Pyramidal Complexes Research Articles

Linking macroscale graph analytical organization to microscale neuroarchitectonics in the macaque connectome.

Macroscale connectivity of the mammalian brain has been shown to display several characteristics of an efficient communication network architecture. In parallel, at the microscopic scale, histological studies have extensively revealed large interregional variation in cortical neural architectonics. However, how these two "scales" of cerebrum organization are linked remains an open question. Collating and combining data across multiple studies on the cortical cytoarchitecture of the macaque cortex with information on macroscale anatomical wiring derived from tract tracing studies, this study focuses on examining the interplay between macroscale organization of the macaque connectome and microscale cortical neuronal architecture. Our findings show that both macroscale degree as well as the topological role in the overall network are related to the level of neuronal complexity of cortical regions at the microscale, showing (among several effects) a positive overall association between macroscale degree and metrics of microscale pyramidal complexity. Macroscale hub regions, together forming a densely interconnected "rich club," are noted to display a high level of neuronal complexity, findings supportive of a high level of integrative neuronal processes to occur in these regions. Together, we report on cross-scale observations that jointly suggest that a region's microscale neuronal architecture is tuned to its role in the global brain network.

Anion receptors containing coordinatively unsaturated metal ions: copper(II) complexes with cyclam derivatives

The two coordinatively unsaturated complexes [Cu(cyclam)]2+ (cyclam: 1,4,8,11-tetraazacyclotetradecane, 1) and [Cu(Bn4cyclam)]2+ (Bn4cyclam: 1,4,8,11-tetrabenzyl-1,4,8,11-tetraazacyclotetradecane, 2) in an MeCN solution uptake an anion X− (halide, pseudohalide) to give square pyramidal ternary complexes, whose stability has been determined through spectrophotometric titration experiments. The formation of a five-cordinate complex is favored by the trans-I configuration of the [Cu(Bn4cyclam)]2+ receptor, but it is contrasted by the severe steric repulsions exerted by the benzyl substituents on the macrocyclic framework. No significant repulsive effects have been observed in anion binding to the [Cu(cyclam)]2+ receptor, exhibiting a trans-III configuration. The existence of a linear relationship between the magnitude of the red shift experienced by the d−d absorption band on anion binding and log K values is discussed.

Behavior of the potential antitumor VIVO complexes formed by flavonoid ligands. 1. Coordination modes and geometry in solution and at the physiological pH

The coordination modes and geometry assumed in solution by the potent antitumor oxidovanadium(IV) complexes formed by different flavonoids were studied by spectroscopic (Electron Paramagnetic Resonance, EPR) and computational (Density Functional Theory, DFT) methods. A series of bidentate flavonoid ligands (L) with increasing structural complexity was examined, which can involve (CO, O−) donors and formation of five- and six-membered chelate rings, or (O−, O−) donors and five-membered chelate rings. The geometry corresponding to these coordination modes can be penta-coordinated, [VOL2], or cis-octahedral, cis-[VOL2(H2O)]. The results show that, at physiological pH, ligands provided with (CO, O−) donor set yield cis-octahedral species with “maltol-like” coordination when five-membered chelate rings are formed (as with 3-hydroxyflavone), while penta-coordinated structures with “acetylacetone-like” coordination are preferred when the chelate rings are six-membered (as with chrysin). When both the binding modes are possible, as with morin, the “acetylacetone-like” coordination is observed. For the ligands containing a catecholic donor set, such as 7,8-dihydroxyflavone, baicalein, fisetin, quercetin and rutin, the formation of square pyramidal complexes with (O−, O−) “catechol-like” coordination and five-membered chelate rings is preferred at physiological pH. The determination of the different coordination modes and geometry is important to define the biotransformation in the blood and the interaction of these complexes with the biological membranes.

Chain of dimers to assembly of trimers: temperature and ligand influenced formation of novel supramolecular assemblies of Cu(ii) with isomeric (aminomethyl) pyridines and azide

Five new complexes, viz., [Ni(2-aminomethylpyridine)2(N3)2] (1), [Cu(2-aminomethylpyridine)(N3)2]n (2), [Cu(2-aminomethylpyridine)2(N3)2] (3), [Cu3(3-aminomethylpyridine)2(N3)6]n (4) and [Zn(2-aminomethylpyridine)2(N3)2] (5), were synthesized and structurally characterized to probe the role of temperature as well as ligand geometry in the formation of novel supramolecular assemblies. The influential and preferential role of temperature as well as ligand geometry is observed in the supramolecular structure formation of Cu(II) complexes alone, with isomeric (aminomethyl)pyridines and azide. With 2-amp as the ligand, temperature greatly influences the product formation, resulting in thermodynamically stable 2 at RT and kinetically stable 3 at LTs. However, such a temperature influence is not evident with the analogous 3-amp derivative. Interestingly, the change in ligand geometry from 2-amp to 3-amp has resulted in drastic changes in the final supramolecular structure formation. The change in ligand geometry from chelating in 2-amp, to bridging in 3-amp leads to a 1-D polymeric chain of dimers bridged by asymmetric end-on azides in 2 to a 1-D assembly of trimers bridged by symmetric end-on azides in 4. The change in the ligand geometry appears to be responsible for the changes in the metal ion's geometrical preferences from square pyramidal in 2 to simultaneous octahedral and square planar in 4, assisted by a change in azide's bridging modes. Magnetic studies on both 2 and 4 revealed antiferromagnetic Cu–Cu interactions with J = −2.26 cm−1 (H = −JS1S2) and −7.5 cm−1 (H = −J(S1S2 + S2S3)) respectively. While the observed AFM interactions in 4 are in accordance with the theoretical predictions based on the crossover in the magnetic property from FM to AFM at α > 104°, in asymmetric end-on azide bridged dimers of transition metal complexes, the magnetic interactions in 2 are contrary to the predictions. The results once again emphasize that the predictions are valid only for the basal–basal mode of azide bridging, but not for basal–apical mode of bridging in square pyramidal complexes.

Dendritic Arborization and Spine Dynamics Are Abnormal in the Mouse Model ofMECP2Duplication Syndrome

MECP2 duplication syndrome is a childhood neurological disorder characterized by intellectual disability, autism, motor abnormalities, and epilepsy. The disorder is caused by duplications spanning the gene encoding methyl-CpG-binding protein-2 (MeCP2), a protein involved in the modulation of chromatin and gene expression. MeCP2 is thought to play a role in maintaining the structural integrity of neuronal circuits. Loss of MeCP2 function causes Rett syndrome and results in abnormal dendritic spine morphology and decreased pyramidal dendritic arbor complexity and spine density. The consequences of MeCP2 overexpression on dendritic pathophysiology remain unclear. We used in vivo two-photon microscopy to characterize layer 5 pyramidal neuron spine turnover and dendritic arborization as a function of age in transgenic mice expressing the human MECP2 gene at twice the normal levels of MeCP2 (Tg1; Collins et al., 2004). We found that spine density in terminal dendritic branches is initially higher in young Tg1 mice but falls below control levels after postnatal week 12, approximately correlating with the onset of behavioral symptoms. Spontaneous spine turnover rates remain high in older Tg1 animals compared with controls, reflecting the persistence of an immature state. Both spine gain and loss rates are higher, with a net bias in favor of spine elimination. Apical dendritic arbors in both simple- and complex-tufted layer 5 Tg1 pyramidal neurons have more branches of higher order, indicating that MeCP2 overexpression induces dendritic overgrowth. P70S6K was hyperphosphorylated in Tg1 somatosensory cortex, suggesting that elevated mTOR signaling may underlie the observed increase in spine turnover and dendritic growth.

Novel Dimerization of Maleic Anhydride at a Mo2 Complex: Phase-Driven Keto/Enol Tautomerism in a Phosphinidenium–Ylide Complex

A novel dimerization of maleic anhydride involving olefinic to carbonyl C–C coupling and an [1,7]-H shift is promoted by a strongly nucleophilic pyramidal phosphinidene complex. The resulting carbene is stabilized by coordination of the P atom of the phosphinidene ligand and undergoes keto/enol tautomerization when going from solution to the solid state. This is accompanied by a strong pyramidalization of the ylidic carbon atom, facilitated by the presence of π···π stacking interactions in the crystal lattice.

O1 * FREE ORAL COMMUNICATIONS 1: BASIC NEUROBIOLOGICAL MECHANISMS OF ALCOHOL ADDICTION

O1 * FREE ORAL COMMUNICATIONS 1: BASIC NEUROBIOLOGICAL MECHANISMS OF ALCOHOL ADDICTION

Derivation of ligand σ- and π-bonding parameters from density functional theoretical calculations and Bursten ligand additivity relationships

New ligand additivity equations, based on the Bursten model, describing dπ orbital energies in square-planar and square–pyramidal complexes are proposed and tested for hypothetical binary Cr(0) and Mn(I) complexes of CO and CNMe. Density functional theory calculations are used to calculate the energies of dπ orbitals of binary octahedral, square–planar, and square–pyramidal d6 complexes of Mn(I) and Cr(0). Combination of the modified equations for unsaturated species with Bursten’s original equations for octahedral species allows for calculation of individual ligand bonding parameters and the separation of σ- and π-bonding effects. The calculated parameters provide interesting insight into the nature of metal–ligand bonding in the species studied. The method of separating σ- and π-bonding effects, applied here to CO and CNMe, is proposed as general method for solution of the Bursten equations for low-spin d6 octahedral systems.

New Kingdom Graffiti in Dahshur, Pyramid Complex of Senwosret III: Preliminary Report. Graffiti Uncovered in Seasons 1992–2010

The Middle Kingdom (ca. 2010–1670 BCE) pyramid complex of Senwosret III at Dahshur contained a number of New Kingdom (ca. 1560–1080 BCE) hieratic inscriptions in its different structures. The texts proffer unique evidence for the study of the history of the pyramid complex, as well as of Egyptian literate culture, especially its relation to the uses of the past, and to sacred and ritual spaces. Relations between visual and written culture can also be observed with the help of graffiti that are placed in close contact with preceding decoration of the funerary complex. The preliminary report offers a summary of state of research, a description of hitherto uncovered graffiti corpus, and a perspective on interpretation of visitors’ graffiti in the pyramid complex of Senwosret III.

Complicated Electronic Process of C–C σ-Bond Activation of Cyclopropene by Ruthenium and Iridium Complexes: Theoretical Study

C–C σ-bond activation of cyclopropene by RuCl2(PPh3)2 and IrCl(CO)(PMe3)2 was theoretically investigated. The activation barrier and the reaction energy calculated here indicate that the reaction occurs more easily by the ruthenium complex than by the iridium complex, which is consistent with the experimental results that the Ru–vinylcarbene species is formed but the Ir–vinylcarbene is not. The valence bond analysis of the CASSCF wave function disclosed that the Ir–vinylcarbene bond is significantly weaker than that of the Ru complex because the d6 square pyramidal complex of Ru is more favorable than the d8 complex of Ir for this bonding interaction. In both the Ru and Ir systems, a precursor complex is formed by coordination of the C1═C2 double bond of cyclopropene with the metal center, where C1 and C2 are sp2 carbons and C3 is an sp3 carbon. In the transition state, one C–C single bond (named C1–C3) is almost broken, but the M–C1 bond (M = Ru or Ir) and another C–C single bond (named C2–C3) are becomi...

Miszelle. ′Inb(w) ḥḏ “White wall(s)”: A Town or White Limestone Cliffs?

Abstract The text on a Fifth Dynasty sealing found in the pyramid complex of Raneferef is a rare piece of historical evidence confirming the commonly accepted presumption that Ỉnb in Ptah’s epithet was merely an abbreviated form of ’Inb(w) ḥḏ and, at the same time, suggesting that the enclosure wall of ’Inb(w) ḥḏ was very probably decorated with the “Prunkscheintür”-pattern.

Ligand Effects on the Oxidative Addition of Halogens to (dpp-nacnacR)Rh(phdi)

The treatment of (dpp-nacnac(R))Rh(phdi) {(dpp-nacnac(R))(-) = CH[C(R)(N-(i)Pr2C6H3)]2(-); R = CH3, CF3; phdi = 9,10-phenanthrenediimine} with X2 oxidants afforded octahedral rhodium(III) products in the case of X = Cl and Br. The octahedral complexes exhibit well-behaved cyclic voltammograms in which a two-electron reduction is observed to regenerate the initial rhodium(I) complex. When treated with I2, (dpp-nacnac(CH3))Rh(phdi) produced a square pyramidal η(1)-I2 complex, which was characterized by NMR and UV-vis spectroscopies, mass spectrometry, and X-ray crystallography. The more electron poor complex (dpp-nacnac(CF3))Rh(phdi) reacted with I2 to give a mixture of two products that were identified by (1)H NMR spectroscopy as a square pyramidal η(1)-I2 complex and an octahedral diiodide complex. Reaction of the square pyramidal (dpp-nacnac(CH3))Rh(I2)(phdi) with HBF4 resulted in protonation of the (dpp-nacnac(CH3))(-) backbone to provide an octahedral rhodium(III) diiodide species. These reactions highlight the impact that changes in the electron-withdrawing nature of the supporting ligands can have on the reactivity at the metal center.

Co2+/Co+Redox Tuning in Methyltransferases Induced by a Conformational Change at the Axial Ligand

Density functional theory and quantum mechanics/molecular mechanics computations predict cob(I)alamin (Co(+)Cbx), a universal B(12) intermediate state, to be a pentacoordinated square pyramidal complex, which is different from the most widely accepted viewpoint of its tetracoordinated square planar geometry. The square pyramidality of Co(+)Cbx is inspired by the fact that a Co(+) ion, which has a dominant d(8) electronic configuration, forms a distinctive Co(+)--H interaction because of the availability of appropriately oriented filled d orbitals. This uniquely H-bonded Co(+)Cbx may have catalytic relevance in the context of thermodynamically uphill Co(2+)/Co(+) reduction that constitutes an essential component in a large variety of methyltransferases.

The Solution Chemistry of Cu2+–tren Complexes Revisited: Exploring the Role of Species That Are Not Trigonal Bipyramidal

AbstractPotentiometric and spectrophotometric titrations indicate that aqueous solutions that contain equimolar amounts of Cu2+ and tren contain the HCuL3+, CuL2+ and CuL(OH)+ species and that their relative concentrations depend on the pH of the solution. The stability constants and the UV/Vis and EPR spectra of the three species have been determined. The position of the absorption maximum clearly corresponds to a trigonal bipyramidal (tbp) geometry for CuL2+, whereas for HCuL3+ and CuL(OH)+ there are also bands that could correspond to square pyramidal (sp) complexes, but the EPR spectra indicate that only HCuL3+ can be considered to be sp. When any of these species is mixed with an excess of acid, an intermediate is formed within the mixing time of the stopped‐flow technique. This intermediate undergoes complete decomposition in a second slower step. Interestingly, the spectrum of this intermediate is typical of sp geometry. Kinetic studies on complex formation in general indicate that complexation occurs in a single step, although under certain conditions an additional step has been observed that probably corresponds to the conversion of CuL2+ to HCuL3+, and the spectral changes indicate that the process involves structural reorganization from tbp to sp geometry. DFT and TD‐DFT calculations have been carried out for the three stable species, as well as for species in a higher protonation state. The results indicate that CuL2+ exists as a species with tetradentate tren and tbp geometry, although a wide range of distortions between the ideal tbp geometry and a geometry closer to sp is possible with a very modest energy cost. The energy change associated with hydrolysis of one of the Cu–N bonds to give a species with tridentate tren was found to be slightly higher than that previously found for a related ligand, which contains a substituent at one of the terminal amino groups. For CuL(OH)+, the calculations suggest that an equilibrium exists between species with essentially the same energy but different geometries, each one of the species is closer to one of the ideal tbp and sp limits. For HCuL3+, the relevance of the sp geometry was confirmed by the calculations.

Copper(II) and Palladium(II) Complexes with Cytotoxic and Antibacterial Activity

The synthesis of eight square pyramidal copper complexes with general structure [Cu(IL)(AL)H2O]2+, where IL represents various methylated 1,10-phenanthrolines, and AL represents either 1S,2S- or 1R,2R-diaminocyclohexane, is reported, with the complexes synthesised as both the perchlorate and chloride salts. The crystal structures of [Cu(1,10-phenanthroline)(1S,2S-diaminocyclohexane](ClO4)2·H2O and [Cu(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane](ClO4)2·1.5H2O are reported. Four square planar palladium complexes with general structure [Pd(IL)(AL)]Cl2 have also been synthesised. These complexes were synthesised in order to investigate the structure–activity relationship against both cancer cell lines and bacterial cultures. The copper complexes display anticancer activity similar to cisplatin and 1,10-phenanthroline (phen) in the L1210 murine leukaemia cell line. Methylation of the phen increased the copper complex cytotoxicity by approximately four-fold, compared with the non-methylated complex. No significant difference in activity was observed by altering the chirality of the diaminocyclohexane ligand. The copper complexes demonstrated antibacterial activity against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli; however, high levels of toxicity (30–60 % of death) were observed in the nematode Caenorhabditis elegans. The copper complexes have also been shown to act as DNA nucleases, with the ability to cleave plasmid DNA in the presence of hydrogen peroxide. The palladium complexes all have half maximal inhibitory concentration (IC50) values of ~10 μM in the L1210 cell line, with no significant difference in the cytotoxicity of any of the compounds tested. Minimal antibacterial activity of the palladium complexes was observed.

The Snefru Projects and the Topography of Funerary Landscapes during the Twelfth Egyptian Dynasty

The topography of the pyramids of the twelfth dynasty is explored here in its full historical and chronological context, with the aim of highlighting connections between the architectural choices, religious ideas, and traditions inspiring the reigns of the Pharaohs of that period. There emerges a clear and close connection between the conceptual landscapes devised by the architects of these rulers, and the two “'double” building projects carried out more than six centuries before by Snefru at Dahshur and at Meidum-Seila. This connection encompasses geometry, perspective, and astronomical alignments in the progressive planning of the pyramidal complexes, and it is confirmed by an important text of the period, the tale entitled Prophecy of Neferti. In such a context, an attempt can be made to interpret several architectural and topographical choices that have remained so far unexplained. In particular, the funerary project of the last great king of the dynasty, Amenemhet III—who built two pyramids, one at Dahshur and the other at Hawara—appears to stem largely from symbolic, as opposed to practical, reasons.

Oxidoalkoxidovanadium(V) complexes: Synthesis, characterization and comparison of X-ray crystal structures

The reaction of VO(acac)2 with the ONO-chelator obtained by the condensation of salicylaldehyde with 2-hydroxybenzoylhydrazine (H2L) in a monohydric alcohol (ROH) medium produces [VO(OR)L]-type oxidoalkoxido complexes (1–7) where R=Me, nPr, iPr, nBu, iBu, tBu and nPen. All the complexes show the metal atom to have a five-coordinate square pyramidal environment, although in some complexes there is an additional weak V⋯O interaction in the sixth axial position. In acetonitrile medium and in the presence of a cis-diol (ethylene glycol), H2L reacts with VO(acac)2 to form a six-coordinate complex, [VO(OCH2CH2OH)L] (8). When the reaction is carried out in acetonitrile medium in the presence of 2-amino ethanol, a completely different type of product containing the square pyramidal complex anion [VO2L]− associated with the cation [NH3CH2CH2OH]+ is obtained. It was noted previously that on being reacted with monodentate nitrogen donor bases B (which are stronger than pyridine), the [VO(OR)L] complexes react to form the same complex anion [VO2L]− associated with the corresponding cation [BH]+. The coordination environment around the V(V) acceptor center of the water soluble [BH]+[VO2L]− satisfies one of the several requirements for an efficient antidiabetic vanadium species such as water solubility, nature of donor atoms of the ligand and their disposition around the VO2+ acceptor center.

Structure of BaTiO3 phases is studied by comparing neutron diffraction and Raman spectroscopy data

Considering the structural unit of the rhombohedral BaTiO3 phase in the form of Ti(-O...Ti)6 which was constructed by neutron diffraction data, we revealed an atomic group in the form of a pyramidal complex anion TiO32−. Inspection of the Raman spectra of this phase showed symmetry group Cs for this complex anion. From the similarity of the Raman spectra of all ferroelectric BaTiO3 phases, we inferred that the orthorhombic phase and tetragonal phase are also built of TiO32− complex anions. In the paraelectric cubic phase, TiO32− complex anions decompose to oxygen ions O2− and Ti2+(O−)2 molecules, which are randomly oriented over 12 possible positions. Average Ti-O distances derived from neutron diffraction data were used to calculate Ti-O− and Ti=O bond lengths in TiO32− complex anions of the ferroelectric BaTiO3 phases. Two types of Ti-O...Ti bridges were found to exist; they belong to weak and strong intermolecular bonds, which are similar to weak and strong hydrogen bonds (H-bonds) in ferroelectrics. Weak bonds exist in all of the three ferroelectric phases; strong bonds are only in the orthorhombic phase and the tetragonal phase. As a result of a low potential barrier height in strong bonds, an oxygen atom persistently hops from one potential well to an adjacent one, which is responsible for bands appearing below 100 cm−1 in the Raman spectra of the tetragonal phase and orthorhombic phase. The data obtained on the structure of the ferroelectric BaTiO3 phases were used to interpret their spontaneous polarization, repolarization, and permittivity.

DFT investigation of endohedral boron oxide nanocapsules: Encapsulation of He, Ne, Ar, H, N, and Cl atoms

The electronic structure and stabilization energy of spherical and pyramidal shapes of boron oxide nanocapsules (X@B 20O 30, X = He, Ne, Ar, H, N, Cl) were investigated by long-range and dispersion corrected density functional theory (DFT + Disp) including CAM-B3LYP, B3LYP-D3, ωB97X-D and B2PLYP-D methods. Based on these calculations, the formation of nanocapsules is an exothermic process (except for Cl@B 20O 30). The spherical boron oxide nanocapsules are mainly stabilized by dispersion, while the stability of pyramidal complexes is mainly due to monomer relaxation energy. The theoretical results obtained in this work show that the boron oxide capsule is a good potential candidate for gas storage.

Antimicrobial and antioxidant activities of new metal complexes derived from (E)-3-((5-phenyl-1,3,4-oxadiazol-2-ylimino)methyl)naphthalen-2-ol

(E)-3-((5-phenyl-1,3,4-oxadiazol-2-ylimino)methyl)naphthalen-2-ol (LH) has been synthesized and used as a ligand for the formation of V(IV), Cr(III), Mn(II), Co(II), Ni(II), and Cu(II) complexes. The chemical structures were characterized using different spectroscopic methods. The elemental analyses revealed that the complexes have the general formula [ML2(H2O)2] [where M = Mn(II), Co(II), and Cu(II)], while the Cr(III) complex has the formula [CrL2(H2O)2]Cl, V(IV) complex has the formula [VO2L2], and Ni(II) complex has the formula [NiL2]. The molar conductance data revealed that all the metal chelates except the Cr(III) are non-electrolytes. From the magnetic susceptibility measurement and UV–Visible spectra, it is found that the structures of Cr(III), Mn(II), Co(II), and Cu(II) complexes are octahedral, V(IV), complex is square pyramid and Ni(II) complex is square planar. The stability of the prepared complexes was studied theoretically using density function theory. The total energy for the complexes was calculated and it was shown that the copper complex is the most stable. Complexes were tested against selected types of microbial organisms and showed significant activities. The free radical scavenging activity of metal complexes have been determined by their interaction with the stable DPPH-free radicals. All the compounds have shown encouraging antioxidant activities.