A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY PABLO PINACHO SUSANA BLANCO JUAN CARLOS LÓPEZ Departamento de Química Física y Química Inorgánica Universidad de Valladolid, Valladolid SPAIN

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide.

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide. cis-peptide ~1% trans-peptide ~99% Ca-R R-Ca Ca-R FW-1:1c FW-1:1a 14% In proteins R-Ca Ca-R R-Ca FW-1:1b 42% in proteins

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide. cis-peptide ~1% trans-peptide ~99% Ca-R R-Ca Ca-R FW-1:1c FW-1:1a 14% In proteins R-Ca Ca-R R-Ca FW-1:1b 42% in proteins

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY We have analyzed the rotational spectra of formamidem-(H2O)n (m,n=1,2) clusters: 1) To characterize the different 1:1, 1:2, 2:1 conformers. FW-1:1a FW-1:1c FW-2:1 FW-1:2a FW-1:1b S. Blanco et al., JACS 128(37) 12111 (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY We have analyzed the rotational spectra of formamidem-(H2O)n (m,n=1,2) clusters: 1) To characterize the different 1:1, 1:2, 2:1 conformers. 2) To search for evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. 1.343 Å 1.350 Å rC-N = 1.361 Å shortening of HB lengths r(C-N) decrease S. Blanco et al., JACS 128(37) 12111 (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY In these contest we have analyzed the rotational spectra of formamide-(H2O)3 cluster 1) To characterize the different 1:1, 1:2, 2:1 conformers. 2) To search for evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. 1.341 Å 1.342 Å 1.343 Å 1.350 Å + rC-N = 1.361 Å shortening of HB lengths ? r(C-N) decrease ? S. Blanco et al., JACS 128(37) 12111 (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Formamide-(H2O)3 conformers FW1+FW2 Parameter(a) FW1-b ’b c FW2a-FW1b FW2a-FW1c FW2b-FW1a E/ cm-1 E/ kJmol-1   A/MHz B/MHz C/MHz

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Formamide-(H2O)3 conformers Cloud Parameter(a) C-top-u C-top-d C-back C-front E/ cm-1 E/ kJmol-1   A/MHz B/MHz C/MHz

supersonic jet - sample A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum A/D D/A I/O GP-IB Control pulso molecular generador pulsos 10 MHz ordenador PC n - 160 MHz 160 MHz FTMW spectrometer Fabry-Pérot cavity supersonic jet - sample MB-FTMW (4-16 GHz) Chem. Phys. 218 267 (1997); Chem. Phys. 119 880 (2003)

Liquid sample of formamide A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum Heated Nozzle Heater 50ºC (F)m ··· (H2O)n Carrier gas Ne 12 bar Ne + H2O H2O Liquid sample of formamide b.p. 210ºC

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum Gas pulse Diff. pump Rotatory Fabry-Pérot resonator Molecular beam MW pulse Polarization Detection MW field FT Time-domain Frequency domain

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum 6500 MHz 11500 MHz 9000 MHz FW-1:1c FW-1:2a FW-2:1 F FW-1:1a FW-1:1b

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum 6000 MHz 12000 MHz 9000 MHz

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Spectrum: inversion large amplitude motion or 11 kJ mol-1 16 kJ mol-1

rHf···Ow = 1.886 Å / rHw···Of = 1.810 Å A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. - rHf···Ow = 2.062 Å rHw···Of = 1.957 Å rHw···Ow = 1.791 Å rHf···Ow = 1.886 Å / rHw···Of = 1.810 Å - rOw···Of = 2.813 Å rOw···Ow = 2.774 Å rOw···Of = 2.728 Å shortening of HB lengths S. Blanco et al., JACS 128(37) 12111 (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY Evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. rC-N = 1.361 Å 1.350 Å 1.343 Å r(C-N) decrease S. Blanco et al., JACS 128(37) 12111 (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

A STUDY OF THE FORMAMIDE-(H2O)3 COMPLEX BY MICROWAVE SPECTROSCOPY PABLO PINACHO SUSANA BLANCO JUAN CARLOS LÓPEZ Departamento de Química Física y Química Inorgánica Universidad de Valladolid, Valladolid SPAIN