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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