1. FTIR AND DFT STUDIES OF THE MgC 3 - ANION IN SOLID Ar M. Bejjani, C. M. L. Rittby, and W. R. M. Graham Department of Physics and Astronomy Texas Christian University Fort Worth, TX 76129 66 th International Symposium on Molecular Spectroscopy The Ohio State University June 20-24, 2011 1

2. Objectives  Synthesize small novel metal carbide molecules  Determine the vibrational fundamentals and molecular structure based on the infrared spectrum of the molecule  13 C isotopic shift measurements  Density Functional Theory (DFT) 2 Motivation  Application to astrophysics  Application to materials science (e.g. metcars)

3. Astrophysics 2 atoms3 atoms4 atoms5 atoms6 atoms7 atoms8 atoms9 atoms H2H2 C3C3 c-C 3 HC5C5 C5HC5HC6HC6HCH 3 C 3 NCH 3 C 4 H AlFC2HC2Hl-C 3 HC4HC4Hl-H 2 C 4 CH 2 CHCNHCOOCH 3 CH 3 CH 2 CN AlClC2OC2OC3NC3NC 4 SiC2H4C2H4 CH 3 C 2 HCH 3 COOH(CH 3 ) 2 O CN - C2SC2SC3OC3Ol-C 3 H 2 CH 3 CNHC 5 NC7HC7HCH 3 CH 2 OH C2C2 CH 2 C3SC3Sc-C 3 H 2 CH 3 NCCH 3 CHOH2C6H2C6 HC 7 N CH, CH + HCNC2H2C2H2 H 2 CCNCH 3 OHCH 3 NH 2 CH 2 OHCHOC8HC8H CNHCO, HCO + NH 3 CH 4 CH 3 SHc-C 2 H 4 Ol-HC 6 H ?CH 3 C(O)NH 2 CO, CO + HCS + HCCNHC 3 NHC 3 NH + H 2 CCHOHCH 2 CHCHO ?C8H–C8H– CPHOC + HCNH + HC 2 NCHC 2 CHOC6H–C6H– CH 2 CCHCNC3H6C3H6 SiCH 2 O, H 2 O + HNCOHCOOHNH 2 CHOH 2 NCH 2 CN HClH2SH2SHNCSH 2 CNHC5NC5N KClHNCHOCO + H2C2OH2C2Ol-HC 4 H ? NHHNOH 2 COH 2 NCNl-HC 4 N NOMgCNH 2 CNHNC 3 c-H 2 C 3 O NSMgNCH 2 CSSiH 4 H 2 CCNH ? NaClN2H+N2H+ H3O+H3O+ H 2 COH + C5N–C5N– OHN2ON2Oc-SiC 3 C4H–C4H– PNNaCNCH 3 HC(O)CN SO, SO + OCSHOCN SiNSO 2 HSCN SiOc-SiC 2 C3N–C3N– CH 3 C 5 NHC 9 NC 6 H 6 ?HC 11 N SiSCO 2 PH 3 ?(CH 3 ) 2 COCH 3 C 6 HC 2 H 5 OCH 3 ?C 60 CSNH 2 HCNO(CH 2 OH) 2 C 2 H 5 OCHOn-C 3 H 7 CNC 70 HFH3+H3+ CH 3 CH 2 CHO SH + H2D+H2D+ HDHD 2 + FeO ?SiCN O 2 ?AlNC CF + SiNC SiH ?HCP POCCP AlOAlOH OH + KCN H 2 Cl + 10 atoms11 atoms12 atoms> 12 atoms Source: Cologne Database for Molecular Spectroscopy, April 2011. 3

4. Materials science  Small metal-carbide molecules may help in understanding the bonding and the growth mechanism of larger clusters such as metallocarbohedrenes (metcars).  Large MC 2 production indicates MC 2 may serve as a fundamental building block of larger metcar clusters (M 8 C 12 ). M C C 4

5. Previous work on MgC n clusters (n>2)  No experimental observations of any MgC n clusters have so far been reported.  Theoretical studies (Largo et al., 2001 and 2003)  MgC n (n=2-7)  n-even: cyclic isomers preferred  n-odd: chain preferred  MgC n +, MgC n - (n=2-7)  Chains except for MgC 2 +, MgC 2 - and MgC 3 + 5

6. 2 A 1 rhombic C1C1 C3C3 Mg C2C2 1.5 2.2 1.3 2 Σ linear Mg C1C1 C2C2 C3C3 2.11.3 MgC 3 + cation MgC 3 neutral, anion and cation (Largo et al.) C3C3 C2C2 C1C1 Mg 2 A'' bent 2.2 141.8° 174.8° 1.3 2.0 Mg C1C1 C2C2 C3C3 4 Σ linear C1C1 C3C3 Mg C2C2 1.5 2.2 1.3 2 A 1 rhombic 2.3 MgC2C2 C3C3 C1C1 2.1 1.3 4 B 1 fan MgC 3 - anion 1.3 6 3 Π linear Mg C1C1 C2C2 C3C3 2.11.3 3 A 1 rhombic C1C1 C3C3 Mg C2C2 1.5 2.2 1.3 C3C3 C2C2 C1C1 170.8° Mg 1 A' bent 2.2 1.3 120.0° C1C1 C3C3 Mg C2C2 1 A 1 rhombic 2.21.3 1.7 3 B 2 fan 1.3 MgC2C2 C3C3 C1C1 2.4 2.3 3 B 2 ring 1.3 1.5 1.4 MgC1C1 C2C2 C3C3 2.1 124.6° MgC 3 neutral

7. Nd-YAG 1064 nm pulsed laser Quartz window Laser focusing lens Ar To pump 10 -7 Torr or < CsI window To pump 10 -3 Torr Carbon rod Magnesium rod Gold mirror ~ 12 K Bomem DA3.16 Fourier Transform Spectrometer KBr beam splitter liquid N 2 cooled MCT detector (500 - 5000 cm -1 ) 0.2 cm -1 resolution Experimental apparatus 7

8. Candidates for Mg n C m bands C n ? ● C6C6 ●● 1730 1740 1750 1760 1770 1780 1790 1800 (a) 12 C rod (b) 12 C rod + Mg rod Absorbance Mg n C m ? C7-C7- 1188 1198 ● ● ● ● Frequency (cm -1 ) ● 1797.5 1190.1 8

9. SpeciesB3LYP/6-311+G(d) MgC 3 ( 3 Π) 109.1 (1.8), 121.3 (0.3), 350.0 (2.9), 409.9 (98.6), 456.3 (10.0), 1242.4 (135.7), 1893.6 (101.0) MgC 3 ( 1 A′) 126.3 (3.4), 211.5 (5.3), 303.3 (6.5), 432.1 (30.0), 1222.7 (27.7), 1974.3 (764.6) MgC 3 + ( 2 Σ) 119.6 (16.2), 169.1 (0.0), 291.3 (24.8), 368.9 (50.4), 1235.2 (14.8), 2074.4 (827.8) MgC 3 - ( 2 A′′) 102.6 (8.5), 282.0 (63.4), 383.4 (22.6), 388.2 (16.1), 1204.9 (217.4), 1748.7 (922.9) MgC 3 - ( 4 Σ) 143.2 (0.2), 470.0 (43.7), 474.6 (27.4), 1260.64 (0.7), 1735.9 (20.2) DFT calculations: vibrational frequencies (cm -1 ) and intensities (km/mol) for open-chain MgC 3 species Experimental1190.1, 1797.5 cm -1

10. Effects of 20% 13 C isotopic substitution 1728.2 1736.8 1745.6 1753.6 1773.2 1781.6 1789.8 13-13-13 13-13-12 12-13-13 13-12-13 12-13-12 13-12-12 12-12-13 x CnCn x x x x 1797.5 (b) 22 K Absorbance 11861196 Frequency (cm -1 ) 1730 1740 1750 1760 1770 1780 1790 1800 (a) 12 K 1190.1 x x x x Mg n 12 C m ? 10

11. MgC 3 ( 3 Π)MgC 3 - ( 2 A′′)MgC 3 - ( 4 Σ) Isotopomer Mg-C-C-C Observed ν Scaled ν Difference Δ ν Scaled ν Difference Δ ν Scaled ν Difference Δν Mg-12-12-121797.5……………… Mg-13-12-121781.61775.66.01784.5-2.91781.50.1 Mg-12-12-131789.81793.1-3.31787.821789.10.7 Mg-13-12-131773.21770.62.61774.0-0.81772.11.1 Mg-12-13-121753.61754.7-1.11750.931753.00.6 Mg-12-13-131745.61750.4-4.81741.14.51744.80.8 Mg-13-13-121736.81731.75.11737.6-1.81736.30.5 Mg-13-13-131728.21726.81.41726.81.41726.81.4 Observed vs theoretical 13 C isotopic shifts 11 Std deviation= 4.1Std deviation= 2.7Std deviation= 0.4

12.  Linear MgC 3 - anion has been observed in its 4 Σ ground state.  Its ν 1 (σ) vibrational fundamental is identified at 1797.5 cm -1.  The 1190.1 cm -1 band may be the ν 2 (σ) mode. Mg Conclusions 12 Frequency (cm -1 ) 12-13-12 13-12-12 12-12-13 11861196 1730 1740 1750 1760 1770 1780 1790 1800 1728.2 1736.8 1745.6 1753.6 1773.2 1781.6 1789.8 13-13-13 13-13-12 12-13-13 13-12-13 x x x x 1797.5 1190.1 x x x x Absorbance MgC 3 - ( 4 Σ) 1260.64 (0.7), 1735.9 (20.2)

13. 13 Acknowledgments  The Welch Foundation  TCU Research and Creative Activities Fund  The Graduate Student Travel Grant Program  W. M. Keck Foundation for the Bomem spectrometer

14. 14 References 1 P. Redondo, C. Barrientos, and A. Largo, Chemical Physics Letters 335, 64 (2001). 2 P. Redondo, C. Barrientos, A. Climas, and A. Largo, J. Phys. Chem. A 107, 4676 (2003). 3 P. Redondo, C. Barrientos, A. Climas, and A. Largo, J. Phys. Chem. A 107, 6317 (2003).