Displaying publications 41 - 60 of 66 in total

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  1. Mental Health and COVID-19: Policies, Guidelines, and Initiatives from the Asia-Pacific Region
    Samy AL, Awang Bono S, Tan SL, Low WY
    Asia Pac J Public Health, 2021 11;33(8):839-846.
    PMID: 34308673 DOI: 10.1177/10105395211025901
    The COVID-19 outbreak was declared a pandemic by the World Health Organization in March 2020 due to rapid intercontinental spread and high morbidity and mortality. Globally, the disease has had a major impact on human lives, including health, economic, employment, psychological, and overall well-being. The COVID-19, besides causing respiratory, neurological, and cardiovascular diseases, has had significant impact on mental health. Major mental health disorders, including depression, anxiety, and stress, have risen in parallel with increasing prevalence of COVID-19. Many population groups, including children, the elderly, those with chronic illnesses, and health care workers, have been affected. This review gives an overall assessment of the prevalence of COVID-19-associated psychological morbidity. In countries in the Asia-Pacific region, prevalence of depression ranged between 4.9% and 43.1%, anxiety from 7.0% to 43.0%, and stress from 3.4% to 35.7%. As COVID-19 continues to severely affect the psychosocial well-being of the population at large, countries have developed and revised policies, guidelines, and introduced new initiatives to curb mental health issues among their citizens. In the long run, pre-disaster preparedness is important to alleviate long-term post-pandemic psychiatric morbidity and to develop psychological resilience toward disasters and pandemic, alongside investment for better mental health coverage.
  2. Drug allergy knowledge, attitude, and practice: A survey among doctors and pharmacists in public health facilities of Sabah, Malaysia
    Kwan MSK, Tan SL, Keowmani T, Goh SL, Voo JYH, Tan HS, et al.
    Asia Pac Allergy, 2023 Sep;13(3):121-126.
    PMID: 37744958 DOI: 10.5415/apallergy.0000000000000115
    BACKGROUND: Given the deficits in allergists and testing capacity, the diagnosis of drug allergy is largely dependent on the clinician's and pharmacist's judgment. The ability to recognize drug allergies and respond appropriately is crucial to patient safety. Currently, there is a void in the evidence that limits the ability to recommend comprehensive and swift improvements on this front.

    OBJECTIVE: This study thus aimed to evaluate the knowledge, attitude, and practice toward drug allergy among doctors and pharmacists working in public healthcare facilities in Sabah, Malaysia.

    METHODS: This cross-sectional study was conducted in 24 hospitals and 11 clinics in Sabah. A validated Drug Allergy Knowledge, Attitude, and Practice Questionnaire was adapted from a published study and developed on an online survey platform. The questionnaire was distributed to all listed eligible respondents via email and personal messenger service.

    RESULTS: A total of 549 doctors and pharmacists responded, with an overall response rate of 18.2%. The total mean knowledge, attitude, and practice scores were 8.3 (SD, 1.98), 18.9 (SD, 2.55), and 17.3 (SD, 4.4), respectively. It was found that pharmacists performed significantly poorer than both medical officers (mean score difference = -0.5; P = 0.006) and specialists (mean score difference = -0.9; P = 0.020) in the knowledge domain. As the time in service doubles, the knowledge score increases significantly by 0.3 (P = 0.015).

    CONCLUSION: Knowledge, attitude, and practice on drug allergy among doctors and pharmacists in Sabah were poor. It is thus timely for advanced educational programs on drug allergy to be formalized and implemented.

  3. Fulltext Translation and Validation of the Malay Version of Comprehensive Geriatric Assessment Questionnaire for Older Adults in Malaysia
    Harith S, Tan SL
    Ann Geriatr Med Res, 2020 Jun;24(2):115-124.
    PMID: 32743332 DOI: 10.4235/agmr.20.0005
    Background: This study aimed to translate and validate the comprehensive geriatric assessment (CGA) questionnaire among older adult patients in Malaysia in the Malay language.

    Methods: The questionnaire contained items on the socio-demographic characteristics, medical condition, quality of life (QOL), nutritional status, functional capacity, and depression status. The forward and backward translation processes of the original English language version of the questionnaire were undertaken by three independent linguistic translators, while its content was validated by an expert team consisting of seven geriatricians, physicians, dietitian, and lecturers. The Malay version of the questionnaire was tested for face validity in 10 older adult patients over 65 years of age. The internal consistency reliability and construct validity were evaluated among 166 older adult patients (mean age, 71.0 years; 73.5% male). The questionnaire was administered through face-to-face interviews with the patients. Minor amendments were made after the content and face validity tests.

    Results: The internal consistency reliability was good, as the Cronbach's alpha for most of the scales surpassed 0.70, ranging from 0.70 to 0.98, with only one exception (Mini Nutritional Assessment Short-Form, Cronbach's alpha=0.62). The factor loadings for all scales were satisfactory (>0.40), ranging from 0.45 to 0.90.

    Conclusion: The Malay-version CGA showed evidence of satisfactory internal consistency reliability and construct validity in Malaysian geriatric patients.

  4. Fulltext Conduct of body donation and cadaveric dissection training during the COVID-19 pandemic: challenges, impacts and mitigation
    Wong LP, Alias H, Tan SL, Saw A
    Anat Sci Int, 2023 Sep;98(4):558-565.
    PMID: 37072599 DOI: 10.1007/s12565-023-00723-9
    The new coronavirus disease 2019 (COVID-19) has had a substantial impact on the Silent Mentor Programme (SMP), a programme in which members of the public may pledge their bodies to be used for medical training and research after their death. This study aimed to explore the conduct of body donations and simulation surgery training during the COVID-19 pandemic from the viewpoints of the committee members of the SMP and the next-of-kin of body donor pledgers. This study utilised a qualitative exploration method to seek an in-depth understanding of this phenomenon. In-depth individual interviews were carried out. Thematic analysis was used to identify patterns of themes. The COVID-19 polymerase chain reaction (RT-PCR) test is compulsory before accepting a body donation, and this resulted in the turning down of several donations. Being a donor is the final wish of pledgers and this turning down led to a negative emotional remorseful feeling in the next-of-kin of pledgers. From the perspective of students, it is feared that the conduct of the programme, particularly the home visit session being held online, has impeded teaching of humanistic values, compassion, and empathy, which is the prime philosophy of the programme. Previous to the pandemic, the programme ceremonies were well-attended, denoting the utmost respect and recognition of the mentors; however, travel restrictions due to the pandemic limiting in-person attendance resulted in ceremonies becoming less impactful. Continuous postponements of cadaveric dissection training also resulted in students missing training opportunities, hence potentially impairing their professional practice and humanistic values in the medical profession. Counselling interventions should be directed at easing the negative psychological impact on the next-of-kin of pledgers. As the COVID-19 pandemic may pose a significant impediment to achieving the educational outcomes of cadaveric dissection training, efforts to make up for these gaps are essential.
  5. Fulltext A cinnamaldehyde Schiff base of S-(4-methyl-benz-yl) di-thio-carbazate: crystal structure, Hirshfeld surface analysis and computational study
    Yusof ENM, Tahir MIM, Ravoof TBSA, Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2017 Apr 01;73(Pt 4):543-549.
    PMID: 28435717 DOI: 10.1107/S2056989017003991
    The title di-thio-carbazate ester (I), C18H18N2S2 [systematic name: (E)-4-methyl-benzyl 2-[(E)-3-phenyl-allyl-idene]hydrazinecarbodi-thio-ate, comprises an almost planar central CN2S2 residue [r.m.s. deviation = 0.0131 Å]. The methyl-ene(tolyl-4) group forms a dihedral angle of 72.25 (4)° with the best plane through the remaining non-hydrogen atoms [r.m.s. deviation = 0.0586 Å] so the mol-ecule approximates mirror symmetry with the 4-tolyl group bis-ected by the plane. The configuration about both double bonds in the N-N=C-C=C chain is E; the chain has an all trans conformation. In the crystal, eight-membered centrosymmetric thio-amide synthons, {⋯HNCS}2, are formed via N-H⋯S(thione) hydrogen bonds. Connections between the dimers via C-H⋯π inter-actions lead to a three-dimensional architecture. A Hirshfeld surface analysis shows that (I) possesses an inter-action profile similar to that of a closely related analogue with an S-bound benzyl substituent, (II). Computational chemistry indicates the dimeric species of (II) connected via N-H⋯S hydrogen bonds is about 0.94 kcal mol(-1) more stable than that in (I).
  6. (Tris{2-[(5-chloro-2-oxido-benzyl-idene-κO)amino-κN]eth-yl}amine-κN)-ytterbium(III): crystal structure and Hirshfeld surface analysis
    Lee SM, Lo KM, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Oct 1;72(Pt 10):1390-1395.
    PMID: 27746926
    The Yb(III) atom in the title complex, [Yb(C27H24Cl3N4O3)] [systematic name: (2,2',2''-{(nitrilo)-tris-[ethane-2,1-di-yl(nitrilo)-methylyl-idene]}tris-(4-chloro-phenolato)ytterbium(III)], is coordinated by a trinegative, hepta-dentate ligand and exists within an N4O3 donor set, which defines a capped octa-hedral geometry whereby the amine N atom caps the triangular face defined by the three imine N atoms. The packing features supra-molecular layers that stack along the a axis, sustained by a combination of aryl-C-H⋯O, imine-C-H⋯O, methyl-ene-C-H⋯π(ar-yl) and end-on C-Cl⋯π(ar-yl) inter-actions. A Hirshfeld surface analysis points to the major contributions of C⋯H/ H⋯C and Cl⋯H/H⋯Cl inter-actions (along with H⋯H) to the overall surface but the Cl⋯H contacts are at distances greater than the sum of their van der Waals radii.
  7. Fulltext fac-Aceto-nitrile-tricarbon-yl(di-methyl-carbamodi-thio-ato-κ(2)S,S')rhenium(I): crystal structure and Hirshfeld surface analysis
    Tan SL, Lee SM, Heard PJ, Halcovitch NR, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2017 Feb 01;73(Pt 2):213-218.
    PMID: 28217345 DOI: 10.1107/S2056989017000755
    The title compound, [Re(C3H6NS2)(C2H3N)(CO)3], features an octa-hedrally coordinated Re(I) atom within a C3NS2 donor set defined by three carbonyl ligands in a facial arrangement, an aceto-nitrile N atom and two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. In the crystal, di-thio-carbamate-methyl-H⋯O(carbon-yl) inter-actions lead to supra-molecular chains along [36-1]; both di-thio-carbamate S atoms participate in intra-molecular methyl-H⋯S inter-actions. Further but weaker aceto-nitrile-C-H⋯O(carbonyl) inter-actions assemble mol-ecules in the ab plane. The nature of the supra-molecular assembly was also probed by a Hirshfeld surface analysis. Despite their weak nature, the C-H⋯O contacts are predominant on the Hirshfeld surface and, indeed, on those of related [Re(CO)3(C3H6NS2)L] structures.
  8. A non-solvated form of [(Z)-O-methyl-N-(2-methyl-phen-yl)-thio-carbamato-κS](tri-phenyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis
    Yeo CI, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Oct 1;72(Pt 10):1446-1452.
    PMID: 27746938
    The title compound, [Au(C9H10NOS)(C18H15P)], features a near linear P-Au-S arrangement defined by phosphane P and thiol-ate S atoms with the minor distortion from the ideal [P-Au-S is 177.61 (2)°] being traced in part to the close intra-molecular approach of an O atom [Au⋯O = 3.040 (2) Å]. The packing features supra-molecular layers lying parallel to (011) sustained by a combination of C-H⋯π and π-π [inter-centroid distance = 3.8033 (17) Å] inter-actions. The mol-ecular structure and packing are compared with those determined for a previously reported hemi-methanol solvate [Kuan et al. (2008 ▸). CrystEngComm, 10, 548-564]. Relatively minor differences are noted in the conformations of the rings in the Au-containing mol-ecules. A Hirshfeld surface analysis confirms the similarity in the packing with the most notable differences relating to the formation of C-H⋯S contacts between the constituents of the solvate.
  9. 3,3-Bis(2-hy-droxy-eth-yl)-1-(4-methyl-benzoyl)thio-urea: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Azizan AHS, Jotani MM, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 Oct 01;75(Pt 10):1472-1478.
    PMID: 31636978 DOI: 10.1107/S2056989019012581
    In the title tri-substituted thio-urea derivative, C13H18N2O3S, the thione-S and carbonyl-O atoms lie, to a first approximation, to the same side of the mol-ecule [the S-C-N-C torsion angle is -49.3 (2)°]. The CN2S plane is almost planar (r.m.s. deviation = 0.018 Å) with the hy-droxy-ethyl groups lying to either side of this plane. One hy-droxy-ethyl group is orientated towards the thio-amide functionality enabling the formation of an intra-molecular N-H⋯O hydrogen bond leading to an S(7) loop. The dihedral angle [72.12 (9)°] between the planes through the CN2S atoms and the 4-tolyl ring indicates the mol-ecule is twisted. The experimental mol-ecular structure is close to the gas-phase, geometry-optimized structure calculated by DFT methods. In the mol-ecular packing, hydroxyl-O-H⋯O(hydrox-yl) and hydroxyl-O-H⋯S(thione) hydrogen bonds lead to the formation of a supra-molecular layer in the ab plane; no directional inter-actions are found between layers. The influence of the specified supra-molecular inter-actions is apparent in the calculated Hirshfeld surfaces and these are shown to be attractive in non-covalent inter-action plots; the inter-action energies point to the important stabilization provided by directional O-H⋯O hydrogen bonds.
  10. Fulltext A 1:1:1 co-crystal solvate comprising 2,2'-di-thiodi-benzoic acid, 2-chloro-benzoic acid and N,N-di-methyl-formamide: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 Apr 01;75(Pt 4):475-481.
    PMID: 31161060 DOI: 10.1107/S205698901900375X
    The asymmetric unit of the three-component title compound, 2,2'-di-thiodi-benzoic acid-2-chloro-benzoic acid-N,N-di-methyl-formamide (1/1/1), C14H10O4S2·C7H5ClO2·C3H7NO, contains a mol-ecule each of 2,2'-di-thiodi-benzoic acid (DTBA), 2-chloro-benzoic acid (2CBA) and di-methyl-formamide (DMF). The DTBA mol-ecule is twisted [the C-S-S-C torsion angle is 88.37 (17)°] and each carb-oxy-lic group is slightly twisted from the benzene ring to which it is connected [CO2/C6 dihedral angles = 7.6 (3) and 12.5 (3)°]. A small twist is evident in the mol-ecule of 2CBA [CO2/C6 dihedral angle = 4.4 (4)°]. In the crystal, the three mol-ecules are connected by hydrogen bonds with the two carb-oxy-lic acid residues derived from DTBA and 2CBA forming a non-symmetric eight-membered {⋯HOCO}2 synthon, and the second carb-oxy-lic acid of DTBA linked to the DMF mol-ecule via a seven-membered {⋯HOCO⋯HCO} heterosynthon. The three-mol-ecule aggregates are connected into a supra-molecular chain along the a axis via DTBA-C-H⋯O(hydroxyl-2CBA), 2CBA-C-H⋯O(hydroxyl-DTBA) and DTBA-C-H⋯S(DTBA) inter-actions. Supra-molecular layers in the ab plane are formed as the chains are linked via DMF-C-H⋯S(DTBA) contacts, and these inter-digitate along the c-axis direction without specific points of contact between them. A Hirshfeld surface analysis points to additional but, weak contacts to stabilize the three-dimensional architecture: DTBA-C=O⋯H(phenyl-DTBA), 2CBA-Cl⋯H(phenyl-DTBA), as well as a π-π contact between the delocalized eight-membered {⋯HOC=O}2 carb-oxy-lic dimer and the phenyl ring of 2CBA. The latter was confirmed by electrostatic potential (ESP) mapping.
  11. Fulltext A 1:2 co-crystal of 2,2'-di-thiodi-benzoic acid and benzoic acid: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 Jan 01;75(Pt 1):1-7.
    PMID: 30713723 DOI: 10.1107/S2056989018017097
    The asymmetric unit of the title 1:2 co-crystal, C14H10O4S2·2C7H6O2, comprises half a mol-ecule of di-thiodi-benzoic acid [systematic name: 2-[(2-carb-oxy-phen-yl)disulfan-yl]benzoic acid, DTBA], as the mol-ecule is located about a twofold axis of symmetry, and a mol-ecule of benzoic acid (BA). The DTBA mol-ecule is twisted about the di-sulfide bond [the C-S-S-C torsion angle is -83.19 (8)°] resulting in a near perpendicular relationship between the benzene rings [dihedral angle = 71.19 (4)°]. The carb-oxy-lic acid group is almost co-planar with the benzene ring to which it is bonded [dihedral angle = 4.82 (12)°]. A similar near co-planar relationship pertains for the BA mol-ecule [dihedral angle = 3.65 (15)°]. Three-mol-ecule aggregates are formed in the crystal whereby two BA mol-ecules are connected to a DTBA mol-ecule via hy-droxy-O-H⋯O(hydroxy) hydrogen bonds and eight-membered {⋯HOC=O}2 synthons. These are connected into a supra-molecular layer in the ab plane through C-H⋯O inter-actions. The inter-actions between layers to consolidate the three-dimensional architecture are π-π stacking inter-actions between DTBA and BA rings [inter-centroid separation = 3.8093 (10) Å] and parallel DTBA-hy-droxy-O⋯π(BA) contacts [O⋯ring centroid separation = 3.9049 (14) Å]. The importance of the specified inter-actions as well as other weaker contacts, e.g. π-π and C-H⋯S, are indicated in the analysis of the calculated Hirshfeld surface and inter-action energies.
  12. Utilizing Hirshfeld surface calculations, non-covalent inter-action (NCI) plots and the calculation of inter-action energies in the analysis of mol-ecular packing
    Tan SL, Jotani MM, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 Mar 01;75(Pt 3):308-318.
    PMID: 30867939 DOI: 10.1107/S2056989019001129
    The analysis of atom-to-atom and/or residue-to-residue contacts remains a favoured mode of analysing the mol-ecular packing in crystals. In this contribution, additional tools are highlighted as methods for analysis in order to complement the 'crystallographer's tool', PLATON [Spek (2009). Acta Cryst. D65, 148-155]. Thus, a brief outline of the procedures and what can be learned by using Crystal Explorer [Spackman & Jayatilaka (2009). CrystEngComm11, 19-23] is presented. Attention is then directed towards evaluating the nature, i.e. attractive/weakly attractive/repulsive, of specific contacts employing NCIPLOT [Johnson et al. (2010). J. Am. Chem. Soc. 132, 6498-6506]. This is complemented by a discussion of the calculation of energy frameworks utilizing the latest version of Crystal Explorer. All the mentioned programs are free of charge and straightforward to use. More importantly, they complement each other to give a more complete picture of how mol-ecules assemble in mol-ecular crystals.
  13. A monoclinic polymorph of [(Z)-N-(3-chloro-phen-yl)-O-methyl-thio-carbamato-κS](tri-phenyl-phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis
    Yeo CI, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Aug 1;72(Pt 8):1068-73.
    PMID: 27536384 DOI: 10.1107/S2056989016010781
    The title compound, [Au(C8H7ClNOS)(C18H15P)], is a monoclinic (P21/n, Z' = 1; form β) polymorph of the previously reported triclinic form (P-1, Z' = 1; form α) [Tadbuppa & Tiekink (2010 ▸). Acta Cryst. E66, m664]. The mol-ecular structures of both forms feature an almost linear gold(I) coordination geometry [P-Au-S = 175.62 (5)° in the title polymorph], being coordinated by thiol-ate S and phosphane P atoms, a Z conformation about the C=N bond and an intra-molecular Au⋯O contact. The major conformational difference relates to the relative orientations of the residues about the Au-S bond: the P-Au-S-C torsion angles are -8.4 (7) and 106.2 (7)° in forms α and β, respectively. The mol-ecular packing of form β features centrosymmetric aggregates sustained by aryl-C-H⋯O inter-actions, which are connected into a three-dimensional network by aryl-C-H⋯π contacts. The Hirshfeld analysis of forms α and β shows many similarities with the notable exception of the influence of C-H⋯O inter-actions in form β.
  14. Zwitterionic 4-bromo-6-meth-oxy-2-{[tris-(hy-droxy-meth-yl)methyl]-iminiumyl-meth-yl}phenolate: crystal structure and Hirshfeld surface analysis
    Lee SM, Lo KM, Tan SL, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Aug 1;72(Pt 8):1223-7.
    PMID: 27536419 DOI: 10.1107/S2056989016012159
    In the solid state, the title compound, C12H16BrNO5 [systematic name: 4-bromo-2-((1E)-{[1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-yl]iminium-yl}meth-yl)-6-meth-oxy-benzen-1-olate], C12H16BrNO5, is found in the keto-amine tautomeric form, with an intra-molecular iminium-N-H⋯O(phenolate) hydrogen bond and an E conformation about the C=N bond. Both gauche (two) and anti relationships are found for the methyl-hydroxy groups. In the crystal, a supra-molecular layer in the bc plane is formed via hy-droxy-O-H⋯O(hy-droxy) and charge-assisted hy-droxy-O-H⋯O(phenolate) hydrogen-bonding inter-actions; various C-H⋯O inter-actions provide additional cohesion to the layers, which stack along the a axis with no directional inter-actions between them. A Hirshfeld surface analysis confirms the lack of specific inter-actions in the inter-layer region.
  15. [N,N-Bis(2-hy-droxy-eth-yl)di-thio-carbamato-κ2S,S']bis-(tri-phenyl-phosphane-κP)copper(I) chloro-form monosolvate: crystal structure, Hirshfeld surface analysis and solution NMR measurements
    Tan SL, Yeo CI, Heard PJ, Akien GR, Halcovitch NR, Tiekink ER
    Acta Crystallogr E Crystallogr Commun, 2016 Dec 01;72(Pt 12):1799-1805.
    PMID: 27980834
    The title compound, [Cu(C5H5NO2S2)(C18H15P)2]·CHCl3, features a tetra-hedrally coordinated CuI atom within a P2S2 donor set defined by two phosphane P atoms and by two S atoms derived from a symmetrically coordinating di-thio-carbamate ligand. Both intra- and inter-molecular hy-droxy-O-H⋯O(hydroxy) hydrogen bonding is observed: the former closes an eight-membered {⋯HOC2NC2O} ring, whereas the latter connects centrosymmetrically related mol-ecules into dimeric aggregates via eight-membered {⋯H-O⋯H-O}2 synthons. The complex mol-ecules are arranged to form channels along the c axis in which reside the chloro-form mol-ecules, being connected by Cl⋯π(arene) and short S⋯Cl [3.3488 (9) Å] inter-actions. The inter-molecular inter-actions have been investigated further by Hirshfeld surface analysis, which shows the conventional hydrogen bonding to be very localized with the main contributors to the surface, at nearly 60%, being H⋯H contacts. Solution NMR studies indicate that whilst the same basic mol-ecular structure is retained in solution, the tri-phenyl-phosphane ligands are highly labile, exchanging rapidly with free Ph3P at room temperature.
  16. Fulltext N,N'-Bis(pyridin-4-ylmeth-yl)oxalamide benzene monosolvate: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Halcovitch NR, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2019 Aug 01;75(Pt 8):1133-1139.
    PMID: 31417779 DOI: 10.1107/S2056989019009551
    The asymmetric unit of the title 1:1 solvate, C14H14N4O2·C6H6 [systematic name of the oxalamide mol-ecule: N,N'-bis-(pyridin-4-ylmeth-yl)ethanedi-amide], comprises a half mol-ecule of each constituent as each is disposed about a centre of inversion. In the oxalamide mol-ecule, the central C2N2O2 atoms are planar (r.m.s. deviation = 0.0006 Å). An intra-molecular amide-N-H⋯O(amide) hydrogen bond is evident, which gives rise to an S(5) loop. Overall, the mol-ecule adopts an anti-periplanar disposition of the pyridyl rings, and an orthogonal relationship is evident between the central plane and each terminal pyridyl ring [dihedral angle = 86.89 (3)°]. In the crystal, supra-molecular layers parallel to (10) are generated owing the formation of amide-N-H⋯N(pyrid-yl) hydrogen bonds. The layers stack encompassing benzene mol-ecules which provide the links between layers via methyl-ene-C-H⋯π(benzene) and benzene-C-H⋯π(pyrid-yl) inter-actions. The specified contacts are indicated in an analysis of the calculated Hirshfeld surfaces. The energy of stabilization provided by the conventional hydrogen bonding (approximately 40 kJ mol-1; electrostatic forces) is just over double that by the C-H⋯π contacts (dispersion forces).
  17. Fulltext 4-[(1E)-({[(Benzyl-sulfan-yl)methane-thio-yl]amino}-imino)-meth-yl]benzene-1,3-diol chloro-form hemisolvate: crystal structure, Hirshfeld surface analysis and computational study
    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. Fulltext 2,2'-(Disulfanedi-yl)di-benzoic acid N,N-di-methyl-formamide monosolvate: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2020 Jul 01;76(Pt 7):1150-1157.
    PMID: 32695471 DOI: 10.1107/S2056989020008257
    The title 1:1 solvate, C14H10O4S2·C3H7NO, features a twisted mol-ecule of 2,2'-di-thiodi-benzoic acid (DTBA), with the central C-S-S-C torsion angle being -88.57 (6)°, and a mol-ecule of di-methyl-formamide (DMF). The carb-oxy-lic acid groups are, respectively, close to co-planar and twisted with respect to the benzene rings to which they are connected as seen in the CO2/C6 torsion angles of 1.03 (19) and 7.4 (2)°. Intra-molecular, hypervalent S←O inter-actions are noted [S⋯O = 2.6140 (9) and 2.6827 (9) Å]. In the crystal, four-mol-ecule aggregates are formed via DTBA-O-H⋯O(DMF) and DTBA-O-H⋯O(DTBA) hydrogen bonding, the latter via an eight-membered {⋯OHCO}2 homosynthon. These are linked into supra-molecular layers parallel to (011) via benzene-C-H⋯O(DTBA) and DTBA-C=O⋯π(benzene) inter-actions, with the connections between these, giving rise to a three-dimensional architecture, being of the type benzene-C-H⋯π(benzene). An analysis of the calculated Hirshfeld surfaces indicates, in addition to the aforementioned inter-molecular contacts, the presence of stabilizing inter-actions between a benzene ring and a quasi-π-system defined by O-H⋯O hydrogen bonds between a DTBA dimer, i.e. the eight-membered {⋯OCOH}2 ring system, and between a benzene ring and a quasi-π(OCOH⋯OCH) system arising from the DTBA-O-H⋯O(DMF) hydrogen bond. The inter-centroid separations are 3.65 and 3.49 Å, respectively.
  19. Fulltext N,N'-Bis(pyridin-3-ylmeth-yl)ethanedi-amide monohydrate: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2020 Jan 01;76(Pt 1):25-31.
    PMID: 31921447 DOI: 10.1107/S2056989019016153
    The mol-ecular structure of the title bis-pyridyl substituted di-amide hydrate, C14H14N4O2·H2O, features a central C2N2O2 residue (r.m.s. deviation = 0.0205 Å) linked at each end to 3-pyridyl rings through methyl-ene groups. The pyridyl rings lie to the same side of the plane, i.e. have a syn-periplanar relationship, and form dihedral angles of 59.71 (6) and 68.42 (6)° with the central plane. An almost orthogonal relationship between the pyridyl rings is indicated by the dihedral angle between them [87.86 (5)°]. Owing to an anti disposition between the carbonyl-O atoms in the core, two intra-molecular amide-N-H⋯O(carbon-yl) hydrogen bonds are formed, each closing an S(5) loop. Supra-molecular tapes are formed in the crystal via amide-N-H⋯O(carbon-yl) hydrogen bonds and ten-membered {⋯HNC2O}2 synthons. Two symmetry-related tapes are linked by a helical chain of hydrogen-bonded water mol-ecules via water-O-H⋯N(pyrid-yl) hydrogen bonds. The resulting aggregate is parallel to the b-axis direction. Links between these, via methyl-ene-C-H⋯O(water) and methyl-ene-C-H⋯π(pyrid-yl) inter-actions, give rise to a layer parallel to (10); the layers stack without directional inter-actions between them. The analysis of the Hirshfeld surfaces point to the importance of the specified hydrogen-bonding inter-actions, and to the significant influence of the water mol-ecule of crystallization upon the mol-ecular packing. The analysis also indicates the contribution of methyl-ene-C-H⋯O(carbon-yl) and pyridyl-C-H⋯C(carbon-yl) contacts to the stability of the inter-layer region. The calculated inter-action energies are consistent with importance of significant electrostatic attractions in the crystal.
  20. Fulltext The 1:2 co-crystal formed between N,N'-bis(pyridin-4-ylmeth-yl)ethanedi-amide and benzoic acid: crystal structure, Hirshfeld surface analysis and computational study
    Tan SL, Tiekink ERT
    Acta Crystallogr E Crystallogr Commun, 2020 Jan 01;76(Pt 1):102-110.
    PMID: 31921461 DOI: 10.1107/S2056989019016840
    The crystal and mol-ecular structures of the title 1:2 co-crystal, C14H14N4O2·2C7H6O2, are described. The oxalamide mol-ecule has a (+)-anti-periplanar conformation with the 4-pyridyl residues lying to either side of the central, almost planar C2N2O2 chromophore (r.m.s. deviation = 0.0555 Å). The benzoic acid mol-ecules have equivalent, close to planar conformations [C6/CO2 dihedral angle = 6.33 (14) and 3.43 (10)°]. The formation of hy-droxy-O-H⋯N(pyrid-yl) hydrogen bonds between the benzoic acid mol-ecules and the pyridyl residues of the di-amide leads to a three-mol-ecule aggregate. Centrosymmetrically related aggregates assemble into a six-mol-ecule aggregate via amide-N-H⋯O(amide) hydrogen bonds through a 10-membered {⋯HNC2O}2 synthon. These are linked into a supra-molecular tape via amide-N-H⋯O(carbon-yl) hydrogen bonds and 22-membered {⋯HOCO⋯NC4NH}2 synthons. The contacts between tapes to consolidate the three-dimensional architecture are of the type methyl-ene-C-H⋯O(amide) and pyridyl-C-H⋯O(carbon-yl). These inter-actions are largely electrostatic in nature. Additional non-covalent contacts are identified from an analysis of the calculated Hirshfeld surfaces.
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