INFRARED SPECTRA OF ANIONIC COBALT-CARBON DIOXIDE CLUSTERS B. J. Knurr & J. Mathias Weber June 19, 2014

Motivation: Prior results on transition metal-CO2 complex anions: Au and Ag form formate-like complexes involving only one CO2 ligand CO2 is partially reduced in these complexes, reduction depends strongly on solvation.  Important implications for CO2 reduction catalysis!!! B. J. Knurr & JMW, JACS 134 (2012) 18804−18808 B. J. Knurr & JMW, J. Phys. Chem. A 117 (2013) 10764–10771 Cartoon representation of a negatively charged metal catalyst supported on a thin film with liquid CO2 as a solvnet The negative charge is replenished by the metal electrode [AuCO2]-

What about other interesting transition metals?

What about other interesting transition metals? Electron configurations: Au: [Xe] (4f)14 (5d)10 (6s)1 Ag: [Kr] (4d)10 (5s)1 Cu: [Ar] (3d)10 (4s)1 Co: [Ar] (4s)2 (3d)7 Ni: [Ar] (4s)2 (3d)8 What will be the effect of a drastic change in electron configuration? Cobalt, Nickel New chemistry???

Experimental Method: IR Photodissociation cluster + h

Experimental Method: IR Photodissociation cluster + h hot cluster

Experimental Method: IR Photodissociation cluster + h hot cluster

Experimental Method: IR Photodissociation cluster + h hot cluster fragments

Experimental Setup Nd:YAG IR-OPO/OPA electron gun 600 – 4500 cm-1 0.1-10 mJ / 5 ns IR-OPO/OPA mass gate power meter ion source

Experimental Setup [M·(CO2)n]- Metal CO2 Ion source: laser vaporization & entrainment electron beam [M·(CO2)n]- Metal 355 nm Not spectators Say evaporate CO2 from the cluster CO2

IR Spectra of [Au(CO2)n]- 3 4 5 6 7 8 9 10 11 12 13 B. J. Knurr & JMW, JACS 134 (2012) 18804−18808

[Co(CO2)n]- [Co(CO2)n]- clusters charge carrier solvent [Co(CO2)n]- clusters Fragments observed only for n ≥ 3  first two CO2 units are strongly bound to the metal atom No significant change in dominant IR signatures  No change of dominant structural motif with increasing cluster size B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

[Co(CO2)n]- [Co(CO2)n]- clusters – Structures B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

[Co(CO2)n]- [Co(CO2)n]- clusters – Structures Exp., n= 3 Lowest energy (insertion) structure is not the dominant motif. “Butterfly” structures give best fit to experimental spectrum. B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

[Co(CO2)n]- [Co(CO2)n]- clusters – Structures Exp., n=4 Lowest energy (insertion) structure is not the dominant motif. “Butterfly” structures give best fit to experimental spectrum. Calculated spectra corroborate robustness w.r. to solvation. Calculated partial charges: Co  +1; CO2  -1 B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

d-orbitals in isolated metal atom d-block in octahedral complex t2g eg Interactions of the d-block in octahedral transition metal complexes (Oh) d-orbitals in isolated metal atom d-block in octahedral complex t2g eg From: Yves Jean “Molecular Orbitals of Transition Metal Complexes”

Interactions of the d-block in transition metal complexes Square-planar complexes (D4h) eg 3a1 b2 b2 a2 1a1 t2g

[Co(CO2)n]- 3a1 b2 a2 1a1 2a1 B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

[Co(CO2)n]- B. J. Knurr & JMW, J. Phys. Chem. A (2014), in press

Conclusions Co complexes with CO2 show bidentate metal-ligand interactions with M-C and M-O bonds Electronic structure: monovalent metal cation bound to anionic CO2 ligands

Alfred P. Sloan Research Fellowship Dramatis Personae NSF AMO PFC Alfred P. Sloan Research Fellowship NSF CAREER Award

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