Spin Changes Accompany Ultrafast Structural Interconversion in the Ground State of a Cobalt Nitrosyl Complex. Issue 44 (22nd September 2017)

• Record Type: Journal Article
• Authors: Marroux, Hugo J. B.; Curchod, Basile F. E.; Faradji, Charly A.; Shuttleworth, Timothy A.; Sparkes, Hazel A.; Pringle, Paul G.; Orr‐Ewing, Andrew J.
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 44(2017)
• Page Start: 13713
• Page End: 13716
• Publication Date: 2017-09-22
• Subjects: 2D infrared spectroscopy -- electron spin -- intersystem crossing -- nitrosyl ligand -- ultrafast dynamics; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201707508
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Ultrafast, reversible intersystem crossing (ISC) is reported under ambient conditions for the electronic ground state of the pentacoordinate cobalt nitrosyl complexes, [CoX2 (NO)(PMePh2 )2 ] (X=Cl, Br), in solution. ISCs on such short timescales are more typically observed in electronically excited states reached by absorption of ultraviolet or visible light. Singlet and triplet electron spin states of the complex, corresponding to two different isomers, are populated at room temperature, and the two isomers exchange on a timescale of a few picoseconds. Ultrafast two‐dimensional infrared spectroscopy observes the change in wavenumber of the NO ligand band accompanying the isomerization and associated ISC on the (spin) adiabatic ground potential energy surface. Comparison of the dynamics of the chloro‐ and bromo‐complexes shows that inertial effects of the ligand motion have a greater effect than spin–orbit coupling on determining the forward and reverse isomerization and ISC rates. Abstract : The ground state intersystem crossing of a cobalt nitrosyl complex is shown to occur on an ultrafast time scale. The electron spin changing dynamics can be observed with 2DIR spectroscopy by probing the nuclear vibrational frequencies associated with each electronic state. Comparison of the spin‐state exchange rates in two halido‐substituted complexes shows that inertial effects outweigh ligand spin–orbit coupling effects.