1
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Bao W, Gu G, Wu J, Gu YC, Zhao Y. Detection and Identification of Nitrile Compounds via Recognition-Enabled Chromatographic 19F NMR. Anal Chem 2024; 96:4463-4468. [PMID: 38462969 DOI: 10.1021/acs.analchem.3c04909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
The surge in applications of nitrile compounds across diverse fields, such as pharmaceuticals, agrochemicals, dyes, and functional materials, necessitates the development of rapid and efficient detection and identification methods. In this study, we introduce a chemosensing strategy employing a novel 19F-labeled probe, facilitating swift and accurate analysis of a broad spectrum of nitrile-containing analytes. This approach leverages the reversible interaction between the 19F-labeled probe and the analytes to produce chromatogram-like outputs, ensuring the precise identification of various pharmaceuticals and pesticides within complex matrices. Additionally, this dynamic system offers a versatile platform to investigate through-space 19F-19F interactions, showcasing its potential for future applications in mechanistic studies.
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Affiliation(s)
- Wenjing Bao
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China
| | - Guangxing Gu
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China
| | - Jian Wu
- Instrumental Analysis Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yu-Cheng Gu
- Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, U.K
| | - Yanchuan Zhao
- Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China
- Instrumental Analysis Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
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2
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Raghava T, Chattopadhyay A, Banerjee S, Sarkar N. Conversion of amino-terephthalonitriles to multi-substituted single benzene fluorophores with utility in bioimaging. Org Biomol Chem 2024; 22:364-373. [PMID: 38086694 DOI: 10.1039/d3ob01761c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Substitution of two fluorine atoms of the tetrafluoroterephthalonitrile (TFTN) ring (ortho to each other) by amine nucleophiles through SNAr chemistry is achievable. However, tri- and tetra-substitution towards multi-substituted single benzene fluorophores (SBFs) is harder due to increased electron richness of the TFTN moiety. Tertiary amine donors promote the molecule towards such multi-substitution guided by the steric obstruction to intramolecular charge transfer to the TFTN ring. Contrarily, secondary amine substituents with better lone pair donation to the TFTN ring cannot induce the SNAr pathway and instead promote hydrolysis of the nitrile groups of the TFTN moiety. Theoretical investigations have helped unearth the reasons for this observed difference in chemical reactivities and also explain the differences in the emission spectra. Finally, the success of the synthetic method towards multi-substitution is showcased through creation of a highly lipophilic SBF bearing an octyl unit and demonstrating its utility in in vitro cellular imaging.
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Affiliation(s)
- Tanya Raghava
- Birla Institute of Technology and Science Pilani KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India.
| | - Anjan Chattopadhyay
- Birla Institute of Technology and Science Pilani KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India.
| | - Subhadeep Banerjee
- Birla Institute of Technology and Science Pilani KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India.
- Fluoresight Bioprobes Private Limited, BGIIES Bioncubator, BITS Pilani KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India
| | - Nivedita Sarkar
- Fluoresight Bioprobes Private Limited, BGIIES Bioncubator, BITS Pilani KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India
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3
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Chen X, Bu Y. Enhanced J-Couplings through Specially Solvated Electron in Perfluoro-[ n]Prismanes and [ n]Asteranes. J Phys Chem A 2023; 127:9672-9683. [PMID: 37942900 DOI: 10.1021/acs.jpca.3c04257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Perfluoro-[n]prismanes ((C2F2)n, n = 3-8) and [n]asteranes ((C3F4)n, n = 3-5) exhibit a strong perfluoro cage effect that can stably encapsulate an additional electron inside the cage. The 2s-like distribution of solvated electron (esol-) not only changes the molecular structure but also affects the nuclear spin properties. In this work, we reveal how the esol- enhances and regulates indirect nuclear spin-spin coupling between two coupled F nuclei (JFF-coupling). Results show that esol- is mainly distributed in the central cavity, and a part of it penetrates into the C-shell and C-F bond regions due to the unique polyhedral C-shell structure. Such a 2s-like esol- creates a novel esol- based coupling mechanism, including the newly generated through-esol- (TSE) and esol--enhanced traditional through-bonds and through-space (esol--enhanced TB+TS) pathways, enhancing and regulating N(e)JFF-coupling, which crosses N bonds in the shortest TB pathway and is affected by esol-. The contribution of the TSE (JTSE) is positive and increases with the increase of the central angle between two coupled F nuclei (∠F⊗F), and the contribution of the esol--enhanced TB+TS (JTB+TS) is negative and |JTB+TS| decreases with the increase of N and straight linear distance between two coupled F nuclei (dFF). Interestingly, N(e)JFF exhibits a special dependence on N/dFF and ∠F⊗F due to the cooperation and competition between JTSE and JTB+TS. When ∠F⊗F < 70°, the esol--enhanced TB+TS can play a role; JTB+TS determines sign and magnitude of N(e)JFF. When ∠F⊗F > 70°, the TSE dominates, and JTSE determines sign and magnitude of N(e)JFF. This work not only further enriches information on the states, distributions, and properties of esol- but also provides insights into the nuclei spin properties in perfluorinated polyhedrons triggered by esol-.
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Affiliation(s)
- Xiao Chen
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China
| | - Yuxiang Bu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, People's Republic of China
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4
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Raghava T, Banerjee S, Chattopadhyay A. Diamino-Terephthalonitrile-based Single Benzene Fluorophores Featuring Strong Solution State Fluorescence and Large Stokes Shifts. J Org Chem 2023; 88:15708-15716. [PMID: 37931905 DOI: 10.1021/acs.joc.3c01685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
1°- and 2°-amines react with tetrafluoroterephthalonitrile through SNAr chemistry, creating the strongly emissive para-diamino-terephthalonitrile type single benzene fluorophores. The regioselectivity of reaction is dictated by the sterics of the initial secondary amine adduct. The molecules exhibit strong green-yellow emission and large (nearly 150 nm) Stokes shifts. Excited state analysis reveals a cooperative effect between the para-positioned amino groups through the electron-poor terephthalonitrile unit resulting in the fluorescence amplification.
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Affiliation(s)
- Tanya Raghava
- Department of Chemistry, Birla Institute of Technology and Science Pilani, KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India
| | - Subhadeep Banerjee
- Department of Chemistry, Birla Institute of Technology and Science Pilani, KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India
| | - Anjan Chattopadhyay
- Department of Chemistry, Birla Institute of Technology and Science Pilani, KK Birla Goa Campus, NH 17B Bypass Road, Zuarinagar, Goa 403726, India
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5
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Fitzgerald SA, Payce EN, Horton PN, Coles SJ, Pope SJA. 2-(Thienyl)quinoxaline derivatives and their application in Ir(III) complexes yielding tuneable deep red emitters. Dalton Trans 2023; 52:16480-16491. [PMID: 37874197 DOI: 10.1039/d3dt02193a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The synthesis and characterisation of eleven different 2-(thienyl)quinoxaline species that incorporate different points of functionality, including at the thiophene or quinoxaline rings, are described. These species display variable fluorescence properties in the visible region (λem = 401-491 nm) depending upon the molecular structures and extent of conjugation. The series of 2-(thienyl)quinoxaline species were then investigated as cyclometalating agents for Ir(III) to yield [Ir(C^N)2(bipy)]PF6 (where C^N = the cyclometalated ligand; bipy = 2,2'-bipyridine). Eight complexes were successfully isolated and fully characterised by an array of spectroscopic and analytical techniques. Two Ir(III) examples were structurally characterised in the solid state using single crystal X-ray diffraction; both structures confirmed the proposed formulations and coordination spheres in each case showing that the thiophene coordinates via a Ir-C bond. The photophysical properties of the complexes revealed that each complex is luminescent under ambient conditions with a range of emission wavelengths observed (665-751 nm) indicating that electronic tuning can be achieved via both the thienyl and quinoxaline moieties.
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Affiliation(s)
- Sophie A Fitzgerald
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
| | - Ellie N Payce
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
| | - Peter N Horton
- UK National Crystallographic Service, Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Simon J Coles
- UK National Crystallographic Service, Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
| | - Simon J A Pope
- School of Chemistry, Main Building, Cardiff University, Cardiff CF10 3AT, UK.
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6
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Raghava T, Chattopadhyay A, Bhavana P, Banerjee S. Amino-Terephthalonitrile-Based Single Benzene Fluorophores with Large Stokes Shifts and Solvatochromic Behavior. Chem Asian J 2023; 18:e202201314. [PMID: 36892161 DOI: 10.1002/asia.202201314] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Revised: 02/25/2023] [Indexed: 03/03/2023]
Abstract
We have synthesized a small library of blue-to-green emissive single benzene-based fluorophores (SBFs) in a short synthetic sequence. The molecules exhibit good Stokes shift in the range of 60-110 nm and select examples also possess very high fluorescence quantum yields of up to 87%. Theoretical investigations into the ground state and excited state geometries of many of these compounds reveal that good degree of planarization between the electron donor secondary amines and electron accepting benzodinitrile units can be achieved under certain solvatochromic conditions, giving rise to the strongly fluorescent behavior. On the other hand, the excited state geometry which lacks co-planarity of the donor amine and the single benzene moiety can open up a non-fluorescent channel. Additionally, in molecules with a dinitrobenzene acceptor, the perpendicular nitro moieties render the molecules completely non-emissive.
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Affiliation(s)
- Tanya Raghava
- Department of Chemistry, BITS Pilani K.K. Birla Goa Campus, NH 17B, Bypass Road, Zuarinagar, Goa, 403726, India
| | - Anjan Chattopadhyay
- Department of Chemistry, BITS Pilani K.K. Birla Goa Campus, NH 17B, Bypass Road, Zuarinagar, Goa, 403726, India
| | - Purushothaman Bhavana
- Department of Chemistry, BITS Pilani K.K. Birla Goa Campus, NH 17B, Bypass Road, Zuarinagar, Goa, 403726, India
| | - Subhadeep Banerjee
- Department of Chemistry, BITS Pilani K.K. Birla Goa Campus, NH 17B, Bypass Road, Zuarinagar, Goa, 403726, India
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7
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Alkorta I, Popelier PLA. Linking the Interatomic Exchange-Correlation Energy to Experimental J-Coupling Constants. J Phys Chem A 2023; 127:468-476. [PMID: 36608277 PMCID: PMC9869393 DOI: 10.1021/acs.jpca.2c07693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The main aim of the current work is to find an experimental connection to the interatomic exchange-correlation energy as defined by the energy decomposition method Interacting Quantum Atoms (IQA). A suitable candidate as (essentially) experimental quantity is the nuclear magnetic resonance (NMR) J-coupling constant denoted 3J(H,H'), which a number of previous studies showed to correlate well with QTAIM's delocalization index (DI), which is essentially a bond order. Inspired by Karplus equations, here, we investigate correlations between 3J(H,H') and a relevant dihedral angle in six simple initial compounds of the shape H3C-YHn (Y = C, N, O, Si, P, and S), N-methylacetamide (as prototype of the peptide bond), and five peptide-capped amino acids (Gly, Ala, Val, Ile, and Leu) because of the protein direction of the force field FFLUX. In conclusion, except for methanol, the inter-hydrogen exchange-correlation energy Vxc(H,H') makes the best contact with experiment, through 3J(H,H'), when multiplied with the internuclear distance RHH'.
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Affiliation(s)
- Ibon Alkorta
- Instituto
de Química Médica (CSIC), Juan de la Cierva, 3, Madrid 28006, Spain
| | - Paul L. A. Popelier
- Department
of Chemistry, University of Manchester, Manchester M13 9PL, U.K.,
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8
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Braddock DC, Duran-Corbera A, Nilforoushan M, Yang Z, He T, Santhakumar G, Bahou KA, Rzepa HS, Woscholski R, White AJP. (±)-Polysiphenol and Other Analogues via Symmetrical Intermolecular Dimerizations: A Synthetic, Spectroscopic, Structural, and Computational Study. JOURNAL OF NATURAL PRODUCTS 2022; 85:2650-2655. [PMID: 36288514 PMCID: PMC9706781 DOI: 10.1021/acs.jnatprod.2c00749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Indexed: 06/16/2023]
Abstract
We report an improved total synthesis of 4,5-dibromo-9,10-dihydrophenanthrene-2,3,6,7-tetraol, (±)-polysiphenol, via intermolecular McMurray dimerization of 5-bromovanillin and subsequent intramolecular oxidative coupling as the key steps. The synthetic route is applicable to 4,5-dichloro- and 4,5-difluoro-halologues (as well as a 4,5-dialkyl-analogue). Distinctive AA'BB' multiplets in their 1H NMR spectra for the dimethylene bridges of the dibromo and dichloro compounds reveal them to be room-temperature stable atropisomers, while for the difluoro compound they present as a singlet. X-ray crystal structure determinations of their tetramethylated synthetic precursors show atropisomeric twist angles of 48°, 46°, and 32°, respectively, with the former representing the largest yet observed in any 4,5-disubstituted-9,10-dihydrophenanthrene. DFT computational studies reveal an unprecedented two-stage atropisomeric interconversion process involving time-independent asynchronous rotations of the dimethylene bridge and the biaryl axis for halologues containing chlorine or bromine, but a more synchronous rotation for the difluoro analogue.
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9
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Sun M, Chen W, Zhang T, Liu Z, Wei J, Xi N. 19F NMR spectroscopy as a tool to detect rotations in fluorine substituted phenyl compounds. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.131679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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10
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Silva-Nigenda E, Martínez-Gómez A, Cruz-de la Cruz J, Barroso-Flores J, González-Romero C, Fuentes-Benites A, Jankowski CK, Cuevas-Yáñez E, Díaz-Torres E, Corona-Becerril D. Long range 1H19F coupling through multiple bond in thienopyridines, isoquinolines and 2-aza-carbazoles derivatives. J Mol Struct 2019. [DOI: 10.1016/j.molstruc.2018.08.084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Ligand-Tuneable, Red-Emitting Iridium(III) Complexes for Efficient Triplet-Triplet Annihilation Upconversion Performance. Chemistry 2018; 24:8577-8588. [DOI: 10.1002/chem.201801007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Indexed: 11/07/2022]
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12
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13
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Wang L, Huan G, Momen R, Azizi A, Xu T, Kirk SR, Filatov M, Jenkins S. QTAIM and Stress Tensor Characterization of Intramolecular Interactions Along Dynamics Trajectories of a Light-Driven Rotary Molecular Motor. J Phys Chem A 2017; 121:4778-4792. [PMID: 28586210 DOI: 10.1021/acs.jpca.7b02347] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A quantum theory of atoms in molecules (QTAIM) and stress tensor analysis was applied to analyze intramolecular interactions influencing the photoisomerization dynamics of a light-driven rotary molecular motor. For selected nonadiabatic molecular dynamics trajectories characterized by markedly different S1 state lifetimes, the electron densities were obtained using the ensemble density functional theory method. The analysis revealed that torsional motion of the molecular motor blades from the Franck-Condon point to the S1 energy minimum and the S1/S0 conical intersection is controlled by two factors: greater numbers of intramolecular bonds before the hop-time and unusually strongly coupled bonds between the atoms of the rotor and the stator blades. This results in the effective stalling of the progress along the torsional path for an extended period of time. This finding suggests a possibility of chemical tuning of the speed of photoisomerization of molecular motors and related molecular switches by reshaping their molecular backbones to decrease or increase the degree of coupling and numbers of intramolecular bond critical points as revealed by the QTAIM/stress tensor analysis of the electron density. Additionally, the stress tensor scalar and vector analysis was found to provide new methods to follow the trajectories, and from this, new insight was gained into the behavior of the S1 state in the vicinity of the conical intersection.
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Affiliation(s)
- Lingling Wang
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Guo Huan
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Roya Momen
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Alireza Azizi
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Tianlv Xu
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Steven R Kirk
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Michael Filatov
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
| | - Samantha Jenkins
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research and Key Laboratory of Resource Fine-Processing and Advanced Materials of Hunan Province of MOE, College of Chemistry and Chemical Engineering, Hunan Normal University , Changsha, Hunan 410081, China
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14
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Abraham RJ, Cooper MA. A re-investigation of 4JFF and 5JFF nuclear spin–spin couplings in substituted benzenes, a novel conformational tool. Phys Chem Chem Phys 2016; 18:15822-7. [DOI: 10.1039/c6cp01975g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The FF couplings in fluorobenzenes are separated into their σ and π components and this provides a novel method of determining the conformation of the C-1 substituent in 2,6-difluorobenzenes.
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Affiliation(s)
| | - M. Ashley Cooper
- Department of Chemistry
- The University of Liverpool
- Liverpool L69 7ZD
- UK
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15
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Electron localization-delocalization matrices in the prediction of pKa's and UV-wavelengths of maximum absorbance of p-benzoic acids and the definition of super-atoms in molecules. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.08.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Contreras RH, Llorente T, Ducati LC, Tormena CF. Revisiting NMR Through-Space JFF Spin–Spin Coupling Constants for Getting Insight into Proximate F---F Interactions. J Phys Chem A 2014; 118:5068-75. [DOI: 10.1021/jp501929t] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rubén H. Contreras
- Department
of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, C1053ABJ Buenos Aires, Argentina
| | - Tomás Llorente
- Department
of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, C1053ABJ Buenos Aires, Argentina
| | - Lucas Colucci Ducati
- Institute
of Chemistry, University of Sao Paulo − USP, P.O. Box 26077, 05513-970 Sao Paulo - SP, Brazil
| | - Cláudio Francisco Tormena
- Chemistry
Institute, University of Campinas - UNICAMP, P.O. Box 6154, 13083-970 Campinas - SP, Brazil
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17
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Matta* CF. Modeling biophysical and biological properties from the characteristics of the molecular electron density, electron localization and delocalization matrices, and the electrostatic potential. J Comput Chem 2014; 35:1165-98. [PMID: 24777743 PMCID: PMC4368384 DOI: 10.1002/jcc.23608] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Revised: 03/16/2014] [Accepted: 03/21/2014] [Indexed: 11/11/2022]
Abstract
The electron density and the electrostatic potential are fundamentally related to the molecular hamiltonian, and hence are the ultimate source of all properties in the ground- and excited-states. The advantages of using molecular descriptors derived from these fundamental scalar fields, both accessible from theory and from experiment, in the formulation of quantitative structure-to-activity and structure-to-property relationships, collectively abbreviated as QSAR, are discussed. A few such descriptors encode for a wide variety of properties including, for example, electronic transition energies, pK(a)'s, rates of ester hydrolysis, NMR chemical shifts, DNA dimers binding energies, π-stacking energies, toxicological indices, cytotoxicities, hepatotoxicities, carcinogenicities, partial molar volumes, partition coefficients (log P), hydrogen bond donor capacities, enzyme-substrate complementarities, bioisosterism, and regularities in the genetic code. Electronic fingerprinting from the topological analysis of the electron density is shown to be comparable and possibly superior to Hammett constants and can be used in conjunction with traditional bulk and liposolubility descriptors to accurately predict biological activities. A new class of descriptors obtained from the quantum theory of atoms in molecules' (QTAIM) localization and delocalization indices and bond properties, cast in matrix format, is shown to quantify transferability and molecular similarity meaningfully. Properties such as "interacting quantum atoms (IQA)" energies which are expressible into an interaction matrix of two body terms (and diagonal one body "self" terms, as IQA energies) can be used in the same manner. The proposed QSAR-type studies based on similarity distances derived from such matrix representatives of molecular structure necessitate extensive investigation before their utility is unequivocally established.
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Affiliation(s)
- Chérif F Matta*
- Department of Chemistry and Physics, Mount Saint Vincent UniversityHalifax, Nova Scotia, Canada, B3M 2J6
- Department of Chemistry, Dalhousie UniversityHalifax, Nova Scotia, Canada, B3H 4J3
- Department of Chemistry, Saint Mary's UniversityHalifax, Nova Scotia, Canada, B3H 3C3
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18
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Electron-density descriptors as predictors in quantitative structure--activity/property relationships and drug design. Future Med Chem 2011; 3:969-94. [PMID: 21707400 DOI: 10.4155/fmc.11.65] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The use of electron density-based molecular descriptors in drug research, particularly in quantitative structure--activity relationships/quantitative structure--property relationships studies, is reviewed. The exposition starts by a discussion of molecular similarity and transferability in terms of the underlying electron density, which leads to a qualitative introduction to the quantum theory of atoms in molecules (QTAIM). The starting point of QTAIM is the topological analysis of the molecular electron-density distributions to extract atomic and bond properties that characterize every atom and bond in the molecule. These atomic and bond properties have considerable potential as bases for the construction of robust quantitative structure--activity/property relationships models as shown by selected examples in this review. QTAIM is applicable to the electron density calculated from quantum-chemical calculations and/or that obtained from ultra-high resolution x-ray diffraction experiments followed by nonspherical refinement. Atomic and bond properties are introduced followed by examples of application of each of these two families of descriptors. The review ends with a study whereby the molecular electrostatic potential, uniquely determined by the density, is used in conjunction with atomic properties to elucidate the reasons for the biological similarity of bioisosteres.
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19
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Ampt KAM, Aspers RLEG, Jaeger M, Geutjes PETJ, Honing M, Wijmenga SS. Application of fluorine NMR for structure identification of steroids. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2011; 49:221-230. [PMID: 21387404 DOI: 10.1002/mrc.2737] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 01/13/2011] [Accepted: 01/14/2011] [Indexed: 05/30/2023]
Abstract
Fluorinated steroids were examined using 1D and 2D homo- and heteronuclear (19)F NMR, such as (19)F-(1) H and (19)F-(13)C. The utilization of fluorine NMR accounted for spectral simplification and resulted in a straightforward pathway for the determination of structures including the configuration of these compounds; these steroids present an illustrative example for other types of fluorinated compounds, which are increasingly encountered in drug discovery. The potential of (19)F NMR is elaborated on in detail for two compounds containing diastereotopic fluorines with different coupling patterns. The analysis of the coupling patterns and the through-space interactions resulted in the determination of the structure and configuration. Heteronuclear correlation experiments, i.e. (19)F-(1)H HETCOR, (19)F-(13)C HMQC and HMBC, and (19)F-(1)H HOESY, were applied to determine first the relative stereochemistry and then the molecular configuration at C4 and C5 of a steroidal compound bearing a fused three-membered ring with two fluorine substituents. These examples proved (19)F NMR to be a useful addition to the extensively used (1)H and (13)C NMR within structure elucidation and configuration determination of small molecules.
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Affiliation(s)
- Kirsten A M Ampt
- Institute of Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Ghiviriga I, Zhang L, Martinez H, Contreras RH, Tormena CF, Nodin L, Dolbier WR. 19F chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2011; 49:93-105. [PMID: 21246624 DOI: 10.1002/mrc.2713] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 11/15/2010] [Accepted: 11/19/2010] [Indexed: 05/30/2023]
Abstract
In the process of studying the chemistry of perfluoro[2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their (19)F-(19) F coupling patterns, and establishing a methodology for the assignment of their (19)F chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron-donor character and size. Quantum chemical calculations, performed at the HF/6-311 + G(d,p)//B3LYP/EPR-III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four- and five-bond (19)F-(19) F couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of (19)F chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products.
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Affiliation(s)
- Ion Ghiviriga
- Chemistry Department, University of Florida, Gainesville, 32611-7200, USA.
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Contreras RH, dos Santos FP, Ducati LC, Tormena CF. Difference between ²JC2H3 and ²JC3H2 spin-spin couplings in heterocyclic five- and six-membered rings as a probe for studying σ-ring currents: a quantum chemical analysis. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2010; 48 Suppl 1:S151-S158. [PMID: 21104760 DOI: 10.1002/mrc.2669] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Adequate analyses of canonical molecular orbitals (CMOs) can provide rather detailed information on the importance of different σ-Fermi contact (FC) coupling pathways (FC term transmitted through the σ-skeleton). Knowledge of the spatial distribution of CMOs is obtained by expanding them in terms of natural bond orbitals (NBOs). Their relative importance for transmitting the σ-FC contribution to a given spin-spin coupling constants (SSCCs) is estimated by resorting to the expression of the FC term given by the polarisation propagator formalism. In this way, it is possible to classify the effects affecting such couplings in two different ways: delocalisation interactions taking place in the neighbourhood of the coupling nuclei and 'round the ring' effects. The latter, associated with σ-ring currents, are observed to yield significant differences between the FC terms of (2)J(C2H3) and (2)J(C3H2) SSCCs which, consequently, are taken as probes to gauge the differences in σ-ring currents for the five-membered rings (furan, thiophene, selenophene and pyrrol) and also for the six-membered rings (benzene, pyridine, protonated pyridine and N-oxide pyridine) used in the present study.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, Buenos Aires, Argentina
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Contreras RH, Gotelli G, Ducati LC, Barbosa TM, Tormena CF. Analysis of Canonical Molecular Orbitals to Identify Fermi Contact Coupling Pathways. 1. Through-Space Transmission by Overlap of 31P Lone Pairs. J Phys Chem A 2009; 114:1044-51. [DOI: 10.1021/jp908970f] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rubén H. Contreras
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Gustavo Gotelli
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Lucas C. Ducati
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Thais M. Barbosa
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Cláudio F. Tormena
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
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Alkorta I, Elguero J, Limbach HH, Shenderovich IG, Winkler T. A DFT and AIM analysis of the spin-spin couplings across the hydrogen bond in the 2-fluorobenzamide and related compounds. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2009; 47:585-592. [PMID: 19378352 DOI: 10.1002/mrc.2433] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In 1975 a large number of coupling constants were measured in 2-fluorobenzamide labeled with (15)N. Some of them were assigned to couplings through intramolecular N-H...F hydrogen bonds (HBs). These couplings change dramatically when CDCl(3) is replaced by DMSO-d(6). In this theoretical paper we provide density functional theory (DFT) calculations that justify the existence of a weak HB in the absence of solvent, while solvents that act as HB acceptors break down the intramolecular hydrogen bond (IMHB) of 2-fluorobenzamide. Atoms in molecules (AIM) analyses and Steiner-Limbach plots were used to analyze the structure of the compounds.
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Affiliation(s)
- Ibon Alkorta
- Instituto de Química Médica, CSIC, Juan de la Cierva 3, E-28006 Madrid, Spain.
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Gauze GF, Basso EA, Contreras RH, Tormena CF. Effect of Sulfur Oxidation on the Transmission Mechanism of 4JHH NMR Coupling Constants in 1,3-Dithiane. J Phys Chem A 2009; 113:2647-51. [DOI: 10.1021/jp810981z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gisele F. Gauze
- Departamento de Química, Universidade Estadual de Maringá, CEP-87020-900, Maringá, PR, Brazil, Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina, and Department of Organic Chemistry, Chemistry Institute, P.O. Box 6154, University of Campinas, UNICAMP, CEP: 13084-971 Campinas, SP, Brazil
| | - Ernani A. Basso
- Departamento de Química, Universidade Estadual de Maringá, CEP-87020-900, Maringá, PR, Brazil, Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina, and Department of Organic Chemistry, Chemistry Institute, P.O. Box 6154, University of Campinas, UNICAMP, CEP: 13084-971 Campinas, SP, Brazil
| | - Rubén H. Contreras
- Departamento de Química, Universidade Estadual de Maringá, CEP-87020-900, Maringá, PR, Brazil, Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina, and Department of Organic Chemistry, Chemistry Institute, P.O. Box 6154, University of Campinas, UNICAMP, CEP: 13084-971 Campinas, SP, Brazil
| | - Cláudio F. Tormena
- Departamento de Química, Universidade Estadual de Maringá, CEP-87020-900, Maringá, PR, Brazil, Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina, and Department of Organic Chemistry, Chemistry Institute, P.O. Box 6154, University of Campinas, UNICAMP, CEP: 13084-971 Campinas, SP, Brazil
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Contreras RH, Provasi PF, dos Santos FP, Tormena CF. Stereochemical dependence of NMR geminal spin-spin coupling constants. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2009; 47:113-120. [PMID: 18991325 DOI: 10.1002/mrc.2359] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this work it was sought to explore the versatility of geminal spin-spin coupling constants, (2)J(XY) SSCCs, as probes for stereochemical studies. A set of compounds, where their experimental (2)J(XY) SSCCs through the X-C-Y molecular fragment are predicted to be sensitive to hyperconjugative interactions involving either bonding or antibonding orbitals containing the C carbon atom ('coupling pathway'), were analyzed. SSCC calculations were performed for some selected examples using the second order polarization propagator approximation (SOPPA) method or within the DFT-B3LYP framework. Hyperconjugative interactions were calculated within the Natural Bond Orbital (NBO) approach. Results are condensed in two qualitative rules: Rule I(M)-hyperconjugative interactions transferring charge into the coupling pathway yield a positive increase to the Fermi contact (FC), contribution to (2)K(XY) reduced spin-spin coupling constants (RSSCC), and Rule II(M)-hyperconjugative interactions transferring charge from the coupling pathway yield a negative increase to the FC contribution to (2)K(XY) RSSCC.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina
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Pérez C, Suardíaz R, Ortiz PJ, Crespo-Otero R, Bonetto GM, Gavín JA, García de la Vega JM, San Fabián J, Contreras RH. On the unusual 2J(C2-H(f)) coupling dependence on syn/anti CHO conformation in 5-X-furan-2-carboxaldehydes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:846-850. [PMID: 18566984 DOI: 10.1002/mrc.2268] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A remarkable difference for (2)J(C(2)-H(f)) coupling constant in syn and anti conformers of 5-X-furan-2-carboxaldehydes (X = CH(3), Ph, NO(2), Br) and a rationalization of this difference are reported. On the basis of the current knowledge of the Fermi-contact term transmission, a rather unusual dual-coupling pathway in the syn conformer is presented. The additional coupling pathway resembles somewhat that of the J(H-H) in homoallylic couplings, which are transmitted by hyperconjugative interactions involving the pi(C=C) electronic system. The homoallylic coupling pathway can be labeled as sigma*(C-H) <-- pi(C=C) --> sigma*(C-H). In the present case, this additional coupling pathway, using an analogous notation, can be labeled as sigma*(C(2)-C(C)) <-- LP(1)(O(1))...LP(2)(O(C)) --> sigma*(C(C)-H(f)) (sigma*(C(2)-C(C))) where O(1) and O(C) stand for the ring and carbonyl O atoms, respectively. This additional coupling pathway is not activated in the anti conformers since both oxygen lone pairs do not overlap.
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Affiliation(s)
- Carlos Pérez
- Departamento de Química Física, Facultad de Química, Universidad de La Habana, La Habana 10400, Cuba.
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Contreras RH, Suardíaz R, Pérez C, Crespo-Otero R, San Fabián J, García de la Vega JM. Karplus Equation for 3JHH Spin−Spin Couplings with Unusual 3J(180°) < 3J(0°) Relationship. J Chem Theory Comput 2008; 4:1494-500. [DOI: 10.1021/ct800145h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. H. Contreras
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R. Suardíaz
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - C. Pérez
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R. Crespo-Otero
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J. San Fabián
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J. M. García de la Vega
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Pedersoli S, Dos Santos FP, Rittner R, Contreras RH, Tormena CF. NMR spin-spin couplings involving nuclei in the neighborhood of a carbonyl group. 3JCH couplings in alpha-substituted acetamides. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:202-205. [PMID: 18181244 DOI: 10.1002/mrc.2158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In this work 3JCH spin-spin coupling constants (SSCCs) for the cis- and trans-conformers for alpha-X-acetamides (X = F, Cl, Br and CN) (1-4) were studied in detail since they were found to be notably different for both conformers. These differences are rationalized as originating in the changes of the strong negative hyperconjugative interactions that take place within the carbonyl group. Such changes are found to depend not only on conformation, but also on solvent. For the cis-conformers there is a close proximity between the X-substituent and the in-plane oxygen lone pair of pure p character, which affects notably their respective negative hyperconjugative interactions. Both the efficiency for transmitting the Fermi contact (FC) term through the coupling pathway of 3JCH SSCCs and its potential as a probe to study the stereochemical properties of the XH2C group are discussed.
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Affiliation(s)
- Susimaire Pedersoli
- Physical Organic Chemistry Laboratory, Chemistry Institute, Campinas State University, C.P. 6154, 13084-971, Campinas, SP, Brazil
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Krivdin LB, Khutsishvili SS, Shemyakina OA, Mal'kina AG, Trofimov BA, Contreras RH. Stereochemical study of iminodihydrofurans based on experimental measurements and SOPPA calculations of (13)C-(13)C spin-spin coupling constants. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2007; 45:758-65. [PMID: 17661430 DOI: 10.1002/mrc.2044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Configurational assignment and conformational analysis of a series of iminodihydrofurans obtained from cyanoacetylenic alcohols were performed on the basis of experimental measurements and high-level ab initio calculations of their (13)C-(13)C spin-spin coupling constants. The title compounds were shown to form and exist in solution as the individual Z isomers, adopting the orthogonal orientation of the amino, alkylamino and dialkylamino groups and the s-trans orientation of the CONH(2) group at the C(4) position of the 2,5-dihydro-2-iminofuran moiety.
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Affiliation(s)
- Leonid B Krivdin
- A. E. Favorsky Institute of Chemistry, Irkutsk, Siberian Branch of the Russian Academy of Sciences, Favorsky St. 1, 664033 Irkutsk, Russia.
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Matta CF, Bader RFW. An experimentalist's reply to "What is an atom in a molecule?". J Phys Chem A 2007; 110:6365-71. [PMID: 16686473 DOI: 10.1021/jp060761+] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Parr, Ayers and Nalewajski have opined in this Journal that the concept of an atom in a molecule "is an object knowable by the mind or intellect, not by the senses." This view is countered by the two hundred years of experimental chemistry underlying the realization that the properties of some total system are the sum of its atomic contributions. This paper concludes that an experimentalist has no doubt but that he or she is measuring the properties of atoms when performing an experiment.
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Affiliation(s)
- Chérif F Matta
- Department of Chemistry, Dalhousie University, Halifax NS B3H 4J3, Canada
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Contreras RH, Esteban AL, Díez E, Lochert IJ, Della EW, Tormena CF. Experimental and DFT studies on the transmission mechanisms of analogous NMR JCH and JCC couplings in 1-X- and 1-X-3-methylbicyclo[1.1.1]-pentanes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2007; 45:572-7. [PMID: 17534878 DOI: 10.1002/mrc.2009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The main aim of this work is to compare the transmission mechanisms for the Fermi contact term of spin-spin couplings, SSCCs, in series 1-X-bicyclo[1.1.1]-pentane, (1), and 1-X-3-methylbicyclo[1.1.1]pentane, (2), and from that comparison to gain insight into some subtle aspects of the FC transmission. To this end, 18 members of the latter series were isotopically enriched in (13)C at the methyl position and the following couplings were measured; 1JC3CMe, 3JC1CMe and 4JCXCMe. These three types of SSCCs in (2) are compared, respectively, with 1JC3H3, 3JC1H3 and 4JCXH in (1); these latter values were taken from previous works. Since electron delocalization plays an important role in the transmission of the FC interaction, the natural bond orbital (NBO) method is employed to quantify electron delocalization interactions within selected members of series (1) and (2). It is found that 1JC3H3 SSCCs in (1) is more efficiently transmitted than 1JC3CMe SSCCs in (2). On the other hand, 3JC1H3 and 4JCXH SSCCs in (1) are notably less efficiently transmitted than 3JC1CMe and 4JCXCMe SSCCs in (2), although substituent effects on these two SSCCs show the opposite trends. These different efficiencies are rationalized in terms of different sigma-hyperconjugative interactions in both series of compounds.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires, Ciudad Universitaria, Pabellón 1 (C1428EHA) Buenos Aires, Argentina
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Pakiari A, Eskandari K. Closed shell oxygen–oxygen bonding interaction based on electron density analysis. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2006.10.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Mandado M, Blockhuys F, Alsenoy CV. On the applicability of QTAIM, Hirshfeld and Mulliken delocalisation indices as a measure of proton spin–spin coupling in aromatic compounds. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.09.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Dorozhkin EI, Ignat'eva DV, Tamm NB, Goryunkov AA, Khavrel PA, Ioffe IN, Popov AA, Kuvychko IV, Streletskiy AV, Markov VY, Spandl J, Strauss SH, Boltalina OV. Synthesis, Characterization, and Theoretical Study of Stable Isomers of C70(CF3)n (n = 2, 4, 6, 8, 10). Chemistry 2006; 12:3876-89. [PMID: 16550623 DOI: 10.1002/chem.200501346] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Reaction of C70 with ten equivalents of silver(I) trifluoroacetate at 320-340 degrees C followed by fractional sublimation at 420-540 degrees C and HPLC processing led to the isolation of a single abundant isomer of C70(CF3)n for n = 2, 4, 6, and 10, and two abundant isomers of C70(CF3)8. These six compounds were characterized by using matrix-assisted laser desorption ionization (MALDI) mass spectrometry, 2D-COSY and/or 1D 19F NMR spectroscopy, and quantum-chemical calculations at the density functional theory (DFT) level. Some were also characterized by Raman spectroscopy. The addition patterns for the isolated compounds were unambiguously found to be C1-7,24-C70(CF3)2, C1-7,24,44,47-C70(CF3)4, C2-1,4,11,19,31,41-C70(CF3)6, Cs-1,4,11,19,31,41,51,64-C70(CF3)8, C2-1,4,11,19,31,41,51,60-C70(CF3)8, and C1-1,4,10,19,25,41,49,60,66,69-C70(CF3)10 (IUPAC numbering). Except for the last compound, which is identical to the recently reported, crystallographically characterized C70(CF3)10 derivative prepared by a different synthetic route, these compounds have not previously been shown to have the indicated addition patterns. The largest relative yield under an optimized set of reaction conditions was for the Cs isomer of C70(CF3)8 (ca. 30 mol % of the sublimed mixture of products based on HPLC integration). The results demonstrate that thermally stable C70(CF3)n isomers tend to have their CF3 groups arranged on isolated para-C6(CF3)2 hexagons and/or on a ribbon of edge-sharing meta- and/or para-C6(CF3)2 hexagons. For Cs- and C2-C70(CF3)8 and for C2-C70(CF3)6, the ribbons straddle the C70 equatorial belt; for C1-C70(CF3)4, the para-meta-para ribbon includes three polar hexagons; for C1-7,24-C70(CF3)2, the para-C6(CF3)2 hexagon includes one of the carbon atoms on a C70 polar pentagon. The 10.3-16.2 Hz 7JF,F NMR coupling constants for the end-of-ribbon CF3 groups, which are always para to their nearest-neighbor CF3 group, are consistent with through-space Fermi-contact interactions between the fluorine atoms of proximate, rapidly rotating CF3 groups.
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Kareev IE, Kuvychko IV, Lebedkin SF, Miller SM, Anderson OP, Strauss SH, Boltalina OV. Synthesis and structures of poly(perfluoroethyl)[60]fullerenes: 1,7,16,36,46,49-C60(C2F5)6and 1,6,11,18,24,27,32,35-C60(C2F5)8. Chem Commun (Camb) 2006:308-10. [PMID: 16391743 DOI: 10.1039/b513477c] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The high-temperature reaction of C60 and C2F5I produced poly(perfluoroethyl)fullerenes with unprecedented addition patterns.
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Affiliation(s)
- Ivan E Kareev
- Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432, Russia
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The first example of a cage critical point in a single ring: A novel twisted α-helical ring topology. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.04.088] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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