1. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 The Pure Rotational Spectra of FeCN (X 6  i ) and FeNC (X 6  i ): It Had to Be There! M. A. Flory and L. M. Ziurys University of Arizona Department of Chemistry Department of Astronomy Steward Observatory

2. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 Importance of Metal Cyanides NCNC Prussian Blue Fe-NC and Fe-CN bonds Vitamin B12 Co-CN Metals bonded to CN Moiety - Found in many areas of chemistry (Biochemistry, Inorganic, Materials, etc.) Also important in Astrophysics - Most common metal carriers in interstellar gas - Tracers of nucleosynthesis - Window on dust condensation in evolved stars - MgCN, MgNC, AlNC, NaCN, KCN identified in several carbon-rich envelopes

3. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 N M C C N M C N M Alkali-earth/main group M = Ca, Mg, Al, Ga, In Transition metals M = Cr, Co, Ni, Cu, Zn Alkali metals M = Na, K Also quite interesting spectroscopically Three structures possible LINEAR CYANIDE T-SHAPED LINEAR ISOCYANIDE ScTiVCrMnFeCoNiCuZn ???CN?? Ziurys group pursuing 3d cyanides Recorded pure rotational spectra of later 3d cyanides, recently CrCN Iron analog remained elusive for over 10 years

4. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 Previous Work on FeNC/FeCN Laser Fluorescence Spectroscopy (Lie and Dagdigian, 2001) –Observed  = 7/2′ ←  ″ = 9/2 transition of FeN 12 C and FeN 13 C –Determined B  =9/2 = 4331(12) MHz –Proposed 6  ground state; same as FeF and FeCl Theoretical Calculations –deYonker et al. (2004) –Calculated B e (FeNC) = 4259 MHz; B e (FeCN) = 3708 MHz –Predict that FeNC (X 6  is more stable isomer by 0.6 kcal/mol –Hirano et al. (2006, 2007) –Calculated B e (FeNC) = 4272 MHz; B e (FeCN) = 3714 MHz –Predict that FeCN (X 6  is more stable isomer by 0.4 kcal/mol A bit confusing !!! Who is correct ??

5. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 A Sub-mm Search for FeCN/FeNC Fe(CO) 5 : 2 mTorr –(CN) 2 : Trace (< 0.1 mTorr) –Ar: 30 mTorr –AC: 150 W (lower than usual) Much cleaner spectrum than with Oven Several unsuccessful attempts using Broida-type oven with Fe + (CN) 2  puzzling, since this method worked for other 3d cyanides  But.. It had to be there ! Attempted different synthetic method VM machine with AC discharge Scanned continuously from 380-415 GHz (over 4 estimated rotational transitions)

6. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 FeCN/FeNC  = 9/2 J = 46.5 → 47.5 Many harmonically- related features Spin-orbit and Renner–Teller Due to iron precursor and cyanogen Also reproduced with HCN J = 50.5 → 51.5 FeCN/FeNC  = 9/2 J = 46.5 → 47.5 Broida oven BUT…rotational constant unexpected ~ 4085 MHz NOT 4331 MHz 4259 MHz 4272 MHz

7. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 Verify the Ground State Structure 4 isotopologues observed (  = 9/2) – 56 FeCN (92 %) – 54 FeCN (6 %) – 57 FeCN (2 %) – 56 Fe 13 CN (with H 13 CN as precursor) Fe 13 CN  = 9/2 J = 49.5→50.5 CONCLUSION: This is FeCN !

8. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 FeNC J=46.4→47.5  = 9/2 Avg. of 3 scans And FeNC (X 6  i )… WEAKER set of transitions with higher B value 10 transitions measured in range 272-419 GHz Based on relative intensity  E FeNC-FeCN ≈ 1.7 kcal/mol In MHzSub-mmLie & Dagdigian B4329.735(11)4331(12) D0.0018788(69) H6.0(14)*10 -9 rms0.020 FeNC (X 6  9/2 ) Complete Analysis awaits next graduate student…. (Robin ???)

9. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 Analysis In Progress In MHz FeCN (X 6  i ) B4085.07(69) D0.00142(12) H-0.000000013(11) A-1 887 724.275 ADAD -9.990(45) AHAH 0.0000916(39) 13 000 D -0.31(12) H 0.0000138(38)  -55 000(35 000) DD -0.65(37) DD 0.037(30) -533(60) -3.5(1.0) 0.035(30) 0.0056(24) Assigning other Spin-Orbit and Renner-Teller components 204 lines measured in 4 isotopologues 21 rotational transitions observed in range 140-500 GHz Analysis with effective case (a) Hamiltonian H eff = H Rot + H SO + H SS + H LD B FeNC (Optical) = 4331 MHz B FeNC (Theory) = 4259-4272 MHz B FeCN (Theory) = 3708-3714 MHz Current rotational constant does not agree with any previous values

10. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 Arizona’s FTMW system being used to study metal-bearing radicals Discharge Nozzle with organometallic precursors After ZnCN, move to FeCN and CrCN As a check…An FTMW Study… N = 2 – 1 ZnCN ~ 15 GHz

11. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 In Conclusion…at least thus far Grad student Mike Flory needs to finish analysis for PhD Pure rotational spectrum of FeCN has been measured in all spin components BUT…still need to complete assignment B FeCN is ~10% larger than calculations Bond lengths of FeCN determined Spectrum of FeNC (  = 9/2) recorded: work in progress FeCN is the more stable structure In pursuit of FTMW spectrum

12. 62 nd International Symposium on Molecular Spectroscopy June 18-22, 2007 And thanks to the Ziurys Group: (Soon to be, Dr.) Mike Flory Dr. Aldo Apponi Dr. Chandra Savage Dr. DeWayne Halfen Stefanie Milam Emily Tenenbaum Ming Sun Robin Pulliam The star of the show.. (…provided he finishes the analysis) NSF NASA