1
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Gámez F, Avilés-Moreno JR, Berden G, Oomens J, Martínez-Haya B. Proton in the ring: spectroscopy and dynamics of proton bonding in macrocycle cavities. Phys Chem Chem Phys 2021; 23:21532-21543. [PMID: 34549205 DOI: 10.1039/d1cp03033g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The proton bond is a paradigmatic quantum molecular interaction and a major driving force of supramolecular chemistry. The ring cavities of crown ethers provide an intriguing environment, promoting competitive proton sharing with multiple coordination anchors. This study shows that protons confined in crown ether cavities form dynamic bonds that migrate to varying pairs of coordinating atoms when allowed by the flexibility of the macrocycle backbone. Prototypic native crown ethers (12-crown-4, 15-crown-5 and 18-crown-6) and aza-crown ethers (cyclen, 1-aza-18-crown-6 and hexacyclen) are investigated. For each system, Infrared action spectroscopy experiments and ab initio Molecular Dynamics computations are employed to elucidate the structural effects associated with proton diffusion and its entanglement with the conformational and vibrational dynamics of the protonated host.
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Affiliation(s)
- Francisco Gámez
- Department of Physical Chemistry, Universidad de Granada, Avenida de la Fuente Nueva s/n, 18071, Granada, Spain
| | - Juan R Avilés-Moreno
- Department of Applied Physical Chemistry, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Giel Berden
- FELIX Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525ED Nijmegen, The Netherlands
| | - Jos Oomens
- FELIX Laboratory, Institute for Molecules and Materials, Radboud University, Toernooiveld 7, 6525ED Nijmegen, The Netherlands
| | - Bruno Martínez-Haya
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. de Utrera, km. 1, 41013 Seville, Spain.
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2
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Martens J, van Outersterp RE, Vreeken RJ, Cuyckens F, Coene KLM, Engelke UF, Kluijtmans LAJ, Wevers RA, Buydens LMC, Redlich B, Berden G, Oomens J. Infrared ion spectroscopy: New opportunities for small-molecule identification in mass spectrometry - A tutorial perspective. Anal Chim Acta 2019; 1093:1-15. [PMID: 31735202 DOI: 10.1016/j.aca.2019.10.043] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 10/19/2019] [Accepted: 10/21/2019] [Indexed: 01/21/2023]
Abstract
Combining the individual analytical strengths of mass spectrometry and infrared spectroscopy, infrared ion spectroscopy is increasingly recognized as a powerful tool for small-molecule identification in a wide range of analytical applications. Mass spectrometry is itself a leading analytical technique for small-molecule identification on the merit of its outstanding sensitivity, selectivity and versatility. The foremost shortcoming of the technique, however, is its limited ability to directly probe molecular structure, especially when contrasted against spectroscopic techniques. In infrared ion spectroscopy, infrared vibrational spectra are recorded for mass-isolated ions and provide a signature that can be matched to reference spectra, either measured from standards or predicted using quantum-chemical calculations. Here we present an overview of the potential for this technique to develop into a versatile analytical method for identifying molecular structures in mass spectrometry-based analytical workflows. In this tutorial perspective, we introduce the reader to the technique of infrared ion spectroscopy and highlight a selection of recent experimental advances and applications in current analytical challenges, in particular in the field of untargeted metabolomics. We report on the coupling of infrared ion spectroscopy with liquid chromatography and present experiments that serve as proof-of-principle examples of strategies to address outstanding challenges.
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Affiliation(s)
- Jonathan Martens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, the Netherlands.
| | - Rianne E van Outersterp
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, the Netherlands
| | - Rob J Vreeken
- Drug Metabolism & Pharmacokinetics, Janssen R&D, Beerse, Belgium
| | - Filip Cuyckens
- Drug Metabolism & Pharmacokinetics, Janssen R&D, Beerse, Belgium
| | - Karlien L M Coene
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Udo F Engelke
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Leo A J Kluijtmans
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Ron A Wevers
- Department of Laboratory Medicine, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Lutgarde M C Buydens
- Radboud University, Institute for Molecules and Materials, Chemometrics, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands
| | - Britta Redlich
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, the Netherlands
| | - Giel Berden
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, the Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, the Netherlands; van't Hoff Institute for Molecular Sciences, University of Amsterdam, 1098XH, Amsterdam, Science Park 908, the Netherlands.
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3
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Yatsyna V, Mallat R, Gorn T, Schmitt M, Feifel R, Rijs AM, Zhaunerchyk V. Conformational Preferences of Isolated Glycylglycine (Gly-Gly) Investigated with IRMPD-VUV Action Spectroscopy and Advanced Computational Approaches. J Phys Chem A 2019; 123:862-872. [DOI: 10.1021/acs.jpca.8b10881] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Vasyl Yatsyna
- Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden
- Radboud University, Institute of Molecules and Materials, FELIX Laboratory, Toernoovield 7-c, 6525 ED Nijmegen, The Netherlands
| | - Ranim Mallat
- Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - Tim Gorn
- Institut für Physikalische Chemie I, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| | - Michael Schmitt
- Institut für Physikalische Chemie I, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| | - Raimund Feifel
- Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden
| | - Anouk M. Rijs
- Radboud University, Institute of Molecules and Materials, FELIX Laboratory, Toernoovield 7-c, 6525 ED Nijmegen, The Netherlands
| | - Vitali Zhaunerchyk
- Department of Physics, University of Gothenburg, 412 96 Gothenburg, Sweden
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4
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Avilés-Moreno JR, Berden G, Oomens J, Martínez-Haya B. Complexes of Crown Ether Macrocycles with Methyl Guanidinium: Insights into the Capture of Charge in Peptides. Chemphyschem 2018; 19:2169-2175. [PMID: 29944200 DOI: 10.1002/cphc.201800596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Indexed: 11/08/2022]
Abstract
Crown ethers are well known as modulating agents of protein function and interactions. The action of crown ethers is driven by an alteration of the charged moieties of proteins through the capping of cationic amino acid side chains. This study evaluates the conformational features involved in the binding of crown ethers to the side chain of arginine. For this purpose, isolated complexes of methyl guanidinium with 12-crown-4 and 18-crown-6 are characterized with infrared action vibrational spectroscopy and quantum chemical computations. The conformational landscapes of the two complexes comprise an extensive ensemble of conformations close in energy. In the 12-crown-4 complex, the crown ether has the plane of its backbone approximately perpendicular to that of the guanidinium moiety and coordinates to two or three of its NHδ+ bonds. In the 18-crown-6 complex, the crown ether backbone is partially folded and tilted with respect to guanidinium and fixes its position in order to facilitate up to a four-fold coordination in the complex. The access of the complexes to multiple conformations leads to broad band structures in the N-H stretching region of their vibrational spectra.
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Affiliation(s)
- Juan Ramón Avilés-Moreno
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, 41013, Seville, Spain
| | - Giel Berden
- Radboud University, Institute for Molecules and Materials FELIX Laboratory, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials FELIX Laboratory, Toernooiveld 7c, 6525ED, Nijmegen, The Netherlands
| | - Bruno Martínez-Haya
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, 41013, Seville, Spain
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5
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Avilés-Moreno JR, Berden G, Oomens J, Martínez-Haya B. Intra-cavity proton bonding and anharmonicity in the anionophore cyclen. Phys Chem Chem Phys 2018; 20:8968-8975. [PMID: 29557457 DOI: 10.1039/c8cp00660a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Proton bonding drives the supramolecular chemistry of a broad range of materials with polar moieties. Proton delocalization and electronic charge redistribution have a profound impact on the structure of proton-bound molecular frameworks, and pose fundamental challenges to quantum chemical modelling. This study provides insights into the structural and spectral signatures of the intramolecular proton bond formed in a benchmark polyazamacrocycle anionophore (cyclen, 1,4,7,10-tetraazacyclododecane). Infrared action spectroscopy is employed to characterize the macrocycle, isolated in protonated form. In its most stable configuration, protonated cyclen adopts an open arrangement of Cs symmetry with a particularly strong NHδ+N bond across the cavity. The quantum chemical analysis of the infrared spectrum reveals intrinsic difficulties for the accurate description of the vibrational modes of the system. The reconciliation of the computational predictions with experiment demands a careful anharmonic treatment of the proton motion, which exposes the limitations of current methods. Best results are obtained with the incorporation of anharmonicity only to the fundamental modes directly related to motions of the proton. However, the full anharmonic treatment of the system fails to describe correctly the vibrations related to the macrocycle backbone. The results should serve as motivation for new developments in the modelling of proton bonded systems.
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Affiliation(s)
- Juan Ramón Avilés-Moreno
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, E-41013 Seville, Spain.
| | - Giel Berden
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen, The Netherlands
| | - Bruno Martínez-Haya
- Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, E-41013 Seville, Spain.
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6
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Reid JESJ, Bernardes CES, Agapito F, Martins F, Shimizu S, Minas da Piedade ME, Walker AJ. Structure-property relationships in protic ionic liquids: a study of solvent-solvent and solvent-solute interactions. Phys Chem Chem Phys 2018; 19:28133-28138. [PMID: 29022017 DOI: 10.1039/c7cp05076c] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ionic nature of a functionalized protic ionic liquid cannot be rationalized simply through the differences in aqueous proton dissociation constants between the acid precursor and the conjugate acid of the base precursor. The extent of proton transfer, i.e. the equilibrium ionicity, of a tertiary ammonium acetate protic ionic liquid can be significantly increased by introducing an hydroxyl functional group on the cation, compared to the alkyl or amino-functionalized analogues. This increase in apparent ionic nature correlates well with variations in solvent-solute and solvent-solvent interaction parameters, as well as with physicochemical properties such as viscosity.
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Affiliation(s)
- Joshua E S J Reid
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
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7
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Kwocz A, Jan Panek J, Jezierska A, Hetmańczyk Ł, Pawlukojć A, Kochel A, Lipkowski P, Filarowski A. A molecular roundabout: triple cyclically arranged hydrogen bonds in light of experiment and theory. NEW J CHEM 2018. [DOI: 10.1039/c8nj04339f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This paper dwells on the synthesis and diverse studies of cyclically arranged hydrogen bridges in tris-hydroxy aryl Schiff bases. Experimental (IINS, IR, Raman and X-ray) and theoretical (CPMD, DFTP and DFT) studies of tris-hydroxy aryl Schiff bases have been performed in the solid state.
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Affiliation(s)
- Agnieszka Kwocz
- Faculty of Chemistry
- University of Wrocław
- 50-383 Wrocław
- Poland
| | | | - Aneta Jezierska
- Faculty of Chemistry
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Łukasz Hetmańczyk
- Faculty of Chemistry
- Jagiellonian University
- 30-387 Kraków
- Poland
- Frank Laboratory of Neutron Physics
| | - Andrzej Pawlukojć
- Frank Laboratory of Neutron Physics
- Joint Institute for Nuclear Research
- 141980 Dubna
- Russia
- Institute of Nuclear Chemistry and Technology
| | - Andrzej Kochel
- Faculty of Chemistry
- University of Wrocław
- 50-383 Wrocław
- Poland
| | - Paweł Lipkowski
- Department of Physical and Quantum Chemistry
- Faculty of Chemistry
- Wrocław University of Science and Technology
- 50-370 Wrocław
- Poland
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8
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Carita Correra T, Santos Fernandes A, Mota Reginato M, Colucci Ducati L, Berden G, Oomens J. Probing the geometry reorganization from solution to gas-phase in putrescine derivatives by IRMPD, 1H-NMR and theoretical calculations. Phys Chem Chem Phys 2017; 19:24330-24340. [DOI: 10.1039/c7cp04617k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Geometry reorganization of ESI formed ions are demonstrated and explicit calculations of the solution phase are shown to be relevant.
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Affiliation(s)
- Thiago Carita Correra
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - André Santos Fernandes
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Marcelo Mota Reginato
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Lucas Colucci Ducati
- Department of Fundamental Chemistry
- Institute of Chemistry
- University of São Paulo
- São Paulo
- Brazil
| | - Giel Berden
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
| | - Jos Oomens
- Radboud University
- Institute for Molecules and Materials
- FELIX Laboratory
- 6525 ED Nijmegen
- The Netherlands
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9
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Reid JESJ, Agapito F, Bernardes CES, Martins F, Walker AJ, Shimizu S, Minas da Piedade ME. Structure–property relationships in protic ionic liquids: a thermochemical study. Phys Chem Chem Phys 2017; 19:19928-19936. [DOI: 10.1039/c7cp02230a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How does cation functionality influence the strength of intermolecular interactions in protic ionic liquids (PILs)? Quantifying the energetics of PILs can be an invaluable tool to answer this fundamental question.
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Affiliation(s)
- Joshua E. S. J. Reid
- York Structural Biology Laboratory
- Department of Chemistry
- University of York
- Heslington
- York
| | - Filipe Agapito
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Carlos E. S. Bernardes
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Filomena Martins
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | | | - Seishi Shimizu
- York Structural Biology Laboratory
- Department of Chemistry
- University of York
- Heslington
- York
| | - Manuel E. Minas da Piedade
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
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10
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Paciotti R, Corinti D, De Petris A, Ciavardini A, Piccirillo S, Coletti C, Re N, Maitre P, Bellina B, Barran P, Chiavarino B, Elisa Crestoni M, Fornarini S. Cisplatin and transplatin interaction with methionine: bonding motifs assayed by vibrational spectroscopy in the isolated ionic complexes. Phys Chem Chem Phys 2017; 19:26697-26707. [DOI: 10.1039/c7cp05203k] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
IRMPD spectroscopy discloses N- versus S-platination.
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11
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Rao J, Fernández-Ronco MP, Vong M, Gaan S. Enhanced flame-retardancy and controlled physical properties of flexible polyurethane foams based on a shear-responsive internal network. RSC Adv 2017. [DOI: 10.1039/c7ra07083g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The flame retardancy of FPUFs can be enhanced by the manipulation of the solid-polymer interface chemistry.
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Affiliation(s)
- Jingyi Rao
- Laboratory of Advanced Fibers
- Functional Materials
- Swiss Federal Laboratories for Materials Science and Technology
- St. Gallen
- Switzerland
| | - María P. Fernández-Ronco
- Laboratory of Advanced Fibers
- Functional Materials
- Swiss Federal Laboratories for Materials Science and Technology
- St. Gallen
- Switzerland
| | - Michel Vong
- Laboratory of Advanced Fibers
- Functional Materials
- Swiss Federal Laboratories for Materials Science and Technology
- St. Gallen
- Switzerland
| | - Sabyasachi Gaan
- Laboratory of Advanced Fibers
- Functional Materials
- Swiss Federal Laboratories for Materials Science and Technology
- St. Gallen
- Switzerland
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12
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Pearson WL, Contreras C, Powell D, Berden G, Oomens J, Bendiak B, Eyler JR. Differentiation of Rubidiated Methyl-d-Glycoside Stereoisomers by Infrared Multiple-Photon Dissociation Spectroscopy in the O–H and C–H Stretching Regions. J Phys Chem B 2015; 119:12970-81. [DOI: 10.1021/acs.jpcb.5b06563] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wright L. Pearson
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Cesar Contreras
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - David Powell
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
| | - Giel Berden
- Radboud University, Institute for Molecules and
Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and
Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
- University of Amsterdam, Science
Park 904, 1098XH Amsterdam, The Netherlands
| | - Brad Bendiak
- Department
of Cell and Developmental Biology and Program in Structural Biology
and Biochemistry, University of Colorado Health Sciences Center, Denver, Colorado 80045, United States
| | - John R. Eyler
- Department
of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States
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13
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Ledvina AR, Coon JJ, Tureček F. Competitive Hydrogen Atom Migrations Accompanying Cascade Dissociations of Peptide Cation-Radicals of the z+• Type. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2015; 377:44-53. [PMID: 25844055 PMCID: PMC4380023 DOI: 10.1016/j.ijms.2014.02.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report a combined experimental and computational study of energy-resolved collision-induced dissociation (ER-CID) and time-resolved infrared multiphoton dissociation (TR-IRMPD) of z4 ions prepared by electron transfer dissociation of peptide (Ala-Ala-Asn-Ala-Arg + 2H)2+ ions. The z4 cation-radicals, •ANAR+, undergo competitive dissociations by backbone cleavage and loss of a CONH2 radical from the Asn side chain. The backbone cleavage proceeds by radical-assisted dissociation of the Asn Cα-CO bond, forming an x2 ion intermediate which rapidly dissociates by HNCO elimination to yield a stable z2 fragment ion, •AR+. The ER-CID and TR-IRMPD data were consistent with the consecutive nature of the backbone dissociation but showed different branching ratios for the two major fragmentations. The ER-CID data showed branching ratios 0.6-1.0 for the side-chain and backbone cleavages whereas the TR-IRMPD data showed an earlier onset for the latter dissociation. Computational analysis of the potential energy surface with density functional theory and ab initio calculations was carried out to provide structures and energies for the reactant ions as well as several intermediates, products, and transition states. Dissociation pathways for cis and trans amide conformers were distinguished and their energies were evaluated. The threshold dissociation energies for the backbone and side-chain dissociations were similar in accordance with the experimental ER-CID branching ratio. The TR-IRMPD data were interpreted by different absorbances of intermediates produced by hydrogen atom migrations along the dissociation pathways.
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Affiliation(s)
- Aaron R Ledvina
- Department of Chemistry, University of Wisconsin, Madison, WI, USA
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin, Madison, WI, USA ; Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI, USA
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, WA 98195-1700, USA
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14
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Ung HU, Moehlig AR, Kudla RA, Mueller LJ, Oomens J, Berden G, Morton TH. Proton-bound dimers of 1-methylcytosine and its derivatives: vibrational and NMR spectroscopy. Phys Chem Chem Phys 2014; 15:19001-12. [PMID: 24096726 DOI: 10.1039/c3cp52260a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Vibrational spectroscopy and NMR demonstrate that the proton-bound dimer of 1-methylcytosine, 1, has an unsymmetrical structure at room temperature. In the gas phase, investigation of isolated homodimer 1 reveals five fundamental NH vibrations by IR Multiple Photon Dissociation (IRMPD) action spectroscopy. The NH···N stretching vibration between the two ring nitrogens exhibits a frequency of 1570 cm(-1), as confirmed by examination of the proton-bound homodimers of 5-fluoro-1-methycytosine, 2, and of 1,5-dimethylcytosine, 3, which display absorptions in the same region that disappear upon deuterium substitution. (13)C, and (15)N NMR of the solid iodide salt of 1 confirm the nonequivalence of the two rings in the anhydrous proton-bound homodimer at room temperature. IRMPD spectra of the three possible heterodimers also show NH···N stretches in the same domain, and at least one of the heterodimers, the proton-bound dimer of 1,5-dimethylcytosine with 1-methylcytosine, exhibits two bands suggestive of the presence of two tautomers close in energy.
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Affiliation(s)
- Hou U Ung
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
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