Aromatic Region Research Articles

Optical absorption and photoluminescence of partially fluorinated graphite crystallites

Fluorinated graphene-like materials are currently attracting much attention due to the tuning of their properties by changing the fluorine content and pattern on the graphene lattice. In this work, we report the redshift of absorption bands and the suppression (increase) of green (yellow-orange) photoluminescence (PL) in the spectra of transparent CFx crystallites as x decreases from ∼0.44 to ∼0.33. Time-dependent density functional theory (TDDFT) calculations reveal that the aromatic regions and polyene chains in the CFx layers are mainly responsible for the optical absorption of the samples in the ultraviolet and visible regions, respectively. The electron-hole recombination within branched aromatic rings or long carbon chains produces orange-red emission, while green-yellow PL is due to transitions of excited polyene electrons to half-occupied levels of aromatic carbon. Our results show that the optical properties of partially fluorinated graphite layers are determined by the size and shape of the remaining sp2 carbon regions, which can be varied by changing the fluorination conditions.

An exit beyond the pharmacophore model for 5-HT6R agents - a new strategy to gain dual 5-HT6/5-HT2A action for triazine derivatives with procognitive potential

This research allowed us to find the first highly potent 5-HT6/5-HT2A receptor (5-HT6/5-HT2AR) dual antagonists in a group of 1,3,5-triazine compounds as a result of an exit beyond the hydrophobic feature of the pharmacophore model for 5-HT6R antagonists. Design and synthesis of the series (2–16) of new O- and S-containing ether derivatives of 1,3,5-triazines with the double-ring aromatic region have been performed. The new compounds were examined within the comprehensive pharmacological screening, including: radioligand binding assays, functional and ADMET studies in vitro as well as behavioral tests in rats. Crystallographic aspects and computer-aided structure–activity relationship were analyzed, as well. The comprehensive approach led to selection of compound 12 (4-(4-methylpiperazin-1-yl)-6-(2-(naphthalen-2-ylthio)propan-2-yl)-1,3,5-triazin-2-amine) with the most significant dual 5-HT6/5-HT2AR antagonistic action (5-HT6R Ki = 11 nM, 5-HT2AR Ki = 39 nM). Moreover, the compound 12 has satisfactory ADMETox properties in vitro, i.e.: the high permeability through biological membranes, high metabolic stability, neither mutagenic nor hepatotoxic effects, and moderate ability to inhibit CYP3A4. Above all, 12 showed ability to reverse the pharmacologically-induced (MK-801) memory impairment at low doses (1–3 mg/kg) in Novel Object Recognition (NOR) test in rats. Our results indicate a promising potency of dual 5-HT6/5-HT2AR antagonism in the search for novel strategy to fight Alzheimer’s disease, which remains an unmet clinical need.

Simultaneous elevation of acid-insoluble lignin and syringyl lignin is the preliminary Cd detoxification strategy in a Cd pollution-safe cultivar (Cd-PSC) of Brassica parachinensis L.

Cadmium (Cd) immobilization in the cell wall is responsible for Cd detoxification in Cd-accumulating cultivars. Lignin is the dominant constituent of the secondary cell wall (SCW), but its role in Cd compartmentalization is poorly understood. The mechanism of Cd compartmentalization by lignin was thus investigated herein. Lignin content and composition, as well as related genes and proteins, were analyzed in the Cd pollution-safe cultivar Brassica parachinensis L. ‘SJ19’. The lignin microstructural regions and Cd affinities were characterized by 2D-heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) and density functional theory (DFT). Lignin combined with 14.2% of the total Cd in SJ19, with a higher Cd distribution in acid-insoluble lignin (AIL). Additionally, the proportion of AIL increased under Cd treatment. The increase in the proportion of the lignin aromatic region syringyl (S) and decrease in the guaiacyl (G) proportion were in accordance with the significant up-regulation of peroxidase P7 and down-regulation of caffeoyl-CoA O-methyltransferase At1g67980 under Cd stress. Moreover, the Cd affinity associating with the lignin aromatic region ranked as S > G> H (p-hydroxyphenyl). Therefore, rather than lignin biosynthesis, the simultaneous elevation of AIL and S lignin was recognized as the preliminary strategy for lignin compartmentalization of Cd in SCW for the first time herein. This is beneficial for Cd detoxification in the Cd pollution-safe cultivar of B. parachinensis.

Exploring Dissolved Organic Carbon Variations in a High Elevation Tropical Peatland Ecosystem: Cerro de la Muerte, Costa Rica

Tropical peatlands are distributed mainly in coastal lowlands; however high elevation regions exhibit a large prevalence of small and fragmented peatlands that are mostly understudied. Artificial drainage of peatlands to expand the area of cattle farming, horticulture, and urbanization is increasing carbon losses to the atmosphere and streams worldwide. Here, we present an exploratory characterization of dissolved carbon optical properties in ombrotrophic peat bogs of the Talamanca range of Costa Rica, across an altitudinal gradient (2,400–3,100 m a.s.l.) during the rainy season. Dissolved organic matter (DOM) sources and decomposition processes were evaluated in the light of dissolved organic and inorganic carbon (DOC and DIC), optical properties, and major water chemistry. DOC concentrations ranged from 0.2 up to 47.0 mg/L. DIC concentrations were below 2 mg/L and δ13CDIC values indicated a mixture between soil organic matter, CO2 in soil water, and to a lesser degree DIC derived from bacterial CO2. Absolute fluorescence intensity of humic-like peaks was 6–7 times greater than fresh-like peaks across all sites. Fluorescence peak ratios coupled with the biological and humification indexes point to a greater relative contribution of recalcitrant soil-derived DOM. Excitation/Emission matrices denoted a high prevalence of humic and fulvic acids in the peat bogs, with moderate intensities in soluble microbial by-products-like and aromatic protein regions at three sites. Our data provides a baseline to underpin tropical carbon dynamics across high elevation peatlands.

Molecular docking studies and evaluation of the antiretroviral activity and cytotoxicity of the species Lafoensia pacari Saint-Hilaire.

Interest in antiviral plant species has grown exponentially and some have been reported to have anti-HIV properties. This research aims to perform the bio-guided phytochemical fractionation by antiretroviral activity of Lafoensia pacari stem barks. This in vitro experimental study involved the preparation of plant material, obtention of ethanolic extract, fractionation, purification, identification and quantification of fractions, acid-base extraction, nuclear magnetic resonance, HIV-1 RT inhibition test and molecular docking studies. From the bio-guided fractionation by the antiretroviral activity there was a higher activity in the acetanolic subfractions, highlighting the acetate subfraction - neutrals with 60.98% of RT inhibition and ellagic acid with 88.61% of RT inhibition and absence of cytotoxicity. The macrophage lineage cytotoxicity assay showed that the chloroform fraction was more toxic than the acetate fraction. The analysis of the J-resolved spectrum in the aromatic region showed a singlet at 7.48 and 6.93 ppm which was identified as ellagic acid and gallic acid, respectively. The 5TIQ enzyme obtained better affinity parameter with the ellagic acid ligand, which was confirmed by the HSQC-1H-13C spectra. Gallic acid was also favorable to form interaction with the 5TIQ enzyme, being confirmed through the HSQC-1H-13C spectrum. From the PreADMET evaluation it was found that ellagic acid is a promising molecule for its RT inhibition activity and pharmacokinetic and toxicity parameters.

Phytotoxicity of plant extracts of Vismia japurensis cultivated in vivo and in vitro.

Plants that produce secondary metabolites with allelopathic activity or phytotoxicity can be biotechnologically important, serving as sources of allelochemicals, and thus contributing to the agroindustrial sector. Vismia japurensis (Hypericaceae) is an Amazonian species that grows in clumps called vismiais, from which most other plants are absent. Accordingly, the objective of this study was to identify possible phytotoxicity effects of hexane and methanol extracts of Vismia japurensis leaves and branches in vivo and from seedlings grown in vitro on Lactuca sativa. In addition, fresh and dry leaves were assayed by the sandwich method in order to determine their ability to release allelochemicals. The hexanic extract from in vitro seedlings reduced germination by 10%, while the methanol extract produced a 16% reduction in germination speed. Root growth of Lactuca sativa was inhibited by 64.7% when subjected to hexane leaf extract, by 39.3% under the influence of hexane branch extract, and by 96.09% for in vitro seedling hexanic extract. When analysed by thin layer chromatography and 1H nuclear magnetic resonance, extracts showed evidence of terpenes, anthraquinones and flavonoids, with greater intensity of signals in the aromatic region of in vitro seedling hexanic extract. Clearly, Vismia japurensis has a high biotechnological potential in terms of the production of substances of low polarity with capacity to interfere in plant development.

All are aromatic: A 3D globally aromatic cage containing five types of 2D aromatic macrocycles

All are aromatic: A 3D globally aromatic cage containing five types of 2D aromatic macrocycles

Site-selective and metal-free C\u2013H nitration of biologically relevant N-heterocycles

The site-selective and metal-free C–H nitration reaction of quinoxalinones and pyrazinones as biologically important N-heterocycles with t-butyl nitrite is described. A wide range of quinoxalinones were efficiently applied in this transformation, providing C7-nitrated quinoxalinones without undergoing C3-nitration. From the view of mechanistic point, the radical addition reaction exclusively occurred at the electron-rich aromatic region beyond electron-deficient N-heterocycle ring. This is a first report on the C7–H functionalization of quinoxalinones under metal-free conditions. In contrast, the nitration reaction readily takes place at the C3-position of pyrazinones. This transformation is characterized by the scale-up compatibility, mild reaction conditions, and excellent functional group tolerance. The applicability of the developed method is showcased by the selective reduction of NO2 functionality on the C7-nitrated quinoxalinone product, providing aniline derivatives. Combined mechanistic investigations aided the elucidation of a plausible reaction mechanism.

α-glucosidase inhibitors from Syzygium polyanthum (Wight) Walp leaves as revealed by metabolomics and in silico approaches

Ethnopharmacological relevanceSyzygium polyanthum (Wight) Walp leaves are traditionally used to cure diabetes in many regions of Indonesia. Traditional use involves boiling the leaves until the water is reduced to half volume, and then the decoction is taken 1–2 times daily. Despite several studies reporting the antidiabetic activity of this plant, bioactive compounds have not been well identified. Aim of the studyIndonesia is one of the countries with the highest diabetes cases, particularly type 2 diabetes mellitus (T2DM). Few people have access to modern medicinal treatment; thus, the role of antidiabetic traditional medicine has become increasingly important. This research aimed to identify α-glucosidase inhibitors from S. polyathum leaves using a metabolomics approach. When the active compounds of S. polyathum are properly identified, the quality of the herb can be more easily controlled. Materials and methodsThe dried leaves of S. polyanthum were extracted by a comprehensive extraction method using a solvent combination of n-hexane, acetone, and water in a gradient, resulting in a total of 42 fractions. All fractions were subjected to an in vitro α-glucosidase inhibition test and chemical profile analysis using Nuclear Magnetic Resonance (NMR) and high performance liquid chromatography (HPLC). Orthogonal projection least square (OPLS) analysis was used to correlate the two data to identify NMR signals, and HPLC chromatogram peaks correlated to the activity. 2D NMR and ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS) analyses were also used to give more precise compound identification. The activity of the identified active compounds was confirmed by an in silico technique. Results and discussionThe results of the α-glucosidase activity test showed that the most active fractions were obtained from solvents with medium polarity: Fractions 9 and 10 (F9 and F10), obtained from gradient acetone-water 4:1 and 3:2, respectively. The IC50 values of F9 and F10 were 24.8 and 31.8 μg/mL, respectively. NMR data showed that F9 had more intense and diverse signals in the aromatic region than F10. OPLS analysis results showed that some typical flavonoid signals abundant in F9 positively correlated with α-glucosidase activity. 2D NMR and UHPLC-HRMS analysis of F9 led to the conclusion that these signals could be attributed to myricetin-3-O-rhamnoside (myricitrin) and epigallocatechin-3-gallate (EGCG). In silico analysis confirmed these results, as myricitrin and EGCG had binding energies resembling acarbose as a positive control (-8.47, -8.19, and -10.13, respectively). ConclusionsNMR and HPLC-metabolomics successfully identified myricitrin and EGCG as α-glucosidase inhibitors from S. polyanthum leaves, and docking analysis validated their inhibitory activity. The results of this study justified the traditional use of S. polyanthum as an antidiabetes herbal.

Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Discrete Self‐Assembled Metallo‐Foldamers with Heteroleptic Sequence Specificity

AbstractDiscrete and structurally diverse foldamer sequences are constructed in both natural and abiotic systems primarily using inert connectivity with irreversible organic covalent bonds, serving to preserve the identity of the sequence. The formation of sequences under thermodynamic control using labile coordination bonds would be attractive for synthetic ease and modular capability, but this presents issues regarding sequence preservation. Here is presented an approach integrating palladium(II) metal ions into the sequence itself, with fidelity maintained through use of complementary pairings of ligand arrangements at the metal centre. This is accomplished using sites of different denticity and/or hydrogen bonding capability. In this fashion, discrete and ordered metallo‐sequences are formed as thermodynamic products in a single step, and these then fold into defined conformations due to π–π interactions between electron‐rich and ‐poor aromatic regions of the combined componentry.

Discrete Self-Assembled Metallo-Foldamers with Heteroleptic Sequence Specificity.

Discrete and structurally diverse foldamer sequences are constructed in both natural and abiotic systems primarily using inert connectivity with irreversible organic covalent bonds, serving to preserve the identity of the sequence. The formation of sequences under thermodynamic control using labile coordination bonds would be attractive for synthetic ease and modular capability, but this presents issues regarding sequence preservation. Here is presented an approach integrating palladium(II) metal ions into the sequence itself, with fidelity maintained through use of complementary pairings of ligand arrangements at the metal centre. This is accomplished using sites of different denticity and/or hydrogen bonding capability. In this fashion, discrete and ordered metallo-sequences are formed as thermodynamic products in a single step, and these then fold into defined conformations due to π-π interactions between electron-rich and -poor aromatic regions of the combined componentry.

Bi-aryl Analogues of Salicylic Acids: Design, Synthesis and SAR Study to Ameliorate Endoplasmic Reticulum Stress.

IntroductionEndoplasmic reticulum (ER) stress condition is characterized as the accumulation of misfolded or unfolded proteins in lumen of ER. This condition has been implicated in various diseases and pathologies including β-cell apoptosis, Alzheimer’s disease and atherosclerosis. We have reported that hydroxynaphthoic acids (HNA), naphthalene analogues of salicylic acid (SA), reduced ER stress. In this study, we explored structural modification to bi-aryl analogues of SA.MethodsPalladium-catalyzed cross-coupling was applied to synthesize bi-aryl analogues of SA. Anti-ER stress activity was monitored by using our cell-based assay system where ER stress is induced by tunicamycin. To monitor ER stress markers, ER stress was induced physiologically relevant palmitate system.ResultsMany analogues decreased ER stress signal induced by tunicamycin. Compounds creating dihedral angle between Ar group and SA moiety generally increased the activity but gave some cytotoxicity to indicate the crucial role of flat conformation of aromatic region. The best compound (16e) showed up to almost 6-fold and 90-fold better activity than 3-HNA and tauro-ursodeoxycholic acid, positive controls, respectively. ER stress markers such as p-PERK and p-JNK were accordingly decreased in Western blotting upon treatment of 16e under palmitate-induced condition.ConclusionAnti-ER stress activity and toxicity profile of bi-aryl analogues of SA could provide a novel platform for potential therapy for protein misfolding diseases.

Phase reversal behavior on two-dimension plane of fluorinated graphene during defluorination

The inverse engineering of structure regulation on graphene plane is underexplored and challenging task because of its fast process and complicated dynamics. Here the slow-released defluorination for fluorinated graphene (FG) was successfully achieved, and we consequently found the “phase reversal” behavior on FG plane during defluorination firstly, rather than widely considered to be an arbitrary defluorination process. Before “phase reversal”, some aromatic regions of island phase generate and fluorinated regions with leading status are continuous phase. After “phase reversal”, the further increased aromatic regions link up into a single stretch as continuous phase reversedly and decreased fluorinated regions split into island phase. For special intermediate state (FG-12h) before “phase reversal”, the excitons of confining aromatic regions easily return to ground state through the radiative recombination pathway, which achieves the strong photoluminescence emission with a quantum yield of ∼56 %. Meanwhile, the produced radicals are relatively stable on the confining aromatic regions. Finally, obtained highly fluorescent FG-12h is applied for detection of Au3+ and its detection concentration is as low as 0.024 μM. This is not attributed to the charge interactions between C–F bonds and Au3+ but also the stable radicals enabling Au3+-radical interactions. Such detection also presents a good selectivity and reversibility.

Ternary aromatic and anti-aromatic clusters derived from the hypho species [Sn2Sb5]3\u2212

Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M2(CO)6Sn2Sb5]3− (M = Cr, Mo), and [(MSn2Sb5)2]4−, (M = Cu, Ag)) in the process of capturing the hypho- [Sn2Sb5]3− in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo2(CO)6Sn2Sb5]3− stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn2Sb5)2]4− and [(CuSn2Sb5)2]4− render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn2Sb5]3−, thus providing conceptual advances in the field of metal-metal bonding in clusters.

Revealing compositional attributes of Glossostemon bruguieri Desf. root geographic origin and roasting impact via chemometric modeling of SPME-GC-MS and NMR metabolite profiles

Glossostemon bruguieri Desf. (Moghat, Sterculiaceae), is a shrub well-known for its thick long-tapering dark colored roots, grown in the Middle East and North Africa. Studies on Glossostemon have focused on its nutritive value and health benefits attributed to its phenolic content with no extensive analysis of secondary metabolome. NMR metabolite fingerprinting of 12 G. bruguieri root specimens of different origins using 1D and 2D experiments identified 12 major primary and secondary metabolites. Orthogonal partial least squares-discriminant analysis (OPLS-DA) of NMR aromatic regions was competent in discriminating between roots origin based on moghatin and pinoresinol levels. Quantification of 1H NMR spectra revealed enrichment of Siwa specimens in sugars i.e., sucrose and inositol (17.89 and 12.06 μg/mg, respectively), as well as some secondary metabolites viz. moghatin, pinoresinol, takakin and fraxetin (7.73, 4.55, 3.81 and 3.03 μg/mg, respectively), posing it for future incorporation in nutraceuticals. However, much less is known regarding aroma and roasting impact on root chemical composition. Volatile profiles of 15 unroasted and roasted specimens were analyzed using headspace solid-phase microextraction coupled to mass spectrometry. 100 Volatile constituents were identified dominated by aldehydes, ethers and mono- and sesquiterpenes, whereas esters were abundant in roasted roots. OPLS-DA identified 2-ethyl-6-methylpyrazine and 5-methyl-2-furfural as roasting descriptors.

Molecular characterization of Dachengzi oil shale kerogen by multidimensional solid-state nuclear magnetic resonance spectroscopy

Solid-state nuclear magnetic resonance (SSNMR) techniques of 13C multiple cross polarization (multiCP), 13C multiCP with recoupled dipolar dephasing (multiCP/DD) and two-dimensional (2D) 1H–13C heteronuclear correlation (HETCOR) were used to characterize Dachengzi oil shale kerogen. Specific structural information was obtained from the quantitative multiCP and multiCP/DD spectra. The protonated aromatic signals distribute widely in the aromatic region and account for 24% of the total aromatic signals. The strong methylene peak in multiCP/DD spectrum indicates the long methylene chain structures. The 2D HETCOR spectra show that oxygen atoms play an important role in the connectivities between different groups. The strong peaks at the 1H/13C chemical shifts of 5/131 and 1.5/131 ppm indicate the high abundance of (–O–CH2)-aromatic and alkyl-substituted aromatic moieties. The connectivities were validated by calculating the chemical shifts of a series of relevant molecular models using quantum chemistry methods. The 13C signal assignment was completed and improved with the multidimensional SSNMR spectra. The results from SSNMR are in agreement with the fast pyrolysis study, and the appearance of (–O–CH2)-aromatic moieties indicates that the methylbenzene homologues in the pyrolysis products can originate from the cleavage of the C–O bonds in (–O–CH2)-aromatic moieties in addition to the β-scission reaction of linear alkylbenzene moieties.

Distinguishing Vinylic and Aromatic 1H NMR Signals Using Selectively Deuterated Chalcones

1H NMR spectroscopy is a molecular characterization technique that is ubiquitously used in research and teaching laboratories alike. Strategic deuteration of molecules is a commonly employed technique in the deconvolution of 1H NMR signals. Here this approach is applied in a second-year chemistry course in which students synthesize 4-methoxychalcone using the Claisen–Schmidt variant of the foundational aldol reaction. The 1H NMR spectrum is complicated by a crowded aromatic and alkene region due in part to extensive conjugation through the two phenyl groups surrounding an α,β-unsaturated ketone. This report demonstrates that students gain competence and confidence in making 1H NMR assignments when presented with a curated set of selectively deuterated chalcones rather than the corresponding spectrum of the fully protiated chalcone. While deuteration does not resolve all of the challenges associated with interpreting this spectrum, it is an invaluable tool to complement chemical shifts (including the predictive nature of resonance structures), integration, and spin–spin splitting. A proposed lecture is presented that is timed to correlate with the performance of the chalcone synthesis lab. Assessment data collected before and after the lecture and then again on the final exam point to the effectiveness of this approach.

Antidiabetic activity screening and nmr profile of vegetable and spices commonly consumed in Indonesia

Apart from their nutritional value, vegetables and spices were empirically known to have functional properties such as antioxidant and antidiabetic activity. However, scientific evidence of these health effects is limited. In our effort to find potent raw material for antidiabetic functional food development, α-glucosidase inhibition and antioxidant activity of 15 Indonesian vegetables and spices methanolic extracts were screened. Their phytochemical profiles were assessed by determining total phenolic content (TPC) and 1H NMR fingerprinting. The results showed that the Syzygium polyanthum, Pluchea indica, Etlingera elaitor, and Cosmos caudatus had the highest GIA (IC50 11.76 ± 0.32, 12.17 ± 0.18, 53.13 ± 2.87, and 61.33 ± 1.21 μg/ml, respectively). The AA and TPC of the four samples were also higher than the others. The 1H NMR profiles of the active samples were different from the non-active samples mainly in the aromatic region. Further observation of the spectra revealed that caffeoylquinic derivatives and esculetin were identified in P. indica; while gallic acid, syringic acid, and myricetin were identified in S. polyanthum. These compounds were known to have antidiabetic activity through different mechanisms.

Aromaticity in Phenyl Decorated closo-Monocarboranes. Planar-Spherical Aggregates Involving 7-12-Vertex Cages.

The characterized phenyl decorated closo-monocarboranes with variable sizes from 7- to 12-vertex cages, [Ph-closo-CBnHn]-, n = 6-11, allow us to address the role of the varying size and shape of the carborane cage in dual planar-spherical aromatic species. Our results show the formation of adjacent shielding cone characteristics enabled from both planar and spherical aromatic fragments, despite the different structures of the closo-monocarboranes. Under a field perpendicular to the phenyl ring, both shielding cones are enabled, which overlap at long-range regions, in contrast to other orientations leading to a short-range response from the planar aromatic fragment. Thus, a two- or one-aromatic circuit is enabled selectively within the same molecular unit, by controlling the orientation of the external field. Along with the series, a variable extension of the shielding cone from the carborane cage is observed, which is larger for the -CB11H11 case, decreasing toward -CB6H6, denoting a similar extension from both the planar and spherical aromatic regions at the [4-Ph-closo-4-CB8H8]- (4) counterpart. The analysis of such multiple aromatic structures shows that, despite the different sizes and shapes of the closo cages, a similar aromatic behavior remains. In addition, the anisotropy of the induced magnetic field is given graphically, denoting a larger anisotropy for the planar aromatic moiety owing to its two-dimensional structure, which is suggested to discriminate between planar and spherical aromatic fragments within the same molecule.