Unique Cation Research Articles

4-Iodoanilinium nitrate

In the title compound, C6H7IN+·NO3 −, π–π stacking inter­actions [centroid–centroid distances = 4.014 (4) and 4.029 (4) Å] stabilize the crystal structure and strong N—H⋯O and N—H⋯N hydrogen bonds link the cations and anions into zigzag chains running parallel to the c axis. The asymmetric unit contains two unique cations and anions

Differential stability of DNA crossovers in solution mediated by divalent cations

The assembly of DNA duplexes into higher-order structures plays a major role in many vital cellular functions such as recombination, chromatin packaging and gene regulation. However, little is currently known about the molecular structure and stability of direct DNA–DNA interactions that are required for such functions. In nature, DNA helices minimize electrostatic repulsion between double helices in several ways. Within crystals, B-DNA forms either right-handed crossovers by groove–backbone interaction or left-handed crossovers by groove–groove juxtaposition. We evaluated the stability of such crossovers at various ionic concentrations using large-scale atomistic molecular dynamics simulations. Our results show that right-handed DNA crossovers are thermodynamically stable in solution in the presence of divalent cations. Attractive forces at short-range stabilize such crossover structures with inter-axial separation of helices less than 20 Å. Right-handed crossovers, however, dissociate swiftly in the presence of monovalent ions only. Surprisingly, left-handed crossovers, assembled by sequence-independent juxtaposition of the helices, appear unstable even at the highest concentration of Mg2+studied here. Our study provides new molecular insights into chiral association of DNA duplexes and highlights the unique role divalent cations play in differential stabilization of crossover structures. These results may serve as a rational basis to understand the role DNA crossovers play in biological processes.

Investigation of the Effect of Functional Group Substitutions on the Gas-Phase Electron Affinities and Ionization Energies of Room-Temperature Ionic Liquids Ions using Density Functional Theory

The cathodic and anodic stabilities of room-temperature ionic liquids (ILs) are important factors in their applications in electrochemical devices. In this work, we investigated the electron affinities of cations and ionization energies of anions for ionic liquids by density functional theory (DFT) calculations at the B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d) level. Over 200 unique cations and anions, formed from a set of six base cation structures, three base anion structures, and seven functional groups, were investigated. We find the trends in calculated EAs of alkylated cations and IEs of alkylated anions to be in good agreement with observed experimental trends in relative cathodic and anodic stabilities of various ILs. In addition, we also investigated the effect that functional group substitution at distinct positions in the ions have on the EA of the 1,2,3-trimethylimidazolium cation and the IE of the PF 5CF 3 anion. The overall impact on the EA or IE can be explained by the known electron-donating and electron-withdrawing inductive and resonance effects of the attached functional group, and the relative strength of the effect depends on the substitution position.

1-(2-Fluorobenzylideneamino)pyridinium bis(1,2-dicyanoethene-1,2-dithiolato)nickelate(II)

In the title complex, (C12H10FN2)2[Ni(C4N2S2)2], the anion lies on an inversion center with the NiII ion coordinated by four S atoms in a slightly distorted square-planar environment. In the unique cation, the dihedral angle between the benzene and pyridine rings is 7.1 (2) Å.

The crucial role of C—H...O and C=O...π interactions in the building of three-dimensional structures of dicarboxylic acid–biimidazole compounds

The supramolecular architectures of three dicarboxylic acid-biimidazole compounds, namely, 2,2'-biimidazolium malonate, C(6)H(8)N(4)(2+).C(3)H(2)O(4)(2-), (I), 2,2'-bi(1H-imidazole) succinic acid, C(6)H(6)N(4).C(4)H(6)O(4), (II), and 2,2'-biimidazolium 2,2'-iminiodiacetate chloride, C(6)H(8)N(4)(2+).C(4)H(6)NO(4)(-).Cl(-), (III), are reported. The crystal structures are assembled by the same process, namely double conventional N-H...O or O-H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair-aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C-H...O interactions. The C=O...pi interactions involved in stacking the tapes in (II) and the C-H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively.

Effects of the application of natural zeolite on the growth and nutrient status of radish (Raphanus sativus L.)

SummaryThe unique cation exchange, adsorption, hydration-dehydration, and catalytic properties of natural zeolites, and their abundance, have promoted their use in agriculture as soil amendments and slow-release fertilisers. This research was conducted to investigate the effects of natural Iranian zeolite on vegetative growth and the nutrient status of radish (Raphanus sativus L. cv. Cherry Belle). The experiment was performed as a completely randomised design with six treatments (0, 20, 40, 60, 80, or 100 g zeolite kg−1 soil) and four replicates. The results indicated that zeolite increased leaf number and leaf area, shoot fresh weight (FW), the diameter and FW of edible roots, the number, length and FW of fibrous roots, and harvest index. The use of zeolite also increased the concentrations of nitrogen (N) and potassium (K) in shoot tissues, and the cation-exchange capacity of the medium. It was concluded that zeolite had a pronounced positive effect on vegetative growth in radish. Zeolite may be recommended as a soil amendment for vegetable crops such as radish to decrease nutrient leaching.

A unique and novel cyclopropylmethyl cation intermediate: a DFT study

Some physical organic aspects of the intermediates that result from the interaction between phenylmethylenecyclopropane (substituted derivatives are important in synthesizing cyclobutenes) and platinum and palladium halides have been studied using B3LYP. Geometrical aspects, values of atom polarizable tensor charges (APT), effect of substituents, selected transition states activation barriers, and molecular orbital calculations are presented. These calculations suggest a novel organometallic cyclopropylmethyl cation, which is characterized by the presence of a highly polarized and unusually long sigma bond between the benzylic carbon and coordinating halogen atom.

Site Solution Preference of $\hbox {Bi}^{3+}$ in $\hbox {RE}_{2}\hbox {O}_{3}$ Scintillators

Atomic-scale simulations have been employed to predict the site solution preference of Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> activator cations in a series of RE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> scintillators with the bixbyite crystal structure (Ialpha3), where RE denotes a 3+ cation ranging in size from Sc <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> to La <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> . There are two crystallographically unique cation sites in the bixbyite structure, in Wyckoff notation referred to as the 24d and 8b site. It is expected that the spectroscopic properties of an activator cation residing on the 24d site will be different from the same activator cation residing on the 8b site, due to the distinct symmetries (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> respectively) of these two sites. Previous studies have revealed two different Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> emissions in Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> corresponding to Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> cations occupying both lattice 24d and 8b sites. By predicting the energy difference of the Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> solution on the 24d and 8b sites, we are able to predict the distribution of Bi <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> in a range of bixbyite compounds.

Di-μ-methacrylato-bis[diaquabis(methacrylato)europium(III)] methacrylic acid disolvate

In the title centrosymmetric complex, [Eu2(C4H5O2)6(H2O)4]·2C4H6O2, the unique EuIII cation is coordinated by seven carb­oxylate O atoms from four methacrylate ligands and two water mol­ecules in a slightly disorted tricapped trigonal–prismatic environment. Two EuIII ions are bridged by carboxyl­ate groups, forming a dinuclear complex. The formula unit also contains two mol­ecules of methacrylic acid. In the crystal structure, mol­ecules are linked via inter­molecular O—H⋯O hydrogen bonds, forming one-dimensional chains propagating along the b-axis direction

Determining the site preference of trivalent dopants in bixbyite sesquioxides by atomic-scale simulations

Oxides with the bixbyite structure $(Ia\overline{3})$ have two crystallographically unique cation sites, namely (in Wyckoff notation) $24d$ and $8b$. Since the symmetries of these two sites are different (${C}_{2}$ and ${S}_{6}$, respectively), properties related to solute cations will vary depending on the site preference. Therefore, we have employed atomic scale simulation techniques to systematically investigate the solution site preference of a range of trivalent cations ranging from ${\mathrm{Sc}}^{3+}$ to ${\mathrm{La}}^{3+}$ in ${A}_{2}{\mathrm{O}}_{3}$ bixbyite oxides (where $A$ ranges from Sc to La). Results reveal that when the solute cation is smaller than the host lattice cation, the $24d$ site is energetically favorable, but when the solute cation is larger than the host lattice cation, the $8b$ site is preferred. We also discuss the tendency for solute cations to cluster, as well as corroboration of this work by first principles methods.

Expression of CatSper family transcripts in the mouse testis during post-natal development and human ejaculated spermatozoa: relationship to sperm motility

CatSper is a unique sperm cation channel-like protein family exclusively expressed in the testis and plays important roles in sperm functions. The temporal expression profiles of CatSper1-4 mRNAs in the mouse testis during post-natal development through adulthood were investigated using real-time RT-PCR. The CatSper2 transcript was present in the testis of the 8-day-old mice, and was repressed in the adult testis after two sharp up-regulations at day 18 and 35. CatSper1 and CatSper3, 4 mRNAs were detectable in the testis of 18-day and 15-day-old mice, respectively. After sharp up-regulation at day 25 and 35, respectively, they were maximal at the adult testis stage. The differences between the temporal expression profiles of the CatSper transcripts in post-natal mouse testis development suggest different regulation to their transcription, and potentially contribute to the possibility of forming heteromeric channels among these four CatSper family members. CatSper1-3 transcripts were identified to be present in the human ejaculated spermatozoa by RT-PCR. Significantly higher levels of CatSper2 and CatSper3 mRNAs revealed by real-time RT-PCR were observed in the high-motile spermatozoa than in the low-motile fraction and suggests that CatSper2 and CatSper3 transcripts in the human ejaculated spermatozoa could be the potential targets for further study and male infertility screening.

Bis[4-(4-hydroxystyryl)-1-methylpyridinium] triiodide iodide

In the title compound, 2C14H14NO+·I3−·I−, the cations are almost planar and exist in E configurations. The dihedral angles between the pyridinium and benzene rings in the two unique cations are 2.6 (2) and 2.8 (2)°. O—H⋯I hydrogen bonds and weak C—H⋯I inter­actions are observed in the crystal structure. The cations are arranged in a zigzag fashion along the c axis and are packed in an anti­parallel manner into sheets parallel to the bc plane. These sheets are inter­connected via O—H⋯I hydrogen bonds and weak C—H⋯I inter­actions to form a three-dimensional network.

Effects of Zeolite Application on Rice Yield, Nitrogen Recovery, and Nitrogen Use Efficiency

The unique cation exchange, adsorption, hydration–dehydration, and catalytic properties of natural zeolites and their abundance have promoted their use in a wide variety of agricultural processes as soil amendments, slow‐release fertilizers, and other materials. To investigate the feasibility of using a natural clinoptilolite to enhance rice grain yield, nitrogen (N) recovery and N use efficiency, an experiment was conducted in a coarse‐textured rice field in the Guilan province of Iran. Three levels of 8, 16, or 24 tons of zeolite ha−1 were incorporated into the soil with and without 60 kg N ha−1 as urea, and their effects on the grain and straw yields, available K, apparent N recovery, N use efficiency, and some soil properties were determined. Results indicated a significant positive effect of treatments on the grain yield, straw, and tiller numbers of rice. All levels of zeolite with N showed a significant increase in grain yield compared with 60 kg N ha−1 and control treatment. Zeolite application also increased soil‐available potassium and its uptake by rice straw significantly. The lowest apparent N recovery (40%) was obtained from application of 60 kg N ha−1, whereas application of 8 or 16 tons zeolite ha−1 increased apparent N recovery up to 65%. Nitrogen use efficiency was also improved.

Functional organization of TRPC-Ca 2+ channels and regulation of calcium microdomains

TRP family of proteins are components of unique cation channels that are activated in response to diverse stimuli ranging from growth factor and neurotransmitter stimulation of plasma membrane receptors to a variety of chemical and sensory signals. This review will focus on members of the TRPC sub-family (TRPC1–TRPC7) which currently appear to be the strongest candidates for the enigmatic Ca 2+ influx channels that are activated in response to stimulation of plasma membrane receptors which result in phosphatidyl inositol-(4,5)-bisphosphate (PIP 2) hydrolysis, generation of IP 3 and DAG, and IP 3-induced Ca 2+ release from the intracellular Ca 2+ store via inositol trisphosphate receptor (IP 3R). Homomeric or selective heteromeric interactions between TRPC monomers generate distinct channels that contribute to store-operated as well as store-independent Ca 2+ entry mechanisms. The former is regulated by the emptying/refilling of internal Ca 2+ store(s) while the latter depends on PIP 2 hydrolysis (due to changes in PIP 2 per se or an increase in diacylglycerol, DAG). Although the exact physiological function of TRPC channels and how they are regulated has not yet been conclusively established, it is clear that a variety of cellular functions are controlled by Ca 2+ entry via these channels. Thus, it is critical to understand how cells coordinate the regulation of diverse TRPC channels to elicit specific physiological functions. It is now well established that segregation of TRPC channels mediated by interactions with signaling and scaffolding proteins, determines their localization and regulation in functionally distinct cellular domains. Furthermore, both protein and lipid components of intracellular and plasma membranes contribute to the organization of these microdomains. Such organization serves as a platform for the generation of spatially and temporally dictated [Ca 2+] i signals which are critical for precise control of downstream cellular functions.

K‐Site Splitting in KTiOPO4 at Room Temperature.

AbstractFor Abstract see ChemInform Abstract in Full Text.

K-site splitting in KTiOPO4at room temperature

The room-temperature structure of potassium titanyl phosphate (KTiOPO4, KTP) with Pna2(1) symmetry has been studied by means of synchrotron radiation. Each of the two crystallographically unique K1 and K2 cations is split over two sites that are shifted along the c direction by 0.287 (13) and 0.255 (13) A for the K1a/b and K2a/b pairs, respectively. The refined populations of the minor K1b and K2b sites are 0.102 (12) and 0.132 (17), respectively. It is shown that accurate high-resolution synchrotron data (Rmerged = 0.015 for 25 010 reflections, 9456 unique, sintheta/lambda limit > 1.0) are required for the determination of a reliable structure model.

Facilitated ion transfer reactions across oil∣water interfaces based on different competitive ligands

In this paper, we present the general equations for facilitated ion transfer reactions across oil∣water interfaces based on different competitive ligands, i.e., the transfer of a cation that, under given conditions, is assisted by a mechanism that involves ligands exchange. The obtained results agree with the general voltammetric criteria reported by Girault and co-workers [F. Reymond, P.-A. Carrupt, H.H. Girault, J. Electroanal. Chem. 449 (1998) 49; F. Reymond, G. Lagger, P.-A. Carrupt, H.H. Girault, J. Electroanal. Chem. 451 (1998) 59] for the facilitated transfer of a unique cation assisted by a neutral ligand. The equations reported in this paper grant to simulate the system under all possible conditions. The results are interpreted for different zones determined by the ratio of cation and ligand concentrations.

Systematic study of grain boundary atomistic structures and related properties in cubic zirconia bicrystals

Abstract Systematic grain boundary study of cubic zirconia has been conducted by using bicrystals. It is clearly demonstrated that grain boundary atomistic structures dramatically change according to the misorientations and plane orientations of the boundaries, resulting in a dramatic change of excess energies and solute segregation behaviors. Combining with theoretical calculations, it is found that grain boundaries possess unique coordination-deficient cation sites at the cores, and their densities have a clear correlation with these properties in high-angle grain boundaries. This result indicates that grain boundary properties in ceramics are possibly determined by the accumulation of coordination-deficient sites. Thus, systematic grain boundary study using bicrystal offers fundamental understandings of the relationship between atomistic structures and properties in ceramic grain boundaries.

1,3-Diethylbenzimidazolium iodide

The title salt, C11H15N2+·I−, crystallizes with two formula units in the asymmetric unit. The two crystallographically unique cations form alternating columns along the a axis, linked by protruding ethyl groups and interspersed with iodide counter-ions. Cations in a given column stack in centrosymmetrically related pairs with interionic C⋯C and C⋯N distances consistent with substantial π–π bonding. One of the iodide ions appears to form a weak hydrogen bond with the most acidic proton in one of the cations.

Dinicotinamidium squarate.

The crystal structure determination of the dinicotinamidium squarate salt, 2C(6)H(7)N(2)O(+).C(4)O(4)(2-), is reported, with the squarate dianion residing on an inversion centre and the unique cation in a general position. Salt formation occurs by donation of two H atoms from squaric acid to the nicotinamide base. The crystal packing is derived from three types of hydrogen bonding. The primary hydrogen bond involves a squarate anion O atom and an H atom of the protonated pyridine group of the nicotinamide, with an N.O distance of 2.5760 (13) A. The second hydrogen bond involves a second anion O atom and an amide H atom, with an N.O distance of 2.8374 (14) A. Thirdly, an intermolecular interaction between two coplanar nicotinamide moieties occurs between an amide O atom and a symmetry-related amide H atom, with an N1.O3 distance of 2.8911 (15) A. These hydrogen bonds are also responsible for the planarity of the nicotinamide moiety in the salt.