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Chamberlayne CF, Zare RN. Simple Estimate of the Potential Drop across an Amphiprotic Liquid-Liquid Interface. J Phys Chem B 2022; 126:8112-8118. [PMID: 36194396 DOI: 10.1021/acs.jpcb.2c05696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two immiscible liquids in contact with each other can have different internal electrostatic potentials. An associated electric double layer (EDL) therefore exists within each liquid. For amphiprotic liquids, the exchange of protons between the two liquids gives rise to two EDLs, a positively charged EDL in one of the liquids and negatively charged EDL in the other. Using the pKa and pKb of one liquid dissolved in the other and the pH equivalent within each amphiprotic liquid, we can estimate the potential drop, Δφ, between the interior of the two liquids, also known as the Galvani potential or liquid-liquid junction potential. This estimation is independent of surface charge and ionic strength. By using the ionic strength to find the thickness of the EDL, we also estimate the average electric field strength across the interface. For the special case of water (H2O) in contact with an immiscible alcohol (ROH), the potential drop across the interface from the water to the alcohol is Δφ = 2.303VT (pKb + pH - pKw - pH2OR), where VT is the thermal voltage at a given temperature T.
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Affiliation(s)
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, California94305, United States
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2
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Chamberlayne CF, Zare RN. Microdroplets can act as electrochemical cells. J Chem Phys 2022; 156:054705. [PMID: 35135250 PMCID: PMC8824579 DOI: 10.1063/5.0078281] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 01/10/2022] [Indexed: 12/21/2022] Open
Abstract
A water microdroplet in air or oil typically possesses an electric double layer (EDL) from the preferential adsorption of surface-bound ions at the periphery. We present the calculations of the ion gradients within a microdroplet at equilibrium, including systems containing buffers and water autoionization. These ion gradients are used to calculate the potential energy stored within the microdroplet. We consider how this stored potential energy can be utilized to drive chemical reactions, much like an electrochemical cell. Effective voltages as high as 111 mV are found for microdroplets having a low surface charge density (0.01 ions per nm2). Two sources of potential energy are investigated: (1) the electrostatic energy of the EDL of the microdroplet and (2) shifts in other chemical equilibria coupled to the main reaction through the EDL. A particularly important example of the latter is water autoionization, wherein the reaction of interest causes a flattening of the [H+] gradient within the EDL, resulting in a net recombination of H+ and OH- throughout the microdroplet. Numerical calculations are performed using a continuum model consisting of a balance between the electromigration and diffusion of ions throughout the microdroplet. Our treatment accounts for the autoionization of water and any chemical equilibrium of buffers present. The results are presented for uncharged water microdroplets with low amounts of salts and simple buffers in them. However, the calculational method presented here can be applied to microdroplets of any net charge, composed of any solvent, containing ions of any valence, and containing complex mixtures of chemical equilibria.
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Affiliation(s)
| | - Richard N. Zare
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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3
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Li YL, Zhou BW, Cheng J, Zhang F, Zhang J, Zhang L, Guo YL. Mass Spectrometry-Based Discovery of New Chemical Scaffold Rearrangement Ions: Aza-biphenylene as a Novel Potent Biradical Agent in Cancer Chemotherapy. Anal Chem 2020; 92:14517-14527. [PMID: 33054169 DOI: 10.1021/acs.analchem.0c02669] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Discovery of a new drug is time-consuming, laborious, and expensive. Herein, a novel integrative strategy for discovering potential new lead compounds has been developed, which was based on the characteristics of mass spectrometry (MS). MS was used to predict the potential forced degradation products (DPs) and metabolites of drugs by electrospray ionization and collision-induced dissociation (CID). Special rearrangement ions representing unique predicted DPs and metabolites were identified. The consistency between the predicted and the measured results was proven by in vitro metabolism and forced degradation of a commercial drug, respectively. From this, new chemical scaffold rearrangement ions named (aza)-biphenylenes, as potent anticancer agents, were discovered. As a representative aza-biphenylene analogue, 2-azabiphenylene was proven in vitro to induce apoptosis and inhibit the growth of various human cancer cells in a dose-dependent manner. Surprisingly, 2-azabiphenylene exhibited the best comparable bioactivity with the positive control sorafenib, but showed significantly lower in vitro cytotoxicity than sorafenib (at least a 5-fold decrease in cytotoxicity) because it could be targeted to the tumor microenvironment at low pH. A biradical mechanism accompanied by a mitochondrion-dependent oxidative stress mechanism was proposed to explore its anticancer mechanism. The highly reactive intermediate aza-biphenylenediyl worked as an active pharmaceutical ingredient and induced apoptosis of cancer cells. This provided the basis for the potential applications of CID-induced special rearrangement ions in developing new lead compounds.
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Affiliation(s)
- Yu-Ling Li
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Bo-Wen Zhou
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jie Cheng
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Fang Zhang
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jing Zhang
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Li Zhang
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yin-Long Guo
- State Key Laboratory of Organometallic Chemistry and National Center for Organic Mass Spectrometry in Shanghai, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
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Chen HT, Zhou Z, Subotnik JE. On the proper derivation of the Floquet-based quantum classical Liouville equation and surface hopping describing a molecule or material subject to an external field. J Chem Phys 2020; 153:044116. [PMID: 32752688 DOI: 10.1063/5.0013873] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate different approaches to derive the proper Floquet-based quantum-classical Liouville equation (F-QCLE) for laser-driven electron-nuclear dynamics. The first approach projects the operator form of the standard QCLE onto the diabatic Floquet basis and then transforms to the adiabatic representation. The second approach directly projects the QCLE onto the Floquet adiabatic basis. Both approaches yield a form that is similar to the usual QCLE with two modifications: (1) The electronic degrees of freedom are expanded to infinite dimension and (2) the nuclear motion follows Floquet quasi-energy surfaces. However, the second approach includes an additional cross derivative force due to the dual dependence on time and nuclear motion of the Floquet adiabatic states. Our analysis and numerical tests indicate that this cross derivative force is a fictitious artifact, suggesting that one cannot safely exchange the order of Floquet state projection with adiabatic transformation. Our results are in accord with similar findings by Izmaylov et al., [J. Chem. Phys. 140, 084104 (2014)] who found that transforming to the adiabatic representation must always be the last operation applied, although now we have extended this result to a time-dependent Hamiltonian. This paper and the proper derivation of the F-QCLE should lay the basis for further improvements of Floquet surface hopping.
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Affiliation(s)
- Hsing-Ta Chen
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Zeyu Zhou
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Joseph E Subotnik
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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van den Berg JL, Neumann KI, Harrison JA, Weir H, Hohenstein EG, Martinez TJ, Zare RN. Strong, Nonresonant Radiation Enhances Cis- Trans Photoisomerization of Stilbene in Solution. J Phys Chem A 2020; 124:5999-6008. [PMID: 32585098 DOI: 10.1021/acs.jpca.0c02732] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Previously, it has been demonstrated that external electric fields may be used to exert control over chemical reactivity. In this study, the impact of a strong, nonresonant IR field (1064 nm) on the photoisomerization of cis-stilbene is investigated in cyclohexane solution. The design of a suitable reaction vessel for characterization of this effect is presented. The electric field supplied by the pulsed, near-IR radiation (εl = 4.5 × 107 V/cm) enhances the cis → trans photoisomerization yield at the red edge of the absorption spectrum (wavelengths between 337 and 340 nm). Within the microliter focal volume, up to 75% of all cis-stilbene molecules undergo isomerization to trans-stilbene in the strong electric-field environment, indicating a significant increase relative to the 35% yield of trans-stilbene under field-free conditions. This result correlates with a 1-3% enhancement in the trans-stilbene concentration throughout the bulk solution. Theoretical analysis suggests that the observed change is the result of dynamic Stark shifting of the ground and first excited states, leading to a significant redshift in cis-stilbene's absorption spectrum. The predicted increase in the absorption cross section in this range of excitation wavelengths is qualitatively consistent with the experimental increase in trans-stilbene production.
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Affiliation(s)
- Jana L van den Berg
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Kallie Ilene Neumann
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - John A Harrison
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,Chemistry, School of Natural and Computational Sciences, Massey University Auckland, Private Bag 102904, Auckland 4442, New Zealand
| | - Hayley Weir
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Edward G Hohenstein
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Todd J Martinez
- Department of Chemistry, Stanford University, Stanford, California 94305, United States.,SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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Zhang K, Ma L, Zhou M, Shi Y, Li S, Wang Y, Kong X. Wavelength-Dependent Ultraviolet Photodissociation of Protonated Tryptamine. J Phys Chem A 2020; 124:5280-5287. [PMID: 32536155 DOI: 10.1021/acs.jpca.0c02528] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Ultraviolet photodissociation (UVPD) experiments of protonated tryptamine ([Tryp+H]+) have been implemented by a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer combined with a wavelength-tunable optical parametric oscillator (OPO) laser. UVPD mass spectra under different laser wavelengths have been obtained, in which the dependence of the yield of fragment ions on the laser wavelength was observed. The UVPD spectrum of [Tryp+H]+ has been obtained in the range of 210-310 nm. Besides the previously reported two competitive channels of H loss and NH3 loss, two important channels of losing CH2NH and CH2NH2 units were observed and further studied by UV-UV tandem mass spectrometry and theoretical calculations. Interestingly, results show that the pair of competitive channels of CH2NH loss and CH2NH2 loss are both from the McLafferty-type rearrangement caused by ππ* electronic excited states. After the excitation, the two different dissociation pathways produce two different ion-neutral complexes, respectively. The wavelength-dependent dissociation and the existing competitive channels shown in this study reflect the diversity of UVPD processes of such organic molecules.
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Affiliation(s)
- Kailin Zhang
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China.,State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
| | - Lifu Ma
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
| | - Min Zhou
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China.,Department of Physics, Anhui Normal University, Wuhu 241000, China
| | - Yingying Shi
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
| | - Shuqi Li
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
| | - Yan Wang
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
| | - Xianglei Kong
- State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China.,Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
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Chamberlayne CF, Zare RN. Simple model for the electric field and spatial distribution of ions in a microdroplet. J Chem Phys 2020; 152:184702. [PMID: 32414270 DOI: 10.1063/5.0006550] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It is well established that the chemistry in microdroplets has been found to be radically different from reactions in bulk, particularly in the case of water. It has also been established that there is a threshold size for microdroplets to behave differently than droplets near the 10 µm diameter range. We present a three-dimensional electrostatic treatment in the spirit of the Gouy-Chapman model for double layers at interfaces. Our treatment predicts a strong concentration of charged molecules toward the surface of the droplet. As the droplet size deceases, the majority of the volume of the liquid experiences a large DC electric field. Such electric fields are highly unusual in a conducting fluid such as water. We believe that this unique environment helps to explain the reaction rate acceleration and new chemistry that have been observed in microdroplets compared to bulk phase.
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Affiliation(s)
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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Zhou Z, Chen HT, Nitzan A, Subotnik JE. Nonadiabatic Dynamics in a Laser Field: Using Floquet Fewest Switches Surface Hopping To Calculate Electronic Populations for Slow Nuclear Velocities. J Chem Theory Comput 2020; 16:821-834. [PMID: 31951404 DOI: 10.1021/acs.jctc.9b00950] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We investigate two well-known approaches for extending the fewest switches surface hopping (FSSH) algorithm to periodic time-dependent couplings. The first formalism acts as if the instantaneous adiabatic electronic states were standard adiabatic states, which just happen to evolve in time. The second formalism replaces the role of the usual adiabatic states by the time-independent adiabatic Floquet states. For a set of modified Tully model problems, the Floquet FSSH (F-FSSH) formalism gives a better estimate for both transmission and reflection probabilities than the instantaneous adiabatic FSSH (IA-FSSH) formalism, especially for slow nuclear velocities. More importantly, only F-FSSH predicts the correct final scattering momentum. Finally, in order to use Floquet theory accurately, we find that it is crucial to account for the interference between wavepackets on different Floquet states. Our results should be of interest to all those interested in laser-induced molecular dynamics.
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Affiliation(s)
- Zeyu Zhou
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Hsing-Ta Chen
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Abraham Nitzan
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Joseph Eli Subotnik
- Department of Chemistry , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
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Hilsabeck KI, Meiser JL, Sneha M, Harrison JA, Zare RN. Nonresonant Photons Catalyze Photodissociation of Phenol. J Am Chem Soc 2019; 141:1067-1073. [PMID: 30571915 DOI: 10.1021/jacs.8b11695] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phenol represents an ideal polyatomic system for demonstrating photon catalysis because of its large polarizability, well-characterized excited-state potential energy surfaces, and nonadiabatic dissociation dynamics. A nonresonant IR pulse (1064 nm) supplies a strong electric field (4 × 107 V/cm) during the photolysis of isolated phenol (C6H5OH) molecules to yield C6H5O + H near two known energetic thresholds: the S1/S2 conical intersection and the S1 - S0 origin. H-atom speed distributions show marked changes in the relative contributions of dissociative pathways in both cases, compared to the absence of the nonresonant IR pulse. Results indicate that nonresonant photons lower the activation barrier for some pathways relative to others by dynamically Stark shifting the excited-state potential energy surfaces rather than aligning molecules in the strong electric field. Theoretical calculations offer support for the experimental interpretation.
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Affiliation(s)
- Kallie I Hilsabeck
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Jana L Meiser
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - Mahima Sneha
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
| | - John A Harrison
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States.,Chemistry, Institute of Natural and Mathematical Sciences , Massey University Auckland , Auckland 0632 , New Zealand
| | - Richard N Zare
- Department of Chemistry , Stanford University , Stanford , California 94305 , United States
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