1. OSU – June – 2010 - SGK1 ADAM DALY, STEVE KUKOLICH, Dept. of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721. CHAKREE TANJAROON, Dept. of Chemistry and Physics, Arkansas State University, Jonesboro, AR 72467 ADAM J. V. MARWITZ and SHIH-YUAN LIU Department of Chemistry, University of Oregon, Eugene, OR 97403 MICROWAVE SPECTRUM, STRUCTURAL PARAMETERS AND QUADRUPOLE COUPLING FOR AZABORINE AND 1-ETHYL-AZABORINE † † This material is based on work supported by the National Science Foundation under Grant No. CHE-0809053. Partial funding from the U.S. Department of Energy (S.Y.L., DE-FG36-08GO18143), and the National Science Foundation (A.J.V.M., DGE-0549503) U - OREGON

2. OSU – June – 2010 - SGK2 A Hybrid Organic/Inorganic Benzene Michael Faraday Friedrich August Kekulé Alfred Stock

3. OSU – June – 2010 - SGK3  BENZENE, is the quintessential aromatic molecule  How aromatic is AZABORINE? A)PLANAR MOLECULE  0 = 0.02 amu  Å 2 B)PARTIAL CANCELLATION OF B-N POLARIZATION, BUT  = 2.0D C)eqQ’s CONSISTENT WITH PARTIAL DELOCALIZATION of  ELECTRONS 1,2-dihydro-1,2-azaborine

4. OSU – June – 2010 - SGK4 Some hyperfine components of the 1 01 -0 00 transition at 8099. The stimulation frequency is 8098.770 MHz, and frequencies are relative to the stimulation frequency with A measured to be 8097.959, B at 8098.073, and C at 8098.172 MHz. THERE ARE 10 BLENDED TRANSITIONS UNDER PEAKS A, B, and C.

5. OSU – June – 2010 - SGK5 Synthesis of 1,2-Dihydro-1,2-azaborine † Adam Marwitz † Angew. Chem. Int. Ed. 2009, 48, 973-7. TBS - tetrabromobenzotriazole

6. Phys. Chem. Oct. 17, 056  EXPERIMENTAL Flygare-Balle Spectrometer – Homodyne Detection, – AZABORINE sample in dodecane solution, maintained at 0º C. Measurements 7-15 GHz. Three isotopomers, H 6 C 4 11 B 14 N, H 6 C 4 10 B 14 N, and H 5 DC 4 11 B 14 N CH 3 OD was added to the dodecane solution for N-D isotopomer.

7. OSU – June – 2010 - SGK7 Spectroscopic constants for1,2-dihydro-1,2-Azaborine. Values in MHz. The ground state inertia defect (  = I cc - I aa –I bb ) is  0 = 0.02 amu  Å 2 for H 6 B 11 N 14 C 4. CALC. – Gaussian MP2/6-311+G(d,p) H 6 11 B 14 NC 4 H 6 10 B 14 NC 4 H 5 10 BD 14 NC 4 CALC. A5657.335(1)5794.049(3)5642.9575633.597 B5349.2807(5)5352.383(1)5059.2585344.391 C2749.1281(4)2781.7927(6)2669.6752742.593  aa -1.71(1)-3.42(2)--1.6  bb -1.33(2)-1.83(5)--1.4  cc 3.03(2)5.26(3)-3.0  aa 0.46(1)0.43(1)-0.47  bb 0.78(6)0.79(3)-0.57  cc -1.25(6)-1.22(3)-   (kHz) 8(139)17(73)--

8. OSU – June – 2010 - SGK8 Structural parameters from the least squares fit. Listed error limits are 2 . Param.MicrowaveCALC r(B-N)1.45(3) Å 1.437 Å r(B-C)1.51(1) Å 1.516 Å r(N-C)1.37(3) Å 1.368 Å  119˚ 119.1˚  115(3)˚ 114.5˚  123(3)˚ 124.1˚  120˚ 120.4˚  0.9 MHz - MoleculeR(B-N)/ Å H 2 NBH 2 1.391(2) a H 3 NBF 3 1.59 b BH 3 NH 3 1.6576(16) c HCN-BF 3 * 1.60(2) d

9. OSU – June – 2010 - SGK9 Electron density maps for the MP2 optimized structures of 1,2-dihydro-1,2- azaborine and benzene mapped with the electrostatic potential (Iso Val = 0.001) from the total SCF density. Red is most negative (electron rich) and blue is most positive. In the top, right, B atom is pink, N atom blue(darker). Azaborine Benzene

10. Phys. Chem. Oct. 17, 0510  N-Et-1,2-azaborine Measurements 5-13 GHz (214 lines) More stable than 1,2-Dihydro-1,2-azaborine PG (trans) PE (cis) (1120 cm -1 )

11. OSU – June – 2010 - SGK11 J = 3 03  2 02 rotational transition for ethyl-azaborine illustrating the compex nuclear quadrupole hyperfine splittings.

12. OSU – June – 2010 - SGK12 Experimental and calculated spectroscopic constants for Ethyl-azaborine (PG conformer). MicrowaveMP2/6- 311++G(d,p) A /MHz4477.9874(43)4460.2800 B /MHz1490.50833(71)1495.3686 C /MHz1230.67282(63)1233.2265  J /kHz 0.135(15)- 11 B  aa /MHz -1.819(13)-1.706 11 B (  bb -  cc ) /MHz -3.3980(37)-3.630 14 N  aa /MHz 1.254(12)1.094 14 N(  bb -  cc ) /MHz 0.6624(40)0.6676 Number of lines214-  (fit) /kHz 10-

13. OSU – June – 2010 - SGK13  Azaborine Calculated(MP2) p c orbital occ. Atomic Charge q (other q(H) =0.2) For Benzene pc = 1.09 (all C-atoms)

14. experimental to H to C to B p z n pz 1.001.201.401.501.602.001.631.58 g1g1 nHnH 0.911.111.311.411.511.911.28 g 2 +g 3 n C + n B 1.762.162.562.762.963.762.52 n total about N 3.674.475.275.676.077.675.85.38 Again, two equations and three unknowns. There is no way to distinguish between populations of the sp 2 orbital to C and to B without  xy. Setting n pz And calculating the other populations we obtain: The two blue columns are the most reasonable (charge on N -0.27 or -0.67). We get: n pz = 1.6 from MP2/6-311+G(d,p) NBO calculation. MP2 – STO3G

15. OSU – June – 2010 - SGK15 Acknowledgements N$F - This material is based upon work supported by the National Science Foundation under Grant No. CHE-0809053. Partial funding from the U.S. Department of Energy (S.Y.L., DE- FG36-08GO18143), and the National Science Foundation (A.J.V.M., DGE-0549503) We thank Laszlo Sarkozy for a spectral analyzer program that greatly aided the assignments. Stew Novick provided many helpful comments and the extended Townes-Dailey (hybrid-orbital) analysis. U - OREGON

16. OSU – June – 2010 - SGK16

17. OSU – June – 2010 - SGK17 Structural fit parameters Param.MicrowaveCALC r(B-N)1.45(3) Å 1.437 Å r(B-C)1.51(1) Å 1.516 Å r(N-C)1.37(3) Å 1.368 Å  119˚ 119.1˚  115(3)˚ 114.5˚  123(3)˚ 124.1˚  120˚ 120.4˚  0.9 MHz - C 4 H 4 FRAGMENT Geometry fixed at Calculated values

18. OSU – June – 2010 - SGK18 PG (energy minimum)PE (transition state) A e /MHz4494.9454495.357 B e /MHz1472.8031464.933 C e /MHz1217.8531210.790 A o /MHz4465.4974466.840 B o /MHz1460.7121452.405 C o /MHz1207.4761200.089 B - C255254 Conformer E. /cm -1 0.01120

19. OSU – June – 2010 - SGK19 1,2-dihydro-1,2-azaborine  BENZENE, is the quintessential aromatic molecule  How aromatic is AZABORINE? A)PLANAR MOLECULE  0 = 0.02 amu  Å 2 + B) ELECTRONIC STRUCTURE C) MOLECULAR STRUCTURE