University of Otago, New Zealand

Chemistry

Te Tari Hua-Ruanuku

Greg Huff

contact photo
Greg Huff
Supervisor: Professor Keith C. Gordon
Tel: (03) 479 7930
Location: Science II, 5c9a
greg.huff@otago.ac.nz


Photophysical properties of metal complexes with close-lying ILCT and MLCT states.

Project Summary

There have been many attempts to develop transition metal complexes based on N719 and “black dye” with both superior efficiency and broader visible absorption.  Many of these dyes have utilized organic donor groups attached to the ligands which give rise to intraligand charge transfer (ILCT) excited states in addition to the usual MLCT excited states of Ruthenium complexes.  However there have been very few theoretical and spectroscopic analyses of this type of transition metal complex.

We have studied a series of complexes based on the pyridyl-1,2,3-triazole ligand (pytri) which have MLCT excited states.   The metal centers used are Re(CO)3Br, PtCl2, Pt(CCPh)2 and Ru(bpy)22+  These complexes are similar to well-known bipyridine-based systems.  Appending a triphenylamine (TPA) electron donor to the pyridine ring gives a ligand termed TPA-pytri.  These complexes have vastly improved visible light absorption properties compared to those lacking the TPA substituent.

Resonance Raman spectroscopy and TD-DFT calculations show that the new absorption band is due to an ILCT transition.  The excited state lifetimes and emission quantum yields for the Re(I) and Pt(II) complexes show significant changes from those of the unsubstituted complexes.  Thus the thermally equilibrated excited state (THEXI) appears to switch to ILCT as well.  For the Ru(II) complex the ILCT lies at higher energy than the MLCT state and there is little change in the photophysical properties.