Structure Elucidation Research Articles

An Electrochemical Pipette for the Study of Drug Metabolite.

Electrochemistry offers an effective means of mimicking enzymatic metabolic pathways, particularly the oxidative pathways catalyzed by the cytochrome P450 superfamily. The electrochemical generation and identification of metabolites are time-sensitive, necessitating adjustable cell designs for an accurate mechanistic interpretation. We present a thin-layer electrode (TLE) that addresses the needs of both the analytical and synthetic electrochemical generation of drug metabolites. The TLE's ability to conduct experiments on a minute-to-hour time scale allows for detailed observation of reaction mechanisms for metabolites not easily identified by traditional methods. The utility of the TLE for drug metabolites was benchmarked for electrochemical oxidation of acetaminophen, acebutolol, and 2-acetyl-4-butyramidophenol, known to produce quinone imine metabolites, i.e., NAPQI, upon oxidation. When combined with a microelectrode (μE), the TLE enables probing of the concentration profiles for metabolic oxidation of these drugs. The micromole scale and pipette-type structure of the TLE facilitate comprehensive structural elucidation of intermediates and products using chromatographic and spectroscopic techniques.

Structural elucidation and environmental remediation potential of Ficus carica mediated synthesis of novel Eu3O4/rGO nanocatalyst

A novel europium oxide/reduced graphene oxide (Eu3O4/rGO) nanocatalyst was synthesized via green one pot method and green deposition method using Ficus carica leaves extract. The prepared nanocatalyst was characterized by UV–vis., FTIR, TGA, SEM, HR-TEM, and XRD. Band gaps of Eu3O4/rGO nanocatalyst by green one pot method and green deposition method were found 3.27 and 5.5 eV, respectively. The particle size of Eu3O4/rGO nanocatalyst determined by HRTEM was found 16.9 and 32.1 nm when prepared by using green one pot method and green deposition method, respectively. Significant morphology was observed in the SEM images of Eu3O4/rGO nanocatalysts; where Eu3O4 nanoparticles were observed to be dispersed on chunks of sheets of rGO. The catalytic activity of prepared nanocatalyst was performed against Methylene blue, Rhodamine B, and Ciprofloxacin. The green one pot method demonstrated highest levels of degradation activity 88, 75 and 54 % against MB, CIP, and Rh B pollutants present in wastewater, respectively and helps to achieve SDGs 6 and 13.

Natural products as drug leads: exploring their potential in drug discovery and development.

Natural products have been pivotal in drug discovery, offering a wealth of bioactive compounds that significantly contribute to therapeutic developments. Despite the rise of synthetic chemistry, natural products continue to play a crucial role due to their unique chemical structures and diverse biological activities. This study reviews and evaluates the potential of natural products in drug discovery and development, emphasizing the integration of traditional knowledge with modern drug discovery methodologies and addressing the associated challenges. A comprehensive literature search was conducted across PubMed/MedLine, Scopus, Web of Science, Google Scholar, and Cochrane Library, covering publications from 2000 to 2023. Inclusion criteria focused on studies related to natural products, bioactive compounds, medicinal plants, phytochemistry, and AI applications in drug discovery. Data were categorized into source, extraction methods, bioactivity assays, and technological advances. The current review underscores the historical and ongoing importance of natural products in drug discovery. Technological advancements in chromatographic and spectroscopic techniques have improved the isolation and structural elucidation of bioactive compounds. AI and machine learning have streamlined the identification and optimization of natural product leads. Challenges such as biodiversity sustainability and development complexities are discussed, alongside innovative approaches like biosynthetic engineering and metagenomics. Natural products remain a vital source of novel therapeutic agents, providing unique chemical diversity and specific biological activities. Integrating traditional knowledge with modern scientific methods is essential for maximizing the potential of natural products in drug discovery. Despite existing challenges, ongoing research and technological advancements are expected to enhance the efficiency and success of natural product-based drug development.

“Novel chemo-enzymatic synthesis, structural elucidation and first antiprotozoal activity profiling of the atropoisomeric dimers of trans-8-Hydroxycalamenene”

Leishmaniasis and malaria are two debilitating protozoan diseases affecting millions globally, particularly in tropical and subtropical regions. Current therapeutic options face significant challenges due to emerging drug-resistant strains, necessitating the discovery of novel antiprotozoal agents. This study explores, for the first time, the antiprotozoal potential of calamenenes and their dimers, naturally occurring sesquiterpenes found in essential oils, through a novel chemo-enzymatic synthesis approach. Using the laccase from Trametes versicolor, atropoisomeric dimers of (−)- and (+)-8-trans-hydroxycalamenene were synthesized from commercially available (−)- and (+)-menthol. Structural elucidation was achieved via 2D-NMR spectroscopy, electronic circular dichroism, and DFT calculations. In vitro profiling against Leishmania spp and drug-resistant Plasmodium falciparum revealed that calamenene dimers exhibited significantly higher antiprotozoal activity compared to their monomeric counterparts, highlighting the potential of dimeric terpenoids as promising antiprotozoal agents. This work lays the foundation for developing novel antimalarial drugs based on calamenene scaffolds, encouraging further interactome studies to optimize their pharmacological properties.

Structure elucidation and molecular mechanism of an immunomodulatory polysaccharide from Nostoc commune

Nostoc commune Vaucher, a terrestrial and benthic blue-green alga, widely used in food and medicine worldwide. N. commune Polysaccharides (NCVP) have excellent biological activities, especially immunomodulatory, hypoglycemic and anti-tumor activities. However, the mechanism and structure-activity relationship of NCVP has been less studied. In this study, based on methylation and NMR results, a novel polysaccharide NCVP2 with 135 kDa, containing→4)-α-D-Galp-(1→, → 4)-β-D-Glcp-(1→, and →4)-α-D-Xylp-(1→ residues as the backbon, was sequentially purified from N.commune by DEAE-52 and Sephadex G-100 column. NCVP2 (50 μg/mL) exhibited the strong in vitro immunomodulatory activity by promoting the generation of nitric oxide (NO) and reactive oxygen species (ROS). A total of 2048 differentially expressed genes (DEGs) were identified by RNA-seq, including 1019 down-regulated genes and 1065 up-regulated genes. These DEGs were mainly enriched in the immune-related biological processes, involving in Mitogen-activated protein kinase (MAPK) and Toll-like receptor (TLR) signaling pathways by GO and KEGG enrichment analysis. Furthermore, Western blot results proved NCVP2 could recognize TLR2 and TLR4/MD2, and regulate TLR7/IRF7, MAPK and PI3K/AKT signaling pathways. In summary, a novel polysaccharide NCVP2 from N.commune was proposed to exhibit significant immunomodulatory effects with multiple-paths and targets, and has great potential in the development of healthy foods such as immunomodulators.

Synthesis, structural elucidation, ion flotation and biological evaluation of Ni(II) and Zn(II) Complexes featuring a heterocyclic thiosemicarbazide ligand with their computational studies

Herein, Ni(II) and Zn(II) complexes were synthesized using the heterocyclic thiosemicarbazide ligand (Z)-N-(2-oxoindolin-3-ylidene)nicotinohydrazide (H2L). The structures and geometries of these complexes were identified using elemental analysis, FT-IR, UV-Visible, Mass spectroscopy and thermogravimetric analysis (TGA). These techniques confirmed the composition of the target chelates as [Ni₂(HL)₂Cl₂(H₂O)₄].3H₂O with an octahedral geometry and [Zn(HL)(OAc)(H₂O)] with a tetrahedral geometry. Conductivity measurements indicated the non-ionic nature of the complexes. Moreover, the chelation patterns, structural configurations, and molecular interactions within the complexes were further corroborated through quantum mechanical computations, specifically density functional theory (DFT).An ion flotation method was employed to investigate the removal of nickel and zinc ions from aqueous solutions. This approach involved the formation of a complex between Ni(II) or Zn(II) ions and H₂L, followed by flotation using oleic acid (HOL) as the surfactant. Various parameters, including pH, surfactant and metal ion concentrations, the presence of foreign ions, and temperature, were systematically tested to determine the optimal flotation conditions. Furthermore, the compounds were evaluated for their effects on human carcinoma cells and their antibacterial properties. Additionally, molecular docking studies of the ligand, H₂L and its complexes were performed using the XP Glide module within the Schrödinger suite, targeting HepG2 (PDB ID: 2OH4) and MCF-7 (PDB ID: 3W2S) cell lines.

Variable stoichiometry and a salt-cocrystal intermediate in multicomponent systems of flucytosine: structural elucidation and their impact on stability.

New cocrystals and a salt-cocrystal intermediate system involving the antifungal drug flucytosine (FCY) and various coformers including caffeic acid (CAF), 2-chloro-4-nitrobenzoic acid (CNB), hydroquinone (HQN), resorcinol (RES) and catechol (CAL), are reported. The crystal structures of the prepared multicomponent systems were determined through SC-XRD analysis and characterized by different solid-state techniques. All FCY multicomponent systems crystallize in anhydrous form with different stoichiometric ratios. The cocrystals FCY-HQN, FCY-RES and FCY-CAL crystallize in 2:0.5, 2:0.5 and 3:2 stoichiometric ratios respectively. In contrast, FCY-CAF and FCY-CNB crystallize in a 1:1 stoichiometric ratio. The FCY-CAF cocrystal is formed via an acid-pyrimidine heterosynthon. Due to the partial proton transfer from the acid group of CNB to FCY, a three-point homosynthon is observed between two FCY molecules and the molecules interact via an N-H...O hydrogen bond between FCY and CNB. In FCY phenolic cocrystals, a single-point O-H...O hydrogen bond is observed. The formation of cocrystals and salt-cocrystal intermediate was further confirmed by difference Fourier map analysis and bond angle differences. Except for FCY-CAL, all the multicomponent systems were reproduced in the bulk scale for further characterization. A detailed Crystal Structural Database search was carried out on the multicomponent systems of FCY with acid coformers and we evaluated the formation of cocrystals/salt based on the ΔpKa values, the difference in the bond distances and bond angles. Additionally, the prepared multicomponent systems exhibited hydration stability for one month under accelerated conditions [40 (2)°C and relative humidity 90-95 (5)%].

Podocarpane and cleistanthane diterpenoids from Strophioblachia glandulosa: Structural elucidation, anti-hypertrophy activity and network pharmacology

In the present investigation, fourteen unprecedented podocarpane diterpenoids strophiolosas A-J, L-N and P (1–10, 12–14, 16), two new cleistanthane derivatives strophiolosas Q-R (17–18), two new dibenzopyroan-ones and one new tetralone strophiolosas S-U (19–21), were isolated from the whole plant of Strophioblachia glandulosa. The structures were elucidated via various spectroscopic analysis, quantum chemistry calculations, and X-ray diffraction. Bioactivity test indicated that compounds 5 and 17 possessed promising anti-cardiac hypertrophy effect in vitro (IC50 values of 16.50 and 9.67 μM). Additionally, through network pharmacology prediction, PARP1 may be a potential target of compound 17, mediating its anti-hypertrophic effects through multiple pathways.

New Antioxidant Caffeate Esters of Fatty Alcohols Identified in Robinia pseudoacacia

The stem bark of black locust (Robinia pseudoacacia L.) was extracted, and nine antioxidant compounds (R1–R9) were detected by high-performance thin-layer chromatography combined with the radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay, multi-detection, and heated electrospray high-resolution mass spectrometry. For structure elucidation, the methanolic crude extract was fractionated by solid-phase extraction, and the compounds were isolated by reversed-phase high-performance liquid chromatography with diode array detection. The structures of isolated compounds were elucidated by nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy as well as gas chromatography-mass spectrometry to determine the double bond position. 3-O-Caffeoyl oleanolic acid (R1), oleyl (R2), octadecyl (R3), gadoleyl (R4), eicosanyl (R5), (Z)-9-docosenyl (R6), docosyl (R7), tetracosyl (R8), and hexacosanyl (R9) caffeates were identified. While R1 has been reported in R. pseudoacacia stem bark, the known R3, R5, R7, R8, and R9 are described for the first time in this species, and the R2, R4, and R6 are new natural compounds. All nine caffeates demonstrated antioxidant activity. The antioxidant effects of the isolated compounds R1–R8 were quantified by a microplate DPPH• assay, with values ranging from 0.29 to 1.20 mol of caffeic acid equivalents per mole of isolate.

Synthesis, characterization, DNA, BSA, antimicrobial, antioxidant and molecular docking studies of gadolinium(III) based complexes

The present study reports the synthesis of two new gadolinium-metal-based complexes with mixed ligands, [Gd(L1)2(py)(H2O)3] (C1) and [Gd (L2)2(phen)(H2O)2] (C2), where L1 represents 3-(4 cyanophenyl) acrylate and L2 as 3-(4 fluorophenyl) acrylate. The complexes were characterized by various analytical techniques including FT-IR, PXRD, TGA, DSC, SEM and EDX to determine structural elucidation, binding mode, crystallinity, thermal stability, morphology and elemental composition, respectively. The synthesized complexes were tested for DNA (salmon sperm) and BSA interaction studies to infer their antitumor potential. The binding constants obtained for C1 and C2 with SS DNA were 3.03 × 104 and 3.2 × 104 while with BSA observed as 1.59 × 105 and 1.22 × 105, respectively. In vitro antimicrobial potential of both complexes was determined against various bacterial and fungal strains. Experimental results showed complex C2 is more active than C1 against all selected bacterial strains and showed higher antibacterial potential against E. coli with a zone of inhibition (ZOI) of 35 mm. The antibacterial potential of C2 was further investigated by calculating the MIC (IC50) value. MIC of complex C2 was assessed using visual inspection (turbidity) and spectrophotometric assay at 600 nm. The findings of the spectrophotometric approach have greater sensitivity than the standard disc diffusion assays. The molecular docking studies were conducted to validate further and compare the findings of experimental results which exhibited that complex C2 has an excellent binding capacity with the target protein (5CDQ) with free binding energy −12.23 kcal/mol. Antioxidant potentials of the complexes were assessed using phosphomolybdenum assay, which demonstrated that complex C2 exhibits higher antioxidant activity than complex C1.

A new coumarin derivative and other compounds from Achillea alpina L. and their chemotaxonomic significance

Phytochemical investigation of the aerial parts of Achillea alpina L. (Asteraceae) led to the isolation and structural elucidation of one previously undescribed isofraxidin derivative and fifteen known compounds including five lignans (2–5, and 16), one coumarin glucoside (6), four flavonoids (7–10), three feruloylsucrose derivatives (11–13), one caffeoylquinic acid (14), and one polyacetylene (15). Their structures were determined by analyzing HR-ESI-MS and NMR data and comparing them with those in the references. To the best of our knowledge, this study was the first report of isolating compounds 1–4 and 13 from the family Asteraceae, compounds 1–4, 6, 13, and 15 from the genus Achillea, and compounds 1–6, 11–13, and 15 from A. alpina. Their chemotaxonomic significance was also discussed.

MS-DIAL 5 multimodal mass spectrometry data mining unveils lipidome complexities

Lipidomics and metabolomics communities comprise various informatics tools; however, software programs handling multimodal mass spectrometry (MS) data with structural annotations guided by the Lipidomics Standards Initiative are limited. Here, we provide MS-DIAL 5 for in-depth lipidome structural elucidation through electron-activated dissociation (EAD)-based tandem MS and determining their molecular localization through MS imaging (MSI) data using a species/tissue-specific lipidome database containing the predicted collision-cross section values. With the optimized EAD settings using 14 eV kinetic energy, the program correctly delineated lipid structures for 96.4% of authentic standards, among which 78.0% had the sn-, OH-, and/or C = C positions correctly assigned at concentrations exceeding 1 μM. We showcased our workflow by annotating the sn- and double-bond positions of eye-specific phosphatidylcholines containing very-long-chain polyunsaturated fatty acids (VLC-PUFAs), characterized as PC n-3-VLC-PUFA/FA. Using MSI data from the eye and n-3-VLC-PUFA-supplemented HeLa cells, we identified glycerol 3-phosphate acyltransferase as an enzyme candidate responsible for incorporating n-3 VLC-PUFAs into the sn1 position of phospholipids in mammalian cells, which was confirmed using EAD-MS/MS and recombinant proteins in a cell-free system. Therefore, the MS-DIAL 5 environment, combined with optimized MS data acquisition methods, facilitates a better understanding of lipid structures and their localization, offering insights into lipid biology.

Batrachopolyenes: Volatile Norsteroids from Femoral Scent Glands of Frogs

Steroid hormones are C18‐C21‐sterane derivatives, featuring the typical 6‐6‐6‐5 ring system. Here we report on a novel C18‐steroid ring system named batrachane with a contracted A‐ring resulting in a 5‐6‐6‐5 ring arrangement. The isolation, structural elucidation, and total synthesis of three members of the novel batrachopolyene family occurring in the tropical frog genus Odontobatrachus is reported. The batrachopolyenes represent an entirely new collection of volatile steroidal natural products produced by anuran amphibians. Alongside the contracted A‐ring, each member contains a Δ16‐17 double bond but differs in the central belt of the steroidal structure. To create these atypical structural features, syntheses featuring a combination of Breslow radical chain relay chlorination, Favorskii ring contraction, and Clemmensen reduction proved successful. The occurrence of such compounds in another distal anuran group, the Mantellinae, suggests a more widespread distribution of the batrachane‐type compounds among frogs. The new structural steroid type raises questions concerning steroid biosynthesis and reception, as well as distribution in frogs in general and the structures of their hormones.

Exploration of Aflatoxin B1 Degradation Products via Kocuria rosea: Structure Elucidation and Toxicity Analysis

Aflatoxin B1, a natural mycotoxin produced by Aspergillus fungi with high toxicity and carcinogenicity to humans and animals, has attracted more and more attention in the past 40 years. In the study of the biological detoxification of aflatoxin B1—although it has been confirmed that Kocuria rosea has the ability to efficiently remove aflatoxin B1—the degradation products, degradation pathways, and toxicity of the degradation products of aflatoxin B1 have not been clarified. Therefore, in this study, it was found that the functional groups of aflatoxin B1 changed after being cultured with Kocuria rosea, indicating the production of aflatoxin B1 degradation products. Ten main AFB1 degradation products (including aflatoxicol, aflatoxin D1, and aflatoxin D2) were identified, and their structures and fragmentation mechanisms were further elucidated by the parent ions and fragment ions of the products. The possible degradation pathway of aflatoxin B1 was proposed according to the structure of the degradation products. Additionally, the toxicity of the degradation products was analyzed according to the quantitative structure–activity relationship theory, and cytotoxicity experiments and dead–live cell staining experiments showed that the toxicity of the degradation products was significantly less than that of aflatoxin B1. In this study, the mechanism of aflatoxin B1 degradation by Kocuria rosea was explored from several perspectives, indicating that aflatoxin B1 degradation by Kocuria rosea is a promising biological method.

Batrachopolyenes: Volatile Norsteroids from Femoral Scent Glands of Frogs.

Steroid hormones are C18-C21-sterane derivatives, featuring the typical 6-6-6-5 ring system. Here we report on a novel C18-steroid ring system named batrachane with a contracted A-ring resulting in a 5-6-6-5 ring arrangement. The isolation, structural elucidation, and total synthesis of three members of the novel batrachopolyene family occurring in the tropical frog genus Odontobatrachus is reported. The batrachopolyenes represent an entirely new collection of volatile steroidal natural products produced by anuran amphibians. Alongside the contracted A-ring, each member contains a Δ16-17 double bond but differs in the central belt of the steroidal structure. To create these atypical structural features, syntheses featuring a combination of Breslow radical chain relay chlorination, Favorskii ring contraction, and Clemmensen reduction proved successful. The occurrence of such compounds in another distal anuran group, the Mantellinae, suggests a more widespread distribution of the batrachane-type compounds among frogs. The new structural steroid type raises questions concerning steroid biosynthesis and reception, as well as distribution in frogs in general and the structures of their hormones.

SUSTAINABLE AND SCALABLE ENZYMATIC PRODUCTION, STRUCTURAL ELUCIDATION, AND BIOLOGICAL EVALUATION OF NOVEL PHLORIZIN ANALOGUES.

It is not unusual for naturally occurring compounds to be limited for their use in cosmetics due to their low water solubility. Recently, aiming at accessing novel phlorizin analogues, we reported the synthesis of very promising - but low water-soluble - biomass-derived chalcones (CHs) and dihydrochalcones (DHCs) exhibiting antioxidant and anti-tyrosinase activities. Glycosylating bioactive compounds being one of the most common strategies to increase water solubility, herein we report the enzymatic glycosylation of the aforementioned CHs, as well as DHC, using cyclodextrin glycosyltransferases (CGTase), enzymes well-known for catalyzing the selective ⍺(1→4)transglycosylation. Indeed,while most natural glycosides areβ-glycosides (such as phlorizin), the selected enzyme produces selectively newα-glycosides, thus expanding their structural diversity. A first separation using Centrifugal Partition Chromatography (CPC) led to mono-, di- or triglycosides-enriched fractions, which were then submitted to a comprehensive purification strategy for an in-depth chemical profiling of the synthesizedα-glycosides, revealingas major compounds. Surprisingly, among the diglycosides characterized, besides the expected maltoside compounds, nigeroside derivatives were also identified in significant amounts, depending on the starting compound structure. Finally, evaluating the antiradical, anti-tyrosinase and antimicrobial activities of the major glycosides revealed them as potential sustainable alternatives to current petro-sourced cosmetic ingredients.

Synthesis, structural elucidation, and DNA binding behavior of a ternary copper(II) complex featuring substituted bipyridyl and dicarboxylate ligands

The present research study is centered around the synthesis, characterization, and biological application of a ternary mixed-ligand based binuclear Cu(II) complex [Cu2(trans-1,4-chdc)(4,4′-Me2-2,2′-bpy)2(5,5′-Me2-2,2′-bpy)2]·2(cis-H21,4-chdc)·2(BF4¯) (1) by meticulous incorporation of 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me2-2,2′-bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2-2,2′-bpy) and cis- andtrans- mixture of 1,4-cyclohexanedicarboxylic acid (H21,4-chdc). Hirshfeld analysis is employed to validate non-bonded interactions, demonstrating the existence of widespread π···π stacking interactions between adjacent 4,4′-Me2-2,2′-bpy ligands at a distance of 3.757 Å, forming a one-dimensional (1D) supramolecular polymer chain. The biological activity of complex 1 is explored via docking study, driven by the inherent biological inclination of the Cu(II) complexes. Agreeably, the coordination complex 1 displays a favorable binding to DNA, specifically binds to the major groove of DNA and the aromatic pyridine ring of the ligand partially intercalates into the base pairs with a binding constant (Kb) of 1.98 × 105 M−1.

GT-NMR: a novel graph transformer-based approach for accurate prediction of NMR chemical shifts

In this work, inspired by the graph transformer, we presented an improved protocol, termed GT-NMR, which integrates 2D molecular graph representation with Transformer architecture, for accurate yet efficient prediction of NMR chemical shifts. The effectiveness of the GT-NMR was thoroughly examined with the standard nmrshiftdb2 dataset, 37 natural products and structural elucidation of 11 pairs of natural products. Systematical analysis affirms that GT-NMR outperforms traditional graph-based methods in all aspects, achieving state-of-the-art performance, with the mean absolute error of 0.158 and 1.189 ppm in predicting 1H and 13C NMR chemical shifts, respectively, for the standard nmrshiftdb2 dataset. Further scrutiny of its practical applications indicates that GT-NMR's efficacy is closely tied to molecular complexity, as quantified by the size-normalized spatial score (nSPS). For relatively simple molecules (nSPS < = 27.71), GT-NMR performs comparably to the best density functional while its effectiveness significantly diminishes with complex molecules characterized by higher nSPS values (nSPS > = 38.42). This trend is consistent across other graph-based NMR chemical shift prediction methods as well. Therefore, while employing GT-NMR or other graph-based methods for the rapid and routine prediction of NMR chemical shifts, it is advisable to utilize nSPS to assess their suitability. The source codes and trained model of GT-NMR are publicly available at GitHub.Scientific contributionGT-NMR, which combines the 2D molecular graph representation with the Transformer architecture, was implemented for the first time to predict atom-level NMR chemical shifts, achieving state-of-the-art performance. More importantly, the reliability of the GT-NMR and graph-based methods was assessed for the first time in terms of molecular complexity, as quantified by the size-normalized spacial score (nSPS). Systematical scrutiny demonstrated that GT-NMR offer a valuable way for routine application in structural screening and elucidation of relatively simple molecules.

Structural Elucidation of the 1D Cd(II) Coordination Polymer and Its Application in the Selective Detection of TNP and the Schottky Diode Device Fabrication

Structural Elucidation of the 1D Cd(II) Coordination Polymer and Its Application in the Selective Detection of TNP and the Schottky Diode Device Fabrication

Elucidation of Electronic Structures of Mixed-Valence States Induced by dσ-π Charge Delocalization in Linear-Chain and Discrete Rhodium-Dioxolene Tetrameric Complexes.

We have successfully synthesized unique linear-chain and discrete mixed-valence tetrameric complexes, {[Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4·hexane}∞ (4) and [Rh(3,6-DBDiox-4,5-S2CO)(CO)2]4 (5), by carefully choosing the solvent. X-ray photoelectron spectra (XPS) confirm that 4 and 5 are in the Rh(I,II) mixed-valence state. Analyses of the metrical oxidation state (MOS) of dioxolene ligands reveal that in 4 and 5, the electron density corresponding to one electron per tetramer is transferred from Rh(I) ions to semiquinonato ligands, and the transferred charge is delocalized throughout the four dioxolene ligands. Due to their mixed-valence state, 4 and 5 are semiconductors with relatively high electrical conductivity at room temperature. Density functional theory (DFT) calculations of tetrameric complex demonstrated for the first time that the dσ* orbitals of the Rh atoms and the π* orbitals of the semiquinonato ligands, which are originally highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), respectively, strongly hybridize with each other, leading to the Rh(I,II)-semiquinonato/catecholato mixed-valence state. Furthermore, time-dependent (TD)-DFT calculations have also revealed that the low energy absorption band observed centered at 5700 cm-1 is attributed to a charge transfer from [dσ*(Rh)] (HOMO) or [π*(SQ)-dσ*(Rh)] (HOMO-1) to [π*(SQ)-dσ*(Rh)] (LUMO/LUMO+1). Although 4 and 5 are tetramers with nearly identical structures, their magnetic interactions are found to differ significantly depending on their crystal structures.