Aromatic Molecular Complexes of the Electron Donor-Acceptor Type.

Andrews, Lawernece J.

doi:10.1021/cr60171a001

Cited by 210 publications

(67 citation statements)

References 147 publications

(249 reference statements)

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“…These π-π interactions are often referred to as an "aromatic donor-acceptor interactions" [159][160][161], but others reached different conclusions. Hunter et al [162] and Waters [163] suggested that it is not the sheer presence of donor-acceptor interactions alone that is decisive, instead they are more complex and consist of electrostatic, hydrophobic and van der Waals interactions.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Graphene-philic surfactants for nanocomposites in latex technology

Mohamed

Ardyani

Bakar

et al. 2016

Advances in Colloid and Interface Science

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Graphene is the newest member of the carbon family, and has revolutionized materials science especially in the field of polymer nanocomposites. However, agglomeration and uniform dispersion remains an Achilles" heel (even an elephant in the room), hampering the optimization of this material for practical applications. Chemical functionalization of graphene can overcome these hurdles but is often rather disruptive to the extended piconjugation, altering the desired physical and electronic properties. Employing surfactants as stabilizing agents in latex technology circumvents the need for chemical modification allowing for the formation of nanocomposites with retained graphene properties. This article reviews the recent progress in the use of surfactants and polymers to prepare graphene/polymer nanocomposites via latex technology. Of special interest here are surfactant structure-performance relationships, as well as background on the roles surfactantgraphene interactions for promoting stabilization.

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Section: Accepted M Manuscriptmentioning

confidence: 99%

Graphene-philic surfactants for nanocomposites in latex technology

Mohamed

Ardyani

Bakar

et al. 2016

Advances in Colloid and Interface Science

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“…Nevertheless, spectroscopic studies of a variety of electron donor/acceptor systems have in many cases confirmed the correlation of the CT band energy with the IP and EA. 11,26,27 It is now generally accepted that the strong characteristic UV absorption bands of D•I 2 and other related complexes are due to the CT excitation. However, the ground state complexes are bound simply by the dispersion force and electrostatic multipole interactions.…”

Section: The Ct Systemmentioning

confidence: 99%

“…26,27 Various conventional spectroscopic methods have been employed to investigate these complexes in the liquid, gas, and solid phases. In Fig.…”

Section: The Ct Systemmentioning

confidence: 99%

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Femtosecond real-time probing of reactions. XXI. Direct observation of transition-state dynamics and structure in charge-transfer reactions

Cheng

Zhong

Zewail

1996

The Journal of Chemical Physics

100

126

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Two-dimensional spectroscopy: Theory of nonstationary, time-dependent absorption and its application to femtosecond processes J. Chem. Phys. 91, 4485 (1989); 10.1063/1.456786 Femtosecond resolution ultrafast ion reaction time measurement a pulsed-laser field desorption time-of-flight spectroscopy AIP Conf. Proc. 146, 610 (1986) This paper in the series gives our full account of the preliminary results reported in a communication ͓Cheng, Zhong, and Zewail, J. Chem. Phys. 103, 5153 ͑1995͔͒ on real-time femtosecond ͑fs͒ studies of the transition state of charge-transfer ͑CT͒ reactions, generally described as harpooning reactions. Here, in a series of experimental studies in a molecular beam, and with the help of molecular dynamics, we elucidate the microscopic elementary dynamics and the structure of the transition states for the isolated, bimolecular reaction of benzenes ͑electron donor͒ with iodine ͑electron acceptor͒. The transition state is directly reached by fs excitation into the CT state of the complex Bz•I 2 , and the dynamics is followed by monitoring the product build up or the initial transition-state decay. We further employed the fs resolution in combination with the kinetic-energy resolved time-of-flight and recoil anisotropy techniques to separate different reaction pathways and to determine the impact geometry. Specifically, we have studied: ͑1͒ the temporal evolution of the transition state ͑ ‡ ͒ and of the final products ͑ ͒; ͑2͒ the product translational-energy distributions; ͑3͒ the recoil anisotropy ͑␤͒ in each channel; ͑4͒ the reaction time dependence on the total energy; ͑5͒ the dynamical and structural changes with varying CT energy ͑ionization potential-electron affinity-Coulomb energy͒. Such a change is made by replacing the electron donor from benzene to toluene, and to xylenes and trimethylbenzenes of different symmetries. We have also studied deutrobenzene as a donor. The reaction mechanism involves two exit channels. The first one ͑ionic͒ follows the ionic potential of the CT state. Following the harpooning ͑Bz ϩ•I 2 Ϫ ͒, the transition state•I͔* ‡ evolves on the adiabatic potential to produce Bz ϩ •I Ϫ and I products. The second channel ͑neutral͒ is due to the coupling of the transition state to neutral, locally excited, iodine repulsive states and, in this case, the products are Bz•IϩI. The latter process is an intermolecular electron transfer and occurs on an ultrafast time scale of 250 fs, resulting in a greater yield for the neutral channel. Molecular dynamics simulations support this dynamical picture and provide the time scales for trajectories in the transition-state region and in the product valley. The geometry of the transition state is determined from the anisotropy measurements and we found a nearly axial geometry with the iodine axis of recoil tilted 30°-35°away from the transition moment. These angular dependencies are related to the molecular structure and the electronic structure with highest occupied molecular orbit-lowest occupied molecular orbit descriptions. By...

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“…Aromatic molecules form complexes of the electron donor-acceptor type [5] and they can react as hydrogen-bonding bases [9]. Carbon-bound hydrogen atoms, e.g.…”

Section: Structure Elementsmentioning

confidence: 99%

Tertiary structure and function of transfer-RNA

Melcher

1972

Biophysik

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Summary. In analogy to the globular protein structures the predominant stabilization factor of which is surface energy a compact model with the smallest possible surface of the tertiary structure of t-RNA is suggested. The principle of folding is --according to the clover leaf model --the superposition of the three leaves. The three loops form a ring (loop-stack). The stem can be placed on this molecular body bringing the CCA end into the vicinity of the loop-stack, where the CCA end can be bound. The structures of the RNA chain are subordinated to this globular structural principle. Under the influence of the GT~CG sequence the CCA end is able to undergo structural changes, thus allowing to explain the role of t-RNA in the aminoacylation process and the structural differences between t-RNA, aminoacyl-t-RNA, and peptidyl-t-RNA. Furthermore it is possible to comment on the existence of the characteristic and modified bases, the role of magnesium ions and the chemical reactions of these compounds. IntroduetionWater is necessary for the stabilization of tertiary structures of biological macromolecules. The properties of water are decisive for the arrangement of hydrophobic groups in the interior and of hydrophilic groups on the surface of the molecule. The tendency to reduce the surface as much as possible exists because free energy, the thermodynamic criterion for reaction equilibrium of the stabihty of a tertiary structure, depends on the size of the surface and the interfacial tension [84].That is the reason for the formation of micelles and why most proteins prefer globular structures in aqueous solutions. Decisive for the stability of the tertiary structure of such chain molecules like proteins and nucleic acids is the sequence, because it determines the order of the hydrophobic and hydrophilie forces and the possibilities of hydrogen bond formation. Hydrophilic groups which can be bound together in the interior of the structure by hydrogen bridges will not participate in the formation of the surface, because these bonds are energetically more favoured than hydrogen bridges of these groups with the surrounding water. Additional binding through coordinative or ionic bonds with the help of cations can be of great influence on the resulting structure.In the case of nucleic acids two groups have to be distinguished, DNA and RNA. These two classes do not only seem to differ in their stabilization principle [6i] but show also other evident differences.Generally DNA is built by two very long complementary chains. For such long complementary chains the double helix seems to be the best suited structure.

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Aromatic Molecular Complexes of the Electron Donor-Acceptor Type.

Cited by 210 publications

References 147 publications

Graphene-philic surfactants for nanocomposites in latex technology

Graphene-philic surfactants for nanocomposites in latex technology

Femtosecond real-time probing of reactions. XXI. Direct observation of transition-state dynamics and structure in charge-transfer reactions

Tertiary structure and function of transfer-RNA

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