ROTATIONAL SPECTRA OF THE TRIFLUORO ETHANOL (TFE) -WATER CLUSTERS AND THE TFE DIMERS - PowerPoint Presentation

Slide1

ROTATIONAL SPECTRA OF THE TRIFLUORO ETHANOL (TFE) -WATER CLUSTERS AND THE TFE DIMERS

Javix

Thomas and

Yunjie Xu

Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2.Slide2

2

Motivation

1. Xu

et al.

J. Chem. Phys., 1995, 103, 9541.2. Scharge et al. Z. Phys. Chem., 2008, 222, 1407.

TFE is an important organic solvent. TFE and water are often used as co-solvents in the studies of protein folding process. The interactions of TFE with itself and with water may play some significant roles molecular recognition of biomolcules.  The TFE monomer was extensively studied using rotational spectroscopy1 and the TFE dimer was investigated using low resolution FTIR spectroscopy.2Slide3

Related alcohols

trans

conformation

gauche

conformation

Extra binding site

Ethanol FE

gauche

conformation

TFESlide4

4

4

Conformers of

TFE

dimer with O-H…O H-bond

H-bond donor/acceptor: homo and het 2Insertion into intra-ring: inserted or associated X 2O lone pairs of acceptor:

compact or open X 2 = 8

1.80

2.52

2.52

2.11

2.52

2.52

associated

inserted

1.62

associated

inserted

2.52

2.52

1.91

1.86

2.52

2.52

2.01

homo

heteroSlide5

5

Confs

Δ

Do

kJ/mol

A B CGHzμ

a

,

μ

b

,

μ

c

i

/

hom

0

1.61147 0.43043 0.41144

-2.43

,

-0.1

3,

-1.26

a/

hom

2.82

1.62591 0.39955 0.38001

1.4

3,

2.34

,

-3.3

2

i

/het

0.756

1.51552 0.44402 0.40357

3.12

,

1.13

,

0.25

a/het

3.226

1.83234 0.35243 0.34739

-1.2

8,

0.38

,

-3.8

1

MP2/6-311++g(

d,p

) level of theory

Properties of the f

our

conformers of the TFE dimerSlide6

6

Searches were carried out using a chirp pulsed FTMW spectrometer.

Final measurements were done with a cavity based FTMW spectrometer

0.3%~0.5%

TFE (and water) in Neon or Helium backing gas ( 2~3 atm)

Experimental detailsSlide7

Our chirp pulsed FTMW spectrometer

G

. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman and B. H. Pate,

Rev.

Sci. Inst.

, 2008, 79, 053103; S. Dempster, O. Sukhorukov, Q.-Y. Lei, W. Jäger, J. Chem. Phys., 2012, 137, 174303; J. Thomas, J. Yiu, J. Rebling, W. Jäger, Y. Xu, J. Phys. Chem. A., Online, Apr. 25, 2013, DOI: 10.1021/jp402552t.Slide8

Broadband spectrum of

TFE+HeSlide9

Assignment of the TFE dimer Slide10

10

2.82

3.23

0

1.02

ichet

ichom

achom

achet

iohet

iohom

Relative energy

/ kJmol

-1

MP2/

aug

-cc-pVTZ//MP2/6-311++G(

d,p

)

The TFE

dimer versus

the 2-FE

dimer

X. Liu, N. Borho, Y. Xu,

Eur. J.

Chem.

2009

, 15, 270.

0

0.76

ahet

ihom

ahom

ihet

Relative energy

/ kJmol

-1

2.91

2.81

4.52

3.64

MP2/6-311++G(

d,p

)Slide11

6

Conformers of

the TFE-water dimer

Do=0

Do=10.9

Do=21.6

Do=22.3MP2/6-311++G(d,p), ZPE corrected: kJ/mol

2.64

1.87

2.38

2.06

2.55

2.17

2.55

2.55

2.27

1.77

1.70

Do=9.0

Do=16.7Slide12

Broadband spectrum of

TFE+water+He

TFE+water+He

TFE+HeSlide13

Assignment of the TFE-water spectrum

Simulated spectrum of the TFE-waterSlide14

14

Semirigid rotor fits of the most stable TFE-water dimer

Spec. Component 1 Component 12

Const.

A 3.5428110(9) 3.542896(1)

B 1.5504968(2) 1.5504926(2) C 1.3583053(2) 1.3582814(2) DJ 0.1299(2)E-05 0.1298(3)E-05 DJK -0.39(2)E-06 -0.37(2)E-06 DK 0.24(2)E-05 0.24(2)E-05 d1 -0.243(2)E-06 -0.241(2)E-06 d2 0.36(1)E-07 0.36(2)E-07

N 45 45SD 2.3 2.7Slide15

15

Conclusion and future

work

** Only the most stable conformer of the TFE dimer was

identified, in contrast to the related ethanol and 2-

fluoroethanol cases. ** Some unassigned lines may be attributed to the TFE trimer and perhaps even the TFE tetramer.

** Many strong unassigned lines in TFE+water+He are likely due to larger TFE-water clusters. Their assignments are in progress. Slide16

16

Acknowledgement

Funding:

UofA

, NSERC, CFI, AI, Petro-Canada.

Thank you!

Questions?