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Abstract Objectives: to evaluate static and dynamic respiratory muscle strength in children and adolescents with asthma. Methods: cross-sectional study, involving 80 children and adolescents, 40 with asthma and 40 healthy controls. Biological and clinical characteristics were analyzed. The analysis of the dynamic inspiratory muscle strength was obtained using the KH5 device of the POWERbreathe® line, while the static evaluation was performed using an analog manova-cuometer. Results: the mean obtained from the S-Index was higher in the control group compared to asthmatics (p = 0.026). There was no statistical difference between MIP values for asthmatics and predicted values (p = 0.056). The MEP results showed a significant difference between the mean of the cases and the predicted values (p = 0.000). There was a positive correlation between height and S-Index (p = 0.002 and r = 0.438). Conclusion: the present study demonstrated that the static inspiratory muscle strength (PImáx) of children and adolescents with asthma in comparison with the values predicted in the literature does not differ, however, when submitted to dynamic assessment (S-Index), it presents higher values in healthy controls. In addition, the S-Index showed a positive correlation with the child's height.

Introdução: Cirurgia bariátrica é um importante tratamento para a obesidade severa. Como ansiedade e estratégias de enfrentamento insatisfatórias estão associadas à obesidade, é importante avaliar o comportamento de pacientes candidatos e submetidos à cirurgia bariátrica, uma vez que esta pode ter impacto negativo sobre os resultados desse procedimento. Objetivo: avaliar ansiedade, depressão, estratégias de enfrentamento e qualidade de vida pré e pós-cirurgia bariátrica a partir dos dados da avaliação psicológica. Método: Estudo descritivo, longitudinal, com 118 pacientes atendidos no Ambulatório de Cirurgia Bariátrica de um hospital de ensino de alta complexidade, que realizaram o procedimento entre janeiro/2011 e janeiro/2015. Foram utilizados dados primários (avaliação psicológica pós-cirurgia) e secundários (relatório da avaliação psicológica pré-cirurgia). A avaliação psicológica incluiu: questionário socioeconômico, Escala Hospitalar de Ansiedade e de Depressão (HAD), Questionário de Qualidade de Vida SF-36 e Escala de Modos de Enfrentamento de Problemas (EMEP). Resultados: A média de idade dos pacientes foi 40,1 anos e houve predomínio de mulheres (n = 105, 89%). Houve redução significante dos sintomas de depressão após a cirurgia (p

Abstract: An empirical model of leaching of pesticides was developed to simulate the concentration of fungicides throughout unsaturated soil. The model was based on chemical reactions and the travel time of a conservative tracer to represent the travel time required for water to flow between soil layers. The model's performance was then tested using experimental data from dimethomorph and pyrimethanil applied to the soil under field and laboratory conditions. The empirical model simulated fungicide concentration on soil solids and in soil solution at different depths over time (mean square error between 2.9 mg 2  kg -2 and 61mg 2  kg -2 ) using sorption percentages and degradation rates under laboratory conditions. The sorption process was affected by the organic carbon, clay, and the effective cation exchange capacity of the soil. The degradation rate values of dimethomorph (0.039 d -1 -0.009 d -1 ) and pyrimethanil (0.053 d -1 -0.004 d -1 ) decreased from 0 to 40 cm and then remained constant in deeper soil layers (60-80 cm). Fungicide degradation was a critical input in the model at subsurface layers. The model was determined to be a reliable mathematical tool to estimate the leachability of pesticides in tropical soil under a steady-state flow. It may be extended to other substances and soils for environmental risk assessment projects., Supplementary Information: The online version contains supplementary material available at 10.1007/s13762-023-05038-w., Competing Interests: Conflict of interestNone of the authors has any potential conflict of interest., (© The Author(s) 2023.)

Most guidelines fail to specify patient positioning during central venous catheterization. The objective was to determine the effects of head-down tilt (Trendelenburg position) and head rotation on the internal jugular vein (IJV). A prospective, observational, longitudinal, and descriptive study using healthy adult volunteers, of both sexes, was performed. The change in position and cross-sectional areas (CSA) of the right IJV and common carotid artery (CA) were measured by ultrasonography during Trendelenburg position (TP) (0°, 5°, 10°, and 15°) and contralateral head-rotation (HR) (0°, 45°, and 90°) for a total of 12 positions. The neutral supine position was first, randomizing the other 11 positions, with 5-min rest intervals in between. Vital signs and symptoms were recorded. A total of 54 volunteers were recruited between the ages of 21 and 32, of which 30 were men. Any degree of TP or HR significantly increased the CSA. The largest area obtained was 1.78 cm 2 with a TP15HR90 which did not have a statistical difference with TP10HR45 1.59 cm 2 . A HR90 tended to displace the IJV medially, overlaying the CA. Any degree of TP or HR will significantly increase CSA or the right IJV. A 5° to 10° TP is recommended when the patient's condition allows it, with a 45° HR, without significantly displacing the IJV anterior to the CCA., (© 2022 American Association for Clinical Anatomists and the British Association for Clinical Anatomists.)

Introduction: High-grade serous primary peritoneal cancer is highly sensitive to platinum-based chemotherapy with response rates above 80%. Incidence of immediate hypersensitivity reactions to carboplatin is estimated to be between 15% and 20%, usually seen after a mean of 6-8 infusions, with patients developing moderate to severe reactions., Case Report: A 62-year-old female patient with stage IIIC primary high-grade serous carcinoma of the peritoneum was diagnosed and chemotherapy with carboplatin and Paclitaxel was indicated by the oncology service and patient shows response. At 6 months the patient returns, a new PET/CT reports progression of the disease. Carboplatin/paclitaxel cycles are restarted and in the eight cycle of carboplatin within 40 min of administration, she presented severe anaphylaxis with skin, pulmonary, cardiac and atypical symptoms. Infusion is suspended and intramuscular epinephrine with hydrocortisone and chlorphenamine are administered resolving symptoms., Management and Outcome: Intradermal skin test with carboplatin at the concentration of 10 mg / ml (dilution 1: 100) was positive. Due to the symptoms presented and to continue the safe reintroduction to carboplatin, a 4 bag 16-step drug desensitization protocol was carried out at a total dose of 620 mg with no hypersensitivity reactions., Discussion: Prolonged carboplatin use is associated with an increased incidence of carboplatin-related hypersensitivity reactions. And in patients that present hypersensitivity reactions, a safe and effective carboplatin desensitization protocol can be carried out to reach the administration of a full dose. Desensitization protocol induces tolerance to a drug temporarily and is dependent on continuous exposure.

Latin America (LATAM) children offer special insight into Severe Acute Respiratory Syndrome Coronavirus 2 (SARS COV2) due to high-risk race/ethnicity, variability in medical resources, diverse socioeconomic background, and numerous involved organ systems. This multinational study of LATAM youth examined the distinguishing features of acute or late multisystem SARS COV2 with versus without cardiac involvement. A consecutive sample of youth 0-18 years old (N = 98;50% male) presenting with multisystem SARS COV2 to 32 centers in 10 Latin American countries participating in a pediatric cardiac multi-imaging society were grouped as with versus without cardiac involvement, defined as abnormal echocardiographic findings or arrhythmia. Collected clinical data were analyzed by Student's t-test or Fisher's exact test. Cardiac (N = 48, 50% male) versus no cardiac (N = 50, 50% male) were similar in age; weight; nonrespiratory symptoms; and medical history. The cardiac group had 1 death and symptoms including coronary artery dilation, ejection fraction <50%, pericardial effusion, peripheral edema, arrhythmia, and pulmonary artery thrombus. The cardiac group had higher risk of ICU admission (77% vs 54%, p = 0.02); invasive ventilation (23% vs 4%,p = 0.007); vasoactive infusions (27% vs 4%, p = 0.002); prominent respiratory symptoms (60% vs 36%, p < 0.03); abnormal chest imaging (69% vs 34%, p = 0.001); troponin (33% vs 12%, p = 0.01); alanine aminotransferase (33% vs 12%, p = 0.02); and thrombocytopenia (46% vs 22%, p = 0.02). Receiver operating curve analysis showed that abnormal laboratories had 94% sensitivity and 98% negative predictive value on the need for ICU interventions.Conclusion: In LATAM children with multisystem SARS COV2, cardiac involvement was prevalent. Cardiac involvement was more likely to require ICU interventions, certain abnormal labs, and respiratory involvement. What is Known: • SARS COV2 can be asymptomatic in children but in some cases can have serious multisystemic involvement. • Hispanic ethnicity is purportedly at high risk of SARS COV2 in nations where they are often disadvantaged minority populations. What is New: • Latin American children presenting with multisystem SARS COV2 frequently have cardiac involvement which was associated with ICU interventions; prominent respiratory symptoms; abnormal chest X-ray; elevated troponin, ALT, and thrombocytopenia. • Elevated troponin, ALT or thrombocytopenia had high sensitivity and negative predictive value on the need for intensive care interventions., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Stepwise reaction of W(CO)6 with tetramethylated bicyclic guanidinate ligands, characterized by a central C(N)3 unit joining two fused six-membered rings with CH2CMe2CH2 units spanning two of the nitrogen atoms, allowed isolation of W2(μ-CO)2(μ-TMhpp)2(η(2)-TMhpp)2, 1, a precursor of W2(TMhpp)4Cl2 ( J. Am. Chem. Soc. 2013 , 135 , 17889 ; TMhpp = [(CH2CMe2CH2)2(C(N)3)]). Subsequent heating of 1 followed by reaction with TlPF6 generates [W2(TMhpp)4](PF6)2, 2. Compound 1 has an edge-sharing bioctahedral (ESBO) arrangement with a W2(μ-CO)2(4+) core having semibridging carbonyl groups, while 2 has a paddlewheel structure with a W2(6+) core spanned by four tetramethyl-substituted bicyclic guanidinate ligands. This compound also has hexafluorophosphate anions along the metal-metal bond that are nestled within methylene groups with the aid of a network of weak C-H···F interactions that prevent a close approach of the fluorine atoms to the dimetal unit. Theoretical computations were carried out on ditungsten model complexes supported by three ligand sets: bicyclic guanidinate, guanidinate, and formamidinate. The computations show that the π-accepting ability of the carbonyl groups significantly lowers the energy of the σ* orbital, and thus, the energy falls below that of the δ orbital. This information along with the diamagnetism of both 1 and 2-as shown by the sharp signals in the (1)H NMR spectra that support a lack of unpaired electrons (S = 0)-is consistent with the electronic configuration of σ(2)π(2)σ*(2)δ(2) (π(2)δ(2)) and thus a formal bond order of 2 for 1 and σ(2)π(4) for the triple-bonded W2(6+) core in 2. A comparison of the W-W bond lengths in 2, its chloro precursor W2(TMhpp)4Cl2, and the corresponding analogue W2(hpp)4Cl2 shows a substantial effect from the axially coordinated ligand, distal lone pair in determining the length of the metal-metal bond for these paddlewheel species. The importance of the ligands in tuning the energy level of the metal-metal bonds that may lead to dramatic changes in physical properties is also discussed. It is noteworthy that bicyclic guanidinates with the strongest π-donating ability push upward the energy level of the δ orbital, thus allowing the compounds to be easily oxidized.

The development of our understanding of the δ bond and its role in quadruple metal-metal bonding is described in terms of the conceptual advances and experimental and theoretical results achieved through a 50-year period beginning with the seminal report by Cotton and co-workers in 1964. The work behind the original discovery is described, along with the qualitative orbital description of the components of the quadruple bond. The effect of torsion about the metal-metal axis on the metal-metal bond length is described, together with the conclusion that this accords with a progressive loss of the δ component of the metal-metal bond. The important role of photoelectron spectroscopy in characterizing the loss of electrons from the metal-metal bonding orbitals is reviewed, as are the electron paramagnetic resonance results that establish that unpaired electrons, when present, populate metal-based orbitals. Other important results are described: destabilization of the metal-metal bond to produce strong reducing agents, exceptions to the expected orbital ordering, and the use of chiroptical properties to reveal additional information about the electronic structure of the metal-metal bond.

Variable-temperature magnetic and structural data of two pairs of diruthenium isomers, one pair having an axial ligand and the formula Ru2(DArF)4Cl (where DArF is the anion of a diarylformamidine isomer and Ar = p-anisyl or m-anisyl) and the other one being essentially identical but devoid of axial ligands and having the formula [Ru2(DArF)4]BF4, show that the axial ligand has a significant effect on the electronic structure of the diruthenium unit. Variable temperature crystallographic and magnetic data as well as density functional theory calculations unequivocally demonstrate the occurrence of π interactions between the p orbitals of the chlorine ligand and the π* orbitals in the Ru2(5+) units. The magnetic and structural data are consistent with the existence of combined ligand σ/metal σ and ligand pπ/metal-dπ interactions. Electron paramagnetic resonance data show unambiguously that the unpaired electrons are in metal-based molecular orbitals.

This Perspective reviews some of the contributions that EPR spectroscopy has made for the understanding of the bonding and electronic structure of molecular species with metal-to-metal multiple bonds. The goal is to show how useful this technique can be in (a) elucidating whether unpaired electrons reside in metal-based or ligand-based molecular orbitals, (b) providing information on the metal center's total electronic spin, an aspect that offers support to its oxidation state, (c) informing about the distribution of the unpaired electrons between the metals and the organic ligand, (d) detecting molecular dynamics and phase transitions to complement X-ray studies and (e) using high-frequency, high-field EPR for studying compounds that might be EPR-silent when only commonly available spectrometers are used. A brief comparison with NMR is provided in the ESI where it is noted that for typical laboratory magnetic fields, the energy gap between resonant states in EPR is in the microwave region of the electromagnetic spectrum (GHz) while for NMR it is in the radiofrequency range (MHz). Our aim is to encourage the inorganic chemistry community and more broadly other chemists and physicists to collaborate while characterizing new paramagnetic inorganic complexes. Enough basic background is provided as ESI to allow senior-level undergraduate and graduate students to understand the simplicity as well as the power of EPR spectroscopy with a view to encourage them to use this technique in their own research activities. Finally, it should be noted that this report commemorates the fiftieth anniversary of the description in Science of the first species with a quadruple bond.

An ionic edge-sharing bioctahedral (ESBO) species has been prepared having a tetramethylated bicyclic guanidinate with two fused six-membered rings characterized by a fairly flat N-C(N)-N skeleton and abbreviated as TMhpp. The anion has two W(IV) atoms bridged by two oxo groups; the metal atoms are also spanned by two bridging guanidinate ligands, and each has two monodentate chlorine atoms. The complex formulated as (H2TMhpp)2[W(μ-O)(μ-TMhpp)Cl2]2 has the shortest W-W distance (2.3318(8) Å) of any species with a σ(2)π(2) electronic configuration. The anion and cations are connected by hydrogen bonds. To unambiguously ascertain the existence of the double-bonded W2(μ-O)2 entity, density functional theory calculations and natural bond orbital analyses were done on an analogous but hypothetical species with a W2(μ-OH)2 core having trivalent tungsten atoms and a possible σ(2)π(2)δ(2) electronic configuration. The calculations decidedly support the presence of tungsten-oxo instead of tungsten-hydroxo groups and thus the existence of the double-bonded W2(μ-O)2 core. The strong bonding interaction between metal atoms is a clear indication that under certain circumstances the two octahedra in ESBO species do not behave as the sum of two mononuclear compounds.

Two very soluble compounds having W2(bicyclic guanidinate)4 paddlewheel structures show record low ionization energies (onsets at 3.4 to 3.5 eV) and very negative oxidation potentials in THF (-1.84 to -1.90 V vs Ag/AgCl). DFT computations show the correlation from the gas-phase ionization energies to the solution redox potentials and chemical behavior. These compounds are thermally stable and easy to synthesize in high yields and good purity. They are very reactive and potentially useful stoichiometric reducing agents in nonpolar, nonprotonated solvents.

Three rare compounds have been synthesized and structurally characterized; these species have paddlewheel structures and Re(2)(7+) cores surrounded by four bicyclic guanidinates and two axial ligands along the Re-Re axis. Each possesses a formal bond order of 3.5 and a σ(2)π(4)δ(1) electronic configuration that entails the presence of one unpaired electron for each compound. The guanidinate ligands characterized by having CH(2) entities and a central C(N)(3) unit that joins two cyclic units--one having two fused 6-membered rings (hpp) and the other having a 5- and a 6-membered ring fused together (tbn)--allowed the isolation of [Re(2)(tbn)(4)Cl(2)]PF(6), 1, [Re(2)(tbn)(4)Cl(2)]Cl, 2, and [Re(2)(hpp)(4)(O(3)SCF(3))(2)](O(3)SCF(3)), 3. Because of the larger bite angle of the tbn relative to the hpp ligand, the Re-Re bond distances in 1 and 2 (2.2691(14) and 2.2589(14) Å, respectively) are much longer than that in 3 (2.1804(8) Å). Importantly, electron paramagnetic resonance (EPR) studies at both X-band (~9.4 GHz) and W-band (112 GHz) in the solid and in frozen solution show unusually low g-values (~1.75) and the absence of zero-field splitting, providing direct evidence for the presence of one metal-based unpaired electron for both 1 and 3. These spectroscopic data suggest that the unsymmetrical 5-/6-membered ligand leads to the formation of isomers, as shown by significantly broader EPR signals for 1 than for 3, even though both compounds possess what appears to be similar ideal crystallographic axial symmetry on the X-ray time scale.

Binding two quadruply bonded dimolybdenum units [Mo(2)(DAniF)(3)](+) (DAniF=N,N'-di-p-anisylformamidinate) with two chalcogen atoms generated two molecules with a central core composed of a cyclic six-membered [Mo(2)](2)(μ-EH)(2) species (E=S in 1 and O in 3, and [Mo(2)] is a quadruple-bonded [Mo(2)(formamidinate)(3)] unit). Aerobic oxidation of 1 and 3 followed by concomitant deprotonation gave rise to the corresponding [Mo(2)](2)(μ-E)(2) compounds 2 and 4. The latter show a striking coplanarity and near-bond equalization of the Mo/E cluster. The oxidized species 2 and 4 are diamagnetic in the measured temperature range of 5 to 300 K, which is somewhat unexpected for molecules that have dimetal units with a σ(2)π(4)δ(1) electronic configuration. This suggests there are strong interactions between the dimolybdenum units through the E atoms. The large electronic delocalization of the δ electrons over the entire Mo/E core is supported by the exceptionally large potential separation for the two successive one-electron reductions of the linked Mo(2)(5+) units from the oxidized species (ΔE(½)=1.7 V for the sulfur analogue). This large electronic delocalization has an important effect on the NMR spectroscopic signals for the two sets of methine (N-(CH)-N) protons from the DAniF ligands. Those essentially parallel to the core, H(∥), and those essentially perpendicular to the core, H(⊥), exhibit downfield and upfield chemical shifts, respectively, that are separated by δ=1.32 ppm. The structural, electronic, magnetic, and chemical behaviors for 2 and 4 are consistent with aromaticity, with the [Mo(2)E(2)Mo(2)] cores that resemble the prototypical benzene molecule. Theoretical studies, including DFT calculations, natural bond orbital (NBO) analyses, and gauge-independent atomic orbital (GIAO) NMR spectroscopic calculations, are also consistent with the aromaticity of the [Mo(2)](2)(μ-E)(2) units being promoted by d(δ)(Mo(2))-p(π)(E) π conjugation. The cyclic π conjugation of the central moiety in 2 and 4 involves a total of six electrons with 2e from δ(Mo(2)) and 4e from p(π)(E) orbitals, thereby conforming to Hückel's rule when electrons in the MOs with δ character are considered part of the delocalized system., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A long-sought metal-metal bonded species with an M(2)(8+) core has been structurally characterized. The diamagnetic compound {[Re(2)(hpp)(3)(OH)(O(3)SCF(3))](2)(μ-O)(2)}(O(3)SCF(3))(2), 2, has two σ(2)π(4) electron-poor triple-bonded Re(2)(8+) units embraced by three bicyclic guanidinate ligands (hpp) and axial OH and triflate groups; the two dimetal units are held together by bridging oxo-groups., (This journal is © The Royal Society of Chemistry 2011)

Four Re(2)(6+) paddlewheel compounds with equatorial bicyclic guanidinate ligands and two monodentate anions in axial positions show a large change in the metal-metal distance that depends on the bite angle of the ligands and whether there are pi interactions between the dimetal unit and the axial ligands. These processes are accompanied by significant changes in the redox behavior. The two pairs of compounds that have been synthesized are Re(2)(tbn)(4)Cl(2), 1, and Re(2)(tbn)(4)(SO(3)CF(3))(2), 2, as well as Re(2)(tbo)(4)Cl(2), 3, and Re(2)(tbo)(4)(SO(3)CF(3))(2), 4, where tbn is the anion of a bicyclic guanidinate with six- and five-membered rings (1,5,7-triazabicyclo[4.3.0]non-6-ene) and tbo is an analogous species with two five-membered rings (the anion of 1,4,6-triazabicyclo[3.3.0]oct-4-ene). For both 1 and 2 as well as for 3 and 4, the metal-metal distances are shorter for the triflate species than for the chloride analogues because of the π interactions of the Cl with the π bonds of the triply bonded Re(2)(6+) cores compounded by a small but symmetry allowed interaction between the antisymmetric combination of the filled σp orbitals of the chlorine atom and the empty σ* orbital of the metal atoms. In addition there is a significant increase in the Re-Re distance from that in the six/five tbn-membered ring to the five/five-membered tbo species. Electrochemical measurements show two redox processes for each set of compounds corresponding to the uncommon Re(2)(6+) → Re(2)(7+) and Re(2)(7+) → Re(2)(8+) processes, which are strongly affected by the bite angle of the guanidinate ligand as well as the ability of the axial ligands to interact with the π orbitals of the dirhenium unit. For 1 and 3, the first redox couples are at 0.146 and 0.487 V, respectively, while for 2 and 4 these are at 0.430 and 0.698 V, respectively.

Syntheses and characterization of two Ru(2)(6+) paddlewheel compounds having very different magnetic behavior are reported. The compounds Ru(2)(tbn)(4)Cl(2), 1, and Ru(2)(tbo)(4)Cl(2), 2 (where tbn = the anion of 1,5,7-triazabicyclo[4.3.0]non-6-ene and tbo = the anion of 1,4,6-triazabicyclo[3.3.0]oct-4-ene), have four equatorial bicyclic guanidinate ligands and two chloride ions in axial positions. They show large disparity in Ru-Ru distances of about 0.11 A (2.389(3) and 2.499(3) A at 30 K for 1 and 2, respectively) that is attributed to the divergence in the bite angle of the ligand. Variable temperature structural data show no significant changes in the Ru-Ru distances between 30 and 213 K suggesting that the electronic structure remains unchanged in this temperature range for both compounds. Magnetic studies of 1 indicate there are two unpaired electrons at room temperature but the compound behaves as essentially diamagnetic at approximately 2 K. Compound 2 is non-magnetic across all temperatures in the range of 2 to 300 K. Density functional theory calculations suggest a pi(4)pi*(4)delta(2) electronic configuration for 2, while the magnetic behavior and structural data for 1 are consistent with a sigma(2)pi(4)delta(2)pi*(2) electronic configuration. This shows the importance of the ligand bite angle in determining the electronic configuration of the diruthenium unit and a way to tune magnetic behavior.

We report an investigation of complexes of the type M(2)(dmp)(4) (M = Mo, Cr; dmp = 2,6-dimethoxyphenyl) using resonance Raman (RR) spectroscopy, Cr isotopic substitution, and density functional theory (DFT) calculations. Assignment of the Mo-Mo stretching vibration in the Mo(2) species is straightforward, as evidenced by a single resonance-enhanced band at 424 cm(-1), consistent with an essentially unmixed metal-metal stretch, and overtones of this vibration. On the other hand, the Cr(2) congener has no obvious metal-metal stretching mode near 650-700 cm(-1), where empirical predictions based on the Cr-Cr distance as well as DFT calculations suggest that this vibration should appear if unmixed. Instead, three bands are observed at 345, 363, and 387 cm(-1) that (a) have relative RR intensities that are sensitive to the Raman excitation frequency, (b) exhibit overtones and combinations in the RR spectra, and (c) shift in frequency upon isotopic substitution ((50)Cr and (54)Cr). DFT calculations are used to model the vibrational data for the Mo(2) and Cr(2) systems. Both the DFT results and empirical predictions are in good agreement with experimental observations in the Mo(2) complex, but both, while mutually consistent, differ radically from experiment in the Cr(2) complex. Our experimental and theoretical results, especially the Cr isotope shifts, clearly demonstrate that the potential energy of the Cr-Cr stretching coordinate is distributed among several normal modes having both Cr-Cr and Cr-ligand character. The general significance of these results in interpreting spectroscopic observations in terms of the nature of metal-metal multiple bonding is discussed.

Variable temperature structural and EPR studies are reported on the paddlewheel compound [Os(2)(hpp)(4)Cl(2)]PF(6), 1, (hpp = the anion of the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) that contains a rare M(2)(7+) species, with the goal of determining whether the unpaired electron resides in a metal- or ligand-based molecular orbital. Crystallographic studies show that the Os-Os distance in 1 remains essentially unchanged from 213 to 30 K, which is consistent with no changes in electronic structure in this range of temperature. It is noteworthy that the metal-metal distance in 1 is about 0.05 A shorter than that in the precursor Os(2)(hpp)(4)Cl(2), which is consistent with the loss of an electron in a delta* orbital. EPR spectra of 1 were measured in dilute frozen solution, powder, and single crystals. The spectra were observable only below about 50 K, with an exceptionally large line width, approximately 3,750 gauss, for a powdered sample, due to dipolar interactions and to short relaxation times. There is a very small average g value of approximately 0.750 and a cylindrical symmetry about the Os-Os bond. These data are consistent with the unpaired electron orbital having a large L value, such as that of a delta* orbital. The combination of X-ray structural data, the short relaxation time, and the magnetic data provide strong evidence that the unpaired electron in this nine-electron Os(2)(7+) species is localized in a metal-based orbital with this electron residing predominantly in a delta* orbital rather than in a pi* orbital and, thus, having an electronic configuration of sigma(2)pi(4)delta(2)delta*.

Depending on conditions the reactions of [Mo(2)(cis-DAniF)(2)(NCCH(3))(4)](BF(4))(2) (DAniF = N,N'-di-p-anisylformamidinate) with solutions containing thiocyanate anions lead to two compounds: a quadruple-bonded dinuclear species 1, (Bu(n)(4)N)(2)[Mo(2)(cis-DAniF)(2)(NCS)(4)], and a molecular pair 3, [Mo(2)(cis-DAniF)(2)](2)(mu(1,3)-NCS)(4). The latter has a cuboidal structure having two (cis-DAniF)(2)Mo(2)(2+) units, [Mo(2)], with four thiocyanate groups bridging two [Mo(2)] units in an end-to-end fashion in which the N and S atoms serve as the bridging units. On the contrary, the structure of the cyanate isomer, [Mo(2)(cis-DAniF)(2)](2)(mu(1,1)-NCO)(4) (2), shows an end-on binding of the cyanate linkers. Various physical measurements of 2 and its oxidized species 2.PF(6) indicate that there is strong electronic communication between the two dimetal cores. For 1, two reversible oxidation processes were observed in the cyclic voltammogram corresponding to the successive oxidation to 1(+) and an uncommon 1(2+) species that has a triple-bonded Mo(2)(6+) core. DFT calculations indicate that the antibonding character between the Mo-Mo delta orbitals and thiocyanate p orbitals plays a very important role in elevating the HOMO delta orbital energy that allows formation of the dication. A selenium isomer of 3 was also studied. In both the thiocyanate and selenocyanate bridged dimers of dimers, in which the pseudohalide bridges bind the two dimetal units in an end-to-end fashion, long separations between the dimetal units are observed, and these generate very weak electronic interactions.

A dimer of dimers containing two quadruply bonded [Mo(2)(DAniF)(3)](+) units (DAniF = N,N'-di(p-anisyl)formamidinate) linked by the S-donor linker, dimethyldithiooxamidate was synthesized, structurally characterized, and electronic communication was probed. The core of [Mo(2)(DAniF)(3)](2)(C(2)S(2)N(2)Me(2)), 1, formed by the Mo(2)NSC(2)SNMo(2) atoms shows two fused but non planar six-membered rings, which differs from that of the beta form of dimethyloxamidate analogue that has a heteronaphthalene-type structure (Cotton, F. A.; Liu, C. Y.; Murillo, C. A.; Villagran, D.; Wang, X. J. Am. Chem. Soc. 2004, 126, 14822). For these two analogous compounds electronic coupling between the two [Mo(2)] units, as determined by electrochemical measurements, diminishes considerably upon replacement of O-donor by S-donor atoms (DeltaE(1/2) = 531 mV and 440 mV, respectively). This suggests that the non planar conformation of the linker in 1 hampers a pathway leading to pi conjugation. Density functional theory (DFT) calculations show that the highest occupied molecular orbitals HOMO-HOMO-1 energy gap of 0.12 eV for 1 is much smaller than that of 0.61 eV for the O-donor analogue, which is consistent with the electrochemical data.

Background: Neointimal thickening is the major cause of restenosis after carotid endarterectomy (CEA) and carotid stenting. The biologic behavior of these lesions is regulated by the interaction between smooth muscle cells (SMCs), endothelial cells (ECs), and extracellular matrix (ECM) proteins. Although the contribution of the cellular components of neointimal lesions has been extensively studied, the role of the ECM proteins in lesion remodeling is less well defined., Methods: We examined primary and restenotic carotid endarterectomy specimens to determine their cellular morphology. Tissue was also preserved for protein extraction for Western immunoblotting and mRNA for RT-PCR and cDNA microarray analysis., Results: All primary lesions demonstrated the features of complex atherosclerotic plaque. Restenotic lesions were composed of SMCs embedded in ECM. Microarray analysis demonstrated altered expression of 13 of 96 genes. Eight genes were increased more than 3-fold and five genes were decreased more than 3-fold in primary plaque compared with restenotic lesions. RT-PCR confirmed alpha2-, alpha6-, and beta3-integrin gene expression in reference tissue, primary plaque, and restenotic lesions, with the greatest expression in primary plaque. Primary plaque demonstrated increased protein expression of plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteinase (TIMP-1). By zymography, pro-MMP-2, pro-MMP-9 levels, and MMP-2 activity were also increased in primary plaque compared with reference and restenotic tissues., Conclusions: The decreased integrin expression and protease activity in restenotic lesions versus primary carotid plaques suggests that the neointimal lesions were in a quiescent phase. These alterations in protein expression and protease activity demonstrate the importance of proteinase/inhibitor imbalance in regulating plaque remodeling.

Depending on the number of interstitial solvent molecules, n, crystals of the linear chain compound Co(3)(dipyridylamide)(4)Cl(2) x nCH(2)Cl(2) adopt either symmetrical or unsymmetrical metal chain structures. We explore here the possible reasons for such behavior using Hirshfeld surface analysis of intermolecular interactions as well as the charge density determined from 100(1) K X-ray diffraction data on the unsymmetrical complex Co(3)(dipyridylamide)(4)Cl(2) x 2.11 CH(2)Cl(2), u-1, and crystal structures of u-1 determined from single crystal synchrotron X-ray diffraction data at 20, 150, and 300 K. The new crystal structures are compared with previous structural results on a crystal with slightly different solvent content. This change in solvent content only affects the bond distances to atom Co(3), which are also strongly affected by temperature changes due to a spin crossover transition. Large differences in intermolecular interactions are revealed by the Hirshfeld surface analysis between symmetrical (s-1) and unsymmetrical (u-1) crystal solvates, suggesting that the molecular isomerism is strongly influenced by crystal packing effects. Topological analysis of the static electron density of u-1 suggests that there is direct metal-metal bonding for both the shorter Co(1)-Co(2) and the longer Co(2)-Co(3) contact. The approximate description of the system as a (Co(2))(2+)-dimer and an isolated Co(2+)-ion is reflected in the character of the metal-ligand interactions, which are more ionic for the isolated Co(3) atom, and the topological charges Co(1)(+0.50), Co(2)(+0.77), and Co(3)(+1.36). The two termini of u-1 are found to be very different, both in terms of structural surroundings as well as topology. The central Co(2) atom is similar to a cobalt atom in a tetragonally distorted octahedral environment resulting in preferred occupancy in the t(2g) orbitals. The Co(1) atom has significant deformation in the xz and yz planes (z along the chain axis, x and y toward ligands) reflecting covalent interactions with the terminal chlorine atom Cl(1). The Co(3) atom has a relatively high occupancy of the d(x(2)-y(2)) orbital and a relatively low occupancy of the d(xy) orbital confirming that these orbitals are involved in the spin crossover process and predominantly responsible for the observed variation in bond lengths with temperature.

Full metal bonding: The reduction of a six-coordinate, mononuclear Werner-type iron(II) complex (see scheme) resulted in the isolation of a compound with an extraordinarily rare, unsupported Fe-Fe bond having an experimental Fe-Fe distance of 2.6869(6) A and a calculated bond order of 0.5.

The relative intensity of photonic modes in microcavity pillars with embedded self-assembled quantum dots is shown to be a sensitive function of quantum dot dipole orientation and position. This is deduced from a comparison of experiment and calculated intensities of light emission for many nominally identical pillars. We are able to obtain the overall degree of in-plane polarization of the quantum dot ensemble and also to obtain information on the degree of polarization along the growth axis.

The title complex, [Nb(C(7)H(12)N(3))(4)]PF(6), features chelating hpp anions (hpp is 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrim-idine) that define a distorted dodeca-hedral coordination geometry based on an N(8) donor set. The Nb atom is situated on a site of symmetry , and the PF(6) (-) anion has crystallographic fourfold symmetry.

Oxidation of the molybdate-linked pair having two quadruply bonded Mo(2)(4+) units, [Mo(2)(DAniF)(3)](2)(micro(2)-MoO(4)), (DAniF = N,N'-di-(p-anisyl)formamidinate) leads to the formation of a species consisting of three oxidized Mo(2)(5+) units connected by two micro(3)-MoO(4)(2-) dianions, {[Mo(2)(DAniF)(3)](3)(micro(3)-MoO(4))(2)}(2+). This cation displays overall D(3) point group symmetry due to a slight twisting of the three Mo(2)(5+) units about the threefold symmetry axis. This distortion removes all mirror symmetry but preserves all C(2) axes orthogonal to the unique C(3) axis. Cyclic voltammetry of {[Mo(2)(DAniF)(3)](3)(micro(3)-MoO(4))(2)}(2+) in CH(2)Cl(2) reveals three reversible one-electron redox processes, corresponding to successive reduction of each of the three Mo(2)(5+) units, with DeltaE(1/2) separations of 0.36 V and 0.41 V.

Density functional theory is used to explore the electronic states involved in the remarkable two-step spin crossover (S = 0 --> S = 1 --> S = 2) in the cationic extended metal atom chain [Co(3)(dpa)(4)Cl(2)](+) (dpa = the anion of 2-dipyridylamine) (R. Clérac, F. A. Cotton, K. R. Dunbar, T. Lu, C. A. Murillo and X. Wang, J. Am. Chem. Soc., 2000, 122, 2272). The calculations are consistent with a model in which all three spin states share one common feature-a vacancy in the d(xy) orbital on the central cobalt atom which is stabilised by pi donation from four amide groups. As a result, all three can be considered to contain a Co(2+)-Co(3+)-Co(2+) chain. The singlet and triplet states arise from antiferromagnetic and ferromagnetic coupling, respectively, between the unpaired electron in this d(xy) orbital and another localised entirely on the terminal cobalt centres (the antisymmetric combination of Co d(z(2))). The singlet-triplet transition does not, therefore, populate any additional antibonding orbitals, and as a result the structure is almost invariant around the characteristic temperature of the singlet-triplet transition. In the most stable quintet, in contrast, the symmetry of the Co-Co-Co chain is broken, giving rise to a localised high-spin Co(II) centre (S = 3/2), ferromagnetically coupled to a Co(III)-Co(II) dimer (S = 1/2). The structural changes associated with this transition are apparent in the X-ray data in subtle changes in both Co-N and Co-Cl bond lengths, although their magnitude is damped by the relatively low population (18%) of the quintet even at 300 K.

Ligands derived from N-CH(3) substituted benzoquinonemonoimines are exceedingly good facilitators of electronic communication between two quadruply bonded dimolybdenum units and provide record values for comproportionation constants.

Two neutral compounds having [Mo2] units linked by squarate dianions, [Mo2(DAniF)3]2(mu4-C4O4) (DAniF = N,N'-di(p-anisyl)formamidinate) (1) and [Mo2(DmCF3F)3]2(mu4-C4O4) (DmCF3F = N,N'-di(m-trifluoromethylphenyl)formamidinate) (2), as well as the singly oxidized compound {[Mo2(DmCF3F)3]2(mu4-C4O4)}SbF6 (3) and the doubly oxidized species {[Mo2(DAniF)3]2(mu4-C4O4)}(TFPB)2 (TFPB = [B(3,5-(CF3)2C6H3)4]-) (4), were synthesized and structurally characterized. Electrochemical measurements of the two neutral species showed only very weak electronic interactions between the two dimolybdenum units linked by the squarate anion in contrast to what was observed in dioxolene analogues having C6 instead of C4 rings (J. Am. Chem. Soc. 2006, 128, 3281) which led to differences in comproportionation constants of over 108. In the squarate species, the pi electrons are localized within the carbonyl and dimetal units in the heterometallic six-membered Mo2O2C2 rings to minimize the antiaromaticity in the central C4 square. The oxidized species 3 and 4 are electronically localized in the time scale of the physical measurements. Calculations at the DFT level suggested that the energy mismatch of the frontier orbitals of the linker and dimetal units contributes to the weak communication between the Mo2 units. For the doubly oxidized complex 4, DFT calculations gave a J value of -130 cm(-1) which suggests that the two unpaired electrons are only weakly antiferromagnetically coupled, as shown by magnetic studies (J = -121 cm(-1)).

A tetranuclear cluster containing two quadruply bonded cis-Mo2(DAniF)2 units (DAniF = N,N'-di-p-anisylformamidinate) linked by four hydroxide groups (1) was obtained by hydrolysis of [Mo2(cis-DAniF)2](mu-OCH3)4. Analogous compounds linked by two bidentate bridges (o-O2C6H4 for 2, o-O2C10H6 for 3, and o-S2C6H4 for 4) were synthesized by direct assembly of the corner species precursor [Mo2(cis-DAniF)2(NCCH3)4](BF4)2 and the respective protonated ligands. All four compounds were characterized by X-ray crystallography. Cyclic voltammograms of the O-linked compound 2 and the S analogue 4 show two reversible one-electron-oxidation processes with potential separations (DeltaE(1/2)) of 474 and 776 mV, respectively. The large increase of about 300 mV in DeltaE(1/2) for the S analogue relative to that of the O compound is consistent with a large increase in electronic communication. This enhancement occurs despite the increase of ca. 0.45 A in nonbonding separation between the midpoints of the Mo2 units, which changes from 3.266 A in 2 to 3.72 A in 4, and the increase of ca. 0.4 A in M-E distances as E changes from O to S. Density functional theory calculations show that the increase in electronic communication between the metal centers in 4 is due to a superexchange pathway involving d and p orbitals in the linker E atoms that is less important in 2.

Six very soluble paddlewheel compounds containing Mo2n+ units, n = 4, 5, 6, and two alkyl-substituted bicyclic guanidinate ligands have been synthesized. The quadruply bonded complexes with n = 4, Mo2(TMhpp)4 and Mo2(TEhpp)4, (TMhpp = the anion of 3,3,9,9-tetramethyl-1,5,7-triazabicyclo[4.4.0]dec-4-ene and TEhpp = the anion of 3,3,9,9-tetraethyl-1,5,7-triazabicyclo[4.4.0]dec-4-ene) are easily oxidized. The electrode potentials in THF are -1.08 and -1.17 V vs. Ag/AgCl, respectively, for the Mo(2)(5+/4+) couple. These potentials are in accord with the low ionization potentials for the quadruply bonded compounds. Because of the high solubility of the Mo(2)(4+) compounds in most common organic solvents they are attractive candidates for use as strong reducing agents in homogeneous systems.

Structures of compounds having two dimolybdenum units Mo2(DAniF)3+ (DAniF = N,N'-di-p-anisylformamidinate) connected by unsubstituted oxamidate (1) and dithiooxamidate (2) linkers are isomorphous, and the cores of the molecules are planar because of two intramolecular hydrogen bonds within the linkers. Molecular mechanics calculations show a barrier of rotation along the C-C bond of approximately 10 kcal x mol(-1), which suggests that planar conformations are also expected in solution. Changing the two oxygen atoms in the linker of 1 to sulfur atoms results in a significant enhancement of the electronic coupling between the dimetal units (Delta(E1/2) = 204 mV for 1 and 407 mV for 2). The electronic spectrum of 2 shows an intense low energy (600 nm) metal-to-ligand charge transfer (MLCT) band, whereas that for 1 shows only a weak absorption band at 460 nm. DFT calculations on models 1' and 2', in which the anisyl groups were replaced by hydrogen atoms, show that the energy of the pi* orbital of the linker is much lower for 2'. This allows dpi-ddelta interactions from the electrons in the delta orbitals of the Mo2 unit to the sulfur atom that in turn facilitates an electron hopping pathway.

Hydride anions, H-, have been found to cause the assembly of dimolybdenum units [Mo2(cis-DAniF)2]2+, DAniF = N,N'-di(p-anisyl)formamidinate, forming a tetranuclear complex [Mo2(cis-DAniF)2]2(mu-H)4 (1) with an Mo4H4 core that may be described as an elongated tetrahedron in which the H atoms are along the four long edges of such tetrahedron and the Mo2 units are along the short edges. The two quadruply bonded dimolybdenum units, separated by only 2.718 A, are essentially orthogonal. This gives the shortest [Mo2]...[Mo2] distance known for complexes with multiple dimolybdenum units. DFT calculations indicate that the energy of a cuboidal isomer is only 3.8 kcal/mol above that of 1, but such an isomer has not been observed.

Two compounds with quadruply bonded Mo2(4+) species having isonicotinate ligands bound through the carboxylate group have been designed to act as anglers by luring metal-containing Lewis acids to bind to the N-pyridyl group. The corner pieces are Mo2(DAniF)3(O2CC5H4N) and cis-Mo2(DAniF)2(O2CC5H4N)2, DAniF=N,N'-di(p-anisyl)formamidinate. The heterometallic molecular rods -Ni(acac)2-and-Rh2(O2CCH3)4- were made by reaction of with Ni(acac)2 and the metal-metal bonded species Rh2(O2CCH3)4, respectively. In these compounds either a mononuclear or a dinuclear species are sandwiched between two molecules of . The cisoid compound has been employed for the synthesis of a molecular rhombus, [-Zn(Cl2)]2. The successful syntheses and isolation of show that the use of corner pieces with angler groups is an excellent approach for making heterometallic supramolecular compounds having a combination of metal-metal bonded units and other metal species.

A crystal-to-crystal transformation of (DAniF)3Mo2(micro-OH)2Mo2(DAniF)3 (1) to (DAniF)3Mo2(micro-O)2Mo2(DAniF)3 (2), where DAniF is the anion (p-anisyl)NC(H)N(p-anisyl), by dioxygen provides rare insight into the deprotonation process effected by dioxygen. In this dimolybdenum system, the conversion occurs without significant loss of crystallinity. Although no intermediates have been directly observed, a compound containing the [(DAniF)3Mo2(micro-OH)(micro-O)Mo2(DAniF)3]+ cation, a proposed intermediate, has been obtained independently. Possible pathways for the overall conversion of 1 to 2 are discussed.

By using stoichiometric amounts of (C5H5)2FePF6, the isomeric neutral diamidate-bridged molecules, alpha- and beta-(DAniF)3Mo2(ArN(O)CC(O)NAr)Mo2(DAniF)3, with Ar = p-MeOC6H4, have been oxidized to give the PF6 salts of the four cations alpha1+, alpha2+, beta1+, and beta2+. All four structures have been accurately determined and, together with supporting evidence from near-IR, EPR, NMR and magnetic susceptibility measurements, it clearly establishes that in the mixed-valent alpha+ species the unpaired electron is localized over only one of the Mo2 units while the alpha2+ cation behaves as a diradical having two Mo25+ units that are essentially uncoupled. However, the beta+ species is fully delocalized, in the time scale of the experiments, with the unpaired electron being equally shared by the two Mo2 units. It displays a HOMO-1 --> SOMO transition at 4700 cm-1 (Deltanu1/2 = 2300 cm-1). Because of strong coupling, the beta2+ species is diamagnetic.

A series of compounds has been made containing quadruply bonded Re2(hpp)4X2 species (hpp = the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2a]pyrimidine), where X is CF3SO3 (1), CF3CO2 (2), and F (3). The distances of 2.1562(7), 2.1711(5), and 2.1959(4) A for 1-3 show significant effects of the sigma and pi electron donating ability of the axial ligands on the metal-metal distance. With the weakly coordinating triflate ligand the Re-Re distance is the shortest for any quadruple bonded species known. In addition to examining the effects of axial ligands on the Re2(hpp)42+ core, our study of the Re2(hpp)43+ core is being extended beyond the preliminary results previously reported in only one compound [Re2(hpp)4Cl2]PF6 (Dalton Trans. 2003, 1218). We now report the structural characterization by both X-ray and neutron diffraction of the compound [Re2(hpp)4F](TFPB)2, 4 (TFPB = the anion tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), and a detailed study by EPR spectroscopy of [Re2(hpp)4Cl2]PF6 at 9.5, 34.5, and 95 GHz frequencies, using dilute fluid solutions, frozen glass, and neat powder, show that the unpaired electron in the [Re2(hpp)4Cl2]+ ion is in an MO of predominant metal character with little mixing from the guanidinate ligands.