Base-hydration-resolved hydrogen-bond networking dynamics: Quantum point compression

    Base-hydration-resolved hydrogen-bond networking dynamics: Point compression Yong Zhou, Danping Wu, Yinyan Gong, Zengsheng Ma, Yongli Huang, Xi Zhang, Chang Q Sun PII: DOI: Reference:

S0167-7322(16)31622-1 doi:10.1016/j.molliq.2016.09.052 MOLLIQ 6329

To appear in:

Journal of Molecular Liquids

Received date: Revised date: Accepted date:

20 June 2016 23 August 2016 19 September 2016

Please cite this article as: Yong Zhou, Danping Wu, Yinyan Gong, Zengsheng Ma, Yongli Huang, Xi Zhang, Chang Q Sun, Base-hydration-resolved hydrogenbond networking dynamics: Point compression, Journal of Molecular Liquids (2016), doi:10.1016/j.molliq.2016.09.052

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ACCEPTED MANUSCRIPT

Base-Hydration-Resolved Hydrogen-Bond Networking Dynamics: Point

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Compression

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Yong Zhou1,2, Danping Wu1, Yinyan Gong1, Zengsheng Ma2, Yongli Huang2, Xi Zhang3, Chang Q Sun4 Highlight

The :Ö:H- formation creates a Ö::Ö super hydrogen bond in the base hydration network



Effecting the same to mechanical compression, the Ö::Ö deforms its neighboring O:H-O bonds



Compression lengthens and softens the H-O bonds with cohesive energy reduction from 4.0 to 2.7 eV



The mono H-O bond of the :Ö:H- performs the same to the H-O dangling bonds featured at 3610 cm-1.

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

Abstract

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We show phonon spectrometrically that the unprecedented H2Ö::Ö:H- compression resolves the performance of the base solution networks with “:” being the electron lone pair of oxygen. At

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hydration, LiOH, NaOH, KOH molecules dissolve each into a :Ö:H- hydroxide and cations of Li+,

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Na+, and K+, respectively. The cations serve as charge centers to polarize the neighboring water molecules and raise the solution skin stress (or surface tension). The :Ö:H- tetrahedron adds,

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however, three lone pairs and one bonded H+ proton to the solution matrix, turning the initially 2N lone pairs into 2N+3 and the 2N bonded H+ into 2N+1 with an additional O2- anion. This hydration process breaks the conservation of the 2N lone pairs and protons with two extra lone pairs that only

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can form a H2Ö::Ö:H- super hydrogen bond (super-HB) with strong repulsivity. In addition to the H-O bond of the :Ö:H- featured at 3610 cm-1, the internal H2Ö::Ö:H- compression has an identical effect of mechanical compression, shortening the O:H nonbonds and stiffening their phonons from below 200 cm-1 to the above. Meanwhile, compression lengthens the network H-O bonds and softens their phonons from above 3150 cm-1 to below. The network H-O bonds elongation decrease their energy from ~4.0 to ~ 2.7 eV at hydration, which heats the solution as one often observes. The

1

Institute of Coordination Bond Metrology and Engineering, College of Materials Science and Engineering, China Jiliang University, Hangzhou

310018, China 2

Key Laboratory of Low-Dimensional Materials and Application Technology (Ministry of Education) and School of Materials Science and Engineering,

Xiangtan University, Hunan 411105, China 3

Institute of Nanosurface Science and Engineering, Shenzhen University, Shenzhen 518060, China

4

NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore 1

ACCEPTED MANUSCRIPT H2Ö::Ö:H- super-HB compressor and the alkali cation polarisor form the keys to the base hydration networks and the properties.

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Keywords: Base Dissolution and Hydration; Super Hydrogen Bond; Point Compression; Hydrogen

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Bond Relaxation

Table of Contents

Base-Hydration-Resolved Hydrogen-Bond Networking Dynamics: Point Compression ......... 1 Introduction .................................................................................................................................... 3

2

Principles ......................................................................................................................................... 6

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1

Water structure and HB cooperativity: 2N conservation ......................................................... 6

2.2

Differential phonon spectrometrics .......................................................................................... 8

2.3

Ö::Ö point compressor: super hydrogen bond ..................................................................... 9

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2.1

Experiment method ....................................................................................................................... 10

4

Results and discussion .................................................................................................................. 10

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4.1

Ö::Ö compression induced phonon relaxation .................................................................. 10

4.2

Network H-O bond energy loss ............................................................................................. 13

4.3

Skin stress or surface tension construction ............................................................................ 14

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3

Conclusion ..................................................................................................................................... 15

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Acknowledgement ............................................................................................................................... 15

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ACCEPTED MANUSCRIPT 1

Introduction

LiOH, NaOH, and KOH base molecular hydration has striking implications to numerous subject

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areas of organic and inorganic chemistry. However, the mechanism behind observations remains unclear despite intensive spectroscopic investigations using various spectroscopic technologies and

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quantum computations. For instances, the sum frequency generation (SFG) provides information on the sublayer-resolved dipole orientation, or the skin dielectrics, at the air-solution interface [1, 2], and the time-domain two-dimensional infrared absorption (t-2DIR) reveals the solute or water

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molecular dynamics in terms of phonon lifetime and the viscosity of the solutions [3, 4]. The performance of the base solution is in so far best explained in terms of “structural diffusion” or

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“solute delocalization” [1-4] with little attention to the relaxation dynamics of the hydrogen bonding (HB or O:H-O with “:” being the electron lone pairs on oxygen) networks or the solution matrix. It

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remains puzzling how the OH- hydroxide functionalizes the solvent H2O molecules and how the OH-

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determines the functionality of the solution matrix [5-7].

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Studies of NaOH hydration in bulk water [8] and water clusters [9] revealed two processes of vibration relaxations. One is the rapid processes on 200  50 fs time scales (corresponds to slow H-O bond vibration) and the other slower is slow dynamics on 1–2 ps time scales (to fast H-O bond The

vibrational

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vibration).

energy

exchange

between

the

bulk-like

water

and

the

hydroxide-associated water takes place in ∼200 fs scales. The strong nonlinear coupling between intra- and inter-molecular vibrations and the non-adiabatic vibrational relaxation could be responsible for the rapid dynamics of phonon relaxation. The phonon frequency blueshift is associated with a longer phonon lifetime, a slower molecular dynamics, a higher viscosity of the solution, due to stronger polarization [10]. For instance, an addition of 7M-NaOH solute could fold the lifetime and increase four-fold the viscosity of the solution compared with pure water [8]. On the other hand, base NaOH hydration broadens the IR spectra with an association of redshift transiting the phonon abundance from above 3000 cm-1 to its below [9]. The free and hydrogen bonded OHstretches the OH- -(H2O)4,5 cluster phonon band substantially [11].

3

ACCEPTED MANUSCRIPT In contrast, 1 M salt KX (X = I, Br, Cl, and F) hydration [12] raises the H-O stretching vibration frequency (H) in the Hofmeister series order of anion size [13, 14] - larger ions of less electronegative stiffen the H more significantly [15, 16]. Molecular dynamics (MD) simulations and

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t-2DIR measurements [17] unveiled that an addition of 5% NaBr to the D2O/H2O mixture solution

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raises the O-D vibration wavenumber from ~2509 to ~2539 cm-1 and the amount of the shift changes

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with the H2O/Br- molecular ratio (8, 16, 32). The anion interaction with water molecules prolongs the lifetime of molecular dynamics [18], and enhances the viscosity of the solution. Salt hydration shifts the H-O peak from 3200 to 3450 cm-1 and narrows the H-O phonon band. The blue shift of the H-O

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band indicates the stiffening of the H-O bond and the slow molecular dynamics by salt hydration, as the phonon frequency shift is proportional to the square root of bond stiffness; the narrow of the

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full-width-at-half-maximum (FWHM) of the specific peak indicates the higher structure order of

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water molecules [10, 14].

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Earlier Raman studies on temperature and pressure dependence of liquid water [19-21] and the concentration dependence of electrolyte ZX solutions (Z = Li, Na, K and X = F, Cl, Br and I) [21, 22]

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revealed the same trend of our observations [14-16] - compression downshifts while heating upshifts the H-O phonon band [10, 22]; chloride, bromide and iodide hydration shifts the O-H band upwardly [14, 23]. However, hydroxide (base) hydration shifts the H-O band downwardly associated w2ith a

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sharp peak at 3610 cm-1. These observations are usually explained as the weakening of the surrounding O:H nonbond (structure breakers) due to Cl-, Br-, and I- ions interactions or strengthening the O:H (structure makers) due to OH- involvement [24-26]. Unfortunately, little has yet been known how the O:H-O bond network evolve at hydration. In fact, O:H-O bond phonon cooperative shifts fingerprint directly the relaxation of the HB segmental lengths and their cohesive energies over the entire network subjecting to spectroscopy measurements [10, 27].

On the other hand, the hydroxide (OH-) mobility in solutions has rarely been noted since 1900’s when Svante Arrhenius [28], Brønsted–Lowry [29, 30], and Gilbert Lewis [31] defined the base compounds dissolution in terms of OH- or electron pair donation. The century-old notion regarded an OH- as a H2O molecule missing an H+ proton, and such a ‘proton hole’ transport mechanism could 4

ACCEPTED MANUSCRIPT be deduced from the H3O+ of an excess proton by simply reversing HB polarities. The hydroxide is ever suggested highly active in solutions in comparison to Z+ and X- ions that serve each as a point charge centre of polarization [14-16]. This OH- behaviour was explained in terms of ‘structural

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diffusive evolution’- hydration complexes interconversion driven by the ionic solvation-shell fluctuations. First-principles calculations [3] suggested that an interplay between the hydration

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complexes and nuclear quantum effects determines the OH- transport dynamics with omitting the response of the HB network to the base solutes.

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In fact, a LiOH, NaOH, KOH base molecule dissolves into a Li+, Na+, K+ cation and an OHhydroxide in common when they are hydrated, which governs the performance of the HB network of

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the solution. The alkali cation combines with an X- anion to form an alkali salt molecule, which has been used to neutralize the Cl- anions in the drinking water by adding NaHCO3 (soda) for the

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reaction:

Cl- + H2O + NaHCO3  NaCl + CO2 + OH- + H2O

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(1)

This process turns the Cl- rich water into a salt (Na+ + Cl-) and a base (OH-) solution. Understanding the base solute-solvent interaction also implicates to some drugs whose molecules are sided with OH-

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hydroxides, which functionalize cells through solution-protein interactions. Unfortunately, such knowledge was prevented due to the uncertainty of water structure and the unclear dynamics of the HB relaxation in the base hydration networks.

The objective of this communication is to show that the latest knowledge of the HB cooperativity in water [5, 10, 32] has allowed us to resolve this HB network mystery spectrometrically. Complementing the SFG and the t-2DIR spectroscopies, we employed the Raman differential phonon spectrometrics (DPS) [33] to examine the effect of base hydration on the HB network relaxation from the perspective of H-O bond stiffness, molecular fluctuation dynamics, and phonon population transition. We found that the :Ö:H- hydroxide retains its tetrahedral configuration to interact with one of its tetrahedral neighbors through H2Ö::Ö:H- super hydrogen bond interaction. 5

ACCEPTED MANUSCRIPT The strong repulsivity of the H2Ö::Ö:H- makes it a point compressor that has the same effect to mechanical compression on the HB length and stiffness relaxation. The discovery of the H2Ö::Ö:H- point compressor and the alkali cation point polarisor could form important impact to

Principles

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2

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the understanding of HB relaxation dynamics and functionalities of base solutions.

2.1 Water structure and HB cooperativity: 2N conservation

When reacting with atoms of electropositive elements, an O atom captures an electron from each of

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its two nearest neighbors and then hybridizes its two sp orbits with creation of four directional orbits [34]. The O bonds to its four nearest neighbors with two nonbonding lone pairs and two bonding

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electron pairs. Water is a typical case that exists in all the gases, liquids, and solid phases in broad ranges of pressure and temperature [35]. For a water specimen contains N oxygen atoms, there will

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be 2N electron lone pairs and 2N bonded H+ protons. These 2N numbers conserve in its liquid or

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solid forms, which only allows for forming the O:H-O configuration in the network of water and ice, even though in the superionic state (H3O+:OH-) and the Xth phase of ice. The superionic states only

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exists at 2 TPa and 2000 K [36]. Featured with the identical O:H and the H-O length, the Xth phase of ice exists at  60 GPa pressure over all temperatures [32, 37, 38]. The Xth phase of salt solutions also

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exist at relatively higher pressures [39-42].

As a strongly correlated and fluctuating system, water prefers the statistic mean of the tetrahedrally-coordinated structure with strong fluctuation in the bond angle and segmental lngths. However, sharing the same geometry, the segmental lengths and energies of the O:H-O bonds in the skin up to three molecular layers is different from those in the bulk [10, 32]. The skin O:H nonbond is longer and the H-O bond is shorter than they are in the bulk, as a result of molecular undercoordination. The skin bulk water, nanodroplets, and nanobubbles are thermally more stable, mechanical stronger with ≤0.75 mass density [43-46].

Figure 1a shows the ideal unit cell for water and ice, which contains two H2O molecules and four oriented HBs with the pairing dots representing the electron lone pairs “:” on oxygen [47]. Figure 1b 6

ACCEPTED MANUSCRIPT shows the Ex-dx potential paths of the segmented O:H-O bond under mechanical compression [48] (x = L for the O:H and x = H for the H-O segment). A Lagrangian solution of the HB oscillator pair motion dynamics has transformed the measured HB segmental lengths and vibration frequencies (dx,

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x) [48] at each pressure of compression into the respective force constant and binding energy (kx, Ex)

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and hence derived the potential paths for the HB under compression [32].

The HB consists the weaker O:H intermolecular nonbond (~0.1 eV) and the stronger H-O intramolecular covalent bond (~4.0 eV) with asymmetrical and short-range interactions and coupled

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by the Coulomb repulsion between electron pairs on adjacent oxygen ions [49]. The long-range interactions are averaged away as background. The HB is associated with the electron lone pairs

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presenting not only in H2O but also in the HF (three lone pairs)[50] and NH3(one lone pair) or their

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mixtures, such as N:H-C and F:H-C [51-54].

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The HB segmental disparity [55], cooperativity [56], and the O-O repulsivity allow the segmented HB to relax in a “master-slave” fashion under excitation –both O ions dislocate along the HB in the

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same direction but by different extents. The stiffer H-O bond always relaxes less than the softer O:H nonbond with respect to the coordination origin of H+. The HB containing angle  relaxation contributes insignificantly to the segmental length and energy that dictate the detectable properties

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such as the skin stress (traditionally called surface tension), hydrophobicity, phonon frequency, and thermal stability [10].

The HB only relaxes in two ways– elongation or contraction. Liquid heating and molecular undercoordination lengthen the HB but compression shortens the HB associated with nonbonding electron polarization (mechanical compression [57], salt hydration [15, 16, 57] and molecular undercoordination [58]) or depolarization (heating) [22, 32].

Figure 1b indicates that the O:H nonbond contracts more than the H-O elongates along the potential paths towards HB segmental length symmetrization [37, 59]. The HB asymmetrical cooperative relaxation arises intrinsically from the O-O Coulomb coupling and the segmental strength disparity 7

ACCEPTED MANUSCRIPT (EH/EL ~ 4.0/0.1 eV), which is irrespective to structure phase or the nature of the external stimulus. The external stimulus determines the direction of the HB relaxation and polarization, as just

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mentioned.

(b)

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(a)

(d)

120

180 -1 L / cm

240

I / a.u.

0.77 1.03 1.33

300

2800

3000

3200 3400 -1 H / cm

3600

3800

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0.77 1.03 1.33

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I / a.u.

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(c)

Figure 1. (a) A water unit cell containing two H2O molecules and four oriented HBs with the pairing dots representing the lone pairs on oxygen. (b) Potential paths for the HB of 80 K ice under pressure (r. to l.: P changes from 0 to 60 GPa in 5 GPa step size)[48]. (c, d) The differential phonon spectra revealed that compression stiffens the L but softens the H of the O:H-O bond of liquid water[60].

2.2 Differential phonon spectrometrics Raman phonon frequency shift x probes the HB stiffness relaxation that depends on the segmental length dx and energy Ex, irrespective of the nature of the source of stimulation or the probing photon energy [32, 59]. x is correlated to the segmental stiffness in terms of length dx and energy Ex by:

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ACCEPTED MANUSCRIPT x   2πc 

1

 kx  kC  x 

Ex x / d x

(2)

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The O:H nonbond is characterized by the stretching vibration frequency around 200 cm-1 and the

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H-O intramolecular bond by ~3200 cm-1 in bulk water. The kx and kC are the force constants or the second differentials of the intra/inter molecular interaction (x = H, L for H-O and O:H, respectively)

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and O-O repulsive potentials. The x also varies with the reduced mass x of the specific x

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oscillator.

If one segment of the HB turns to be shorter, it will become stiffer, and its characteristic phonon

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frequency undergoes a blueshift; the other segment of the HB will react oppositely to stimulation. Therefore, Raman spectroscopy resolves unambiguously the effect of any perturbation to the HB

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solution network [61].

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To examine the phonon relaxation dynamics due to base hydration, we were focused on the difference between the measured solution spectra and the referential spectrum measured from

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deionized water. All spectra were background corrected and peak area normalized prior to this differentiation. This process of experimental spectra distills the phonon abundance net gain from the

spectra.

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net loss by removing the commonly shared area, without needing the tedious decomposition of the

The DPS (difference between two spectra) for the compressed liquid water, shown in Figure 1(c, d) confirmed that the applied pressure stiffens the L from 170 to 200 cm-1 and above, and meanwhile softens the H from 3450 to 3100 cm-1 for liquid water. Features centered at 80 cm-1 result from polarization due to mechanical compression.

2.3 Ö::Ö point compressor: super hydrogen bond

One can imagine what will happen if replace the central H2O of the structure unit cell in Figure 1a with a :Ö:H- hydroxide, see Figure 2a inset. This replacement increases the 2N lone pairs of the water 9

ACCEPTED MANUSCRIPT to 2N+1 and lowers the number of H+ protons from 2N to 2N-1. The excessive two lone pairs can only form the internal Ö::Ö point compressor between the central :Ö:H- hydroxide and one of its four H2Ö: neighbors. This unaware Ö::Ö configuration may be named as a super hydrogen bond

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with internal strong repulsion. This Ö::Ö pertaining to each hydroxide is expected to have at least

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the same effect of mechanical compression on the HB network relaxation. Experiment method

Raman measurements of 150 L deionised water and aqueous solutions injected into a silica stage

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were conducted using the confocal micro Raman spectrometer (Renishaw inVia) with a 532-nm He–Ne laser as the light source. The measurements were conducted at the ambient pressure and 298

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K temperature. The phonon frequency range was set to 50–4000 cm-1. Each spectrum is an accumulation of four scans, and each scan took 30 seconds. A 50× long-working-distance objective

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(Leica) was used to focus laser light onto the sample and collect the scatted light. Signal was

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detected by a thermoelectric cooled (-70ºC) standard charge-coupled array detector.

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High purity (> 90%) bases were purchased from Aladdin Co. Deionized water (18.2 MΩ•cm resistivity) produced by a HITECH laboratory water purification system was used for all the measurements. The contact angles were estimated with a drop sharp analysis system (Krüss GmbH,

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Germany) by ion solution droplets dropping onto the glass surface at ambient temperature. The value reported was the average of more than 10 measurements made at different position of the glass surface.

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Results and discussion

4.1 Ö::Ö compression induced phonon relaxation In order to confirm the effect of Ö::Ö point compression, we examined the base type and concentration effect on the phonon frequency shift of the LiOH, NaOH, KOH hydration networks. Figure 2(a-d) confirmed that LiOH, NaOH, KOH hydration indeed softens the H, indicating that the H-O bond turns to be longer and softer. The x is less sensitive to the type of the alkali cations of the same concentration. The DPS in Figure 2(e, f) refined that the H moves from above 3100 cm-1 to its below and that the L shifts from below 220 cm-1 to its above. It has thus justified that the Ö::Ö 10

ACCEPTED MANUSCRIPT compressors have the same effect of mechanical compression on shortening and stiffening the O:H nonbond and lengthening and softening the H-O bond.

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Different from the meno9cal compression, the Ö::Ö compressors result in the 3610 cm-1 sharp

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peak whose intensity is proportional to the concentration of the solutes. This 3610 cm-1 spectral

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feature is the same to the skin dangling H-O bond. This observation indicates that the single H-O bond pertaining to the :Ö:H- hydroxide has the same identity of the H-O dangling bond - shorter and

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stronger than those between H2O molecules in bulk water.

Most strikingly, the L for the low LiOH, NaOH, KOH concentration duplicates the L feature of

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the mechanically compressed water – blue shift. Spectral feature consistence between Figure 1(c, d) and Figure 2(e, f) evidences the Ö::Ö point compression of the solution HB networks, and the

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strength of point compressor is more pronounced than the applied pressure on the HB of the

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networks for water and solutions [62].

(b)

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(a)

H O 2

LiOH/H2O

Intensity / a.u.

LiOH

NaOH KOH

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Intensity / a.u.

0.08

100 200 300 400 2800 3200 3600 -1 Raman shift / cm NaOH/H2O

Intensity / a.u.

298K H 2O

0 0.02 0.04 0.06 0.08 0.10

Exp Fit Bulk Skin O-H

2800

3000

3200 3400 -1 H(cm )

100 200 300 400 2800 3200 3600 -1 Raman shift / cm

3600

3800

(d) KOH/H2O

Intensity / a.u.

(c)

0 0.02 0.04 0.06 0.08

0 0.02 0.04 0.06 0.08 0.10

100 200 300 400 2800 3200 3600 -1 Raman shift / cm

100 200 300 400 2800 3200 3600 -1 Raman shift / cm

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(e)

(f)

20

40

LiOH NaOH KOH

-40

-80 240 -1 L / cm

320

400

2400

2800

3200 -1 H / cm

LiOH NaOH KOH

3600

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-60 80

-40

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0

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I / a.u.

I / a.u.

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Figure 2. Room-temperature full-scan Raman spectra for (a) the LiOH/H2O, NaOH/H2O, KOH/H2O = 0.08

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solutions and for the (b) LiOH, (c) NaOH and, (d) KOH dependence. An alteration of the H2O in the cell center with a :Ö:H- (see unit cell in the inset (a)) creates the unique Ö::Ö point compressor, which relaxes the hydration network and the phonon frequencies. Inset (c) decomposes the H-O phonon peak into

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components for the bulk (3200 cm-1), skin (3450 cm-1), and H-O radical (3610 cm-1) of deionized water. The

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DPS (e, f) of the LiOH, NaOH, KOH at 0.08 concentration revealed consistently the effect of Ö::Ö super-HB compression on the O:H stiffening and the H-O bond softening in addition to the identical 3610

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cm-1 wavenumber for the single H-O bond and the skin dangling H-O bond.

-20 -40

0.02 0.04 0.06 0.08

-60 80

40

0 I / a.u.

I / a.u.

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(b)

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(a) 20

-40

0.02 0.04 0.06 0.08

-80 160

240 -1 L / cm

320

400

2400

12

2800 3200 -1 H / cm

3600

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(c) 20

(d)

40

0.02 0.04 0.06 0.08 0.10

-60 80

-80

160

240 -1 L / cm

320

400

(e) 20

2400

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3200 -1 H / cm

0.02 0.04 0.06 0.08 0.10

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I / a.u.

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240 -1 L / cm

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0.02 0.04 0.06 0.08 0.10

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3200 -1 H / cm

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0.02 0.04 0.06 0.08 0.10

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I / a.u.

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0

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I / a.u.

I / a.u.

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Figure 3. The refined DPS for (a, b) LiOH, (c, d) NaOH and (e, f) KOH hydration networks as a function of molecular concentration, showing the (a, c, e) O:H nonbonds stiffening and the (b, d, f) network H-O bonds

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softening and the OH- single H-O bond stiffening.

4.2 Network H-O bond energy loss The refined DPS in Figure 3 further confirmed the effect of the Ö::Ö point compressors on the LiOH, NaOH, KOH hydration networks. The number of the deformed HB contributes to the transition of the segmental stiffness, fluctuation dynamics, and the population of the respective phonons. However, the DPS can hardly resolve the polarization effect of the alkali cations because of the point compression compensates the polarization that elongates the local O:H in its hydration shell.

With the documented values of (dH, EH, H) = (1.0 Ǻ, 4.0 eV, 3200 cm-1) for bulk water [47], one can estimate the H-O bond cohesive energy (1.05 Ǻ, 2.70 eV, 2500 cm-1) in base solutions using 13

ACCEPTED MANUSCRIPT correlation (2):

2

E d2     2500  E2  1 2 H2  1   4.0  (1.05/1.0)2    2.70 eV d H1  2   3200  2

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4.3 Skin stress or surface tension construction

Figure 4 shows that the contact angle between the LiOH, NaOH, KOH solution droplet and a glass substrate increases with the solution concentration. The same concentration trend of the contact angle

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suggests that the LiOH, NaOH, KOH constructs the skin stress through polarization by both cation polarizors and Ö::Ö compressors. Cations form each a charge center that clusters, stretches, and

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polarizes the neighboring H2O molecules [15, 16, 57]. However, DPS can hardly resolve the joint yet

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LiOH NaOH KOH

80 76

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92

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Contact Angle / degree

opposite effects of polarization and compression on the O:H relaxation.

0.00 0.02 0.04 0.06 0.08 0.10 Mole Fraction / %

Figure 4. The contact angle between LiOH, NaOH, KOH solutions and a glass surface as a function of the solution concentration.

It becomes clear now why the solution becomes hot when the base molecules are hydrated, as one often observes. The H-O bond elongation losses its cohesive energy from 4.0 to 2.7 eV, which turns to be Joule heat to warm up the solution. According to the present HB relaxation premise and recent observations [4], the longer H-O bond in the hydration network shortens the phonon life time as detected as 2DIR fast relaxation [8, 9]; the slow dynamics arises from the shorter H-O bond of the :Ö:H- hydroxide. The elongated H-O bond broadens its phonon band towards the lower frequency end, 3100 cm-1 and below. 14

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Conclusion

The DPS strategy has enabled us to confirm that the unprecedented H2Ö::Ö:H- point compressors

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govern the performance of the base solutions. In addition to creation of the H-O bond radical

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featured at 3610 cm-1, the internal H2Ö::Ö:H- point compression has the same effect to the applied

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pressure on the O:H-O bond network relaxation. No matter it is internal or external, the compression shortens the O:H nonbonds and stiffen their phonons from below 200 cm-1 to the above, and meanwhile, lengthen the H-O bond and transit their phonons from above 3150 cm-1 to below. The

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energy loss of the H-O bond from ~4.0 to ~ 2.7 eV at hydration heats the solution as one often observes. The Li+, Na+, K+ cations create electric fields that polarize the neighboring water

MA

molecules. Both the cation polarisors and the O::O super-HB compressors raise the skin stress of the base solutions. The discovery of the intrinsic O::O point compressor and its effect on the

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nature of the solute-solvent-functionality of the base solutions shall have important impact to the

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understanding of performance for base solution and beyond.

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Acknowledgement

Financial supports from National Natural Science Foundation (Nos. 11502223, 21273191) of China

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are gratefully acknowledged.

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ACCEPTED MANUSCRIPT References

7.

8. 9.

10. 11.

12. 13.

14.

15.

16. 17.

T

IP

SC R

NU

6.

MA

5.

D

4.

TE

3.

CE P

2.

Y.R. Shen and V. Ostroverkhov, Sum-frequency vibrational spectroscopy on water interfaces: Polar orientation of water molecules at interfaces. Chem. Rev., 106(4): 1140-1154, (2006). H. Chen, W. Gan, B.-h. Wu, D. Wu, Y. Guo, and H.-f. Wang, Determination of structure and energetics for Gibbs surface adsorption layers of binary liquid mixture 1. Acetone+ water. The Journal of Physical Chemistry B, 109(16): 8053-8063, (2005). M.E. Tuckerman, D. Marx, and M. Parrinello, The nature and transport mechanism of hydrated hydroxide ions in aqueous solution. Nature, 417(6892): 925-929, (2002). S.T. van der Post, C.S. Hsieh, M. Okuno, Y. Nagata, H.J. Bakker, M. Bonn, and J. Hunger, Strong frequency dependence of vibrational relaxation in bulk and surface water reveals sub-picosecond structural heterogeneity. Nat Commun, 6: 8384, (2015). K. Dong and S. Zhang, Hydrogen bonds: a structural insight into ionic liquids. Chem.-Eur. J., 18(10): 2748-2761, (2012). K. Dong, S. Zhang, and Q. Wang, A new class of ion-ion interaction: Z-bond. Science China Chemistry, 58(3): 495-500, (2015). D.B. Wong, C.H. Giammanco, E.E. Fenn, and M.D. Fayer, Dynamics of Isolated Water Molecules in a Sea of Ions in a Room Temperature Ionic Liquid. J. Phys. Chem. B, 117(2): 623-635, (2013). A. Mandal and A. Tokmakoff, Vibrational dynamics of aqueous hydroxide solutions probed using broadband 2DIR spectroscopy. J. Chem. Phys., 143(19): 194501, (2015). A. Mandal, K. Ramasesha, L. De Marco, and A. Tokmakoff, Collective vibrations of water-solvated hydroxide ions investigated with broadband 2DIR spectroscopy. J. Chem. Phys., 140(20): 204508, (2014). C.Q. Sun and Y. Sun, The Attribute of Water: Single Notion, Multiple Myths. Springer Ser. Chem. Phys. Vol. 113. 2016, Heidelberg: Springer-Verlag. 494 pp. C. Chaudhuri, Y.-S. Wang, J. Jiang, Y. Lee, H.-C. Chang, and G. Niedner-Schatteburg, Infrared spectra and isomeric structures of hydroxide ion-water clusters OH-(H2O) 1-5: a comparison with H3O (H2O) 1-5. Mol. Phys., 99(14): 1161-1173, (2001). J.D. Smith, R.J. Saykally, and P.L. Geissler, The Effects of Dissolved Halide Anions on Hydrogen Bonding in Liquid Water. Journal of America Chemical Society, 129: 13847-13856, (2007). F. Hofmeister, Concerning regularities in the protein-precipitating effects of salts and the relationship of these effects to the physiological behaviour of salts. Arch. Exp. Pathol. Pharmacol, 24: 247-260, (1888). X. Zhang, T. Yan, Y. Huang, Z. Ma, X. Liu, B. Zou, and C.Q. Sun, Mediating relaxation and polarization of hydrogen-bonds in water by NaCl salting and heating. PCCP, 16(45): 24666-24671, (2014). Y. Gong, Y. Zhou, H. Wu, D. Wu, Y. Huang, and C.Q. Sun, Raman spectroscopy of alkali halide hydration: hydrogen bond relaxation and polarization. Journal of Raman Spectroscopy: DOI: 10.1002/jrs.4963, (2016). Y. Zhou, Y. Huang, Z. Ma, Y. Gong, X. Zhang, Y. Sun, and C.Q. Sun, Water molecular structure-order in the NaX hydration shells (X= F, Cl, Br, I). J. Mol. Liq., 221: 788-797, (2016). S. Park and M.D. Fayer, Hydrogen bond dynamics in aqueous NaBr solutions. Proc. Natl. Acad.

AC

1.

16

ACCEPTED MANUSCRIPT

24. 25. 26. 27. 28. 29. 30.

31. 32.

33. 34. 35.

36. 37. 38.

T

IP

SC R

NU

23.

MA

22.

D

21.

TE

20.

CE P

19.

AC

18.

Sci. U.S.A., 104(43): 16731-8, (2007). R. Yuan, C. Yan, A. Tamimi, and M.D. Fayer, Molecular Anion Hydrogen Bonding Dynamics in Aqueous Solution. The Journal of Physical Chemistry B, 119(42): 13407-13415, (2015). P.C. Cross, J. Burnham, and P.A. Leighton, The Raman spectrum and the structure of water. J. Am. Chem. Soc., 59: 1134-1147, (1937). G.E. Walrafen, Raman Spectral Studies of the Effects of Temperature on Water Structure. J. Chem. Phys., 47(1): 114-126, (1967). Z. Wang, Y. Pang, and D.D. Dlott, Hydrogen-Bond Disruption by Vibrational Excitations in Water. J. Phys. Chem. A, 111(17): 3196-3208, (2007). C.Q. Sun, X. Zhang, X. Fu, W. Zheng, J.-l. Kuo, Y. Zhou, Z. Shen, and J. Zhou, Density and phonon-stiffness anomalies of water and ice in the full temperature range. J. Phys. Chem. Lett., 4: 3238-3244, (2013). Q. Zeng, Y. Zhou, W. Kai, Y. Gong, Y. Zhou, Y. Huang, C.Q. Sun, and B. Zou, Compression icing of room-temperature NaX solutions (X = F, Cl, Br, I). PCCP, DOI: 10.1039/C6CP00648E, (2016). W.M. Cox and J.H. Wolfenden, The Viscosity of Strong Electrolytes Measured by a Differential Method. Proc Roy Soc London A, 145(855): 475-488, (1934). P. Ball and J.E. Hallsworth, Water structure and chaotropicity: their uses, abuses and biological implications. Phys. Chem. Chem. Phys., 17(13): 8297-305, (2015). K.D. Collins and M.W. Washabaugh, The Hofmeister effect and the behaviour of water at interfaces. Quarterly Reviews of Biophysics, 18(04): 323-422, (1985). C.Q. Sun, Relaxation of the Chemical Bond. Springer Ser. Chem. Phys. Vol. 108. 2014, Heidelberg: Springer-Verlag. 807 pp. S. Arrhenius, Development of the theory of electrolytic Dissociation. Nobel Lecture, (1903). J. Brönsted, Part III. Neutral salt and activity effects. The theory of acid and basic catalysis. Trans. Faraday Society, 24: 630-640, (1928). T.M. Lowry and I.J. Faulkner, CCCXCIX.—Studies of dynamic isomerism. Part XX. Amphoteric solvents as catalysts for the mutarotation of the sugars. Journal of the Chemical Society, Transactions, 127: 2883-2887, (1925). G.N. Lewis, Acids and bases. Journal of the Franklin Institute, 226(3): 293-313, (1938). Y.L. Huang, X. Zhang, Z.S. Ma, Y.C. Zhou, W.T. Zheng, J. Zhou, and C.Q. Sun, Hydrogen-bond relaxation dynamics: Resolving mysteries of water ice. Coord. Chem. Rev., 285: 109-165, (2015). X.J. Liu, M.L. Bo, X. Zhang, L.T. Li, Y.G. Nie, H. TIan, Y. Sun, S. Xu, Y. Wang, W. Zheng, and C.Q. Sun, Coordination-resolved electron spectrometrics. Chem. Rev., 115(14): 6746-6810, (2015). C.Q. Sun, Oxidation electronics: bond-band-barrier correlation and its applications. Prog. Mater Sci., 48(6): 521-685, (2003). X. Zhang, P. Sun, Y. Huang, T. Yan, Z. Ma, X. Liu, B. Zou, J. Zhou, W. Zheng, and C.Q. Sun, Water’s phase diagram: from the notion of thermodynamics to hydrogen-bond cooperativity. Prog. Solid State Chem., 43: 71-81, (2015). Y. Wang, H. Liu, J. Lv, L. Zhu, H. Wang, and Y. Ma, High pressure partially ionic phase of water ice. Nature communications, 2: 563, (2011). M. Benoit, D. Marx, and M. Parrinello, Tunnelling and zero-point motion in high-pressure ice. Nature, 392(6673): 258-261, (1998). J. Teixeira, High-pressure physics - The double identity of ice X. Nature, 392(6673): 232-233, 17

ACCEPTED MANUSCRIPT

45.

46. 47.

48. 49.

50.

51.

52.

53. 54.

55.

T

IP

SC R

NU

44.

MA

43.

D

42.

TE

41.

CE P

40.

AC

39.

(1998). L.E. Bove, R. Gaal, Z. Raza, A.A. Ludl, S. Klotz, A.M. Saitta, A.F. Goncharov, and P. Gillet, Effect of salt on the H-bond symmetrization in ice. Proc Natl Acad Sci U S A, 112(27): 8216–8220, (2015). Y. Bronstein, P. Depondt, F. Finocchi, and A.M. Saitta, Quantum-driven phase transition in ice described via an efficient Langevin approach. Phys. Rev. B, 89(21): 214101, (2014). Y. Bronstein, P. Depondt, L.E. Bove, R. Gaal, A.M. Saitta, and F. Finocchi, Quantum versus classical protons in pure and salty ice under pressure. Phys. Rev. B, 93(2): 024104, (2016). C. Corsaro, D. Mallamace, N. Cicero, S. Vasi, G. Dugo, and F. Mallamace, Dynamics of water clusters in solution with LiCl. Physica A: Statistical Mechanics and its Applications, 442: 261-267, (2016). Y. Zhou, Y. Zhong, Y. Gong, X. Zhang, Z. Ma, Y. Huang, and C.Q. Sun, Unprecedented thermal stability of water supersolid skin. J. Mol. Liq., 220: 865-869, (2016). X. Zhang, X. Liu, Y. Zhong, Z. Zhou, Y. Huang, and C.Q. Sun, Nanobubble Skin Supersolidity. Langmuir, (2016). X. Zhang, Y. Huang, Z. Ma, Y. Zhou, J. Zhou, W. Zheng, Q. Jiang, and C.Q. Sun, Hydrogen-bond memory and water-skin supersolidity resolving the Mpemba paradox. PCCP, 16(42): 22995-23002, (2014). X. Zhang, Y. Huang, Z. Ma, Y. Zhou, W. Zheng, J. Zhou, and C.Q. Sun, A common supersolid skin covering both water and ice. PCCP, 16(42): 22987-22994, (2014). Y. Huang, X. Zhang, Z. Ma, Y. Zhou, J. Zhou, W. Zheng, and C.Q. Sun, Size, separation, structure order, and mass density of molecules packing in water and ice. Sci Rep, 3: 3005, (2013). Y. Huang, Z. Ma, X. Zhang, G. Zhou, Y. Zhou, and C.Q. Sun, Hydrogen Bond Asymmetric Local Potentials in Compressed Ice. J. Phys. Chem. B, 117(43): 13639-13645, (2013). L. Berg, B.K. Mishra, C.D. Andersson, F. Ekström, and A. Linusson, The Nature of Activated Non‐classical Hydrogen Bonds: A Case Study on Acetylcholinesterase–Ligand Complexes. Chemistry–A European Journal, (2016). B. Linclau, F. Peron, E. Bogdan, N. Wells, Z. Wang, G. Compain, C.Q. Fontenelle, N. Galland, J.-Y. Le Questel, and J. Graton, Intramolecular OH center dot center dot center dot Fluorine Hydrogen Bonding in Saturated, Acyclic Fluorohydrins: The gamma-Fluoropropanol Motif. Chem.-Eur. J., 21(49): 17808-17816, (2015). T. Yan, S. Li, K. Wang, X. Tan, Z. Jiang, K. Yang, B. Liu, G. Zou, and B. Zou, Pressure-induced phase transition in N-H...O hydrogen-bonded molecular crystal oxamide. J. Phys. Chem. B, 116(32): 9796-802, (2012). R.J. Thatcher, Johnson, D. G., Slattery, J. M. and Douthwaite, R. E. , Structure of Amido Pyridinium Betaines: Persistent Intermolecular C−H⋅⋅⋅N Hydrogen Bonding in Solution. Chem. Eur. J., doi:10.1002/chem.201503884, (2016). Y. Mo, C. Wang, L. Guan, B. Braïda, P.C. Hiberty, and W. Wu, On the nature of blueshifting hydrogen bonds. Chem.-Eur. J., 20(27): 8444-8452, (2014). H.C. Chen, F.D. Mai, K.H. Yang, L.Y. Chen, C.P. Yang, and Y.C. Liu, Quantitative Evaluation on Activated Property-Tunable Bulk Liquid Water with Reduced Hydrogen Bonds Using Deconvoluted Raman Spectroscopy. Anal. Chem., (2014). K. Sutter, G.A. Aucar, and J. Autschbach, Analysis of Proton NMR in Hydrogen Bonds in Terms 18

ACCEPTED MANUSCRIPT

62.

T

IP

SC R

NU

61.

MA

60.

D

59.

TE

58.

CE P

57.

AC

56.

of Lone-Pair and Bond Orbital Contributions. Chem.-Eur. J., 21(50): 18138-18155, (2015). J.M. Guevara‐Vela, R. Chávez‐Calvillo, M. García‐Revilla, J. Hernández‐Trujillo, O. Christiansen, E. Francisco, Á. Martín Pendás, and T. Rocha‐Rinza, Hydrogen‐Bond Cooperative Effects in Small Cyclic Water Clusters as Revealed by the Interacting Quantum Atoms Approach. Chem.-Eur. J., 19(42): 14304-14315, (2013). Q. Zeng, T. Yan, K. Wang, Y. Gong, Y. Zhou, Y. Huang, C.Q. Sun, and B. Zou, Compression icing of room-temperature NaX solutions (X= F, Cl, Br, I). PCCP, 18(20): 14046-14054, (2016). C.Q. Sun, X. Zhang, J. Zhou, Y. Huang, Y. Zhou, and W. Zheng, Density, Elasticity, and Stability Anomalies of Water Molecules with Fewer than Four Neighbors. J. Phys. Chem. Lett., 4: 2565-2570, (2013). C.Q. Sun, X. Zhang, and W.T. Zheng, Hidden force opposing ice compression. Chem Sci, 3: 1455-1460, (2012). Y. Yoshimura, S.T. Stewart, M. Somayazulu, H.K. Mao, and R.J. Hemley, Convergent Raman Features in High Density Amorphous Ice, Ice VII, and Ice VIII under Pressure. J. Phys. Chem. B, 115(14): 3756-3760, (2011). J.G. Davis, K.P. Gierszal, P. Wang, and D. Ben-Amotz, Water structural transformation at molecular hydrophobic interfaces. Nature, 491(7425): 582-585, (2012). H. Bhatt, C. Murli, A.K. Mishra, A.K. Verma, N. Garg, M.N. Deo, R. Chitra, and S.M. Sharma, Hydrogen Bond Symmetrization in Glycinium Oxalate under Pressure. The Journal of Physical Chemistry B, 120 (4): 851-859, (2016).

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LiOH NaOH KOH

Graphical Abstract -80

3200 -1 H / cm

3600

2800

3000

3200 3400 -1 H / cm

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0.77 1.03 1.33

I / a.u.

I / a.u.

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3800