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Rotational spectra of propargyl alcohol dimer: O-H  O, O-H  , C-H   interactions Devendra Mani and E. Arunan Department of Inorganic & Physical.

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Presentation on theme: "Rotational spectra of propargyl alcohol dimer: O-H  O, O-H  , C-H   interactions Devendra Mani and E. Arunan Department of Inorganic & Physical."— Presentation transcript:

1 Rotational spectra of propargyl alcohol dimer: O-H  O, O-H  , C-H   interactions Devendra Mani and E. Arunan Department of Inorganic & Physical Chemistry, Indian Institute of Science, Bangalore, India.

2 Pulsed Nozzle Fourier Transform Microwave spectrometer (PNFTMW)

3 (a) Molecule of Astro-physical interest – Vinyl alcohol (C 2 H 4 O) was found in 2001. – Propanal (C 3 H 6 O) was found in 2006. – Will propargyl alcohol (C 3 H 4 O) be found ? (b) Combustion Propargyl radical is considered to be precursor in soot formation. C 3 H 3 + C 3 H 3 C 6 H 6 or C 6 H 5 +H Why study propargyl alcohol?

4 Both groups can act as H-bond donor/acceptor c) Multifunctional molecule, like phenylacetylene Offers many possibilities for H-bonding ! Phac-H 2 O Ref1 1.M. Goswami and E. Arunan, Phys. Chem. Chem. Phys., 2011, 13, 14153–14162 2.M. Goswami and E. Arunan, J. Mol. Spectrosc., 2011,268,1-2,147-156 Phac-H 2 S Ref2

5 Propargyl alcohol (monomer)  Due to internal motion of –OH group, this molecule can mainly exist as two conformers: Gauche and trans Relaxed scan at mp2/6-311+(d,p)

6 Rotational Spectrum Many groups in 1960s worked on propargyl alcohol 1,2. Recently in 2005, Pearson et al. revisited the rotational spectrum of this molecule 3. Only gauche conformer could be observed and no spectroscopic signature for trans form was present. Tunneling frequencies between gauche conformers for OH species and OD species have been determined to be 652.38GHz and 213.48 GHz respectively. For propargyl mercaptan (HC≡CCH 2 SH) 4 and propargyl selenol (HC≡CCH 2 SeH) 5 also only gauche conformer was observed! Can trans form be observed in molecular beams ? Can it be stabilized via complex formation with e.g., Ar/H 2 O? 1.Eizi Hirota, Journal of Molecular Spectroscopy 26, 335-350 (1968) 2.K. Bolton, N.L. Owen, J. Sheridan, Nature 217 (1968) 164. 3.J.C. Pearson, B.J. Drouin, Journal of Molecular Spectroscopy 234 (2005) 149–156 4.F. Scappini et al. CPL, 1975, 33(3), 499-501. 5. Harald Møllendal et al. J. Phys. Chem. A 2010, 114, 5537–5543

7 Ar    Propargyl alcohol complex 2.8A 0 3.8A 0  oxygen-hydrogen-Argon angle=145.2 0  Argon-pi bond-carbon angle = 74.5 0  COHAr dihedral angle = 25.9 0 At MP2/6-311+G(3df,2p)  oxygen-hydrogen-Argon angle=138.8 0  COHAr dihedral angle ~ 0 0

8 Ar   g-PAAr   t-PA A/MHz431213563 B/MHz1684932 C/MHz1281863 μaμa 0.9 D1.8 D μbμb 1.1 D1.3 D μcμc 0.8 D0.0 D Ab-initio calculated rotational constants and dipole-moment components Ab-initio calculated rotational constants and dipole-moment components

9 ConstantsLower setUpper setLine centre A/MHz4346.1695(20)4346.1785(22)4346.1735(11) B/MHz1617.15059(41)1617.15664(47)1617.15334(24) C/MHz1245.42035(28)1245.42070(32)1245.42047(18) D J /kHz7.3141(43)7.3166(49)7.3132(27) D JK /kHz61.552(33)61.569(38)61.552(21) D K /kHz-55.30(43)-55.00(48)-55.17(24) d 1 /kHz-2.1765(30)-2.1729(34)-2.1738(18) d 2 /kHz-0.7138(11)-0.7150(13)-0.71468(73) # transitions45 50 rms deviation /kHz4.75.33.1 D. Mani, E. Arunan, ChemPhysChem 14, 754 (2013) Fitted constants

10 Ar  g-PA Ar  methanol Ar  t-PA Nature of interactions: AIM analysis  

11  22 unassigned lines which depend only on PA concentration!!  None of these lines corresponds to the monomer spectra!  Can it be due to higher clusters of propargyl alcohol, dimer or may be trimer?

12 Propargyl alcohol dimer A/MHz2286 B/MHz1234 C/MHz1209 μ a /D1.8 μ b /D1.5 μ c /D2.1  E/kJ.mol -1 31.8 At MP2/6-311+G(3df, 2p) View 1 View 2

13  He used as carrier gas  ~6% of which was flown through a bubbler containing propargyl alcohol  Dependence of the signals was checked by turning off the flow through PA sample.  Already observed signals were used as the initial guess and other signals were searched according to the dimer predictions.  Total 51 transitions could be fitted to the experimental uncertainty.

14 Observed signals for PA-dimer J K -1 K +1 Frequency (MHz) Residue (MHz) Type 2 1 21 1 14525.09040.0026a 2 0 2 1 0 14550.26120.0003a 2 1 1 1 1 04576.26120.0011a 3 0 3 2 1 15601.30990.0078c 2 1 2 1 0 15696.4442-0.0001b 2 1 1 1 0 15773.2026-0.0013c 3 1 3 2 1 26787.26850.0018a 3 0 3 2 0 26824.2441-0.0010a 3 2 2 2 2 16825.9070-0.0010a 3 2 1 2 2 06827.5363-0.0005a 3 1 2 2 1 16864.01720.0014a 4 0 4 3 1 27834.1436-0.0013c 3 1 3 2 0 27933.4491-0.0011b 4 0 4 3 1 37987.6514-0.0022b 5 1 4 4 2 38012.6465-0.0007b 3 1 2 2 0 28086.96120.0024c 2 2 1 1 1 08090.34300.0014b 2 2 0 1 1 08090.7486-0.0004c 2 2 0 1 1 18116.3340-0.0023b 4 2 3 3 2 29100.69890.0002a 4 2 2 3 2 19104.76850.0032a 4 3 2 3 3 19101.7826-0.0050a 4 3 1 3 3 09101.81190.0008a 4 1 4 3 1 39049.01360.0003a 4 0 4 3 0 39096.85860.0000a

15 4 1 3 3 1 29151.3160-0.0009a 6 1 6 5 2 39810.43900.0031b 5 0 5 4 1 310050.48680.0000c 5 0 5 4 1 410306.2977-0.0014b 3 2 2 2 1 110339.99280.0033b 3 2 1 2 1 110342.0246-0.0011c 4 1 3 3 0 310414.03090.0003c 3 2 1 2 1 210418.78550.0002b 4 1 4 3 0 310158.21850.0002b 5 1 5 4 1 411310.19240.0000a 5 0 5 4 0 411367.65880.0000a 5 2 4 4 2 311375.0490-0.0019a 5 4 1 4 4 011376.77700.0009a 5 4 2 4 4 111376.77700.0012a 5 2 3 4 2 211383.16360.0007a 5 3 3 4 3 211377.2647-0.0004a 5 3 2 4 3 111377.34770.0006a 5 1 4 4 1 311438.00390.0011a 5 1 5 4 0 412371.55390.0018b 4 2 3 3 1 212576.6710-0.0015b 6 0 6 5 1 512632.33670.0027b 4 2 2 3 1 312736.2806-0.0033b 3 3 1 2 2 012746.5296-0.0011b 3 3 0 2 2 012746.5296-0.0050c 3 3 1 2 2 112746.94470.0066c 5 1 4 4 0 412755.17700.0023c

16 A /MHz 2321.83350(42) B /MHz 1150.47741(21) C /MHz 1124.88979(16) D J /kHz 1.8422(31) D JK /kHz 0.375(11) D K /kHz -0.982(40) d 1 /kHz -0.0457(27) d 2 /kHz -0.1498(22)  /kHz 2.5 # transitions51 Fitted Constants D. Mani, E. Arunan, manuscript under preparation

17 H-16 as Deuterium Isotopic substitution: 1 A /MHz2299.9 B /MHz1148.4 C /MHz1119.6 Calculated constants

18 J K -1 K +1 Frequency (MHz) obs -cal (MHz) 2 1 1 1 0 15748.995-0.0007 3 1 3 2 1 26749.679-0.0055 3 0 3 2 0 26797.907-0.0005 3 1 2 2 1 16851.0910.0018 3 1 3 2 0 27864.0250.0043 4 0 4 3 1 37994.1440.0013 4 1 4 3 1 38998.544-0.0008 4 0 4 3 0 39060.247-0.0095 4 2 3 3 2 29067.0650.014 4 2 2 3 2 19074.3140.008 4 1 3 3 1 29133.683-0.0103 4 1 4 3 0 310064.66-0.0021 5 0 5 4 1 410315.150.0041 5 1 5 4 1 411246.55-0.0021 5 0 5 4 0 411319.560.004 5 2 4 4 2 311332.59-0.0098 5 2 3 4 2 211347.03-0.0068 5 1 4 4 1 311415.340.0065 5 1 5 4 0 412250.950.0038 Observed signals

19 Fitted constants A /MHz 2297.8207(52) B /MHz 1150.4122(13) C /MHz 1116.6032(14) D J /kHz 1.826(20) D JK /kHz 0.40(14) D K /kHz d 1 /kHz -0.059(17) d 2 /kHz -0.174(10)  /kHz 7.9 #transitions19 D. Mani, E. Arunan, manuscript under preparation

20 H-8 as Deuterium A /MHz2304.9 B /MHz1146.9 C /MHz1124.3 Isotopic substitution: 2 Calculated constants

21 J K -1 K +1 Frequency (MHz) obs -cal (MHz) 3 1 3 2 1 26801.51200.0030 3 0 3 2 0 26828.0980-0.0050 3 1 2 2 1 16856.13700.0006 4 1 4 3 1 39068.2370-0.0006 4 0 4 3 0 39102.9418-0.0001 4 2 3 3 2 29104.9295-0.0009 4 2 2 3 2 19107.01250.0013 4 1 3 3 1 29141.06000.0021 4 1 4 3 0 310178.22450.0000 5 1 5 4 1 411334.59300.0007 5 0 5 4 0 411376.76130.0001 5 2 4 4 2 311380.5950-0.0001 5 2 3 4 2 211384.7490-0.0012 5 1 4 4 1 311425.5832-0.0001 Observed signals

22 A /MHz 2301.8767(51) B /MHz 1147.29807(87) C /MHz 1129.08541(85) DJ /kHz 1.7851(72) DJK /kHz 0.233(51) DK /kHz d1 /kHz -0.042(10) d2 /kHz -0.1130(33)  /kHz 2.5 #transitions14 Fitted constants D. Mani, E. Arunan, manuscript under preparation

23 Isotopic substitution: 3 H-16 and H-8 as Deuterium A /MHz2283.2 B /MHz1144.6 C /MHz1119.3 Calculated constants

24 J K -1 K +1 Frequency (MHz) obs -cal (MHz) 3 1 3 2 1 26764.8930-0.0016 3 0 3 2 0 26802.1560-0.0008 3 2 2 2 2 16803.91500.0000 3 2 1 2 2 06805.6330-0.0010 3 1 2 2 1 16842.3510-0.0094 2 2 1 1 1 17992.96800.0025 4 0 4 3 1 37994.1390-0.7342 4 1 4 3 1 39019.18600.0162 4 0 4 3 0 39067.3170-0.0018 4 2 3 3 2 29071.3630-0.0005 4 2 2 3 2 19075.66000.0053 4 1 3 3 1 29122.4200-0.0051 5 0 5 4 1 410306.30450.0074 5 1 5 4 1 411272.8660-0.0012 5 0 5 4 0 411330.5803-0.0135 5 2 3 4 2 211346.9195-0.0024 5 1 4 4 1 311401.86300.0051 Observed signals

25 A /MHz 2282.0237(32) B /MHz 1146.9285(19) C /MHz 1121.1011(21) DJ /kHz 1.764(25) DJK /kHz -0.21(18) DK /kHz d1 /kHz -0.054(25) d2 /kHz -0.118(17)  /kHz 8.7 #transitions17 Fitted constants D. Mani, E. Arunan, manuscript under preparation

26 AIM analysis O-H  OC-H   O-H  Contactρ(r) in a.u.  2 ρ(r) in a.u. OH  O 0.02330.0921 OH  0.01560.0501 CH  0.00580.0166

27 (H 2 O) 2 H 2 O  C 2 H 2 (C 2 H 2 ) 2 CH 4  C 2 H 2 H 2 O  C 2 H 4 (CH 3 OH) 2

28 ContactComplexρ(r) in a.u.  2 ρ(r) in a.u. OH  O PA-dimer 0.02330.0921 Water-dimer 0.02150.0960 Methanol-dimer 0.02560.1018 OH  PA-dimer 0.01560.0501 Acetylene..water 0.01000.0324 Ethylene…water 0.01000.0291 CH  PA-dimer 0.00580.0166 methane_acetylene0.00420.0109 acetylene_dimer0.00640.0178 D. Mani, E. Arunan, manuscript under preparation

29 Other face of methanol: The “carbon bond”.

30 ESP value at face centre +50.2 kJ.mol -1  Tetrahedral face of methane has a –ve centre! ESP value at face centre = -7.5 kJ.mol -1 Methanol ESP surface

31  Microwave spectra of complexes like CH 4  HF/HCl/HCN and CH 4  H 2 O show that the hydrogen of HX molecule points towards the tetrahedral face of methane.  Microwave spectra of CH 4  ClF complex shows that the Cl points towards the tetrahedral face of methane.  AIM studies confirm the presence of interactions between carbon of methane and hydrogen of HX molecules as well as Cl of ClF leading to the formation of a hydrogen bond and halogen bond respectively.  What are the bonding properties of the CH 3 face of methanol ?  Being electropositive can this face interact with electron rich centres of molecules like water ?

32 H 2 O  CH 3 OH complex was optimized taking initial geometry in which oxygen of water points towards the CH 3 face of methanol. 3.167 Å BSSE corrected interaction energy = 4.2 kJ mol -1 Electron density ρ(r), at intermolecular b.c.p. = 0.0050 a.u. Laplacian of electron density  2 ρ(r) at intermolecular b.c.p. = 0.0248 a.u. H 2 O  CH 3 OH complex b.c.p. Is this a general interaction ?

33 Optimized geometries for (a) H 2 OCH 3 OH, (b) H 2 SCH 3 OH, (c) HFCH 3 OH, (d) HClCH 3 OH, (e)HBrCH 3 OH, (f) LiFCH 3 OH, (g) LiClCH 3 OH, (h) LiBrCH 3 OH, (i) ClFCH 3 OH, (j) H 3 NCH 3 OH, (k) H 3 PCH 3 OH complexes. Similar interaction with other molecules D.Mani, E. Arunan, PCCP, DOI: 10.1039/C3CP51658J

34 Nomenclature ? D.Mani, E. Arunan, PCCP, DOI: 10.1039/C3CP51658J

35 Conclusions  Rotational spectra of PA-dimer and its three deuterated isotopologues has been observed and fitted by a semirigid rotor asymmetric top Hamiltonian.  Observed rotational constants are close to the Ab-initio predicted structure.  AIM calculations show that in the dimer two monomer entities are in a three point contact having O-H  O, O-H , C-H    interactions.  54 lines remain unassigned which could be due to higher PA-clusters.

36 Acknowledgements  My group  Department of Science and Technology, India.  Indo-French Centre of Pure and Applied Research.  Council of Industrial and Scientific Research, India.  Royal Society of Chemistry (PCCP) for travel grant.  Indian Institute of Science, Bangalore, India.

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