Structure Analysis Research Articles

Titanium (IV) μ-Oxo Complex Supported by Phenoxyimine Ligand: Synthesis, Crystal Structure Characterisation, DFT and Molecular Docking Studies

Background: Most of the transition elements in the 3d series (first row transition metals) have been discovered to be extremely significant and practical in biological systems. Naturally, many of the enzymes that are present in the human body system act as catalysts for biological processes and are made of coordination compounds or complexes. Objective: The complex has been characterised by various spectroscopic and analytic techniques. A suitable crystal analysed by X-ray diffraction establishes the formation of a stable binuclear µ-oxo-complex with a hexacoordinate titanium centre. Methods: A new crystalline complex [Ti{La}] has been synthesised in the reaction of titanium butoxide with a phenoxyimine ligand in a 1:1 stoichiometry in toluene at room temperature under a nitrogen atmosphere. The newly synthesised Ti complex has undergone density functional theory and docking study. Results: The crystal shows a monoclinic system with space group C 1 2/c 1. X-ray crystal structure analysis reveals that this complex has a rhomboidal Ti-O-Ti core and exhibits a C2 symmetric conformation with distorted octahedral geometry. Density Functional Theory (DFT) calculations giving insights into the frontier orbitals and mulliken charge analysis, which showed good correlation with the experimental findings. Additionally, in silico molecular docking of ligand and complex was carried out against the HER2 inhibitor kinase. Conclusion: This complex exhibits a higher binding energy of ΔGb = -19.7 kcal/mol with the active pocket of HER2 (PDB:7JXH) than the ligand ΔGb = -8.5 kcal/mol.

Conceptual Mechanical Structure Analysis of A 16 T Canted Cosine Theta (CCT) Magnet

Conceptual Mechanical Structure Analysis of A 16 T Canted Cosine Theta (CCT) Magnet

Diversity and Isolation of Endophytic Fungi in Panax japonicus and Biotransformation Activity on Saponins.

This study reports the diversity and community structure differences of the endophytic fungi of Panax japonicus of different ages to obtain novel endophytic fungi with glycoside hydrolytic activity for rare saponins production. This study used the high-throughput sequencing method to analyze the diversity and community structure of endophytic fungi of P. japonicus. The endophytic fungi were processed by traditional isolation, culture, conservation, and ITS rDNA sequence analyses. Then the total saponins of P. japonicus were used as the substrate to evaluate the glycoside hydrolytic activity. The composition analysis of the community structure showed that the abundance, evenness, and diversity of endophytic fungi of nine-year-old P. japonicus were the best among all samples. A total of 210 endophytic fungi were isolated from P. japonicus samples and further annotated by sequencing the internal transcribed spacer. Then the biotransformation activity of obtained strains was further examined on total saponins of P. japonicus (TSPJ), with a strain identified as Fusarium equiseti (No.30) from 7-year-old P. japonicus showing significant glycoside hydrolytic activity on TSPJ, including ginsenoside Ro→zinglbroside R1, pseudoginsenoside RT1→pseudoginsenoside RP1, chikusetsusaponin IV→tarasaponin VI and chikusetsusaponin IVa →calenduloside E. These results reveal the diversity and community structure differences of the endophytic fungi of P. japonicus with different ages and establish a resource library of endophytic fungi of P. japonicus. More importantly, we identified a valuable endophytic fungus with glycoside hydrolytic activity and provided a promising convenient microbial transformation approach to produce minor deglycosylated ginsenosides.

Cryo-EM and Molecular Dynamics Simulations Reveal Hidden Conformational Dynamics Controlling Ammonia Transport in Human Asparagine Synthetase.

How motions in enzymes might be linked to catalytic function is of considerable general interest. Recent advances in X-ray crystallography and cryogenic electron microscopy offer the promise of elucidating functionally relevant motions in proteins that are not easily amenable to study by other biophysical methods. Here we use 3D variability analysis (3DVA) on cryo-EM maps for wild type (WT) human asparagine synthetase (ASNS) and the R142I ASNS variant to identify conformational changes in the Arg-142 side chain, which mediates the formation of a catalytically relevant intramolecular tunnel. Our 3DVA results for WT ASNS are consistent with independent molecular dynamics (MD) simulations on a model generated from the X-ray structure of human ASNS. Moreover, MD simulations of computational models for the ASNS/β-aspartyl-AMP/MgPPi and R142I/β-aspartyl-AMP/MgPPi ternary complexes, suggest that the structural integrity of the tunnel is impaired in the R142I variant when β-aspartyl-AMP is present in the synthetase active site. The kinetic properties of the R142I ASNS variant support the proposed function of Arg-142. These studies illustrate the power of cryo-EM to identify localized motions and dissect the conformational landscape of large proteins. When combined with MD simulations, 3DVA is a powerful approach to understanding how conformational dynamics might regulate function in multi-domain enzymes possessing multiple active sites.

Identification and Phylogenetic Analysis of Venom Allergens from Transcriptome of Hemiscorpius lepturus Scorpion

Introduction: Venom allergens have been identified in the venom of scorpion, snake, bee, wasp, etc. Some allergy reactions in humans may refer to the venom allergens. Aim: Phylogenetic analysis of venom allergens from the transcriptome of Hemiscorpius lepturus scorpion was the main aim of the study. Methods: Seven venom allergens: HLAllergen1, HLAllergen2, HLAllergen3, HLAllergen4, HLAllergen5, HLAllergen6, and HLAllergen7 have been identified in the venom of Hemiscorpius lepturus scorpion using venom gland transcriptome analysis. Primary, secondary and tertiary structures of the identified venom allergens were predicted using ExPASy ProtParam, PSIPRED, and SWISS MODEL servers. Phylogenetic tree was constructed using MEGA 11 software through neighbor-joining method with 1000 bootstraps. Results: Structure analysis of identified venom allergens showed a molecular weight of between 46 to 52 kDa. Tertiary structure results showed that all predicted 3-D structures were in a normal range. Phylogenetic tree analysis showed that HLAllergen 3, 4 and 5 were formed single clades and HLAllergen 1, 2, 7, and 6 other clades Conclusion: However, further studies using proteomic analysis of H. lepturus are needed to confirm and compare with transcriptome data.

Review of Patents Analysis on Floor Robot Vacuum

Background: As the pace of life gets faster, and with the development and progress of society and the continuous improvement of people's pursuit of a convenient and comfortable life, it has become a growing desire for people to get rid of tedious housework. Hygienic automatic cleaning has also become the main demand of people. Objective: Through review, analysis, and discussion of the patents on existing floor robot vacuums, it is expected to find out the development process and main outcomes, along with the main technologies involved, and provide a valuable prediction basis for future research and development directions. Methods: This study aimed to summarize a number of representative patents related to floor robot vacuums and their main components and analyze them in depth to study their technical points and development laws. Results: By summarizing a large number of patents on floor robot vacuums and further analyzing and comparing the characteristics of the patents, the future development trend of floor robot vacuums was further discussed. Conclusion: Through a detailed analysis of the mechanical structure, intelligent control technology, and sensor technology of the existing floor robot vacuums as a whole and the main work unit, this study discussed the ideas and methods of improving the new floor robot vacuum, which is of great significance to its operation and more convenient and intelligent.

Codon Usage Characteristics and Evolutionary Analysis of Mitochondrial Genome of Winter Squash (Cucurbita maxima Duch.)

Mitochondrial genomes are essential components of eukaryotic cells, understanding their structural characteristics and codon usage bias is critical. Winter squash (Cucurbita maxima Duch ex Poiret) is an economically important cucurbit crop. To clarify its structural characteristics and codon usage bias of mitochondrial genome, as well as the evolutionary characteristics in the Cucurbitaceae family, whole genome sequencing analysis of C. maxima mitochondrial genome was carried out. The results revealed that the total length of the C. maxima mitochondrial genome was 640,814 bp, containing 9,162,318,300 bp of bases. There were 68 annotated genes identified. The mitochondrial coding genes of C. maxima exhibited an average GCall content of 42.57%, with the last position enriched in A/T bases. Codon usage analysis indicated weak codon bias, with the effective codon number (ENC) ranging from 44.22 to 61.00. Correlation analysis and neutrality plot analysis demonstrated a nonsignificant correlation between GC3 and GC12. PR2-plot and ENC-plot analysis further supported the influence of natural selection on the codon preference in the C. maxima mitochondrial genome. Relative synonymous codon usage (RSCU) analysis identified 19 optimal codons, with a preference for U or A as the final base. The analysis of scattered repeat sequences in the genome indicated a high frequency of forward and palindromic repeats in the C. maxima mitochondrial genome. Nucleic acid diversity analysis highlighted rpl5 as the gene with the highest variability. Comparative analysis of mitochondrial structure and phylogenetic tree analysis revealed a close evolutionary relationship between C. maxima and Cucurbita pepo, showing synteny in evolution. Homologous fragment analysis demonstrated a similarity of over 70% between the C. maxima mitochondrial genome and chloroplast genome fragments. These findings provide a foundation for C. maxima identification and phylogenetic studies.

TOI-663: A newly discovered multi-planet system with three transiting mini-Neptunes orbiting an early M star

We present the detection of three exoplanets orbiting the early M dwarf TOI-663 (TIC 54962195; V = 13.7 mag, J = 10.4 mag, R★ = 0.512 ± 0.015 R⊙, M★ = 0.514 ± 0.012 M⊙, d = 64 pc). TOI-663 b, c, and d, with respective radii of 2.27 ± 0.10 R⊕, 2.26 ± 0.10 R⊕, and 1.92 ± 0.13 R⊕ and masses of 4.45 ± 0.65 M⊕, 3.65 ± 0.97 M⊕, and <5.2 M⊕ at 99%, are located just above the radius valley that separates rocky and volatile-rich exoplanets. The planet candidates are identified in two TESS sectors and are validated with ground-based photometric follow-up, precise radial-velocity measurements, and high-resolution imaging. We used the software package juliet to jointly model the photometric and radial-velocity datasets, with Gaussian processes applied to correct for systematics. The three planets discovered in the TOI-663 system are low-mass mini-Neptunes with radii significantly larger than those of rocky analogs, implying that volatiles, such as water, must predominate. In addition to this internal structure analysis, we also performed a dynamical analysis that confirmed the stability of the system. The three exoplanets in the TOI-663 system, similarly to other sub-Neptunes orbiting M dwarfs, have been found to have lower densities than planets of similar sizes orbiting stars of different spectral types.

Leksikos vartosenos tyrimai ir leksikografinė praktika

The article presents research on the usage of Lithuanian lexis and lexicographical works on the Lithuanian language from the beginning of the 20th century to the present day. It reveals how scientific research has been related to academic activity and lexicographic work (data gathering, analysis, dictionary development), and vice versa. Talking about the early and mid-20th century, the focus lies on the well-grounded articles on appropriate language use by Kazimieras Būga and on the preparation of the “Dictionary of the Lithuanian Language”, as well as on Jonas Jablonskis’ interest in the standard language, creation of new words, his work on the dictionary of Antanas Juška and his reviews of earlier dictionaries. Jablonskis’ own “Mūsų žodynėlis” [Our Dictionary] is also briefly discussed. Further on, the article talks about the work of Juozas Balčikonis and the beginnings of the academic “Dictionary of the Lithuanian Language”. Particular mention is made of Pranas Skardžius’ and Antanas Salys’ research on word structure and usage. In addition, various articles in language journals as well as the structure and editorial principles of the journal “Kalbos patarėjas” are reviewed. The research in the Soviet era is mainly associated with the lexicographical activities of Jonas Kruopas and Kazys Ulvydas and the editorial work on both the (historical) “Dictionary of the Lithuanian Language” and the “Dictionary of the Present Lithuanian Language”. The research interest of this period lies primarily in the analysis of lexical structure and systemic relations, whereas publication activity focuses on editing special dictionaries (such as dictionaries of synonyms, antonyms, valency, phraseology, and comparisons), and the publication of textbooks and monographs in the field of lexicology. The article gives an overview of studies that analyse the development and change of various lexical items, describe different semantic groups, language variation, and its phrasal components. Furthermore, lexical databases and the information system e.kalba are given an overview. The main focus here lies on reviewing lexical research and lexicographical projects carried out in the 1990s and the early 21st century, and on revealing lexicographical problems.

Characterization, crystal structure and stability analysis of dianhydrodulcitol polymorphs

1,2:5,6-Dianhydrogalactitol (DAG), an anticancer drug with different crystal structures, is investigated in order to get a comprehensive understanding of its polymorphism. Two polymorphs of DAG were prepared by different methods using DAG form I as the starting material. The formation of new crystal forms was confirmed by means of PXRD and other characterization methods. The single crystals of three polymorphs, including a new discovered crystal form II, were prepared and studied. The crystal structure of the new crystal form II was determined by single crystal X-ray diffraction, and the difference in hydrogen bonding structure of the DAG polymorphs was analyzed. The intermolecular interactions of the DAG polymorphs were studied by Hirshfeld surface analysis. The stability relationship between three polymorphs under different conditions was studied. DAG form I is stable at low temperatures and form III is more stable at high temperatures. Form II is a metastable crystal form and can be transformed into the other two crystal forms by solvent-mediated crystallization.

Evidence for the Use of Karst Tiankengs as Shelters: The Effect of Karst Tiankengs on Genetic Diversity and Population Differentiation in Manglietia aromatica

Karst tiankengs in China are globally significant locations for studying ecological environments and plant diversity. However, there are few reports on how the unique geographical environment of tiankengs affects plant genetic diversity and genetic structure. This study used Hyper-seq gene sequencing technology to develop large-scale genomic SNPs of Manglietia aromatica, both within and outside the tiankengs. Its aim was to investigate the impact of tiankengs on the genetic diversity and genetic structure of the M. aromatica population. The analysis results indicate that the genetic diversity of the populations within the tiankeng (π = 0.2044) is higher than that of the populations outside of it (π = 0.1671), indicating that the tiankengs have a positive impact on species diversity. The genetic differentiation coefficient (FST) between the populations inside and outside the tiankeng was 0.0534 and the FST values of populations within the tiankeng were 0.077, 0.082, and 0.141, meaning that the genetic variation in the tiankengs is very high. The genetic similarity outside the tiankengs is also very high, indicating that the tiankengs are effectively preserving the genetic diversity of M. aromatica. Furthermore, the gene introgression analysis results gave no proof of gene flow between the three tiankeng populations. This suggests that the tiankengs not only protect species diversity, but also hinder gene flow between populations to some extent. However, this hindrance may gradually subside with the evolution of the tiankengs. The genetic structure analysis revealed that the M. aromatica population in Guangxi, China, can be classified into three subpopulations. The first is the tiankeng subpopulation, including all the populations in tiankengs. The second subpopulation consists of populations surrounding the tiankengs. These two subpopulations are distributed in Leye County in northwestern Guangxi, China, and are very close to each other. The third is the Huanjiang subpopulation, which is located far away from the tiankengs. Considering the direction of gene flow and genetic structure, it is speculated that the populations in the tiankengs evolved from the populations near the pit mouth. This study confirms that the tiankengs are shelters and provide a suitable habitat for the endangered plant M. aromatica, because its genetic diversity is well conserved and the species is well adapted to the habitat within the tiankengs.

Polysubstitution Induced Centrosymmetric-to-Noncentrosymmetric Structural Transformation and Nonlinear-Optical Behavior: The Case of Na0.45Ag0.55Ga3Se5.

Obtaining compounds with large nonlinear-optical (NLO) coefficients and wide band gaps is challenging due to their competitive requirements for chemical bonds. Herein, the first member with mixed cations on the A site in the A-M3-Q5 or A-Ag-M6-Q10 (A = alkali metal; M = Ga, In; Q = S, Se, Te) family, viz. Na0.45Ag0.55Ga3Se5 (NAGSe), was obtained by a solid-state reaction. Its structure features [GaSe4] tetrahedra built three-dimensional {[Ga3Se5]-}∞ network, with Na and Na/Ag cations located at the octahedral cavities. Noncentrosymmetric (R32) NAGSe can also be transformed from centrosymmetric RbGa3S5 (P21/c) via multiple-site cosubstitution. NAGSe exhibits the highest NLO response (1.9 × AGS) in the A-Ag-M-Q family. Crystal structure analysis and theoretical calculations suggest that the NLO response is mainly contributed by the regularly arranged [GaSe4] units. This work enriches the exploration of the undeveloped A-M3-Q5 or A-Ag-M6-Q10 family as potential infrared NLO materials.

Geochemical Evaluation of Manganese Neutralization Sludge for Mn-Containing Mine Drainage Treatment

Conventional neutralization treatment for manganese (Mn)-bearing mine drainage provides a challenge of cost-efficiency, and new approaches should be explored for efficient removal of Mn. We focused on Mn neutralization sludge, a by-product of the Mn-bearing drainage treatment process, which was assumed to be useful as a water purification material. Mn and zinc (Zn) removal tests in simulated drainage were performed using Mn neutralization sludge, and the reaction mechanism was elucidated using geochemical modeling and X-ray absorption fine structure (XAFS) analysis. The results showed that the addition of sludge enabled to lower the Mn and Zn concentration below Japanese effluent standard (10 mg dm−3 for Mn; 2 mg dm−3 for Zn) within 1 h. Furthermore, heavy metal immobilization was achieved at neutral pH (7–8) with the sludge addition, while the conventional neutralization process without adding the sludge requires higher pH (>10) to lower Mn concentration. These removal behaviors were not explainable by considering only well-known phenomena: hydroxide precipitation, surface complexation reaction onto δ-MnO2, and autocatalytic Mn oxidation. Hence, we advanced the geochemical model for simulation, suggesting that a surface complexation reaction onto γ-MnOOH greatly contributed to the removal of Mn. Besides, Zn was calculated to be predominantly precipitated as ZnMn2O4. Solid residue analysis by XAFS measurement supported the result of above calculation, validating the reliability of the constructed geochemical model. Overall, we concluded that the advanced geochemical model would be useful in predicting the Mn and Zn behavior during mine drainage treatment with Mn neutralization sludge.Graphical abstract

Analysis of Structure and Function of Ladybird Leg and Subsequent Design and Fabrication of a Simplified Leg Structure for Robotic Applications.

Many insects are able to walk vertically or upside down on both hard and soft surfaces. In beetles such as the ladybird (Coccinella septempunctata), intermolecular forces between tarsal setae on the footpads of the insects make this movement possible. In prior work, adhesion structures made from polydimethylsiloxane (PDMS) that mimic the action of the tarsal setae have been developed. It is proposed that these adhesion structures could be attached to a simplified version of the leg of a ladybird and used in practical applications. For example, the leg structures could potentially be employed in small surveillance drones to enable attachment to surfaces during flights, in order to preserve battery power. Alternatively, the structures could be used in small robotic devices to enable walking on steeply inclined surfaces. In this program of work, the morphology and movement of the leg of a ladybird were closely studied using a 3D X-ray microscope and a high-speed microscope. The positions of the tendons that facilitated movement were identified. From this knowledge, a simplified leg structure using pin-joints was designed and then fabricated using 3-D printing. The PDMS adhesion structures were then attached to the leg structure. The tendons in the actual insect leg were replicated using thread. Typical detachment forces of about 4 N indicated that the simplified leg structure was, in principle, more than capable of supporting the weight of a small device and then detach successfully. Attachment/detachment movement operations were performed using a linear actuator and controlled remotely. Therefore, proof of concept has been demonstrated for the use of such a simplified ladybird leg structure for the attachment/detachment of small robotic devices to horizontal, inclined, or vertical surfaces.

Binuclear Metal Phthalocyanines with Enhanced Activity in the Oxygen Evolution Reaction: A First-Principles Study.

The rational design of efficient catalysts for the electrochemical oxygen evolution reaction (OER) critically relies on a comprehensive understanding of the reaction mechanisms. Herein, the alkaline OER on planar mononuclear metal phthalocyanines (MPc, where M = Mn, Co, Fe, and Ni) and binuclear metal phthalocyanines (bi-MPc) is studied using density functional theory (DFT) methods. Both FePc and bi-CoPc exhibit enhanced stability and OER activity, with the energy required for the leaching of central metal being as high as 2.28 and 2.45 eV and the overpotentials of the OER being 0.48 and 0.57 V, respectively. Through electronic structure analysis, it is found that, in the OER process of bi-MPc, the large macrocyclic ligand and metal ions not bonding with the intermediate can serve as hole reservoirs. Intermediate species are further stabilized by the dispersal of a positive charge, reducing the free energy. These findings underscore the significance of macrocyclic ligands in the rate-determining step of the OER catalyst.

Crystal Structure Assignment for Unknown Compounds from X-ray Diffraction Patterns with Deep Learning.

Determining the structures of previously unseen compounds from experimental characterizations is a crucial part of materials science. It requires a step of searching for the structure type that conforms to the lattice of the unknown compound, which enables the pattern matching process for characterization data, such as X-ray diffraction (XRD) patterns. However, this procedure typically places a high demand on domain expertise, thus creating an obstacle for computer-driven automation. Here, we address this challenge by leveraging a deep-learning model composed of a union of convolutional residual neural networks. The accuracy of the model is demonstrated on a dataset of over 60,000 different compounds for 100 structure types, and additional categories can be integrated without the need to retrain the existing networks. We also unravel the operation of the deep-learning black box and highlight the way in which the resemblance between the unknown compound and a structure type is quantified based on both local and global characteristics in XRD patterns. This computational tool opens new avenues for automating structure analysis on materials unearthed in high-throughput experimentation.

Strong electron-phonon coupling and high lattice thermal conductivity in half-Heusler thermoelectric materials.

Traditional half-Heusler thermoelectric materials, identified as 18-electron compounds, are characterized by the high power factor and the high lattice thermal conductivity. Interestingly, the emerging 19-electron half-Heusler compounds were also found to be promising thermoelectric materials, but with a 5-10 times lower lattice thermal conductivity. Since the two kinds of compounds have similar chemical and physical structures, such as TiCoSb and VCoSb, the large difference in lattice thermal conductivity is a puzzling question. Here, we present a theoretical study to clarify the lattice thermal transport in half-Heusler thermoelectric materials. Based on electronic band structure analysis, we show that the two transition-metal elements in half-Heusler compounds form the strong and direct d-d interaction that is responsible for the high lattice thermal conductivity of 18-electron compounds. In 19-electron half-Heusler compounds, however, the extra valence electron enters the d-d antibonding states, which significantly weakens the atomic bond strength, leading to a large decrease in the cohesive energy. The resulting softened acoustic phonons enhance the phonon-phonon scattering, and thus reduce the lattice thermal conductivity significantly. By constructing an artificial 18-e compound V0.5Sc0.5CoSb, it is proved that the one less electron relative to VCoSb increases the lattice thermal conductivity significantly.

Association study of morpho-phenological traits in quinoa (Chenopodium quinoa Willd.) using SSR markers.

In this study, the genetic and molecular diversity of 60 quinoa accessions was assessed using agronomically important traits related to grain yield as well as microsatellite (SSR) markers, and informative markers linked to the studied traits were identified using association study. The results showed that most of the studied traits had a relatively high diversity, but grain saponin and protein content showed the highest diversity. High diversity was also observed in all SSR markers, but KAAT023, KAAT027, KAAT036, and KCAA014 showed the highest values for most of the diversity indices and can be introduced as the informative markers to assess genetic diversity in quinoa. Population structure analysis showed that the studied population probably includes two subclusters, so that out of 60 quinoa accessions, 29 (48%) and 23 (38%) accessions were assigned to the first and second subclusters, respectively, and eight (13%) accessions were considered as the mixed genotypes. The study of the population structure using Structure software showed two possible subgroups (K = 2) in the studied population and the results of the bar plot confirmed it. Association study using the general linear model (GLM) and mixed linear model (MLM) identified the number of 35 and 32 significant marker-trait associations (MTAs) for the first year (2019) and 37 and 35 significant MTAs for the second year (2020), respectively. Among the significant MTAs identified for different traits, the highest number of significant MTAs were obtained for grain yield and 1000-grain weight with six and five MTAs, respectively.

Spin-Flip via Subtle Electronic Perturbation in Axially Ligated Diiron(III) Porphyrin Dimer.

Spin state switching in the metal center is a crucial phenomenon in many enzymatic reactions in biology. The spin state alteration, a critical step in cytochrome P450 catalysis, is driven most likely through a weak perturbation upon substrate binding in the enzyme, which is still not well clarified. In the current work, the spin state transition of iron(III) from high to intermediate via an admixed state is observed upon a subtle electronic perturbation to the sulphonate moieties coordinated axially to a diiron(III)porphyrin dimer. While electron-donating substituents stabilize the high-spin state of iron(III), strongly electron-withdrawing groups stabilize an intermediate-spin state, whereas the moderate electron-withdrawing nature of axial ligands resulted in an admixed state. Confirmation of the molecular structures and their spin states have been made utilizing single-crystal X-ray structure analysis, Mössbauer, magnetic, EPR, and 1H NMR spectroscopic investigations. The position of the signals of the porphyrin macrocycle in the paramagnetic 1H NMR is found to be very characteristic of the spin state of the iron center in solution. The Curie plot for the pure high-spin complexes shows the signals' temperature dependency in line with the Curie law. Conversely, the pure intermediate-spin state of iron exhibits an anti-Curie temperature dependence, whereas the admixed-spin state of iron displays significant curvature of the lines in the Curie plot. An extensive DFT analysis displays a linear dependence between the energy difference between d and d orbital versus Fe-Npor distance for the complexes reported here. Furthermore, a strong linear correlation between the Fe-O distance and the spin density over the oxygen atom, as well as the Fe-Npor distance for the complexes, has been observed. Thus, a slight electronic perturbation at the axial ligand of the diheme resulted in a large change in the electronic structures with a spin-flip. This is at par with the metalloenzymes, which employ minute perturbations around the periphery of the active sites, leading to spin state transitions.

A twofold interpenetrated two-dimensional zinc(II) coordination polymer for the highly sensitive detection of nitrofurantoin in aqueous medium.

A novel ZnII coordination polymer, namely, poly[{μ2-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone-κ2N3:N3'}(μ2-5-bromobenzene-1,3-dicarboxylato-κ2O1:O3)zinc(II)], [Zn(C8H3BrO4)(C21H18N4O)]n or [Zn(Br-BDC)(MIPMO)]n, (I), has been synthesized by the solvothermal method using 5-bromoisophthalic acid (Br-H2BDC), bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone (MIPMO) and Zn(NO3)2·6H2O. Structure analysis showed that compound (I) displays twofold parallel interwoven sql nets. Fluorescence experiments confirmed that the compound can sensitively and selectively detect nitrofurantoin (NFT) in aqueous medium. In addition, the possible fluorescence quenching mechanisms of compound (I) toward NFT are investigated.