Investigations of the Effect of the Non-Manganese Metal in Heterometallic-Oxido Cluster Models of the Oxygen Evolving Complex of Photosystem II: Lanthanides as Substitutes for Calcium

We report the syntheses and electrochemical properties of nine new clusters ([LLnMn^(IV)_(3)O_4(OAc)_3(DMF)_n]^+ (Ln = La^3+, Ce^3+, Nd^3+, Eu^3+, Gd^3+, Tb^3+, Dy^3+, Yb^3+, and Lu^3+, n = 2 or 3)) supported by a ligand (L^3–) based on a 1,3,5-triarylbenzene motif appended with alkoxide and pyridine donors. All complexes were obtained by metal substitution of Ca2+ with lanthanides upon treatment of previously reported LMn_3CaO_4(OAc)_3(THF) with Ln(OTf)_3. Structural characterization confirmed that the clusters contain the [LnMn_3O_4] cubane motif. The effect of the redox-inactive centers on the electronic properties of the Mn_3O_4 cores was investigated by cyclic voltammetry. A linear correlation between the redox potential of the cluster and the ionic radii or pKa of the lanthanide metal ion was observed. Chemical reduction of the LMn^(IV)_3GdO_4(OAc)_3(DMF)2 cluster with decamethylferrocene, resulted in the formation of LGdMn^(IV)_2Mn^(III)O_4(OAc)_3(DMF)_2, a rare example of mixed-valence [MMn_3O_4] cubane. The lanthanide-coordinated ligands can be substituted with other donors, including water, the biological substrate

Selectivity of C−H vs. C−F Bond Oxygenation by Homo- and Heterometallic Fe_4, Fe_3Mn, and Mn_4 Clusters

A series of tetranuclear [LM_3(HFArPz)_3OM'][OTf]_2 (M, M' = Fe or Mn) clusters that displays 3-(2-fluorophenyl)pyrazolate (HFArPz) as bridging ligand is reported. With these complexes manganese is demonstrated to facilitate C(sp^2)−F bond oxygenation via a putative terminal metal-oxo species. Moreover, the presence of both ortho C(sp^2)−H and C(sp^2)−F bonds in proximity provides an opportunity to investigate the selectivity of intramolecular C(sp^2)−X bond oxygenation (X = H or F) in these isostructural compounds. With iron as the apical metal center (M' = Fe) C(sp^2)−F bond oxygenation occurs almost exclusively, whereas with manganese (M' = Mn) the opposite reactivity is preferred

Reversible 1,2-Alkyl Migration to Carbene and Ammonia Activation in an N-Heterocyclic Carbene–Zirconium Complex

Addition of trimethylphosphine to a bis(phenolate)benzylimidazolylidene(dibenzyl)zirconium complex induces migration of a benzyl ligand from the metal center to the C_(carbine) atom. This process may be reversed, resulting in C_(sp)^3–C_(sp)^3 activation, by abstraction of the phosphine, an example of regulated, reversible alkyl migration. Addition of ammonia to the dibenzyl complex results in migration of one benzyl group and protonolysis of the other to generate a bis(NH_2)-bridged dimer via an NMR-observable intermediate NH_3 adduct

Tris{2-[(2,6-dimethyl­phen­yl)amino]­eth­yl}amine

The title compound, C30H42N4, is an aryl­ated tris­(amino­eth­yl)amine derivative which was obtained by reducing the corresponding tris-amide with AlH3. The asymmetric unit consists of one third of a C 3v-symmetric mol­ecule with the tertiary N atom lying on a crystallographic threefold axis

Synthesis of Substituted Dihydrobenzofurans via Tandem S_NAr/5-Exo-Trig Cyclization

A tandem S_NAr/5-exo-trig cyclization reaction is reported that converts N-alkyl- and -arylimines derived from o-fluorobenzaldehydes into 3-amino-2,3-dihydro-2,2-diarylbenzofurans in moderate to good yields. Diarylmethoxide coupling partners serve the dual role of nucleophile in the S_NAr step and catalytic base in the cyclization step. With a subset of the substrates, a further base-induced elimination of the 3-amino-2,3-dihydro-2,2-diarylbenzofuran to a phenolic enamine was observed

Total Synthesis and Characterization of 7-Hypoquinuclidonium Tetrafluoroborate and 7-Hypoquinuclidone BF_3 Complex

Derivatives of the fully twisted bicyclic amide 7-hypoquinuclidone are synthesized using a Schmidt–Aubé reaction. Their structures were unambiguously confirmed by X-ray diffraction analysis and extensive spectroscopic characterization. Furthermore, the stability and chemical reactivity of these anti-Bredt amides are investigated. 7-Hypoquinuclidonium tetrafluoroborate is shown to decompose to a unique nitrogen bound amide–BF_3 complex of 7-hypoquinuclidone under anhydrous conditions and to react instantaneously with water making it one of the most reactive amides known to date

Mechanistic Insights on the Controlled Switch from Oligomerization to Polymerization of 1-Hexene Catalyzed by an NHC-Zirconium Complex

The benzimidazolylidene zirconium complex 1 switches from an oligomerization (without additive) to a polymerization catalyst by addition of an L-type ligand such as trimethylphosphine, while larger phosphines or amines completely inhibit catalysis. On the basis of the regioselectivity of the oligomers/polymers obtained, the time profiles of reactions as a function of added ligand, and the molecular structures of several cationic zirconium complexes, we propose a mechanistic framework for interpreting this complex catalytic behavior

Examination of Acid-Fast Bacilli in Sputum Using Modified Light Microscope with Homemade Light Emitting Diode Additional Attachment

Typical clinical symptoms and chest X-ray is a marker of Tuberculosis (TB) sufferers. However, the diagnosis of TB in adults should be supported by microscopic examination. Currently, Bacilli microscopic examination of acid-fast bacilli (AFB) in sputum by Ziehl-Neelsen (ZN) coloring is the most widely used. However, for reasons of convenience, especially for laboratories with a considerable amount of smear samples, and due to higher sensitivity compared with ZN staining, the World Health Organization (WHO) has recommended the use of auramine-O-staining (fluorochrome  staining), which is visualized by light emitting diode (LED) fluorescence microscopy. The aim of this study was to evaluate the performance of modified light microscope with homemade LED additional attachment for examination of AFB in sputum using auramine-O-staining method. We compared the sensitivity and specificity of 2 kinds of AFB in sputum methods: ZN and fluorochrome, using culture on Lowenstein-Jensen media as the gold standard. The results showed auramine-O-staining gives more proportion of positive findings (81%) compared to the ZN method (70%). These results demonstrated that the sensitivity of auramine-O-staining was higher than ZN, however it gives more potential false positive results than ZN. The sensitivity of auramine-O-staining in detecting AFB in sputum was 100% while the specificity was 88%

Crystal structure and spectroscopic characterization of a cobalt(II) tetraazamacrocycle: completing a series of first-row transition-metal complexes

The tetraazamacrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetra-decane (TMC) has been used to bind a variety of first-row transition metals but to date the crystal structure of the cobalt(II) complex has been missing from this series. The missing cobalt complex chlorido(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane-κ^4N)cobalt(II) chloride dihydrate, [CoCl(C_(14)H_(32)N_4)]Cl·2H_2O or [Co^(II)Cl(TMC)]Cl·2H_2O, crystallizes as a purple crystal. This species adopts a distorted square-pyramidal geometry in which the TMC ligand assumes the trans-I configuration and the chloride ion binds in the syn-methyl pocket of the ligand. The Co^(II) ion adopts an S = 3/2 spin state, as measured by the Evans NMR method, and UV–visible spectroscopic studies indicate that the title hydrated salt is stable in solution. Density functional theory (DFT) studies reveal that the geometric parameters of [Co^(II)Cl(TMC)]Cl·2H_2O are sensitive to the cobalt spin state and correctly predict a change in spin state upon a minor perturbation to the ligand environment

Perubahan Struktural Dalam Pembangunan Perkotaan

Pertumbuhan daerah kota di negra berkembang menunjukan gejala yang tidak di harapkan.untuk mengantisipasi kondisi keterbelakangan ini, daerah perkotaan haurus di dorong secara kuat untuk meningkatkan permintaan terhadap barang dan pelayanan untuk seluruh kepentingan nasional. permasalahan kota yang telah di hadapi bukan hanya persoalan keruangan dan Perubahan struktur ekonomi saja, tapi juga pembentukan implikasi sosial dan lingkungan. hal ini dapat di lihat di Bogota dengan pola dualisme sistem sosialnya, adanya pemisahan ruang antara masyarakat kaya di daerah utara dan masyarakat miskin di daerah selatan dan barat. Fenomena serupa juga di temukan di Indonesia. Jakarta yang berkembang secara cepat dengan dukungan sektor manufaktur dan keuanga, mencapai kondisi ekonomi dan pendapatan yang baik. Bagaimanapun, di Balik kondisi tersebut, ditemukan biaya yang tak terhindarkan secara nyata, yang umum muncul berupa penurunan kualitas lingkungan. Beberapa kebijaksanaan direkomendasikan adalah: (1) Meningkatkan produktivitas ekonomi wilayah kota yang terintegrasi ke dalam pembangunan regional dan pedesaan, (2) Meningkatkan produktivitas kelompok miskin perkotaan melalui perbaikan infrastruktur sosial dan perluasan kesempatan kerja, (3) Menghindari Perusakan lingkungan serta konsekwensi lainnya di sekitar wilayah masyarakat miskin, dan (4) Membangun persepsi yang seimbang terhadap pembangunan kota dan permasalahan-permasalahan yang berkaitan dengannya: pemerintah, sektor swasta, dan masyarakat