Spectroscopy
Papers and research that Sir Harry Kroto worked on, in the area of spectroscopy.
The Cyanopolyyne long chain molecules
In 1973, Sir Harry Kroto and his colleague David Walton created a degree by thesis project for an undergraduate student, Alec Alexander.
The project entailed the synthesis of long carbon chain molecules starting with HC5N. This would have be very easy to detect by microwave spectroscopy as it would have a big dipole moment.
Read more about the microwave spectra of the cyanopolyynes.
Download the Polyyne section of the Tilden lecture (4.23MB).
View the wide band trace of HC5N I (PDF, 4.05MB) and HC5N II (PDF, 1.94MB).
The first detection and isolation of the phosphaalkenes (eg CH2=PH) and general methods for creating phosphaalkynes (eg CH3C≡P)
Following on from pioneering work on thioaldehydes and ketones, the first Phosphaalkenes (which contain C=P moieties, eg, CH2=PH) were created. The general synthetic routes to this whole new family were developed in 1974-75.
Also, there was the development of general methods of synthesising Phosphaalkynes (RC≡P species such as MeC≡P which have triple bonds between carbon and phosphorus) when only HCP was known and had been around for nearly 15 years.
Although some of these species had been conjectured to exist as intermediates, it was these studies which led to their isolation and characterisation and, in particular, ushered in the new fields of Phosphaalkene and Phospahalkyne chemistry.
This work was carried out by Sir Harry Kroto in collaboration with his Sussex colleague, John Nixon.
Sir Harry Kroto's account of the discovery and isolation of the phosphaalkenes and phosphaalkynes
Sir Harry Kroto, "In 1964, when I arrived at NRC, I met to Takeshi Oka who told me about the molecule HCP, the phosphorus analogue of HCN, which a previous post-doc Kelvin Tyler had studied by electronic spectroscopy. It had been made several years before by Gierr.
This really intrigued me because I thought that if HCP could be made then why not analogues such as for instance CH3CP. This was on my mind for nearly ten years.
Sir Harry Kroto
"When I got my own microwave spectroscopy spectrometer in 1974, I was in the coffee room one day and I consulted my colleague at the University of Sussex, John Nixon, to find out whether he had any likely precursors of double bonded and triple bonded carbon phosphorus molecules.
"A new research student, Nigel Simmons, was started on the project and almost immediately it was successful. There was a wide range of phosphaalkenes, a completely new class of molecules, and a wide range of new analogues of HCP (phosphaalkynes) which had never been made before."
CH2PX paper
I consider this paper one of the most intellectually satisfying contribution (perhaps the most) I have ever made. I thought it must be possible to make a carbon phosphorus double bonded molecules and it worked beautifully.
Sir Harry Kroto
Sir Harry Kroto continued, "It has only around 100 citations but it was the paper that gave birth to the general field of Phosphaalkene Chemistry! So much for citations!"
Download the paper (PDF, 247KB).
The detection of unstable molecules by microwave spectroscopy
'Phospha-alkenes CF2=PH, CH2=PCl, and CH2=PH', M Hopkinson, H Kroto, J F Nixon and N P C Simmons, School of Molecular Sciences, University of Sussex.
Read an overview of the program, the CP section of the Tilden lecture (PDF, 720KB).
Sir Harry Kroto, "In the beautiful spectrum, we see that CH3PCl2 thermalises to form CH2PCl by eliminating one unit of HCL. Furthermore, one sees rather nicely that two units are also eliminated to form HCP, the only phosphaalkyne known before our general synthetic breakthrough."
General methods of creating thioaldehydes thioketones and boron sulphides etc, MeCHS, CH2=C=S, CIBS
Sir Harry Kroto, "In around 1970 I was trying to produce the new molecule thio formaldehyde from dimethyl disulphide by flash photolysis. Remember that at this time there was something called the double bond rule, which indicated that molecules with double bonds between carbon and second and third row elements were either not makeable or unstable. However the mere fact that OCS is stable as CS2 suggests that this rule is unreliable.
"I had previously observed formaldehyde by pyrolysis of dimethyl peroxide. However dimethyl peroxide is much more easily photolysed than dimethyldisulphide.
"Just about this time I was at a conference in Dijon where Don Johnson from NBS presented a paper on this molecule which he had produced simply by using a Bunsen burner on a quartz tube through which he passed dimethyl disulphide and had detected it by microwave spectroscopy. I realised that this might be a general method to obtaining some semi-stable thioaldehydes and ketones and asked Don whether he was interested in going further along this avenue as I was.
"He said he was not and so was initiated a highly successful program on new sulphur-containing compounds such as thioacetaldehyde and other very interesting species."
Read an overview of the synergistic technique we used.
Read an overview of the species such as thioaldehydes, thioketones seleno analogues and thioborines in the thio seleno section of the Tilden lecture (PDF, 556KB).
Discussion
The ramifications of the results on new molecules are talked about in the discussion section of the Tilden lecture (PDF, 505KB).
Acknowledgements
Sir Harry Kroto considers it a great pleasure to acknowledge the hard work of his co-workers in this research:
- Anthony Alexander
- James Burckett-St. Laurent
- Allan Careless
- Terry Cooper
- Krini Georgiou
- Marcus Durrant
- Mike Hutchinson
- Mike King
- Colin Kirby
- Barry Landsberg
- Don McNaughton
- Mike Maier
- Osamu Ohashi
- Keiichi Ohno
- Nigel Simmons
- Roger Suffolk
- Nick Westwood
Sir Harry Kroto would also like to acknowledge the debt he owes to his Sussex colleagues, John Nixon with whom the phosphorus work has been carried out and David Walton with whom the polyynes were studied.
In addition, the help and encouragement of Michael Lappert, Bill McCrea, John Murrell and Jim Watson have been consistent and invaluable.
Finally, Kroto adds that it has been a pleasure to collaborate with Takeshi Oka, Lorne Avery, Norm Broten, and John MacLeod in the radio-astronomical work.