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Hydrogen bonding versus coordination of adsorbate molecules on Ti-silicalites: a density functional theory study.

The present study discusses the results of theoretical calculations obtained at the B3LYP/ 6-31G level on the structural, electronic, and energetic properties of Ti-silicalites. Particularly, the relevance of 5T cluster models, either H- or OH-terminated, in large-scale calculations has been critically considered. It was shown that an open surface structure with one OH group and a closed-bulk structure with no bonded OH group at the Ti site are responsible for the observed UV-vis properties of Ti-silicalite materials. Both water and methanol can preferably interact with Ti-silicalites through the H-bonding mechanism, while ammonia can form either H-bonded or coordination complexes. The calculations support the existence of highly dispersed Ti sites in a tetrahedral environment only in Ti-silicalites because an increase in the coordination number of the Ti site by next-neighbor lattice oxygens is the energetically less favorable process.

Journal Article↗

The training of coordination.

The training of coordination is generally considered a volitional activity, during which, by trial and perception of results, an individual selects the muscular activity resulting in the desired performance. This concept of volitionally directed complex coordination of multiple muscles with speed, skill, and strength does not stand the test of thorough evaluation. Attention is limited to 1 activity at a time, with the ability to shift attention not more frequently than 3 times per second. Only under special conditions can activity be limited to specific muscles during an untrained contraction without cocontraction of other muscles. However, with repeated practice of the desired activity, a pattern of performance is developed which can be carried out rapidly and forcefully without activation of other muscles. At that time, the consciousness is no longer directing the components of the activity but merely starting, maintaining, and stopping the performance. The development of these patterns, or engrams, by practice develops the capacity to automatically inhibit muscles that do not contribute to the performance of the desired pattern. The capacity for inhibition results in coordinated activation of the muscles contributing to the performance desired. Investigation of the development of coordination in many types of normal activities, as well as in neuromuscularly impaired patients, shows that engrams develop progressively by slow, precise practice of simple patterns, combined as they develop into more and more complex patterns, until the final skill is attained.

Attention↗

Cubane-type Mo3CoS4 molecular clusters with three different metal electron populations: structure, reactivity and their use in the synthesis of hybrid charge-transfer salts.

Heterodimetallic cubane-type complexes coordinated to diphosphanes [Mo(3)CoS(4)(dmpe)(3)Cl(4)](+) ([1](+)) (dmpe=1,2-bis(dimethylphosphanyl)ethane), [Mo(3)CoS(4)(dmpe)(3)Cl(4)] (1) and [Mo(3)CoS(4)(dmpe)(3)Cl(3)(CO)] (2) with 14, 15 and 16 metal electrons, respectively, have been prepared from the [Mo(3)S(4)(dmpe)(3)Cl(3)](+) trinuclear precursor using [Co(2)(CO)(8)] or CoCl(2) as cobalt source. Cluster complexes [1](+) and 1 are easily interconverted chemically and electrochemically. The Co-Cl distance increases upon electron addition and substitution of the chlorine atom coordinated to cobalt with CO only takes place in presence of a reducing agent to give complex 2. Structural changes in the intermetallic distances agree with the entering electrons occupying an orbital which is basically Mo-Mo non-bonding and slightly Mo-Co bonding. Magnetic susceptibility measurements for [1](+) and 1 are consistent with the presence of two and one unpaired electrons, respectively and therefore with an "e" character for the HOMO orbital. Oxidation of 1 with TCNQ results in the formation of a charge transfer salt formulated as [1](+)[TCNQ](-) with alternate layers of paramagnetic cluster cations and also paramagnetic organic anions. There is no magnetic interaction between layers and the thermal variation of the magnetic susceptibility has been modelled as a S= 1/2 TCNQ antiferromagnetic chain plus a S=1 cluster monomer with zero field splitting.

Journal Article↗

Cu, Pt, and Pd complexes of the 3-deoxy-1,2-bis(thiosemicarbazone) derived from D-glucose.

3-Deoxy-D-erythro-hexos-2-ulose bis(thiosemicarbazone) (1) acts as a tetradentate ligand of the N2S2 type which forms stable coordination complexes with metal(II) cations. The Cu(II), Pt(II), and Pd(II) chelates (2, 4, and 6, respectively) of 1 were synthesized and characterized by elemental analysis and NMR spectroscopy. The NMR spectra of the Pt complex (4) showed the coupling of H-1 and C-1, C-2 of the bis(thiosemicarbazone) with 195Pt (33.7% naturally occurring), which supports the structure proposed for the chelate. The complexes 2, 4, and 6 were acetylated to give the corresponding tri-O-acetyl derivatives 3, 5, and 7. Elimination of Cu(II) from 3 with hydrogen sulfide afforded 8, the tri-O-acetyl derivative of 1. Preliminary studies have shown antiviral activity of chelates 2, 4, and 6 against poliovirus type 1.

Animals↗

Reactions of [(eta(6)-arene)RuCl(2)](2) with Aromatic Phosphines Containing Methoxy Groups in 2,6-Positions.

Reactions of [(eta(6)-arene)RuCl(2)](2) 1 (arene = p-cymene (a), 1,2,3,4-Me(4)C(6)H(2) (b), 1,2,3-Me(3)C(6)H(2) (c)) with tris(2,6-dimethoxyphenyl)phosphine (TDMPP) led to loss of two molecules of CH(3)Cl to give (eta(6)-arene)Ru[{2-O-C(6)H(3)-6-OMe}(2){C(6)H(3)(OMe)(2)-2,6}], 2a-c, which contains a trihapto ligand (eta(3)-P,O,O) derived from TDMPP, whereas the 1,3,5-Me(3)C(6)H(3) (1d), 1,2,3,5-Me(4)C(6)H(2) (1e), and C(6)Me(6) (1f) complexes did not react with TDMPP. The structures of 2a and 2b were confirmed by X-ray analyses: for 2a, a = 11.691(2) Å, b = 15.228(2) Å, c = 10.320(1) Å, alpha = 95.93(1) degrees, beta = 113.783(9) degrees, gamma = 83.86(1) degrees, triclinic, P&onemacr;, Z = 2, R = 0.051; for 2b, a = 17.79(2) Å, b = 15.43(1) Å, c = 20.93(1) Å, beta = 91.25(8) degrees, monoclinic, P2(1)/n, Z = 8, R = 0.056. Bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP) reacted with 1a, 1b, and 1d at room temperature to give (eta(6)-arene)RuCl[PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}], 3a,b,d, which contains a dihapto (eta(2)-P,O) ligand derived from BDMPP by an X-ray analysis of 3a: a = 12.33(1) Å, b = 14.246(8) Å, c = 11.236(9) Å, alpha = 91.47(8) degrees, beta = 117.28(6) degrees, gamma = 111.70(6) degrees, triclinic, P&onemacr;, Z = 2, R = 0.040. A similar reaction with 1f recovered the starting materials, but that in refluxing MeCN produced [(eta(6)-C(6)Me(6))Ru[PPh(2-O-C(6)H(3)-6-OMe}(2)], 4f, containing a trihapto (eta(3)-P,O,O) ligand derived from BDMPP. Complex 1d reacted with BDMPP at reflux in MeCN/CH(2)Cl(2) and resulted in a loss of an arene ring to give a five-coordinate complex, Ru[eta(2)-P,O-PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}](2)(MeCN), 5. Treatment of (2,6-dimethoxyphenyl)diphenylphosphine (MDMPP) with 1f gave (eta(6)-C(6)Me(6))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe)],6f, and that with 1b gave (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe}], 6b, and (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl(2)[eta(1)-P-PPh(2){C(6)H(3)(OMe)(2)-2,6}],7b. The phosphine ligand of 6b acted as a bidentate ligand derived from MDMPP: a = 8.074(4) Å, b = 16.816(3) Å, c = 18.916(4) Å, beta = 94.05(3) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.051. Transformation of 7b to 6b readily occurred accompanying an elimination of MeCl. Reaction of 1a with MDMPP eliminated an arene ring to give the octahedral compound RuCl(2)[eta(2)-P,OMe-PPh(2){C(6)H(3)(MeO)(2)-2,6}](2), 8. An X-ray analysis of 8 showed that two MDMPP ligands were in a cis-position: a = 10.596(14) Å, b = 27.586(12) Å, c = 13.036(8) Å, beta = 108.17(7) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.035.

Journal Article↗

The first phosphite complex of a metalloporphyrin.

(Diphenyl phosphite-kappaO)(5,10,15,20-tetraphenylporphyrinato-kappa(4)N)manganese(III) hexafluoroantimonate(V), [Mn(C(44)H(28)N(4))(C(12)H(11)O(3)P)](SbF(6)), is the first example of a structurally characterized diaryl or dialkyl phosphite complex of a metal-porphyrin ion. The axial phosphite ligand binds to the Mn(III) ion via the P=O O atom, affording a nominally five-coordinate complex with an Mn-O distance of 2.120 (4) A. The mean porphyrin Mn-N distance is 2.000 (4) A and the Mn(III) ion is displaced from the 24-atom porphyrin mean plane by 0.1548 (13) A towards the axial O atom. The porphyrin adopts a marked saddle conformation, with a small domed component. The saddle distortion of the porphyrin ligand reflects the tight back-to-back dimers formed in the lattice by pairs of neighboring cations. The 'non-covalent' dimers in the lattice exhibit an unusual (weak) eta(2)-type coordination of a pyrrole C=C bond from a neighboring molecule, with Mn(III).C distances of 3.697 (5) and 3.537 (5) A.

Journal Article↗

Zirconium and hafnium complexes containing bidentate diarylamido-phosphine ligands.

The first examples of mononuclear, structurally characterized triarylphosphine complexes of zirconium and hafnium are reported. The metathetical reactions of MCl4(THF)2 (M = Zr, Hf) with [iPrNP]Li(THF)2 ([iPrNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-diisopropylanilide) or [MeNP]Li(THF)2 ([MeNP]- = N-(2-(diphenylphosphino)phenyl)-2,6-dimethylanilide) in toluene at -35 degrees C produced the corresponding [iPrNP]MCl3(THF) and [MeNP]2MCl2, respectively, in high yield. In contrast, attempts to prepare [MeNP]MCl3(THF) and [iPrNP]2MCl2 led to the concomitant formation of mono- and bis-ligated complexes, from which purification proved rather ineffective. The solution and solid-state structures of [iPrNP]MCl3(THF) and [MeNP]2MCl2 were studied by multinuclear NMR spectroscopy and X-ray crystallography. The geometry of these six-coordinate complexes is best described as a distorted octahedron in which the chloride ligands in [iPrNP]MCl3(THF) adopt a virtually meridional coordination mode whereas those in [MeNP]2MCl2 are trans to each other.

Journal Article↗

How can the principles of complexity science be applied to improve the coordination of care for complex pediatric patients?

Clinical and technological advances in medicine have resulted in more patients requiring multidisciplinary care and coordination of services. This is particularly challenging in pediatrics, given the dependency of children. Coordination of care is a key ingredient of quality care; when suboptimal, clinical outcomes and satisfaction can suffer. In this article we view coordination of care through the lens of complexity science in an effort to find new solutions to this healthcare challenge.

Child↗

Anticancer cytotoxicity and nephrotoxicity of the new platinum (II) complexes containing diaminocyclohexane and glycolic acid.

Cisplatin is an important antineoplastic agent, but dose-limiting nephrotoxicity prevents potential efficacy. There is interest in developing new platinum agents that have less toxicity. We have synthesized novel platinum (II) coordination complexes containing diaminocyclohexane as carrier ligands, and glycolic acid as a leaving group. In this study, new platinum (II) complex compounds were evaluated for cytotoxicity on cancer cell lines and nephrotoxicity. The new platinum complexes have demonstrated high efficacy in the cytotoxicity against human ovarian adenocarcinoma cell lines (SKOV-3/NIH.OVCAR-3) and human prostate carcinoma cell lines (DU-145/PC-3). The cytotoxicity of these compounds against rabbit proximal renal tubular cells and human renal cortical tissues was determined by MTT assay, the [3H]-thymidine uptake and glucose consumption test, and found to be considerably less than those of cisplatin. Based on our results, these novel platinum compounds appear to be valuable lead compounds with high efficacy and low nephrotoxicity.

Animals↗

High-performance fluorescent particles prepared via miniemulsion polymerization.

Highly fluorescent polymer particles were prepared with Eu beta-diketonates complex as a fluorophore by miniemulsion polymerization technique. Eu beta-diketonates complex has a long decay time, a large Stokes shift, and very narrow emission bands in comparison with other organic fluorescent compounds. Aqueous miniemulsion was prepared by mixing monomer, crosslinker, hydrophobe, and Eu beta-diketonates complex and then putting the mixture into an aqueous solution of surfactant, followed by ultrasonication. An aqueous solution of initiator was added to the miniemulsion to obtain fluorescent polymer particles, which were monodispersed without aggregation. Particle size was decreased to deca-nano scale by increasing the amount of surfactant. Fluorescent intensity was increased by using Eu beta-complex coordinated with additional ligand. Further fluorescence quantum yields and fluorescent properties in the presence of DNA were investigated to the confirm superiority of Eu beta-diketonates complexes in polymer particles.

Base Sequence↗

[Effect of aniline and hydrazine derivatives on reversible oxygen addition in model systems of cobalt complexes of etioporphyrin and alpha, beta, gamma, delta-tetraphenylporphine].

The influence of aniline and hydrazine derivatives on the reversible oxygenation of cobaltous complexes of etioporphyrin I and alpha,beta,gamma,delta-tetraphenylporphin has been studied by means of ESR and electronic spectra. The formation of stable six-coordinated complexes with the said reagents prevents the oxygenation. The excess of hydrazines cause the destruction of porphyrin nucleus. The formation of intermediate dihydroporphyrins (chlorins) has been noticed.

Aniline Compounds↗

Synthesis and biological activity of five-coordinate platinum(II) complexes including organotin fragments.

The synthesis and characterization of two five-coordinate platinum(II) complexes of general formula [PtCl(SnMe(n)Cl3-n)(2,9-Me2-1,10-phenanthroline) (diethylfumarate)] (n = 1, 2) are described. The bimetallic species were tested on the neuroblastoma cell line SK-N-BE and a considerable inhibition of cellular proliferation was detected; the bimetallic species were also able to induce neuronal differentiation, as did retinoic acid, a well-known neuroblastoma differentiating agent.

Cell Differentiation↗

Copper(II) complexes of a series of alkoxy diazine ligands: mononuclear, dinuclear, and tetranuclear examples with structural, magnetic, and DFT studies.

Picolyl hydrazide ligands have two potentially bridging functional groups (micro-O, micro-N-N) and consequently can exist in different coordination conformers, both of which form spin-coupled polynuclear coordination complexes, with quite different magnetic properties. The complex [Cu(2)(POAP-H)Br(3)(H(2)O)] (1) involves a micro-N-N bridge (Cu-N-N-Cu 150.6 degrees ) and exhibits quite strong antiferromagnetic coupling (-2J = 246(1) cm(-)(1)). [Cu(2)(PZOAPZ-H)Br(3)(H(2)O)(2)] (2) has two Cu(II) centers bridged by an alkoxide group with a very large Cu-O-Cu angle of 141.7 degrees but unexpectedly exhibits quite weak antiferromagnetic exchange (-2J = 91.5 cm(-)(1)). This is much weaker than anticipated, despite direct overlap of the copper magnetic orbitals. Density functional calculations have been carried out on compound 2, yielding a similar singlet-triplet splitting energy. Structural details are reported for [Cu(2)(POAP-H)Br(3)(H(2)O)] (1), [Cu(2)(PZOAPZ-H)Br(3)(H(2)O)(2)] (2), [Cu(2)(PAOPF-2H)Br(2)(DMSO)(H(2)O)].H(2)O (3), [Cu(4)(POMP-H))(4)](NO(3))(4).2H(2)O (4), and PPOCCO (5) (a picolyl hydrazide ligand with a terminal oxime group) and its mononuclear complexes [Cu(PPOCCO-H)(NO(3))] (6) and [Cu(PPOCCO-H)Cl] (7). Compound 1 (C(12)H(13)Br(3)Cu(2)N(5)O(4)) crystallizes in the monoclinic system, space group P2(1)/c, with a = 15.1465(3) A, b = 18.1848(12) A, c = 6.8557(5) A, beta = 92.751(4) degrees, and Z = 4. Compound 2 (C(10)H(13)Br(3)Cu(2)N(7)O(4)) crystallizes in the triclinic system, space group P, with a = 9.14130(1) A, b = 10.4723(1) A, c = 10.9411(1) A, alpha = 100.769(1), beta = 106.271(1) degrees, gamma = 103.447(1) degrees, and Z = 2. Compound 3 (C(23)H(22)Br(2)Cu(2)N(7)O(5.5)S) crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.406(2) A, b = 22.157(3) A, c = 10.704(2) A, beta = 106.21(1) degrees, and Z = 4. Compound 4(C(52)H(48)Cu(4)N(20)O(18)) crystallizes in the monoclinic system, space group P2(1)/n, with a = 14.4439(6) A, b = 12.8079(5) A, c = 16.4240(7) A, beta = 105.199(1) degrees, and Z = 4. Compound 5 (C(15)H(14)N(4)O(2)) crystallizes in the orthorhombic system, space group Pna2(1), with a = 7.834(3) A, b = 11.797(4) A, c = 15.281(3) A, and Z = 4. Compound 6(C(15)H(13)CuN(5)O(5)) crystallizes in the monoclinic system, space group P2(1)/c, with a = 8.2818(9) A, b = 17.886(2) A, c = 10.828(1) A, beta = 92.734(2) degrees, and Z = 4. Compound 7 (C(15)H(13)CuClN(4)O(2)) crystallizes in the orthorhombic system, space group Pna2(1), with a = 7.9487(6) A, b = 14.3336(10) A, c = 13.0014(9) A, and Z = 4. Density functional calculations on PPOCCO are examined in relation to the anti-eclipsed conformational change that occurs on coordination to copper(II).

Journal Article↗

Studies of low-coordinate iron dinitrogen complexes.

Understanding the interaction of N2 with iron is relevant to the iron catalyst used in the Haber process and to possible roles of the FeMoco active site of nitrogenase. The work reported here uses synthetic compounds to evaluate the extent of NN weakening in low-coordinate iron complexes with an FeNNFe core. The steric effects, oxidation level, presence of alkali metals, and coordination number of the iron atoms are varied, to gain insight into the factors that weaken the NN bond. Diiron complexes with a bridging N2 ligand, L(R)FeNNFeL(R) (L(R) = beta-diketiminate; R = Me, tBu), result from reduction of [L(R)FeCl]n under a dinitrogen atmosphere, and an iron(I) precursor of an N2 complex can be observed. X-ray crystallographic and resonance Raman data for L(R)FeNNFeL(R) show a reduction in the N-N bond order, and calculations (density functional and multireference) indicate that the bond weakening arises from cooperative back-bonding into the N2 pi orbitals. Increasing the coordination number of iron from three to four through binding of pyridines gives compounds with comparable N-N weakening, and both are substantially weakened relative to five-coordinate iron-N2 complexes, even those with a lower oxidation state. Treatment of L(R)FeNNFeL(R) with KC8 gives K2L(R)FeNNFeL(R), and calculations indicate that reduction of the iron and alkali metal coordination cooperatively weaken the N-N bond. The complexes L(R)FeNNFeL(R) react as iron(I) fragments, losing N2 to yield iron(I) phosphine, CO, and benzene complexes. They also reduce ketones and aldehydes to give the products of pinacol coupling. The K2L(R)FeNNFeL(R) compounds can be alkylated at iron, with loss of N2.

Crystallography, X-Ray↗

Electronically unsaturated three-coordinate chloride and methyl complexes of iron, cobalt, and nickel.

Three-coordinate organometallic complexes are rare, especially with the prototypical methyl ligand. Using a hindered, rigid bidentate ligand (L), it is possible to create 12-electron methyliron(II) and 13-electron methylcobalt(II) complexes. These complexes are thermally stable, and (1)H NMR spectra suggest that the low coordination number is maintained in solution. Attempts to create the 14-electron LNiCH(3) led instead to the three-coordinate nickel(I) complex LNi(THF). Single crystals of LMCH(3) are isomorphous with the new three-coordinate chloride complexes LNiCl and LCoCl. Along with the recently reported LFeCl (Smith, J. M.; Lachicotte, R. J.; Holland, P. L. Chem. Commun. 2001, 1542), these are the only examples of three-coordinate iron(II), cobalt(II), and nickel(II) complexes with terminal chloride ligands, enabling the systematic evaluation of the effect of coordination number and metal identity on M-Cl bond lengths. Electronic structure calculations predict the ground states of the trigonal complexes.

Journal Article↗

Synthesis and X-ray crystal structure determination of the first Copper(II) complexes of tetraazamacrocycle-glyoxal condensates.

Novel Cu(II) complexes CuLCl(2) (L = 1-4) have been synthesized containing the metal bound to a well-known type of tetracyclic bisaminal formed from the condensation of glyoxal and tetraazamacrocycles (1 = cyclam-glyoxal condensate, 2 = [13]aneN4-glyoxal condensate, 3 = cyclen-glyoxal condensate, 4 = isocyclam-glyoxal condensate). The four-coordinate complexes were characterized by X-ray crystallography, electronic spectroscopy, solid-state magnetic moments, and electron spin resonance spectroscopy. The tetracyclic bisaminals, although having four potential donor atoms, are bound in a cis-bidentate fashion to Cu(II) with two additional cis-chloride donors. The ligands take up folded conformations, and with the exception of ligand 4, only nonadjacent nitrogen atoms coordinate. As expected, ligand 2 in Cu(2)Cl(2) has a folded structure similar to those of the previously characterized 1 and 3. The conformation of 4 in the complex Cu(4)Cl(2) differs from 1-3 in that three nitrogens direct their lone pairs to one side of the folded tetracycle, with adjacent nitrogen atoms coordinated to Cu(II). This difference is probably caused by the presence of the more flexible seven-membered ring rather than the five- to six-membered rings in 1-3. Air oxidation of Cu(I) in the presence of 1 or 3 results in bis(mu-hydroxo) dimers as characterized by X-ray crystal structures, suggesting dioxygen binding, followed by O-O bond splitting to give the Cu(2)O(2) diamond core.

Journal Article↗

Deletion mutagenesis in Synechocystis sp. PCC6803 indicates that the Mn-stabilizing protein of photosystem II is not essential for O2 evolution.

The photosystem II (PSII) reaction center complex coordinates a cluster of Mn atoms that are involved in the accumulation of oxidizing equivalents generated by light-induced charge separations within the intrinsic portion of the PSII complex. A 33-kDa extrinsic protein, termed the Mn-stabilizing protein (MSP), has been implicated in the stabilization of two of the four Mn atoms of the cluster, yet the precise role of this protein in O2 evolution remains to be elucidated. Here we describe the construction of a mutant of the cyanobacterium Synechocystis sp. PCC6803 in which the entire gene encoding MSP has been deleted. Northern and immunoblot analyses indicate that other PSII proteins are expressed and accumulated, despite the absence of MSP. Fluorescence emission spectra at 77 K indicate PSII assembles in the mutant, but that the binding of MSP is required for the normal fluorescence characteristics of the PSII complex, and suggest a specific interaction between MSP and CP47. Fluorescence induction measurements indicate a reduced rate of forward electron transport to the primary electron donor, P680, in the mutant. It is concluded that in contrast to previous reports, MSP is not required for the assembly of active PSII complexes nor is it essential for H2O-splitting activity in vivo.

Blotting, Northern↗