OSU – June – SGK1 STEVE KUKOLICH, ERIK MITCHELL ╬, SPENCER CAREY, MING SUN, AND BRYAN SARGUS, Dept. of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona MICROWAVE STRUCTURE FOR THE PROPIOLIC ACID – FORMIC ACID COMPLEX † ╬ Present address: Patrick Air Force Base, 32925, United States † This material is based on work supported by the National Science Foundation under Grant Nos. CHE , CHE and CHE

OSU – June – SGK2  HYDROGEN-BONDED STRUCTURES ARE NOT STATIC ADAM DALY   CONCERTED PROTON TUNNELING Microwave measurements of proton tunneling and structural parameters for the propiolic acid – formic acid dimer 1 (2011) 1.Adam M. Daly, Kevin O. Douglass, Laszlo C. Sarkozy, Justin L. Neill, Matt T. Muckle, Daniel P. Zaleski, Brooks H. Pate and Stephen G. Kukolich, J Chem. Phys., 135(15), / /12 (2011)

OSU – June – SGK3  PROTON TUNNELING Observed transitions were split into doublets > concerted proton tuneling The small splittings of 1 to 1.5 MHz for the a-dipole transitions are due to the differences in rotational constants for the upper and lower tunneling states. The b-dipole transitions are combination transitions with change in rotational state and tunneling state and provide direct information on the tunneling splittings.

OSU – June – SGK4 PREVIOUS RESULTS FOR THE PROPIOLIC ACID – FORMIC ACID DIMER  C.O.M. SEPARATION > WELL DETERMINED, BUT, RELATIVE ORIENTATIONS OF THE MONOMERS, NOT WELL DETERMINED.  TUNNELING FREQUENCY FOR HCCCOOD···DOOCH BASED ON FEW MEASUREMENTS. HOW TO FIX THIS?  MEASURE MORE ISOTOPOLOGUES! (BOB KUCZKOWSKI RECOMMENDATION)  NEW MEASUREMENTS DCCCOOH···HOOCH and HCCCOOD···DOOCH isotopologues, measured in the GHz range  IMPROVED STRUCTURE and OD···DO TUNNELING FREQUENCY

OSU – June – SGK5 SUMMARY OF RESULTS Hydrogen bond lengths are r(O1-H1··O4) of 1.64 Å and r(O3-H2··O2) 1.87 Å. Average of hydrogen bond lengths is r av (exp) = 1.76 Å, in good agreement with r av (theory) = 1.72 Å. The experimental structure exhibits a greater asymmetry for the two hydrogen bond lengths than was obtained from the ab initio mp2 calculations Tunneling frequency for HCCCOOD···DOOCH is  = 3.48 MHz (compared with  = MHz for OH ···HO)

OSU – June – SGK6  Experimental A new coaxial-beam FTMW spectrometer with multiple FID data acquisition completed by Ming Sun provided good resolution and sensitivity. Propiolic acid-CD (DCCCOOH) was prepared in 32-54% yield by the decarboxylation of acetylenedicarboxylic acid monopotassium salt in D 2 O, by Spencer Carey 7 a-dipole transitions measured for DCCCOOH···HOOCH (lower tunneling state only) A = 5994., B = , C = MHz Propiolic acid-OD samples were prepared using both simple hydrogen exchange with methanol(OD) (99.5%), and by making sodium propiolate using NaOH in methanol, and adding D 2 SO transitions measured for HCCCOOD···DOOCH (a and b-dipole)

OSU – June – SGK7 The J ka, kc = 4 1,4 → 3 0,3 b-type doublet of the ProOD- FAOD. The b-dipole ro-vibrational transitions are weak, 5000 pulses, 10 FID’s each pulse.

OSU – June – SGK8

9  Determining the COM separation of the monomers is easy The formula is: I CC = I CC (Pro) + I CC (FA) +  R 2 CM.

OSU – June – SGK10  Determining the RELATIVE ORIENTATION of the monomers is not so easy. 1)Fix the monomer structures using best parameters available. 2)Assume PLANAR structure (  = 1.33 amu Å 2 ) 3)Fix the origin of X CM, Y CM coordinate system at COM of PROPIOLIC 4)Adjust the location (X CM, Y CM ) and orientation  FA of FORMIC to fit B and C rotational constants

OSU – June – SGK11  HCOOH 1 and HCCCOOH 2 structures fixed at monomer values  ISOTOPOLOGUES > HCCCOOHHOOCH, HCCCOOHDOOCH, HCCCOODHOOCH, HCCCOOHHOO 13 CH, HCCCOOHHOOCD 3,  HCCCOODDOOCH, DCCCOOHHOOCH (new)  Experimental B and C for 7 isotopologues fit with   = 0.7 MHz  The best-fit hydrogen bond lengths are r(O1-H1··O4) = 1.64 Å and r(O3-H2··O2) =1.87 Å.  Average (O-H) is r av (exp) = 1.76 Å, in good agreement with r av (theory) = 1.72 Å. Center of mass separation of monomers is R CM = Å. _______________________________ 1. Davis, R. W.; Robiette, A. G.; Gerry, M. C. L.; Bjarnov, E.; Winnewisser, G. J. Mol. Spec. 1980, 81, Lister, D. G.; Tyler, J. K. Spectochimica Acta 1972, 28A, Daly, A. M.; Douglass, K. O.; Sarkozy, L. C.; Neill, J. L.; Muckle, M. T.; Zaleski, D. P.; Pate, B. H.; Kukolich, S. G. J. Chem.Phys. 2011, 135, / /12

OSU – June – SGK12 Most significant difference is ASYMMETRY OF H-BOND LENGTHS Do the O-H bond lengths change on complex formation?

OSU – June – SGK13 Key Structural Parameters :

OSU – June – SGK14 Acknowledgements N$F - This material is based upon work supported by the National Science Foundation under Grant Nos. CHE , CHE and CHE This support from the National Science Foundation is gratefully acknowledged Adam Daly (UA – JPL); Yimin Wang and Joel Bowman (Emory U.) Department of Chemistry, University of Arizona. Earlier work > Phil Bunker – NRC, > Kevin Douglas, Brooks Pate – U. Virginia

OSU – June – SGK15

OSU – June – SGK16 ISOTOPOLOGUES > HCCCOOHHOOCH, HCCCOOHDOOCH, HCCCOODHOOCH, HCCCOOHHOO 13 CH, HCCCOOHHOOCD †, HCCCOODDOOCH, DCCCOOHHOOCH (new) The best-fit hydrogen bond lengths are r(O1-H1··O4) = 1.64 Å and r(O3-H2··O2) =1.87 Å. Average is r av (exp) = 1.76 Å, in good agreement with r av (theory) = 1.72 Å. Center of mass separation of monomers is R CM = Å. † Daly, A. M.; Douglass, K. O.; Sarkozy, L. C.; Neill, J. L.; Muckle, M. T.; Zaleski, D. P.; Pate, B. H.; Kukolich, S. G. J. Chem.Phys. 2011, 135, / /12

OSU – June – SGK17