Ruthenium Compound Splits Water

If you work in the energy sector and your focus is on hydrogen, then chances are you spend a lot of time thinking about this reaction:

2H₂ + O₂ --> 2H₂O

Researchers in this field tend to fall into one of two groups. The first group wants to use hydrogen to generate energy, usually in the form of electricity via a fuel cell, and devotes its energies into driving the above reaction as far to the right as possible. The second group wants to use energy to generate hydrogen, usually by electrolysis, possibly using solar photons, and strives to drive the reaction as far to the left as possible. (A third group is concerned with hydrogen storage, using high surface area materials such as MOFs, but that’s a topic for another discussion). Although these the two groups would appear to be diametrically opposed, they have at least one thing in common. In both cases, the efficiencies of the processes are often dependent on the oxygen side of the reaction. During electrolysis, forming the O₂ is the hard part, which explains why most of the advancements in this area are related to the anode. The cobalt phosphate electrode coating announced by MIT last year would be one example. And in fuel cells, it’s the cathode that causes most of the headaches, since it’s more difficult to reduce O₂ then it is to oxidize H₂ (at the anode).

In an attempt to negate the need for electrodes, much work has been devoted to identifying transition metal complexes which might catalyze the photochemical splitting of water in solution. The results have been generally disappointing. In many cases, sacrificial reagents are required, usually to facilitate the formation of O₂, obviously limiting the usefulness of the process. In addition, since the H₂ and O₂ are usually co-generated at the same location, an additional step is required to isolate the H₂. Not good at all.

In a recent article in Science , David Milstein describes some ruthenium chemistry which may have some implications in the solar energy field. When water was added to a ruthenium compound they’ve been working with, a new hydrido-hydroxo complex was formed.



Upon heating, this new complex continues to react with water to produce a dihydroxo ruthenium complex along with free H₂. Irradiating this dihydroxo complex with a halogen lamp causes it to revert back to the original hydrido-hydroxo complex, along with the formation of O₂. Catalytic photochemical splitting of water without the use of sacrificial reagents. Not bad. Even better, since the H₂ and O₂ are produced during different steps, there are no separation issues to be dealt with. This process is a loooong way from being commercially viable, but I enjoy any chemistry where an organometallic compound reacts constructively with water without simply igniting or decomposing into an ugly pile of goo.

Clustered Water Chemistry

As an aqueous inorganic chemist by training (at least in grad school, although my horizons have expanded quite a bit due to my time in industry), I’ve spent a fair amount of time investigating and understanding the role of water in chemical reactions. When working with transition metals, this usually translates into accounting for aqueous coordination complexes, pH, and solvent effects. However, after perusing the Net these last few years, I now realize I have been woefully ignorant concerning the chemistry of water. I knew water tends to form loose clusters of molecules (due to hydrogen bonding), which accounts for some of its unusual properties, but I wasn’t aware of the immense importance of these clusters to its chemistry.

I am particularly upset that neither my professors nor my chemistry textbooks felt it necessary to cover this important aspect of aqueous chemistry. As a result, I’ve been forced to learn about clustered water on my own by visiting some rather arcane web sites – web sites that for some reason appear to contain a high percentage of viruses, bots, and other spyware. To make it even worse, most of the my information comes from sites which make a profit by selling devices or elixirs based on the unique properties of these water clusters, which means that the scientific basis for these properties are often poorly explained. (These people really need some spell checkers!)

Here is what I’ve been able to deduce from my research:

1. There is a form of clustered water which has very unusual properties. Scientists are generally unaware of this form of water since it disappeared from the earth in the distant past. However, it can still be found naturally in very old glaciers and newborn babies. Yes, we are born with our own supply of the stuff, but we lose it as we age (being replaced by ordinary water) and this leads to disease and the overall decay of our bodies. I can only assume the major pharmaceutical companies are working feverously on this in secret as I type.

2. Clustered water has a different surface tension than normal water. Unfortunately, there is disagreement as to whether it’s higher or lower. Regardless, this difference in surface tension allows it to permeate cell membranes more readily which keeps our cells more hydrated… and healthy… and happy.

3. Clustered water retains a memory of the impurities which were trapped inside these clusters in the past. Although this sounds suspiciously like the failed theory of "water memory" proposed by Jacques Benveniste, this time it’s for real! Unfortunately, this has led to some confusion amongst the makers of clustered water products. Some marketers want you to ingest water clusters which have been exposed to very dilute solutions of vitamins to help replenish the body. Others feel it is the ingestion of clustered water which has been previously exposed to toxins which causes all our problems. These people want to sell you devices for purging your body of bad clusters. The scientific world is still debating this one.

4. Clustered water can impart its properties to ordinary water. So it’s cheaper to buy a concentrated bottle of clustered water and dilute it with ordinary tap water.

5. Changing the bond angle within the water molecules results in a burst of light which affects your DNA. Apparently, this turns out to be a good thing. I’m not quite sure I understand everything that was explained on the web site, but I believe changing the bond angle can be done using sound vibrations. Gregorian chants are particularly good. In any case, we should all be aware of the possible effects of MP3 players on our lab experiments.

6. Clustered water is not to be confused with the fictional compound Ice-Nine, mentioned in Kurt Vonnegut’s book, Cat’s Cradle. Clustered water is real.


If you wish to read more about this fascinating area, visit the Water Cluster Quackery page.

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Woohoo! We now have vending machines at work! Our work site now is relevant!

Hooray! Aqueous Transition Metal Chemistry Talks

I really miss going to ACS meetings, but with chemistry not being as big a focus at my company anymore, it can be difficult to justify (to upper management) the expense of going to one unless there is a session directly related to my current project. I attended a session on reforming catalysts several years ago, but that’s been it for a while. Besides, my true love is aqueous transition metal chemistry and those types of talks can be few and far between. So imagine my surprise and delight when I ran across blogs discussing, not one, but two such talks being presented at this week’s national ACS meeting.

The first talk was mentioned on the Chemistry Blog, concerning a study to use chelating agents like EDDA to extract actinides from nuclear waste. YES! Good, old-fashioned aqueous transition metal chemistry. Okay, actinides aren't strictly transition metals, but they're close enough. I did find it amusing when Mitch wrote "These types of systems look promising and are a nice upgrade over traditional old-school extractors like tributylphosphate(TBP)." Any reference to classic chelating agents as "new-school" is music to my ears. To be honest though, I would have thought that these chelators, especially EDDA, would have been tested for this application a long time ago. At least it shows there are still applications for this type of chemistry yet to be discovered.

The second talk involved the use of Fe-TAML complexes to facilitate the oxidation of organic pollutants by hydrogen peroxide. Apparently these complexes are good mimcs of peroxidase enzymes. Here is the structure of the compound taken from the Collins group website:


Although I haven't had the chance to read the mechanistic and kinetic work on these reactions yet, this seems like a classic example of the TAML group basically locking the Fe into a square planar configuration and keeping it stable while it’s shuttling back and forth between the +2 and +3 states as it facilitates the transfer of electrons between the H2O2 and the target molecule. I've always had a soft spot for chelating agents that lock themselves around metals in tight, specific configurations, significantly changing the metal's properties in the process. My first undergraduate project used an amine oxime to wrap itself around cobalt in a manner resembling the structure of cobalamin (B12 vitamin). Classic aqueous transition metal chemistry. It brings a tear to my eye.

Aqueous Chemistry Rules!

Apparently, polyoxometalates have been found to be "very powerful inhibitors of a specific protein kinase, CK2, an enzyme that is overactive in a number of cancers." I say apparently, since it was reported in the journal "Chemistry and Biology," a journal to which I do not have access. I only know of the study because of this press release. Polyoxometalates are large anionic clusters generally consisting of transition metals and oxygen. A good description can be found here. This study is of particular interest to me since I have worked with polyoxometalates of V, Mo, and W in the past. I admit to having lost touch with them over the years, mostly because my work at that time involved aqueous polymetalates (I love aqueous chemistry!) and subsequent research on polymetalates had begun turning to derivatives which were only soluble in organic solvents. So it was with some delight that I discovered that aqueous polyoxometalates had reappeared in the literature. Unfortunately, the press release gives very few details about the particular polyoxometalates involved or what kind of chemistry is occurring. In fact, I am only assuming that these are aqueous species since they are being used in biological systems. In any case, since aqueous chemists seem to be vastly outnumbered by non-aqueous chemists (I was definitely in the minority in the U of Illinois Inorganic Chemistry department), I am always happy to see a paper on aqueous chemistry that is at least somewhat mainstream.

Are there any aqueous inorganic chemists out there reading this blog?
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My family and I will be leaving tomorrow to visit my parents in Springfield, Missouri for 5 days. I've talked about Springfield before, so it's always a fun trip, but I won't be updating the blog until next week. In the meantime, here is the previously promised picture of my garden (or at least a small part of it).