Methyl Hexadecyl Viologen Inclusion in Cucurbit[8]uril: Coexistence of Three Host-Guest Complexes with Different Stoichiometry in a Highly Hydrated Crystal

The host-guest inclusion complexes of cucurbiturils with alkyl viologen have interesting architectures, chemical properties, and potential applications in sensors and nanotechnology. A highly hydrated triclinic crystal of cucurbit[8]uril (CB[8]) complexed by methyl hexadecyl viologen (MVC16) is characterized by the unprecedented coexistence in the crystal of three host-guest complexes with 3:2, 2:2, and 1:1 stoichiometries. In all these complexes, the hook-shaped alkyl chain of the MVC16 is hosted in the CB[8] macrocycles, while the methyl viologen moieties have various environments. In the Z-shaped 3:2 complex, a central CB[8] unit hosts two viologen heads in the cavity, while the 2:2 complex is held together by \u3c0-stacking interactions between two viologen units. In the square 2D tiling crystal packing of CB[8] macrocycles, the same site which favors the dimerization observed in the 2:2 complex is also statistically occupied by a single methyl viologen moiety of the 1:1 complex. The rational interpretation of the crystal structure represented an intriguing challenge, due to the complicated statistical disorder in the alkyl chains hosted in CB[8] units and in the methyl viologen moieties of 2:2 and 1:1 complexes. In contrast with the solution behavior dominated by the 2:1 complex, the coexistence of three host-guest complexes with 3:2, 2:2, and 1:1 ratios highlights the fundamental importance of packing effects in the crystallized supramolecular complexes. Therefore, the crystallization process has permitted us to capture different host-guest systems in a single crystal, revealing a supramolecular landscape in a single photo

The Role of Chain Length in Cucurbit[8]uril Complexation of Methyl Alkyl Viologens

Viologens are among the most studied guests for cucurbit[8]uril (CB[8]) and their complexation is usually driven by bipyridyl core inclusion inside the cavity to maximize both hydrophobic and cation-dipole interactions. The presence of alkyl substituents on the guest alters this complexation mode, switching to aliphatic chain inclusion in U-folded conformation. Herein, we report a thorough study of the influence of the alkyl chain length on the binding mode of methyl alkyl viologens. The chain length of the studied guests was increased by two methylene groups starting from methyl dodecyl viologen (MVC12) to the octadecyl analogue (MVC18). Complexation in water, investigated by NMR spectroscopy and ITC, revealed a clear switch from 1 : 1 to 2 : 1 host/guest stoichiometry moving from 12 to 16 carbon atoms, as a consequence of the chain folding of the major portion of the longer alkyl chain in one CB[8] cavity and the inclusion of the full viologen unit by another host molecule. The CB[8]2.MVC18 complex crystal structure evidences the unprecedented 2 : 1 stoichiometry and quantified in 12 the number of carbon atoms necessary to fill the CB[8] cavity in U-shaped conformation

Percepção de médicos e enfermeiros da Estratégia de Saúde da Família sobre terapias complementares

OBJETIVO: Analizar la percepción de profesionales de la Estrategia Salud de la Familia sobre prácticas integrales y complementarias. MÉTODOS: Se realizó estudio con 177 médicos y enfermeros a partir de un cuestionario auto-aplicado en 2008. Las variables consideradas fueron "interés por las prácticas integrales y complementarias" y "concordancia con la Política Nacional de prácticas integrales y complementarias". Sexo, edad, estudio universitario, postgrado, tiempo de formación y de trabajo, poseer hijos, oferta de prácticas integrales y complementarias en el lugar de trabajo y uso de homeopatía o acupuntura conformaron las variables independientes. Los datos fueron analizados por la prueba de chi-cuadrado y la prueba exacta de Fisher. RESULTADOS: Diecisiete centros de salud ofrecían prácticas integrales y complementarias; 12,4% de los profesionales poseían especialización en homeopatía o acupuntura; 43,5% de los médicos eran especialistas en medicina de familia y comunidad/salud de la familia. De los participantes, 88,7% desconocían las directrices nacionales para el área, a pesar de que el 81,4% concordasen con su inclusión en el Sistema Único de Salud. La mayoría (59,9%) mostró interés en capacitaciones y todos concordaran que esas prácticas deberían ser abordadas en el estudio universitario. La concordancia con la inclusión de tales prácticas se mostró asociada significativamente con el hecho de ser enfermero (p=0,027) y con el uso de homeopatía para sí mismo (p=0,019). Interés por las prácticas complementarias estuvo asociado con el uso de homeopatía para sí mismo (p=0,02) y acupuntura para familiares (p=0,013). CONCLUSIONES: Existe aceptación de las prácticas integrales y complementarias por los profesionales estudiados, asociada al contacto previo con las mismas y posiblemente relacionada a la residencia/especialización en medicina de familia y comunidad/salud de la familia.OBJETIVO: Analisar a percepção de profissionais da Estratégia de Saúde da Família sobre práticas integrativas e complementares. MÉTODOS: Estudo com 177 médicos e enfermeiros a partir de um questionário auto-aplicado em 2008. As variáveis desfecho foram "interesse pelas práticas integrativas e complementares" e "concordância com a Política Nacional de Práticas Integrativas e Complementares". Sexo, idade, graduação, pós-graduação, tempo de formado e de trabalho, possuir filhos, oferta de práticas integrativas e complementares no local de trabalho e uso de homeopatia ou acupuntura compuseram as variáveis independentes. Os dados foram analisados pelo teste do qui-quadrado e teste exato de Fisher. RESULTADOS: Dezessete centros de saúde ofereciam práticas integrativas e complementares; 12,4% dos profissionais possuíam especialização em homeopatia ou acupuntura; 43,5% dos médicos eram especialistas em medicina de família e comunidade/saúde da família. Dos participantes, 88,7% desconheciam as diretrizes nacionais para a área, embora 81,4% concordassem com sua inclusão no Sistema Único de Saúde. A maioria (59,9%) mostrou interesse em capacitações e todos concordaram que essas práticas deveriam ser abordadas na graduação. A concordância com a inclusão dessas práticas mostrou-se associada significativamente com o fato de ser enfermeiro (p = 0,027) e com o uso de homeopatia para si (p = 0,019). Interesse pelas práticas complementares esteve associado a usar homeopatia para si (p = 0,02) e acupuntura para familiares (p = 0,013). CONCLUSÕES: Existe aceitação das práticas integrativas e complementares pelos profissionais estudados, associada ao contato prévio com elas e possivelmente relacionada à residência/especialização em medicina de família e comunidade/saúde da família.OBJECTIVE: To analyze Estratégia de Saúde da Família (Family Health Strategy) professionals' perception of complementary and integrative therapies. METHODS: A study with 177 doctors and nurses was conducted in 2008, based on a self-administered questionnaire. The outcome variables were "interest in complementary and integrative therapies" and "agreement with the National Policy on Complementary and Integrative Therapies. Sex, age, graduate level of education, postgraduate level of education, length of time since graduation, length of time of work, having children, providing complementary and integrative therapies in the workplace, and using homeopathy or acupuncture comprised the independent variables. Data were analyzed using Chi-square test and Fisher's exact test. RESULTS: A total of 17 health centers provided complementary and integrative therapies; 12.4% of professionals had a specialization in homeopathy or acupuncture; 43.5% of doctors were specialists in family and community medicine/family health. Of all participants, 88.7% did not know the national directives for this area, although 81.4% agreed with their inclusion in the Sistema Único de Saúde (Unified Health System). The majority (59.9%) showed an interest in qualifications and all agreed that these therapies should be approached during the graduate course. Agreement with the inclusion of such therapies was significantly associated with the fact of being a nurse (p = 0.027) and using homeopathy for oneself (p = 0.019). Interest in complementary therapies was associated with the use of homeopathy for oneself (p = 0.02) and acupuncture by family members (p = 0.013). CONCLUSIONS: Complementary and integrative therapies are accepted by the professionals studied. This acceptance is associated with previous contact with such therapies and, probably, with residency/specialization in family and community medicine/family health

Triptycene-Roofed Quinoxaline Cavitands for the Supramolecular Detection of BTEX in Air

Two novel triptycene quinoxaline cavitands (DiTriptyQxCav and MonoTriptyQxCav) have been designed, synthesized, and applied in the supramolecular detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air. The complexation properties of the two cavitands towards aromatics in the solid state are strengthened by the presence of the triptycene moieties at the upper rim of the tetraquinoxaline walls, promoting the confinement of the aromatic hydrocarbons within the cavity. The two cavitands were used as fiber coatings for solid-phase microextraction (SPME) BTEX monitoring in air. The best performances in terms of enrichment factors, selectivity, and LOD (limit of detection) values were obtained by using the DiTriptyQxCav coating. The corresponding SPME fiber was successfully tested under real urban monitoring conditions, outperforming the commercial divinylbenzene\u2013Carboxen\u2013polydimethylsiloxane (DVB\u2013CAR\u2013PDMS) fiber in BTEX adsorption

Giant regular polyhedra from calixarene carboxylates and uranyl

Self-assembly of large multi-component systems is a common strategy for the bottom-up construction of discrete, well-defined, nanoscopic-sized cages. Icosahedral or pseudospherical viral capsids, built up from hundreds of identical proteins, constitute typical examples of the complexity attained by biological self-assembly. Chemical versions of the so-called 5 Platonic regular or 13 Archimedean semi-regular polyhedra are usually assembled combining molecular platforms with metals with commensurate coordination spheres. Here we report novel, self-assembled cages, using the conical-shaped carboxylic acid derivatives of calix[4]arene and calix[5]arene as ligands, and the uranyl cation UO22+ as a metallic counterpart, which coordinates with three carboxylates at the equatorial plane, giving rise to hexagonal bipyramidal architectures. As a result, octahedral and icosahedral anionic metallocages of nanoscopic dimensions are formed with an unusually small number of components