A STUDY OF THE FORMAMIDE-(H 2 O) 3 COMPLEX BY MICROWAVE SPECTROSCOPY

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1 PABLO PINACHO SUSANA BLANCO JUAN CARLOS LÓPEZ Departamento de Química Física y Química Inorgánica Universidad de Valladolid, Valladolid SPAIN

2 Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide.

3 Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide. trans-peptide ~99% cis-peptide ~1% R C FW 1:1c C R 14% In proteins R C C R FW 1:1a R C FW 1:1b C R 42% in proteins

4 Interactions between peptide groups and water may be modelled from the study of gas phase microsolvated clusters of simple molecules such as formamide. trans-peptide ~99% cis-peptide ~1% R C FW 1:1c C R 14% In proteins R C C R FW 1:1a R C FW 1:1b C R 42% in proteins

5 We have analyzed the rotational spectra of formamide m -(H 2 O) n (m,n=1,2) clusters: 1) To characterize the different 1:1, 1:2, 2:1 conformers. FW-1:1a FW-1:1b FW-1:1c FW-1:2a S. Blanco et al., JACS 128(37) (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

6 We have analyzed the rotational spectra of formamide m -(H 2 O) 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. r C N = Å r(c-n) decrease Å Å shortening of HB lengths S. Blanco et al., JACS 128(37) (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

7 In these contest we have analyzed the rotational spectra of formamide-(h 2 O) 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. + r C N = Å Å Å r(c-n) decrease shortening of HB lengths S. Blanco et al., JACS 128(37) (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)??

8 Formamide-(H 2 O) 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

9 Formamide-(H 2 O) 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

10 Spectrum generador pulsos 10 MHz Control pulso molecular MHz 10 MHz 160 MHz ordenador PC GP-IB I/O A/D D/A A/D FTMW spectrometer Fabry-Pérot cavity supersonic jet - sample Chem. Phys (1997); Chem. Phys (2003) MB-FTMW (4-16 GHz)

11 Spectrum Heated Nozzle Heater 50ºC Carrier gas Ne 12 bar H 2 O Ne + H 2 O (F) m (H 2 O) n Liquid sample of formamide b.p. 210ºC

12 Spectrum Gas pulse Polarization Fabry-Pérot resonator Molecular beam MW pulse MW field Detection Detection Diff. pump Rotatory FT Time-domain Frequency domain

13 Spectrum F FW-1:1a FW-1:1c FW-1:2a FW-1:1b 6500 MHz 9000 MHz MHz

14 Evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. r Hf Ow = Å r Hw Of = Å r Ow Of = Å r Hw Ow = Å r Hf Ow = Å / r Hw Of = Å r Ow Ow = Å r Ow Of = Å shortening of HB lengths S. Blanco et al., JACS 128(37) (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

15 Evidences of cooperative effects such as polarization enhanced or resonance assisted hydrogen bonding. r C N = Å Å Å r(c-n) decrease S. Blanco et al., JACS 128(37) (2006) S. Blanco et al., Ang. Chem. Int. Ed. (2016)

16 PABLO PINACHO SUSANA BLANCO JUAN CARLOS LÓPEZ Departamento de Química Física y Química Inorgánica Universidad de Valladolid, Valladolid SPAIN