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Unexpected isomerism

17 Feb 2012

Phenanthroline-based complexes are increasingly finding use in heterogenous catalysis. One class of phenanthroline ligand is neocuproine – a dimethyl substituted derivative which Fabio Ragaini and his team have been interested in to mechanistically study the carbonylation of nitroarenes to carbamates.

When Ragaini et al. started working with the palladium neocuproine complexes, it appeared that minor variations in the synthetic procedure gave products with very different solubility properties, even though the elemental analysis data matched what was expected. In light of this, Ragaini and his team scoured the literature, upon which they discovered inconsistencies regarding the reported solubility of the [Pd(Neoc)X₂] (X = Cl, Br, I) complexes.

Bearing this in mind, Ragaini et al. decided to further investigate the nature of these compounds. They discovered that for each compound in the series, two structural isomers exist: one isomer is neutral and the second is ionic. Formation of the ionic isomer occurs under a much wider range of experimental conditions than the neutral isomer. The ionic isomer must have been synthesised in previous reports even if formation of the neutral one was claimed, say the authors.

It has already been shown that the way palladium–phosphine complexes are synthesised can affect the nature of the final product, in particular its catalytic activity. Ragaini and colleagues’ paper reiterates this for nitrogen-containing ligands and highlights the importance of correctly identifying a product’s structure.

Read the Dalton Transactions article in full to find out more:
Unexpected isomerism in “[Pd(2,9-dimethylphenanthroline)X₂]” (X = Cl, Br, I) complexes: a neutral and an ionic form exist
Martino Rimoldi, Fabio Ragaini, Emma Gallo, Francesco Ferretti, Piero Macchi and Nicola Casati

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Silver Complexes Kill Cancer Cells

08 Feb 2012

Cisplatin is a well known chemotherapy drug used to treat a range of cancers. While the drug can be an effective treatment there are notable unwanted side-effects, which can include nausea, vomiting, kidney damage and loss of hearing. This new research from Leeds University by Charlotte Willans et al. details the activity of a range of silver complexes containing N-heterocyclic carbene (NHC) ligands which show comparable and even enhanced cytotoxicity compared to cisplatin. As the compounds don’t contain platinum they are likely to be less toxic and therefore exhibit fewer and less severe side-effects.

The team synthesised a series of monodentate, bidentate and macrocyclic cationic silver bis(NHC) complexes and tested their activity with cell lines of breast and colon cancer (MCF7 and DLD1 lines respectively). They found that the bidentate complexes showed enhanced cytotoxicity over the monodentate and macrocyclic ligands, which were similar to cisplatin. As yet the exact mechanisms of action are still unclear but are likely linked to the stabilities of the complexes.

For more information about this exciting research you can download the article which is free to access for 4 weeks. You can also keep up to date with all the latest news in inorganic chemistry by following us on twitter or signing up to the Dalton Transactions e-alert service.

Enhanced cytotoxicity of silver complexes bearing bidentate N-heterocyclic carbene ligands
Charlotte E. Willans, Diana C F Monteiro, Roger M Phillips, Benjamin D Crossley and Jake Fielden
Dalton Trans., 2012, Accepted Manuscript
DOI: 10.1039/C2DT12399A

Also of interest from the collection ‘Highlights in Chemistry’

Therapeutic applications of gold complexes: lipophilic gold(III) cations and gold(I) complexes for anti-cancer treatment
Chi-Ming Che and Raymond Wai-Yin Sun
Chem. Commun., 2011, 47, 9554-9560
DOI: 10.1039/C1CC10860C, Highlight

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Carboxylate complexes going for gold!

25 Jan 2012

Gold nanoparticles (Au-NPs) are attractive for applications in important technological fields as components of biosensors, novel catalysts and new optical, magnetic or electrical devices. Traditional techniques for their preparation include thermal decomposition of organometallic precursors, chemical reduction of Au(I) ions, and electrochemical and photochemical processes. Methods based on reduction by sodium borohydride or citrate ions have been used successfully as the reducing agent acts also as a stabilizer and prevents further aggregation.

As an alternative, Heinrich Lang, from Chemnitz University of Technology, and coworkers have developed a family of gold(I) carboxylate complexes which can be used as precursors for the preparation of Au-NPs in a single step. The ligand works as the reducing and stabilizing part, simultaneously, in one molecule. After thermally induced decomposition of the complexes, Au-NPs are obtained with sizes in the range from 3.3 to 6.5 nm, and almost homogenous size distribution. The ethylene glycol-functionalized carboxylates were obtained from easy chemical reactions using available ethylene gycol or directly from commercial suppliers, and the complexes obtained by a two step procedure. The authors report than larger chain lengths increased stability and slowed particle growth.

To find out more about it, read the full paper in Dalton Transactions.

Gold nanoparticles generated by thermolysis of “all-in-one” gold(I) carboxylate complexes
André Tuchscherer, Dieter Schaarshmidt, Steffen Schulze, Michael Hietschold, Heinrich Lang,
Dalton Transactions, 2012, Advance Article
DOI: 10.1039/c2dt11748g

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Bacteria are not welcome here: antibacterial surfaces produced in glass

25 Jan 2012

To catch a bacterial infection after a visit to a hospital for a health checkup is not a funny way to become sick. Even worse is when the infection came from a device which was supposed to help you to get better, not sicker, such as a medical device. Intra-hospital infections are difficult to avoid as some viruses or bacterias deposit on any surface available, which may become in contact with a healthy person, with potential health consequences. Numerous approaches have been looked at in order to create materials with anti-bacterial capabilities. In this direction, silver and copper nanoparticles (AgNP and CuNP) are attractive as they may be able to avoid propagation of several microorganisms, including E. coli and S. aureus. Several methods have been tried to successfully immobilize the nanoparticles to a surface.

Giacomo Dacarro and coworkers at the Università degli Studi di Pavia at Italy, have devised a new way to chemically modify Si-OH terminated surfaces (glass, quartz, SiO₂) by using a novel silane-derivatized polyethylenimine (PEI) and testing its ability to coordinate Ag⁺ and Cu²⁺ ions, and silver nanoparticles. The functionalized glasses are very effective in fighting against E. coli and S. aureus propagation, and may be an novel platform for use in designing smart, hybrid multifunctional materials.

Read more about his paper published in Dalton Transactions.

Monolayers of polyethilenimine on flat glass: a versatile platform for cations coordination and nanoparticles grafting in the preparation of antibacterial surfaces
Giacomo Dacarro, Lucia Cucca, Pietro Grisoli, Piersandro Pallavicini, Maddalena Patrini and Angelo Taglietti
Dalton Trans., Advance Article, 2012.
DOI: 10.1039/c1dt11373a

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Nano strikes again! Cross coupling catalytic activity of copper nanoparticles supported on silicon nanowires

24 Jan 2012

Noble metals are highly regarded as unique catalysts for use in several reactions, many of them of interest for the pharmaceutical industry. However, their cost may be a reason why not to be considered in several applications. When used in the form of nanoparticles, an increase of their activity is expected as a result of their large specific surface area, even when small amounts are used, which can save money and time. In the search for more efficient ways to form C-N bonds, a variety of homogenous catalysts such as Cu, Pd and Rh have been investigated in order to tune them and improve their ability to promote cross-coupling reactions among aryl halides and amines. Specifically, copper mediated Ullmann condensation is attractive as it is cheaper than Pd or Rh.

Zhenhui Kang and his group at the Institute of Functional Nano and Soft Materials and the Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices at Soochow University have developed a new catalyst based on copper nanoparticles inmovilized on silicon nanowires (CuNPs@SiNWs). This catalyst is able to enhance the coupling reaction at 110 °C among benzene halides and aniline in good yields, without the use of any ligand or additive. Even deactivated aryl bromides and inert chlorobenzene were reactive under the action of this novel catalysts. The authors suggest that the use of SiNWs as an alternative substrate support may be of interest of other researchers in the quest of superior heterogeneous catalysts.

For further information, read the work by Zhenhui Kang and coworkers published in Dalton Transactions.

Copper nanoparticles modified silicon nanowires with enhanced cross-coupling catalytic ability
Keming Pan, Hai Ming, Hang Yu, Hui Huang, Yang Liu, Zhenhui Kang
Dalton Trans., Advance Article, 2012.
DOI: 10.1039/c2dt12182d

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Happy Chinese New Year

23 Jan 2012

The Dalton Transactions team wishes you every success in the Year of the Dragon, and we hope that you enjoy your New Year holiday.

In celebration we have made these recently promoted Dalton Transactions Hot articles free to access for the whole of February:

Ba2AgInS4 and Ba4MGa5Se12 (M = Ag, Li): syntheses, structures, and optical properties
Wenlong Yin, Kai Feng, Dajiang Mei, Jiyong Yao, Peizhen Fu and Yicheng Wu
DOI: 10.1039/C2DT11895E

Synthesis and properties of a dendritic FRET donor–acceptor system with cationic iridium(III) complex core and carbazolyl periphery
Yanfang Li, Yang Liu and Ming Zhou
DOI: 10.1039/C1DT11716E

Three novel Bi(III) complexes with in situ generated anilate ligands: unusual oxidation of cyclohexanedione to dihydroxy benzoquinone
Hui Gao and Xian-Ming Zhang
DOI: 10.1039/C1DT11258A

(Zn, Mg)2GeO4:Mn2+ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties
Mengmeng Shang, Guogang Li, Dongmei Yang, Xiaojiao Kang, Chong Peng, Ziyong Cheng and Jun Lin
DOI: 10.1039/C1DT10673B

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Call for Papers: Polyoxometalates

05 Jan 2012

We are pleased to announce an upcoming themed issue on Polyoxometalates, guest edited by Leroy Cronin and Deliang Long. It is our pleasure to invite you to contribute to this themed issue.

During the last few years, poloyoxometalate (POM) chemistry has growth significantly. Thanks to its versatile nature in terms of structure, size, redox chemistry, photochemistry, and charge distribution, POM chemistry is one of the areas in inorganic chemistry that is developing most rapidly. Today, developments in POM research continue at a great pace, and new areas are emerging that are multidisciplinary, and exploit the great structural and electronic diversity of POM-based systems. The future of POM chemistry has many exciting new dimensions, interacting with materials, nanotechnology, biology, surfaces, catalysis, supramolecular materials, colloid science, and electronic materials. This Dalton Transactions themed issue will highlight to the inorganic research community the latest and very best research in POM chemistry.

How to submit?
All types of manuscript, Communications, Full Papers and Perspectives, will be considered for publication. We aim to publish this themed issue in the second half of 2012 and therefore would like to receive manuscripts by 28th February 2012. The manuscript should be prepared according to the format for regular articles and should be submitted via our online system. All invited manuscripts will be subject to the normal refereeing procedure.

Read some recently published polyoxometalate articles:

Exploring the rotational isomerism in non-classical Wells–Dawson anions {W18X}: a combined theoretical and mass spectrometry study
Laia Vilà-Nadal, Scott G. Mitchell, De-Liang Long, Antonio Rodríguez-Fortea, Xavier López, Josep M. Poblet and Leroy Cronin
Dalton Trans., 2012, DOI: 10.1039/C2DT11919F

Water oxidation catalyzed by a new tetracobalt-substituted polyoxometalate complex: [{Co4(μ-OH)(H2O)3}(Si2W19O70)]11−
Guibo Zhu, Yurii V. Geletii, Paul Kögerler, Helmut Schilder, Jie Song, Sheri Lense, Chongchao Zhao, Kenneth I. Hardcastle, Djamaladdin G. Musaev and Craig L. Hill
Dalton Trans., 2012, Advance Article
DOI: 10.1039/C1DT11211B

New trends in polyoxometalate photoredox chemistry: From photosensitisation to water oxidation catalysis
Carsten Streb
Dalton Trans., 2012, Advance Article
DOI: 10.1039/C1DT11220A

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