NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 1 Effects of Hydrogen Bonding on the Ring Stretching Modes of Pyridine and Pyridinium Darin J. Ulness Department of Chemistry Concordia College Moorhead, MN

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 2 Outline I.Introduction II. Experiment Coherent Raman Scattering III. Hydrogen Bonding Pyridine systems Simple model IV. Prospectus

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 3 Spectroscopy Using light to gain information about matter Transition frequencies Dephasing rate constants Susceptibilities InformationUses of information In Chemistry In Biology In Engineering

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 4 Nonlinear Optics P=  E Signal Material Light field Perturbation series approximation P(t) = P (1) + P (2) + P (3) … P (1) =  (1) E, P (2) =  (2) EE, P (3) =  (3) EEE

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 5 CARS Coherent Anti-Stokes Raman Scattering RR 11 11 22  CARS  1 -  2 =  R  CARS =  1 +  R

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 6 CARS with Noisy Light I (2) CARS We need twin noisy beams B and B’. We also need a narrowband beam, M. The frequency of B (B’) and M differ by roughly the Raman frequency of the sample. The I (2) CARS signal has a frequency that is anti-Stokes shifted from that of the noisy beams. B B’ M I (2) CARS

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 7 I (2) CARS: Experiment Monochromator Narrowband Source Broadband Source (noisy light) Lens Sample Interferometer  B B’ M I (2) CARS Computer CCD

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 8 I (2) CARS: Spectrogram Monochromator Narrowband Source Broadband Source Lens Sample Interferometer  B B’ M I (2) CARS Computer CCD Signal is dispersed onto the CCD Entire Spectrum is taken at each delay 2D data set: the Spectrogram

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 9 I (2) CARS: Spectrogram Pixel A A Pixel B B Pixel C C Dark regions: high intensity Light regions: low intensity Oscillations: downconversion of Raman frequency. Decay: Lineshape function

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 10 I (2) CARS: Data Processing Fourier Transformation X -Marginal

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 11 Hydrogen Bonding Interaction between a hydrogen atom and oxygen or nitrogen (or fluorine) A very weak chemical interaction (bond) A very strong physical interaction Exploited extensively in biological systems O, N H

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 12 Pyridine Systems Why Pyridine Simple molecule Important component in many compounds Biological importance Strong I (2) CARS signal H-bond acceptor but not a H-bond donor. N C C C C C H H H H H

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 13 Pyridine: Normal Modes A1A1 Ring Breathing A1A1 Triangle

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 14 Pyridine and H-bonding Neat Pyridine Two peaks With H-bond Three peaks

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 15 Pyridine and H-bonding Key Results Some pyridine is free some is hydrogen bonded Hydrogen bonding blue- shifts the ring breathing mode Hydrogen bonding does not shift the triangle mode

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 16 Pyridine: Inner Tube Model Molecular orbitals Electrostatics Compare with benzene Stabilization through  delocalization H-bonding makes pyridine more “benzene- like”

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 17 Pyridine: Inner Tube Model Electron density for Benzene = + Electron density for free pyridine Electron density for H-bonded pyridine = + Full e - density  e - density sp 2 e - density Full e - density  e - density sp 2 e - density ≈

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 18 Pyridine: Test of Model Vary the strength of hydrogen bonding Formamide N-H-N bond ~ 3-4 Kcal/mol Water N-H-O bond ~ 6-7 Kcal/mol Acetic Acid Proton transfer (acid/base) Normalized X marginal intensity Raman wavenumber / cm Formamide Water Acetic Acid 4 cm -1 8 cm cm -1

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 19 Pyridine: Peak Broadening

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 20 Peak Broadening Models Network model Thermalized distribution model Etc. Fileti, E.E.; Countinho, K.; Malaspina, T.; Canuto, S. Phys. Rev. E. 2003, 67,

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 21 Pyridine/water Temperature T = -40 O C T = -20 O C T = 0 O C T = 20 O C T = 40 O C T = 60 O C Normalized X marginal intensity Raman wavenumber / cm Xpy = 0.55

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 22 Pyridine/water Temperature Xpy = Peak width (obs) / cm Temperature / O C Hydrogen Bonded Ring Breathing Mode “Free” Pyridine Ring Breathing Mode Triangle Mode

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 23 Pyridine/water Temperature Xpy = 0.55

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 24 Pyridine/Acetic Acid Xpy = 0.3 Xpy = 0.2 Xpy = 0.8 Xpy = 0.7 Xpy = 0.6 Xpy = 0.5 Xpy = 0.4 Xpy = 0.9 Xpy = 1.0 Normalized X marginal Intensity Raman wavenumber / cm Proton transfer (acid/base reaction)

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 25 Pyridine/Acetic Acid Xpy = 0.05 Xpy = 0.25 Xpy = 0.20 Xpy = 0.15 Xpy = 0.10 Xpy = 0.30 Normalized X marginal intensity Raman Wavenumber / cm

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 26 Pyridinium-carboxylate Acetic acid, pKa = 4.77 Trichloroacetic acid, pKa = 0.70 Difluoroacetic acid, pKa = 1.34 Trifluoroacetic acid, pKa = 0.23 “Electronic” (pKa) study

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 27 Pyridinium-carboxylate Predictions from the inner-tube model Stronger Acid (low pKa) Weaker conjugate base Weaker ion complex Less “pullback” on the hydrogen Stronger N-H bond Better delocalization Larger blue shift of the ring breathing mode

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 28 Pyridinium-Trifluoroacetate

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 29 Pyridinium-carboxylate Acetic acid cm -1 Trichloroacetic acid cm -1 Difluoroacetic acid cm -1 Trifluoroacetic acid cm -1 AcidpKaShift Freely solvated pyridinium28 cm -1

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 30 Prospectus Summary: Noisy light provides an alternative method for probing ultrafast dynamics of the condensed phase. Useful tool for probing hydrogen bonding using “test” molecules. Simple model useful in understanding hydrogen bonding in pyridine. Thermalized distribution is likely cause of peak broadening.

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 31 Prospectus Future of noisy light at Concordia: Other pyridine based molecules Hydroxymethyl pyridine. Halo pyridines. Other nitrogen heterocycles. A principle goal is to develop an I (2) CARS based microscopy.

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 32 Acknowledgements Former Students Jahan Dawlaty: Cornell University, Ph.D. candidate in optical electronics Dan Biebighauser: Vanderbilt University, Ph.D. in mathematics John Gregiore: Cornell University, Ph.D. candidate in physics Duffy Turner: MIT, Ph.D. candidate in physical chemistry Pye Phyo Aung: John’s Hopkins University, Ph.D. candidate in mathematics Tanner Schulz: University of Minnesota, Ph.D. candidate in physics Lindsay Weisel: Michigan State University, Ph.D. candidate in physical chemistry Britt Berger: University of Nevada-Reno, Ph.D. candidate in environmental chemistry Zach Johnson: University of Nevada-Reno, Ph.D. candidate in environmental chemistry Current Students Erik Berg Danny Green Diane Moliva Brady Bjerke Other Group Members Dr. Mark Gealy, Department of Physics Dr. Haiyan Fan, Post-doctoral researcher Funding NSF CAREER Grant CHE Henry Dreyfus Teacher/Scholar program Concordia Chemistry Research Fund

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 5 Noisy Light: Definition Broadband Phase incoherent Quasi continuous wave Noisy Light Spectrum Frequency Time resolution on the order of the correlation time,  c

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 23 Pyridine and Water

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 7 Noisy Light: Alternative Its cw nature allows precise measurement of transition frequencies. Its ultrashort noise correlation time offers femtosecond scale time resolution. It offers a different way to study the lineshaping function. It is particularly useful for coherent Raman scattering. Other spectroscopies: photon echo, OKE, FROG, polarization beats…

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 8 Theory Optical coherence theory Perturbation theory: Density operator Noisy Light Spectroscopy

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 9 Theoretical Challenges Complicated Mathematics Complicated Physical Interpretation Difficulty The cw nature requires all field action permutations. The light is always on. The proper treatment of the noise cross-correlates chromophores. Solution Factorized time correlation (FTC) diagram analysis

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 10 Noisy Light Spectroscopy FTC Diagram Analysis Set of intensity level terms (pre-evaluated) Set of evaluated intensity level terms Messy integration and algebra Set of FTC diagrams Construction Rules Evaluation Rules Physics hard easy

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A1 Noisy Light Spectroscopy Utility of FTC Diagrams Organize lengthy calculations Error checking Identification of important terms Immediate information of about features of spectrograms Much physical insight that transcends the choice of mathematical model.

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A2 Noisy Light Spectroscopy Example: I (2) CARS   P(t,{t i }) P(s,{s i }) arrow segments: B, B’ correlation  -dependent line segments: B, B or B’,B’ correlation  -independent FTC analysis Each diagram with arrows has a topologically equivalent partner diagram containing only lines: 2:1 dynamic range Each diagram with arrows has a topologically equivalent partner diagram that has arrows pointing in the opposite direction: signal must be symmetric in 

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 4 Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Measure Spectra Examples IR, UV-VIS, Raman Material response Spectrally narrow Temporally slow Time Domain Response to light pulse Examples PE, transient abs. Material response Spectrally broad Temporally fast

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 4 Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Measure Spectra Examples IR, UV-VIS, Raman Material response Spectrally narrow Temporally slow Time Domain Response to light pulse Examples PE, transient abs. Material response Spectrally broad Temporally fast

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College 4 Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Measure Spectra Examples IR, UV-VIS, Raman Material response Spectrally narrow Temporally slow Time Domain Response to light pulse Examples PE, transient abs. Material response Spectrally broad Temporally fast Is there another useful technique? Noisy light?YES!

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A3 Noisy Light Spectroscopy Example: I (2) CARS Pixel A A Pixel B B Pixel C C The I (2) CARS data shows 2:1 dynamics range  symmetry

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A4 Noisy Light Spectroscopy s  S/N (a) s  D S/N (b)

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A5 Noisy Light Spectroscopy

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A6 Noisy Light Spectroscopy

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A7 Noisy Light Spectroscopy - ∆G° Product Favored - ∆H° Exothermic - ∆S° Entropically unfavorable

NDSU, October 4, 2007Hydrogen Bonding and PyridineDarin J. Ulness, Concordia College A8 Noisy Light Spectroscopy   complex = I complex   free x free I complex = I free at 0.21 mole fraction   complex = 1   free.79   complex = 3.76   free