1
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Sunny AS, Cleven EC, Kumar P, Venkataramani S, Walls JD, Ramamurthy V. Structure, Dynamics, and Reactivity of Encapsulated Molecules in Restricted Spaces: Arylazoisoxazoles within an Octa Acid Capsule. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:17638-17655. [PMID: 39110852 DOI: 10.1021/acs.langmuir.4c01996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
In this study, a well-defined organic capsule assembled from two octa acid (OA) molecules acting as host and select arylazoisoxazoles (AAIO) acting as guests were employed to demonstrate that confined molecules have restricted freedom that translates into reaction selectivity in both ground and excited states. The behavior of these AAIO guests in confined capsules was found to be different from that found in both crystals, where there is very little freedom, and in isotropic solvents, where there is complete freedom. Through one-dimensional (1D) and two-dimensional (2D) 1H NMR spectroscopic experiments, we have established a relationship between structure, dynamics and reactivity of molecules confined in an OA capsule. Introduction of CF3 and CH3 substitution at the 4-position of the aryl group of AAIO reveals that in addition to space confinement, weak interactions between the guest and the OA capsule control the dynamics and reactivity of guest molecules. 1H NMR studies revealed that there is a temperature-dependence to guest molecules tumbling (180° rotation along the capsular short axis) within an OA capsule. While 1H NMR points to the occurrence of tumbling motion, MD simulations and simulation of the temperature-dependent NMR signals provide an insight into the mechanism of tumbling within OA capsules. Thermal and photochemical isomerization of AAIO were found to occur within an OA capsule just as in organic solvents. The observed selectivity noted during thermal and photo induced isomerization of OA encapsulated AAIOs can be qualitatively understood in terms of the well-known concepts due to Bell-Evans-Polanyi (BEP principle), Hammond and Zimmerman.
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Affiliation(s)
- Amal Sam Sunny
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Elliott C Cleven
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Pravesh Kumar
- Department of Chemical Sciences, Indian Institute of Science Education and Research, Mohali, Sector 81, Knowledge City, Manauli 140306, Punjab, India
| | - Sugumar Venkataramani
- Department of Chemical Sciences, Indian Institute of Science Education and Research, Mohali, Sector 81, Knowledge City, Manauli 140306, Punjab, India
| | - Jamie D Walls
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
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2
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Khadka D, Jayasinghe-Arachchige VM, Prabhakar R, Ramamurthy V. Application of molecular dynamic simulations in modeling the excited state behavior of confined molecules. Photochem Photobiol Sci 2023:10.1007/s43630-023-00486-2. [PMID: 37843722 DOI: 10.1007/s43630-023-00486-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/20/2023] [Indexed: 10/17/2023]
Abstract
Relative to isotropic organic solvent medium, the structure and conformation of a reactant molecule in an organized and confining medium are often different. In addition, because of the rigidity of the immediate environment, the reacting molecule have a little freedom to undergo large changes even upon gaining energy or modifications in the electronic structure. These alterations give rise to differences in the photochemistry of a molecular and supramolecular species. In this study, one such example is presented. α-Alkyl dibenzylketones upon excitation in isotropic solvents give products via Norrish type I and type II reactions that are independent of the chain length of the alkyl substituent. On the other hand, when these molecules are enclosed within an organic capsule of volume ~ 550 Å3, they give products that are strikingly dependent on the length of the α-alkyl substitution. These previously reported experimental observations are rationalized based on the structures generated by molecular modeling (docking and molecular dynamics (MD) simulations). It is shown that MD simulations that are utilized extensively in biologically important macromolecules can also be useful to understand the excited state behavior of reactive molecules that are part of supramolecular assemblies. These simulations can provide structural information of the reactant molecule and the surroundings complementing that with the one obtained from 1 and 2D NMR experiments. MD simulated structures of seven α-alkyl dibenzylketones encapsulated within the octa acid capsule provide a clear understanding of their unique behavior in this restricted medium. Because of the rigidity of the medium, these structures although generated in the ground state can rationalize the photochemical behavior of the molecules in the excited state.
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Affiliation(s)
- Dipendra Khadka
- Department of Chemistry, University of Miami, Coral Gables, FL, 33124, USA
| | | | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, Coral Gables, FL, 33124, USA.
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3
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Khadka D, Kulasekharan R, Ramamurthy V. Role of Supramolecular Steric Compression During Photoinduced Intramolecular Hydrogen Abstraction Reactions of Ketones and Thioketones. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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4
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Montà-González G, Sancenón F, Martínez-Máñez R, Martí-Centelles V. Purely Covalent Molecular Cages and Containers for Guest Encapsulation. Chem Rev 2022; 122:13636-13708. [PMID: 35867555 PMCID: PMC9413269 DOI: 10.1021/acs.chemrev.2c00198] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cage compounds offer unique binding pockets similar to enzyme-binding sites, which can be customized in terms of size, shape, and functional groups to point toward the cavity and many other parameters. Different synthetic strategies have been developed to create a toolkit of methods that allow preparing tailor-made organic cages for a number of distinct applications, such as gas separation, molecular recognition, molecular encapsulation, hosts for catalysis, etc. These examples show the versatility and high selectivity that can be achieved using cages, which is impossible by employing other molecular systems. This review explores the progress made in the field of fully organic molecular cages and containers by focusing on the properties of the cavity and their application to encapsulate guests.
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Affiliation(s)
- Giovanni Montà-González
- Instituto
Interuniversitario de Investigación de Reconocimiento Molecular
y Desarrollo Tecnológico (IDM) Universitat
Politècnica de València, Universitat de València. Camino de Vera, s/n 46022, Valencia, Spain
| | - Félix Sancenón
- Instituto
Interuniversitario de Investigación de Reconocimiento Molecular
y Desarrollo Tecnológico (IDM) Universitat
Politècnica de València, Universitat de València. Camino de Vera, s/n 46022, Valencia, Spain,CIBER
de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, 28029 Madrid, Spain,Centro
de Investigación Príncipe Felipe, Unidad Mixta UPV-CIPF
de Investigación de Mecanismos de Enfermedades y Nanomedicina,
Valencia, Universitat Politècnica
de València, 46012 Valencia, Spain,Instituto
de Investigación Sanitaria la Fe, Unidad Mixta de Investigación
en Nanomedicina y Sensores, Universitat
Politènica de València, 46026 València, Spain,Departamento
de Química, Universitat Politècnica
de València, 46022 Valencia, Spain
| | - Ramón Martínez-Máñez
- Instituto
Interuniversitario de Investigación de Reconocimiento Molecular
y Desarrollo Tecnológico (IDM) Universitat
Politècnica de València, Universitat de València. Camino de Vera, s/n 46022, Valencia, Spain,CIBER
de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, 28029 Madrid, Spain,Centro
de Investigación Príncipe Felipe, Unidad Mixta UPV-CIPF
de Investigación de Mecanismos de Enfermedades y Nanomedicina,
Valencia, Universitat Politècnica
de València, 46012 Valencia, Spain,Instituto
de Investigación Sanitaria la Fe, Unidad Mixta de Investigación
en Nanomedicina y Sensores, Universitat
Politènica de València, 46026 València, Spain,Departamento
de Química, Universitat Politècnica
de València, 46022 Valencia, Spain,R.M.-M.: email,
| | - Vicente Martí-Centelles
- Instituto
Interuniversitario de Investigación de Reconocimiento Molecular
y Desarrollo Tecnológico (IDM) Universitat
Politècnica de València, Universitat de València. Camino de Vera, s/n 46022, Valencia, Spain,V.M.-C.:
email,
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5
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Pradeep A, Varadharajan R, Ramamurthy V. Reversible Photoisomerization of Norbornadiene-Quadricyclane within a Confined Capsule. Photochem Photobiol 2022; 99:624-636. [PMID: 35977794 DOI: 10.1111/php.13692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 08/14/2022] [Indexed: 11/30/2022]
Abstract
With the desire to develop a sustainable green method to store and release solar energy via a chemical reaction we have examined the well investigated norbornadiene-quadricyclane (NBD-QC) system in water. In this context, we have employed octa acid (OA) as the host that forms a capsule in water. According to 1 H NMR spectra and diffusion constants OA forms a stable 2:2 complex with both NBD and QC and 1:1:2 mixed complex in presence of equal amounts of both NBD and QC. The photoconversion of NBD to QC within the OA capsule is clean without side reactions. In this case OA itself acts as a triplet sensitizer. Recognizing the disadvantage of this supramolecular approach, in the future we plan to look for visible light absorbing sensitizers to perform this conversion. The reverse reaction (QC to NBD) is achieved via electron transfer process with methylene blue as the sensitizer. This reverse reaction is also clean and no side products were detected. The preliminary results reported here provides 'proof of principle' for combining green, sustainable and supramolecular chemistries in the context of solar energy capture and release.
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Affiliation(s)
- Anu Pradeep
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Ramkumar Varadharajan
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - V Ramamurthy
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
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6
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Ramamurthy V, Sen P, Elles CG. Ultrafast Excited State Dynamics of Spatially Confined Organic Molecules. J Phys Chem A 2022; 126:4681-4699. [PMID: 35786917 DOI: 10.1021/acs.jpca.2c03276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This Feature Article highlights the role of spatial confinement in controlling the fundamental behavior of molecules. Select examples illustrate the value of using space as a tool to control and understand excited-state dynamics through a combination of ultrafast spectroscopy and conventional steady-state methods. Molecules of interest were confined within a closed molecular capsule, derived from a cavitand known as octa acid (OA), whose internal void space is sufficient to accommodate molecules as long as tetracene and as wide as pyrene. The free space, i.e., the space that is left following the occupation of the guest within the host, is shown to play a significant role in altering the behavior of guest molecules in the excited state. The results reported here suggest that in addition to weak interactions that are commonly emphasized in supramolecular chemistry, the extent of empty space (i.e., the remaining void space within the capsule) is important in controlling the excited-state behavior of confined molecules on ultrafast time scales. For example, the role of free space in controlling the excited-state dynamics of guest molecules is highlighted by probing the cis-trans isomerization of stilbenes and azobenzenes within the OA capsule. Isomerization of both types of molecule are slowed when they are confined within a small space, with encapsulated azobenzenes taking a different reaction pathway compared to that in solution upon excitation to S2. In addition to steric constraints, confinement of reactive molecules in a small space helps to override the need for diffusion to bring the reactants together, thus enabling the measurement of processes that occur faster than the time scale for diffusion. The advantages of reducing free space and confining reactive molecules are illustrated by recording unprecedented excimer emission from anthracene and by measuring ultrafast electron transfer rates across the organic molecular wall. By monitoring the translational motion of anthracene pairs in a restricted space, it has been possible to document the pathway undertaken by excited anthracene from inception to the formation of the excimer on the excited-state surface. Similarly, ultrafast electron transfer experiments pursued here have established that the process is not hindered by a molecular wall. Apparently, the electron can cross the OA capsule wall provided the donor and acceptor are in close proximity. Measurements on the ultrafast time scale provide crucial insights for each of the examples presented here, emphasizing the value of both "space" and "time" in controlling and understanding the dynamics of excited molecules.
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Affiliation(s)
| | - Pratik Sen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, UP 208 016, India
| | - Christopher G Elles
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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7
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Varadharajan R, Kelley SA, Jayasinghe-Arachchige VM, Prabhakar R, Ramamurthy V, Blackstock SC. Organic Host Encapsulation Effects on Nitrosobenzene Monomer-Dimer Distribution and C-NO Bond Rotation in an Aqueous Solution. ACS ORGANIC & INORGANIC AU 2021; 2:175-185. [PMID: 36855459 PMCID: PMC9954408 DOI: 10.1021/acsorginorgau.1c00043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The intermolecular (monomer-dimer equilibrium) and intramolecular (C-NO and C-NMe2 rotations) dynamics of 4-nitrosocumene (1a) and 4-(N,N-dimethylamino)nitrosobenzene (1b), respectively, were found to be controlled by the medium (water) and the host environment (organic capsules and cavitands). The ability of water to shift the equilibrium toward the dimer appears to result from dipolar stabilization of the polar dimer structure and has a resemblance to water's known ability to favor organic cycloaddition reactions. In an aqueous medium, a range of organic hosts selectively include only the nitrosocumene monomer 1a. Encapsulation in the octa acid duplex (OA2) selects two 1a monomers rather than a dimer structure. Octa acid encapsulation also results in more restricted intramolecular C-N rotations of the guest 1b.
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Affiliation(s)
- Ramkumar Varadharajan
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33146, United States
| | - Sarah Ariel Kelley
- Department
of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336, United States
| | | | - Rajeev Prabhakar
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33146, United States
| | - Vaidhyanathan Ramamurthy
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33146, United States,
| | - Silas C. Blackstock
- Department
of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama 35487-0336, United States,
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Yao W, Wang K, Ismaiel YA, Wang R, Cai X, Teeler M, Gibb BC. Electrostatic Potential Field Effects on Amine Macrocyclizations within Yoctoliter Spaces: Supramolecular Electron Withdrawing/Donating Groups. J Phys Chem B 2021; 125:9333-9340. [PMID: 34355901 PMCID: PMC8383300 DOI: 10.1021/acs.jpcb.1c05238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The
central role of Coulombic interactions in enzyme catalysis
has inspired multiple approaches to sculpting electrostatic potential
fields (EPFs) for controlling chemical reactivity, including ion gradients
in water microdroplets, the tips of STMs, and precisely engineered
crystals. These are powerful tools because EPFs can affect all reactions,
even those whose mechanisms do not involve formal charges. For some
time now, supramolecular chemists have become increasingly proficient
in using encapsulation to control stoichiometric and catalytic reactions.
However, the field has not taken advantage of the broad range of nanocontainers
available to systematically explore how EPFs can affect reactions
within their inner-spaces. With that idea in mind, previously, we
reported on how positively and negatively charged supramolecular capsules
can modulate the acidity and reactivity of thiol guests bound within
their inner, yoctoliter spaces (Cai, X.; Kataria, R.; Gibb, B. C. J. Am. Chem. Soc. 2020, 142, 8291–8298; Wang, K.; Cai, X.; Yao, W.; Tang, D.; Kataria,
R.; Ashbaugh, H. S.; Byers, L. D.; Gibb, B. C. J. Am. Chem.
Soc.2019, 141, 6740–6747).
Building on this, we report here on the cyclization of 14-bromotetradecan-1-amine
inside these yoctoliter containers. We examine the rate and activation
thermodynamics of cyclization (Eyring analysis), both in the absence
and presence of exogenous salts whose complementary ion can bind to
the outside of the capsule and hence attenuate its EPF. We find the
cyclization rates and activation thermodynamics in the two capsules
to be similar, but that for either capsule attenuation of the EPF
slows the reaction down considerably. We conclude the capsules behave
in a manner akin to covalently attached electron donating/withdrawing
groups in a substrate, with each capsule enforcing their own deviations
from the idealized SN2 mechanism by moving electron density
and charge in the activated complex and TS, and that the idealized
SN2 mechanism inside the theoretical neutral host is relatively
difficult because of the lack of solvation of the TS.
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Affiliation(s)
- Wei Yao
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Kaiyu Wang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Yahya A Ismaiel
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Ruiqing Wang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Xiaoyang Cai
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Mary Teeler
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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9
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Alagbe BD, Gibb BC, Ashbaugh HS. Evolution of the Free Energy Landscapes of n-Alkane Guests Bound within Supramolecular Complexes. J Phys Chem B 2021; 125:7299-7310. [PMID: 34170690 PMCID: PMC8279555 DOI: 10.1021/acs.jpcb.1c03640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Confinement within nanoscale spaces can dramatically alter the ensemble of conformations flexible species explore. For example, chaperone complexes take advantage of confinement to fold misfolded proteins, while viral capsids transport genomic materials in tight packings. Here we examine the free energy landscapes of n-alkanes confined within supramolecular dimeric complexes of deep-cavity cavitand octa-acid, which have been experimentally demonstrated to force these chains with increasing length to adopt extended, helical, hairpin, and spinning top conformational motifs, using molecular simulations. Alkanes up to n-docosane in both vacuum and water predominantly exhibit a free energy minimum for elongated conformations with a majority of trans dihedrals. Within harmonically sealed cavitand dimers, however, the free energy landscapes as a function of the end-to-end distance between their terminal methyl units exhibit minima that evolve with the length of the alkane. Distinct free energy basins are observed between the helical and hairpin motifs and between the hairpin and chicane motifs whose relative stability changes with the number of carbons in the bound guest. These changes are reminiscent of two state-like protein folding, although the observed alkane conformations confined are more insensitive to temperature perturbation than proteins are. While the chicane motif within the harmonically sealed dimers has not been observed experimentally, this conformation relaxes to the observed spinning top motif once the harmonic restraints are released for the complexes in aqueous solution, indicating that these motifs are related to one another. We do not observe distinct minima between the confined extended and helical motifs, suggesting these conformers are part of a larger linear motif family whose population of gauche dihedral angles grows in proportion to the number of carbons in the chain to ultimately form a helix that fits the alkane within the complex.
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Affiliation(s)
- Busayo D Alagbe
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
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10
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Sunny AS, Ramamurthy V. An Organic Capsule as a Matrix to Capture and Store Reactive Molecules at Room Temperature in Aqueous Solution: 7-cis-β-Ionone †. Photochem Photobiol 2021; 97:1365-1375. [PMID: 34146419 DOI: 10.1111/php.13473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/16/2021] [Accepted: 06/17/2021] [Indexed: 11/28/2022]
Abstract
Low-temperature m atrix isolation method is the most popular one to generate and store reactive molecules and characterize them by in situ IR spectroscopy. Recognizing the need for a simpler method to trap and store such molecules and characterize by NMR spectroscopy at room temperature in solution, we have performed experiments exploring the value of water-soluble octa acid (OA) capsule as a storage vessel. The molecule we have chosen to illustrate the feasibility is the highly hindered 7-cis-β-ionone, which has been established to exist in equilibrium with its cyclic form with the later favored at room temperature. In this study, we have shown that confined space can be an alternative to temperature to tilt an equilibrium toward higher energy isomer. During the course of the study, we were surprised to note that 7-trans-β-ionone aggregates in water and has distinct 1 H NMR spectra. Ability to assemble characterizable organic aggregates in water reveals the value of water as a reaction medium that is yet to be fully explored by photochemists. Finally, we have clarified the likely mechanism of secondary photoreaction of α-pyran to the final photoproduct that involves 1,5-hydrogen migration.
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Affiliation(s)
- Amal Sam Sunny
- Department of Chemistry, University of Miami, Coral Gables, FL
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11
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Harada K, Sekiya R, Haino T. Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside a Size-Regulable Hemicarcerand. J Org Chem 2021; 86:4440-4447. [PMID: 33541083 DOI: 10.1021/acs.joc.0c02833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
A resorcinarene-based hemicarcerand, which consists of two cavitands covalently linked to each other by four alkyl chains, allows structural expansion and contraction by demetalation and metalation of Cu(I) cations with a size change of approximately 12 Å. This metal-mediated switching of the two states regulates the conformations of acetoxy group-terminated alkyl chains. A guest binding study reveals the encapsulation of heptyl to undecyl chains in metal-free and Cu(I)-coordinated capsules. The chemical shifts of the acetoxy groups of the bound guests are the same in the metal-free capsule, while those in the Cu(I)-coordinated one differ from each other. This indicates that the metal-free capsule regulates its size to the bound guests, while the bound guests adopt their conformations to the cavity of the Cu(I)-coordinated capsules. 1H NMR measurements and molecular mechanics calculations suggest that the bound guests have extended conformations in the metal-free capsule, while the Cu(I)-coordinated capsule forces the bound guests to adopt folded conformations. The presence of folded conformations is supported by the conformational study with structurally similar capsules and a nonsymmetric guest, allowing us to observe nuclear Overhauser effects stemming from the folded conformations of the guest in the cavity.
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Affiliation(s)
- Kentaro Harada
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Ryo Sekiya
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Takeharu Haino
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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12
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Das A, Danao A, Banerjee S, Raj AM, Sharma G, Prabhakar R, Srinivasan V, Ramamurthy V, Sen P. Dynamics of Anthracene Excimer Formation within a Water-Soluble Nanocavity at Room Temperature. J Am Chem Soc 2021; 143:2025-2036. [PMID: 33471537 DOI: 10.1021/jacs.0c12169] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Excited anthracene is well-known to photodimerize and not to exhibit excimer emission in isotropic organic solvents. Anthracene (AN) forms two types of supramolecular host-guest complexes (2:1 and 2:2, H:G) with the synthetic host octa acid in aqueous medium. Excitation of the 2:2 complex results in intense excimer emission, as reported previously, while the 2:1 complex, as expected, yields only monomer emission. This study includes confirming of host-guest complexation by NMR, probing the host-guest structure by molecular dynamics simulation, following the dynamics AN molecules in the excited state by ultrafast time-resolved experiments, and mapping of the excited surface through quantum chemical calculations (QM/MM-TDDFT method). Importantly, time-resolved emission experiments revealed the excimer emission maximum to be time dependent. This observation is unique and is not in line with the textbook examples of time-independent monomer-excimer emission maxima of aromatics in solution. The presence of at least one intermediate between the monomer and the excimer is inferred from time-resolved area normalized emission spectra. Potential energy curves calculated for the ground and excited states of two adjacent anthracene molecules via the QM/MM-TDDFT method support the model proposed on the basis of time-resolved experiments. The results presented here on the excited-state behavior of a well-investigated aromatic molecule, namely the parent anthracene, establish that the behavior of a molecule drastically changes under confinement. The results presented here have implications on the behavior of molecules in biological systems.
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Affiliation(s)
- Aritra Das
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208 016, India
| | - Ashwini Danao
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Shubhojit Banerjee
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh 462 066, India
| | - A Mohan Raj
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Gaurav Sharma
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Varadharajan Srinivasan
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh 462 066, India
| | - V Ramamurthy
- Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Pratik Sen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208 016, India
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13
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Escobar L, Ballester P. Molecular Recognition in Water Using Macrocyclic Synthetic Receptors. Chem Rev 2021; 121:2445-2514. [PMID: 33472000 DOI: 10.1021/acs.chemrev.0c00522] [Citation(s) in RCA: 123] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Molecular recognition in water using macrocyclic synthetic receptors constitutes a vibrant and timely research area of supramolecular chemistry. Pioneering examples on the topic date back to the 1980s. The investigated model systems and the results derived from them are key for furthering our understanding of the remarkable properties exhibited by proteins: high binding affinity, superior binding selectivity, and extreme catalytic performance. Dissecting the different effects contributing to the proteins' properties is severely limited owing to its complex nature. Molecular recognition in water is also involved in other appreciated areas such as self-assembly, drug discovery, and supramolecular catalysis. The development of all these research areas entails a deep understanding of the molecular recognition events occurring in aqueous media. In this review, we cover the past three decades of molecular recognition studies of neutral and charged, polar and nonpolar organic substrates and ions using selected artificial receptors soluble in water. We briefly discuss the intermolecular forces involved in the reversible binding of the substrates, as well as the hydrophobic and Hofmeister effects operating in aqueous solution. We examine, from an interdisciplinary perspective, the design and development of effective water-soluble synthetic receptors based on cyclic, oligo-cyclic, and concave-shaped architectures. We also include selected examples of self-assembled water-soluble synthetic receptors. The catalytic performance of some of the presented receptors is also described. The latter process also deals with molecular recognition and energetic stabilization, but instead of binding ground-state species, the targets become elusive counterparts: transition states and other high-energy intermediates.
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Affiliation(s)
- Luis Escobar
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain.,Departament de Química Analítica i Química Orgánica, Universitat Rovira i Virgili, c/Marcel·lí Domingo 1, 43007 Tarragona, Spain
| | - Pablo Ballester
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Av. Països Catalans 16, 43007 Tarragona, Spain.,ICREA, Passeig Lluís Companys 23, 08010 Barcelona, Spain
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14
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Varadharajan R, Raj AM, Ramamurthy V. Remote electron and energy transfer sensitized photoisomerization of encapsulated stilbenes. Photochem Photobiol Sci 2020; 19:976-986. [PMID: 32582889 DOI: 10.1039/d0pp00115e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Excited state chemistry and physics of molecules, in addition to their inherent electronic and steric features, depend on their immediate microenvironments. This study explores the influence of an organic capsule, slightly larger than the reactant molecule itself, on the excited state chemistry of the encapsulated molecule. Results presented here show that the confined molecule, in fact, is not isolated and can be manipulated from outside even without direct physical interaction. Examples where communication between a confined molecule and a free molecule present outside is brought about through electronic and energy transfer processes are presented. Geometric isomerization of octa acid encapsulated stilbenes induced by energy and electron transfer by cationic sensitizers that attach themselves to the anionic capsule is examined. The fact that isomerization occurs when the sensitizer present outside is excited illustrates that the reactant and sensitizer are communicating across the molecular wall of the capsule. Ability to remotely activate a confined molecule opens up new opportunities to bring about reactions of confined radical ions and triplet excited molecules generated via long distance energy and electron transfer processes.
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Affiliation(s)
| | - A Mohan Raj
- Department of Chemistry, University of Miami, 33146, Coral GablesMiami, FL, USA
| | - V Ramamurthy
- Department of Chemistry, University of Miami, 33146, Coral GablesMiami, FL, USA.
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15
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Samanta S, Baldridge A, Tolbert LM, Ramamurthy V. Guest/Host Complexes of Octa Acid and Amphiphilic Benzylidene-3-methylimidazolidinones Exchange Hosts within the NMR Time Scale. ACS OMEGA 2020; 5:8230-8241. [PMID: 32309733 PMCID: PMC7161058 DOI: 10.1021/acsomega.0c00523] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 03/19/2020] [Indexed: 06/11/2023]
Abstract
Cavitand octa acid (OA) is established to form a stable capsular assembly with one or two hydrophobic guest molecules (1:2 or 2:2 guest/host complex). Examples are known in which the guest molecule tumbles within the capsule without disrupting the structure of the capsuleplex. This process makes the two OA molecules that form the capsule magnetically equivalent. In this study, we have examined the dynamics of capsules that host amphiphilic benzylidene-3-methylimidazolidinone molecules as guests. In these capsuleplexes, although the guest does not tumble, the two OA molecules become magnetically equivalent because the two OA molecules that form the capsule exchange their positions in the NMR time scale. This is equivalent to the content of the capsule remaining stationary while the capsule swirls around it. Benzylidene-3-methylimidazolidinones form both 1:1 and 1:2 supramolecular complexes with cavitand OA. Two-dimensional NMR, ROESY, and NOESY data suggest that in a 300 ms time scale, the two halves of the capsule exchange between themselves and with free OA. The conclusion drawn here provides valuable information concerning the stability of the OA capsuleplex and cavitandplex that is used as the well-defined space to control the excited-state chemistry and dynamics of confined guest molecules.
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Affiliation(s)
- Shampa
R. Samanta
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33146, United States
| | - Anthony Baldridge
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United
States
| | - Laren M. Tolbert
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United
States
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16
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Mohan Raj A, Sharma G, Prabhakar R, Ramamurthy V. Room-Temperature Phosphorescence from Encapsulated Pyrene Induced by Xenon. J Phys Chem A 2019; 123:9123-9131. [PMID: 31542924 DOI: 10.1021/acs.jpca.9b08354] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphorescence from pyrene especially at room temperature is uncommon. This emission was recorded utilizing a supramolecular organic host and the effect due to the heavy atom. Poor intersystem crossing from S1 to T1, small radiative rate constant from T1, and large rate constant for oxygen quenching hinder the phosphorescence of aromatic molecules at room temperature in solution. In this study, these limitations are overcome by encapsulating a pyrene molecule within a water-soluble capsule (octa acid, OA) and purging with xenon. While OA suppressed oxygen quenching, xenon enabled the intersystem crossing from S1 to T1 and radiative process from T1 to S0 through the well-known heavy atom effect. The close interaction facilitated between the pyrene and the heavy atom perturber xenon in the three-component supramolecular assembly (OA, pyrene, and xenon) resulted in phosphorescence from pyrene. Computational modeling and NMR studies supported the postulate that pyrene and more than one molecule of xenon are present within a confined space of the OA capsule.
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Affiliation(s)
- A Mohan Raj
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Gaurav Sharma
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Rajeev Prabhakar
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - V Ramamurthy
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
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17
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Kamatham N, Raj AM, Givens RS, Da Silva JP, Ramamurthy V. Supramolecular photochemistry of encapsulated caged ortho-nitrobenzyl triggers. Photochem Photobiol Sci 2019; 18:2411-2420. [PMID: 31347647 DOI: 10.1039/c9pp00260j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
ortho-Nitrobenzyl (oNB) triggers have been extensively used to release various molecules of interest. However, the toxicity and reactivity of the spent chromophore, o-nitrosobenzaldehyde, remains an unaddressed difficulty. In this study we have applied the well-established supramolecular photochemical concepts to retain the spent trigger o-nitrosobenzaldehyde within the organic capsule after release of water-soluble acids and alcohols. The sequestering power of organic capsules for spent chromophores during photorelease from ortho-nitrobenzyl esters, ethers and alcohols is demonstrated with several examples.
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18
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Wei X, Raj AM, Ji J, Wu W, Veerakanellore GB, Yang C, Ramamurthy V. Reversal of Regioselectivity during Photodimerization of 2-Anthracenecarboxylic Acid in a Water-Soluble Organic Cavitand. Org Lett 2019; 21:7868-7872. [DOI: 10.1021/acs.orglett.9b02860] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xueqin Wei
- School of Pharmacy, Guangxi Medical University, Nanning 530021, China
- Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, State Key Laboratory of Biotherapy, and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610064, China
| | - A. Mohan Raj
- Department of Chemistry, University of Miami, Coral Cables, Florida 33124, , United States
| | - Jiecheng Ji
- Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, State Key Laboratory of Biotherapy, and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610064, China
| | - Wanhua Wu
- Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, State Key Laboratory of Biotherapy, and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610064, China
| | | | - Cheng Yang
- Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, State Key Laboratory of Biotherapy, and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610064, China
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19
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Das A, Sharma G, Kamatham N, Prabhakar R, Sen P, Ramamurthy V. Ultrafast Solvation Dynamics Reveal that Octa Acid Capsule's Interior Dryness Depends on the Guest. J Phys Chem A 2019; 123:5928-5936. [PMID: 31276410 DOI: 10.1021/acs.jpca.9b04626] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Coumarins are well-known to exhibit environment-dependent excited-state behavior. We have exploited this feature to probe the accessibility of solvent water molecules to coumarins (guest) encapsulated within an organic capsule (host). Two sets of coumarins, one small that fits well within the capsule and the other larger that fits within an enlarged capsule, are used as guests. In our study, the two sets of coumarins serve different purposes: one is employed to explore electron transfer across the capsule and the other to release photoprotected acids into the aqueous environment. The capsule is made up of two molecules of octa acid (OA) and is soluble in an aqueous medium under slightly basic conditions. Molecular modeling studies revealed that while the OA capsule is fully closed with no access to water in the case of smaller coumarins, with the larger molecules, the capsule is not tight and the guest is in contact with water molecules, the number being dependent on the size of the coumarin. We have used the ultrafast time-dependent Stokes shift method to understand the solvent dynamics around the above guest molecules encapsulated within an OA capsule in an aqueous medium. Results depict that for the smaller sets of coumarins, water cannot access the guests within the OA cavity during their excited state lifetime. However, the case is completely different for the larger coumaryl esters. Distorted capsule structure exposes the guest to water, and a dynamics Stokes shift is observed. The average solvation time decreases with the increasing size of guests that clearly indicates accessibility of the encapsulated guests toward greater number of water molecules as the capsule structure distorts with increasing size of the guests. Results of the ultrafast solvation dynamics are consistent with that of molecular dynamics simulation.
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Affiliation(s)
- Aritra Das
- Department of Chemistry , Indian Institute of Technology Kanpur , Kanpur 208016 , India
| | - Gaurav Sharma
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Nareshbabu Kamatham
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Rajeev Prabhakar
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Pratik Sen
- Department of Chemistry , Indian Institute of Technology Kanpur , Kanpur 208016 , India
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20
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Otolski CJ, Mohan Raj A, Sharma G, Prabhakar R, Ramamurthy V, Elles CG. Ultrafast trans → cis Photoisomerization Dynamics of Alkyl-Substituted Stilbenes in a Supramolecular Capsule. J Phys Chem A 2019; 123:5061-5071. [PMID: 31140802 DOI: 10.1021/acs.jpca.9b03285] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ultrafast spectroscopy reveals the effects of confinement on the excited-state photoisomerization dynamics for a series of alkyl-substituted trans-stilbenes encapsulated in the hydrophobic cavity of an aqueous supramolecular organic host-guest complex. Compared with the solvated compounds, encapsulated trans-stilbenes have broader excited-state absorption spectra, excited-state lifetimes that are 3-4 times longer, and photoisomerization quantum yields that are 1.7-6.5 times lower in the restricted environment. The organic capsule disrupts the equilibrium structure and restricts torsional rotation around the central C═C double bond in the excited state, which is an important motion for the relaxation of trans-stilbene from S1 to S0. The location and identity of alkyl substituents play a significant role in determining the excited-state dynamics and photoisomerization quantum yields by tuning the relative crowding inside the capsule. The results are discussed in terms of distortions of the ground- and excited-state potential energy surfaces, including the topology of the S1-S0 conical intersection.
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Affiliation(s)
- Christopher J Otolski
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
| | - A Mohan Raj
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Gaurav Sharma
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | - Rajeev Prabhakar
- Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States
| | | | - Christopher G Elles
- Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States
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21
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Wang K, Cai X, Yao W, Tang D, Kataria R, Ashbaugh HS, Byers LD, Gibb BC. Electrostatic Control of Macrocyclization Reactions within Nanospaces. J Am Chem Soc 2019; 141:6740-6747. [DOI: 10.1021/jacs.9b02287] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Kaiya Wang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Xiaoyang Cai
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Wei Yao
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Du Tang
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Rhea Kataria
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Henry S. Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Larry D Byers
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C. Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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22
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Koehn JT, Beuning CN, Peters BJ, Dellinger SK, Van Cleave C, Crick DC, Crans DC. Investigating Substrate Analogues for Mycobacterial MenJ: Truncated and Partially Saturated Menaquinones. Biochemistry 2019; 58:1596-1615. [DOI: 10.1021/acs.biochem.9b00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Wang K, Jordan JH, Gibb BC. Molecular protection of fatty acid methyl esters within a supramolecular capsule. Chem Commun (Camb) 2019; 55:11695-11698. [DOI: 10.1039/c9cc06501f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We describe the use of a supramolecular nano-capsule for selective protection of cis- and trans-C18 mono-unsaturated fatty-acid esters.
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Affiliation(s)
- Kaiya Wang
- College Of Material Science & Technology
- Nanjing University of Aeronautics and Astronautics
- Nanjing 211100
- China
| | | | - Bruce C. Gibb
- Department of Chemistry
- Tulane University
- New Orleans
- China
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24
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Yu X, Tang W, Zhao T, Jin Z, Zhao S, Liu H. Confinement Effect on Molecular Conformation of Alkanes in Water-Filled Cavitands: A Combined Quantum/Classical Density Functional Theory Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:13491-13496. [PMID: 30350710 DOI: 10.1021/acs.langmuir.8b02209] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The depletion force exerted on an alkane molecule from surrounding solvent may greatly alter its conformation. Such a behavior is closely related to the selective molecular recognition, molecular sensors, self-assembly, and so on. Herein, we report a multiscale theoretical study on the conformational change of a single alkane molecule confined in water-filled cavitands, in which the quantum and classical density functional theories (DFTs) are combined to determine the grand potential of alkane-water system. Specifically, the intrinsic free energy of the alkane molecule is tackled by quantum DFT, while the solvent effect arising from the solvent density inhomogeneity in confined space is addressed by classical DFT. By varying the alkane chain length, pore size, and wettability of inner pore surface, we find that pore confinement and hydrophilic inner surface facilitate the alkane conformational change from extended state to helical state, which becomes more significant as the alkane chain length increases. Our findings, which are in line with previous experimental observations, provide not only the microscopic mechanism but also theoretical guidance for elaborately manipulating molecular conformation at the nanoscale.
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Affiliation(s)
| | | | | | - Zhehui Jin
- School of Mining and Petroleum Engineering, Department of Civil and Environmental Engineering , University of Alberta , Edmonton AB T6G 1H9 , Canada
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25
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Gupta S, Ramamurthy V. Characterization and Singlet Oxygen Oxidation of 1‐Alkyl Cyclohexenes Encapsulated Within a Water‐Soluble Organic Capsule. CHEMPHOTOCHEM 2018. [DOI: 10.1002/cptc.201800043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Shipra Gupta
- Department of Chemistry University of Miami Coral Gables, FL 33146 USA
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26
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Probing the pH dependent assembly-disassembly of water-soluble organic capsules with coumarins and anthracene. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2017.07.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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27
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Koehn J, Magallanes ES, Peters BJ, Beuning CN, Haase AA, Zhu MJ, Rithner CD, Crick DC, Crans DC. A Synthetic Isoprenoid Lipoquinone, Menaquinone-2, Adopts a Folded Conformation in Solution and at a Model Membrane Interface. J Org Chem 2018; 83:275-288. [PMID: 29168636 PMCID: PMC5759649 DOI: 10.1021/acs.joc.7b02649] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Indexed: 11/29/2022]
Abstract
Menaquinones (naphthoquinones, MK) are isoprenoids that play key roles in the respiratory electron transport system of some prokaryotes by shuttling electrons between membrane-bound protein complexes acting as electron acceptors and donors. Menaquinone-2 (MK-2), a truncated MK, was synthesized, and the studies presented herein characterize the conformational and chemical properties of the hydrophobic MK-2 molecule. Using 2D NMR spectroscopy, we established for the first time that MK-2 has a folded conformation defined by the isoprenyl side-chain folding back over the napthoquinone in a U-shape, which depends on the specific environmental conditions found in different solvents. We used molecular mechanics to illustrate conformations found by the NMR experiments. The measured redox potentials of MK-2 differed in three organic solvents, where MK-2 was most easily reduced in DMSO, which may suggest a combination of solvent effect (presumably in part because of differences in dielectric constants) and/or conformational differences of MK-2 in different organic solvents. Furthermore, MK-2 was found to associate with the interface of model membranes represented by Langmuir phospholipid monolayers and Aerosol-OT (AOT) reverse micelles. MK-2 adopts a slightly different U-shaped conformation within reverse micelles compared to within solution, which is in sharp contrast to the extended conformations illustrated in literature for MKs.
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Affiliation(s)
- Jordan
T. Koehn
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Estela S. Magallanes
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Benjamin J. Peters
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Cheryle N. Beuning
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Allison A. Haase
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Michelle J. Zhu
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Christopher D. Rithner
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Dean C. Crick
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Debbie C. Crans
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
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28
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Altaf AA, Hamayun M, Lal B, Tahir MN, Holder AA, Badshah A, Crans DC. Ferrocene-based anilides: synthesis, structural characterization and inhibition of butyrylcholinesterase. Dalton Trans 2018; 47:11769-11781. [DOI: 10.1039/c8dt01726c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Twenty-three compounds in two series of ferrocene-based anilides, with the general formula C5H5-Fe-C5H4-C6H4-NH-CO-C6H4-R (where R = H, F, Cl, CH3 and OCH3), have been synthesized and found to inhibit butyrylcholinesterase.
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Affiliation(s)
- Ataf Ali Altaf
- Department of Chemistry
- University of Gujrat
- Gujrat 50700
- Pakistan
| | | | - Bhajan Lal
- Department of Chemistry
- Shah Abdul Latif University
- Khairpur
- Pakistan
| | | | - Alvin A. Holder
- Department of Chemistry and Biochemistry
- Old Dominion University
- Norfolk
- USA
| | - Amin Badshah
- Department of Chemistry
- Quaid-i-Azam University
- Islamabad-45320
- Pakistan
| | - Debbie C. Crans
- Department of Chemistry
- Colorado State University
- Fort Collins
- USA
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29
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Chuang CH, Porel M, Choudhury R, Burda C, Ramamurthy V. Ultrafast Electron Transfer across a Nanocapsular Wall: Coumarins as Donors, Viologen as Acceptor, and Octa Acid Capsule as the Mediator. J Phys Chem B 2017; 122:328-337. [DOI: 10.1021/acs.jpcb.7b11306] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Chi-Hung Chuang
- Center
for Chemical Dynamics and Nanomaterials Research, Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Mintu Porel
- Department
of Chemistry, University of Miami, Coral Gables, Florida 33124, United States
| | - Rajib Choudhury
- Department
of Physical Sciences, Arkansas Tech University, Russellville, Arkansas 72801, United States
| | - Clemens Burda
- Center
for Chemical Dynamics and Nanomaterials Research, Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - V. Ramamurthy
- Department
of Chemistry, University of Miami, Coral Gables, Florida 33124, United States
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30
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Choudhury R, Ramamurthy V. Understanding the complexation of aliphatic and aromatic acids guests with octa acid. J PHYS ORG CHEM 2017. [DOI: 10.1002/poc.3795] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Rajib Choudhury
- Department of Chemistry; University of Miami; Coral Gables FL USA
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31
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Tang D, Barnett JW, Gibb BC, Ashbaugh HS. Guest Controlled Nonmonotonic Deep Cavity Cavitand Assembly State Switching. J Phys Chem B 2017; 121:10717-10725. [PMID: 29099596 DOI: 10.1021/acs.jpcb.7b09021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Octa-acid (OA) and tetra-endo-methyl octa-acid (TEMOA) are water-soluble, deep-cavity cavitands with nanometer-sized nonpolar pockets that readily bind complementary guests, such as n-alkanes. Experimentally, OA exhibits a progression of 1:1 to 2:2 to 2:1 host/guest complexes (X:Y where X is the number of hosts and Y is the number of guests) with increasing alkane chain length from methane to tetradecane. Differing from OA only by the addition of four methyl groups ringing the portal of the pocket, TEMOA exhibits a nonmonotonic progression of assembly states from 1:1 to 2:2 to 1:1 to 2:1 with increasing guest length. Here we present a systematic molecular simulation study to parse the molecular and thermodynamic determinants that distinguish the succession of assembly stoichiometries observed for these similar hosts. Potentials of mean force between hosts and guests, determined via umbrella sampling, are used to characterize association free energies. These free energies are subsequently used in a reaction network model to predict the equilibrium distributions of assemblies. Our models accurately reproduce the experimentally observed trends, showing that TEMOA's endo-methyl units constrict the opening of the binding pocket, limiting the conformations available to bound guests and disrupting the balance between monomeric complexes and dimeric capsules. The success of our simulations demonstrate their utility at interpreting the impact of even simple chemical modifications on supramolecular assembly and highlight their potential to aid bottom-up design.
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Affiliation(s)
- Du Tang
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
| | - J Wesley Barnett
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
| | - Bruce C Gibb
- Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
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Cendejas K, Parker HE, Molina D, Choudhury R. Supramolecular self-assembly of water-soluble cavitands: investigated by molecular dynamics simulation. J INCL PHENOM MACRO 2017. [DOI: 10.1007/s10847-017-0750-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Kamatham N, Da Silva JP, Givens RS, Ramamurthy V. Melding Caged Compounds with Supramolecular Containers: Photogeneration and Miscreant Behavior of the Coumarylmethyl Carbocation. Org Lett 2017. [DOI: 10.1021/acs.orglett.7b01572] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nareshbabu Kamatham
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33124, United States
| | - José P. Da Silva
- CCMAR
- Centre of Marine Sciences, University of Algarve, Campus de
Gambelas, 8005-139 Faro, Portugal
| | - Richard S. Givens
- Department
of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - V. Ramamurthy
- Department
of Chemistry, University of Miami, Coral Gables, Miami, Florida 33124, United States
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Thomas SS, Tang H, Gaudes A, Baggesen SB, Gibb CLD, Gibb BC, Bohne C. Tuning the Binding Dynamics of a Guest-Octaacid Capsule through Noncovalent Anchoring. J Phys Chem Lett 2017; 8:2573-2578. [PMID: 28535054 PMCID: PMC5574188 DOI: 10.1021/acs.jpclett.7b00917] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Hydrophobic or hydrophilic substituents have different effects on the binding dynamics of pyrene derivatives with a 2:1 capsule formed from two octaacid cavitands, showing a subtle interplay of different kinetic factors. Anchoring of the methyl group of 1-methylpyrene within one cavitand slowed the association and dissociation dynamics of the 1:1 complex by at least 1000 times when compared to the 1:1 complex for pyrene. This slow down for the transient formation of the 1:1 complex is responsible for the overall increase in stability of the 2:1 complex without affecting the overall capsule dissociation. For 1-pyrenemethanol, its residence time in the 2:1 capsule is shorter compared to that of pyrene despite both guests having similar equilibrium constants for the binding of the second cavitand, suggesting that the hydroxymethyl substituent close to the equatorial region of the capsule can interact with water during the partial opening of the capsule.
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Affiliation(s)
- Suma S. Thomas
- Department of Chemistry, University of Victoria, PO Box 1700 STN CSC, Victoria, BC, Canada V8W 2Y2
| | - Hao Tang
- Department of Chemistry, University of Victoria, PO Box 1700 STN CSC, Victoria, BC, Canada V8W 2Y2
| | - Adam Gaudes
- Department of Chemistry, University of Victoria, PO Box 1700 STN CSC, Victoria, BC, Canada V8W 2Y2
| | - Signe B. Baggesen
- Department of Chemistry, University of Victoria, PO Box 1700 STN CSC, Victoria, BC, Canada V8W 2Y2
| | - Corrine L. D. Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C. Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Cornelia Bohne
- Department of Chemistry, University of Victoria, PO Box 1700 STN CSC, Victoria, BC, Canada V8W 2Y2
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Wang K, Gibb BC. Mapping the Binding Motifs of Deprotonated Monounsaturated Fatty Acids and Their Corresponding Methyl Esters within Supramolecular Capsules. J Org Chem 2017; 82:4279-4288. [DOI: 10.1021/acs.joc.7b00264] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Kaiya Wang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Bruce C. Gibb
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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Predicting conformations and orientations of guests within a water soluble host: a molecular docking approach. J INCL PHENOM MACRO 2017. [DOI: 10.1007/s10847-017-0707-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Barnett JW, Gibb BC, Ashbaugh HS. Succession of Alkane Conformational Motifs Bound within Hydrophobic Supramolecular Capsular Assemblies. J Phys Chem B 2016; 120:10394-10402. [PMID: 27603416 DOI: 10.1021/acs.jpcb.6b06496] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
n-Alkane encapsulation experiments within dimeric octa-acid cavitand capsules in water reveal a succession of packing motifs from extended, to helical, to hairpin, to spinning top structures with increasing chain length. Here, we report a molecular simulation study of alkane conformational preferences within these host-guest assemblies to uncover the factors stabilizing distinct conformers. The simulated alkane conformers follow the trends inferred from 1H NMR experiments, while guest proton chemical shifts evaluated from Gauge Invariant Atomic Orbital calculations provide further evidence our simulations capture guest packing within these assemblies. Analysis of chain length and dihedral distributions indicates that packing under confinement to minimize nonpolar guest and host interior contact with water largely drives the transitions. Mean intramolecular distance maps and transfer free energy differences suggest the extended and helical motifs are members of a larger family of linear guest structures, for which the guest gauche population increases with increasing chain length to accommodate the chains within the complex. Breaks observed between the helical/hairpin and hairpin/spinning top motifs, on the other hand, indicate the hairpin and spinning top conformations are distinct from the linear family. Our results represent the first bridging of empirical and simulation data for flexible guests encapsulated within confined nanospaces, and constitute an effective strategy by which guest packing motifs within artificial or natural compartments can be rationalized and/or predicted a priori.
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Affiliation(s)
- J Wesley Barnett
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
| | - Bruce C Gibb
- Department of Chemistry, Tulane University , New Orleans, Louisiana 70118, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University , New Orleans, Louisiana 70118, United States
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Santos FS, Ramasamy E, Ramamurthy V, Rodembusch FS. Excited state behavior of benzoxazole derivatives in a confined environment afforded by a water soluble octaacid capsule. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2015.08.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
Photochemistry along with life as we know it originated on earth billions of years ago. Supramolecular Photochemistry had its beginning when plants that sustain life began transforming water into oxygen by carrying out light initiated reactions within highly organized assemblies. Prompted by the efforts of J. Priestly (photosynthesis), F. Sestini, S. Cannizaro, and C. Liebermann (solid-state photochemistry of santonin, quinones, and cinnamic acid), orderly scientific investigations of the link between light absorption by matter and molecules and the chemical and physical consequences began in the mid-1700s. By 1970 when Molecular Photochemistry had matured, it was clear that controlling photochemical reactions by conventional methods of varying reaction parameters like temperature and pressure would be futile due to the photoreactions' very low activation energies and enthalpies. During the last 50 years, the excited state behavior of molecules has been successfully manipulated with the use of confining media and weak interactions between the medium and the reactant molecule. In this context, with our knowledge from experimentation with micelles, cyclodextrins (CD), cucurbitruils (CB), calixarenes (CA), Pd nanocage, crystals, and zeolites as media, we began about a decade ago to explore the use of a new water-soluble synthetic organic cavitand, octa acid (OA) as a reaction container. The uniqueness of OA as an organic cavitand lies in that two OA molecules form a closed hydrophobic capsule to encapsulate water-insoluble guest molecule(s). The ability to include a large number of guest molecules in OA has provided an opportunity to examine the excited state chemistry of organic molecules in a hydrophobic, confined environment. OA distinguishes itself from the well-known cavitands CD and CB by its active reaction cavity absorbing UV-radiation between 200 and 300 nm and serving as energy, electron, and hydrogen donor. The freedom of guest molecules in OA, between that in crystals and isotropic solution can be transformed into photoproducts selectivity. The results of our photochemical investigations elaborated in this Account demonstrate that OA with a medium sized cavity exerts better control on excited state processes than the more common and familiar organic hosts such as CD, CB, CA, and micelles. By examining the photochemistry of a number of molecules (olefins, carbonyls, aromatics and singlet oxygen) that undergo varied reactions (cleavage, cycloaddition, cis-trans isomerization, oxidation and cyclization) within OA capsule, we have demonstrated that the free space within the container, the capsule influenced conformation and preorientation of guest molecules, supramolecular steric control, and capsular dynamics contribute to the altered excited state behavior. In this Account, we have shown that photochemistry based on concepts of physical organic and supramolecular chemistry continues to be a discipline with unlimited potential. The future of supramolecular photochemistry lies in synthetic, materials, medicinal, and biological chemistries. Success in these areas depends on synthesizing well-designed water-soluble hosts that can emulate complex biological assemblies, organizing and examining the behavior of supramolecular assemblies on solid surfaces, rendering the photoreactions catalytic, and delivering encapsulated drugs in a targeted fashion.
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Ramamurthy V, Jockusch S, Porel M. Supramolecular Photochemistry in Solution and on Surfaces: Encapsulation and Dynamics of Guest Molecules and Communication between Encapsulated and Free Molecules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:5554-5570. [PMID: 25521719 DOI: 10.1021/la504130f] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Supramolecular assemblies that help to preorganize reactant molecules have played an important role in the development of concepts related to the control of excited-state processes. This has led to a persistent search for newer supramolecular systems (hosts), and this review briefly presents our work with octa acid (OA) to a host to control excited-state processes of organic molecules. Octa acid, a water-soluble host, forms 1:1, 2:1, and 2:2 (host-guest) complexes with various organic molecules. A majority of the guest molecules are enclosed within a capsule made up of two molecules of OA whereas OA by itself remains as a monomer or aggregates. Luminescence and (1)H NMR spectroscopy help to characterize the structure and dynamics of these host-guest complexes. The guest molecule as well as the host-guest complex as a whole undergoes various types of motion, suggesting that the guests possess freedom inside the confined space of the octa acid capsule. In addition, the confined guests are not isolated but are able to communicate (energy, electron, and spin) with molecules present closer to the capsule. The host-guest complexes are stable even on solid surfaces such as silica, clay, α-Zr phosphate, TiO2, and gold nanoparticles. This opens up new opportunities to explore the interaction between confined guests and active surfaces of TiO2 and gold nanoparticles. In addition, this allows the possibility of performing energy and electron transfer between organic molecules that do not adsorb on inert surfaces of silica, clay, or α-Zr phosphate. The results summarized here, in addition to providing a fundamental understanding of the behavior of molecules in a confined space provided by the host OA, are likely to have a long-range effect on the capture and release of solar energy.
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Affiliation(s)
- V Ramamurthy
- †Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
| | - Steffen Jockusch
- ‡Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Mintu Porel
- †Department of Chemistry, University of Miami, Coral Gables, Florida 33146, United States
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Abstract
This review focuses on molecular containers formed by assembly processes driven by the hydrophobic effect, and summarizes the progress made in the field over the last ten years. This small but growing facet of supramolecular chemistry discusses three classes of molecules used by researchers to investigate how self-assembly can be applied to form discrete, mono-dispersed, and structurally well-defined supramolecular entities. The approaches demonstrate the importance of preorganization of arrays of rigid moieties to define a specific form predisposed to bind, fold, or assemble. As the examples demonstrate, studying these systems and their properties is teaching us how to control supramolecular chemistry in water, shedding light on aspects of aqueous solutions chemistry, and illustrating novel applications that harness the unique properties of the hydrophobic effect.
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Affiliation(s)
- Jacobs H Jordan
- Department of Chemistry, Tulane University, New Orleans, LA 70118, USA.
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Safe storage of radical initiators within a polyaromatic nanocapsule. Nat Commun 2014; 5:4662. [DOI: 10.1038/ncomms5662] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Accepted: 07/10/2014] [Indexed: 12/26/2022] Open
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