Displaying publications 1 - 20 of 167 in total

  1. Razak IA, Usman A, Fun HK, Yamin BM, Kasim NA
    Acta Crystallogr C, 2002 Apr;58(Pt 4):M225-7.
    PMID: 11932524
    In the title compound, [Fe(C(34)H(29)O(2)P(2))](2)[Sb(2)Cl(8)], the discrete centrosymmetric [Sb(2)Cl(8)]2- anions are formed from two edge-shared square pyramids of Cl atoms about each Sb atom. Within the cation, the two diphenylphosphinate groups share one H atom and the ferrocene cyclopentadienyl rings are in a staggered conformation, with the average value of the twist angle being 46 degrees. In the crystal, each [Sb(2)Cl(8)]2- anion is involved in eight C-H* * *Cl interactions with four surrounding cations and these interactions interconnect the ions to form molecular columns along the a direction.
    Matched MeSH terms: Cations
  2. Bashir MJ, Aziz HA, Yusoff MS
    J Hazard Mater, 2011 Feb 15;186(1):92-102.
    PMID: 21146925 DOI: 10.1016/j.jhazmat.2010.10.082
    Two new applications for sequence treatment of mature (stabilized) landfill leachate, that is, cationic resin followed by anionic resin (cationic/anionic) and anionic resin followed by cationic resin (anionic/cationic), are employed and documented for the first time in the literature. Response surface methodology (RSM) concerning central composite design (CCD) is used to optimize each treatment process, as well as evaluate the individual and interactive effects of operational cationic resin dosage and anionic resin dosage on the effectiveness of each application in terms of color, chemical oxygen demand (COD), and NH(3)-N removal efficiency. A statistically significant model for color, COD, and NH(3)-N removal was obtained with high coefficient of determination values (R(2)>0.8). Under optimum operational conditions, the removal efficiency levels for color, COD, and NH(3)-N are 96.8%, 87.9%, and 93.8% via cationic/anionic sequence, and 91.6%, 72.3%, and 92.5% via anionic/cationic sequence, respectively. The experimental results and the model predictions agree well with each other.
    Matched MeSH terms: Cations*
  3. Usman A, Chantrapromma S, Fun HK, Poh BL, Karalai C
    Acta Crystallogr C, 2002 Jan;58(Pt 1):o46-7.
    PMID: 11781493
    In the title complex, the 1:1 ionic adduct of hexamethylenetetraminium and 2,4,6-trinitrophenolate, C6H13N4+*C6H2N3O7-, the cation acts as a donor for bifurcated hydrogen bonds to the O atoms of the phenolate and one of the nitro groups of the 2,4,6-trinitrophenolate anion. The crystal structure is built from sheets of cations and anions, and is stabilized by intermolecular C-H...O and C-H...pi interactions.
    Matched MeSH terms: Cations
  4. Sim YL, Ariffin A, Khan MN
    J. Org. Chem., 2007 Oct 26;72(22):8452-8.
    PMID: 17918997
    A kinetic study on the aqueous cleavage of N-(2-methoxyphenyl)phthalimide (1) and N-(2-hydroxyphenyl)phthalimide (2), under the buffers of N-methylmorpholine, reveals the equilibrium presence of monocationic amide (Ctam) formed due to nucleophilic reactions of N-methylmorpholine with 1 and 2. Pseudo-first-order rate constants for the reactions of water and HO- with Ctam (formed through nucleophilic reaction of N-methylmorpholine with 1) are 4.60 x 10(-5) s-1 and 47.9 M-1 s-1, respectively. But the cleavage of Ctam, formed through nucleophilic reaction of N-methylmorpholine with 2, involves intramolecular general base (2'-O- group of Ctam)-assisted water attack at carbonyl carbon of cationic amide group of Ctam in or before the rate-determining step.
    Matched MeSH terms: Cations/chemical synthesis; Cations/chemistry
  5. Hong FJ, Low YY, Chong KW, Thomas NF, Kam TS
    J. Org. Chem., 2014 May 16;79(10):4528-43.
    PMID: 24754525 DOI: 10.1021/jo500559r
    A systematic study of the electrochemical oxidation of 1,2-diarylalkenes was carried out with the focus on detailed product studies and variation of product type as a function of aromatic substitution. A reinvestigation of the electrochemical oxidation of 4,4'-dimethoxystilbene under various conditions was first carried out, and all products formed were fully characterized and quantitated. This was followed by a systematic investigation of the effect of aromatic substitution on the nature and distribution of the products. The aromatic substituents were found to fall into three main categories, viz., substrates in which the nature and position of the aromatic substituents gave rise to essentially the same products as 4,4'-dimethoxystilbene, for example, tetraaryltetrahydrofurans, dehydrotetralins, and aldehydes (p-MeO or p-NMe2 on one ring and X on the other ring, where X = o-MeO or p-alkyl, or m- or p-EWG; e.g., 4-methoxy-4'-trifluoromethylstilbene); those that gave rise to a mixture of indanyl (or tetralinyl) acetamides and dehydrotetralins (or pallidols) (both or one ring substituted by alkyl groups, e.g., 4,4'-dimethylstilbene); and those where strategic placement of donor groups, such as OMe and OH, led to the formation of ampelopsin F and pallidol-type carbon skeletons (e.g., 4,3',4'-trimethoxystilbene). Reaction pathways to rationalize the formation of the different products are presented.
    Matched MeSH terms: Cations/chemistry*
  6. Setifi Z, Lehchili F, Setifi F, Beghidja A, Ng SW, Glidewell C
    Acta Crystallogr C Struct Chem, 2014 Mar;70(Pt 3):338-41.
    PMID: 24594730 DOI: 10.1107/S2053229614004379
    In the title salt, C14H18N2(2+) · 2C9H5N4O(-), the 1,1'-diethyl-4,4'-bipyridine-1,1'-diium dication lies across a centre of inversion in the space group P21/c. In the 1,1,3,3-tetracyano-2-ethoxypropenide anion, the two independent -C(CN)2 units are rotated, in conrotatory fashion, out of the plane of the central propenide unit, making dihedral angles with the central unit of 16.0(2) and 23.0(2)°. The ionic components are linked by C-H...N hydrogen bonds to form a complex sheet structure, within which each cation acts as a sixfold donor of hydrogen bonds and each anion acts as a threefold acceptor of hydrogen bonds.
    Matched MeSH terms: Cations/chemistry*
  7. Koh TM, Shanmugam V, Schlipf J, Oesinghaus L, Müller-Buschbaum P, Ramakrishnan N, et al.
    Adv. Mater. Weinheim, 2016 May;28(19):3653-61.
    PMID: 26990287 DOI: 10.1002/adma.201506141
    2D perovskites is one of the proposed strategies to enhance the moisture resistance, since the larger organic cations can act as a natural barrier. Nevertheless, 2D perovskites hinder the charge transport in certain directions, reducing the solar cell power conversion efficiency. A nanostructured mixed-dimensionality approach is presented to overcome the charge transport limitation, obtaining power conversion efficiencies over 9%.
    Matched MeSH terms: Cations
  8. Abdul-Razak I, Usman A, Fun HK, Yamin BM, Kasim NA
    Acta Crystallogr C, 2002 Mar;58(Pt 3):m162-4.
    PMID: 11870289
    In the title compound, [Fe(C(17)H(14)P)(2)](2)[Sb(4)Cl(16)] x C(2)H(6)O, the Fe atoms lie on inversion centres and the pairs of cyclopentadienyl rings are consequently in a fully staggered conformation. The centrosymmetric anionic clusters formed by [Sb(4)Cl(16)](4-) are surrounded by the cations and are held together by weak C-H...Cl interactions. These formations stack along the a axis to form columns, and the columns are interconnected by another weak C-H...Cl interaction along the b axis.
    Matched MeSH terms: Cations
  9. Chantrapromma S, Usman A, Fun HK, Poh BL, Karalai C
    Acta Crystallogr C, 2002 Sep;58(Pt 9):o589-90.
    PMID: 12205398
    In the title ternary complex, C(10)H(9)N(2)(+).C(7)H(3)N(2)O(6)(-).C(7)H(4)N(2)O(6), the pyridinium cation adopts the role of the donor in an intermolecular N-H.O hydrogen-bonding interaction with the carboxylate group of the 3,5-dinitrobenzoate anion. The molecules of the ternary complex form molecular ribbons perpendicular to the b direction, which are stabilized by one N-H.O, one O-H.O and five C-H.O intermolecular hydrogen bonds. The ribbons are further interconnected by three intermolecular C-H.O hydrogen bonds into a three-dimensional network.
    Matched MeSH terms: Cations
  10. Rahman AA, Usman A, Chantrapromma S, Fun HK
    Acta Crystallogr C, 2003 Sep;59(Pt 9):i92-4.
    PMID: 12944636
    A sample of hydronium perchlorate, H(3)O(+) x ClO(4)(-), crystallized from ethanol at ambient temperature, was found to be orthorhombic (space group Pnma) at both 193 and 293 K, with no phase transition observed in this temperature range. This contrasts with the earlier observation [Nordman (1962). Acta Cryst. 15, 18-23] of a monoclinic phase (space group P2(1)/n) at 193 K for crystals grown at that temperature from perchloric acid. The hydronium and perchlorate ions lie across a mirror plane but it is not possible to define at either temperature a simple description of the H-atom positions due to the three-dimensional tumbling of the hydronium cation.
    Matched MeSH terms: Cations
  11. Harun, S.W., Tamjis, M.R., Muhd-Yassin, S.Z., Abd-Rahman, M.K., Ahmad, H.
    ASM Science Journal, 2007;1(2):129-133.
    This paper demonstrates an erbium/ytterbium co-doped fi bre amplifi er (EYDFA) which used a pumping wavelength of 1058 nm, whereby the amplifi cation was assisted by the energy transfer between Yb and Er ions. The energy transfer increased the erbium doping concentration limit that was imposed by concentration quenching in erbium-doped fi bre. The optimum length was obtained at 4m~6m for erbium/ytterbium co-doped fi bre with Er ion concentration of 1000 p.p.m. This enabled the development of a compact amplifi er with a shorter gain medium compared to erbium-doped fi bre amplifi ers which use a gain medium of up to 15 m. A 1058 nm pumping wave-length was used for the EYDFA, as 1480 nm pumping resulted in severely degraded gain and noise fi gures because the energy transfer could not be achieved. The use of the optical isolator improved the small signal gain and noise fi gure by about 4.8 dB and 1.6 dB, respectively. Without the isolator, gain saturation and a noise fi gure penalty were observed due to the oscillating laser which was created at around 1534 nm by spurious refl ection. This showed that the usage of optical isolators was an important aspect to consider when designing an EYDFA.
    Matched MeSH terms: Cations
  12. Kim J, Kim HP, Teridi MA, Yusoff AR, Jang J
    Sci Rep, 2016 11 22;6:37378.
    PMID: 27874026 DOI: 10.1038/srep37378
    Bandgap tuning of a mixed organic cation perovskite is demonstrated via chemical vapor deposition process. The optical and electrical properties of the mixed organic cation perovskite can be manipulated by varying the growth time. A slight shift of the absorption band to shorter wavelengths is demonstrated with increasing growth time, which results in the increment of the current density. Hence, based on the optimized growth time, our device exhibits an efficiency of 15.86% with negligible current hysteresis.
    Matched MeSH terms: Cations
  13. Sani F, Shafie S, Lim HN, Musa AO
    Materials (Basel), 2018 Jun 14;11(6).
    PMID: 29899206 DOI: 10.3390/ma11061008
    Remarkable attention has been committed to the recently discovered cost effective and solution processable lead-free organic-inorganic halide perovskite solar cells. Recent studies have reported that, within five years, the reported efficiency has reached 9.0%, which makes them an extremely promising and fast developing candidate to compete with conventional lead-based perovskite solar cells. The major challenge associated with the conventional perovskite solar cells is the toxic nature of lead (Pb) used in the active layer of perovskite material. If lead continues to be used in fabricating solar cells, negative health impacts will result in the environment due to the toxicity of lead. Alternatively, lead free perovskite solar cells could give a safe way by substituting low-cost, abundant and non toxic material. This review focuses on formability of lead-free organic-inorganic halide perovskite, alternative metal cations candidates to replace lead (Pb), and possible substitutions of organic cations, as well as halide anions in the lead-free organic-inorganic halide perovskite architecture. Furthermore, the review gives highlights on the impact of organic cations, metal cations and inorganic anions on stability and the overall performance of lead free perovskite solar cells.
    Matched MeSH terms: Cations
  14. Yeo CI, Tan YS, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2015 Oct 1;71(Pt 10):1159-64.
    PMID: 26594396 DOI: 10.1107/S2056989015016655
    The crystal and mol-ecular structures of the title salt, C8H8N3S2 (+)·Cl(-), (I), and salt hydrate, C8H7ClN3S2 (+)·Cl(-)·H2O, (II), are described. The heterocyclic ring in (I) is statistically planar and forms a dihedral angle of 9.05 (12)° with the pendant phenyl ring. The comparable angle in (II) is 15.60 (12)°, indicating a greater twist in this cation. An evaluation of the bond lengths in the H2N-C-N-C-N sequence of each cation indicates significant delocalization of π-electron density over these atoms. The common feature of the crystal packing in (I) and (II) is the formation of charge-assisted amino-N-H⋯Cl(-) hydrogen bonds, leading to helical chains in (I) and zigzag chains in (II). In (I), these are linked by chains mediated by charge-assisted iminium-N(+)-H⋯Cl(-) hydrogen bonds into a three-dimensional architecture. In (II), the chains are linked into a layer by charge-assisted water-O-H⋯Cl(-) and water-O-H⋯O(water) hydrogen bonds with charge-assisted iminium-N(+)-H⋯O(water) hydrogen bonds providing the connections between the layers to generate the three-dimensional packing. In (II), the chloride anion and water mol-ecules are resolved into two proximate sites with the major component being present with a site occupancy factor of 0.9327 (18).
    Matched MeSH terms: Cations
  15. Jasmine NJ, Rajam A, Muthiah PT, Stanley N, Razak IA, Rosli MM
    Acta Crystallogr E Crystallogr Commun, 2015 Sep 1;71(Pt 9):o655-6.
    PMID: 26396888 DOI: 10.1107/S2056989015014796
    In the title salt, C5H7N(+)·C6H3ClNO(-), the 2-amino-pyri-din-ium cation inter-acts with the carboxyl-ate group of the 6-chloro-nicotinate anion through a pair of independent N-H⋯O hydrogen bonds, forming an R 2 (2)(8) ring motif. In the crystal, these dimeric units are connected further via N-H⋯O hydrogen bonds, forming chains along [001]. In addition, weak C-H⋯N and C-H⋯O hydrogen bonds, together with weak π-π inter-actions, with centroid-centroid distances of 3.6560 (5) and 3.6295 (5) Å, connect the chains, forming a two-dimensional network parallel to (100).
    Matched MeSH terms: Cations
  16. Muthukkumar M, Karthikeyan A, Poovarasan M, Ruckmani V, Rajaram D, Jegan Jennifer S, et al.
    Acta Crystallogr E Crystallogr Commun, 2019 Apr 01;75(Pt 4):443-446.
    PMID: 31161053 DOI: 10.1107/S2056989019003189
    In the redetermination of the title compound, C3H5N2OS+·CI-, the asymmetric unit consists of one independent 2-oxo-1,3-thia-zolidin-4-iminium cation and one independent chloride anion. The cation inter-acts with a chloride anion via N-H⋯Cl hydrogen bonds forming a supra-molecular chain along [010]. These supra-molecular chains are further extended by weak C-H⋯Cl and C-H⋯O inter-actions, forming a two-dimensional network parallel to (001). The crystal structure is further stabilized by weak C-O⋯π inter-actions, supporting a three-dimensional architecture. The structure was previously determined by Ananthamurthy & Murthy [Z. Kristallogr. (1975). 8, 356-367] but has been redetermined with higher precision to allow the hydrogen-bonding patterns and supra-molecular inter-actions to be investigated.
    Matched MeSH terms: Cations
  17. Sivajeyanthi P, Balasubramani K, Jeevaraj M, Thanigaimani K, Khalib NC, Razak IA
    Acta Crystallogr E Crystallogr Commun, 2015 Jun 1;71(Pt 6):o376-7.
    PMID: 26090174 DOI: 10.1107/S2056989015008397
    In the crystal of the title mol-ecular salt, C7H9N6O(+)·NO3 (-), the cations and anions are linked via N-H⋯O and O-H⋯O hydrogen bonds, forming sheets parallel to (100). Within the sheets there are numerous hydrogen-bonding ring motifs.
    Matched MeSH terms: Cations
  18. Johnson A, Mbonu J, Hussain Z, Loh WS, Fun HK
    Acta Crystallogr E Crystallogr Commun, 2015 Jun 1;71(Pt 6):m139-40.
    PMID: 26090171 DOI: 10.1107/S2056989015010014
    The asymmetric unit of the title compound, [Co(C2H6N5)2(H2O)4][Co(C7H3NO4)2]2·2H2O, features 1.5 Co(II) ions (one anionic complex and one half cationic complex) and one water mol-ecule. In the cationic complex, the Co(II) atom is located on an inversion centre and is coordinated by two triazolium cations and four water mol-ecules, adopting an octa-hedral geometry where the N atoms of the two triazolium cations occupy the axial positions and the O atoms of the four water mol-ecules the equatorial positions. The two triazole ligands are parallel offset (with a distance of 1.38 Å between their planes). In the anionic complex, the Co(II) ion is six-coordinated by two N and four O atoms of the two pyridine-2,6-di-carboxyl-ate anions, exhibiting a slightly distorted octa-hedral coordination geometry in which the mean plane of the two pyridine-2,6-di-carboxyl-ate anions are almost perpendicular to each other, making a dihedral angle of 85.87 (2)°. In the crystal, mol-ecules are linked into a three-dimensional network via C-H⋯O, C-H⋯N, O-H⋯O and N-H⋯O hydrogen bonds.
    Matched MeSH terms: Cations
  19. Sheshadri SN, Kwong HC, Chidan Kumar CS, Quah CK, Siddaraju BP, Veeraiah MK, et al.
    Acta Crystallogr E Crystallogr Commun, 2018 May 01;74(Pt 5):752-756.
    PMID: 29850106 DOI: 10.1107/S2056989018006217
    In the cation of the title salt, C20H19N2O+·Br-, the phenyl rings are inclined to one another by 38.38 (8)°, whereas the central phenyl ring and the pyridiniminium ring are almost perpendicular with a dihedral angle of 87.37 (9)°. The N+=C cationic double bond was verified by the shortened bond length of 1.337 (2) Å. In the crystal, the Br- anion is linked to the cation by an N-H⋯Br hydrogen bond. C-H⋯O hydrogen bonds link adjacent pyridiniminium cations into inversion dimers with an R22(18) graph-set motif. These dimers are stacked in a phen-yl-phenyl T-shaped geometry through C-H⋯π inter-actions. A Hirshfeld surface analysis was conducted to verify the contributions of the different inter-molecular inter-actions.
    Matched MeSH terms: Cations
  20. Lee JS, Lo YL, Chye FY
    This study was carried out to elucidate the effect of three types of cation (K+, Ca2+ and Na+) at various concentrations on the gelling properties of untreated Eucheuma cottoni, with the ultimate aim to explore the possibility of utilizing the seaweed in its natural form as gelling agent. Results obtained suggest that E. cottonii also exhibited the dramatic cation specificity of k-carrageenan, in which the dependence of gel strength follows the order: K+ > Ca2+ > Na+. As expected, cations addition exerts adverse effect on the syneresis, water holding capacity and freeze-thaw stability of the seaweed gel. Water holding capcity of the gel is however independent of the increased concentrations of K+(p>0.05). Storage duration and storage temperature significantly (p<0.05) affect the syneresis and water holding capacity of the gel. Among the cations, K+ appears to be better in improving the gel properties of the seaweed.
    Matched MeSH terms: Cations
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