Microwave Spectra and Structure of CF 3 I···PH 3 by chirped-pulse spectroscopy in context of the CF 3 I···B and ClI···B series Susanna L. Stephens, Nick R. Walker, Antony C. Legon 69 th International Symposium on Molecular Spectroscopy, Champaign-Urbana, Illinois 20 th June 2014

“A halogen bond R-X Y-Z occurs when there is evidence of a net attractive interaction between an electrophilic region on a halogen atom X belonging to a molecule or a molecular fragment R-X (where R can be another atom, including X, or a group of atoms) and a nucleophilic region of a molecule, or molecular fragment, Y-Z.” Gautam R. Desiraju, P. Shing Ho, Lars Kloo, Anthony C. Legon, Roberto Marquardt, Pierangelo Metrangolo, Peter A. Politzer, Giuseppe Resnati, and Kari Rissanen. Denition of the halogen bond, IUPAC Provisional Recommendation. The more of the following features of halogen bonding below that are satisfied the more reliable an identification of a halogen bond: 1) The length of the bond X Y will tend to be less than the sum of their Van de Waal radii of the atoms, X and Y. 2) The angle R-X Y will tend to be linear as the halogen will align with the lone-pair or π-system of the halogen acceptor. This angle may be perturbed slightly by other bonding effects elsewhere in the molecular system. 3) The covalent bond R-X will tend to increase upon bond to the halogen acceptor. 4) The strength of the halogen bonding will decrease when the electronegativity of X increases and the ability of R to withdraw electrons decreases. 5) Although the relative dependence of different bonding forces varies, the two primary bonding mechanisms are dispersion and electrostatic effects (which includes polarisation). 6) Electron density topology analysis tends to show a bond path X and Y and a bond critical point between X and Y. 7) Vibrational modes corresponding with the bond X Y are present upon bonding and vibrational modes in the Raman and IR regions of R-X and Y-Z are suitably shifted. 8) A characteristic shift to the blue is usually observed in the UV-visible spectrum of the halogen bond donor when the X Y bond is formed. 9) Typically the formation of the X Y bond will also change the characteristic nuclear magnetic resonance signals of R-X and Y-Z. 10) The halogen X may be involved in multiple halogen bonds. 11) The halogen bond may be included in reaction mechanisms including halogen transfer reactions.

Halogen Bonding in the Gas-phase: A Comparison of the Iodine Bond in B···ICl and B···ICF 3 for simple Lewis Bases B J Grant Hill, Anthony C Legon, David P Tew and Nicholas R Walker, Topics in Current Chemistry: Halogen Bonding: Impact on Materials Chemistry and Life Sciences C ∞V C 2V C 3V C s at equilibrium C 2V in zero point state C s in equilibrium and zero point state C 3V C S Highest symmetry C 3V C S Highest symmetry C S Highest symmetry C S Highest symmetry C 3V Highest symmetry C 3V Highest symmetry C 2V

Newcastle CPFTMW Spectrometer S. L. Stephens, N. R. Walker, J. Mol. Spectr., 263, 27 (2010) Frequency /MHz

~ averages 1 % CF 3 I, 1 % PH 3 balance 6 bar Ar Frequency /MHz 107 AgI 109 AgI Frequency /MHz

C 3v Symmetric top ?Internal rotation? CF 3 I···NH 3 & CF 3 I···N(CH 3 ) 3 Susanna L. Stephens, Nicholas R. Walker and Anthony C. Legon, Phys. Chem. Chem. Phys., 13, (2011) CH n Y n X··NH 3 G. Valerio, G. Raos, S. V. Meille, P. Metrangolo and G. Resnati, J. Phys. Chem. A, 104, 1617 (2000) CH 3 I···NH 3 G. T. Fraser, F. J. Lovas, R. D. Suenram, D. D. Nelson, Jr. and W. Klemperer, J. Chem. Phys., 84, 5983 (1986) The Hamiltonian   r m.c. Geometric model

Frequency /MHz Assigned spectra of 12 CF 3 I∙∙∙PH 3

84 Kr 57.0 % 86 Kr 17.3 % 82 Kr 11.6 % 83 Kr 11.5 % 12 CF 3 I∙∙∙PH 3 Spectral constants A-stateE-state B 0 /MHz (97)( ) D J /Hz125.21(28)125.25(24) D JK /kHz1.9502(62)1.9841(61) D Jm /kHz-44.57(18) η J /kHz (16) χ aa (I) /MHz (11) (88) N σ r.m.s. /kHz

  r m.c. 12 CF 3 I  84 Krk  = 2.798(2) N m CF 3 I  COk  = 3.950(2) N m CF 3 I  PH 3 k  = 6.27(2) N m -1 Model of subunit oscillation

CF 3 I···CO and CF 3 I···Kr J. Chem. Phys., 135, (2011) CF 3 I···C 2 H 4 J. Mol. Spec., 280, 47 (2012) CF 3 I···NH 3 and CF 3 I···N(CH 3 ) 3 PCCP, 13, (2011) CF 3 I···H 2 O and CF 3 I···H 2 S PCCP, 13, (2011) α /° (B) γ /° (CF 3 I) CF 3 I r m.c. /Å Kr-5.0(5) OC10(3)4.0(5)4.9644(12) NH (12)4.12(37)3.997(1) N(CH 3 ) (20)(4.12)4.080(2) H2OH2O34.4(20)(<5.0)- H2SH2S93.7(2)(<5.0)- PH 3 (20)(5)- N2N2 --- C2H4C2H4 --- C2H2C2H2 --- Determined geometries α /° (B) γ /° (CF 3 I) CF 3 I r m.c. /Å CF 3 I r (Z···I) /Å ClI r (Z···I) /Å Δr /Å Kr-5.0(5) (7)-- OC10(3)4.0(5)4.9644(12)3.4281(12)3.011(1)0.417(2) NH (12)4.12(37)3.997(1)3.039(1)2.711(2)0.327(3) N(CH 3 ) (20)(4.12)4.080(2)2.781(2)-- H2OH2O34.4(20)(<5.0) (18)2.828(1)0.225(3) H2SH2S93.7(2)(<5.0) (2)3.154(3)0.405(4) PH 3 (20)(5)-3.571(3)2.963(1)0.608(4) N2N (1)3.180(2)0.258(3) C2H4C2H (2)3.032(2)0.402(4) C2H2C2H (2)3.115(2)0.327(4)

Intermolecular stretching force constants and disassociation energies k σ /(N m -1 )D e /(kJ Mol -1 ) B···ICF 3 B···IClB···ICF 3 B···ICl N2N2 2.94(2)5.35(2) OC3.950(2) HCN···14.5(1) C2H4C2H4 4.95(1)14.0(1) C2H2C2H2 4.96(7)12.1(1) H2OH2O8.8(1)15.9(2) H2SH2S6.7(1)16.55(5) PH (2)20.7(1) NH (2)30.4(3) D. J. Millen. Can. J. Chem., 63, 1477 (1985) D e calculated by CCSD(T)(F12*)/cc-pVDZ-F12 level of theory where basis set superposition is accounted for by counterpoise correction k σ (B···I) /(N m -1 ) Halogen Bonding in the Gas-phase: A Comparison of the Iodine Bond in B···ICl and B···ICF 3 for simple Lewis Bases B J Grant Hill, Anthony C Legon, David P Tew and Nicholas R Walker, Topics in Current Chemistry: Halogen Bonding: Impact on Materials Chemistry and Life Sciences

Electric charge redistribution Halogen Bonding in the Gas-phase: A Comparison of the Iodine Bond in B···ICl and B···ICF 3 for simple Lewis Bases B J Grant Hill, Anthony C Legon, David P Tew and Nicholas R Walker, Topics in Current Chemistry: Halogen Bonding: Impact on Materials Chemistry and Life Sciences

Acknowledgements University of Newcastle Nick Walker Daniel Zaleski David Hird Dror Bittner University of Bristol Tony C. Legon David Tew Colin M. Western Halogen Bonding in the Gas-phase: A Comparison of the Iodine Bond in B···ICl and B···ICF 3 for simple Lewis Bases B J Grant Hill, Anthony C Legon, David P Tew and Nicholas R Walker Topics in Current Chemistry: Halogen Bonding: Impact on Materials Chemistry and Life Sciences