Bithiophene azo dyes bearing thiazole, benzothiazole and thiadiazole heterocycles: synthesis and comparative study of their photochromic properties

Although a large variety of diarylazo compounds are used in the design of optical materials, only a few reports concerning the photoisomerization of heterocyclic azo dyes can be found in the literature. In the last years our group reported for the first time the synthesis and characterization of heterocyclic azo dyes bearing thiophene and pyrrole moieties as thermally stable conducting materials, solvatochromic probes and nonlinear optical systems. The E/Z isomerizable N=N double bond within a conducting chain can work as molecular switch, making these (hetero)aryl azo systems promising candidates as photochromic materials [1-6]. As part of our continuing interest in heterocyclic azo dyes for optical applications we report here the synthesis of dithiazole azo dyes 4 using as coupling components bithiophene and thiadiazolyldiazonium salts and the comparative study of the photochromic properties of 4 classes of bithiophene azo dyes 1-4. This study reveals that the kinetics of the E-Z transformation of these systems is strongly influenced by the electronic nature of the heterocyclic diazene moiety as well as its position on the bithiophene system. Moreover, for benzothiazole 3 and thiadiazole 4 azo dyes the switching between the two photoisomers can be performed in 3 seconds with a significant conversion of the trans-isomer to the thermal unstable cis-isomer (19-21%) showing that they could be used as efficient photochromic materials. Thanks are due to the Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through the Centro de Química - Universidade do Minho, Projects PTDC/QUI/66251/2006 (FCOMP-01-0124-FEDER-007429), PEst-C/QUI/UI0686/2011 (F-COMP-01-0124-FEDER-022716) and a PhD grant to M. C. R. Castro (SFRH/BD/78037/2011). [1] Coelho, P. J.; Castro, M. C. R.; Fonseca, A. M. C.; Raposo, M.M.M. Dyes Pigments 2012, 92, 745. [2] Raposo, M. M. M.; Castro, M. C. R.; Schellenberg, P.; Fonseca, A. M. C.; Belsley, M. Tetrahedron 2011, 67, 5189. [3] Raposo, M. M. M.; Fonseca, A. M. C.; Castro, M. C. R.; Belsley, M.; Cardoso, M. F. S.; Carvalho, L. M.; Coelho, P. J. Dyes Pigments 2011, 91, 62. [4] Raposo, M. M. M.; Castro, M. C. R.; Belsley, M.; Fonseca, A. M. C. Dyes Pigments 2011, 91, 454. [5] Coelho, P. J.; Carvalho, L. M.; Moura, J. C. V. P.; Raposo, M. M. M. Dyes Pigments 2009, 82, 130. [6] Coelho, P. J.; Carvalho, L. M.; Fonseca, A. M. C.; Raposo, M. M. M. Tetrahedron Lett 2006, 47, 3711

Enhancement of the photochromic switching speed of bithiophene azo dyes

A series of heteroaryl substituted bithiophene azo dyes in solution were irradiated with visible light to promote the azo E–Z isomerization and then the kinetics of the thermal Z–E back reaction was studied. The speed of this process is strongly influenced by the nature of the aromatic ring linked to the N=N function.While thiazole bithiophene azo dyes exhibit high switching speeds between the two isomers, but limited interconversion, for benzothiazole and substituted thiadiazole bithiophene azo dyes the switching between the two photoisomers can be performed in 3 s with a significant conversion of the transisomer to the thermal unstable cis-isomer (19–21%) and therefore a notable variation of the visible spectrum is observed.Fundação para a Ciência e a Tecnologia (FCT

The influence of 1α.25-dihydroxyvitamin D3 coating on implant osseointegration in the rabbit tibia

Objectives: This study aims to evaluate bone response to an implant surface modified by 1α,25-dihydroxyvitamin D3 [1.25-(OH)2D3] in vivo and the potential link between 1.25-(OH) 2D3 surface concentration and bone response. Material and Methods: Twenty-eight implants were divided into 4 groups (1 uncoated control, 3 groups coated with 1.25-(OH)2D3 in concentrations of 10-8, 10-7 and 10-6 M respectively), placed in the rabbit tibia for 6 weeks. Topographical analyses were carried out on coated and uncoated discs using interferometer and atomic-force-microscope (AFM). Twenty-eight implants were histologically observed (bone-to-implant-contact [BIC] and new-bone-area [NBA]). Results: The results showed that the 1.25-(OH)2D3 coated implants presented a tendency to osseointegrate better than the non-coated surfaces, the differences were not significant (P > 0.05). Conclusions: The effect of 1.25-(OH)2D3 coating to implants suggested possible dose dependent effects, however no statistical differences could be found. It is thought that the base substrate topography (turned) could not sustain sufficient amount of 1.25-(OH)2D3 enough to present significant biologic responses. Thus, development a base substrate that can sustain 1.25-(OH)2D3 for a long period is necessary in future studies

Synthesis and characterization of novel diazenes bearing pyrrole, thiophene and thiazole heterocycles as efficient photochromic and nonlinear optical (NLO) materials

Two series of novel thermally stable second-order nonlinear optical (NLO) and photochromic chromophores have been designed and synthesized. The two series of compounds were based on different combinations of donor groups (pyrrole or thienylpyrrole) which act simultaneously as Π-conjugated bridges, together with diazoaryl or diazothiazolyl as acceptor moieties. Their photochromic and electrochemical behavior were characterized, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The results of these studies have been critically analyzed together with two other related compounds reported earlier from our laboratories in which the thienylpyrrole system was used as the donor group keeping the functionalized diazoaryl as acceptor moiety. The measured molecular first hyperpolarizabilities and the observed photochromic behavior showed strong variations for the different donor systems used (pyrrole or thienylpyrrole) and were also sensitive to the acceptor strength of the diazenehetero(aryl) moiety. The thienylpyrrole based compounds endowed with extended Π-conjugated bridges and stronger donor auxiliary effects in comparison to the pyrrole compounds, when coupled to the stronger acceptor diazo(hetero)aryl groups gave rise to significantly larger hyperpolarizabilities (β= 274 - 415 x 10-30 esu) for an incident wavelength of 1064nm). These compounds also displayed improved photochromic behavior with very fast response to the visible light stimulus (1.5 s) and fast thermal return to the original forms (2-3 s).Thanks are due to the Fundacao para a Ciencia e Tecnologia (Portugal) and FEDER for financial support through the Centro de Quimica and Centro de Fisica- Universidade do Minho, Project PTDC/QUI/66251/2006 (FCOMP-01-0124-FEDER-007429), Project PTDC/CTM/105597/2008 with funding from COMPETE/FEDER and research grants to M. C. R. Castro (UMINHO/BI/142/2009) and M. F. S. Cardoso (UMINHO/BII/249/2009). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT

(R)-2-Phen­oxy-1-(4-phenyl-2-sulfan­ylidene-1,3-oxazolidin-3-yl)ethanone

The central 1,3-oxazolidine-2-thione ring in the title compound, C17H15NO3S, is approximately planar with maximum deviations of 0.036 (4) and −0.041 (5) Å for the O and methyl­ene-C atoms, respectively. The dihedral angles formed between this plane and the two benzene rings, which lie to the same side of the central plane, are 86.5 (2) [ring-bound benzene] and 50.6 (3)°. The ethan-1-one residue is also twisted out of the central plane, forming a O—C—N—C torsion angle of 151.5 (5)°. The dihedral angle formed by the benzene rings is 62.8 (2)° so that overall, the mol­ecule has a twisted U-shape. In the crystal, mol­ecules are linked into supra­molecular arrays two mol­ecules thick in the bc plane through C—H⋯O, C—H⋯S and C—H⋯π inter­actions

Apolipoprotein E polymorphism influences orthotopic liver transplantation outcomes in patients with hepatitis C virus-induced liver cirrhosis

BACKGROUND: Hepatitis C virus (HCV) infection is responsible for a chronic liver inflammation, which may cause end-stage liver disease and hepatocellular carcinoma. Apolipoprotein E (protein: ApoE, gene: APOE), a key player in cholesterol metabolism, is mainly synthesized in the liver and APOE polymorphisms may influence HCV-induced liver damage. AIM: To determine whether APOE alleles affect outcomes in HCV-infected patients with liver cirrhosis following orthotopic liver transplantation (OLT). METHODS: This was a cohort study in which 179 patients, both genders and aged 34-70 years, were included before or after (up to 10 years follow-up) OLT. Liver injury severity was assessed using different criteria, including METAVIR and models for end-stage liver disease. APOE polymorphisms were analyzed by quantitative real-time polymerase chain reaction. RESULTS: The APOE3 allele was the most common (67.3%). In inflammation severity of biopsies from 89 OLT explants and 2 patients in pre-transplant, the degree of severe inflammation (A3F4, 0.0%) was significantly less frequent than in patients with minimal and moderate degree of inflammation (≤ A2F4, 16.2%) P = 0.048, in patients carrying the APOE4 allele when compared to non-APOE4. In addition, a significant difference was also found (≤ A2F4, 64.4% vs A3F4, 0.0%; P = 0.043) and (A1F4, 57.4% vs A3F4, 0.0%; P = 0.024) in APOE4 patients when compared to APOE3 carriers. The fibrosis degree of the liver graft in 8 of 91 patients and the lack of the E4 allele was associated with more moderate fibrosis (F2) (P = 0.006). CONCLUSION: Our results suggest that the E4 allele protects against progression of liver fibrosis and degree of inflammation in HCV-infected patients

A new cryptic species of Echinostoma (Trematoda: Echinostomatidae) closely related to Echinostoma paraensei found in Brazil

Echinostoma paraensei, described in Brazil at the end of the 1960s and used as a biological model for a range of studies, belongs to the ‘revolutum’ complex of Echinostoma comprising species with 37 collar spines. However, molecular data are available only for a few isolates maintained under laboratory conditions, with molecular prospecting based on specimens originating from naturally infected hosts virtually lacking. The present study describes Echinostoma maldonadoi Valadão, Alves & Pinto n. sp., a species cryptically related to E. paraensei found in Brazil. Larval stages (cercariae, metacercariae and rediae) of the new species were found in the physid snail Stenophysa marmorata in the State of Minas Gerais, Brazil, the same geographical area where E. paraensei was originally described. Adult parasites obtained experimentally in Meriones unguiculatus were used for morphological (optical microscopy) and molecular [28S, internal transcribed spacer (ITS), nad1 and cox1] characterization. The morphology of larval and adult parasites (most notable the small-sized dorsal spines in the head collar), associated with low (0–0.1%) molecular divergence for 28S gene or ITS region, and only moderate divergence for the mitochondrial cox1 gene (3.83%), might suggest that the newly collected specimens should be assigned to E. paraensei. However, higher genetic divergence (6.16–6.39%) was found in the mitochondrial nad1, revealing that it is a genetically distinct, cryptic lineage. In the most informative phylogenetic reconstruction, based on nad1, E. maldonadoi n. sp. exhibited a strongly supported sister relationship with E. paraensei, which may indicate a very recent speciation event giving rise to these 2 species