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1.
Choi CM Choi DH Heo J Kim NJ Kim SK 《Angewandte Chemie (International ed. in English)》2012,51(29):7297-7300
Conformation selective: A new technique of ultraviolet-ultraviolet hole burning spectroscopy that can be applied to ions stored in a quadrupole ion trap (QIT) is developed and used to obtain the conformation-selective electronic spectra of dibenzo[18]crown-6 complexes with alkali metal cations (M(+), see picture; F(+) = fragment). 相似文献
2.
Gas‐Phase Interactions between Lead(II) Ions and Cytosine: Tandem Mass Spectrometry and Infrared Multiple‐Photon Dissociation Spectroscopy Study
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Dr. Jean‐Yves Salpin Violette Haldys Dr. Sébastien Guillaumont Prof. Jeanine Tortajada Marcela Hurtado Prof. Al Mokhtar Lamsabhi 《Chemphyschem》2014,15(14):2959-2971
Gas‐phase interactions between Pb2+ ions and cytosine (C) were studied by combining tandem mass spectrometry, infrared multiple photon dissociation spectroscopy, and density functional theory (DFT) calculations. Both singly and doubly charged complexes were generated by electrospray. The [Pb(C)?H]+ complex was extensively studied, and this study shows that two structures, involving the interaction of the metal with the deprotonated canonical keto‐amino tautomer of cytosine, are generated in the gas phase; the prominent structure is the bidentate form involving both the N1 and O2 electronegative centers. The DFT study also points out a significant charge transfer from the nucleobase to the low‐lying p orbitals of the metal and a strong polarization of the base upon complexation. The various potential energy surfaces explored to account for the fragmentation observed are consistent with the high abundance of the [PbNH2]+ fragment ion. 相似文献
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Eberlin MN 《Journal of mass spectrometry : JMS》2006,41(2):141-156
This article discusses the application of gas-phase ion/molecule reactions for fine structural elucidation in mass spectrometry. This approach is illustrated via a representative collection of class- and functional group-selective reactions, a few of historical relevance as well as by more recent and instructive examples, and their applications. The focus is on reactions performed under well-controlled conditions of sequential mass spectrometry, discussing key mechanistic details and potential applications. Recent and innovative strategies that allow these reactions to be performed under ambient conditions, making this fast, selective and sensitive approach for structural investigation much more generally applicable, are also discussed. 相似文献
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The protonation sites and structures of a series of protonated amino acids (Gly, Ala, Pro, Phe, Lys and Ser) are investigated by means of infrared multiple‐photon dissociation (IRMPD) spectroscopy and electronic‐structure calculations. The IRMPD spectra of the protonated species are recorded using the combination of a free‐electron laser (FEL) and an electrospray‐ion‐trap mass spectrometer. The structures of different possible isomers of these protonated species are optimized at the B3LYP/6‐311+G(d, p) level of theory and the IR spectra calculated using the same computational method. For every amino acid studied herein, the current results indicate that a proton is bound to the α‐amino nitrogen, except for lysine, in which the protonation site is the amino nitrogen in the side chain. According to the calculated and experimental IRMPD results, the structures of the protonated amino acids may be assigned unambiguously. For Gly, Ala, and Pro, in each of the most stable isomers the protonated amino group forms an intramolecular hydrogen bond with the adjacent carbonyl oxygen. In the case of Gly, the isomer containing a proton bound to the carbonyl oxygen is theoretically possible. However, it does not exist under the experimental conditions because it has a significantly higher energy (i.e. 26.6 kcal mol?1) relative to the most stable isomer. For Ser and Phe, the protonated amino group forms two intramolecular hydrogen bonds with both the adjacent carbonyl oxygen and the side‐chain group in each of the most stable isomers. In protonated lysine, the protonated amino group in the side chain forms two hydrogen bonds with the α‐amino nitrogen and the carbonyl oxygen, which is a cyclic structure. Interestingly, for protonated lysine the zwitterionic structure is a local minimum energy isomer, but the experimental spectrum indicates that it does not exist under the experimental conditions. This is consistent with the fact that the zwitterionic isomer is 9.2 kcal mol?1 higher in free energy at 298 K than the most stable isomer. The carbonyl stretching vibration in the range of 1760–1800 cm?1 is especially sensitive to the structural change. In addition, IRMPD mechanisms for the protonated amino acids are also investigated. 相似文献
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二苯并四氮杂轮烯金属配合物及其亲电取代反应性能 总被引:1,自引:0,他引:1
本文用量子化学半经验方法和从头算研究二苯并四氮杂[14]轮烯离子及其金属配合物,讨论了轮烯配合物的活性位置。^1HNMR谱表明Lunxi-Ni配合物中金属离子对位C7、C16上的H原子被取代,与理论计算结果一致。 相似文献
6.
Back Cover: Characterization of Paramagnetic Reactive Intermediates: Predicting the NMR Spectra of Iron(IV)–Oxo Complexes by DFT (Chem. Eur. J. 37/2015)
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Dr. Andrea Borgogno Dr. Federico Rastrelli Prof. Alessandro Bagno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):13140-13140
7.
Characterization of Paramagnetic Reactive Intermediates: Predicting the NMR Spectra of Iron(IV)–Oxo Complexes by DFT
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Dr. Andrea Borgogno Dr. Federico Rastrelli Prof. Alessandro Bagno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(37):12960-12970
The relative energies of spin states of several iron(IV)–oxo complexes and related species have been calculated with DFT methods by employing the B3LYP* functional. We show that such calculations can predict the correct ground spin state of FeIV complexes and can then be used to determine the 1H NMR spectra of all spin states; the spectral features are remarkably different, hence calculated paramagnetic 1H NMR spectra can be used to support the structure elucidation of numerous paramagnetic complexes. Applications to a number of stable and reactive iron(IV)–oxo species are described. 相似文献
8.
Dr. Davide Corinti Dr. Alessandro Maccelli Prof. Barbara Chiavarino Dr. Markus Schütz Dr. Aude Bouchet Prof. Otto Dopfer Prof. Maria Elisa Crestoni Prof. Simonetta Fornarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200300
The structure of an isolated Ag+(benzylamine) complex is investigated by infrared multiple photon dissociation (IRMPD) spectroscopy complemented with quantum chemical calculations of candidate geometries and their vibrational spectra, aiming to ascertain the role of competing cation-N and cation-π interactions potentially offered by the polyfunctional ligand. The IRMPD spectrum has been recorded in the 800–1800 cm−1 fingerprint range using the IR free electron laser beamline coupled with an FT-ICR mass spectrometer at the Centre Laser Infrarouge d'Orsay (CLIO). The resulting IRMPD pattern points toward a chelate coordination (N-Ag+-π) involving both the amino nitrogen atom and the aromatic π-system of the phenyl ring. The gas-phase reactivity of Ag+(benzylamine) with a neutral molecular ligand (L) possessing either an amino/aza functionality or an aryl group confirms N- and π-binding affinity and suggests an augmented silver coordination in the product adduct ion . 相似文献
9.
Paola Antoniotti Lorenza Operti Roberto Rabezzana Francesca Turco Gian Angelo Vaglio Felice Grandinetti 《Journal of mass spectrometry : JMS》2009,44(5):725-734
The gas phase ion chemistry of silane/hydrogen sulfide and germane/hydrogen sulfide mixtures was studied by ion trap mass spectrometry (ITMS), in both positive and negative ionization mode. In positive ionization, formation of X/S (X = Si, Ge) mixed ions mainly takes place via reactions of silane or germane ions with H2S, through condensation followed by dehydrogenation. This is particularly evident in the system with silane. On the other side, reactions of HnS2+ ions with XH4 (X = Si, Ge) invariably lead to formation of a single X? S bond. In negative ionization, a more limited number of mixed ion species is detected, but their overall abundance reaches appreciable values, especially in the SiH4/H2S system. Present results clearly indicate that ion processes play an important role in formation and growth of clusters eventually leading to deposition of amorphous solids in chemical vapor deposition (CVD) processes. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
Anderson A. B. C. Júnior Gustavo S. G. De Carvalho Lippy F. Marques Charlane C. Corrêa Adilson D. Da Silva Flvia C. Machado 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(8):934-936
The title compound, C14H11NO4, exists in the solid phase in the zwitterionic form, 2‐{[(4‐carboxy‐3‐hydroxyphenyl)iminiumyl]methyl}phenolate, with the H atom from the phenol group on the 2‐hydroxybenzylidene ring transferred to the imine N atom, resulting in a strong intramolecular N—H...O hydrogen bond between the iminium H atom and the phenolate O atom, forming a six‐membered hydrogen‐bonded ring. In addition, there is an intramolecular O—H...O hydrogen bond between the carboxylic acid group and the adjacent hydroxy group of the other ring, and an intermolecular C—H...O contact involving the phenol group and the C—H group adjacent to the imine bond, connecting the molecules into a two‐dimensional network in the (10) plane. π–π stacking interactions result in a three‐dimensional network. This study is important because it provides crystallographic evidence, supported by IR data, for the iminium zwitterionic form of Schiff bases.<!?tpb=12pt> 相似文献
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Ionization of esters of carboxylic acids RCOOR' (R = H, alkyl; R' = alkyl) within the air plasma of the Atmospheric Pressure Chemical Ionization (APCI) source occurs largely via H(+)-transfer and, to a minor extent, via NO(+) association. The protonated ester MH(+) is normally observed as M(2)H(+) and as higher aggregates (M(3)H(+), M(3)H(+)(H(2)O)) also at high source temperature. The behavior of M(2)H(+) upon collisional activation is consistent with the reported dissociation of proton-bound dimers to MH(+) species that, in turn, fragment according to the known paths of lowest energy. In addition, other important product ions form within the plasma, some in very high relative abundance, which are attributed to ion-molecule condensation reactions between neutral M and either MH(+) or M(2)H(+) resulting in the elimination of CO, R'OH, alkene from the alkoxy moiety of the ester and HCOOH. A general scheme is proposed to account for the experimental observations, which suggest that the encounter complex formed between MH(+) and M or between M(2)H(+) and M may either collisionally relax to the protonated dimer or trimer, respectively, or react via covalent bond forming and cleaving steps to eliminate stable neutral molecules. The proposed scheme is supported by both the observed concentration dependence and the temperature dependence of the products relative abundances within the plasma. Such reactions can be the dominant process, as in the case of formate esters. A second significant ionization route involves addition of NO(+) to form M(n)NO(+) (n = 1, 2, 3). An additional product corresponding to [M(2)NO(+) - CO(2)] is also observed with iso- and n-butyl formate esters. 相似文献
13.
Burney C Carmichael D Forissier K Green JC Mathey F Ricard L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(11):2567-2573
The reduction of the phosphacobaltocenium salt [CoCp*(2,5-PC(4)tBu(2)H(2))](+)[BPh(4)](-) (3; Cp*=pentamethylcyclopentadienyl) by magnesium in tetrahydrofuran (THF) furnishes the stable air-sensitive phosphacobaltocene [CoCp*(2,5-PC(4)tBu(2)H(2))] (4) in yields of up to 80 %. The crystal structure of 4 shows long Co-C(alpha) and short C(alpha)-C(beta)bonds in the phospholyl ligand, consistent with a semi-occupied molecular orbital (SOMO) having a" symmetry. A combined Amsterdam density functional (ADF)/photoelectron spectroscopic study, which confirms this assignment, gives ionisation energies (IE) of 5.02 eV from the SOMO and 8.89 eV from the phosphorus "lone pair". A comparison of cyclovoltammograms for 3 and the corresponding cyclopentadienyl complex [CoCp*(1,3-C(5)tBu(2)H(3))](+) [BPh(4)](-)(5) shows that replacing a CH group by an sp(2) phosphorus atom results in an anodic first reduction potential shift of 0.29 V. 相似文献
14.
This perspective gives an overview of the action spectroscopy methods for measurements of electronic, vibrational, and rotational spectra of mass-selected ions in the gas phase. We classify and give a short overview of the existing experimental approaches in this field. There is currently a plethora of names used for, essentially, the same techniques. Hence within this overview, we scrutinized the notations and suggested terms to be generally used. The selection was either driven by making the name unique and straightforward or the term being the most broadly used one. We believe that a simplification and a unification of the notation in ion spectroscopy can make this field better accessible for experts outside the mass spectrometry community where the applications of gas-phase action ion spectroscopy can make a large impact. 相似文献
15.
Prof. Barbara Chiavarino Prof. Rajeev K. Sinha Prof. Maria Elisa Crestoni Dr. Davide Corinti Prof. Antonello Filippi Prof. Caterina Fraschetti Prof. Debora Scuderi Prof. Philippe Maitre Prof. Simonetta Fornarini 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2348-2360
The structures of proton-bound complexes of 5,7-dimethoxy-4H-chromen-4-one ( 1 ) and basic amino acids (AAs), namely, histidine (His) and lysine (Lys), have been examined by means of mass spectrometry coupled with IR ion spectroscopy and quantum chemical calculations. This selection of systems is based on the fact that 1 represents a portion of glabrescione B, a natural small molecule of promising antitumor activity, while His and Lys are protein residues lining the cavity of the alleged receptor binding site. These species are thus a model of the bioactive adduct, although clearly the isolated state of the present study bears little resemblance to the complex biological environment. A common feature of [ 1 +AA+H]+ complexes is the presence of a protonated AA bound to neutral 1 , in spite of the fact that the gas-phase basicity of 1 is comparable to those of Lys and His. The carbonyl group of 1 acts as a powerful hydrogen-bond acceptor. Within [ 1 +AA+H]+ the side-chain substituents (imidazole group for His and terminal amino group for Lys) present comparable basic properties to those of the α-amino group, taking part to a cooperative hydrogen-bond network. Structural assignment, relying on the comparative analysis of the infrared multiple photon dissociation (IRMPD) spectrum and calculated IR spectra for the candidate geometries, derives from an examination over two frequency ranges: 900–1800 and 2900–3700 cm−1. Information gained from the latter one proved especially valuable, for example, pointing to the contribution of species characterized by an unperturbed carboxylic OH or imidazole NH stretching mode. 相似文献
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Sayaka Kira Takayuki Miyamae Dr. Kohei Yoshida Dr. Yuki Kanzaki Dr. Kenji Sugisaki Prof. Dr. Daisuke Shiomi Prof. Dr. Kazunobu Sato Prof. Dr. Takeji Takui Dr. Shuichi Suzuki Prof. Dr. Masatoshi Kozaki Prof. Dr. Keiji Okada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(44):11450-11457
Multinuclear AuI complexes with two or three nitronyl nitroxide-2-ide radical anion and phosphine-ligand scaffolds, (NN-Au)2-1 o , (NN-Au)2-1 m , and (NN-Au)2-1 p , have been synthesized to investigate the influence of AuI−AuI (aurophilic) interactions on the properties of multispin molecular systems. The desired complexes were successfully prepared in moderate yields in a one-pot synthesis from the corresponding phosphine ligand, AuI source, parent NN, and sodium hydroxide. Among the prepared complexes, (NN-Au)2-1 o , in which an aurophilic interaction was clearly observed by crystal structure analysis, showed characteristic spin−spin interactions, electrochemical properties, and solvatochromic behavior. The results from theoretical calculations also suggested that the differences in properties between complex (NN-Au)2-1 o and the other complexes are due to intramolecular aurophilic interactions. 相似文献
19.
L. N. Mazalov S. V. Trubina E. S. Fomin I. M. Oglezneva G. K. Parygina N. V. Bausk I. K. Igumenov 《Journal of Structural Chemistry》2004,45(5):800-807
The Cu(acac)2 complex was investigated by X-ray emission and XANES spectroscopy using synchrotron radiation. Structural data for the complex were obtained in chloroform solution and C2F matrix. The experimental spectra and their fitting on a single scale of binding energies point to possible relaxation effects. As shown by model quantum-chemical calculations, the structure and energy position of the LUMOs constructed from the vacant metal 4p, 5p AOs strongly depends on the nature of the nearest environment.Original Russian Text Copyright © 2004 by L. N. Mazalov, S. V. Trubina, E. S. Fomin, I. M. Oglezneva, G. K. Parygina, N. V. Bausk, and I. K. Igumenov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 844–851, September–October, 2004. 相似文献
20.
Rogelio J. Gómez-Piñeiro Dr. Dimitrios A. Pantazis Dr. Maylis Orio 《Chemphyschem》2020,21(24):2667-2679
The reliable prediction of Cu(II) hyperfine coupling constants remains a challenge for quantum chemistry. Until recently only density functional theory (DFT) could target this property for systems of realistic size. However, wave function based methods become increasingly applicable. In the present work, we define a large set of Cu(II) complexes with experimentally known hyperfine coupling constants and use it to investigate the performance of modern quantum chemical methods for the prediction of this challenging spectroscopic parameter. DFT methods are evaluated against orbital-optimized second-order Møller-Plesset (OO-MP2) theory and coupled cluster calculations including singles and doubles excitations, driven by the domain-based local pair natural orbital approach (DLPNO-CCSD). Special attention is paid to the definition of a basis set that converges adequately toward the basis set limit for the given property for all methods considered in this study, and a specifically optimized basis set is proposed for this purpose. The results suggest that wave function based methods can supplant but do not outcompete DFT for the calculation of Cu(II) hyperfine coupling constants. Mainstream hybrid functionals such as B3PW91 remain on average the best choice. 相似文献