Probing ground and excited state properties of Ruthenium(II) and Osmium(II) polypyridyl complexes Wesley R. Browne A Thesis presented to Dublin City University for the degree of Doctor of Philosophy. 2002 Probing ground and excited state properties of Ruthenium(II) and Osmium(II) polypyridyl complexes Isotope, pH, solvent and temperature effects. by Wesley R. Browne, BSc.(Hons), AMRSC A Thesis presented to Dublin City University for the degree of Doctor of Philosophy. Supervisor: Professor Johannes G. Vos School of Chemical Sciences Dublin City University August 2002 Dedicated to Matthew & to the memory of Ross and Mick “Caste a cold eye on life, on death. Horseman pass by” Epitaph fo r William Butler Yeats REFERENCE I hereby certify that this material, which I now submit for assessment on the programme of study leading to the award of Doctor of Philosophy by research and thesis, is entirely my own work and has not been taken from work of others, save and to the extent that such work has been cited within the text of my work. I D. No. 95478965 Date:_______ ( ( / Û / iv Abstract The area of ruthenium(H) and osmium(H) polypyridyl chemistry has been the subject of intense investigation over the last half century. In chapter 1, topics relevant to the studies presented in this thesis are introduced. These areas include the basic principles behind the ground and excited state properties of Ru(II) and Os(II) polypyridyl complexes, complexes incorporating the 1,2,4-triazole moiety and the application of deuteriation to inorganic photophysics. Chapter 2 details experimental and basic synthetic procedures employed in the studies presented in later chapters. A limited discussion of practical aspects of both synthetic procedures and physical measurements is included, in particular where major difficulties were encountered and where improvements to standard procedures were made. A central theme to this thesis is the application of deuteriation as a spectroscopic probe. In order to fully exploit its potential fully, a general and systematic approach to the deuteriation of polypyridyl type ligands is required. In chapter 3 a range of isotopomers of heteroaromatic compounds containing pyrazyl-, pyridyl-, 1,2,4-triazole-, thienyl-, methyl-, and phenyl- moieties, are reported. The application of deuteriation in inorganic chemistry as a spectroscopic probe both in simplification of NMR and Raman spectra and as a probe into the excited state structure of heteroleptic complexes is the focus of chapter 4. Deuteriation is employed extensively to probe the excited state structure of several series of Ru(II) and Os(II) polypyridyl complexes. In particular the effect of deuteriation on emission lifetime and ground and excited state resonance Raman spectra is investigated. In chapter 5, the phenomena of temperature dependent dual luminescence observed for the mononuclear complex [Ru(bpy)2 (pztr)]+ forms the basis of a wider investigation of related complexes in an effort to gain more insight into the nature of the phenomenon. In addition some fundamental studies into the picosecond excited state processes of [Ru(bpy)3 ]2+ are presented. In these studies deuteriation shows itself as a powerful tool in effecting small but important perturbations. In Chapter 6 the separation, characterisation and photophysical properties of the stereoisomers of mono- and bi-nuclear Ru(II) polypyridyl complexes is examined. In particular the importance of chirality both in terms of solvent and in complex in determining the circular dichroism, ]H NMR spectroscopy and photophysical properties is investigated. In chapters 7 and 8, attention is turned to binuclear systems incorporating 1,2,4-triazole moieties. The effects of variations in the bridging ligand in these systems (e.g., distance and spacer groups, pyrazine vs. triazole etc.) are examined. Deuteriation is employed in some of these systems as a tool in assessing the localisation of the lowest emissive excited state on particular moieties of the complexes. v Acknowledgements Where do I start! At the beginning I suppose. M y Family: Thank you Mum for unrelenting support throughout that epic 21 year quest that is known as an education and for the many heated discussions we have had over those years. I won’t forget it in your twilight years (I am sure I will be able to arrange a job in an old folks home for you). To my sister “Garda Nicola Browne” for always being there for me, despite the fact I manage to get on your nerves without even trying. Next to Mick for all the trouble you’ve caused in the few years I have known you (namely Ross and Matthew), thank you for being a friend; you are not forgotten. To Ross, whom is always there like the warm glow of an open hearth. And last but by no means least to Matthew for being, well, Matthew, the ultimate in long-lived excited states. M y Mentors', the main man, Han, the boss, a.k.a Prof. J.G. Vos. The first day I started my postgrad you said something that set the tone for the following three years- “0 / course you can harass me - but come in and close the door first”. And it went downhill after that. Thanks for the enthusiasm, interest and encouragement over the years and for the freedom to do what I was interested in. Also thanks Ronald (Dr. Ronald Hage), for convincing me to do a Phd in the first place and for being the perfect boss (i.e. leaving me alone to get on with it; must be a dutch trait). And finally to my Sensei (Mr. John Sweeney) for teaching me self-discipline, how to be a true martial artist and for keeping me focused through my teenage years. My friends in the North. Firstly to Prof. J. J. McGarvey for allowing me to use his Raman facilities at Queen’s University Belfast and sending me to R.A.L.. Thanks Colin (take a break) Coates and Clare (how did you survive the years with Colin!!) Brady. Oh, and thanks Pavel, Mike and Stan with those ultrafast thingies. And also to Kate, Ali and Murph for making Belfast more welcoming. On the International seen: Bologna, Italy - Firstly thanks to Mama (Prof) Teresa and Papa (Prof) Roberto for helping me learn something about real photophysics and for making me feel welcome on my visits to Bologna. To the family Passaniti, for putting me up in Bologna and for welcoming me with open arms. And to Paolo, a gentleman and a scholar (and a stirrer if ever there was one). To Cincia and Sebastiano in Messina thanks for an interesting adventure that was the DPY/DPZ saga! To Dr. Dusan Hesek and Dr. Claudio Villani (maybe we will actually meet some day) for help with chiral separations. My proof readers Jennifer McKenna and Aine Connolly (you didn’t know what you were letting yourselves in for!). This thesis would not have read near as good without your help. As for the mistakes still in it, I take full responsibility as they are entirely my own (and Han’s). Thanks also go Sligo VEC and Enterprise Ireland for helping me out with a few quid over the years and to the SCS for the facilities in which to do the work. On the Technical side; I would like to thank all the technicians in the School of Chemical Sciences for being the most capable and professional group of people I will probably ever have the pleasure of working with. My thanks to Mick (an all round good egg if ever their was one), Maurice (Jim‘ill fix it for you), Damien (scuba boy), Veronica and Ann (for vi sorting out the mess that is the ordering system and more importantly the mess I usually made of it), Ambrose, Vinny, John, Mary and Tony. On the staff side, I thank especially Dr. Mary Pryce, Dr. Paraic James, Dr. Peter Kenny, Dr John Gallagher, Dr. Josh Howarth and Dr. Kieran Nolan for the invaluable advice they have given over the years. On the PGAC side, Prof. Malcolm Smyth, Prof. Robert Forster, Mick Burke (again!) Kathleen Greenan, Ger McDermott, Marion King, Jennifer Brennan, Dr. Brett Paul and Dr Dermot Brougham. It was an interesting experience that I am thankfully none the worse for. Keep up the good work. My friends/colleagues- there are too many to name but a few bear special mention: Firstly, in the HVRG past and present, again in no particular order. Dr Christine (have you got another paper written for me yet) O’Connor (is it D.O’C or C.O’C), Dr Francis Weldon, Dr Luke O’Brien, Dr. J. Scott Killeen, thanks for getting me started. To Adrian, Dec, Helen and Marco - I could not have done it without you, good luck in the future. I must point out that both Adrian and Dec are in no small measure responsible for me being able to work with purish compounds, thanks for the help lads. Marco deserves an extra mention (if only for his hair’s chameleon properties), thanks for challenging my thoughts and interpretations not just in chemistry. Thanks to Gillian Whitaker for helping me (doing the donkey work) on the osmium monomers. Also thanks to Carl and Jennifer, who have managed to stay friends with me for SEVEN years, that’s staying power. Oh, and thanks Noel for the CHN’s and for proving chemistry can be amusing, and Clare (where’s my paper) Brennan for making purple the new orange! My closest (non-chemistry) friends, in no particular order, Aine Connolly, Lorraine O’Reilly, Alan Pearson, Ed Walsh, Jupe Van den Broeke (technically your chemistry but I’ve never seen you do anything so the jury is still out), Tom Roberts, Fenton Ewing, Gareth Wynne.