Rotational Spectra of Adducts of Formaldehyde with Freons Qian Gou, 1 Gang Feng, 1 Luca Evangelisti, 1 Montserrat Vallejo-López, 2 Alberto Lesarri, 2 Walther Caminati, 1 Emilio J. Cocinero 3 1 Dipartimento di Chimica “G. Ciamician” dell’Università, Via Selmi 2, I Bologna, Italy 2 Departamento de Química Física y Química Inorganica, Facultad de Ciencias, Universidad de Valladolid, E Valladolid, Spain 3 Departamento de Quimica Fisica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco,E Bilbao, Spain Columbus

2 Introduction With formaldehyde Angew. Chem. Int. Ed., 2011, 50, Angew. Chem. Int. Ed., 2006, 45, J. Am. Chem. Soc. 1999, 121,

3 I.Difluoromethane − Formaldehyde CH 2 F 2 − H 2 CO Phys. Chem. Chem. Phys., 2013, 15, 6714.

MP2/ G** calculated spectroscopic parameters of the plausible conformers of CH 2 F 2 – H 2 CO Ab initio calculation 4 ΔE/cm ΔE BSSE /cm A, B, C /MHz13898, 1766, , 1307, 1176 |μ a |, |μ b |, |μ c |/D2.5, 0.4, , 0.0, 0.0 D J /kHz D JK /kHz M cc /uǺ

Internal Rotation The 0 + and 0 ­ component lines of the 4 04 ­3 03 μ a transition of normal CH 2 F 2 – H 2 CO Relative intensity 1:3 5 Rotational spectra

CH 2 F 2 -HCOH ( 0 + ) CH 2 F 2 -HCOH ( 0 - ) 13 CH 2 F 2 -HCOH ( 0 - ) CH 2 F 2 -H 13 COH ( 0 - ) A/MHz (3) (3)13675(2)13671(2) B/MHz (1) (1) (8) (8) C/MHz (1) (1) (8) (8) D J /kHz2.33(1) 2.29(2)2.22(2) D JK /kHz21.25(5)20.78(5)[20.78] d 1 /kHz-0.24(1)-0.23(1)[-0.23] d 2 kHz0.029(6)0.022(6)[0.022]  /kHz N23 99 Spectroscopic parameters for complex of CH 2 F 2 – H 2 CO including 13 C isotopologues Rotational spectra 6 It’s not possible to determine the vibrational energy spacing (∆E) between the two tunneling states

Molecular Structure C–H … F–C Bifurcated C–H 2 … O=C Weak hydrogen bonds(WHB) a/Åa/Åb/Åc/Å C CH2F2 Exp.±0.965(3)±0.370(8)0 Cal C H2CO Exp.±2.551(1)±0.389(8)0 Cal Substitution coordinates of the two carbon atoms M cc = 1.69 uÅ 2 M cc = 1.65 uÅ 2 7

Molecular Structure The parameters fitted r H8F2 /Å ∠ C7H8 … F2/° ∠ H8 … F2C1/° Exp.(r 0 )2.658(1)113.56(1)113.41(5) Cal The parameters derived r/År/Åα/°β/° Exp.(r 0 )3.132(1)73.58(5)84.99(5) Cal

Internal Rotation Experimental and calculated data Exp.Cal. ∆M aa /uǺ ∆M bb /uǺ ∆M cc /uǺ ∆E/MHz-3411 Potential barrier and structural relaxations V 2 =180(10) cm -1 ∆r =0.027Å∆α =-1.4°∆β = 2.6(5)° J. Mol. Spectrosc. 1979, 76, 266 Potential energy pathway Flexible Model Structural relaxations

10 Internal Rotation Flexible model ERHAM ΔE/GHz  /° ΔE/GHz CH 2 F 2 -H 2 O CH 2 ClF-H 2 O CHClF 2 -H 2 O CH 2 F 2 -CH 2 O Tunnelling splittings calculated for some complexes of freons with C 2v symmetric molecules J. Mol. Struct., 2005, 742, 87. Angew. Chem. Int. Ed., 2006, 45, J. Mol. Spectrpsc.., 2011, 268, 7.

Dissociation Energy Stretching force constant: Dissociation energy by assuming a Lennard-Jones potential function: a b R CM =3.65 Å 9.3 Nm kJmol J. Chem. Phys. 1983, 78, Can. J. Phys. 1975, 53, J. Am. Chem. Soc. 1963, 85, 1715.

Dissociation Energy ComplexesE D /kJ mol -1 CH 2 F 2 … OCS2.1 (CH 2 F 2 ) CH 2 F 2 … H 2 O7.5 CH 2 F 2 … C 2 H 4 O9.6 CH 2 F 2 … H 2 CO10.4 J. Phys. Chem. A, 2008, 112, Angew. Chem. Int. Ed. 1999, 38, J. Am. Chem. Soc. 1999, 121, ChemPhysChem 2004, 5,

13 II. Chlorofluoromethane − Formaldehyde CH 2 FCl − H 2 CO

14 Ab initio calculation ΔE/cm ΔE BSSE /cm A, B, C /MHz 4976, 1995, , 1625, , 1196, 1106 |μ a |, |μ b |, |μ c |/D 0.3, 0.0, , 0.8, , 0.4, 0.,0 χ aa /MHz ( χ bb - χ cc )/MHz M cc /uǺ MP2/ G** calculated spectroscopic parameters of the plausible conformers of CH 2 FCl – H 2 CO

15 Rotational spectra I ( 35 Cl)=3/2 I ( 37 Cl)=3/2 Recorded 3 13 ←2 12 transition of the observed conformer of CH 2 FCl-H 2 CO showing the 35 Cl hyperfine structure and tunnelling splitting due to the internal motion of formaldehyde. Relative intensity 1:3

16 Rotational spectra 35 Cl 37 Cl A/MHz (2) (2) (4) (4) B/MHz (4) (4) (3) (3) C/MHz (4) (4) (2) (2) χ aa /MHz31.13(1)31.11(2)24.59(4)24.54(5) (χ bb - χ cc )/MHz (2) (3)-83.53(4)-83.56(5) Δ c /uÅ D J /kHz1.595(2)[1.595] D JK /kHz17.77(4)[17.77] d 1 /kHz0.329(3)[0.329] d 2 /kHz0.086(2)[0.086]  /kHz N15070 Spectroscopic parameters for complex of CH 2 FCl – H 2 CO

17 Molecular Structure Bond length/ÅValence angle/°Dihedral angel/° Cl2C F3C11.370F3C1Cl H4C11.086H4C1F3109.0H4C1F3Cl H5C11.086H5C1F3109.0H5C1F3H O6Cl23.554(8)O6Cl2C161.9(2)O6Cl2C1F C7O61.215C7O6Cl282.8(10)C7O6Cl2C H8C71.104H8C7O6121.6H8C7O6C10.0 H9C71.104H9C7O6121.6H9C7O6H Derived structural parameters r 1 /Å2.918α/°120.8 r 2 /Å2.821β/°96.6 R CM /Å3.700γ/°96.7 r 0 and r e (MP2/ G (d, p)) geometries of the CH 2 FCl-H 2 CO C–H … Cl–C Bifurcated C–H 2 … O=C Weak hydrogen bonds(WHB)

Internal Rotation Experimental and calculated data Exp.Cal. ∆M aa /uǺ ∆M bb /uǺ ∆M cc /uǺ ∆E/MHz-5389 Potential barrier and structural relaxations V 2 =125(10) cm -1 ∆R=-0.098Å∆θ=-2.3°∆φ= 12.2(5)° J. Mol. Spectrosc. 1979, 76, 266 Potential energy pathway Flexible Model Structural relaxations R(τ) = R 0 + 1/2 ΔR [1 – cos (2τ)] θ(τ) = θ 0 + 1/2 Δθ [1 – cos (2τ)] ϕ (τ) = ϕ 0 + 1/2 Δ ϕ [1 – cos (2τ)

Dissociation Energy Stretching force constant: Dissociation energy by assuming a Lennard-Jones potential function: complexk s /Nm -1 E B /kJmol -1 CH 2 FCl … H 2 O CH 2 FCl … H 2 CO J. Chem. Phys. 1983, 78, Can. J. Phys. 1975, 53, J. Am. Chem. Soc. 1963, 85, 1715.

20 III. Chlorotrifluoromethane − Formaldehyde CF 3 Cl − H 2 CO

MP2/ G** calculated spectroscopic parameters of the plausible conformers of CF 3 Cl – H 2 CO Ab initio calculation 21 ΔE/cm ΔE BSSE /cm A, B, C /MHz 4821, 787, , 872, , 848, , 894, 795 |μ a |, |μ b |, |μ c |/D 1.7,2.0,0.02.1, 0.0, , 1.7, , 2.8, 0.0 χ aa /MHz ( χ bb - χ cc )/MHz

22 Rotational spectra Recorded 6 1 ←5 1 transition of the observed conformer of CF 3 Cl- H 2 CO showing the 35 Cl hyperfine structure and the internal motion of formaldehyde. Feature of symmetric top

23 Rotational spectra m = 0m = ±1 CF 3 35 Cl-H 2 COCF 3 37 Cl-H 2 COCF 3 35 Cl-H 2 COCF 3 37 Cl-H 2 CO B/MHz (2) (3) (3) (4) 1.5χ aa /MHz (2)-87.0(2)-110.3(2)-87.4(4) D J /kHz1.642(1)1.639(3)1.660(3)1.676(5) D JK /MHz1.7050(3)1.7116(2)1.6914(2)[1.6914] H JK /kHz0.670(3)[0.670] σ/kHz N An effective symmetric top

24 Molecular Structure a/Åa/Å rere rsrs ±0.294(5) Assuming that the formation of the complex does not affect the electric field gradient at chlorine nucleus: χ aa = 0.5χ z (3cos 2 θ za - 1) θ = 10.6° r e and r s coordinates of substituted chlorine atom Halogen Bond C −Cl···O=C

Dissociation Energy Stretching force constant: Dissociation energy by assuming a Lennard-Jones potential function: k s = 128π 4 (μR CM ) 2 B 4 /hD J E B = 1/72k s R 2 CM complexk s /Nm -1 E B /kJmol -1 CF 3 Cl … H 2 O CF 3 Cl … H 2 CO J. Chem. Phys. 1983, 78, Can. J. Phys. 1975, 53, J. Am. Chem. Soc. 1963, 85, 1715.

26 Conclusions E D = 7.5 kJ mol -1 V 2 = 340 cm -1 ∆E = 0.66 GHz E D = 10.4 kJ mol -1 V 2 = 180 cm -1 ∆E = 3.41 GHz E D = 8.5 kJ mol -1 V 2 = 336 cm -1 ∆E = 0.82 GHz E D = 9.8 kJ mol -1 V 2 = 125 cm -1 ∆E = 5.39 GHz E D = 7.7 kJ mol -1 E D = 11.0 kJ mol -1

27 Acknowledgement Prof. W. Caminati Dr. L. B. FaveroDr. A. MarisDr. L. Evangelisti Ms. C. Calabrese Dr. F. Gang Prof. S. Melandri Thanks for attention ! attention ! Mr. L. Spada