Determination of the Relative Ligand Binding Strength in Heteroleptic Ir(III) Complexes by ESI-Q-TOF Tandem Mass Spectrometry

Altuntas, Esra; Winter, Andreas; Baumgärtel, Anja; Paulus, Renzo M.; Ulbricht, Christoph; Crecelius, Anna; Risch, Nikolaus; Schubert, Ulrich S.

Abstract:

An electrospray ionization quadrupole time-of-flight mass spectrometer has been utilized to investigate the relative ligandbinding strengths in a series of heteroleptic-charged iridium(III) complexes of the general formula [(C^N)2IrIII(S-tpy)](PF6) by using variable collision energies. Collision-induced dissociation experiments were performed in order to study the stability of the IrIII complexes that are, for instance, suitable phosphors in light-emitting electrochemical cells. The ratio of signal intensities belonging to the fragment and the undissociated complex depends on the collision energy applied for the tandem mass spectra (MS/MS) analysis. By defining the threshold collision energy and the point of complete complex dissociation, it is possible to estimate the relative complex stabilities depending on the nature of the coordinated ligands [i.e. type of cyclometalating ligand (C^N), substituents on the S-shaped terpyridine (S-tpy)]. The collision energy values differed as a function of the coordination sphere of the IrIII centers.

Year:

2012

Type of Publication:

Article

Journal:

Journal of Mass Spectrometry

Volume:

47

Pages:

37 - 43