title: Determination of the relative ligand-binding strengths in heteroleptic Ir(III)  complexes by ESI-Q-TOF tandem mass spectrometry.
abstract: An electrospray ionization quadrupole time-of-flight mass spectrometer has been utilized to investigate the relative ligand-binding strengths in a series of heteroleptic-charged iridium(III) complexes of the general formula [(C^N)(2) Ir(III) (S-tpy)](PF(6) ) by using variable collision energies. Collision-induced dissociation experiments were performed in order to study the stability of the Ir(III) 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 Ir(III) centers.
authors.affiliation: Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich-Schiller-University Jena, Humboldtstr. 10, 07743, Jena, Germany.
authors.forename: Esra
authors.initials: E
authors.lastname: Altuntaş
authors.forename: Andreas
authors.initials: A
authors.lastname: Winter
authors.forename: Anja
authors.initials: A
authors.lastname: Baumgaertel
authors.forename: Renzo M
authors.initials: RM
authors.lastname: Paulus
authors.forename: Christoph
authors.initials: C
authors.lastname: Ulbricht
authors.forename: Anna C
authors.initials: AC
authors.lastname: Crecelius
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Risch
authors.forename: Ulrich S
authors.initials: US
authors.lastname: Schubert
mesh_terms: D002412:Cations / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D008024:Ligands; D011725:Pyridines / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002412:Cations; D056831:Coordination Complexes; D008024:Ligands; D011725:Pyridines; D007495:Iridium; D012238:Rhodium