Zinc(II)-methimazole complexes: synthesis and reactivity

The tetrahedral S-coordinated complex [Zn(MeImHS)(4)](ClO4)(2), synthesised from the reaction of [Zn(ClO4)(2)] with methimazole (1-methyl-3H-imidazole-2-thione, MeImHS), reacts with triethylamine to yield the homoleptic complex [Zn(MeImS)(2)] (MeImS = anion methimazole). ESI-MS and MAS C-13-NMR experiments supported MeImS acting as a (N, S)-chelating ligand. The DFT-optimised structure of [Zn(MeImS)(2)] is also reported and the main bond lengths compared to those of related Zn-methimazole complexes. The complex [Zn(MeImS)(2)] reacts under mild conditions with methyl iodide and separates the novel complex [Zn(MeImSMe)(2)I-2] (MeImSMe = S-methylmethimazole). X-ray diffraction analysis of the complex shows a ZnI2N2 core, with the methyl thioethers uncoordinated to zinc. Conversely, the reaction of [Zn( MeImS)(2)] with hydroiodic acid led to the formation of the complex [Zn(MeImHS)(2)I-2] having a ZnI2S2 core with the neutral methimazole units S-coordinating the metal centre. The Zn-coordinated methimazole can markedly modify the coordination environment when changing from its thione to thionate form and vice versa. The study of the interaction of the drug methimazole with the complex [Zn(MeIm)(4)](2+) (MeIm = 1-methylimidazole) - as a model for Zn-enzymes containing a N-4 donor set from histidine residues shows that methimazole displaces only one of the coordinated MeIm molecules; the formation constant of the mixed complex [Zn(MeIm)(3)(MeImHS)](2+) was determined

Marked increase in PROP taste responsiveness following oral supplementation with selected salivary proteins or their related free amino acids

The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies among individuals and is associated with salivary levels of Ps-1 and II-2 peptides, belonging to the basic proline-rich protein family (bPRP). We evaluated the role of these proteins and free amino acids that selectively interact with the PROP molecule, in modulating bitter taste responsiveness. Subjects were classified by their PROP taster status based on ratings of perceived taste intensity for PROP and NaCl solutions. Quantitative and qualitative determinations of Ps-1 and II-2 proteins in unstimulated saliva were performed by HPLC-ESI-MS analysis. Subjects rated PROP bitterness after supplementation with Ps-1 and II-2, and two amino acids (L-Arg and L-Lys) whose interaction with PROP was demonstrated by (1)H-NMR spectroscopy. ANOVA showed that salivary levels of II-2 and Ps-1 proteins were higher in unstimulated saliva of PROP super-tasters and medium tasters than in non-tasters. Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter taste responsiveness, and this effect was specific to the non-taster group.(1)H-NMR results showed that the interaction between PROP and L-Arg is stronger than that involving L-Lys, and taste experiments confirmed that oral supplementation with these two amino acids increased PROP bitterness intensity, more for L-Arg than for L-Lys. These data suggest that Ps-1 protein facilitates PROP bitter taste perception and identifies a role for free L-Arg and L-Lys in PROP tasting

2,5-Bis(pyridinium-2-yl)-3,6-bis­(2-pyrid­yl)pyrazine bis­[tetra­chlorido­aurate(III)]

In the title compound, (C24H18N6)[AuCl4]2, the cation is located on an inversion center. Each of the two independent AuIII ions lies on an inversion center and has a distorted square-planar geometry. In the crystal, inter­molecular C—H⋯Cl hydrogen bonds, π–π inter­actions [centroid–centroid distances = 3.5548 (16) and 3.7507 (16) Å] and Au⋯π inter­actions [Au⋯centroid distance = 3.6424 (10) Å] are effective in the stabilization of the structure, resulting in the formation of a supra­molecular structure. Intra­molecular N—H⋯N hydrogen bonds are present in the cation

Estágios de mudança de comportamento para atividade física em adolescentes: prevalência e fatores associados

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Desportos, Programa de Pós-Graduação em Educação Física, Florianópolis, 2015.O objetivo deste estudo foi identificar a prevalência de escolares catarinenses nos Estágios de Mudança de Comportamento para atividade física, bem como descrever os seus fatores demográficos, econômicos, comportamentais e psicossociais associados. Foi realizada uma análise de dados secundária da pesquisa CompAC - 2011 (Comportamento do Adolescente Catarinense), a qual possui característica epidemiológica de base escolar com delineamento transversal. A amostra foi composta por 6.529 adolescentes de ambos os sexos, de 15 a 19 anos, de escolas estaduais de Santa Catarina. Para coleta de dados, utilizou-se questionário desenvolvido para a pesquisa em questão. Por meio de regressão logística multinominal bruta e ajusta (categoria de referência: manutenção), foram analisadas informações sobre intenção de mudança de comportamento para AF e associações com variáveis demográficas (sexo, idade, área residencial, série e turno escolar), econômicas (ocupação do adolescente, renda familiar mensal e escolaridade materna), comportamentais (prática de AF no lazer; consumo de frutas e verduras; consumo de refrigerantes; comportamento sedentário; estado nutricional; consumo de bebidas alcoólicas e tabagismo) e psicossociais (preferência de atividades no lazer, gosto por AF, percepção de estresse e de saúde). Os resultados mostraram que 43,8%, 16,2%, 17%, 16% e 7,0% dos adolescentes estavam nos estágios de manutenção, ação, preparação, contemplação e pré-contemplação, respectivamente. Com exceção do turno escolar, comportamento sedentário, tabagismo, consumo de álcool e percepção de estresse, todos os demais fatores estiveram associados a pelos menos um dos estágios. Ainda, cabe destacar que rapazes, adolescentes que trabalhavam, preferiam lazer ativo, praticavam AF no lazer, gostavam de AF e tinham percepção positiva de saúde estiveram associados ao estágio de manutenção, em relação a todos os demais estágios. Conclui-se que a maioria dos adolescentes (60,1%) praticava AF regularmente. Além disso, a cada dez adolescentes que não praticavam, oito possuíam intenção de iniciar a prática. As diferentes associações verificadas entre fatores demográficos e econômicos com cada EMC confirmaram a existência de diferentes perfis em cada EMC. Além disso, observou-se congruência entre atitudes favoráveis para a saúde e estágio de manutenção.Abstract : The aim of the study was to identify the prevalence of students from the state of Santa Catarina among the Stages of Change for physical activity, and to describe the demographic, economic, behavioral, and psychosocial factors associated. We conducted a secondary analysis of data from the CompAC research (Behavior of Adolescents from Santa Catarina State), a school-based cross-sectional epidemiological study. The study population comprised male and female adolescents aged from 15 to 19 years attending public high schools in the State of Santa Catarina in 2011. The questionnaire used was developed for the aforementioned research and was completed in the classroom. Crude and adjusted multinomial logistic regression (reference category: maintenance) was used to analyze information about intention to change physical activity behavior and associations with demographic (gender, age, grade and shift and residence location); economics (occupation, gross monthly household income and maternal education); behavioral (leisure time physical activity, fruit and vegetable intake, soft drink intake, time spent in sedentary behavior, nutritional status, alcoholic beverage intake and tobacco use); and psychosocial (preference for leisure time physical activity, liking of physical activity, and perception of stress and health) variables. The results showed that 43.8%, 16.2%, 17%, 16%, and 7% of the adolescents were in the maintenance, action, preparation, contemplation and pre-contemplation stages, respectively. With the exception of the variables school shift, sedentary behavior, tobacco use, alcohol intake, and stress perception, all of the other factors were associated with at least one of the stages. We concluded that a considerable proportion of the adolescents who are not physically active wish to begin the practice of PA. Besides that, we noticed that each stage has its peculiarities, being differently associated with the study variables, highlighting the need for interventions to promote physical activity with varying approaches according to the level of readiness to change. In face of the evidence, the present study reinforces questions regarding adolescent behavior towards intentions to be physically active in daily life

A structural spproach to the strength evaluation of linear chalcogen bonds

The experimental structural features of chalcogen bonding (ChB) interactions in over 34,000 linear fragments R–Ch⋯A (Ch = S, Se, Te; R = C, N, O, S, Se, Te; A = N, O, S, Se, Te, F, Cl, Br, I) were analyzed. The bond distances dR–Ch and the interaction distances dCh⋯A were investigated, and the functions δR–Ch and δCh⋯A were introduced to compare the structural data of R–Ch⋯A fragments involving different Ch atoms. The functions δR−Ch and δCh⋯A were calculated by normalizing the differences between the relevant bond dR–Ch and ChB interaction dCh⋯A distances with respect to the sum of the relevant covalent (rcovR + rcovCh) and the van der Waals (vdW) radii (rvdWCh + rvdWA), respectively. A systematic comparison is presented, highlighting the role of the chalcogen involved, the role of the R atoms covalently bonded to the Ch, and the role of the A species playing the role of chalcogen bond acceptor. Based on the results obtained, an innovative approach is proposed for the evaluation and categorization of the ChB strength based on structural data

A unique case of polymorphism in polyiodide networks resulting from the reaction of the drug methimazole and I2

The oxidation of thioamide methimazole (C4H6N2S) with molecular diiodine in water afforded the ionic compound [2(C4H5N2S–SN2C4H6)]I3I5 (1) in 1-triclinic and 1-monoclinic polymorphs. The polymorphic nature of [C4H5N2S–SN2C4H6]2I3I5 has been highlighted by comparing the structure of the 1-triclinic form with that of the 1-monoclinic form reported in the literature. No significant geometric differences are observed for the cations in the two polymorphs. The polymorphism is essentially due to a different arrangement in the polyiodide network of the [I5]− and [I3]− components. The FT-Raman spectrum of 1-triclinic shows the characteristic bands in the range 200–50 cm−1 which are in good agreement with the structural features of the polyiodide network. The molecular electrostatic potential maps of the cation methimazole-disulfide [C4H5N2S–SN2C4H6]+ and the bis-cation methimazole-disulfide {[C4H5N2S–SN2C4H6]+}2 in 1-triclinic have been studied to clearly identify the electrostatic potential energy distributions over the cations, and the electron belt and σ-hole areas responsible for the directionality of the non-covalent interactions in the polyiodides. It is suggested that the cation methimazole-disulfide may be a reaction intermediate in the inhibition of thyroid hormones by methimazole

2,3-Bis(thio­phen-2-yl)pyrazine­[2,3-f][1,10]phenanthroline

The mol­ecule of the title compound, C22H12N4S2, shows no crystallographic symmetry. The thiophene rings form different dihedral angles [40.15 (9) and 15.43 (10)°] with the pyrazine ring. A strong π–π stacking inter­action occurs between adjacent pyrazine­[2,3-f][1,10]phenanthroline units with an inter­planar distance of 3.4352 (16) Å

The Nature of the Chemical Bond in Linear Three-Body Systems: From I3− to Mixed Chalcogen/Halogen and Trichalcogen Moieties

The 3 centre-4 electrons (3c-4e) and the donor/acceptor or charge-transfer models for the description of the chemical bond in linear three-body systems, such as I3− and related electron-rich (22 shell electrons) systems, are comparatively discussed on the grounds of structural data from a search of the Cambridge Structural Database (CSD). Both models account for a total bond order of 1 in these systems, and while the former fits better symmetric systems, the latter describes better strongly asymmetric situations. The 3c-4e MO scheme shows that any linear system formed by three aligned closed-shell species (24 shell electrons overall) has reason to exist provided that two electrons are removed from it to afford a 22 shell electrons three-body system: all combinations of three closed-shell halides and/or chalcogenides are considered here. A survey of the literature shows that most of these three-body systems exist. With some exceptions, their structural features vary continuously from the symmetric situation showing two equal bonds to very asymmetric situations in which one bond approaches to the value corresponding to a single bond and the second one to the sum of the van der Waals radii of the involved atoms. This indicates that the potential energy surface of these three-body systems is fairly flat, and that the chemical surrounding of the chalcogen/halogen atoms can play an important role in freezing different structural situations; this is well documented for the I3− anion. The existence of correlations between the two bond distances and more importantly the linearity observed for all these systems, independently on the degree of their asymmetry, support the state of hypervalency of the central atom

Reactivity of the drug methimazole and its iodine adduct with elemental zinc

The reactivity of zinc complexes with N,S-donor molecules may be of relevance to the study of Zn-metalloproteins and -metalloenzymes. In this context, the zinc complex [Zn(MeImSH)2I2] was synthesised by the reaction of zinc powder with the 1 : 1 iodine adduct of the drug methimazole [(MeImSH)·I2]. The molecular structure of the complex, elucidated by X-ray diffraction analysis, showed a tetrahedral zinc(II) centre coordinated by two neutral methimazole units (through the sulfur atoms) and two iodides. From the reaction of MeImSH and Zn powder, the complex [Zn(MeImSH)(MeImS)2] (MeImS = deprotonated form of methimazole) was separated and characterised. An analysis of the crystal packing of the neutral complexes [Zn(MeImSH)2X2] (X = I, Br and Cl) and the ionic complex [Zn(MeImSH)3I]I showed that in all of the complexes the sulfur atom, in addition to binding to the metal centre, contributes to the formation of 1-D chains built via C(4)–HS and N–HX interactions in the neutral complexes, and via C(4)–HS and N–CH3S interactions in the ionic complex [Zn(MeImSH)3I]I. The deprotonation/protonation of the coordinated methimazole units can modulate the coordination environment at the Zn core. From the reaction of complex [Zn(MeImSH)3I]I with a strong non-coordinating organic base, we have shown that, as a consequence of the NH deprotonation of methimazole S-coordinated to zinc(II), the ligand coordination mode changes from S-monodentate to N,S-bridging. Correspondingly, in the complex [Zn(MeImSH)(MeImS)2], the MeImS that displays the N,S-bridging mode at zinc can be N-protonated and thereby changes to the S-monodentate coordination

1,2,4,5-Tetra­fluoro-3,6-diiodo­benzene–4-(pyridin-4-ylsulfan­yl)pyridine (1/1)

The asymmetric unit of the title 1:1 adduct, C10H8N2S·C6F4I2, comprises a half-mol­ecule of 1,2,4,5-tetra­fluoro-3,6-diiodo­benzene, and half a 4-(pyridin-4-ylsulfan­yl)pyridine mol­ecule. The former is completed by crystallographic inversion symmetry, the latter by twofold symmetry, with the S atom lying on the rotation axis. The almost planar 1,2,4,5-tetra­fluoro-3,6-diiodo­benzene mol­ecule (r.m.s. deviation of all 12 atoms = 0.016 Å) and twisted 4-(pyridin-4-ylsulfan­yl)pyridine mol­ecule [dihedral angle between pyridyl rings = 54.88 (13)°] are connected by N⋯I inter­actions [2.838 (4) Å], generating a supra­molecular chain with a step-ladder topology. These chains are connected in the crystal by C—H⋯F and C—H⋯π(pyrid­yl) inter­actions