Download presentation
Presentation is loading. Please wait.
Published byMagnus Jennings Modified over 6 years ago
1
Infrared Spectra and Calculated Binding Energies of γ-butyrolactone Dimers and Trimers
69th annual international symposium on molecular spectroscopy Eric Willis, Chris Baumann June 19, 2014 RI07
2
Optimized Structure of γ-butyrolactone UM06/6-311++(2d,p)
Bond lengths (Å) R12 = 1.189, R62 = 1.353, R56 = 1.426 Angles (°) ∠123 = 128.6, ∠126 = 122.6, ∠623 = 108.8, ∠562 = 110.7 Dihedral Angles (°) ∠1234 = 162.8, ∠1265 = 177.2
3
αβ Dimer
4
αγ Dimer
5
βγ Dimer
6
γγ Dimer
7
Dimer Structural Changes
Elongation of C=O bond observed in all species Cγ – O bond elongated in all species Carbonyl C-O bond shortened in case of γγ and βγ dimers Several bond angle alterations observed in dimers Centered around carbonyl group and ring oxygen Dihedral angle changes indicating changes in ring puckering Increased puckering on one side, decreased on the other
8
αγγ Ring Trimer
9
αβαγ Stacked Trimer Changes magnified in middle unit
Dihedral angles almost unchanged throughout the molecule.
10
The Covalent Trimer
11
Binding Energy (kJ/mol) Counterpoise Correction (kJ/mol)
Energy Information Species Energy (kJ/mol) Binding Energy (kJ/mol) Counterpoise Correction (kJ/mol) Monomer -- αβ Dimer 58.85 3.60 αγ Dimer 57.60 3.50 βγ Dimer 57.74 3.03 γγ Dimer 55.25 3.29 αγγ Ring Trimer 68.81 6.46 αβαγ Stacked Trimer 74.08 7.36 Covalent Trimer 228.85
12
Matrix Isolation Process
GBL deposited on nitrogen at 20 K Cooled down to 12 K Photolysis Annealing
13
Monomer Spectrum
14
Dimer Spectra
15
αγγ Spectrum
16
αβαγ Stacked Trimer
17
Comparison with Experimental Spectrum (13 K)
18
Carbonyl Region Close-up
19
Pre-Annealing
20
Post-Annealing
21
Results of Experimental Spectral Analysis
Dimer and trimer peaks can be differentiated, however individual dimer and trimer structures can’t be resolved Relative amount of dimer and trimer increases with annealing Photolysis affects ratio as well
22
Deuterated Difficulties
23
Anharmonic Corrections
Type of Transition Frequency (cm-1) Intensity (km mol-1) Overtone (v17) 1847.5 60.0 Combination Band (v20 + v12) 1869.8 63.5 Combination Band (v20 + v13) 1866.3 18.3 Combination Band (v21 + v11) 1851.8 13.8 Combination Band (v23 + v10) 1868.1 14.6 Combination Band (v25 + v8) 1856.6 70.5 Several combinations and overtones in this region can contribute to the messiness in the carbonyl region for the deuterated spectrum
24
Electronic Spectroscopy
Monomer Excited State State Energy (eV) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.4293 228.36 2 1.000-A 5.7507 215.6 0.0008 3 5.8472 212.04 4 5.898 210.22 0.0023 5 6.0806 203.9 6 6.3386 195.6 αβ Dimer αγ Dimer Excited State State Energy (ev) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.4822 226.16 2 5.5095 225.04 3 1.000-A 5.8072 213.5 0.0004 4 5.8294 212.69 0.0007 5 6.0303 205.6 6 6.0476 205.01 7 6.0691 204.29 0.0028 8 6.0924 203.51 0.0022 9 6.0983 203.31 10 6.1157 202.73 11 6.267 197.84 12 6.2915 197.07 Excited State State Energy (ev) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.5058 225.19 2 5.5268 224.33 3 1.000-A 5.8378 212.38 0.0002 4 5.8604 211.56 0.0004 5 6.0253 205.77 6 6.0566 204.71 7 6.0573 204.68 0.0024 8 6.0905 203.57 0.0017 9 6.1194 202.61 10 6.1556 201.42 11 6.2555 198.2 12 6.2705 197.73 0.0018
25
βγ Dimer αγγ Trimer γγ Dimer Excited State State Energy (ev)
Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.4865 225.98 2 5.4911 225.79 3 1.000-A 5.8171 213.14 0.0004 4 5.8251 212.84 0.0005 5 6.0585 204.65 6 6.0623 204.52 7 6.0807 203.9 8 6.09 203.59 9 6.0985 203.3 0.0007 10 6.1254 202.41 0.0042 11 6.2771 197.52 12 6.2893 197.13 0.0014 αγγ Trimer Excited State State Energy (ev) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.5602 222.99 2 5.5687 222.65 3 5.5771 222.31 4 1.000-A 5.8732 211.1 0.0009 5 5.8761 211 0.0017 6 5.8883 210.56 0.0012 7 5.9723 207.6 8 5.9775 207.42 9 6.0071 206.4 10 6.0122 206.22 0.0015 11 6.0239 205.82 0.0025 12 6.0529 204.84 0.0048 13 6.1121 202.85 14 6.1197 202.6 15 6.1422 201.86 16 6.2356 198.83 17 6.2446 198.55 18 6.2504 198.36 γγ Dimer Excited State State Energy (ev) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.4809 226.21 2 5.4838 226.09 3 1.000-A 5.8117 213.33 4 5.8218 212.97 0.0008 5 6.0329 205.51 6 6.056 204.73 7 6.0871 203.68 8 6.1076 203 9 6.1182 202.65 0.0003 10 6.145 201.77 0.0045 11 6.322 196.12 12 6.3361 195.68 0.0027
26
αβαγ Trimer Covalent Trimer Excited State State Energy (ev)
Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.4822 226.16 2 5.4857 226.02 3 5.5916 221.73 4 1.000-A 5.804 213.62 0.0005 5 5.8105 213.38 0.0003 6 5.9208 209.4 7 5.9597 208.04 8 5.9775 207.42 9 5.9918 206.92 0.0023 10 6.0047 206.48 11 6.0179 206.03 0.0018 12 6.0309 205.58 0.0024 13 6.09 203.59 14 6.1112 202.88 15 6.175 200.79 16 6.2673 197.83 17 6.2782 197.48 0.0007 18 6.2895 197.13 Excited State State Energy (ev) Wavelength (nm) Oscillator Strength S2 1 3.000-A 5.6354 220.01 2 5.6367 219.96 3 1.000-A 5.663 218.94 0.0006 4 5.6642 218.89 5 5.8073 213.5 6 5.8387 212.35 0.0036 7 5.8994 210.17 8 5.9248 209.26 0.0011 9 5.9379 208.8 10 5.9387 208.77 11 5.955 208.2 0.0008 12 5.9558 208.17 13 6.0737 204.13 14 6.0742 204.11 15 6.1008 203.22 0.0026 16 6.1016 203.2 17 6.2411 198.66 18 6.2415 198.65
27
Summary/Conclusions Structural changes observed in monomer units when dimer and trimer species are formed Dimers and trimers can be detected experimentally using vibrational spectroscopy However, individual dimer and trimer species cannot be resolved Complicated nature of carbonyl region may be due to combination bands and overtones
28
What’s Next? GBL + H2O complexes
Selective photodissociation of trimers and dimers as a possibility More accurate calculations Creating more trimer structures and higher multimers
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.