[Evaluation of a new device for sample collection, transport and detection of Group B Streptococcus in pregnant women]. / Evaluación de un nuevo dispositivo para la recogida de la muestra, transporte y detección del estreptococo del grupo B en mujeres embarazadas.

We have designed a new device that combines sample collection, transportation, culture and detection of Group B Streptococcus (GBS), requiring no additional processing in the clinical laboratory. The objective was to evaluate the performance of this device for GBS detection in pregnant women. The new prototype was compared to direct plating of vaginal-rectal swabs onto Granada solid media plates. Direct plating method detected 124 positive samples out of 600 (20.6%) whereas the new device detected 10 additional positive samples (134/600, 22.3%). This new device (patent-protected) could be considered for routine GBS screening.

Diagnóstico clínico de síndrome de Levy-Hollister familiar / Clinical diagnosis of familial Levy-Hollister syndrome

El síndrome lácrimo-aurículo-dento-digital (síndrome LADD o también conocido como síndrome de Levy-Hollister) es un defecto autosómico dominante con expresividad variable. Este síndrome se caracteriza por la asociación de displasias en diversos órganos y sistemas que afectan a las estructuras craneofaciales, incluyendo glándulas lagrimales y salivales, dientes, oído interno y externo y el esqueleto óseo. Presentamos este síndrome inusual y desconocido (es el primer caso en nuestro estado del que existen solamente cerca de 100 casos descritos, distribuidos en pocas familias) en referencia a un adolescente de 17 años ingresado en la Unidad de Cuidados Intensivos Pediátricos por otro motivo y que tras la exploración física se llega a un diagnóstico clínico en toda la rama familiar

Lacrimo-auriculo-dento-digital syndrome (LADD syndrome), also known as Levy-Hollister syndrome, is an autosomal dominant defect with variability on phenotypical expression. This syndrome is characterised by the association of dysplasia in various organs and systems that affect craniofacial structures, including lachrymal and salivary glands, teeth, internal and external ear, and the bone skeleton. We present this unusual and almost unknown syndrome (the first case in our state, with only about 100 cases described in the world, distributed in a few families) in a teenager of 17 years admitted to PICU for another reason. After the physical examination, a clinical diagnosis was made in the entire family branch

[Clinical diagnosis of familial Levy-Hollister syndrome]. / Diagnóstico clínico de síndrome de Levy-Hollister familiar.

Lacrimo-auriculo-dento-digital syndrome (LADD syndrome), also known as Levy-Hollister syndrome, is an autosomal dominant defect with variability on phenotypical expression. This syndrome is characterised by the association of dysplasia in various organs and systems that affect craniofacial structures, including lachrymal and salivary glands, teeth, internal and external ear, and the bone skeleton. We present this unusual and almost unknown syndrome (the first case in our state, with only about 100 cases described in the world, distributed in a few families) in a teenager of 17 years admitted to PICU for another reason. After the physical examination, a clinical diagnosis was made in the entire family branch.

Boosted CO2 reaction with methanol to yield dimethyl carbonate over Mg-Al hydrotalcite-silica lyogels.

Nonimmobilized and immobilized Mg-Al hydrotalcite-like materials on silica lyogels were prepared and activated by calcination to be tested as catalysts in the direct carboxylation reaction of methanol. The HTs supported on silica lyogels showed an important improvement and high stability in the direct synthesis reaction of DMC from CO2 and MeOH.

Síndrome de Crouzon: a propósito de 2 casos. Entidades craneoestenóticas alélicas de los genes FGFR / Presentation of two cases of Crouzon syndrome: allelic cranio-stenotic conditions of FGFR genes

Introducción: La craneosinostosis consiste en una fusión patológica precoz de una o varias suturas craneales. El 20% de los casos corresponde a formas sindrómicas con patrones hereditarios mendelianos, mientras que el 80% restante a formas no sindrómicas, pero con transmisión hereditaria en el 10-14% de los casos. A propósito de 2 pacientes con síndrome de Crouzon, se revisan los aspectos clínicos y genéticos. Pacientes y métodos: Paciente 1: niña de 35 días con macrocefalia progresiva, abombamiento de la fontanela, proptosis ocular, hipertelorismo y estrabismo divergente. Rx de cráneo con sinostosis de la sutura sagital. Fue intervenida quirúrgicamente a los 3 y 8 meses por desarrollo de pansinostosis. Paciente 2: niño de 3 años 8 meses con cefaleas de tipo migrañoso de un año de evolución. Presentaba acantosis nigricans. Rx de cráneo y TC craneal con impresiones digitales y fondo de ojo con discreto borramiento papilar. Tras 18 meses apareció edema de papila y en la TC craneal se detectó pansinostosis, requiriendo intervención quirúrgica. Resultados: Hemos presentado un paciente con síndrome de Crouzon clásico (paciente 1) y otro con acantosis nigricans (paciente 2), diagnosticándose por su particular fenotipo clínico. Conclusiones: Dada la amplia diversidad de formas alélicas en los genes FGFR que cursan con craneosinostosis, conociéndose hasta 10 entidades, realizamos una revisión de las mismas. En las formas sindrómicas, como nuestros 2 casos, conviene detallar al máximo los signos clínicos pues pueden orientar el diagnóstico, y el estudio molecular permitirá en ocasiones confirmarlo y ofrecer asesoramiento genético a las familias(AU)

Introduction: Craniosynostosis is an abnormal and premature fusion of any cranial suture. Twenty per cent of them involve any specific syndrome with Mendelian transmission; the other 80% are "non syndromic", although but 10-14% of them are genetically transmitted. Using the experience of two patients with Crouzon syndrome, a clinical and genetic review is performed. Patients and methods: Patient 1: girl of 35 days of age with progressive macrocephaly, protrusion of fontanel, ocular proptosis, hypertelorism and divergent strabismus. Cranial RX with sagittal synostosis. Surgical operation was performed with 3 months and 8 months of age due to development of pansynostosis. Patient 2: boy of 3 years 8 months of age with headaches of migrainous type of one year onset. He had acanthosis nigricans. Cranial RX and cerebral CT with evident digital markings and fundus of eye with undefined papillary limits, but 18 month later oedematous papilla were evident and pansynostosis was detected, so surgery was performed. Results: We present a patient with classical Crouzon syndrome (patient 1) and another with acanthosis nigricans (patient 2), both diagnosed by the description of characteristic clinical features. Conclusions: Ten craniosynostotic clinical forms are currently known as allelic variations of the FGFR genes, and as such have reviewed them. As in our two cases, in syndromic types is very important the accurate study of the phenotype to orientate the diagnosis, although the molecular study will confirm it in many patients and genetic counselling offered(AU)

Inter- and intraradiologist variability in the BI-RADS assessment and breast density categories for screening mammograms.

OBJECTIVE: The aim of this study was to evaluate reader variability in screening mammograms according to the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) assessment and breast density categories. METHODS: A stratified random sample of 100 mammograms was selected from a population-based breast cancer screening programme in Barcelona, Spain: 13 histopathologically confirmed breast cancers and 51 with true-negative and 36 with false-positive results. 21 expert radiologists from radiological units of breast cancer screening programmes in Catalonia, Spain, reviewed the mammography images twice within a 6-month interval. The readers described each mammography using BI-RADS assessment and breast density categories. Inter- and intraradiologist agreement was assessed using percentage of concordance and the kappa (κ) statistic. RESULTS: Fair interobserver agreement was observed for the BI-RADS assessment [κ=0.37, 95% confidence interval (CI) 0.36-0.38]. When the categories were collapsed in terms of whether additional evaluation was required (Categories III, 0, IV, V) or not (I and II), moderate agreement was found (κ=0.53, 95% CI 0.52-0.54). Intra-observer agreement for BI-RADS assessment was moderate using all categories (κ=0.53, 95% CI 0.50-0.55) and substantial on recall (κ=0.66, 95% CI 0.63-0.70). Regarding breast density, inter- and intraradiologist agreement was substantial (κ=0.73, 95% CI 0.72-0.74 and κ=0.69, 95% CI 0.68-0.70, respectively). CONCLUSION: We observed a substantial intra-observer agreement in the BI-RADS assessment but only moderate interobserver agreement. Both inter- and intra-observer agreement in mammographic interpretation of breast density was substantial. Advances in knowledge Educational efforts should be made to decrease radiologists' variability in BI-RADS assessment interpretation in population-based breast screening programmes.

[Presentation of two cases of Crouzon syndrome: allelic cranio-stenotic conditions of FGFR genes]. / Síndrome de Crouzon: a propósito de 2 casos. Entidades craneoestenóticas alélicas de los genes FGFR.

INTRODUCTION: Craniosynostosis is an abnormal and premature fusion of any cranial suture. Twenty per cent of them involve any specific syndrome with Mendelian transmission; the other 80% are "non syndromic", although but 10-14% of them are genetically transmitted. Using the experience of two patients with Crouzon syndrome, a clinical and genetic review is performed. PATIENTS AND METHODS: Patient 1: girl of 35 days of age with progressive macrocephaly, protrusion of fontanel, ocular proptosis, hypertelorism and divergent strabismus. Cranial RX with sagittal synostosis. Surgical operation was performed with 3 months and 8 months of age due to development of pansynostosis. Patient 2: boy of 3 years 8 months of age with headaches of migrainous type of one year onset. He had acanthosis nigricans. Cranial RX and cerebral CT with evident digital markings and fundus of eye with undefined papillary limits, but 18 month later oedematous papilla were evident and pansynostosis was detected, so surgery was performed. RESULTS: We present a patient with classical Crouzon syndrome (patient 1) and another with acanthosis nigricans (patient 2), both diagnosed by the description of characteristic clinical features. CONCLUSIONS: Ten craniosynostotic clinical forms are currently known as allelic variations of the FGFR genes, and as such have reviewed them. As in our two cases, in syndromic types is very important the accurate study of the phenotype to orientate the diagnosis, although the molecular study will confirm it in many patients and genetic counselling offered.

[Variability in the sensitivity to tigecycline against Acinetobacter baumannii in different culture media]. / Variabilidad en la sensibilidad de tigeciclina frente a Acinetobacter baumannii en diferentes medios de cultivo.

INTRODUCTION: The tigecycline may represent a therapeutic alternative for the control of multiresistant A. baumannii, although there is no consensus regarding the cutoff points for sensitivity or variability of MIC as a function of culture medium used for the antibiogram against this microorganism. Therefore, our objective was to verify this variability, and propose the culture medium that comes closest to the standard method. METHODS: We selected 41 strains of carbapenem-resistant A. baumannii. We analyzed the sensitivity to tigecycline in different culture media: Mueller Hinton agar Oxoid commercial (C-MH), Mueller Hinton fresh agar BD and Co., USA (F-MH) and ISO-sensitest fresh agar Oxoid, using the E-test and disk. The MICs were compared against those obtained using the technique standard of macrodilution. RESULTS: The mean MIC and inhibition diameters obtained in the different culture media corresponded to 9.26 mg/L and 15.1 mm in diameter for MH-C, 1.71 mg/L and 22.7 mm for MH-F; 2.68 mg/L and 20.8 mm for ISO-sensitest. Half the MIC obtained by the standard method of dilution was 0.47 mg/L (SD =0.21), with values between 0.25 and 1 mg/L. CONCLUSION: In the three growth media studied, MICs superior to the standard are observed, which is false to interpret resistance in many cases. However, the medium that comes closer more that of reference is the MH-F.

Evidence for quantization of mechanical rotation of magnetic nanoparticles.

We report evidence of the quantization of the rotational motion of solid particles containing thousands of atoms. A system of CoFe2O4 nanoparticles confined inside polymeric cavities has been studied. The particles have been characterized by the x-ray diffraction, transmission electron microscopy, plasma mass spectroscopy, ferromagnetic resonance (FMR), and magnetization measurements. Magnetic and FMR data confirm the presence of particles that are free to rotate inside the cavities. Equidistant, temperature-independent jumps in the dependence of the microwave absorption on the magnetic field have been detected. This observation is in accordance with the expectation that orbital motion splits the low-field absorption line into multiple lines.

Deleción intersticial del brazo largo del cromosoma 4(4q12q21.1): comunicación de un nuevo caso / Intersticial deletion of the long arm of chromosome 4(4q12-q21.1): report oa a new case

Se comunica un nuevo caso de deleción proximal del brazo largo del cromosoma 4 de novo, en un niño de 3 años de edad con rasgos fenotípicos compatibles con un síndrome de Waardemburg tipo II. Presentaba mechón de pelo blanco frontal, hipoacusia neurosensorial bilateral, desplazamiento lateral de cantos internos, heterocromía de iris, fisura velopalatina, lesiones hipocrómicas en tronco, hipotonía axial, extremidades cortas, deformidades de cuerpos vertebrales, retraso mental y ponderoestatural, reflujo gastroesofágico, síndrome de malabsorción, panhipopituitarismo, comunicación interauricular tipo ostium secundum, hipermetropía (11 dioptrías) y dificultad para la deglución. El cariotipo de alta resolución realizado en células de sangre periférica y piel hipo/hiperpigmentada puso de manifiesto una deleción intersticial en el brazo largo del cromosoma 4 (4q12-q21.1). El estudio mutacional del gen MITF (Waardenburg II) fue normal. Se revisan los casos similares descritos anteriormente en la bibliografía y se resalta que la asociación retraso mental y ponderoestatural en niños con rasgos fenotípicos que recuerdan al síndrome de Waardenburg o al piebaldismo aislado deben alertar sobre posibles deleciones en la estructura del brazo largo del cromosoma 4(AU)

We report a new case of a de novo interstitial deletion of the long arm of chromosome 4, in a three-year-old boy, with phenotypic features compatible with Waardenburg syndrome type II. Clinical examination disclosed the following abnormalities: white forelock, sensorineural hearing loss, hypertelorism, irisheterochromia, cleft palate, hypotonia, depigmented areas in trunk, short limbs and deformities in vertebral bodies, mental retardation and developmental delay. Further studies showed gastroesophageal reflux, malabsorption syndrome, panhypopituitarism, atrial septal defect, hypermetropia (11 diopters) and swallowing difficulties. Chromosome analysis of peripheral blood cells and hypopigmented and hyperpigmented skin cells showed an interstitial deletion of the long arm of chromosome 4 (4q12-q21.1). The results of the mutational study of the MITF gene (Waardenburg II) were normal. Genetic studies of the parentsal so produced normal results. We have reviewed similar cases previously published in the literature, and we stress the fact that the association of growth failure and mental retardation in children with a phenotype resembling piebald trait or Waardenburg syndrome should alert us to the possibility of deletions in the structure of the long arm of chromosome 4(AU)

Synthesis and mass spectroscopy kinetics of a novel ternary copper(II) complex with cytotoxic activity against cancer cells.

The X-ray structure of the [Cu(I-hip)(phen)2](+).(I-hip-).(H2O)7 complex (1) (where I-hipH is referred to o-iodohippuric acid and phen is 1,10-phenanthroline) and its binary synthetic intermediate [Cu(I-hip)2(H2O)3].(H2O)2 (2) have been solved and characterized by different techniques. This ternary [Cu(I-hip)(phen)2]+.(I-hip-).7H2O complex generates the copper(I) complex [Cu(phen)2]+ in aqueous solution without the addition of any external reductant, possibly by an intramolecular red-ox process in the presence of oxygen; the ESI-HRMS spectra (electrospray ionization-high resolution mass spectroscopy) detect these species and 24h after the solution, [Cu(phen)2]+ is the main product. The complex 1 is capable of cleaving DNA. To evaluate the biological properties, we carried out: cell culture, cell proliferation assays, cell cycle analysis, and electrophoresis (SDS-PAGE) and immunoblotting. Complex 1 induced apoptosis of A549 cells at low nanomolar and induced marked decreases of cancer cells at concentrations that did not change adipocyte survival. These data indicate that the parent complex is a potential anticancer drug.

Polymer-filled nanoporous silica aerogels as hosts for highly stable solid-state dye lasers.

New hybrid solid-state dye laser materials based on highly porous silica aerogels have been synthesized. The open porous network of the aerogel was saturated with laser dyes dissolved in appropriate organic monomers, and polymerization took place inside the silica structure. The resulting polymer-filled nanoporous aerogel (PFNPA) was cast in a cylindrical shape, forming monoliths that were used as gain media in solid-state dye lasers. When the PFNPA incorporated pyrromethene dyes, highly photostable laser emission with good lasing efficiency was obtained. Under the demanding conditions of tightly focused transversal pumping with 532 nm, 5 mJ pulses at 10 Hz repetition rate, the commercial dye Pyrromethene 567 exhibited laser action with only a 10% drop in the laser output after 10(6) pump pulses in the same position of the sample.

Ternary complexes metal [Co(II), Ni(II), Cu(II) and Zn(II)]--ortho-iodohippurate (I-hip)--acyclovir. X-ray characterization of isostructural [(Co, Ni or Zn)(I-hip)(2)(ACV)(H(2)O)(3)] with stacking as a recognition factor.

Four ternary metal--ortho-iodohippurate (I-hip)--acyclovir (ACV) complexes, [M(I-hip)(2)(ACV)(H(2)O)(3)] where M is Co(II) (1), Ni(II) (2), Cu (3) and Zn(II) have been obtained by reaction between the corresponding binary complexes M(II)(I-hip)(2)xnH(2)O and ACV. Three ternary complexes (M=Co, Ni and Zn) and the corresponding Zn(II)--ortho-iodohippurate binary derivative have been structurally characterized by X-ray diffraction: The studies show these three ternary complexes are isostructural and present, in solid state, an interesting stacking between the nucleobase and the aryl ring of the hippurate moiety, which probably promotes the formation of ternary complexes. Moreover, the two different ligands interact between them by means of ancillary hydrogen bonds with water molecules coordinated to the metal ion. It must be mentioned that these two recognition factors, hydrogen bonds plus stacking, could explain the reason for the isostructurality of these ternary derivatives with so different three metal ions, with diverses trends in coordination numbers and geometries. In solid state, there are two enantiomeric molecules that are related by an inversion center as the crystal-building unit (as a translational motif) for the ternary complexes.

Synthesis, characterization, and dynamic studies of 12-vertex eta5-ruthenium(II) closo-phosphine complexes with monoanionic [10-L-nido-7-R-7,8-C2B9H9]- ligands.

Ruthenacarborane complexes of formula [3-H-3,3-(PPh3)2-8-L-closo-3,1,2-RuC2B9H10)] (L = SMe2 (2a), SEt2 (2b), S(CH2)4 (2c), SEtPh (2d)) and [1-Me-3-H-3,3-(PPh3)2-8-L-closo-3,1,2-RuC2B9H9)] (L = SMe2 (2e), SEt2 (2f)) were prepared by reaction of the respective monoanionic charge-compensated ligands [10-L-nido-7,8-C2B9H10]- and [7-Me-10-L-nido-7,8-C2B9H9]- with [RuCl2(PPh3)3]. Similary, complexes [3-H-3,3,8-(PPh3)3-closo-3,1,2-RuC2B9H10)] (4a) and [3-H-3,3-(PPh3)2-8-PPh2Me-closo-3,1,2-RuC2B9H10)] (4b) were prepared from the corresponding phosphonium ligands. The reaction is done in one pot by reacting the ligand with the Ru(II) complex in a 1.5:1 ratio. All compounds have been fully characterized by multinuclear NMR spectroscopy, and the molecular structures for 2a and 4a have been elucidated by single-crystal X-ray diffraction analysis. The Ru(II) atom in this complex is on the open face of the monoanionic charge-compensated ligand adopting a pseudooctahedral coordination. Formally, three positions are supplied by the C2B3 open face, two PPh3 groups occupy two other positions, and a hydride fulfills the remaining one. The hydride complexes were generated with no special reagent. They result from a dehalogenation in the presence of ethanol.

Uracilato and 5-halouracilato complexes of Cu(II), Zn(II) and Ni(II). X-ray structures of [Cu(uracilato-N(1))(2)(NH(3))(2)].2(H(2)O), [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2), [Ni(5-chlorouracilato-N(1))(2)(en)(2)].2H(2)O and [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O).

Four new complexes of uracilato and 5-halouracilato with the divalent metal ions Cu(II), Zn(II) and Ni(II) were obtained and structurally characterized. [Cu(uracilato- N(1))(2)(NH(3))(2)].2(H(2)O) (1) and [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2) (2) complexes present distorted square planar co-ordination geometry around the metal ion. Although an additional axial water molecule is present [Cu(II)-OH(2)=2.89 A (for 1) and 2.52 A (for 2)] in both cases, only in the complex 2 would be considered in the limit of a bond distance. The Zn(II) in [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O) presents a tetrahedral co-ordination with three ammonia molecules and the N(1) of the corresponding uracilato moiety. A non-coordinated uracilato molecule is present as a counterion and a recognition between co-ordinated and free ligands, by means a tandem of H-bonds, should be mentioned. Finally, the complex [Ni(5-chlorouracilato-N(1))(2)(en)(2)] (H(2)O)(2) (where en is ethylenediamine) presents a typical octahedral trans co-ordination with additional hydrogen bonds between 5-chlorouracilato and the NH(2) groups of ethylenediamine units.

[Septo-optic dysplasia]. / Displasia septóptica.

INTRODUCTION: Septo optic syndrome, described by De Morsier in 1956, consists in the hypoplasia of one or both optic nerves, mid line brain malformations and hypothalamohypophysial dysfunction, which is inconstant. It is an infrequent, but treatable, cause of hepatic and neurological damage, and it is important to obtain an early diagnosis and to begin hormone replacement therapy. CASE REPORT: We report the clinical case of a female baby who was diagnosed early on as suffering from septo?optic dysplasia, after discovery of the existence of cholestatic jaundice. In our case the three components of the syndrome were present: hypothalamohypophysial dysfunction, bilateral hypoplasia of the optic nerves and brain malformations with dysplasia of the transparent septum. All this gives rise to complex clinical features and the predominance of hypernatraemic dehydration secondary to insipid diabetes, nystagmus and serious psychomotor retardation. Our patient died, as in other cases reported in the literature, from an episode of sudden death. DISCUSSION: Despite the importance of an early diagnosis of this disorder, it is usually late. Most children who present hypopituitarism traits in the neonatal period are not diagnosed at that time, with the subsequent risk of death or brain damage. Some clinical findings, which appear early on and can provide clues which aid us to reach a diagnosis, are the appearance of episodes of hypoglycaemia in the neonatal period, the existence of micropenis and cryptorchidism with hypoplasic testes, jaundice or the appearance of clinical manifestations of insipid diabetes. Later on nystagmus and neurological symptoms may appear. The final diagnosis is performed through the use of neuroimaging techniques (CT or MRI) and hormonal studies.

Displasia septóptica / Septo-optic dysplasia

Introducción. El síndrome septóptico, descrito por De Morsier en 1956, consiste en la hipoplasia de uno o ambos nervios ópticos, malformaciones cerebrales de línea media y disfunción hipotalamohipofisaria, la cual es inconstante. Es una causa poco frecuente, pero tratable, de daño hepático y neurológico, y es de gran importancia su diagnóstico precoz e instauración de tratamiento hormonal substitutivo. Caso clínico. Presentamos el caso clínico de una lactante que se diagnosticó precozmente de displasia septoóptica, a partir de la existencia de ictericia colestática. En nuestro caso se presentan los tres componentes del síndrome: disfunción hipotalamohipofisaria, hipoplasia bilateral de nervios ópticos y malformaciones cerebrales con displasia del septum pellucidum. Todo ello da lugar a una florida clínica, y predomina la deshidratación hipernatrémica secundaria a diabetes insípida, nistagmo y grave retraso psicomotor. Nuestra paciente falleció, como otros casos descritos en la bibliografía, por un episodio de muerte súbita. Discusión. Pese a la importancia del diagnóstico precoz de esta entidad, éste suele ser tardío. La mayoría de niños que presentan rasgos de hipopituitarismo en el período neonatal no se diagnostican en ese momento, con el consecuente riesgo de muerte o daño cerebral. Algunos hallazgos clínicos, que aparecen tempranamente y que pueden darnos la pista para llegar al diagnóstico, son la aparición de episodios de hipoglucemia en el período neonatal, la existencia de micropene y criptorquidia con testes hipoplásicos, ictericia o aparición de manifestaciones clínicas de diabetes insípida. Más adelante, pueden aparecer nistagmo y síntomas neurológicos. El diagnóstico definitivo se realiza mediante técnicas de neuroimagen (TAC o RM) y estudios hormonales (AU)

Effect of asymmetry on the electronic delocalization in diiron and iron-cobalt mixed valence metallocenic compounds.

In this work, we report the synthesis and a study on the degree of electronic delocalization in the asymmetric mixed valence complexes [CpFe(C(8)H(6))Fe(C(8)H(7))](+), 3a(+), and [CpCo(C(8)H(6))Fe(C(8)H(7))](+), 3b(+), (Cp = C(5)Me(5), C(8)H(6) = pentalenyde, C(8)H(7) = hydropentalenyde, and = ((3,5(CF(3))(2)C(6)H(3))(4)B(-))). Electrochemical methods, (57)Fe Mössbauer spectroscopy, electronic spectroscopy, and electron paramagnetic resonance were used for this purpose. Although the anti conformation of the complexes precludes any metal-metal interaction, all the techniques employed show that 3a(+) is a electronic delocalized system, while 3b(+) behaves as two individual metallic centers with localized electron density.