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# The advantages of the neon matrix to the vibrational study of van der Waals and hydrogen bonded molecular complexes

Benoît Tremblay, Pascale Soulard

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Benoît Tremblay, Pascale Soulard. The advantages of the neon matrix to the vibrational study of van der Waals and hydrogen bonded molecular complexes. 23rd International conference on "Horizons in hydrogen bond research", Sep 2019, Amsterdam, Netherlands. hal-04019252

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# The advantages of the neon matrix to the vibrational study of van der Waals and hydrogen bonded molecular complexes

B.Tremblay, P. Soulard

MONARIS, CNRS-Sorbonne Université, Paris FRANCE

## The complementarity between experiment and ab initio calculations allow to obtain new data on the n:m L<sub>n</sub>-(H<sub>2</sub>O)<sub>m</sub> complexes

### The neon matrix isolation apparatus coupled with FTIR

Absorption spectra collected on the same sample at 3 K from 80 to 9000 cm<sup>-1</sup> with a Bruker 120 FTIR spectrometer
(InSb, MCT, and bolometer detectors)

<figure><img src="image_2.png" /><figcaption>### Calculated binding energy (kJ/mol) of some 1:1 complexes</figcaption></figure>

<table><thead><tr><th rowspan="2"></th><th colspan="4">Van der Waals complexes</th><th colspan="3">Hydrogen bonded complexes</th></tr><tr><th>CO<sub>2</sub></th><th>OCS</th><th>N<sub>2</sub>O</th><th>H<sub>2</sub>O</th><th>H<sub>2</sub>O</th><th>(CH<sub>2</sub>)<sub>2</sub>O</th><th>diacetyl</th></tr></thead><tbody><tr><th>Ne</th><td>1.3</td><td>0.6</td><td>1</td><td>0.8</td><td></td><td></td><td></td></tr><tr><th>Ar</th><td>2.6</td><td>2.1</td><td>2.6</td><td>1.7</td><td></td><td></td><td></td></tr><tr><th>N<sub>2</sub></th><td>3.8</td><td>1.7</td><td>3.9</td><td>5.4</td><td></td><td></td><td></td></tr><tr><th>H<sub>2</sub>O</th><td>12.5</td><td>6.6</td><td>7.8</td><td>-</td><td>13</td><td>18.8</td><td>17.5</td></tr></tbody></table>

<table><caption>### Vibrational modes for the H<sub>2</sub>O and CO<sub>2</sub> molecules in gas phase and in N<sub>2</sub>, Ar, and Ne matrices</caption><thead><tr><th>Polarizability<br>(10<sup>-24</sup> cm<sup>3</sup>)</th><th><sup>1</sup>H<sub>2</sub></th><th><sup>14</sup>N<sub>2</sub></th><th><sup>20</sup>Ne</th><th><sup>40</sup>Ar</th></tr></thead><tbody><tr><td></td><td>0.80</td><td>1.71</td><td>0.40</td><td>1.64</td></tr></tbody></table>

<table><thead><tr><th rowspan="2"></th><th colspan="4">H<sub>2</sub>O modes</th><th colspan="4">CO<sub>2</sub> modes</th></tr><tr><th>ν<sub>1</sub></th><th>Δν<sup>a</sup></th><th>ν<sub>2</sub></th><th>Δν<sup>a</sup></th><th>ν<sub>3</sub></th><th>Δν<sup>a</sup></th><th>ν<sub>2</sub></th><th>Δν<sup>a</sup></th><th>ν<sub>3</sub></th><th>Δν<sup>a</sup></th></tr></thead><tbody><tr><th>gas</th><td>3656.7</td><td></td><td>1594.6</td><td></td><td>3755.8</td><td></td><td>667.4</td><td></td><td>2349.1</td><td></td></tr><tr><th>N<sub>2</sub></th><td>3634.9</td><td>21.8</td><td>1597.1</td><td>-2.5</td><td>3727.4</td><td>28.4</td><td>662.3</td><td>5.1</td><td>2349.0</td><td>0.1</td></tr><tr><th>Ar</th><td>3638.4</td><td>18.3</td><td>1588.7</td><td>5.9</td><td>3734.1</td><td>21.7</td><td>663.2</td><td>4.2</td><td>2339.4<sup>b</sup></td><td>9.7</td></tr><tr><th>Ne</th><td>3665.4</td><td>-8.7</td><td>1595.6</td><td>-0.8</td><td>3759.5</td><td>-3.7</td><td>668.0</td><td>-0.6</td><td>2347.8</td><td>1.3</td></tr></tbody></table>

<figure><img src="image_3.png" /></figure>

In matrix experiments, the perturbation induced by N<sub>2</sub> and Ar cannot be neglected for a weak binding complex and the use of less perturbing material like neon is essential

### Hydrated complexes formed with small molecules

- Identification of very weak binding complexes 1:1, 2:1, and 1:2

- Observation of different isomers for n:m complexes

- Observation of inter and intramolecular bands, overtones and combinations (v<sub>intra</sub>+v<sub>inter</sub> and v<sub>intra</sub>+v<sub>intra</sub>)

- Many deduced anharmonic coefficients providing data for anharmonic calculations

### Far infrared: Intermolecular region

<figure><img src="image_4.png" /></figure>

### Near infrared: overtones and combinations region

<figure><img src="image_5.png" /><figcaption>### Vibrational modes for the 1:1 H<sub>2</sub>O-CO<sub>2</sub> complex in gas phase and in N<sub>2</sub>, Ar, and Ne matrices</figcaption></figure>

<table><thead><tr><th rowspan="2"></th><th colspan="3">H<sub>2</sub>O modes</th><th colspan="2">CO<sub>2</sub> modes</th></tr><tr><th>Δν<sub>1</sub><sup>a</sup></th><th>Δν<sub>2</sub></th><th>Δν<sub>3</sub></th><th>Δν<sub>2</sub><sup>b</sup></th><th>Δν<sub>3</sub></th></tr></thead><tbody><tr><th>gas</th><td></td><td>-0.9</td><td></td><td></td><td></td></tr><tr><th>N<sub>2</sub></th><td>2.8</td><td>-1.4</td><td>1.9</td><td>-2.9</td><td>-2.0</td></tr><tr><th>Ar</th><td>0.4</td><td>-1.2</td><td>1.6</td><td>-4.8</td><td>-0.8</td></tr><tr><th>Ne</th><td>0.6</td><td>0.4</td><td>-0.8</td><td>-4.2</td><td>-0.4</td></tr><tr><th></th><td></td><td></td><td></td><td>9.3</td><td></td></tr></tbody></table>

<figure><img src="image_6.png" /><figcaption>### Vibrational shifts for molecule-H<sub>2</sub>O complexes in Ne matrices

#### Water modes</figcaption></figure>

<table><thead><tr><th rowspan="2"></th><th colspan="3">Van der Waals complexes</th><th colspan="3">Hydrogen bonded complexes</th></tr><tr><th>CO<sub>2</sub><br>-H<sub>2</sub>O</th><th>OCS<br>-H<sub>2</sub>O</th><th>N<sub>2</sub>O<br>-H<sub>2</sub>O</th><th>(H<sub>2</sub>O)<sub>2</sub><sup>b</sup></th><th>H<sub>2</sub>O-(CH<sub>2</sub>)<sub>2</sub>O</th><th>H<sub>2</sub>O-diacetyl<sup>c</sup></th></tr></thead><tbody><tr><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>1:1</td><td>ν<sub>1</sub></td><td>0.8</td><td>6.0<sup>a</sup><br>10.0</td><td>4.8, 74.9</td><td>129.6</td><td>71.2<br>97.2</td></tr><tr><td></td><td>ν<sub>2</sub></td><td>-0.4</td><td>-2.0<br>6.0</td><td>-3.6, -20.9</td><td>-9.7</td><td>-7.6</td></tr><tr><td></td><td>ν<sub>3</sub></td><td>0.7</td><td>7.0<br>9.0</td><td>-2.5, 27.3</td><td>42.8</td><td>28.3<br>34.4</td></tr><tr><td>2:1</td><td>ν<sub>1</sub></td><td>15</td><td>17.4</td><td>18.3</td><td></td><td></td></tr><tr><td></td><td>ν<sub>2</sub></td><td>1.0</td><td>2.2</td><td>-4.6</td><td></td><td></td></tr><tr><td></td><td>ν<sub>3</sub></td><td>9.0</td><td>20.0</td><td>7.6</td><td></td><td></td></tr><tr><td>1:2<sup>b</sup></td><td>ν<sub>1</sub></td><td>29.3, 21.6</td><td>19, 21</td><td>23.6, 18.7</td><td></td><td></td></tr><tr><td></td><td>ν<sub>2</sub></td><td>1.4, 3.2</td><td>2.0, 0.9</td><td>1.0, no</td><td></td><td></td></tr><tr><td></td><td>ν<sub>3</sub></td><td>24.0, no</td><td>22.9, 19.0</td><td>22.4, no</td><td></td><td></td></tr></tbody></table>

<figure><img src="image_7.png" /><figcaption>Structures for the OCS-H<sub>2</sub>O complexes</figcaption></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /><figcaption>Structure for the 1:1 N<sub>2</sub>O-H<sub>2</sub>O complex</figcaption></figure>

<figure><img src="image_10.png" /></figure>

<table><thead><tr><th rowspan="2"></th><th colspan="3">Van der Waals complexes</th></tr><tr><th>CO<sub>2</sub><sup>a</sup><br>-H<sub>2</sub>O</th><th>OCS<br>-H<sub>2</sub>O</th><th>N<sub>2</sub>O<br>-H<sub>2</sub>O</th></tr></thead><tbody><tr><td></td><td></td><td></td><td></td></tr><tr><td>1:1</td><td>ν<sub>1</sub></td><td>no</td><td>4.0<sup>b</sup><br>-7.0</td><td>2.4</td></tr><tr><td></td><td>ν<sub>2</sub></td><td>-4.0, 9.0</td><td>-7.5<br>-7.5</td><td>2.3</td></tr><tr><td></td><td>ν<sub>3</sub></td><td>-0.4</td><td>7.0<br>14.4</td><td>-8.9</td></tr><tr><td>2:1</td><td>ν<sub>1</sub></td><td>no</td><td>-5.3, 5.7</td><td>3.4</td></tr><tr><td></td><td>ν<sub>2</sub></td><td>-3.5, 4.5, 12.0</td><td>no</td><td>-2.8</td></tr><tr><td></td><td>ν<sub>3</sub></td><td>-1.5, -2.4</td><td>-2.1, 21.2</td><td>-12.6</td></tr><tr><td>1:2</td><td>ν<sub>1</sub></td><td>no</td><td>no</td><td>-17.4</td></tr><tr><td></td><td>ν<sub>2</sub></td><td>-2.6, 14.2</td><td>no</td><td>-6.0</td></tr><tr><td></td><td>ν<sub>3</sub></td><td>-2.4</td><td>19.8</td><td>-17.4</td></tr></tbody></table>

<footnote><sup>a</sup> Δν = v<sub>gas</sub> - v<sub>matrix</sub></footnote>

<footnote><sup>b</sup> In solid argon, the CO<sub>2</sub> v<sub>3</sub> band has two trapping sites</footnote>

<footnote><sup>a</sup> Δν = v<sub>monomer</sub> - v<sub>complex</sub> in the same matrix</footnote>

<footnote><sup>b</sup> the degeneracy of the v<sub>2</sub> mode is broken in the complex</footnote>

<footnote><sup>a</sup> the OCS-H<sub>2</sub>O complex has 2 isomers</footnote>

<footnote><sup>b</sup> the 1:2 and (H<sub>2</sub>O)<sub>2</sub> complexes have PA (proton acceptor) and PD (proton donor) vibrations</footnote>

<footnote><sup>c</sup> the diacetyl-H<sub>2</sub>O complex has 2 isomers</footnote>

<footnote><sup>a</sup> the degeneracy of the v<sub>2</sub> mode is broken in the complex</footnote>

<footnote><sup>b</sup> the 1:1 OCS-H<sub>2</sub>O complex has 2 isomers</footnote>

<footnote>REFERENCES: N<sub>2</sub>O-H<sub>2</sub>O: P. Soulard, M. Goubet, B. Tremblay. "First vibrational investigations of N<sub>2</sub>O-H<sub>2</sub>O, N<sub>2</sub>O-(H<sub>2</sub>O)<sub>2</sub>, and (N<sub>2</sub>O)<sub>2</sub>-H<sub>2</sub>O complexes from the far to the near-infrared spectral region by neon matrix isolation and ab initio calculations." *J. Chem. Phys.* **149**, 147311 (2018). OCS-H<sub>2</sub>O: P. Soulard, B. Madebène, B. Tremblay. "First infrared investigations of OCS-H<sub>2</sub>O, OCS-(H<sub>2</sub>O)<sub>2</sub>, and (OCS)<sub>2</sub>-H<sub>2</sub>O complexes isolated in solid neon: highlighting the presence of two isomers for OCS-H<sub>2</sub>O." *J. Chem. Phys.* **146**, 234303 (2017). Diacetyl-H<sub>2</sub>O: D. Dargent, B. Madebène, P. Soulard, B. Tremblay, E. L. Zins, M. E. Alikhani, P. Asselin. "Conformational landscape of the 1/1 diacetyl/water complex investigated by Infrared Spectroscopy and ab initio Calculations" *J. Phys. Chem. A* **121**, 88 (2017). CO<sub>2</sub>-H<sub>2</sub>O: P. Soulard, B. Tremblay. "Vibrational investigations of CO<sub>2</sub>-H<sub>2</sub>O, CO<sub>2</sub>- (H<sub>2</sub>O)<sub>2</sub>, and (CO<sub>2</sub>)<sub>2</sub>- H<sub>2</sub>O complexes isolated in solid neon." *J. Chem. Phys.* **143**, 224311 (2015). (H<sub>2</sub>O)<sub>2</sub>: Y. Bouteiller, B. Tremblay, J.-P. Perchard "The vibrational spectrum of the water dimer: Comparison between anharmonic ab initio calculations and neon matrix infrared data between 90 and 14 000 cm<sup>-1</sup>." *Chem. Phys.* **386**, 29 (2011). (CH<sub>2</sub>)<sub>2</sub>O-H<sub>2</sub>O: M. Cirtog, P. Asselin, P. Soulard, B. Tremblay, B. Madebène, M. E. Alikhani, R. Georges, A. Moudens, M. Goubet, T. R. Huet, O. Pirali, P. Roy. "The (CH<sub>2</sub>)<sub>2</sub>O-H<sub>2</sub>O hydrogen bonded complex. Ab initio calculations and FTIR spectroscopy from neon matrix and a new supersonic jet experiment coupled to the infrared AILES beamline of synchrotron SOLEIL." *J. Phys. Chem. A* **115**, 2523 (2011). (H<sub>2</sub>O)<sub>3</sub>: B. Tremblay, M. Madebène, M. E. Alikhani, J-P. Perchard "The vibrational spectrum of the water trimer: Comparison between anharmonic ab initio calculations and neon matrix infrared data between 11 000 and 90 cm<sup>-1</sup>." *Chem. Phys.* **378**, 27 (2010).</footnote>