Complex R1 Research Articles

Supramolecular Spring-Like Fe(II) Spin-Crossover Complexes Experiencing Giant and Anisotropic Thermal Expansion Across Two Distinct Temperature Regimes.

Dynamic molecules with tunable chemical and physical properties in response to external stimuli hold great potential for applications in information storage, smart molecular machines, and biomimetics. Among them, supramolecular springs and spin-crossover (SCO) complexes can both undergo visible macroscopic changes under heat or light stimulation. In this study, we synthesized a trinuclear Fe(II)-SCO complex, [(R-L)FeII{Au(CN)2}2] (R1), using a chiral chelating ligand decorated with rotatable benzyl rings. The [FeAu2] trinuclear molecules form a 21-helical supramolecular chain via elastic Au∙∙∙Au contacts. Interestingly, the synergy between the multiple dynamic factors (SCO event, rotation of the rings, and flexibility in Au∙∙∙Au distance) endows the complex with multiple switchings in both magnetism and structure, as well as the most intriguing characteristic of giant and anisotropic "breathing" feature in thermal expansion within two distinct temperature regimes. Specifically, complex R1 undergoes two hysteretic magnetic transitions: a non-spin transition and an unsymmetric SCO transition. Both transitions are triggered/accompanied by the rotation of the benzyl rings. Correspondingly, reversible spring-like motions of the helical chains are observed in the two distinct temperature regimes. This work demonstrates a significant success in incorporating both SCO and spring-like motion in one system, paving the way for designing multifunctional dynamic materials for future devices.

Supramolecular Spring‐Like Fe(II) Spin‐Crossover Complexes Experiencing Giant and Anisotropic Thermal Expansion Across Two Distinct Temperature Regimes

Dynamic molecules with tunable chemical and physical properties in response to external stimuli hold great potential for applications in information storage, smart molecular machines, and biomimetics. Among them, supramolecular springs and spin‐crossover (SCO) complexes can both undergo visible macroscopic changes under heat or light stimulation. In this study, we synthesized a trinuclear Fe(II)‐SCO complex, [(R‐L)FeII{Au(CN)2}2] (R1), using a chiral chelating ligand decorated with rotatable benzyl rings. The [FeAu2] trinuclear molecules form a 21‐helical supramolecular chain via elastic Au∙∙∙Au contacts. Interestingly, the synergy between the multiple dynamic factors (SCO event, rotation of the rings, and flexibility in Au∙∙∙Au distance) endows the complex with multiple switchings in both magnetism and structure, as well as the most intriguing characteristic of giant and anisotropic “breathing” feature in thermal expansion within two distinct temperature regimes. Specifically, complex R1 undergoes two hysteretic magnetic transitions: a non‐spin transition and an unsymmetric SCO transition. Both transitions are triggered/accompanied by the rotation of the benzyl rings. Correspondingly, reversible spring‐like motions of the helical chains are observed in the two distinct temperature regimes. This work demonstrates a significant success in incorporating both SCO and spring‐like motion in one system, paving the way for designing multifunctional dynamic materials for future devices.

A sensing approach based on rhodamine associated Bis-1,2,3-triazole probe for targeted recognition of Fe3+ ions: Imaging on DL-tumor cells and molecular modelling

The discriminatory identification of Fe3+ ions among the series of metal ions in an aqueous medium is a significant importance of chemosensors, a bis-1,2,3-triazole associated with rhodamine (R1) was developed with a perfect hetero-atomic cavity. The chemosensor R1 was synthesized using a simple and well-known click reaction to generate a nitrogen enrich triazoles unit in the R1. Through the naked eyes, Fe3+ ion was detected on the spot at tremendously low concentrations with the alterations of fluorescent from non-fluorescent and colored from colorless R1. After formation of complex R1:Fe3+, it is highly pH sustained range from pH 2.0–10.0 and reversible with cysteine in solution and on a paper strip. The formed complex R1:Fe3+, it exhibits excellent pH stability within the range of pH 2.0–10.0. Moreover, its reversibility can be achieved through interaction with cysteine, both in solution and on a paper strip. R1 was also feasible to detect Fe3+ ions in real water samples. In DL-tumor cells, cytocompatibility was investigated using MTT assay, and found that cell viability was greater than 80 %. The binding interaction of R1 with the crystal structure of the anti-apoptotic protein Bcl-XL (PDB ID: 2YXJ) showed that R1 fits well at the active site of Bcl-XL with binding energy (ΔG) − 10.42 kcal/mol (Ki = 22.97 nM). The result shows that R1 is cytocompatible and may be exploited as a fluorescent probe for selectively detecting Fe3+ in living cells.

Fluorine and Nitrogen Co-Doped Carbon Dot Complexation with Fe(III) as a T1 Contrast Agent for Magnetic Resonance Imaging.

Commercial gadolinium-based materials have been widely used as contrast agents for magnetic resonance imaging (MRI), but the high toxicity of leaking free Gd3+ ions still raises biosafety concerns. Here, we develop a novel, safe, and efficient MRI contrast agent based on a stable Fe(III) complex of fluorine and nitrogen co-doped carbon dots (F,N-CDs) that was prepared from glucose and levofloxacin by a simple microwave-assisted thermal decomposition method. The obtained Fe3+@F,N-CD complex exhibits higher longitudinal relaxivity ( r1 = 5.79 mM-1·s-1) than that of the control samples of the Fe3+@CD complex ( r1 = 4.23 mM-1 s-1) and free Fe3+ ( r1 = 1.59 mM-1 s-1) in aqueous solution, as assessed by a 1.5 T NMR analyzer. More importantly, the Fe3+@F,N-CD complex is very stable with a large coordination constant of 1.06 × 107 in aqueous medium. While incubated with HeLa cells, the Fe3+@F,N-CD complex shows clear MR images, demonstrating that it has potential to be an excellent MRI contrast agent. Furthermore, in vivo MRI experiments indicate that the Fe3+@F,N-CD complex provides high-resolution MRI pictures of 4T1 tumor bearing BALB/c mice 15 min after injection and can be completely excreted 2 h after administration. No cytotoxicity was observed with F,N-CDs and Fe concentration up to 0.2 mg/mL and 0.3 mM in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assay, respectively. The possible mechanism of the enhanced MRI effect of the Fe3+@F,N-CD complex is therefore proposed. The extremely low toxicity, high r1 relaxivity, strong photoluminescence, and low synthetic cost enable the Fe3+@F,N-CD complex to be a safe and promising T1-weighted MRI contrast agent for clinical applications.

ATP Induced Modulation in π–π Stacking Interactions in Pyrene Based Zinc Complexes: Chemosensor Study and Quantitative Investigation of Apyrase Activity

Fluorescent zinc complexes of 1,2-disubstituted benzimidazole (R1–R3) have been synthesized and characterized using single crystal X-ray diffraction. The ligands L1–3 were found to be less emissive due to photoinduced electron transfer (PET) mechanism originated from the electron pair of benzimidazole nitrogen. The complexation of ligands with Zn(II) not only enhances the fluorescent intensity; it also orients the ligands to a new packing. It was observed that the aromatic unit plays a decisive role in the packing of the molecules. The complex R1 has extended the coordination through C–H···π interaction, whereas complex R2 involved C–H···π interaction and C–H···Br interaction for packing in supramolecular architecture. Among these complexes, R3 showed the most interesting noncovalent interaction pattern involving C–H···π interaction, C–H···Br interaction, and π–π stacking between pyrene rings. These noncovalent interactions govern photophysical properties that are sensitive toward the microenvironment. Thus, by altering these interactions, the selective sensing for a particular analyte can be achieved. The complexes R1 and R2 have shown enhanced emission intensity upon interacting with adenosine triphosphate (ATP) competitively in the presence of some other tested anions. A ratiometric change in emission spectra of the complex R3 was observed upon binding with ATP in semiaqueous medium offering the lowest detection limit of 15 nM. Upon interaction with ATP, the π–π stacking between pyrene rings breaks and results in a decrease in excimer emission at 470 nm and increases in monomeric emission intensity at 410 nm. The AFM (Atomic force microscopy) images of receptor R3 show that upon addition of ATP to the R3 solution, solvent mediated aggregation takes place, which results in the ratiometric detection. In the dimethylformamide solvent system, aggregates were formed, whereas in a water/tetrahydrofuran solvent system the clear solution was converted to a highly viscous gel. To investigate the applications of the prepared sensor, the fluorescence response of HeLa cells enriched with ATP was observed using fluorescence microscopy. The fluorescence modulation of the sensor in living cells makes the receptor practically applicable in a biological environment. Quantitative analysis of apyrase activity has shown that the presented sensor R3 is capable of monitoring the hydrolysis process in the biological system.

A 2-mercaptobenzimidazole-based emissive Cu(I) complex for selective determination of iodide with large Stokes shift

A Cu(I) complex of 2-mercaptobenzimidazole (R1) was synthesized and characterized using single-crystal X-ray diffraction. Complex R1 showing strong emission at 598nm serves as a sensor for iodide determination. Upon addition of iodide to a solution of complex R1, a reduction in emission intensity by aggregation-caused quenching (ACQ) was observed, with a large Stokes shift. The limit of detection (LOD) of complex R1 was estimated to be 14±1.5nM. Complex R1 proved to be reusable by extracting the iodide ions with silver nitrate. The advantages of using complex R1 as a sensor for iodide include low LOD and emission at long wavelengths, which eliminate the interference caused by short-wavelength emissive impurities.

A benzimidazolium-based mixed organic–inorganic polymer of Cu(II) ions for highly selective sensing of phosphates in water: applications for detection of harmful organophosphates

We synthesized a dinuclear Cu(II) paddle-wheel complex R1 containing a benzimidazolium ligand and explored using it as a fluorescence turn-ON sensor for detecting phosphates in water. The sensor exhibited both fluorescence and electrochemical responses to phosphates with high selectivity and sensitivity over other anions, which makes it useful for the detection of harmful organophosphates.

A Cu(II) complex of an imidazolium-based ionic liquid: synthesis, X-ray structure and application in the selective electrochemical sensing of guanine.

An imidazolium-based ionic liquid containing a carboxylic acid group was synthesized and complexed with Cu(II). The resulting complex R1 was fully characterized using various techniques, including IR spectroscopy and X-ray crystallography. Binding studies of the complex R1 were performed with anions and biomolecules using cyclic voltammetry, which showed no change in its voltammogram upon the addition of various anions and most biomolecules. However, a shift in the reduction peak from +0.20 to -0.15 was observed upon the addition of guanine. This selective determination of guanine by R1 was extended by using R1 as an electrochemical sensor for guanine in various voltammetric techniques, including cyclic voltammetry, LSV and DPV. The proposed sensor showed excellent reproducibility and high selectivity and sensitivity towards guanine, with a linear range of 0-20 μM and a detection limit of 45 nM.

Enantiomeric Specificity of Biologically Significant Cu(II) and Zn(II) Chromone Complexes Towards DNA

Novel chiral Schiff base ligands (R)/(S)-2-amino-3-(((1-hydroxypropan-2-yl)imino)methyl)-4H-chromen-4-one (L(1) and L(2)) derived from 2-amino-3-formylchromone and (R/S)-2-amino-1-propanol and their Cu(II)/Zn(II) complexes (R1, S1, R2, and S2) were synthesized. The complexes were characterized by elemental analysis, infrared (IR), hydrogen ((1) H) and carbon ((13)C) nuclear magnetic resonance (NMR), electrospray ionization-mass spectra (ESI-MS), and molar conductance measurements. The DNA binding studies of the complexes with calf thymus were carried out by employing different biophysical methods and molecular docking studies that revealed that complexes R1 and S1 prefers the guanine-cytosine-rich region, whereas R2 and prefers the adenine-thymine residues in the major groove of DNA. The relative trend in K(b) values followed the order R1>S1>R2>S2. This observation together with the findings of circular dichroic and fluorescence studies revealed maximal potential of (R)-enantiomeric form of complexes to bind DNA. Furthermore, the absorption studies with mononucleotides were also monitored to examine the base-specific interactions of the complexes that revealed a higher propensity of Cu(II) complexes for guanosine-5'-monophosphate disodium salt, whereas Zn(II) complexes preferentially bind to thymidine-5'-monophosphate disodium salt. The cleavage activity of R1 and R2 with pBR322 plasmid DNA was examined by gel electrophoresis that revealed that they are good DNA cleavage agents; nevertheless, R1 proved to show better DNA cleavage ability. Topoisomerase II inhibitory activity of complex R1 revealed that the complex inhibits topoisomerase II catalytic activity at a very low concentration (25 μM). Furthermore, in vitro antitumor activity of complexes R1 and S1 were screened against human carcinoma cell lines of different histological origin.

Experimental and Theoretical Study of a Tungsten Dihydride Silyl Complex: New Insight into Its Bonding Nature and Fluxional Behavior

Tungsten dihydride silyl complex Cp*(CO)2W(H)2[SiH(OMe){C(SiMe3)3}] (R1) was synthesized by the reaction of silylene complex Cp*(CO)2(H)W═Si(H){C(SiMe3)3} (R2) with MeOH. Complex R1 was characterized by spectroscopic data as well as elemental analysis, and its geometry was supported by X-ray crystallography. Interestingly, the variable-temperature 1H NMR spectroscopy revealed that R1 shows highly fluxional behavior, in which two diastereotopic hydrides rapidly exchange their positions in the NMR time scale. The DFT-optimized geometry of Cp(CO)2W(H)2[SiH(OMe){C(SiH3)3}] (1a), which was employed as a model of R1, indicates the presence of a W−silyl and two W−hydride bonds in addition to two weak Si---H interactions. Based on the analyses of molecular orbitals and electron populations, a theoretical understanding of 1a is presented, as follows: (i) 1a is neither a pure dihydride silyl complex of W(IV) bearing d2 electron configuration nor a pure silicate complex of W(II) bearing d4 electron configuration, (i...

The Effects of IL-20 Subfamily Cytokines on Reconstituted Human Epidermis Suggest Potential Roles in Cutaneous Innate Defense and Pathogenic Adaptive Immunity in Psoriasis

IL-19, IL-20, IL-22, IL-24, and IL-26 are members of the IL-10 family of cytokines that have been shown to be up-regulated in psoriatic skin. Contrary to IL-10, these cytokines signal using receptor complex R1 subunits that are preferentially expressed on cells of epithelial origin; thus, we henceforth refer to them as the IL-20 subfamily cytokines. In this study, we show that primary human keratinocytes (KCs) express receptors for these cytokines and that IL-19, IL-20, IL-22, and IL-24 induce acanthosis in reconstituted human epidermis (RHE) in a dose-dependent manner. These cytokines also induce expression of the psoriasis-associated protein S100A7 and keratin 16 in RHE and cause persistent activation of Stat3 with nuclear localization. IL-22 had the most pronounced effects on KC proliferation and on the differentiation of KCs in RHE, inducing a decrease in the granular cell layer (hypogranulosis). Furthermore, gene expression analysis performed on cultured RHE treated with these cytokines showed that IL-19, IL-20, IL-22, and IL-24 regulate many of these same genes to variable degrees, inducing a gene expression profile consistent with inflammatory responses, wound healing re-epithelialization, and altered differentiation. Many of these genes have also been found to be up-regulated in psoriatic skin, including several chemokines, beta-defensins, S100 family proteins, and kallikreins. These results confirm that IL-20 subfamily cytokines are important regulators of epidermal KC biology with potentially pivotal roles in the immunopathology of psoriasis.

Pl-bol3, a complex allele of the anthocyanin regulatory pl1 locus that arose in a naturally occurring maize population.

The pl1 gene encodes a MYB-related transcriptional activator committed to the regulation of anthocyanin biosynthesis in maize. Here, we report the genetic and molecular characterisation of pl-bol3, an Andean allele displaying features that make it different from all the known pl1 alleles. pl-bol3 has partial, light-independent expression, and it is active mainly in the juvenile phase of growth. It has a complex molecular structure, containing multiple pl1 gene copies, thus being the first complex locus discovered in the c1/pl1 family. Although the composite genes of the complex locus encode proteins identical to other functional PL1 proteins, the putative promoters of the pl-bol3 gene are different from the promoters of Pl-Rhoades (Pl-Rh) and pl1 sun-red alleles. The intensity and the tissue specificity of anthocyanin production directed by pl-bol3 differ significantly from that of Pl-Rh and the original pl-W22, and are specified by the interaction of pl-bol3 with the different r1/b1 gene family members and the competence of pl-bol3 to different pigment tissues. This allele represents a natural example of gene duplication and diversification of expression, giving rise to a significant change in phenotype and, in this way, is analogous to the complex r1 locus in maize. Analysis of the pl-bol3 allele contributes to understanding the generation of diversity associated with multiple-copy genes and the molecular basis of allele-specific gene expression.

Synthesis and characterization of methyl methacrylate/styrene hyperbranched copolymers via living radical mechanism

Free-radical copolymerizations of N,N-diethylaminodithiocarbamoylmethylstyrene (inimer: DTCS) with a methyl methacrylate (MMA)/zinc chloride (ZnCl2) complex were carried out under UV light irradiation. DTCS monomers play an important role in this copolymerization system as an inimer that is capable of initiating living radical polymerization of the vinyl group. The reactivity ratios (r1 = 0.56 and r2 = 0.52: DTCS [M1]; MMA [M2]) obtained for this copolymerization system were different from a corresponding model system (alternating copolymer) of a styrene and MMA/ZnCl2 complex (r1 = 0.25 and r2 = 0.056). It was found that the hyperbranched copolymers produced exhibited a random branching structure. It was found that the Lewis acid ZnCl2 formed the complex not only with MMA but also with the carbamate group of inimer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2490–2495, 2003

Evidence of local structural transition during oxidation process of RBCO epitaxial films using time resolved reflexafs measurements

We report results of a time resolved X-ray Absorption Spectroscopy (XAS) experiment on the oxidation process of epitaxial Y1(Nd0.05Ba1.95)Cu3Ox superconducting thin films. For the first time Cu K-edge XAS technique has been used to explore local structural changes around the Cu ions during the oxidation process of a high critical temperature superconducting film. The results show that during the oxygenation of a tetragonal Y1(Nd0.05Ba1.95)Cu3Ox additional local transitions appear in the orthorhombic I phase, which are not linked to long range order transformations as shown by in situ X-ray diffraction experiment. New questions concerning the dynamic microscopic process leading to the oxygenation and eventually to superconductivity of the complex R1+xBa2-xCu3Ox (R = Y or rare earth) compounds arose from these results.

Distribution of ABO and Rhesus Blood Groups in G6PD Deficient Chinese and Malay Newborns

The distribution of ABO blood groups was studied in 459 Chinese and 65 Malay newborns with deficiency of G6PD, and in 1181 Chinese and 535 Malay newborns with normal levels of the enzyme. Similarly, the distribution of Rhesus blood groups was studied in 248 G6PD deficient Chinese newborns and in 255 normal subjects. No association between the ABO blood groups and G6PD deficiency was observed in either Chinese or Malays. For the Rhesus system there was found to be a statistically significant decrease in the frequency of genotypes containing the complex R1, in G6PD deficient subjects compared with that in normal subjects.

Geometric groups and Whitehead torsion

The purpose of this paper is to define geometric and to relate them to various problems in topology. This relation is exhibited through Conjectures I and II. It will be shown that Conjecture I implies Conjecture II and that Conjecture II implies the topological invariance of Whitehead torsion. Conjecture II is true for 2-complexes, and this implies that if K and N are finite connected complexes, L' K is a subcomplex with dim L $2, and f: K -> N is a homeomorphism with f IK-L p.w.l., then f is a simple homotopy equivalence. Another corollary is that if K is a 2-complex contained in a p.w.l. manifold Mn, Un is a compact p.w.l. submanifold, K' U' M, and U e-deforms to K, then KG U is a simple homotopy equivalence and, thus, if n > 65 U is a regular neighborhood of K. Finally, for any finitely presented group with Wh (-a) #0, ] an h-cobordism W with -a (W) = which is not topologically trivial. Geometric groups are related to other problems in topology and some of these are mentioned without proof in the appendix. For example, Conjecture I implies that compact ANRs of finite dimension have the homotopy type of finite complexes. Conjecture II has a noncompact analogue and since the difficulties are local, there is essentially nothing new here (Conjecture II is true for infinite 2-complexes). This noncompact form of Conjecture 11 implies the following: If f: Rn -> Rn is a homeomorphism (n >5) such that fx Id: Rn x Rk Rn x Rk is stable, then f is stable. The final note of the appendix implies the following: Suppose (ai,j) is an infinite matrix with integer entries, and that it and its inverse are band matrices, i.e., bounded about the diagonal. Then (ai,j) can be diagonalized by row operations. This is a nongeometric analogue of Conjecture II for the infinite complex R1.