1
|
Quintano M, Moura RT, Kraka E. Exploring Jahn-Teller distortions: a local vibrational mode perspective. J Mol Model 2024; 30:102. [PMID: 38478107 PMCID: PMC11315727 DOI: 10.1007/s00894-024-05882-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 02/20/2024] [Indexed: 04/06/2024]
Abstract
The characterization of normal mode (CNM) procedure coupled with an adiabatic connection scheme (ACS) between local and normal vibrational modes, both being a part of the Local Vibrational Mode theory developed in our group, can identify spectral changes as structural fingerprints that monitor symmetry alterations, such as those caused by Jahn-Teller (JT) distortions. Employing the PBE0/Def2-TZVP level of theory, we investigated in this proof-of-concept study the hexaaquachromium cation case,[ Cr ( OH 2 ) 6 ] 3 + /[ Cr ( OH 2 ) 6 ] 2 + , as a commonly known example for a JT distortion, followed by the more difficult ferrous and ferric hexacyanide anion case,[ Fe ( CN ) 6 ] 4 - /[ Fe ( CN ) 6 ] 3 - . We found that in both cases CNM of the characteristic normal vibrational modes reflects delocalization consistent with high symmetry and ACS confirms symmetry breaking, as evidenced by the separation of axial and equatorial group frequencies. As underlined by the Cremer-Kraka criterion for covalent bonding, from[ Cr ( OH 2 ) 6 ] 3 + to[ Cr ( OH 2 ) 6 ] 2 + there is an increase in axial covalency whereas the equatorial bonds shift toward electrostatic character. From[ Fe ( CN ) 6 ] 4 - to[ Fe ( CN ) 6 ] 3 - we observed an increase in covalency without altering the bond nature. Distinct π back-donation disparity could be confirmed by comparison with the isolated CN- system. In summary, our study positions the CNM/ACS protocol as a robust tool for investigating less-explored JT distortions, paving the way for future applications.
Collapse
Affiliation(s)
- Mateus Quintano
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, TX, 75275-0314, USA
| | - Renaldo T Moura
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, TX, 75275-0314, USA
- Department of Chemistry and Physics, Center of Agrarian Sciences, Federal University of Paraiba, Areia, PB, 58397-000, Brazil
| | - Elfi Kraka
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, TX, 75275-0314, USA.
| |
Collapse
|
2
|
Talewar SK, Pardo LC, Headen TF, Halukeerthi SO, Chikani B, Rosu-Finsen A, Salzmann CG. Hydrophobic hydration of the hydrocarbon adamantane in amorphous ice. Faraday Discuss 2024; 249:69-83. [PMID: 37794776 PMCID: PMC10845010 DOI: 10.1039/d3fd00102d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/19/2023] [Indexed: 10/06/2023]
Abstract
Hydrophobic molecules are by definition difficult to hydrate. Previous studies in the area of hydrophobic hydration have therefore often relied on using amphiphilic molecules where the hydrophilic part of a molecule enabled the solubility in liquid water. Here, we show that the hydrophobic adamantane (C10H16) molecule can be fully hydrated through vapour codeposition with water onto a cryogenic substrate at 80 K resulting in the matrix isolation of adamantane in amorphous ice. Using neutron diffraction in combination with the isotopic substitution method and the empirical potential structure refinement technique, we find that the first hydration shell of adamantane is well structured consisting of a hydrogen-bonded cage of 28 water molecules that is also found in cubic structure II clathrate hydrates. The four hexagonal faces of the 51264 cage are situated above the four methine (CH) groups of adamantane whereas the methylene (CH2) groups are positioned below the edges of two adjoining pentagonal faces. The oxygen atoms of the 28 water molecules can be categorised on the basis of symmetry equivalences as twelve A, twelve B and four C oxygens. The water molecules of the first hydration shell display orientations consistent with those expected for a clathrate-hydrate-type cage, but also unfavourable ones with respect to the hydrogen bonding between the water molecules. Annealing the samples at 140 K, which is just below the crystallisation temperature of the matrix, removes the unfavourable orientations and leads to a slight increase in the structural order of the first hydration shell. The very closest water molecules display a tendency for their dipole moments to point towards the adamantane which is attributed to steric effects. Other than this, no significant polarisation effects are observed which is consistent with weak interactions between adamantane and the amorphous ice matrix. FT-IR spectroscopy shows that the incorporation of adamantane into amorphous ice leads to a weakening of the hydrogen bonds. In summary, the matrix-isolation of the highly symmetric adamantane in amorphous ice provides an interesting test case for hydrophobic hydration. Studying the structure and spectroscopic properties of water at the interface with hydrophobic hydrocarbons is also relevant for astrophysical environments, such as comets or the interstellar medium, where amorphous ice and hydrocarbons have been shown to coexist in large quantities.
Collapse
Affiliation(s)
- Sukhpreet K Talewar
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Luis Carlos Pardo
- Grup de Caracterització de Materials, Departament de Física, EEBE, Universitat Politècnica de Catalunya, and Barcelona Research Center in Multiscale Science and Engineering, C/Eduard Maristany 10, E-08019 Barcelona, Spain
| | - Thomas F Headen
- ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, OX11 0QX, UK
| | - Siriney O Halukeerthi
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Bharvi Chikani
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Alexander Rosu-Finsen
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| | - Christoph G Salzmann
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
| |
Collapse
|
3
|
Zhao Z, Li Y, Wang H, Shan Y, Liu X, Wu M, Zhang X, Song X. Ultra-Tough Self-Healing Hydrogel via Hierarchical Energy Associative Dissipation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303315. [PMID: 37505367 PMCID: PMC10520617 DOI: 10.1002/advs.202303315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 06/28/2023] [Indexed: 07/29/2023]
Abstract
Owing to high water content and homogeneous texture, conventional hydrogels hardly reach satisfactory mechanical performance. Tensile-resistant groups and structural heterogeneity are employed to fabricate tough hydrogels. However, those techniques significantly increase the complexity and cost of material synthesis, and have only limited applicability. Here, it is shown that ultra-tough hydrogels can be obtained via a unique hierarchical architecture composed of chemically coupled self-assembly units. The associative energy dissipation among them may be rationally engineered to yield libraries of tough gels with self-healing capability. Tunable tensile strength, fracture strain, and toughness of up to 19.6 MPa, 20 000%, and 135.7 MJ cm⁻3 are achieved, all of which exceed the best known records. The results demonstrate a universal strategy to prepare desired ultra-tough hydrogels in predictable and controllable manners.
Collapse
Affiliation(s)
- Zhi Zhao
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
| | - Yurong Li
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
- Institute of Information Photonics TechnologyFaculty of ScienceBeijing University of TechnologyBeijing100124China
| | - Haibin Wang
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
| | - Yupeng Shan
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
| | - Xuemei Liu
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
| | - Mengfei Wu
- Department of Engineering MechanicsBeijing University of TechnologyBeijing100124China
| | - Xinping Zhang
- Institute of Information Photonics TechnologyFaculty of ScienceBeijing University of TechnologyBeijing100124China
| | - Xiaoyan Song
- Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China
| |
Collapse
|
4
|
Rubli PT, Dopfer O. Infrared spectrum of the 1-cyanoadamantane cation: evidence of hydrogen transfer and cage-opening upon ionization. Phys Chem Chem Phys 2023; 25:22734-22743. [PMID: 37584199 DOI: 10.1039/d3cp03417h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2023]
Abstract
The radical cations of diamondoids are important intermediates in their functionalization reactions and are also candidates as carriers for astronomical absorption and emission features. Although neutral diamondoids have been studied extensively, information regarding their radical cations is largely lacking, particularly for functionalized diamondoid derivatives. Herein, we characterize the structure of the 1-cyanoadamantane radical cation (C10H15CN+, AdCN+) using infrared photodissociation (IRPD) spectroscopy of mass selected AdCN+N2 clusters in the XH stretch range (2400-3500 cm-1) and dispersion-corrected density functional theory calculations (B3LYP-D3BJ/cc-pVTZ). A group of three distinct CH stretch bands are observed in the 2800-3000 cm-1 range, in addition to a highly redshifted absorption at 2580 cm-1 attributed to the acidic CH proton predicted by calculations. An unexpected broad absorption peaking at 3320 cm-1 is also detected and assigned to an NH stretch mode based on its width and frequency. Calculations indicate that hydrogen atom transfer (HAT) from the adamantyl cage (C10H15, Ady) to the N atom of the CN group yields lower energy structures, with an open-cage isomer exhibiting such hydrogen transfer being the global minimum on the potential energy surface. The energy barriers involved in the formation of this open-cage isomer are also lower than those calculated for generation of the analogous open-cage 1-amantadine cation isomer which has previously been identified by IRPD. The combined consideration of IRPD spectra and calculations indicates a major population of the nascent canonical closed-cage isomer and a smaller population of the global minimum isomer featuring both cage-opening and hydrogen transfer.
Collapse
Affiliation(s)
- Peter Theodore Rubli
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
5
|
George MAR, Dopfer O. Microhydration of the adamantane cation: intracluster proton transfer to solvent in [Ad(H 2O) n=1-5] + for n ≥ 3. Phys Chem Chem Phys 2023; 25:13593-13610. [PMID: 37144298 DOI: 10.1039/d3cp01514a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Radical cations of diamondoids are important intermediates in their functionalization reactions in polar solvents. To explore the role of the solvent at the molecular level, we characterize herein microhydrated radical cation clusters of the parent molecule of the diamondoid family, adamantane (C10H16, Ad), by infrared photodissociation (IRPD) spectroscopy of mass-selected [Ad(H2O)n=1-5]+ clusters. IRPD spectra of the cation ground electronic state recorded in the CH/OH stretch and fingerprint ranges reveal the first steps of this fundamental H-substitution reaction at the molecular level. Analysis of size-dependent frequency shifts with dispersion-corrected density functional theory calculations (B3LYP-D3/cc-pVTZ) provides detailed information about the acidity of the proton of Ad+ as a function of the degree of hydration, the structure of the hydration shell, and the strengths of the CH⋯O and OH⋯O hydrogen bonds (H-bonds) of the hydration network. For n = 1, H2O strongly activates the acidic C-H bond of Ad+ by acting as a proton acceptor in a strong CH⋯O ionic H-bond with cation-dipole configuration. For n = 2, the proton is almost equally shared between the adamantyl radical (C10H15, Ady) and the (H2O)2 dimer in a strong C⋯H⋯O ionic H-bond. For n ≥ 3, the proton is completely transferred to the H-bonded hydration network. The threshold for this size-dependent intracluster proton transfer to solvent is consistent with the proton affinities of Ady and (H2O)n and confirmed by collision-induced dissociation experiments. Comparison with other related microhydrated cations reveals that the acidity of the CH proton of Ad+ is in the range of strongly acidic phenol+ but lower than for cationic linear alkanes such as pentane+. Significantly, the presented IRPD spectra of microhydrated Ad+ provide the first spectroscopic molecular-level insight of the chemical reactivity and reaction mechanism of the important class of transient diamondoid radical cations in aqueous solution.
Collapse
Affiliation(s)
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
6
|
George MAR, Dopfer O. Microhydrated clusters of a pharmaceutical drug: infrared spectra and structures of amantadineH +(H 2O) n. Phys Chem Chem Phys 2023; 25:5529-5549. [PMID: 36723361 DOI: 10.1039/d2cp04556g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Solvation of pharmaceutical drugs has an important effect on their structure and function. Analysis of infrared photodissociation spectra of amantadineH+(H2O)n=1-4 clusters in the sensitive OH, NH, and CH stretch range by quantum chemical calculations (B3LYP-D3/cc-pVTZ) provides a first impression of the interaction of this pharmaceutically active cation with water at the molecular level. The size-dependent frequency shifts reveal detailed information about the acidity of the protons of the NH3+ group of N-protonated amantadineH+ (AmaH+) and the strength of the NH⋯O and OH⋯O hydrogen bonds (H-bonds) of the hydration network. The preferred cluster growth begins with sequential hydration of the NH3+ group by NH⋯O ionic H-bonds (n = 1-3), followed by the extension of the solvent network through OH⋯O H-bonds. However, smaller populations of cluster isomers with an H-bonded solvent network and free N-H bonds are already observed for n ≥ 2, indicating the subtle competition between noncooperative ion hydration and cooperative H-bonding. Interestingly, cyclic water ring structures are identified for n ≥ 3, each with two NH⋯O and two OH⋯O H-bonds. Despite the increasing destabilization of the N-H proton donor bonds upon gradual hydration, no proton transfer to the (H2O)n solvent cluster is observed up to n = 4. In addition to ammonium cluster ions, a small population of microhydrated iminium isomers is also detected, which is substantially lower for the hydrophilic H2O than for the hydrophobic Ar environment.
Collapse
Affiliation(s)
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
7
|
George MAR, Dopfer O. Infrared spectra and structures of protonated amantadine isomers: detection of ammonium and open-cage iminium ions. Phys Chem Chem Phys 2022; 24:16101-16111. [PMID: 35748364 DOI: 10.1039/d2cp01947g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The protonated form of amantadine (1-C10H15NH2, Ama), the amino derivative of adamantane (C10H16, Ada), is a wide-spread antiviral and anti-Parkinsonian drug and plays a key role in many pharmaceutical processes. Recent studies reveal that the adamantyl cage (C10H15) of Ama can open upon ionization leading to distonic bicyclic iminium isomers, in addition to the canonical nascent Ama+ isomer. Herein, we study protonation of Ama using infrared photodissociation spectroscopy (IRPD) of Ar-tagged ions and density functional theory calculations to characterize cage and open-cage isomers of AmaH+ and the influence of the electron-donating NH2 group on the cage-opening reaction potential. In addition to the canonical ammonium isomer (AmaH+(I)) with an intact adamantyl cage, we identify at least one slightly less stable protonated bicyclic iminium ion (AmaH+(II)). While the ammonium ion is generated by protonation of the basic NH2 group, AmaH+(II) is formally formed by H addition to a distonic bicyclic iminium ion produced upon ionization of Ama and subsequent cage opening.
Collapse
Affiliation(s)
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany.
| |
Collapse
|
8
|
George MAR, Dopfer O. Opening of the Diamondoid Cage upon Ionization Probed by Infrared Spectra of the Amantadine Cation Solvated by Ar, N 2 , and H 2 O. Chemistry 2022; 28:e202200577. [PMID: 35611807 PMCID: PMC9400954 DOI: 10.1002/chem.202200577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Indexed: 01/18/2023]
Abstract
Radical cations of diamondoids, a fundamental class of very stable cyclic hydrocarbon molecules, play an important role in their functionalization reactions and the chemistry of the interstellar medium. Herein, we characterize the structure, energy, and intermolecular interaction of clusters of the amantadine radical cation (Ama+, 1‐aminoadamantane) with solvent molecules of different interaction strength by infrared photodissociation (IRPD) spectroscopy of mass‐selected Ama+Ln clusters, with L=Ar (n≤3) and L=N2 and H2O (n=1), and dispersion‐corrected density functional theory calculations (B3LYP−D3/cc‐pVTZ). Three isomers of Ama+ generated by electron ionization are identified by the vibrational properties of their rather different NH2 groups. The ligands bind preferentially to the acidic NH2 protons, and the strength of the NH…L ionic H‐bonds are probed by the solvation‐induced red‐shifts in the NH stretch modes. The three Ama+ isomers include the most abundant canonical cage isomer (I) produced by vertical ionization, which is separated by appreciable barriers from two bicyclic distonic iminium ions obtained from cage‐opening (primary radical II) and subsequent 1,2 H‐shift (tertiary radical III), the latter of which is the global minimum on the Ama+ potential energy surface. The effect of solvation on the energetics of the potential energy profile revealed by the calculations is consistent with the observed relative abundance of the three isomers. Comparison to the adamantane cation indicates that substitution of H by the electron‐donating NH2 group substantially lowers the barriers for the isomerization reaction.
Collapse
Affiliation(s)
| | - Otto Dopfer
- Institut für Optik und Atomare PhysikTechnische Universität BerlinHardenbergstr. 3610623BerlinGermany
| |
Collapse
|
9
|
Robert George MA, Dopfer O. Infrared Spectrum of the Amantadine Cation: Opening of the Diamondoid Cage upon Ionization. J Phys Chem Lett 2022; 13:449-454. [PMID: 34990124 DOI: 10.1021/acs.jpclett.1c03948] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Radical cations of diamondoids, a fundamental class of highly stable cycloalkanes, are intermediates in functionalization reactions and possibly present in the interstellar medium. Herein, we characterize the structure of the radical cation of 1-amantadine (1-C10H15NH2+, Ama+), the amino derivative of the parent adamantane (C10H16+, Ada+), by infrared spectroscopy and density functional theory calculations. The structural isomers of Ama+ produced by electron ionization are probed by infrared photodissociation of cold Ar-tagged ions. In addition to the canonical nascent Ama+ isomer with an intact C10H15 cage, we identify two distonic bicyclic iminium isomers in which the adamantyl cage opens upon ionization, one of which is lower in energy than the cage isomer. The reaction profile with barriers and intermediates for this cage-opening reaction are determined. Comparison with Ada+ suggests that this type of ionization-induced cage-opening may be a common feature for diamondoids and important for their reactivity.
Collapse
Affiliation(s)
- Martin Andreas Robert George
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrsase 36, 10623 Berlin, Germany
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrsase 36, 10623 Berlin, Germany
| |
Collapse
|
10
|
Fárník M, Fedor J, Kočišek J, Lengyel J, Pluhařová E, Poterya V, Pysanenko A. Pickup and reactions of molecules on clusters relevant for atmospheric and interstellar processes. Phys Chem Chem Phys 2021; 23:3195-3213. [PMID: 33524089 DOI: 10.1039/d0cp06127a] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this perspective, we review experiments with molecules picked up on large clusters in molecular beams with the focus on the processes in atmospheric and interstellar chemistry. First, we concentrate on the pickup itself, and we discuss the pickup cross sections. We measure the uptake of different atmospheric molecules on mixed nitric acid-water clusters and determine the accommodation coefficients relevant for aerosol formation in the Earth's atmosphere. Then the coagulation of the adsorbed molecules on the clusters is investigated. In the second part of this perspective, we review examples of different processes triggered by UV-photons or electrons in the clusters with embedded molecules. We start with the photodissociation of hydrogen halides and Freon CF2Cl2 on ice nanoparticles in connection with the polar stratospheric ozone depletion. Next, we mention reactions following the excitation and ionization of the molecules adsorbed on clusters. The first ionization-triggered reaction observed between two different molecules picked up on the cluster was the proton transfer between methanol and formic acid deposited on large argon clusters. Finally, negative ion reactions after slow electron attachment are illustrated by two examples: mixed nitric acid-water clusters, and hydrogen peroxide deposited on large ArN and (H2O)N clusters. The selected examples are discussed from the perspective of the atmospheric and interstellar chemistry, and several future directions are proposed.
Collapse
Affiliation(s)
- Michal Fárník
- J. Heyrovský Institute of Physical Chemistry, v.v.i., The Czech Academy of Sciences, Dolejškova 2155/3, 182 23 Prague, Czech Republic.
| | | | | | | | | | | | | |
Collapse
|
11
|
George MAR, Buttenberg F, Förstel M, Dopfer O. Microhydration of substituted diamondoid radical cations of biological relevance: infrared spectra of amantadine +-(H 2O) n = 1-3 clusters. Phys Chem Chem Phys 2020; 22:28123-28139. [PMID: 33290468 DOI: 10.1039/d0cp05299j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hydration of biomolecules and pharmaceutical compounds has a strong impact on their structure, reactivity, and function. Herein, we explore the microhydration structure around the radical cation of the widespread pharmaceutical drug amantadine (C16H15NH2, Ama) by infrared photodissociation (IRPD) spectroscopy of mass-selected Ama+Wn = 1-3 clusters (W = H2O) recorded in the NH, CH, and OH stretch range of the cation ground electronic state. Analysis of the size-dependent frequency shifts by dispersion-corrected density functional theory calculations (B3LYP-D3/cc-pVTZ) provides detailed information about the acidity of the protons of the NH2 group of Ama+ and the structure and strength of the NHO and OHO hydrogen bonds (H-bonds) of the hydration network. The preferred sequential cluster growth begins with hydration of the two acidic NH protons of the NH2 group (n = 1-2) and continues with an extension of the H-bonded hydration network by forming an OHO H-bond of the third W to one ligand in the first hydration subshell (n = 3), like in the W2 dimer. For n = 2, a minor population corresponds to Ama+W2 structures with a W2 unit attached to Ama+via a NHW2 H-bond. Although the N-H proton donor bonds are progressively destabilized by gradual microhydration, no proton transfer to the Wn solvent cluster is observed in the investigated size range (n ≤ 3). Besides the microhydration structure, we also obtain a first impression of the structure and IR spectrum of bare Ama+, as well as the effects of both ionization and hydration on the structure of the adamantyl cage. Comparison of Ama+ with aliphatic and aromatic primary amine radical cations reveals differences in the acidity of the NH2 group and the resulting interaction with W caused by substitution of the cycloalkyl cage.
Collapse
|
12
|
George MAR, Förstel M, Dopfer O. Infrared Spectrum of the Adamantane + -Water Cation: Hydration-Induced C-H Bond Activation and Free Internal Water Rotation. Angew Chem Int Ed Engl 2020; 59:12098-12104. [PMID: 32392402 PMCID: PMC7383494 DOI: 10.1002/anie.202003637] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Indexed: 12/21/2022]
Abstract
Diamondoid cations are reactive intermediates in their functionalization reactions in polar solution. Hydration is predicted to strongly activate their C-H bonds in initial proton abstraction reactions. To study the effects of microhydration on the properties of diamondoid cations, we characterize herein the prototypical monohydrated adamantane cation (C10 H16 + -H2 O, Ad+ -W) in its ground electronic state by infrared photodissociation spectroscopy in the CH and OH stretch ranges and dispersion-corrected density functional theory (DFT) calculations. The water (W) ligand binds to the acidic CH group of Jahn-Teller distorted Ad+ via a strong CH⋅⋅⋅O ionic H-bond supported by charge-dipole forces. Although W further enhances the acidity of this CH group along with a proton shift toward the solvent, the proton remains with Ad+ in the monohydrate. We infer essentially free internal W rotation from rotational fine structure of the ν3 band of W, resulting from weak angular anisotropy of the Ad+ -W potential.
Collapse
Affiliation(s)
- Martin Andreas Robert George
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany
| | - Marko Förstel
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany
| | - Otto Dopfer
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany
| |
Collapse
|