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1.  Spontaneous echo contrast masking thrombus in giant left atrium of mitral stenosis-a dilemma in clinical diagnosis 
Pakistan Journal of Medical Sciences  2015;31(5):1283-1285.
Spontaneous echo contrast (SEC) and thrombus in enlarged left atrium (LA) are common in mitral valvular disease (MVD) and SEC is considered to be a prethrombotic condition. Reliable exclusion of LA thrombus is important before any definitive curative attempts like percutaneous transluminal mitral commissurotomy (PTMC), closed mitral commissurotomy (CMC) or innovative therapies like pulmonary vein isolation and percutaneous closure of the LA appendage. Echocardiography, particularly the transesophageal echocardiography (TEE) is considered to be the gold standard for the diagnosis and to exclude LA thrombus. However, LA thrombus may remain rarely undetected even by TEE potentially making the interventions a risky job. We present a case of mitral stenosis (MS) with giant LA where profuse, dense SEC masked the underlying thrombus in the LA cavity.
PMCID: PMC4641301  PMID: 26649032
Mitral stenosis; Left atrium; Thrombus; Transesophageal echocardiography
2.  Comparative evaluation of chromogenic agar medium and conventional culture system for isolation and presumptive identification of uropathogens 
Pakistan Journal of Medical Sciences  2014;30(5):1033-1038.
Objective: Urine is the most frequent specimen received for culture/sensitivity by clinical laboratories. The microbiological performance of HiCrome UTI agar medium was compared with Blood agar and MacConkey agar for isolation and presumptive identification of bacteria from urine culture.
Methods: A total of 443 consecutively collected midstream and/or catheter-catch urine samples from patients attending the Islami Bank Medical College Hospital, Rajshahi, Bangladesh during January to December, 2012 were cultured. Urine samples showing pus cells ≥ 5/HPF were inoculated on to Blood agar (BA), MacConkey agar (MAC) and HiCrome UTI agar (CA) media simultaneously and incubated overnight aerobically at 370C. Rate of isolation and presumptive identification of bacterial species were compared for different media.
Results: Culture yielded a total of 199 bacterial isolates from 189 (42.67%) positive plates including 179 (40.40%) unimicrobial and 10 (2.26%) polymicrobial (mixed growth of pair of bacteria) growths. Both HiCrome UTI agar and Blood agar media supported 100% growths while 151 (75.88%) growths were observed on MacConkey agar. The rate of presumptive identification was found significantly higher on HiCrome UTI agar (97.49%) than MAC agar (67.34%) (P<0.001) as primary urine culture medium. Of 199 isolates, E. coli was found to be the leading uropathogen isolated from 118 (59.30%) samples with its presumptive identification rate of 95.76%, 93.22% and 5.93% on CA, MAC and BA respectively. All 10 (100%) polymicrobial growths were demonstrated distinctly on CA against only 01(10%) on each BA and MAC.
Conclusion: HiCrome UTI agar was found to be more useful as primary urine culture medium in both higher rate of isolation and presumptive identification of uropathogens in comparison to conventional media. Its inherent characteristics in demonstrating polymicrobial growth and ease of rapid identification by distinct colony colour are unique.
PMCID: PMC4163227  PMID: 25225521
Urine culture; Chromogenic agar medium; Conventional culture system; Rate of isolation; Presumptive identification
3.  Evaluation of diagnostic performance of rK28 ELISA using urine for diagnosis of visceral leishmaniasis 
Parasites & Vectors  2016;9:383.
Recombinant fusion proteins are now commonly used to detect circulating antibodies for the serodiagnosis of visceral leishmaniasis (VL) in Asia, Africa and the Americas. Although simple, these tests still require blood collection and their use in remote settings can be limited due to the need of collection devices, serum fractionation instrument and generation of biohazardous waste. The development of an accurate and non-invasive diagnostic algorithm for VL, such as could be achieved with urine, is desirable.
We enrolled 87 VL patients and 81 non-VL individuals, including 33 healthy endemic controls, 16 healthy non-endemic controls, 16 disease controls and 16 tuberculosis (TB) patients. We compared the efficacy of recombinant antigens rK28, rK39 and rKRP42 for the diagnosis of VL when either serum or urine were used to develop antibody-detection ELISA.
As expected, each of the antigens readily detected antibodies in the serum of VL patients. rK28 ELISA showed the highest sensitivity (98.9 %), followed by rK39 and rKRP42 ELISA (97.7 and 94.4 %, respectively); overall specificity was > 96 %. When urine was used as the test analyte, only a marginal drop in sensitivity was observed, with rK28 ELISA again demonstrating the greatest sensitivity (95.4 %), followed by rK39 and rKRP42 ELISA, respectively. Again, the overall specificity was > 96 %.
Our data indicate the potential for using urine in the diagnosis of VL. Detection of antibodies against rK28 demonstrated the greatest sensitivity. Together, our results indicate that rK28-based antibody detection tests using urine could provide a completely non-invasive tool amenable for diagnosis of VL in remote locations.
Electronic supplementary material
The online version of this article (doi:10.1186/s13071-016-1667-2) contains supplementary material, which is available to authorized users.
PMCID: PMC4932727  PMID: 27377266
Visceral leishmaniasis; Diagnosis; rK28; rK39; rKRP42; ELISA; Serum; Urine; Bangladesh
4.  Development and comparative evaluation of two antigen detection tests for Visceral Leishmaniasis 
BMC Infectious Diseases  2015;15:384.
Visceral leishmaniasis (VL) can be fatal without timely diagnosis and treatment. Treatment efficacies vary due to drug resistance, drug toxicity and co-morbidities. It is important to monitor treatment responsiveness to confirm cure and curtail relapse. Currently, microscopy of spleen, bone marrow or lymph node biopsies is the only definitive method to evaluate cure. A less invasive test for treatment success is a high priority for VL management.
In this study, we describe the development of a capture ELISA based on detecting Leishmania donovani antigens in urine samples and comparison with the Leishmania Antigen ELISA, also developed for the same purpose. Both were developed as prototype kits and tested on patient urine samples from Sudan, Ethiopia, Bangladesh and Brazil, along with appropriate control samples from endemic and non-endemic regions. Sensitivity and specificity were assessed based on accurate detection of patients compared to control samples. One- Way ANOVA was used to assess the discrimination capacity of the tests and Cohen’s kappa was used to assess their correlation.
The Leishmania Antigen Detect™ ELISA demonstrated >90 % sensitivity on VL patient samples from Sudan, Bangladesh and Ethiopia and 88 % on samples from Brazil. The Leishmania Antigen ELISA was comparable in performance except for lower sensitivity on Sudanese samples. Both were highly specific. To confirm utility in monitoring treatment, urine samples were collected from VL patients at days 0, 30 and 180 post- treatment. For the Leishmania Antigen Detect™ ELISA, positivity was high at day 0 at 95 %, falling to 21 % at day 30. At day 180, all samples were negative, corresponding well with clinical cure. A similar trend was also seen for the Leishmania Antigen ELISA albeit; with lower positivity of 91 % at Day 0 and more patients, remaining positive at Days 30 and 180.
The Leishmania Antigen Detect™ and the Leishmania Antigen ELISAs are standardized, user- friendly, quantitative and direct tests to detect Leishmania during acute VL as well as to monitor parasite clearance during treatment. They are a clear improvement over existing options.
The ELISAs provide a non-invasive method to detect parasite antigens during acute infection and monitor its clearance upon cure, filling an unmet need in VL management. Further refinement of the tests with more samples from endemic regions will define their utility in monitoring treatment.
PMCID: PMC4580298  PMID: 26395447
Diagnosis; Leishmania; Antigen; Treatment; Antibody; Kala azar; Infection
5.  Prevalence and susceptibility of uropathogens: a recent report from a teaching hospital in Bangladesh 
BMC Research Notes  2015;8:416.
This investigation was aimed to determine the current status of prevalence and antimicrobial susceptibility of uropathogens isolated in a teaching hospital in Bangladesh. A retrospective analysis was done at the department of Microbiology of Islami Bank Medical College, Rajshahi (IBMCR), Bangladesh during January to December, 2012. Midstream clean-catch urine samples were collected from 443 suspected urinary tract infection patients of different age and sex groups. Uropathogens were identified by standard and specific microbiological techniques and antimicrobial susceptibility pattern was determined by Kirby Bauer Disc diffusion method following Clinical and Laboratory Standards Institute (CLSI) guidelines.
Culture yielded a total of 189 (42.66 %) significant growths of uropathogens including 179 (94.71 %) unimicrobial (single bacterial species) and 10 (5.29 %) polymicrobial (pair of two different bacterial species) growths. Gender distribution showed 34.44 % male and 48.29 % female UTI patients with male to female ratio of 1:1.46, respectively. E. coli was the predominant isolate (59.30 %), followed by Staph saprophyticus (19.09 %), Enterococcus spp. (11.56 %), Klebsiella spp. (5.53 %), Pseudomonas spp. (2.01 %), Proteus spp. (1.51 %) and Enterobacter spp. (1.00 %). Very high frequency of resistance ranging from 72.03 to 91.53 % to cotrimoxazole, ciprofloxacin, cefuroxime, cephradin, amoxicillin and nalidixic acid, moderately high resistance to ceftriaxone (55.08 %) and gentamicin (40.68 %) and low resistance to nitrofurantoin (16.10 %) were shown by E. coli. Similarly, Staph. saprophyticus and Enterococcus spp. showed low resistance (18.42 and 21.74 %) to nitrofurantoin, but moderately high against cefaclor, gentamycin, cefuroxime and ceftriaxone. Klebsiella spp. and Proteus spp. were 72.73 and 66.67 % susceptible, respectively to gentamycin only but low frequency of susceptibility (<50 %) was found to all other antimicrobial agents. Peudomonas spp. was 75 % susceptible to nitrofurantoin only and showed 75–100 % resistance to all other agents. Enterobacter spp. were 50 % resistant to nitrofurantoin, gentamycin, cefuroxime, cefaclor and ceftriaxone but showed 100 % resistance to all remaining antimicrobials.
Current uropathogens showed the highest rate of susceptibility to nitrofurantoin and gentamicin which can be adapted for empirical treatment of urinary tract infections.
PMCID: PMC4560919  PMID: 26342570
UTI; Uropathogens; Antibiogram; Teaching hospital; Bangladesh
6.  Amebic liver abscess in northern region of Bangladesh: sociodemographic determinants and clinical outcomes 
BMC Research Notes  2014;7:625.
Amebic liver abscess (ALA) is endemic in Bangladesh since historical age but its epidemiology and sociodemographic determinants are not well described in the literatures. This paper focuses on the endemicity, sociodemographic determinants and clinical outcomes of ALA patients from certain northern districts in Bangladesh. Ninety hospitalized ALA patients enrolled from 6 northern districts of Bangladesh during July 2008 to June 2010 were analyzed.
Clinical presentations of ALA was initially substantiated by ultrasound imaging and later confirmed by detection of small subunit rRNA gene of E. histolytica using a Real Time PCR. Structured questionnaire and data sheet were used to record sociodemographic characteristics, clinical presentations and outcomes. Patients were followed for immediate and late treatment outcomes up to 2 years since diagnosis. Northern districts those situated on the Ganges basin were noted as endemic areas. Male significantly outnumbered the female with a male to female ratio of 21:1 and majority of patients (58%) were in their 3rd and 4th decades. A significant (21%) number of patients were aborigines despite their ethnic minority as population under investigation and overall 68% belonged to low socioeconomic group. Habit of indigenous alcohol consumption was very high (78%) among ALA patients with overwhelming majority was illiterate (74.44%) and from rural population (70%). Fever with right hypochondriac pain of variable duration was the principal presenting complains. Gross fluid derangements including pleural effusion, edema and ascities were observed in 39% cases and 6% had rupture of abscess. All patients were treated with standard antimicrobial regimen and discharged with initial recovery. Recurrent attack was observed in 6% cases and 3 (3.33%) patients died during 2 years follow-up period. Complicated (37.78%) ALA patients showed significant Odds ratio (P < 0.05) for major sociodemographic determinants in comparison to non-complicated patients.
Amebic liver abscess is endemic in certain northern districts of Bangladesh especially on the Ganges basin with relatively high prevalence among aborigines. Rural habitat, ethnicity (Aborigine) and habit of indigenous alcohol consumption were found to be strong determinants, especially for complicated ALA, which were associated with different grades of morbidity and a few mortalities.
PMCID: PMC4169810  PMID: 25204395
Amebic liver abscess; E. histolytica; Sociodemographic determinants; Clinical outcomes; Bangladesh
7.  Exact traveling wave solutions of modified KdV–Zakharov–Kuznetsov equation and viscous Burgers equation 
SpringerPlus  2014;3:105.
Mathematical modeling of many physical systems leads to nonlinear evolution equations because most physical systems are inherently nonlinear in nature. The investigation of traveling wave solutions of nonlinear partial differential equations (NPDEs) plays a significant role in the study of nonlinear physical phenomena. In this article, we construct the traveling wave solutions of modified KDV-ZK equation and viscous Burgers equation by using an enhanced (G '/G) -expansion method. A number of traveling wave solutions in terms of unknown parameters are obtained. Derived traveling wave solutions exhibit solitary waves when special values are given to its unknown parameters.
Mathematics subject classification
35C07; 35C08; 35P99
PMCID: PMC3946109  PMID: 24616841
Enhanced (G '/G)-expansion method; Modified KDV-ZK equation; Viscous burgers equation; Traveling wave; Solitary wave
8.  Brugada syndrome with a novel missense mutation in SCN5A gene: A case report from Bangladesh 
Indian Heart Journal  2014;66(1):104-107.
Brugada syndrome is an inherited cardiac arrhythmia that follows autosomal dominant transmission and can cause sudden death. We report a case of Brugada syndrome in a 55-year-old male patient presented with recurrent palpitation, atypical chest pain and presyncope. ECG changes were consistent with type 1 Brugada. Gene analysis revealed a novel missense mutation in SCN5A gene with a genetic variation of D785N and a nucleotide change at 2353G-A. One of his children also had the same mutation. To our knowledge this is the first genetically proved case of Brugada syndrome in Bangladesh.
PMCID: PMC3946469  PMID: 24581105
Brugada syndrome; SCN5A gene; Novel missense mutation; Bangladesh
9.  2-[(1,3-Benzo­thia­zol-2-yl)imino­meth­yl]-6-meth­oxy­phenol: a new monoclinic polymorph 
The title compound, C15H12N2O2S, is a P21/c polymorph of a previously reported P21/n polymorph [Büyükgüngör et al. (2004 ▶). Acta Cryst. E60, o1414–o1416]. The dihedral angle between the benzo­thia­zole (r.m.s. deviation = 0.010 Å) and the benzene ring of 7.86 (6)° compares with 10.76 (10)° in the literature structure. The meth­oxy substituent is almost coplanar with the benzene ring to which it is attached [C—O—C—C torsion angle = 178.31 (14)°] and the conformation about the imine bond [1.287 (2) Å] is E. There is an intra­molecular O—H⋯N hydrogen bond and the hy­droxy O and thio­ether S atoms are syn. In the crystal, columns are formed along the b axis as centrosymmetric dimeric aggregates, mediated by C—H⋯O inter­actions and linked by π–π inter­actions between the thia­zole and benzene rings [centroid-to-centroid distance = 3.8256 (10) Å].
PMCID: PMC3793768  PMID: 24109355
10.  Detection of extended spectrum β-lactamase in Pseudomonas spp. isolated from two tertiary care hospitals in Bangladesh 
BMC Research Notes  2013;6:7.
Extended spectrum ß-lactamases (ESBLs) represent a major group of lactamases responsible for resistance, mostly produced by gram-negative bacteria, to newer generations of ß-lactam drugs currently being identified in large numbers worldwide. The present study was undertaken to see the frequency of ESBL producing Pseudomonas spp. isolated from six hundred clinical specimens (wound, pus, aural, urine, sputum, throat and other swabs) collected over a period of three years from two tertiary care hospitals in Bangladesh.
Aerobic bacterial culture was performed on aseptically collected swabs and only growth of Pseudomonas was considered for further species identification and ESBL production along with serotyping of Pseudomonas aeruginosa. Antimicrobial susceptibility testing was carried out using the Kirby-Bauer agar diffusion method and ESBL production was detected on Mueller Hinton agar by double-disk synergy technique using Amoxicillin-Clavulanic acid with Ceftazidime, Cefotaxime, Ceftriaxone and Aztreonam. Culture yielded 120 Pseudomonas spp. and 82 of them were biochemically characterized for species. Pseudomonas aeruginosa was found to be the predominant (90.2%) species. Of 82 isolates tested for ESBL, 31 (37.8%) were ESBL positive with 29 (93.5%) as Pseudomonas aeruginosa, the remaining 2 (6.5%) were Stenotrophomonas maltophilia and Ralstonia pickettii. Antibiogram revealed Imipenem as the most effective drug (93.3%) among all antimicrobials used against Pseudomonas spp. followed by Aminoglycosides (63.7%).
ESBL producing Pseudomonas spp. was found to be a frequent isolate from two tertiary care hospitals in Bangladesh, showing limited susceptibility to antimicrobials and decreased susceptibility to Imipenem in particular, which is a matter of great concern.
PMCID: PMC3543721  PMID: 23289861
Pseudomonas spp; Antimicrobial susceptibility; ESBL
11.  Diagnostic accuracy of loop-mediated isothermal amplification (LAMP) for detection of Leishmania DNA in buffy coat from visceral leishmaniasis patients 
Parasites & Vectors  2012;5:280.
Visceral leishmaniasis (VL) remains as one of the most neglected tropical diseases with over 60% of the world’s total VL cases occurring in the Indian subcontinent. Due to the invasive risky procedure and technical expertise required in the classical parasitological diagnosis, the goal of the VL experts has been to develop noninvasive procedure(s) applicable in the field settings. Several serological and molecular biological approaches have been developed over the last decades, but only a few are applicable in field settings that can be performed with relative ease. Recently, loop-mediated isothermal amplification (LAMP) has emerged as a novel nucleic acid amplification method for diagnosis of VL. In this study, we have evaluated the LAMP assay using buffy coat DNA samples from VL patients in Bangladesh and compared its performance with leishmania nested PCR (Ln-PCR), an established molecular method with very high diagnostic indices.
Seventy five (75) parasitologically confirmed VL patients by spleen smear microcopy and 101 controls (endemic healthy controls −25, non-endemic healthy control-26, Tuberculosis-25 and other diseases-25) were enrolled in this study. LAMP assay was carried out using a set of four primers targeting L. donovani kinetoplast minicircle DNA under isothermal (62 °C) conditions in a heat block. For Ln-PCR, we used primers targeting the parasite’s small-subunit rRNA region.
LAMP assay was found to be positive in 68 of 75 confirmed VL cases, and revealed its diagnostic sensitivity of 90.7% (95.84-81.14, 95% CI), whereas all controls were negative by LAMP assay, indicating a specificity of 100% (100–95.43, 95% CI). The Ln-PCR yielded a sensitivity of 96% (98.96-87.97, 95% CI) and a specificity of 100% (100–95.43, 95% CI).
High diagnostic sensitivity and excellent specificity were observed in this first report of LAMP diagnostic evaluation from Bangladesh. Considering its many fold advantages over conventional PCR and potential to be used as a simple and rapid test in the VL endemic areas of the Indian subcontinent, our findings are encouraging, but further evaluation of LAMP is needed.
PMCID: PMC3545740  PMID: 23206441
LAMP; Visceral leishmaniasis; Diagnosis; PCR; Bangladesh
12.  Recent outbreak of cutaneous anthrax in Bangladesh: clinico-demographic profile and treatment outcome of cases attended at Rajshahi Medical College Hospital 
BMC Research Notes  2012;5:464.
Human cutaneous anthrax results from skin exposure to B. anthracis, primarily due to occupational exposure. Bangladesh has experienced a number of outbreaks of cutaneous anthrax in recent years. The last episode occurred from April to August, 2011 and created mass havoc due to its dreadful clinical outcome and socio-cultural consequences. We report here the clinico-demographic profile and treatment outcome of 15 cutaneous anthrax cases attended at the Dermatology Outpatient Department of Rajshahi Medical College Hospital, Bangladesh between April and August, 2011 with an aim to create awareness for early case detection and management.
Anthrax was suspected primarily based on cutaneous manifestations of typical non-tender ulcer with black eschar, with or without oedema, and a history of butchering, or dressing/washing of cattle/goat or their meat. Diagnosis was established by demonstration of large gram-positive rods, typically resembling B. anthracis under light microscope where possible and also by ascertaining therapeutic success. The mean age of cases was 21.4 years (ranging from 3 to 46 years), 7 (46.7%) being males and 8 (53.3%) females. The majority of cases were from lower middle socioeconomic status. Types of exposures included butchering (20%), contact with raw meat (46.7%), and live animals (33.3%). Malignant pustule was present in upper extremity, both extremities, face, and trunk at frequencies of 11 (73.3%), 2 (13.3%), 1 (6.7%) and 1 (6.7%) respectively. Eight (53.3%) patients presented with fever, 7 (46.7%) had localized oedema and 5 (33.3%) had regional lymphadenopathy. Anthrax was confirmed in 13 (86.7%) cases by demonstration of gram-positive rods. All cases were cured with 2 months oral ciprofloxacin combined with flucoxacillin for 2 weeks.
We present the findings from this series of cases to reinforce the criteria for clinical diagnosis and to urge prompt therapeutic measures to treat cutaneous anthrax successfully to eliminate the unnecessary panic of anthrax.
PMCID: PMC3493280  PMID: 22929128
Cutaneous anthrax; Clinico-demographic profile; Therapeutic response; Bangladesh
13.  n-Butyldichlorido{4-cyclo­hexyl-1-[1-(pyridin-2-yl-κN)ethyl­idene]thio­semi­carb­azi­dato-κ2 N 1,S}tin(IV) 
Two independent mol­ecules comprise the asymmetric unit in the title compound, [Sn(C4H9)(C14H19N4S)Cl2]. In each mol­ecule, the SnIV atom exists within a distorted octa­hedral geometry defined by the N,N′,S-tridentate mono-deprotonated Schiff base ligand, two mutually trans Cl atoms, and the α-C atom of the n-butyl group; the latter is trans to the azo-N atom. The greatest distortion from the ideal geometry is found in the nominally trans angle formed by the S and pyridyl-N atoms at Sn [151.72 (7) and 152.04 (7)°, respectively]. In the crystal, mol­ecules are consolidated into a three-dimensional architecture by a combination of N—H⋯Cl, C—H⋯π and π–π inter­actions [inter-centroid distances = 3.6718 (19) and 3.675 (2) Å].
PMCID: PMC3393180  PMID: 22807748
14.  Chlorido{4-cyclo­hexyl-1-[1-(pyridin-2-yl-κN)ethyl­idene]thio­semicarbazidato-κ2 N 1,S}diphenyl­tin(IV) 
The distorted octa­hedral geometry about the SnIV atom in the title compound, [Sn(C6H5)2(C14H19N4S)Cl], is defined by the N,N,S-tridentate Schiff base ligand, two mutually trans ipso-C atoms of the Sn-bound phenyl groups, and the Cl atom which is trans to the azo N atom. The two five-membered chelate rings and pyridyl ring are almost coplanar with the dihedral angle between the outer five-membered chelate and pyridine rings being 5.39 (8)°. Centrosymmetric dimers feature in the crystal packing mediated by N—H⋯S hydrogen bonds, leading to eight-membered {⋯HNCS}2 synthons. The dimeric aggregates are connected into a three-dimensional architecture by C—H⋯Cl and C—H⋯π inter­actions, as well as π–π inter­actions occurring between centrosymmetrically related pyridine rings [centroid–centroid distance = 3.6322 (13) Å].
PMCID: PMC3343835  PMID: 22589809
15.  (2E)-2-[2-(Cyclo­hexyl­carbamothio­yl)hydrazinylidene]­propanoic acid 
In the title thio­urea derivative, C10H17N3O2S, the carboxyl group and the least-squares plane through the cyclo­hexyl ring are twisted out of the plane through the central CN3S residue; the respective dihedral angles are 7.18 (8) and 62.29 (4)°. The conformation about the azomethine bond [1.275 (2) Å] is E. The NH groups are anti, with one forming an intra­molecular N—H⋯N hydrogen bond. The main feature of the crystal structure is the formation of linear supra­molecular chains along [110] mediated by alternating pairs of O—H⋯O and pairs of N—H⋯S hydrogen bonds.
PMCID: PMC3089072  PMID: 21754495
16.  3-{(E)-[1-(2-Hy­droxy­phen­yl)ethyl­idene]amino}-1-(2-methyl­phen­yl)thio­urea 
In the title thio­urea derivative, C16H17N3OS, the hy­droxy- and methyl-substituted benzene rings form dihedral angles of 9.62 (12) and 55.69 (6)°, respectively, with the central CN3S chromophore (r.m.s. deviation = 0.0117 Å). An intra­molecular O—H⋯N hydrogen bond ensures the coplanarity of the central atoms. The H atoms of the NH groups are syn and the conformation about the N=C double bond [1.295 (4) Å] is E. In the crystal, helical supra­molecular chains sustained primarily by N—H⋯S hydrogen bonds are found. Additional stabilization is provided by C—H⋯π and π–π [ring centroid(hy­droxy­benzene)⋯ring centroid(methyl­benzene) = 3.8524 (18) Å] inter­actions.
PMCID: PMC3089068  PMID: 21754471
17.  1-Cyclo­hexyl-3-{(E)-[1-(pyridin-2-yl)ethyl­idene]amino}­thio­urea 
In the title thio­urea derivative, C14H20N4S, the non-ring non-H atoms are approximately planar, with an r.m.s. deviation of 0.0720 Å. The pyridine ring is twisted out of this plane and makes a dihedral angle of 16.85 (13)° with it. The mean plane passing through the cyclo­hexyl ring is almost normal to the central plane [dihedral angle = 69.23 (8)°]. An intra­molecular N—H⋯N(imine) hydrogen bond occurs. Centrosymmetric dimers are formed in the crystal structure via pairs of N—H⋯S hydrogen bonds, and these are connected into a supra­molecular chain along the a axis via C—H⋯π(pyrid­yl) inter­actions.
PMCID: PMC3099887  PMID: 21754220
18.  Dichlorido{4-cyclo­hexyl-1-[1-(2-pyridyl-κN)ethyl­idene]thio­semicarbazidato-κ2 N 1,S}methyl­tin(IV). Corrigendum 
Corrigendum to Acta Cryst. (2010), E66, m570.
The address of one of the authors in the paper by Salam et al. [Acta Cryst. (2010), E66, m570] is corrected.
PMCID: PMC3050345
19.  Dichlorido{4-cyclo­hexyl-1-[1-(2-pyridyl-κN)ethyl­idene]thio­semicarbazidato-κ2 N 1,S}phenyl­tin(IV) 
The SnIV atom in the title compound, [Sn(C6H5)(C14H19N4S)Cl2], exists within a distorted octa­hedral geometry defined by the N,N′,S-tridentate monodeprotonated Schiff base ligand, two mutually trans Cl atoms, and the ipso-C atom of the Sn-bound phenyl group; the latter is trans to the azo-N atom. The greatest distortion from the ideal geometry is found in the nominally trans angle formed by the S and pyridyl-N atoms at Sn [151.03 (4)°]. With the exception of the cyclo­hexyl group (chair form), the Schiff base ligand is almost planar (r.m.s. deviation of non-H and Sn atoms = 0.053 Å). The nearly orthogonal orientation of the Sn-bound phenyl group [N—Sn—C—C torsion angle = 70.8 (5)°] to the planar portion of the Schiff base allows for the formation of significant intra­molecular C—H⋯Cl inter­actions which preclude the Cl atoms from participating in N—H⋯Cl hydrogen bonds. Instead, C—H⋯π contacts, involving methyl­ene H and the Sn-bound phenyl group, lead to the formation of supra­molecular chains that pack in the bc plane. Connections between these layers are of the type C—H⋯Cl.
PMCID: PMC3011751  PMID: 21589211
20.  Aqua­chlorido{2-[2-(cyclo­hexyl­carbamo­thioyl-κS)hydrazinyl­idene-κN 1]propano­ato(2−)}phenyl­tin(IV) 
In the title organotin compound, [Sn(C6H5)(C10H15N3O2S)Cl(H2O)], the Sn atom is coordinated by the S, O, and imine N atoms of the dinegative tridentate ligand, a chloride ligand, the ipso-C atom of a phenyl ligand and by a water mol­ecule in a distorted octa­hedral coordination environment. Coordin­ated water mol­ecules link the organotin mol­ecules by forming O—H⋯O hydrogen bonds with both carbonyl and carboxyl­ate O atoms, leading to 12-membered {⋯OCO⋯HOH⋯}2 synthons. This results in the formation of supra­molecular chains along the c axis. The chains pack in the ac plane and stack along the b axis with links between layers afforded by N—H⋯Cl hydrogen bonds.
PMCID: PMC3007908  PMID: 21588519
21.  Dichlorido{4-cyclo­hexyl-1-[1-(2-pyridyl-κN)ethyl­idene]thio­semicarbazidato-κ2 N 1,S}methyl­tin(IV) 
The monodeprotonated Schiff base ligand in the title compound, [Sn(CH3)(C14H19N4S)Cl2], N,N′,S-chelates to the Sn atom, which is six-coordinated in an octa­hedral environment. The three coordinating atoms along with the methyl C atom comprise a square plane, above and below which are positioned the Cl atoms. The amino group is a hydrogen-bond donor to a Cl atom of an adjacent mol­ecule, the hydrogen bond giving rise to a helical chain extending parallel to [100].
PMCID: PMC2979086  PMID: 21579051
22.  n-Butyl­dichlorido{4-cyclo­hexyl-1-[phenyl(2-pyridyl-κN)methyl­ene]­thiosemicarbazidato-κ2 N 1,S}tin(IV) chloro­form monosolvate 
The monodeprotonated Schiff base ligand in the title com­pound, [Sn(C4H9)(C19H21N4S)Cl2]·CHCl3, N,N′,S-chelates to the Sn atom, which is six-coordinated in an octa­hedral environment. The three coordinating atoms along with the butyl C atom comprise a square plane, above and below which are positioned the Cl atoms. The amino group is a hydrogen-bond donor to a Cl atom of an adjacent mol­ecule, the hydrogen bond giving rise to a helical chain propagating in [010]. The Cl and H atoms of the chloro­form mol­ecule are disordered over two positions in an 0.67:0.33 ratio.
PMCID: PMC2979137  PMID: 21579052

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