1. Halogen bonding vs hydrogen bonding: CHF2INH3 vs CHF2IN(CH3)3
Chris Medcraft
Dror Bittner, Nick Walker
Yannick Geboes, Wouter Herrebout

2. Introduction CHF2I can form halogen or hydrogen bonds
When is halogen bonding energetically favoured over hydrogen bonding?

3. Halogen bond
Electrostatic potential of Br2
Halogen bond describes attractive interaction between electron donor (e.g. NH3) and a halogen atom. +
A.C. Legon, PCCP, 2010, 12, 7736
S.L. Stephens et al., PCCP, 2011, 13, 20736

4. Chirped-pulse Fourier transform microwave spectrometer (CP-FTMW)
Nd:Yag 532 nm laser
~25 mJ/pulse
N. R. Walker et al., Phys. Chem. Chem. Phys., 16, 2014, 25221

6. Halogen vs Hydrogen bond
Halogen bond predicted to be more stable for trimethylamine a a
ΔE = 0 kJ/mol
ΔE = 2.7 kJ/mol
Halogen bonded
Hydrogen bonded
A [MHz]
3182.9
1432.3
B [MHz]
494.0
540.7
C [MHz]
477.1
462.2
μA/μB/μC [D]
2.4/0.0/1.2
2.9/1.0/0.0
MP2/aug-cc-pvdz

7. CHF2I---N(CH3)3 50 261K FIDs Intensity [μV] 7 8 9 10 11 18 12 13 14 15
261K FIDs
Intensity [μV] 7 8 9 10 11 18 12 13 14 15 16 17
Frequency [GHz]

8. CF2HI---N(CH3)3 3 261K FIDs Intensity [μV] 7 8 9 10 11 18 12 13 14 157 8 9 10 11 18 12 13 14 15 16 17
Frequency [GHz]

9. J = 14  13 J = 15  14 2 2.5 Intensity [μV] Intensity [μV]
Ka=1
Ka=1
Ka=1
Ka=1
13.7
13.8
13.9
14.7
14.8
14.9
Frequency [GHz]
Frequency [GHz]
Halogen bonded
Hydrogen bonded
‘Fit’
A [MHz]
3182.9
1432.3 ??
B [MHz]
494.0
540.7
501.2
C [MHz]
477.1
462.2
484.4
μA/μB/μC [D]
2.4/0.0/1.2
2.9/1.0/0.0
a-type

10. Iodine Nuclear Quadrupole Coupling Constants
χaa(I)
CF3I monomer
(11)
CHF2I monomer
(34)
-NH3
(75)
-N(CH3)3
(17)
-2071(15)
-84Kr
− (63)
-CO
(45)
-H2S
(11)
-H2O
(84)
-N2
− (13) a a
MP2/aug-cc-pvdz+ANO-RCC
CF3I---N(CH3)3
CHF2I---N(CH3)3
Halogen bond
Hydrogen bond
χaa
(47)
-2071(15)
-190.4
χbb-cc
18(62)
91.9

11. I C O
H3N I
H2O I I
H2S I
C2H4
1 S.L. Stephens et al., Phys. Chem. Chem. Phys (2011)
2 S.L. Stephens et al., J. Chem. Phys (2011)

12. CF3I14NH3 Free rotation of NH3 Energy/MHz 13850 13855 13860 13865
13870
13875
A species sim.
E species sim.
Total (A and E) sim.
CF3I14NH3
Frequency [MHz]
S.L. Stephens et al., PCCP, 2011, 13, 20736

13. Large amplitude motion(s)

14. CHF2I---NH3 127K b a a a ΔE=2.5 kJ/mol MP2/aug-cc-pvdz ΔE = 0 kJ/mol
Frequency [MHz]
Halogen bonded
Hydrogen bonded
A [MHz]
8765.9
2155.3
B [MHz]
1034.5
1462.1
C [MHz]
960.5
1041.3
μA/μB/μC [D]
2.7/0.0/1.0
2.1/2.9/0.0

15. CF3I---CO2 J = 19  18 J = 11  10 1.1M FIDs Frequency [MHz]
8120
8140
14020
14030
14040
Frequency [MHz]
Frequency [MHz]

16. CF3I---CO2 Structural Analysis
12C16O2----ICF3
13C16O2----ICF3
12C18O2----ICF3
B [MHz]
(14)
(16)
(17)
DJ [kHz]
(20)
(23)
(25)
DJK [kHz]
(81)
131.40(14)
131.26(12)
Χaa(I) [MHz]
(60)
(85)
(91)
Number
392
290
195
σRMS [kHz]
31.0
29.9
24.9
r0 = (2) Å

17. Outlook Throw data away and cry in the corner New spectrometer
Tektronix SX 100GS/s Scope (32+Hz)
2-8 GHz TWT
2-18 GHz Horns
Measure lower J’s
Easier to analyse?

18. Acknowledgements
Newcastle University Nick Walker John Mullaney Dror Bittner Argonne National Laboratory Daniel Zaleski University of Bristol Tony Legon Colin Western

19. BICF3 Complexes I C O H3N I H2O I H2S I C2H4
1 S.L. Stephens et al., Phys. Chem. Chem. Phys (2011) 2 S.L. Stephens et al., J. Chem. Phys (2011)

20. BCF3I vs BICl k(BICl) k(BICF3) NH3 H2S H2O N2 CO Kr
Complexes formed between B and ICl are more strongly bound than those formed between B and ICF3. Both series provide evidence for formation of halogen bonds.