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

2. 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]-

3. What about other interesting transition metals?

4. 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???

5. Experimental Method: IR Photodissociation
cluster + h

6. Experimental Method: IR Photodissociation
cluster + h
hot cluster

7. Experimental Method: IR Photodissociation
cluster + h
hot cluster

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

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

10. 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

11. 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

12. [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

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

14. [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

15. [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

16. 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”

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

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

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

20. 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

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

22. Thank you for your attention