Displaying publications 1 - 20 of 38 in total

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  1. Karen A
    World Hosp Health Serv, 2015;51(1):26-30.
    PMID: 26058289
    Established 20 years ago with a single dialysis center assisting only 20 patients with 6 hemodialysis machines, Medicare has grown leaps and bounds to assist thousands of poor patients to obtain a highly subsidized rate for quality treatment. Millions of ringgit raised via various fundraising projects and events have been well utilized to serve the growing number of kidney patients in Malaysia who simply cannot bear the exorbitant cost of treatment. Staying true to its mission, Medicare extends its assistance to needy kidney patients and their families, who indirectly have become part of the Medicare family.
  2. Break MK, Tahir MI, Crouse KA, Khoo TJ
    Bioinorg Chem Appl, 2013;2013:362513.
    PMID: 24319401 DOI: 10.1155/2013/362513
    Two bidentate Schiff base ligands having nitrogen sulphur donor sequence were derived from the condensation of S-benzyldithiocarbazate (SBDTC) with 2-chloroacetophenone and 4-chloroacetophenone to give S-benzyl- β -N-(2-chlorophenyl)methylenedithiocarbazate (NS2) and S-benzyl- β -N-(4-chlorophenyl)methylenedithiocarbazate (NS4) isomers. Each of the ligands was then chelated with Cd(2+), Zn(2+), Cu(2+), and Ni(2+). The compounds were characterized via IR spectroscopy and melting point while the structure of NS4 was revealed via X-ray crystallography. Finally, the compounds were screened for antimicrobial activity to investigate the effect that is brought by the introduction of the chlorine atom to the benzene ring. X-ray crystallographic analysis showed that the structure of NS4 is planar with a phenyl ring that is nearly perpendicular to the rest of the molecules. The qualitative antimicrobial assay results showed that NS4 and its complexes lacked antifungal activity while Gram-positive bacteria were generally inhibited more strongly than Gram-negative bacteria. Furthermore, NS4 metal complexes were inhibited more strongly than the ligand while the opposite was seen with NS2 ligand and its complexes due to the partial solubility in dimethyl sulfoxide (DMSO). It was concluded that generally NS2 derivatives have higher bioactivity than that of NS4 derivatives and that the Cd complexes of both ligands have pronounced activity specifically on K. rhizophila.
  3. Paulus G, Kwong HC, Crouse KA, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2020 Aug 01;76(Pt 8):1245-1250.
    PMID: 32844007 DOI: 10.1107/S2056989020008762
    The complete mol-ecule of the title hydrazine carbodi-thio-ate derivative, C32H30N4O2S4, is generated by a crystallographic twofold axis that bis-ects the di-sulfide bond. The mol-ecule is twisted about this bond with the C-S-S-C torsion angle of 90.70 (8)° indicating an orthogonal relationship between the symmetry-related halves of the mol-ecule. The conformation about the imine bond [1.282 (2) Å] is E and there is limited delocalization of π-electron density over the CN2C residue as there is a twist about the N-N bond [C-N-N-C torsion angle = -166.57 (15)°]. An intra-molecular hydroxyl-O-H⋯N(imine) hydrogen bond closes an S(6) loop. In the crystal, methyl-ene-C-H⋯π(tol-yl) contacts assemble mol-ecules into a supra-molecular layer propagating in the ab plane: the layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surfaces confirm the importance of H⋯H contacts, which contribute 46.7% of all contacts followed by H⋯C/C⋯H contacts [25.5%] reflecting, in part, the C-H⋯π(tol-yl) contacts. The calculation of the inter-action energies confirm the importance of the dispersion term and the influence of the stabilizing H⋯H contacts in the inter-layer region.
  4. Mohd Abdul Fatah Abdul Manan, M. Ibrahim M. Tahir, Crouse, Karen A., How, Fiona N.-F., Watkin, David J.
    MyJurnal
    The crystal structure of the title compound has been determined. The compound crystallized in the triclinic space group P -1, Z = 2, V = 1839.42(18) Å3 and unit cell parameters a = 11.0460(6) Å, b = 13.3180(7) Å, c = 13.7321(8) Å, a = 80.659(3)°, ß = 69.800(3)° and ? = 77.007(2)° with one disordered dimethylsulfoxide solvent molecule with the sulfur and oxygen atoms are distributed over two sites; S101/S102 [site occupancy factors: 0.6035/0.3965] and O130/O131 [site occupancy factor 0.3965/0.6035]. The C22-S21 and C19-S20 bond distances of 1.779(7) Å and 1.788(8) Å indicate that both of the molecules are connected by the disulfide bond [S20-S21 2.055(2) Å] in its thiol form. The crystal structure reveals that both of the 5-bromoisatin moieties are trans with respect to the [S21-S20 and C19-N18] and [S20-S21 and C22-N23] bonds whereas the benzyl group from the dithiocarbazate are in the cis configuration with respect to [S21-S20 and C19-S44] and [S20-S21 and C22-S36] bonds. The crystal structure is further stabilized by intermolecular hydrogen bonds of N9-H35···O16 formed between the two molecules and N28-H281···O130, N28-H281···O131 and C41-H411···O131 with the solvent molecule.
  5. Low ML, Ravoof TB, Tahir MI, Crouse KA, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2014 Nov 1;70(Pt 11):o1207-8.
    PMID: 25484832 DOI: 10.1107/S1600536814023228
    In the title salt of an S-substituted di-thio-carbazate, C16H16N3S2 (+)·Cl(-), the dihedral angles between the almost planar (r.m.s deviation = 0.005 Å) central CN2S2 residue and the terminal pyridinium and phenyl rings are 80.09 (11) and 3.82 (11)°, respectively, indicating the cation has an L-shape; the amine H and thione S atoms are syn. The conformation about each of the imine [1.376 (3) Å] and ethene [1.333 (4) Å] bonds is E. The shortened C-C bond [1.444 (4) Å] linking the double bonds is consistent with conjugation in this part of the mol-ecule. In the crystal, supra-molecular layers with a jagged topology are formed by charged-assisted amine-H⋯Cl(-) and pyridinium-N(+)-H⋯Cl(-) hydrogen bonds. The layers stack along the a axis with no specific directional inter-actions between them.
  6. Ravoof TB, Omar SA, Mohamed Tahir MI, Crouse KA
    Acta Crystallogr Sect E Struct Rep Online, 2012 May 1;68(Pt 5):m534-5.
    PMID: 22590061 DOI: 10.1107/S1600536812013529
    The title compound, [Zn(C(15)H(14)N(3)S(2))(2)], contains two chemically equivalent Schiff base anions that are coordinated to the Zn(II) ion as tridentate N,N',S-chelating ligands, creating a distorted octa-hedral environment [the smallest angle being 75.40 (6)° and the widest angle being 162.87 (6)°], with the two S atoms in cis positions. The dihedral angle between the mean planes of the two coordinating ligands is 85.65 (5)°. Weak C-H⋯S hydrogen bonds are also observed.
  7. Ravoof TB, Omar SA, Mohamed Tahir MI, Crouse KA
    Acta Crystallogr Sect E Struct Rep Online, 2012 Apr 1;68(Pt 4):m390-1.
    PMID: 22589778 DOI: 10.1107/S1600536812009592
    In the title compound, [Zn(C(20)H(16)N(3)S(2))(2)]·CH(3)CN, two different Schiff base moieties coordinate to the central Zn(II) ion as tridentate N,N',S-chelating ligands, creating a distorted octa-hedral environment [the smallest angle being 73.24 (6)° and the widest angle being 155.73 (7)°], with the two S atoms in cis positions. The dihedral angle between the mean planes of the two coordinating ligands is 83.65 (5)°. The crystal packing is consolidated by weak C-H⋯N hydrogen-bonding inter-actions.
  8. Omar SA, Ravoof TB, Mohamed Tahir MI, Crouse KA
    Acta Crystallogr Sect E Struct Rep Online, 2012 Mar 1;68(Pt 3):m316-7.
    PMID: 22412456 DOI: 10.1107/S1600536812006952
    The structure of the title compound, [Ni(C(15)H(14)N(3)S(2))(2)]·H(2)O, has one mol-ecule in the asymmetric unit, along with a solvent water mol-ecule. The two different Schiff base moieties coordinate to the central Ni(II) ion as tridentate N,N',S-chelating ligands, creating a six-coordinate distorted octa-hedral environment [the smallest angle being 77.43 (7)° and the widest angle being 169.99 (7)°]. The mean planes of the two ligands are nearly orthogonal to each other with an angle of 89.53 (6)°. The packing of the complex is supported by O-H⋯N and O-H⋯S hydrogen bonding between the solvent water mol-ecule and the uncoordinated N and S atoms of neighbouring ligands.
  9. Tayamon S, Mazlan NA, Ravoof TB, Mohamed Tahir MI, Crouse KA
    Acta Crystallogr Sect E Struct Rep Online, 2012 Nov 1;68(Pt 11):o3104-5.
    PMID: 23284431 DOI: 10.1107/S1600536812042018
    The title compound C(8)H(15)N(3)S has two mol-ecules in the asymmetric unit in which cis-trans isomerism is exhibited around the N(NH)C=S bonds. The cyclo-hexyl rings in both mol-ecules adopt a chair conformation. In the crystal, N-H⋯S hydrogen bonding produces dimers, which are inter-connected through further N-H⋯S hydrogen bonds, forming chains along the b-axis direction.
  10. Tayamon S, Ravoof TB, Tahir MI, Crouse KA, Tiekink ER
    PMID: 23476568 DOI: 10.1107/S1600536813003966
    In the title salt, C14H17N2(+)·Cl(-), the central N atom is pyramidal (sum of bond angles = 330.9°) and there is a near orthogonal relationship between the benzene rings [dihedral angle = 89.95 (10)°]. The crystal packing features N-H⋯Cl hydrogen bonds, which lead to a supra-molecular undulating ribbon along the a axis comprising edge-shared eight-membered {⋯HNH⋯Cl}2 synthons. The chains are connected into layers in the ab plane by C-H⋯π inter-actions.
  11. Low ML, Ravoof TB, Tahir MI, Crouse KA, Tiekink ER
    Acta Crystallogr Sect E Struct Rep Online, 2013 Feb 1;69(Pt 2):o167-8.
    PMID: 23424455 DOI: 10.1107/S1600536812051537
    In the title compound, C(16)H(15)N(3)S(2), the central C(2)N(2)S(2) residue is planar (r.m.s. deviation = 0.045 Å) and the pyridyl and benzene rings are inclined and approximately coplanar to this plane, respectively [dihedral angles = 72.85 (9) and 10.73 (9)°], so that, overall, the mol-ecule adopts an L-shape. The conformation about each of the N=C [1.290 (3) Å] and C=C [1.340 (3) Å] bonds is E. Supra-molecular chains along [1-10] are stabilized by N-H⋯N(pyridine) hydrogen bonding and these are connected into a double layer that stacks along the c-axis direction by C-H⋯π(pyridine) inter-actions.
  12. Break MK, Mehta S, Tahir MI, Crouse KA, Khoo TJ
    PMID: 23424463 DOI: 10.1107/S1600536812051008
    The title compound, C(12)H(16)N(2)S(3), was obtained by the condensation reaction of S-benzyl dithio-carbazate and 3-mercaptobutan-2-one. The phenyl ring and thiol (SH) group are approximately perpendicular [S-C-C-C and N-C-C-S torsion angles = 67.8 (3) and 116.9 (2)°, respectively] to the rest of the mol-ecule. In the crystal, mol-ecules are linked by weak S-H⋯S and N-H⋯S hydrogen bonds, π-π inter-actions between the benzene rings [centroid-centroid distance = 3.823 (2) Å] and C-H⋯π inter-actions.
  13. Tarafder MT, Kasbollah A, Saravanan N, Crouse KA, Ali AM, Tin Oo K
    J. Biochem. Mol. Biol. Biophys., 2002 Apr;6(2):85-91.
    PMID: 12186762
    Eight selective nitrogen-sulfur donor ligands have been synthesized from the condensation of S-methyldithiocarbazate (SMDTC) with aldehydes and ketones with a view to evaluating their antimicrobial and cytotoxic activities, and also to correlate the biological properties with the structure of the ligands. The compounds were all characterized by elemental analyses and other physicochemical techniques. SMDTC and the Schiff bases were screened for antimicrobial and cytotoxic activities. SMDTC showed very large inhibition zones (24-44 mm) against bacteria and fungi with a minimum inhibitory concentration (MIC) of 390-25,000 and 1562-6250 microg ml(-1), against different bacteria and fungi, respectively. Streptomycin and nystatin were used as the internal standards against bacteria and fungi, respectively. SMDTC along with its Schiff bases with pyridine-2-carboxaldehyde, acetylacetone and 2,3-butanedione were strongly antifungal and the MIC values were comparable to nystatin. Most of the Schiff bases were strongly cytotoxic. In particular, those with pyridine-2-carboxaldehyde and 2,3-butanedione have CD(50) values of 5.5, 1.9-2.0 microg ml(-1), respectively, against leukemic cells, while against colon cancer cells, the values were 3.7 and 2.0 microg ml(-1), respectively. The glyoxal Schiff base was strongly active only against leukemic cell with CD(50) value of 4.0 microg ml(-1). The present findings have been compared with standard drugs.
  14. Tan MY, Crouse KA, Ravoof TB, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2015 Dec 1;71(Pt 12):o1047-8.
    PMID: 26870491 DOI: 10.1107/S2056989015023531
    In the title thio-semicarbazone compound, C18H18ClN3S, the CN3S residue is almost planar (r.m.s. deviation = 0.0031 Å) and forms dihedral angles of 65.99 (7) and 34.60 (10)° with the phenyl and chloro-benzene rings, respectively; the dihedral angle between the aromatic rings is 85.13 (8)°. The conformation about the C=N bond is Z, and that about the C=C bonds is E. The imine N and ethyl N atoms are syn and are linked by an eth-yl-imine N-H⋯N hydrogen bond. This H atom also forms an inter-molecular hydrogen bond to the thione S atom, resulting in a supra-molecular helical chain propagating along the b axis. The chains are consolidated into a three-dimensional architecture by phenyl-C-H⋯Cl contacts and weak π-π inter-actions between centrosymmetrically related chloro-benzene rings [inter-centroid distance = 3.9127 (15) Å].
  15. Tan MY, Kwong HC, Crouse KA, Ravoof TBSA, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2021 Aug 01;77(Pt 8):788-794.
    PMID: 34422302 DOI: 10.1107/S2056989021006666
    The title thio-urea derivative, C17H19N3OS, adopts a U-shaped conformation with the dihedral angle between the terminal aromatic rings being 73.64 (5)°. The major twist in the mol-ecule occurs about the ethane bond with the Ci-Ce-Ce-Cb torsion angle being -78.12 (18)°; i = imine, e = ethane and b = benzene. The configuration about the imine bond is E, the N-bound H atoms lie on opposite sides of the mol-ecule and an intra-molecular amine-N-H⋯N(imine) hydrogen bond is evident. In the mol-ecular packing, hydroxyl-O-H⋯S(thione) and amine-N-H⋯O hydrogen bonding feature within a linear, supra-molecular chain. The chains are connected into a layer in the ab plane by a combination of methyl-ene-C-H⋯S(thione), methyl-ene-C-H⋯O(hydrox-yl), methyl-C-H⋯π(phen-yl) and phenyl-C-H⋯π(hy-droxy-benzene) inter-actions. The layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface highlights the presence of weak methyl-C-H⋯O(hydrox-yl) and H⋯H inter-actions in the inter-layer region. Computational chemistry indicates that dispersion energy is the major contributor to the overall stabilization of the mol-ecular packing.
  16. Tan MY, Kwong HC, Crouse KA, Ravoof TBSA, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2021 Aug 01;77(Pt 8):839-846.
    PMID: 34422312 DOI: 10.1107/S2056989021007398
    The title zinc bis-(thio-semicarbazone) complex, [Zn(C22H17N4O2S)2], comprises two N,S-donor anions, leading to a distorted tetra-hedral N2S2 donor set. The resultant five-membered chelate rings are nearly planar and form a dihedral angle of 73.28 (3)°. The configurations about the endocyclic- and exocyclic-imine bonds are Z and E, respectively, and that about the ethyl-ene bond is E. The major differences in the conformations of the ligands are seen in the dihedral angles between the chelate ring and nitro-benzene rings [40.48 (6) cf. 13.18 (4)°] and the N-bound phenyl and nitro-benzene ring [43.23 (8) and 22.64 (4)°]. In the crystal, a linear supra-molecular chain along the b-axis direction features amine-N-H⋯O(nitro) hydrogen bonding. The chains assemble along the 21-screw axis through a combination of phenyl-C-H⋯O(nitro) and π(chelate ring)-π(phen-yl) contacts. The double chains are linked into a three-dimensional architecture through phenyl-C-H⋯O(nitro) and nitro-O⋯π(phen-yl) inter-actions.
  17. Khairuanuar NL, Crouse KA, Kwong HC, Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2020 Jul 01;76(Pt 7):990-997.
    PMID: 32695439 DOI: 10.1107/S2056989020007070
    The title hydrazine carbodi-thio-ate chloro-form hemisolvate, 2C15H14N2O2S2·CHCl3, comprises two independent hydrazine carbodi-thio-ate mol-ecules, A and B, and a chloro-form mol-ecule; the latter is statistically disordered about its mol-ecular threefold axis. The common features of the organic mol-ecules include an almost planar, central CN2S2 chromophore [r.m.s. deviation = 0.0203 Å (A) and 0.0080 Å (B)], an E configuration about the imine bond and an intra-molecular hydroxyl-O-H⋯N(imine) hydrogen bond. The major conformational difference between the mol-ecules is seen in the relative dispositions of the phenyl rings as indicated by the values of the dihedral angles between the central plane and phenyl ring of 71.21 (6)° (A) and 54.73 (7)° (B). Finally, a difference is seen in the disposition of the outer hydroxyl-H atoms, having opposite relative orientations. In the calculated gas-phase structure, the entire mol-ecule is planar with the exception of the perpendicular phenyl ring. In the mol-ecular packing, the A and B mol-ecules assemble into a two-mol-ecule aggregate via N-H⋯S hydrogen bonds and eight-membered {⋯HNCS}2 synthons. The dimeric assemblies are connected into supra-molecular chains via hydroxyl-O-H⋯O(hydrox-yl) hydrogen bonds and these are linked into a double-chain through hy-droxy-O-H⋯π(phen-yl) inter-actions. The double-chains are connected into a three-dimensional architecture through phenyl-C-H⋯O(hydrox-yl) and phenyl-C-H⋯π(phen-yl) inter-actions. The overall assembly defines columns along the a-axis direction in which reside the chloro-form mol-ecules, which are stabilized by chloro-form-methine-C-H⋯S(thione) and phenyl-C-H⋯Cl contacts. The analysis of the calculated Hirshfeld surfaces, non-covalent inter-action plots and inter-action energies confirm the importance of the above-mentioned inter-actions, but also of cooperative, non-standard inter-actions such as π(benzene)⋯π(hydrogen-bond-mediated-ring) contacts.
  18. Tan MY, Crouse KA, Ravoof TBSA, Jotani MM, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2017 Nov 01;73(Pt 11):1607-1611.
    PMID: 29152334 DOI: 10.1107/S2056989017014128
    The title compound, C23H21N3O2, is constructed about an almost planar disubstituted amino-urea residue (r.m.s. deviation = 0.0201 Å), which features an intra-molecular amine-N-H⋯N(imine) hydrogen bond. In the 'all-trans' chain connecting this to the terminal meth-oxy-benzene residue, the conformation about each of the imine and ethyl-ene double bonds is E. In the crystal, amide-N-H⋯O(carbon-yl) hydrogen bonds connect centrosymmetrically related mol-ecules into dimeric aggregates, which also incorporate ethyl-ene-C-H⋯O(amide) inter-actions. The dimers are linked by amine-phenyl-C-H⋯π(imine-phen-yl) and meth-oxy-benzene-C-H⋯π(amine-phen-yl) inter-actions to generate a three-dimensional network. The importance of C-H⋯π inter-actions in the mol-ecular packing is reflected in the relatively high contributions made by C⋯H/H⋯C contacts to the Hirshfeld surface, i.e. 31.6%.
  19. Tan MY, Crouse KA, Ravoof TBSA, Jotani MM, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2018 Jan 01;74(Pt 1):21-27.
    PMID: 29416884 DOI: 10.1107/S2056989017017273
    Two independent mol-ecules (A and B) comprise the asymmetric unit of the title compound, C18H21N3O3. The urea moiety is disubstituted with one amine being linked to a phenyl ring, which is twisted out of the plane of the CN2O urea core [dihedral angles = 25.57 (11) (A) and 29.13 (10)° (B)]. The second amine is connected to an imine (E conformation), which is linked in turn to an ethane bridge that links a disubstituted benzene ring. Intra-molecular amine-N-H⋯N(imine) and hydroxyl-O-H⋯O(meth-oxy) hydrogen bonds close S(5) loops in each case. The mol-ecules have twisted conformations with the dihedral angles between the outer rings being 38.64 (81) (A) and 48.55 (7)° (B). In the crystal, amide-N-H⋯O(amide) hydrogen bonds link the mol-ecules A and B via an eight-membered {⋯HNCO}2 synthon. Further associations between mol-ecules, leading to supra-molecular layers in the ac plane, are hydrogen bonds of the type hydroxyl-O-H⋯N(imine) and phenyl-amine-N-H⋯O(meth-oxy). Connections between layers, leading to a three-dimensional architecture, comprise benzene-C-H⋯O(hy-droxy) inter-actions. A detailed analysis of the calculated Hirshfeld surfaces shows mol-ecules A and B participate in very similar inter-molecular inter-actions and that any variations relate to conformational differences between the mol-ecules.
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