Apical Site Research Articles

CD13 orients the apical-basal polarity axis necessary for lumen formation

Polarized epithelial cells can organize into complex structures with a characteristic central lumen. Lumen formation requires that cells coordinately orient their polarity axis so that the basolateral domain is on the outside and apical domain inside epithelial structures. Here we show that the transmembrane aminopeptidase, CD13, is a key determinant of epithelial polarity orientation. CD13 localizes to the apical membrane and associates with an apical complex with Par6. CD13-deficient cells display inverted polarity in which apical proteins are retained on the outer cell periphery and fail to accumulate at an intercellular apical initiation site. Here we show that CD13 is required to couple apical protein cargo to Rab11-endosomes and for capture of endosomes at the apical initiation site. This role in polarity utilizes the short intracellular domain but is independent of CD13 peptidase activity.

Longitudinal investigation of idiopathic osteosclerosis lesions of the jaws in a group of Chinese orthodontically-treated patients using digital panoramic radiography

Background/purposeIdiopathic osteosclerosis (IO) is an intraosseous lesion of asymptomatic, non-expansive, radiopaque. The study aimed to investigate the prevalence and morphometric parameters of IO in orthodontic patients and variations in longitudinal observations and to assess the relationship between IO and orthodontic treatment. Materials and methodsFive hundred and seventy-one orthodontically-treated patients were reviewed. A cross-sectional study was performed with the evaluated parameters, including the age and sex of patients, as well as the number, shape, location and morphometric data of IO observed in panoramic radiography. Long-term behaviour of IO and orthodontic tooth movement were also observed. Also, a control group was set up for comparisons. ResultsSixty-eight (11.3%) patients had 78 lesions all in the mandible with premolar/molar preference and no sex predilection. Lesions were located more commonly at apical and separate sites related to teeth. A large majority of lesions enlarged in the 10–19 years old group, while most lesions had no change in the 30–39 years old group. Hindrances of tooth movement and external root resorption around IO were not found in affected patients. ConclusionIO is labile lesion that may develop in early stages of life, with little change occurring once the affected individual is mature and being relatively stable in the middle stage of life. Our study supports the hypothesis that IO may be developmental anatomic variations of normal bone. However, no obvious association between IO and orthodontic treatment was found in patients, which may be due to the limitations of two-dimensional shooting of panoramic radiography and the sample size.

Bone Density around Titanium Dental Implants Coating Tested/Coated with Chitosan or Melatonin: An Evaluation via Microtomography in Jaws of Beagle Dogs

Peri-implant bone density plays an important role in the osseointegration of dental implants. The aim of the study was to evaluate via micro-CT, in Hounsfield units, the bone density around dental implants coated with chitosan and melatonin and to compare it with the bone density around implants with a conventional etched surface after 12 weeks of immediate post-extraction placement in the jaws of Beagle dogs. Six dogs were used, and 48 implants were randomly placed: three groups—melatonin, chitosan, and control. Seven 10 mm × 10 mm regions of interest were defined in each implant (2 in the crestal zone, 4 in the medial zone, and 1 in the apical zone). A total of 336 sites were studied with the AMIDE tool, using the Norton and Gamble classification to assess bone density. The effect on bone density of surface coating variables (chitosan, melatonin, and control) at the crestal, medial, and apical sites and the implant positions (P2, P3, P4, and M1) was analyzed at bivariate and multivariate levels (linear regression). Adjusted effects on bone density did not indicate statistical significance for surface coatings (p = 0.653) but did for different levels of ROIs (p < 0.001) and for positions of the implants (p = 0.032). Micro-CT, with appropriate software, proved to be a powerful tool for measuring osseointegration.

MO339KIDNEY DERIVED APOM AND ITS ROLE IN ACUTE KIDNEY INJURY

Abstract Background and Aims Acute kidney injury is a severe disease with detrimental outcomes. The underlying ethiology is still elusive and besides dialysis, treatment options are poor. Apolipoprotein M (apoM) is mainly expressed in liver and in proximal tubular epithelial cells in the kidney. In plasma, apoM associates with HDL particles via a retained signal peptide. ApoM is a carrier of sphingosine-1-phosphate (S1P), a small bioactive lipid involved in e.g. angiogenesis, lymphocyte trafficking, and vascular barrier function. Recently, it was shown that apoM/S1P protects against development of liver and lung fibrosis. In urine, apoM is normally undetectable in both wild type mice and healthy humans. However, lack of megalin receptors in proximal tubuli induces loss of apoM into the urine. The biological function of kidney-derived apoM is unknown, but it has been hypothesized that apoM might be secreted to the pre-urine to sequester molecules, such as S1P, from secretion. The aim of this study was to unravel the role of apoM in kidney biology and in acute kidney injury. Method A novel kidney specific human apoM transgenic mouse (RPTEC-hapoMTG), was generated by expressing human apoM under the control of the proximal tubular epithelial cell specific Sglt2 promoter. The effect of kidney specific apoM overexpression on acute kidney injury was accessed by inducing either cisplatin or ischemia/reperfusion injury. Further, a stable cell line of HK-2 cells overexpressing hapoM (HK-2hapoM-TG) was generated and the cells were cultured on transwells to assess the secretion of apoM to respectively the apical and basolateral site. Results hapoM was present in plasma from RPTEC-hapoMTG mice (mean 0.18 μM), indicating that kidney-derived apoM can be secreted to plasma. When assessing the secretion of hapoM from proximal tubular epithelial cells in vitro, studies support that apoM can be secreted to both the apical (urine) and basolateral (blood) compartment. No differences in kidney injury markers (plasma urea and creatinine) between RPTEC-hapoMTG and wild type (WT) mice subjected to cisplatin injections, or in kidney injury score determined by histological evaluation was found. Similar, we could not detect any histological difference between RPTEC-hapoMTG and WT mice after ischemia/reperfusion injury, and overexpression of hapoM did not affect kidney gene expression of inflammatory markers (i.e. IL6, MCP-1) compared to WT mice. Conclusion Our study suggests that apoM can be secreted to both the apical and basolateral compartment, supporting a role for apoM in sequestering molecules from secretion in urine. Transgenic overexpression of apoM in proximal tubular epithelial cells of mice did not protect against acute kidney injury.

Endocardial pacing is not haemodynamically superior to trans-coronary sinus epicardial pacing in cardiac resynchronization therapy: the Endo-Epi CRT study

Abstract Funding Acknowledgements Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Medtronic Background Cardiac resynchronization therapy (CRT) conventionally involves trans-coronary sinus, epicardial left ventricular (LV) pacing. Some studies have suggested that endocardial LV pacing may be superior to epicardial LV pacing. Objectives To compare the acute haemodynamic effects of CRT when delivered from endocardial (Endo-CRT) and epicardial LV stimulation sites (Epi-CRT). Methods and results Sixteen CRT recipients (aged 70.4 ± 10.1 years [mean ± SD], 62.5% male, QRS: 156.5 ± 16.1 ms, LBBB in 13 [81.3%]) in sinus rhythm underwent intra-procedural measurements of the rate of rise of LV pressure (dP/dtmax) during Endo- and Epi-CRT (RADI pressure wire). Epi-CRT was delivered in basal, mid and apical positions. The Endo-CRT pacing site was chosen using iterative, biplane fluoroscopic views, to target the same position as the Epi-CRT site on the endocardium (see Figure A). Compared to AAI pacing (10 beats per minute above intrinsic rate), both Endo-CRT and Epi-CRT led to an increase in LV dP/dtmax (6.52 ± 8.90% and 6.15 ± 7.97% respectively, both p < 0.001). There were no significant differences in the change in LV dP/dtmax (ΔLV dP/dtmax) between Endo-CRT and Epi-CRT at basal (p = 0.54), mid (p = 0.78) or apical LV stimulation sites (p = 0.12) [Figure B]. Conclusions Endo-CRT is not haemodynamically superior to Epi-CRT. Abstract Figure.

Evidence for a percolative Mott insulator-metal transition in doped Sr2IrO4

Despite many efforts to rationalize the strongly correlated electronic ground states in doped Mott insulators, the nature of the doping induced insulator to metal transition is still a subject under intensive investigation. Here we probe the nanoscale electronic structure of the Mott insulator Sr$_2$IrO$_{4-\delta}$ with low-temperature scanning tunneling microscopy and find enhanced local density of states (LDOS) inside the Mott gap at the location of individual apical oxygen site defects. We visualize paths of enhanced conductance arising from the overlapping of defect states which induces finite LDOS at the Fermi level. By combining these findings with the typical spatial extension of isolated defects of about 2~nm, we show that the insulator to metal transition in Sr$_2$IrO$_{4-\delta}$ is of percolative nature.

Updated Echocardiographic Effects of Long Term Pacing on Left Ventricle and Left Atrial Function in Patients with Congenital Heart Block: Outflow Tract vs. Apical Pacing Sites

Updated Echocardiographic Effects of Long Term Pacing on Left Ventricle and Left Atrial Function in Patients with Congenital Heart Block: Outflow Tract vs. Apical Pacing Sites

Fractal analysis as a useful predictor for determining osseointegration of dental implant? A retrospective study

PurposeThe present study aimed at evaluating the effectiveness of fractal analysis on determining the osseointegration of dental implants.Material and methodsIn a single center, retrospective clinical trial, patients with dental implants in the mandibular premolar/molar region, ASA I–II and < 65-year-old patients were included. Orthopantomograph (OPG) were taken before implant surgery (t0), within a week of surgery (t1), and 1 (t2) and 2 (t3) months after surgery, respectively. Three regions of interest (ROIs) from mesial, distal, and apical sites of the implants were chosen and fractal analysis (FA) was conducted with the box-counting algorithm using White and Rudolph’s method.ResultsA total of 39 patients 19 women and 20 men, with a mean age of 52.2 years (52.3 and 52.1 years, respectively) were included. The mean, minimum and maximum values of mesial (roi1), distal (roi2), and apical (roi3) surfaces were compared. The fractal dimension (FD) values of t1 were significantly lower compared with t0 as they decreased during the first week. FD values gradually increased after the first week although never exceeded the FD values of t0. Also, difference between mean FD values of t0 and t3 were found statistically significant (p < 0.05).DiscussionFA is a promising and noninvasive method to predict osseointegration of a dental implant based on dental radiographs, and it can help shorten the total treatment time.

Right ventricular apical and septal pacing: long term impacts on ventricular function

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): The costs of the study were afforded by the researchers. Background In patients requiring permanent pacemaker, in order to protect left and right ventricular functions the optimal pacing site has yet to be determined. Conflicting results exist about septal and apical pacing sites. Aim Our purpose was to evaluate the long term effects of right ventricular apical and septal pacing on left and right ventricular functions. Methods We scanned 378 patients from 2007 to 2012 who received a permanent pacemaker for the treatment of symptomatic bradyarrythmia. As exclusion criteria we identified the patients who did not have an echocardiography before the procedure, those who had co-morbidities which cause reduction in ventricular functions, ejection fraction &amp;lt;%45, patients who died and those who rejected our invitation. 54 women and 66 men were eligible for our study. To determine the patients’ New York Heart Association Class (NYHA) we questioned and did the physical examination. Lead position confirmed by fluoroscopy in two planes, and electrocardiograms were obtained. Finally, we compared the pre-procedural echocardiographic data with our up-to-date findings. Results In sixteen patients the lead placement was inferoseptal and in one hundred and four patients apical site. Median follow up was 9 years. The mean ejection fraction before the implantation was 58,86 ± 4,08 in the apical, and 56,37 ± 8,8 in the septal group (p &amp;lt; 0,05). The long term follow up showed that these values have been reduced, 56,66 ± 8,38 for the apical group and 51,33 ± 13,94 for the septal group, respectively (p &amp;lt; 0,05). Placing the right ventricular lead in both septal and apical site resulted in reduced tricuspid annular plane systolic excursion (from mean 2,25 to 2,18, (p &amp;lt; 0,05)), and in increased systolic pulmonary artery pressure (from 35,46 ± 9,93 to 39,84 ± 11,21 (p &amp;lt; 0,05)). There were no differences regarding the mitral and tricuspid insufficiencies, and diastolic functions before the implantation and long term follow up. These findings were independent of neither the etiology of implanting the pacemaker nor the underlying diseases. Conclusion These two selective ventricular pacing sites caused a reduction in both left and right ventricular functions. Despite the ejection fraction declines, most of these patients have a good quality of life, without symptoms and signs of heart failure. But certainly, there is emerging need for more randomized trials in order to describe the optimal RV pacing site. The main purpose must be preserving better ventricular functions in patients requiring permanent ventricular pacing.

Synthesis, spectroscopic, thermal decomposition, DFT studies and antibacterial activity of uracil cobalt(III)dimethylglyoximato complexes

ABSTRACT Three new mixed-ligand complexes of the type [Co(Hdmg)2(Ura)X], where Hdmg = dimethylglyoximato anion, Ura = uracil, and X = Cl, Br, or I, were synthesized and characterized using elemental analyses, molar conductance, IR and UV–visible spectroscopies. The molar conductance values indicate that the compounds are not electrolytes. The thermal decomposition was studied using TG and DSC techniques. It is shown that the decomposition process of all complexes occurs in three steps. The IR spectra of the complexes show that the four nitrogen atoms of oxime functions of the two Hdmg mono-anions are linked to the central atom, the whole moiety forming an equatorial plane. Uracil (-N) and halogen occupy the apical sites in the trans position in an octahedral arrangement. The absorption bands observed in the UV-visible spectra are due either to intra-ligand transitions, ligand-metal charge transfer transitions or d -d transitions. Density Functional Theory (DFT) calculations have been successfully used to investigate the nature of the bonding in the complexes. The antibacterial activities of the complexes and their combinations were tested against Escherichia coli, pseudomonas aeruginosa, klebsiella pneumonia, proteus mirabilis, staphylococcus aureus, and bacillus cereus. The combination of iodo and bromo complexes showed a strong inhibitory power compared to the other combinations and to the free complexes.

Crystallographic and Computational Electron Density of dx2-y2 Orbitals of Azo-Schiff Base Metal Complexes Using Conventional Programs.

The crystal structures of two azobenzene derivative Schiff base metal complexes (new C44H40CuN6O2 of P-1 and known C44H38MnN6O7 of P21/c abbreviated as Cu and Mn, respectively) were (re-)determined experimentally using conventional X-ray analysis to obtain electron density using a PLATON program. Cu affords a four-coordinated square planar geometry, while Mn affords a hexa-coordinated distorted octahedral geometry whose apical sites are occupied by an acetate ion and water ligands, which are associated with hydrogen bonds. The π-π or CH-π and hydrogen bonding intermolecular interactions were found in both crystals, which were also analyzed using a Hirshfeld surface analysis program. To compare these results with experimental results, a density functional theory (DFT) calculation was also carried out based on the crystal structures to obtain calculated electron density using a conventional Gaussian program. These results revealed that the axial Mn-O coordination bonds of Mn were relatively weaker than the in-plane M-N or M-O coordination bonds.

Infection of polarized bovine respiratory epithelial cells by bovine viral diarrhea virus (BVDV)

ABSTRACT Bovine viral diarrhea virus (BVDV) is affecting cattle populations all over the world causing acute disease, immunosuppressive effects, respiratory diseases, gastrointestinal, and reproductive failure in cattle. The virus is taken up via the oronasal route and infection of epithelial and immune cells contributes to the dissemination of the virus throughout the body. However, it is not known how the virus gets across the barrier of epithelial cells encountered in the airways. Here, we analyzed the infection of polarized primary bovine airway epithelial cells (BAEC). Infection of BAEC by a non-cytopathogenic BVDV was possible via both the apical and the basolateral plasma membrane, but the infection was most efficient when the virus was applied to the basolateral plasma membrane. Irrespective of the site of infection, BVDV was efficiently released to the apical site, while only minor amounts of virus were detected in the basal medium. This indicates that the respiratory epithelium can release large amounts of BVDV to the environment and susceptible animals via respiratory fluids and aerosols, but BVDV cannot cross the airway epithelial cells to infect subepithelial cells and establish systemic infection. Further experiments showed that the receptor, bovine CD46, for BVDV is expressed predominantly on the apical membrane domain of the polarized epithelial cells. In a CD46 blocking experiment, the addition of an antibody directed against CD46 almost completely inhibited apical infection, whereas basolateral infection was not affected. While CD46 serves as a receptor for apical infection of BAEC by BVDV, the receptor for basolateral infection remains to be elucidated.

Evaluating Incidence, Location, and Predictors of Positive Surgical Margin Among Chinese Men Undergoing Robot-Assisted Radical Prostatectomy.

PurposeTo evaluate the incidence and locations of positive surgical margin (PSM) among Chinese men undergoing RARP and identify the preoperative predictors for PSM.MethodsWe retrospectively identified 393 patients who underwent RARP according to inclusion criteria by single surgeon in our hospital. PSM was defined as the presence of cancer adjacent to inked surface of the specimen and categorized into four groups based on locations: apex, posterolateral, base, and multifocal. Logistic regression analysis was performed to identify the predictors of overall and location-specific PSM.ResultsThe overall PSM rate was 133/393 (34%). The PSM rates for pT2, pT3, and pT4 stage were 63/278 (23%), 50/89 (56%), and 20/26 (77%), respectively. The estimated rates for apical, posterolateral, basal, and multifocal PSM were 8%, 4%, 7%, and 14%, respectively. In univariate analysis, overall PSM related to tPSA, f/tPSA, percentage of positive needles, and Gleason score. Multifocal PSM correlated with smoking history, drinking history, tPSA, f/tPSA, percentage of positive needles, and Gleason score. In multivariate analysis, percentage of positive needles reminded the only independent predictor for overall (OR = 10.5, 95% CI: 2.58–44.4) and basal PSM (OR = 24.0, 95% CI: 3.22–179.4). The f/tPSA (OR = 2.59, 95% CI: 2.18–5.71) and percentage of positive needles (OR = 31.0, 95% CI: 3.17–303) were independent risk factors for multifocal PSM.ConclusionThe multifocal sites were the most common location of positive surgical margin, followed by apical and basal sites among Chinese patients undergoing RARP. The percentage of positive needles was an independent predictor for overall, basal, and multifocal PSM.

Temporal Pitch Perception in Cochlear-Implant Users: Channel Independence in Apical Cochlear Regions.

Two-electrode stimuli presented on adjacent mid-array contacts in cochlear-implant users elicit pitch percepts that are not consistent with a summation of the two temporal patterns. This indicates that low-rate temporal rate codes can be applied with considerable independence on adjacent mid-array electrodes. At issue in this study was whether a similar independence of temporal pitch cues can also be observed for more apical sites of stimulation, where temporal cues have been shown to be more reliable than place cues, in contrast to middle and basal sites. In cochlear-implant recipients with single-sided deafness implanted with long lateral-wall electrode arrays, pitch percepts were assessed by matching the pitch of dual-electrode stimuli with pure tones presented to the contralateral normal-hearing ear. The results were supported with an additional pitch-ranking experiment, in a different subject population with bilateral deafness. Unmodulated pulse trains with 100, 200, and 400 pulses per second were presented on three pairs of adjacent electrodes. Pulses were separated by the minimal interchannel delay (1.7 µs) in a short-delay configuration and by half the pulse period in a long-delay configuration. The hypothesis was that subjects would perceive a pitch corresponding to the doubled temporal pattern for the long-delay stimuli due to the summation of excitation patterns from adjacent apical electrodes, if those electrodes were to activate largely overlapping neural populations. However, we found that the mean matched acoustic pitch of the long-delay pulses was not significantly different from that of the short-delay pulses. These findings suggest that also in the apical region in long-array cochlear-implant recipients, temporal cues can be transmitted largely independently on adjacent electrodes.

A clinical case of single left ventricle in a Holstein calf.

A 15-day-old Holstein calf with lethargy and tachypnea presented to the Veterinary Teaching Hospital at Obihiro University of Agriculture and Veterinary Medicine for evaluation of suspected congenital heart defect. A Levine grade 6 systolic murmur was noted at right apical site auscultation and phonocardiogram also recorded systolic a murmur. Electrocardiography findings include increased R and S waves, R wave split, and negative T waves without arrhythmia. Echocardiography revealed a single ventricle with a trace of the right ventricular wall, atrioventricular valve regurgitation, and turbulent in a single ventricle. Arterial blood analysis showed a marked decrease in oxygen saturation of 78% and oxygen partial pressure of 44 mmHg. Post-mortem examination confirmed the diagnosis of a single left ventricle.

Local ferroelectric polarization in antiferroelectric chalcogenide perovskite BaZrS3 thin films

Bulk chalcogenide perovskite BaZrS3 (BZS), with a direct band gap in visible region, is an important photovoltaic material, albeit with limited applicability owing to its antiferroelectric (AF) nature. Presently, ferroelectric (FE) perovskite-based photovoltaics are attracting enormous attention for environmental stability and better energy conversion efficiency through enhanced charge separation, owing to loss of center of inversion symmetry. We report on antiferroelectric-ferroelectric (AF-FE) phases of BZS thin film, grown with chemical vapor deposition (CVD), using temperature-dependent Raman investigations and first-principles calculations. The origin of FE phases is established from anomalous behavior of A7g ~ 300 cm-1 and B1g5 ~ 420 cm-1 modes, which involves the vibration of atoms at apical site of ZrS6 octahedra. Additionally, below 60 K, B1g1 and B2g2 ( ~ 85 cm-1) modes appear whereas B12g (~ 60 cm-1) disappears to stabilize the Pnma structure against ferroelectricity by local distortion. Here, B2g2 and B1g2 involve vibrations of Ba atoms in AF manner while B1g1 involves, in addition, the rotation of octahedra as well. Our first-principles calculations confirm that FE appears as a result of loss of center of inversion symmetry in ZrS6 octahedra due to existence of oxygen (O) impurities placed locally at apical sites of sulfur (S) atom.

Cyclooctadiene iridium complexes with phosphine, oxo- and aza-pentadienyl ligands

Reaction of [(η4-COD)Ir(Cl)PR´3] (R´ = Ph, 1; Me, 2) with lithium(oxobutadienide) (4) and lithium(2,4-dimethyl-oxopentadienide) (5) affords the η3-oxopentadienyl [(η4-COD)Ir(η3-exo-syn-syn-CH2CHCHCHO)PPh3] (6), the alkenyl carbonyl [(η4-COD)Ir(η1-CHCHMe)(CO)PMe3] (7), and the 2,4-dimethyl-η3-oxopentadienyl [(η4-COD)Ir(η3-exo-syn-anti–CH2CMeCHCMeO)PPh3] (8), as well as the mixture of isomers [(η4-COD)Ir(η3-exo-syn-anti-CH2CMeCHCMeO)PMe3] (9a) and [(η4-COD)Ir(η3-exo-anti-anti-CH2CMeCHCMeO)PMe3] (9b) in a 2:1 ratio, respectively.The synthesis of azapentadienyl compounds obtained from the reaction of [(η4-COD)Ir(Cl)PR´3] (R = Ph, 1; Me, 2; i-Pr, 3) with lithium azapentadienide Li(CH2CHCHCHNR) showed the exclusive η3-exo-syn-syn coordination mode for the azapentadienyl ligands in [(η4-COD)Ir(η3-CH2CHCHCHNR)PR´3] (R = t-Bu, R´= Ph, 13; R´= Me, 14; R´= i-Pr, 15 and R = C6H11, R´= Ph, 16). Novel bridging azapentadienyl ligands in the dinuclear [(η4-COD)Ir(1-3:5-η-μ2-CH2CHCHCHNt-Bu)PMe3][IrCl(η4-COD)] (18) and the iridaazacyclohexadiene [(η4-COD)Ir[μ-(1,5:1-4-η-μ2-CHCHCH2CHNCy)]Ir(η4-COD)] (19) compounds were synthesized by the reaction of [(η4-COD)Ir(μ2-Cl)]2 (17) with 14 or lithium azapentadienide (11), respectively. All chiral heteropentadienyl complexes showed evidence for the lack of symmetry of the nonconjugated unsaturated cyclooctadiene ligands.Compounds 8, 9a, 13, 15, 18 and 19, as well as the side-product, 2-acetyl-1,3,3,5-tetramethyl-5-cyclohexen-1-ol (10), which result of the favorable cycloaddition reaction in the presence of lithium 2,4-dimethyl-oxopentadienide (5), have been structurally characterized by single-crystal X-ray diffraction studies. The parameters for all mononuclear heteropentadienyl crystalline structures show a geometric distorsion from square-pyramidal (SP), where the phosphine ligands are in the apical site, being the highest distorsion observed for the azapentadienyl complexes, compared to pentadienyl and oxopentadienyl analogues.

Synthesis, Structure, and Magnetic Properties of Linear Trinuclear CuII and NiII Complexes of Porphyrin Analogues Embedded with Binaphthol Units

A porphyrin analogue embedded with (S)-1,1′-bi-2-naphthol units was synthesized without reducing optical purity of the original binaphthol unit. This new macrocyclic ligand provides the hexaanionic N4O4 coordination environment that enables a linear array of three metal ions. That is, it provides the square planar O4 donor set for the central metal site and the distorted square planar N2O2 donor set for the terminal metal sites. In fact, a CuII3 complex with a Cu(1)–Cu(2) distance of 2.910 Å, a Cu(1)–Cu(2)–Cu(1′) angle of 174.7°, and a very planar Cu2O2 diamond core was obtained. The variable-temperature 1H-NMR study of the CuII3 complex showed increasing paramagnetic shifts for the naphthyl protons as temperature increased, which suggests strong antiferromagnetic coupling of CuII ions. The temperature dependence of the magnetic susceptibility indicated antiferromagnetic coupling both for the CuII3 complex (J = −434 cm−1) and for the NiII3 complex (J = −49 cm−1). The linear (L)M(µ-OR)2M(µ-OR)2M(L) core in a rigid macrocycle cavity made of aromatic components provides robust metal complexes that undergo reversible ligation at the apical sites of the central metal.

Synchrotron X-Ray Absorption Spectroscopy (XAS) Studies on Structural and Magnetic Properties of T’-Pr&lt;sub&gt;2-x&lt;/sub&gt;Ce&lt;sub&gt;x&lt;/sub&gt;CuO&lt;sub&gt;4&lt;/sub&gt; Nanocrystals

We have succeeded in synthesizing electron-doped cuprates T’-Pr2-xCexCuO4 (PCCO) with x = 0 and 0.10 nanocrystals prepared by the chemically dissolved method. Reduction annealing of the PCCO samples at 700°C under a flowing argon gas atmosphere has been performed for the removal of excess oxygen in the apical sites. The XRD data showed that the reduction annealing process decreases c-axis length indicating successful removal of the excess oxygen. The bond distortion of PCCO including coordination number and bond distance between the absorber atoms with the nearest neighboring atoms (Cu-O) was investigated by extended x-ray absorption fine structure (EXAFS) using Cu K-edge. The implication of our results is discussed on the basis of tremendous influence of oxygen vacancies on the magnetism of the nanosized T’-cuprates at the normal state.

Seven Reversible Redox Processes in a Self-Assembled Cobalt Pentanuclear Bis(triple-stranded helicate): Structural, Spectroscopic, and Magnetic Characterizations in the CoICoII4, CoII5, and CoII3CoIII2 Redox States.

We report on the synthesis and structural characterization of the cobalt pentanuclear helicate complex from the rigid tetradentate bis(2-pyridyl)-3,5-pyrazolate ligand bpp-, namely, [{CoII(μ-bpp)3}2CoII3(μ3-OH)]3+ (13+), in which a trinuclear {CoII3(μ3-OH)} core is wrapped by two {CoII(μ-bpp)3} units. The cyclic voltammogram of 13+ in CH3CN revealed seven successive reversible one-electron waves, in the 0 and -3.0 V potential range, highlighting the remarkable stability of such architecture in several redox states. Two mixed-valent states of this complex, the two-electron-oxidized CoII3CoIII2 (15+) and the one-electron-reduced species CoICoII4 (12+), were generated by bulk electrolyses and successfully characterized by single-crystal X-ray diffraction among the eight redox levels between CoI5 and CoII3CoIII2 that can be accessed under electrochemical conditions. Because of the crystallographic characterization of 15+ and 12+, the five reduction processes located at E1/2 values of -1.63 (13+/2+), -1.88 (12+/+), -2.14 (1+/0), -2.40 (10/-), and -2.60 V (1-/2-) versus Ag/AgNO3 were unambiguously assigned to the successive reduction of each of the five Co(II) ions to Co(I), starting with the three ions located in the central core followed by the two apical ions. The two other redox events at E1/2 values of -0.21 (14+/3+) and -0.11 V (15+/4+) are assigned to the successive oxidation of the apical Co(II) ions to Co(III). The Co(I) complexes are rare, and the stabilization of a Co(I) within a trinuclear μ-hydroxo core in the reduced species, 12+, 1+, 10, 1-, and 12-, is probably the result of the particular structure of this complex in the presence of the two apical sites that maintain the trinuclear core through the six bridging bpp- ligands. The spectroscopic characteristics of 12+, 13+, and 15+ (ultraviolet-visible and X-band electron paramagnetic resonance) are also described as well as their magnetic properties in the solid state.