Dalton Transactions Blog

Organic radicals in a self-assembled grid

26 Oct 2012

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Konstantin Shuvaev, Annie K. Powell and colleagues have designed a ligand containing the nitronyl nitroxide radical. The ligand can self-assemble with copper(II) ions to give a [2 x 2] grid complex.

The nitronyl nitroxide radical coordinated via the oxo-atom of the N+-O- fragment in a chelating fashion and lies in the equatorial plane of the metal ion.

The high reactivity of organic radicals makes them difficult to use but the nitronyl nitroxide radical is one of the most stable and so can be used in the design of paramagnetic polytopic ligands as building blocks for supramolecular grids. Most previous supramolecular grids have been made using diamagnetic ligands but the team found that being able to use a paramagnetic ligand resulted in a grid with interesting spin coupling and magnetic properties.

CNC pincer ligand catalyst

18 Oct 2012

By Fiona McKenzie, Executive Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Scientists in Mexico and Spain have synthesised a ruthenium complex using a N-heterocyclic CNC pincer ligand.

Lutidine-derived pincer complexes are well established amongst organometallic chemists. More traditionally, the pincer ligand motif, PNX has been utilised (where P is a phosphine and X is either a phosphine or N donor ligand) but substitution of phosphines with stronger electron-donating N-heterocyclic carbenes has meant that more active catalytic species have been made for promoting hydrogenation of non-active esters. Mostly speaking, these ligands follow a CNN coordination pattern. According to the researchers, the only CNC pincer complex reported coordinates to the ruthenium centre in a mer geometry.

In their latest Dalton Transactions Communication, the team report on the synthesis of a CNC ligand which coordinates to ruthenium in an usual fac mode. They proved that the resultant complex can be used to catalyse the hydrogenation of imines by firstly deprotonating one of the ligand methylene bridges.

To read more about this development, read the full article now…

Hydrogenation of imines catalysed by ruthenium(II) complexes based on lutidine-derived CNC pincer ligands
Martín Hernández-Juárez, Mónica Vaquero, Eleuterio Álvarez, Verónica Salazar and Andrés Suárez
Dalton Trans., 2012, Advance Article

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Persistently luminescent: long lasting phosphor MOF

18 Oct 2012

By Leah Morris, Web Writer.

In recent years, metal organic frameworks (MOFs) have received a great deal of research interest due to their application for gas storage, catalysis and for use as sensors. By choosing different metals and organic linkers, the pore shape and size can be tuned for one’s particular need.

In this article, Yue-ying Ching and colleagues have reported a MOF which has green persistent luminescence. To the researchers’ knowledge, persistent luminescence has not been reported in MOF’s before. The luminescence lasts for about 1 second which means that this material can be classed as a long lasting phosphor (LLP). LLPs have decay times of seconds, minutes and in some cases hours making them useful for LEDs and emergency lighting, amongst others.

The preparation of conventional LLPs requires extreme reaction conditions (temperatures of at least 1000ºC!). This new MOF was synthesized using solvothermal conditions at 115ºC. This work provides an exciting new route towards LLPs, without the need for co-dopants or extreme synthesis conditions.

To find out more, download the article now….

Promising long-lasting phosphor material: a novel metal–organic framework showing intriguing luminescent performance
Feng Luo, Gong-Ming Sun, An-min Zheng, Shi-xun Lian, Ying-liang Liu, Xue Feng Feng and Yue-ying Chu.

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Articles from around the world: Japan

11 Oct 2012

By Matthew Cude, Development Editor.

Matsumoto Castle, Nagano Prefecture. Built in 1504 the castle's origins go back to the Sengoku period

This month we have collected together some of the excellent articles published in Dalton Transactions from Japan, all are free to download until 9^th November!

You can also submit your manuscript to our Japanese Editorial Office, managed by Associate Editor Professor Masahiro Yamashita.

Click here to see the full list of articles

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Mononuclear Pacmans

09 Oct 2012

By Fiona McKenzie, Executive Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

As Jason Love described in his 2009 ChemComm Feature Article, pyrrole-based macrocycles are ideal ligands for creating pre-organised metal binding sites to enable the multielectron redox chemistry so required for transforming small molecules such as O₂, carbon dioxide and water.

Here in their latest Dalton Transactions article, Love and colleagues take this a step further.

The team note how their previous attempts to make mononuclear transition metal complexes with the donor ligands were unsuccessful. Despite significant efforts, they could only make bimetallic complexes – well, until now that is…

The newest set of ligands now incorporate N₄^¬with either O₅ or ONO donors which are separated through aryl spacers. Upon binding of a singular metal atom, the complexes fold to form a Pacman-like cleft structure. Love and colleagues expect the structure to play host to guest molecules which can benefit from metal coordination as well as hydrogen bonding interactions to the oxygen and nitrogen atom acceptors.

To read more, download the article now…

Synthesis and structures of transition metal pacman complexes of heteroditopic Schiff-base pyrrole macrocycles
James W. Leeland, Colin Finn, Bérengère Escuyer, Hiroyuki Kawaguchi, Gary S. Nichol, Alexandra M. Z. Slawin and Jason B. Love

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Studying hydrogen activation of FLPs

04 Oct 2012

By Fiona McKenzie, Executive Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Scientists from Pacific Northwest National Laboratory have investigated the mechanism of heterolytic H₂ activation by frustrated lewis pairs (FLPs). To do this, they employed an unique approach of solution calorimetry and were able to obtain the enthalpies and relative rates of H₂ activation.

With the exception of previous studies that partly relied on theoretical calculations, there has not been a great deal of work devoted to understanding how molecular hydrogen is activated by FLPs. Autrey and colleagues have found that H₂ activation rates using such species are relatively fast considering no metals are involved. They discovered that the rate was dependent on the structure of the Lewis basic amine involved, and that diffusion of hydrogen across the gas-liquid interface is not rate limiting.

Further work is needed to extract fundamental rate constants, kinetic orders, and activation barriers, say the researchers.

Read the article now to find out more…
A thermodynamic and kinetic study of the heterolytic activation of hydrogen by frustrated borane–amine Lewis pairs
Abhi Karkamkar, Kshitij Parab, Donald M. Camaioni, Doinita Neiner, Herman Cho, Thomas K. Nielsen and Tom Autrey

This article is part of an upcoming themed issue on Boranes and Borohydrides, guest edited by Simon Aldridge. Other articles by this author include:

Methods to stabilize and destabilize ammonium borohydride
Thomas K. Nielsen, Abhi Karkamkar, Mark Bowden, Flemming Besenbacher, Torben R. Jensen and Tom Autrey

Also of interest… Take a look at our recent themed issue in Frustrated Lewis Pairs

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Group 4 tetracarbamato complexes for lactide polymerization

24 Sep 2012

By Katie Renouf, Web Writer.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Ever since Ziegler and Natta’s 1950s discovery of TiCl₄ as a catalytic precursor for alkene polymerization, interest in similar compounds with potentially superior properties has soared.

Biodegradable polylactic acid cups

Polylactide, polyglycolide and polycaprolactone are all commercially available biodegradable polyesters with advantages over non-biodegradable alternatives. They are used primarily in biomedical applications ranging from sutures, screws and pins to drug delivery and dentistry. Biodegradable polymers have also found uses in areas as diverse as compostable food packaging, plastics repair and rapid prototyping.

Marchetti et al. have reported a number of group 4 N,N-dialkylcarbamato complexes alongside their catalytic properties with regard to the ring opening polymerization of rac-lactide. They have also studied their polymerization mechanisms in great detail, concluding that the first stage of the polymerization reaction proceeds through different pathways for the Ti, Zr and Hf analogues, explaining the observed differences in activity. All pathways produce a vacant metal site, which is required for further propagation.

Read more about these new group 4 tetracarbamates and their application as catalytic precursors for the polymerization of rac-lactide in this HOT article.

Ring opening polymerization of rac-lactide by group 4 tetracarbamato complexes: activation, propagation and role of the metal
Fabio Marchetti, Guido Pampaloni, Calogero Pinzino, Filippo Renili, Timo Repo and Sirpa Vuorinen

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Ammonium borohydride – a promising hydrogen storage material?

24 Sep 2012

By Helen Lunn, Publishing Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Hydrogen has been investigated for some time as a possible renewable energy source but its practical application has been limited by storage problems. In this HOT article, Tom Autrey and co-workers have studied the stabilisation and destabilisation of ammonium borohydride with a view to its use as a promising hydrogen storage material. The results suggest that ammonium borohydride could be stabilized by high pressure hydrogen or inert gas.

Dalton Transactions Blog

Organic radicals in a self-assembled grid

Top ten most accessed articles in September

CNC pincer ligand catalyst

Persistently luminescent: long lasting phosphor MOF

Articles from around the world: Japan

Mononuclear Pacmans

Studying hydrogen activation of FLPs

Top ten most accessed articles in August

Group 4 tetracarbamato complexes for lactide polymerization

Ammonium borohydride – a promising hydrogen storage material?

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