSAR) study of the inhibitory activity of the target compounds against Aspergillus niger was carried out using CoMFA and CoMSIA, and the model results showed that increasing the volume of the 2- and 6-positions of benzene ring A and the 3-position substituent of benzene ring B, decreasing the volume of the 5-position substituent benzene ring A; increasing hydrophobic groups at the 6-position of benzene ring A and the 2′-position of benzene ring B; increasing the 3′-position hydrogen bond donor group and decreasing the 3′-position hydrogen bond acceptor group of benzene ring B can improve the biological activity of the compounds. The inhibitory activity of the compounds can be improved.

Products of Photo- and Thermochemical Rearrangement of 19-Membered di-tert-Butyl-Azoxybenzocrown.

The preparation and characterization of products of the photochemical and thermochemical rearrangements of 19-membered azoxybenzocrowns with two, bulky, tert-butyl substituents in benzene rings in the para positions to oligooxyethylene fragments (meta positions to azoxy group, i.e., t-Bu-19-Azo-O have been presented. In photochemical rearrangement, two colored typical products were expected, i.e., 19-membered o-hydroxy-m,m′-di-tert-butyl-azobenzocrown (t-Bu-19-o-OH) and 19-membered p-hydroxy-m,m′-di-tert-butyl-azobenzocrown (t-Bu-19-p-OH). In experiments, two colored atypical macrocyclic derivatives, one 6-membered and one 5-membered ring, bearing an aldehyde group (t-Bu-19-al) or intramolecular ester group (t-Bu-20-ester), were obtained. Photochemical rearrangement led to one more macrocyclic product being isolated and identified: a 17-membered colorless compound, without an azo moiety, t-Bu-17-p-OH. The yield of the individual compounds was significantly influenced by the reaction conditions. Thermochemical rearrangement led to t-Bu-20-ester as the main product. The structures of the four crystalline products of the rearrangement—t-Bu-19-o-OH, t-Bu-19-p-OH, t-Bu-20-ester and t-Bu-17-p-OH—were determined by the X-ray method. Structures in solution of atypical derivatives (t-Bu-19-al and t-Bu-20-ester) and t-Bu-19-p-OH were defined using NMR spectroscopy. For the newly obtained hydroxyazobenzocrowns, the azo–phenol⇄quinone–hydrazone tautomeric equilibrium was investigated using spectroscopic methods. Complexation studies of alkali and alkaline earth metal cations were studied using UV-Vis absorption spectroscopy. 1H NMR spectroscopy was additionally used to study the cation recognition of metal cations. Cation binding studies in acetonitrile have shown high selectivity towards calcium over magnesium for t-Bu-19-o-OH.

Benzaldehyde Attenuates the Fifth Stage Larval Excretory-Secretory Product of Angiostrongylus cantonensis-Induced Injury in Mouse Astrocytes via Regulation of Endoplasmic Reticulum Stress and Oxidative Stress.

Excretory–secretory products (ESPs) are the main research targets for investigating the hosts and helminths interaction. Parasitic worms can migrate to parasitic sites and avoid the host immune response by secreting this product. Angiostrongylus cantonensis is an important food-borne zoonotic parasite that causes severe neuropathological damage and symptoms, including eosinophilic meningitis or meningoencephalitis in humans. Benzaldehydes are organic compounds composed of a benzene ring and formyl substituents. This compound has anti-inflammatory and antioxidation properties. Previous studies showed that 3-hydroxybenzaldehyde (3-HBA) and 4-hydroxybenzaldehyde (4-HBA) can reduce apoptosis in A. cantonensis ESP-treated astrocytes. These results on the protective effect underlying benzaldehyde have primarily focused on cell survival. The study was designed to investigate the molecular mechanisms of endoplasmic reticulum stress (ER stress) and oxidative stress in astrocytes in A. cantonensis ESP-treated astrocytes and to evaluate the therapeutic consequent of 3-HBA and 4-HBA. First, we initially established the RNA-seq dataset in each group, including normal, ESPs, ESPs + 3-HBA, and ESPs + 4-HBA. We also found that benzaldehyde (3-HBA and 4-HBA) can stimulate astrocytes to express ER stress-related molecules after ESP treatment. The level of oxidative stress could also be decreased in astrocytes by elevating antioxidant activity and reducing ROS generation. These results suggested that benzaldehyde may be a potential therapeutic compound for human angiostrongyliasis to support brain cell survival by inducing the expression levels of ER stress- and oxidative stress-related pathways.

Research progresses in the biosynthesis of curcuminoids

Curcuminoids are rare diketone compounds in plants and can be found in the rhizome of Curcuma longa as well as other Zingiberaceae and Araceae. Curcuminoids have been widely used in food and medical area owing to the yellow colors, as well as the antioxidant and many other pharmacological activities. Curcuminoids are a mixture of compounds containing curcumin, demethoxycurcumin and bisdemethoxycurcumin, which have distinct benzene ring substituents. Currently, curcuminoids are exclusively produced through plant extraction, which do not satisfy the meeting of the market demand. Empowered with new synthetic biology tools and metabolic engineering strategies, there is renewed interest in production of curcuminoids using microorganisms. Heterologous production of curcuminoids has been achieved using Escherichia coli, Yarrowia lipolytica, Pseudomonas putida and Aspergillus oryzae via engineering of curcuminoids biosynthesis pathway. In this review, we first describe the biological activities and various applications of curcuminoids. Next, we summarize the biosynthetic pathway of curcuminoids in Curcuma longa and discuss the catalytic mechanisms of curcumin synthases. Then, we thoroughly explore recent advances in the use of distinct microorganisms for the production of curcuminoids with a special focus on metabolic engineering strategies. Finally, we prospect the microbial production of curcuminoids by highlighting some promising techniques and approaches.

Influence of the ligand structure on the properties of bidentate salicylaldimine nickel(II) complexes in ethylene oligomerization

Three nickel(II) complexes (C1–C3) bearing diamine-bridged 4-hydroxysalicylaldehyde ligands (L1–L3) were successfully synthesized, and all the compounds were characterized by physicochemical and spectroscopic methods. The influence of the oligomerization parameters on the catalytic properties of complex C2 was systematically investigated. The results showed that oligomerization parameters played an important role in the catalytic properties and the catalytic activity was 19.90 × 104 g/(mol·Ni·h) and the selectivity of C8+ olefins was 60.25% when the precatalyst dosage was 5 μmol, the Al/Ni molar ratio was 500, the temperature was 25 °C, the reaction time was 30 min and the pressure of ethylene was 0.7 MPa. Complexes C1–C3 with different lengths of the bridged group were evaluated for ethylene oligomerization, and the results showed that the length of the alkyl chain in the ligand had little influence on the catalytic properties. Complex C4 based on ethanediamine-bridged salicylaldimine and C5 based on the hyperbranched salicylaldimine in our previous work were also investigated to study the influence of the ligand structure on the catalytic properties. The catalytic activity [31.80 × 104 g/(mol·Ni·h)] and the content of the low-carbon oligomers (70.16%) for complex C4 were higher than complex C2 with hydroxyl substituent in benzene ring. The catalytic activity and the content of the low carbon oligomers for complex C5 were far higher than other four complexes.

The effect of benzene ring substituent at different position of main ligand on electronic structure and photophysical properties of a series of iridium(III) complexes

The electronic structure and photophysical properties of a series of iridium(III) complexes have been theoretically explored by DFT/TDDFT calculations. Ionization potential, electron affinities, and reorganization energy have been calculated to evaluate the charge transfer and balance properties between hole and electron for the three complexes. The lowest lying absorption of 3 is obviously blue-shifted in contrast to those of 1 and 2, which is consistent with the variation of the energy gap between of LUMO and HOMO values. The calculated lowest energy emissions of complexes 1, 2 and 3 are located at 607, 634 and 698 nm, respectively.

Photoresponsive Behavior of Heterocyclic Azo Polymers with Various Functional Groups

Here, we report on efficiency of light-induced processes in a series of methacrylic polymers containing heterocyclic azo moieties covalently attached to the polymer backbone. The optical response of the polymers was investigated in experiments on photoinduced birefringence measurements and surface relief gratings inscription upon irradiation with polarized blue light. The experimental results indicate that the presence of acceptor-type (Br) substituent in the side benzene ring linked to the heterocyclic ring has a beneficial effect on efficiency of birefringence generation, while incorporation of donor-type (CH3, OCH3) substituents lowers the level of photoinduced birefringence. Moreover, the process of surface relief structure formation was successfully observed for all studied polymers. The obtained surface-modulation depth reached up to 100 nm for two out of four investigated materials. No straightforward relation between the induced azo chromophore alignment level and the efficiency of mass-transport process is observed.

Novel Thiazolidin-4-ones as Potential Non-nucleoside Inhibitors of HIV-1 Reverse Transcriptase.

Background: HIV is the causative agent of Acquired Immunodeficiency Syndrome (AIDS), an infectious disease with increasing incidence worldwide. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) play an important role in the treatment of AIDS. Although, many compounds are already being used as anti-HIV drugs, research for the development of new inhibitors continues as the virus develops resistant strains. Methods: The best features of available NNRTIs were taken into account for the design of novel inhibitors. PASS (Prediction of activity spectra for substances) prediction program and molecular docking studies for the selection of designed compounds were used for the synthesis. Compounds were synthesized using conventional and microwave irradiation methods and HIV RT inhibitory action was evaluated by colorimetric photometric immunoassay. Results: The evaluation of HIV-1 RT inhibitory activity revealed that seven compounds have significantly lower ΙC50 values than nevirapine (0.3 μΜ). It was observed that the activity of compounds depends not only on the nature of substituent and it position in benzothiazole ring but also on the nature and position of substituents in benzene ring. Conclusion: Twenty four of the tested compounds exhibited inhibitory action lower than 4 μΜ. Seven of them showed better activity than nevirapine, while three of the compounds exhibited IC50 values lower than 5 nM. Two compounds 9 and 10 exhibited very good inhibitory activity with IC50 1 nM.

Calculation of Lithium Isotope Effects in Extraction Systems with Benzo-15-crown-5 and Its Derivatives

With taking into account the β-factor value of the lithium ion aqua complex found earlier, the single stage extraction coefficient of isotope separation (α) of the 6Li–7Li pair has been calculated for the extraction system containing the benzo-15-crown-5–Li+ (H2O)Cl– complex in the organic phase, which corresponds to a real extraction process. Similar calculations have been carried out for other anions, as well as for various benzo-15-crown-5 derivatives with varying the number and type of donor atoms and different substituents in the benzene ring. Quantum-chemical calculations of the vibrational frequencies of the isotopic forms of the crown ether complex were performed using the Firefly program with the RHF/6-311++G** basis set. It has been shown that the isotope separation factor in this case is lower than in the case of the anhydrous benzo-15-crown-5–Li+Cl– complex and the model benzo-15-crown-5–Li+ (H2O) complex.

Effect of orientation of extra fused benzene ring and lateral methyl substituent on the mesophase behaviour of three-ring azo/ester molecules

ABSTRACTTwo homologous series of the three-ring azo/ester compounds 2-(or1-) naphthyl 4ʹ-(4ʹ’-alkoxy phenylazo) benzoates (Ina and IIna) were synthesised. A lateral methyl group was introduced in different positions of the alkoxy phenyl moiety, in position-2 to give series Inb and IInb and in position-3 to give series Inc and IInc. Molecular structures were characterised via elemental analyses, infrared and 1H-NMR. Their mesophase characteristics were investigated by differential scanning calorimetry (DSC) and their phases identified via polarised light microscopy (PLM). Transition temperatures were correlated with the alkoxy-chain length (n) that varies between 6, 8, 10, 12, 14, and 16 carbons. Comparative studies were first made to investigate the effect of including the extra fused benzene ring, and its orientation, into the previously investigated three-ring compounds, 4-phenyl 4ʹ-(4′′-alkoxyphenylazo) benzoates (IIIna). Investigation of the mesophase behaviour was extended to cover the effect of introducing the lateral methyl group and its position. The comparison between the present six series and their corresponding phenyl analogues IIIna,b,c, indicated that the 2-naphthyl analogues, Ina,b,c, exhibit the highest mesophase stability. Whereas, the steric effect of the protruded naphthalene group destabilises all mesophases and appear only monotropically. The results were discussed in terms of polarisability effect.