1,721,389 research outputs found
Celebrating the 100th Anniversary of the Nobel Prize in Chemistry awarded to Alfred Werner
No full textHalf a grid is better than no grid : competition between 2,2':6',2"-terpyridine and 3,6-di(pyrid-2-yl)pyridazine for copper(II)
No full textThe reaction between Cu(NO3)2·3H2O, 2,2′:6′,2′′-terpyridine (tpy) and 3,6-di(pyrid-2-yl)pyridazine (1) in a 2 : 2 : 1 molar equivalent ratio in aqueous MeCN in the presence of excess NH4PF6 leads to competition between the assembly of the dinuclear half-grid [Cu2(1)(tpy)2][PF6]4·2H2O and the mononuclear complex [Cu(1)2(OH2)][PF6]2. The yield of [Cu2(1)(tpy)2][PF6]4·2H2O has been optimized using microwave conditions. [Cu(1)2(OH2)][PF6]2 can be selectively produced by treating Cu(NO3)2·3H2O with 1 (1 : 2 molar equivalents) in aqueous MeCN in the presence of NH4PF6. The single crystal structures of [Cu2(1)(tpy)2][PF6]4·4MeNO2 and [Cu(1)2(OH2)][PF6]2 are presented. In the [Cu2(1)(tpy)2]4+ cation, ligand 1 bridges the two copper(II) centres, each of which is further coordinated by a tpy ligand. The copper(II) coordination geometry is closely associated with the arrangement of the two tpy ligands which engage in efficient face-to-face π-stacking. Magnetic data for crystalline [Cu2(1)(tpy)2][PF6]4·4MeNO2 are consistent with a weak antiferromagnetic interaction between the two copper(II) centres. EPR spectroscopic data for a powder sample of [Cu2(1)(tpy)2][PF6]4·2H2O are consistent with the dinuclear structure, but in frozen DMF and DMSO solutions, the data indicate that the dinuclear structure of [Cu2(1)(tpy)2]4+ is not preserved
Homoleptic metal complexes of 4'-(5-pyrimidinyl)-2,2':6',2''-terpyridine : tetrafurcated expanded ligands
No full textWith iron(II) and ruthenium(II), 4`-(5-pyrimidinyl)-2,2`: 6`,2 ``-terpyridine (L) preferentially coordinates through the tpy domain to give octahedral [ML2](2+) (M Fe, Ru) complexes. Treatment of [RuL2][PF6](2) with CuCl2 center dot 2H(2)O leads to [Ru(2)(2)][CuCl2(OH2)][CuCl3]Cl center dot 3MeCN center dot 7H(2)O(n) which exhibits a two-dimensional coordination network with copper(II) centres interconnecting [RuL2](2+) motifs. Magnetic susceptibility data for the material are consistent with a one-dimensional S = 1/2 antiferromagnetic chain
Structural diversity in the reactions of 4 '-(pyridyl)-2,2 ':6 ',2 ''-terpyridine ligands and bis{4 '-(4-pyridyl)-2,2 ':6 ',2 ''-terpyridine}iron(II) with copper(II) salts
No full textWe have demonstrated that treatment of [Fe(1)(2)](2+) (1 = 4'-(4-pyridyl)-2,2':6',2 ''-terpyridine) with an excess of CuCl2 center dot 2H(2)O leads to competition between coordination of copper(II) by the pendant pyridine donors in [Fe(1)(2)](2+), and transfer of ligand 1 from iron(II) to copper(II) to yield [{Cl3Cu(mu-1)Fe(mu-1)}(2)CuCl2(OH2)(2)]Cl-2 center dot 4H(2)O and [Cu(H1)Cl-2]Cl center dot 4H(2)O, respectively. Direct reaction of 1 with CuCl2 center dot 2H(2)O and variation in crystallization conditions results in the formation of either monomeric or polymeric complexes: [Cu(1)Cl-2]center dot 4.75H(2)O, [Cu(1)Cl-2]center dot H2O center dot MeOH and [Cu(1)Cl-2 center dot 2H(2)O](n). The reaction of 1 with Cu(NO3)(2)center dot 3H(2)O gives the coordination polymer [Cu(1)(ONO2)(2)center dot H2O](n). Magnetic data for [Cu(1)Cl-2 center dot 2H(2)O](n) and [Cu(1)(ONO2)(2)center dot H2O](n) are consistent with antiferromagnetically- coupled chains. Reactions of CuCl2 center dot 2H(2)O with ligands 2 and 3 (2 = 4'-(3-pyridyl)-2,2':6',2 ''-terpyridine, 3 = 4'-(2-pyridyl)-2,2':6',2 ''-terpyridine) lead to monomeric complexes. With the exception of [Cu(3)Cl-2], the mononuclear complexes show a propensity for the incorporation of water into their crystal lattices; in the case of [Cu(H1)Cl-2]Cl center dot 4H(2)O and [Cu(H1)Cl-2]Cl center dot 4.75H(2)O, the small change in water content leads to the assembly of (5.8(2))(2)(5.6.8)(4)(5(2).6)(2) or (4(2).6(2))(3)(4.6(2))(6) water-chloride ion nets
Preparation and photophysical studies of copper(I) and ruthenium(II) complexes of 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine
No full textWe report the synthesis of a new ligand, 4,4'-bis(3,5-dimethoxyphenyl)-6,6'-dimethyl-2,2'-bipyridine, optimised for binding to copper(I) and with pendant functionality that can eventually be developed into metallodendritic structures. The synthesis and photophysical properties of complexes with copper(I) and ruthenium(II) are reported. The solid state structure of the complex [Cu(1)(2)][PF6] center dot MeCN (1 = 4,4'-bis(3,5-dimethoxyphenyl)- 6,6'-dimethyl-2,2'-bipyridine) is also described. (C) 2008 Elsevier B. V. All rights reserved
Transitioning to Affordable and Clean Energy
Full text linkTransitioning to Affordable and Clean Energy is a collective volume which combines original contributions and review papers that address the question how the transition to clean and affordable energy can be governed. It will cover both general analyses of the governance of transition, including policy instruments, comparative studies of countries or policies, and papers setting out scientifically sound visions of a clean and just energy system. In particular, the following aspects are foregrounded: - Governing the supply and demand side transformation - Geographical and cultural differences and their consequences for the governance of energy transitions - Sustainability and justice related to energy transitions (e.g., approaches for addressing energy poverty) Transitioning to Affordable and Clean Energy is part of MDPI's new Open Access book series Transitioning to Sustainability . With this series, MDPI pursues environmentally and socially relevant research which contributes to efforts toward a sustainable world. Transitioning to Sustainability aims to add to the conversation about regional and global sustainable development according to the 17 SDGs. The book series is intended to reach beyond disciplinary, even academic boundaries
Transitioning to Affordable and Clean Energy
Full text linkTransitioning to Affordable and Clean Energy is a collective volume which combines original contributions and review papers that address the question how the transition to clean and affordable energy can be governed. It will cover both general analyses of the governance of transition, including policy instruments, comparative studies of countries or policies, and papers setting out scientifically sound visions of a clean and just energy system.
In particular, the following aspects are foregrounded: • Governing the supply and demand side transformation • Geographical and cultural differences and their consequences for the governance of energy transitions • Sustainability and justice related to energy transitions (e.g., approaches for addressing energy poverty) Transitioning to Affordable and Clean Energy is part of MDPI's new Open Access book series Transitioning to Sustainability. With this series, MDPI pursues environmentally and socially relevant research which contributes to efforts toward a sustainable world. Transitioning to Sustainability aims to add to the conversation about regional and global sustainable development according to the 17 SDGs. The book series is intended to reach beyond disciplinary, even academic boundaries
Transitioning to Affordable and Clean Energy
Full text linkTransitioning to Affordable and Clean Energy is a collective volume which combines original contributions and review papers that address the question how the transition to clean and affordable energy can be governed. It will cover both general analyses of the governance of transition, including policy instruments, comparative studies of countries or policies, and papers setting out scientifically sound visions of a clean and just energy system.
In particular, the following aspects are foregrounded: • Governing the supply and demand side transformation • Geographical and cultural differences and their consequences for the governance of energy transitions • Sustainability and justice related to energy transitions (e.g., approaches for addressing energy poverty) Transitioning to Affordable and Clean Energy is part of MDPI's new Open Access book series Transitioning to Sustainability. With this series, MDPI pursues environmentally and socially relevant research which contributes to efforts toward a sustainable world. Transitioning to Sustainability aims to add to the conversation about regional and global sustainable development according to the 17 SDGs. The book series is intended to reach beyond disciplinary, even academic boundaries
Shape switchable azo macrocycles
Full text linkThe present thesis is organized in three main chapters. The first section discusses a research project for the integration of azobenzene motives as a functional unit in macrocyclic molecular structures. The optically addressable switching units give access to two conformations with large differences in exterior form. Due to the rigid design with a m�terphenyl backbone and the integration of two azo units a considerable stabilization of the thermodynamically less favored cis�isomer is obtained.
In a second project the modification of platinum electrodes with different functional molecules, in order to obtain tailor made surfaces is investigated. By electrochemical grafting the electrodes with a suitable diazonium salt, an organic coated platinum electrode exposing iodoaryls is obtained. Subsequent Sonogashira cross-coupling chemistry with tailor made acetylene molecules allows substituting the exposed iodines with various functional groups. The new technique is improved in order to introduce a wide range of functional groups onto surfaces with a high surface coverage of functional subunits.
In a last project a bridged biphenyl as a novel molecular switch and memory device based on “mechanical” motion in a molecular biphenylic structure was synthesized. To alter the transport properties by an external stimulus, such as light, an azobenzene derivative as a bistable molecular subunit with state dependent length as the bridging system was integrated
Iron(II) pyridine-2-carbaldehyde-2-pyridylhydrazone complexes modified with Fréchet type dendritic wedges for scanning tunneling microscopy
Full text linkIron(II) pyridine-2-carbaldehyde-2-pyridylhydrazone complexes modified with Fréchet type dendritic wedges for scanning tunneling microscopy
Marc Häusler
Scanning tunneling microscopy (STM) is a technique of big importance in studying nanoscopic phenomena. While the behaviour of organic molecules on highly ordered pyrolitic graphite (HOPG) is well examined, not many complexes have been examined and studied.
Pyridine-2-carbaldehyde-2-pyridylhydrazone (Hpaphy) was selected for its possibilities for modification. To generate a favourable interaction between Hpaphy and the HOPG substrate Fréchet type dendritc wedges were coupled to Hpaphy. For the dendritic wedges several modifications were synthesized. Of three dendritic wedges crystal structures could be obtained showing the high purity and homogeneity of the compounds.
The iron(II) Hpaphy complexes show an interesting acid-base behaviour. The acidity of the amine proton on the Hpaphy backbone is strongly enhanced in the complex allowing for easy deprotonation. The deprotonation is accompanied by strong changes in solubity behaviour and UV-vis spectra.
While the dendritic wedges and the free ligand with the dendritic wedge gave monolayers that could be examined by STM the standard methods for monolayer formation, solution casting and liquid-slid interface, did not give observable monolayers of the complex compounds on HOPG. To overcome this problem Langmuir-Blodgett experiments were conducted. One compound was then selected for a deposition experiment and examined with STM
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