Effects Of Molecular Symmetry Research Articles

Effect of Molecular Symmetry on the Self-Assembly Behavior of AB2 Linear–Branched Block Copolymers

Effect of Molecular Symmetry on the Self-Assembly Behavior of AB₂ Linear–Branched Block Copolymers

Catalytic Pyrolysis of Plastic Waste and Molecular Symmetry Effects: A Review

The present review addresses the latest findings and limitations in catalytic pyrolysis for the processing of plastic waste into valuable fuels. Compared to thermal degradation of plastics, catalytic pyrolysis provides better results in regards to the quality of the obtained liquid hydrocarbon fuel. Different types of catalysts can be used in order to improve the thermal degradation of plastics. Some of the most used catalysts are different types of zeolites (HUSY, HZSM-5, Hβ), Fluid Catalytic Cracking (FCC), silica-alumina catalysts, or natural clays. There is a need to find affordable and effective catalysts in the aim of achieving commercialization of catalytic pyrolysis of plastic waste. Therefore, this study summarizes and presents the most significant results found in the literature in regards to catalytic pyrolysis. This paper also investigates the symmetry effects of molecules on the pyrolysis process.

Effect of Molecular Symmetry on Fused‐Ring Electron Acceptors

Two isomeric fused‐ring electron acceptors F7TC‐1 and F7TC‐2 with different molecular symmetry are designed and synthesized, and the effect of molecular symmetry is studied. All side chains are located on the same side of the fused‐ring core in axisymmetric F7TC‐1, whereas they are evenly located on both sides of the fused‐ring core in centrosymmetric F7TC‐2. The molecular symmetry shows slight effects on the absorption spectra, energy levels, and bandgaps of the two molecules, but notable effects on crystallinity, molecular packing, film morphology, and device performance. F7TC‐1‐ and F7TC‐2‐based organic solar cells show power conversion efficiencies of 1.08% and 11.14%, respectively. Different molecular packing and film morphology lead to a big difference in device performance.

Energy Landscapes for Electronic Structure

Orbital-optimized multiple self-consistent-field (SCF) solutions are increasingly being interpreted as mean-field approximations of diabatic or excited electronic states. However, surprisingly little is known about the topology of the electronic energy landscape from which these multiple solutions emerge. In this contribution, we extend energy landscape methods, developed for investigating molecular potential energy surfaces, to investigate and understand the structure of the electronic SCF energy surface. Using analytic gradients and Hessians, we systematically identify every real SCF minimum for the prototypical H4 molecule with the 3-21G basis set, and the index-1 saddles that connect these minima. The resulting SCF energy landscape has a double-funnel structure, with no high-energy local minima. The effect of molecular symmetry on the pathways is analyzed, and we demonstrate how the SCF energy landscape changes with the basis set, SCF potential, molecular structure, and spin state. These results provide guiding principles for the future development of algorithms to systematically identify multiple SCF solutions from an orbital optimization perspective.

Photoelectron angular distributions in photodetachment from polarised d-like states: the case of HO2 −

We present a photoelectron imaging study of the angular distributions in HO2 − photodetachment. The transitions studied correspond to electron detachment from the a ″ HOMO and a′ HOMO−1 of HO2 −, yielding the neutral hydroperoxy radical in the ground and first excited electronic states. The experimental results are analysed using the p-d variant of the general model for photodetachment from mixed-character states. In this model, the parent anion molecular orbitals or the corresponding Dyson orbitals are described as superpositions of atomic p and d functions placed at a chosen centre in the molecular frame. As photoelectron angular distributions are sensitive to the long-range scaling of the parent orbitals, modelling the experimental results yields insight into the asymptotic behaviour of anionic wavefunctions. In the model, the long-range behaviour of diffuse orbitals is parameterised using the effective charges defining the basis functions. These parameters do not correspond to physical charges in the anion, but describe the long-range scaling of the p and d components of the model function and, therefore, the parent anion orbital. The experimental and model results for HO2 − are compared to NO− and O2 −, shedding light on the effects of molecular symmetry and chemical bonding structures on the photoelectron angular distributions.

Biaxial ordering in the supercooled nematic phase of bent-core mesogens: effects of molecular symmetry and outer wing lateral groups

ABSTRACT In previous research, we have found that the incorporation of three lateral substituents on bent-core oxadiazole-based liquid crystals has allowed for the presence of a nematic phase that supercooled to room temperature. X-ray diffraction (XRD) studies of these derivatives have confirmed that the nematic phase consists of cybotactic clusters. Moreover, the wide-angle XRD pattern showed a splitting indicative of local biaxial ordering within this phase. In this paper, we report the phase behaviour of two series of compounds that contain up to four lateral methyl groups. In one series, the arrangement of the lateral groups is symmetrical, and in the other case, the groups are not symmetrically distributed. All of the non-symmetric derivatives supercool to room temperature in the nematic phase, while symmetric derivatives tend to crystallise well above room temperature. XRD analysis of all of these compounds indicates the presence of cybotactic order. However, a splitting of the wide-angle XRD pattern is observed only in derivatives with lateral groups on the outer benzene rings, regardless of their supercooling behaviour, indicating the crucial influence of these substituents on the molecular packing.

Molecular symmetry effects on the stability of highly ordered smectic phases

ABSTRACTIn an effort to control the phase ranges of highly ordered smectic phases, we examined the impact of molecular symmetry on phase behaviour of a series of 12 symmetrical and unsymmetrical 4,4′-dialkanoyloxybiphenyl derivatives. Combined differential scanning calorimetry, polarised optical microscopy, and X-ray diffraction studies indicated that the compounds studied formed smectic F liquid crystals, and in some cases, G phases at lower temperatures. Although the clearing temperatures were largely unaffected by molecular symmetry, the transitions from the SmF liquid crystals to more ordered phases were consistently lowered upon reducing the molecular symmetry. As a result, unsymmetrical molecules had broader mesophases than their higher symmetry isomers, suggesting a strategy for tuning the phase behaviour of these highly ordered lamellar phases, which have been widely targeted for organic semiconductors.

Triptycene-Bis(aroyleneimidazole)s as Non-Fullerene Acceptors: The Missing Links.

The syntheses of four triptycene-bis(aroyleneimidazole)s-the missing links with respect to the previously reported triptycene-mono(aroyleneimidazole)s and triptycene-tris(aroyleneimidazole)s-are presented. Their optoelectronic properties and use as non-fullerene acceptors in organic photovoltaics with poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}[3-fluoro-2-(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl) (PTB7) as a donor are described; these systems reach a maximum power conversion efficiency of 2 %. Furthermore, the effect of molecular symmetry on the photovoltaic device performance is discussed.

Unsymmetry effect of hexa-peri-hexabenzocoronenes on columnar mesophase behaviour

ABSTRACTTo address the effects of molecular symmetry on the phase of columnar liquid crystals, a series of unsymmetry (C1) and symmetry (D3h) hexa-peri-hexabenzocoronene derivatives was prepared. Compounds 3 and 4, as well as a mixture of compounds 3+4, all had a significantly lower melting temperature and clearing temperature than high-symmetry compounds (D6h), and all results show a strong dependence on molecular symmetry.

Tuning light-emitting properties of N-phenylcarbazole-capped anthrylvinyl derivatives by symmetric and isomeric effects

This paper focuses on effects of molecular symmetry and isomerisation on light-emitting properties based on N-phenylcarbazole-capped anthrylvinyl derivatives. We have designed and synthesized three isomeric 10-(arylvinyl)anthracenes with N-phenylcarbazole as the mono aryl moiety whose 2-, 3-, or carbazole-9-yl-phenyl positions are linked, and their optical and electroluminescence properties are investigated and compared with analogous 9,10-bis(arylvinyl)anthracenes. The results showed that, contrary to the dual N-phenylcarbazole-capped analogues, the three mono N-phenylcarbazole-capped isomers have neither aggregation-induced emission nor mechanofluorochromism although they are characterized by twisted π-backbone and grinding-induced amorphization. It is observed that the mono substitution can significantly blue-shift the emission spectra and greatly improve the electroluminescence performances, accompanying by the remarkably isomeric effect. This finding demonstrates that changing the molecular substitution patterns could effectively alter and tune the light-emitting properties to greatly widen the scope of molecular candidates applicable in optical and optoelectronic fields.

Correction to "Effects of Molecular Symmetry on the Electronic Transitions in Carotenoids".

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Effects of Molecular Symmetry on the Electronic Transitions in Carotenoids”Leszek Fiedor*†, Heriyanto†‡, Joanna Fiedor†§, and Mariusz Pilch*†∥View Author Information† Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland‡ Ma Chung Research Center for Photosynthetic Pigments, Ma Chung University, Villa Puncak Tidar N-01, Malang 65151, Indonesia§ Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland∥ Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, PolandCite this: J. Phys. Chem. Lett. 2016, 7, 17, 3502Publication Date (Web):August 25, 2016Publication History Published online25 August 2016Published inissue 1 September 2016https://doi.org/10.1021/acs.jpclett.6b01827Copyright © 2016 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views447Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (134 KB) Get e-Alerts Get e-Alerts

Effects of Molecular Symmetry on the Electronic Transitions in Carotenoids.

The aim of this work is the verification of symmetry effects on the electronic absorption spectra of carotenoids. The symmetry breaking in cis-β-carotenes and in carotenoids with nonlinear π-electron system is of virtually no effect on the dark transitions in these pigments, in spite of the loss of the inversion center and evident changes in their electronic structure. In the cis isomers, the S2 state couples with the higher excited states and the extent of this coupling depends on the position of the cis bend. A confrontation of symmetry properties of carotenoids with their electronic absorption and IR and Raman spectra shows that they belong to the C1 or C2 but not the C2h symmetry group, as commonly assumed. In these realistic symmetries all the electronic transitions are symmetry-allowed and the absence of some transitions, such as the dark S0 → S1 transition, must have another physical origin. Most likely it is a severe deformation of the carotenoid molecule in the S1 state, unachievable directly from the ground state, which means that the Franck-Condon factors for a vertical S0 → S1 transition are negligible because the final state is massively displaced along the vibrational coordinates. The implications of our findings have an impact on the understanding of the photophysics and functioning of carotenoids.

Effects of molecular symmetry on quantum reaction dynamics: novel aspects of photoinduced nonadiabatic dynamics.

Nonadiabatic coupling terms (NACTs) between different electronic states lead to fast radiationless decay in photoexcited molecules. Using molecular symmetry, i.e., symmetry with respect to permutation of identical nuclei and inversion of the molecule in space, the irreducible representations of the NACTs can be determined with a combination of molecular symmetry arguments and quantization rules. Here, we extend these symmetry rules for electronic states and coupling elements and demonstrate the importance of molecular symmetry for nonadiabatic nuclear dynamics. As an example, we consider the NACTs related to the torsion around the CN bond in C5H4NH. We present the results of quantum dynamical simulations of the photoinduced large amplitude torsion on three coupled electronic states and show how the interference between wavepackets leads to radiationless decay, which depends on the symmetry of the NACTs. Moreover, we show that the nuclear spin of the system determines the symmetry of the initial nuclear wave function and thus influences the torsional dynamics. This may open new possibilities for nuclear spin selective laser control of nuclear dynamics.

Effects of molecular symmetry on the directions of nuclear flux densities during tunnelling in double well potentials

Coherent tunnelling in molecular systems with cyclic and non-cyclic symmetric double well potentials may proceed with similar nuclear densities, but with entirely different flux densities. For sufficiently high potential barriers, the nuclear densities may even become indistinguishable, whereas the patterns of the flux densities at a given time remain pincer-motion type for the cyclic systems, but unidirectional for the non-cyclic one. This effect is traced back to symmetry breaking of the cyclic to the non-cyclic model. Accordingly, nuclear flux densities are much more sensitive to symmetry breaking than nuclear densities. For a proof of principle, the phenomenon is demonstrated by means of three one-dimensional models. The cyclic model I represents torsion in oriented B2Cl2F2, the non-cyclic model II is constructed from I by symmetry breaking and the non-cyclic model III represents tunnelling by inversion of oriented NH3.

Effect of Molecular Symmetry on the Spectra and Dynamics of the Intramolecular Charge Transfer (ICT) State of Peridinin

The spectroscopic properties and dynamics of the excited states of two different synthetic analogues of peridinin were investigated as a function of solvent polarity using steady-state absorption, fluorescence, and ultrafast time-resolved optical spectroscopy. The analogues are denoted S-1- and S-2-peridinin and differ from naturally occurring peridinin in the location of the lactone ring and its associated carbonyl group, known to be obligatory for the observation of a solvent dependence of the lifetime of the S(1) state of carotenoids. Relative to peridinin, S-1- and S-2-peridinin have their lactone rings two and four carbons more toward the center of the π-electron system of conjugated carbon-carbon double bonds, respectively. The present experimental results show that as the polarity of the solvent increases, the steady-state spectra of the molecules broaden, and the lowest excited state lifetime of S-1-peridinin changes from ∼155 to ∼17 ps which is similar to the magnitude of the effect reported for peridinin. The solvent-induced change in the lowest excited state lifetime of S-2-peridinin is much smaller and changes only from ∼90 to ∼67 ps as the solvent polarity is increased. These results are interpreted in terms of an intramolecular charge transfer (ICT) state that is formed readily in peridinin and S-1-peridinin, but not in S-2-peridinin. Quantum mechanical computations reveal the critical factors required for the formation of the ICT state and the associated solvent-modulated effects on the spectra and dynamics of these molecules and other carbonyl-containing carotenoids and polyenes. The factors are the magnitude and orientation of the ground- and excited-state dipole moments which must be suitable to generate sufficient mixing of the lowest two excited singlet states.

Controlling the Position of Functional Groups at the Liquid/Solid Interface: Impact of Molecular Symmetry and Chirality

With the aim of controlling the position of functional groups in a substrate-supported monolayer, a new family of functionalized linear alkyl chains was designed and synthesized, aided by molecular mechanics and dynamics simulations of its two-dimensional self-assembly on graphite. The self-assembly of these amino functionalized diamides at the liquid/solid interface was investigated with scanning tunneling microscopy. Intermolecular hydrogen-bonding interactions involving amides, combined with the effect of molecular symmetry and chirality, were found to guide the self-assembly. Control of the relative position and orientation of the amine groups was achieved, in the case of enantiopure compounds. Interestingly, racemates led to both racemic conglomerate and solid solution formation, with a concomitant loss of positional and orientational control of the amino groups as a result.

Effect of Molecular Symmetry on Potency in Novel Down-Modulators of the CD4 Receptor

Effect of Molecular Symmetry on Potency in Novel Down-Modulators of the CD4 Receptor

Classification and averaging of random orientation single macromolecular diffraction patterns at atomic resolution

Single molecule imaging experiments at future X-ray free electron laser sources will provide large number of random 3D oriented diffraction patterns with low counting statistics. Grouping of this vast amount of data into classes of similar orientations and averaging must be performed before their orientation and structure reconstruction can take place. Classification algorithms performing all-pair pattern comparisons scale badly with the number of patterns in terms of their computing requirements, which presents a problem in case of improving resolution and decreasing signal to noise ratios. We describe an algorithm performing significantly less pattern comparisons and render classification possible in such cases. The invariance of patterns against rotation of the object about the primary beam axis is also exploited to decrease the number of classes and improve the quality of class averages. This work is the first, which demonstrates that it is possible to classify a dataset with realistic target parameters: 10 keV photon energy, 10(12) photons/pulse, 100 x 100 nm2 focusing, 538 kDa protein, 2.4 A resolution, 10(6) patterns, approximately 3 x 10(4) classes, <1 degree misorientation within classes. The effects of molecular symmetry and its consequences on classification are also analyzed.

Excitation followed by stimulated-emission from diabatic levels in all- trans- and 15- cis-β-carotenes: Effects of molecular symmetry and solvent polarity

Upon-excitation, with subpicosecond pulses, to the pair of overlapped optically-allowed 1 B u + (1) and optically-forbidden 3 A g - (2) levels (‘diabatic levels’), we observed stimulated-emission from five diabatic levels, above and below the original pair, which included 1 B u - (1), 3 A g - (0), 3 A g - (1), 3 A g - (2) and 3 A g - (3). We ascribed this to diabatic excitation followed by radiative transitions between the 3 A g - and 1 B u + (or 1 B u - ) vibronic levels in aggregates. The number of observed stimulated-emission peaks increased from two to five in n-hexane on going from all- trans- to 15- cis-β-carotene, and in all- trans-β-carotene from non-polar to polar solvent, which we ascribed to configurational change and electronic polarization in the conjugated chain.

Effects of molecular symmetry on enhanced ionization by intense laser pulses

When molecules are driven by intense laser fields linearly polarized along the internuclear axis, their ionization rate vs the internuclear separation $R$ is known to have a maximum at some critical intermediate separation ${R}_{c}$. We show that such a maximum should occur only in molecules whose highest occupied molecular orbitals (HOMOs) are such that the electron cloud is concentrated along the internuclear axis (i.e., $\ensuremath{\sigma}$-type HOMOs). For molecular systems whose HOMO symmetry prevents electron probability distribution along this axis, we find that the ionization rate increases monotonically with increasing $R$ until saturation occurs. In other words, for such molecular systems, there is no critical ${R}_{c}$ at which molecular ionization is maximum.