Paracyclophanes as Model Compounds for Strongly Interacting π-Systems, Part 3: Influence of the Substitution Pattern on Photoabsorption Properties

Pfister, Johannes; Schon, Christof; Roth, Wolfgang R.; Kaiser, Conrad; Lambert, Christoph; Gruß, Katrin; Braunschweig, Holger; Fischer, Ingo; Fink, Reinhold F.; Engels, Bernd

doi:10.1021/jp200823q

Cited by 16 publications

(17 citation statements)

References 67 publications

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“…At this point we want to discuss the results of p-DHPC in light of our recent multiphoton ionization (MPI) data. 13 For the S 1 ' S 0 transition, less than 1% o-DHPC contamination was found to dominate the electronic spectrum in the 31 500 cm À1 region. Computations revealed that the geometry change upon excitation in p-DHPC was so large that the Franck-Condon factors (FCF) close to the origin of the S 1 ' S 0 transition vanish and the signal from the small amount of ortho-isomer dominates the spectrum.…”

Section: Resultsmentioning

confidence: 89%

“…p-DHPC was synthesized according to the literature approach. 13,49 In the p-DHPC experiments a small residual signal from the MHPC sample was still present, which could be subtracted based on the C 8 H 8 + signal, which is unique to MHPC spectra.…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

“…12 Small paracyclophanes are volatile enough to be investigated in the gas phase to shed light on their electronic structure. [13][14][15][16][17][18][19] We use the term p-p interaction in a general sense to describe coupling between the two six-membered rings, and not to imply an exclusive role of the p orbitals in the ring-ring bonding. 4 The most important parameter is the interaction energy, i.e.…”

Section: Introductionmentioning

confidence: 99%

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A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

Hemberger

Bodi

Schon

et al. 2012

Phys. Chem. Chem. Phys.

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The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of three hydroxy-substituted [2.2]paracyclophane derivatives were studied yielding adiabatic ionization energies and dissociative photoionization energies (appearance energies). The simplest dissociation pathway is the breaking of both CH(2)-CH(2) bridge units and fragmenting the molecular ion in half to yield xylylene neutral and cationic fragments. The experimental data show that this process is outcompeted by a faster, higher energy channel, possibly yielding cyclooctatetraene derivatives. The role of the reaction coordinate, the effect of large amplitude motions on the density of states function at low and high energies and the temperature dependent 'population gap' in the internal energy distribution in large molecules are discussed in the context of applying statistical models to the dissociation. Computational approaches to the binding energy of paracyclophanes are marred with pitfalls. Noncovalent interactions play a major role in keeping paracyclophanes bound by some 200 kJ mol(-1) with respect to the two xylylene motifs, and the covalent CH(2)-CH(2) bonds are mostly counteracted by the geometric strain. The stabilizing effects are twofold: first, paracyclophanes are aromatic compounds, whereas xylylenes are not. Thus, the aromaticity of the molecule is induced by dimerization. Second, dispersive π-π interactions also stabilize the molecule. We evaluated 23 different computational chemistry approaches, and found that very few of the favorably scaling ones give an adequate description of this system. Among the DFT functionals tested, only PBE-D3 and perhaps M06-2X yielded consistently accurate results, comparable with MP3 and CCSD, or the G4 and CBS-QB3 composite methods. MP2 results in general suffer from significant overbonding.

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Section: Resultsmentioning

confidence: 89%

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

Hemberger

Bodi

Schon

et al. 2012

Phys. Chem. Chem. Phys.

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“…177,178 However, enhanced excited-state geometries and vibrational frequencies could lead to more accurate 0-0 transition energies for π → π * and n → π * excitations. [179][180][181] Therefore, any potential improvements for SCS-CC2 seem to be problem specific, hence we need to carry out a comparison with CC2.…”

Section: Which Cc2 Variant Is More Appropriate?mentioning

confidence: 99%

Noncovalently bound excited-state dimers: a perspective on current time-dependent Density Functional Theory approaches applied to aromatic excimer models

Hancock

Goerigk

2022

Preprint

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Excimers are supramolecular systems whose binding strength is influenced by many factors that are ongoing challenges for computational methods, such as charge transfer, exciton coupling, and London dispersion interactions. Treating the various intricacies of excimer binding at an adequate level is expected to be particularly challenging for time-dependent Density Functional Theory (TD- DFT) methods. In addition to well-known limitations for some TD-DFT methods in the description of charge transfer or exciton coupling, the inherent London dispersion problem from ground-state DFT translates to TD-DFT. While techniques to appropriately treat dispersion in DFT are well- developed for electronic ground states, these dispersion corrections remain largely untested for excited states. Herein, we aim to shed light on current TD-DFT methods, including some of the newest developments. The binding of four model excimers is studied across nine density functionals with and without the application of additive dispersion corrections against a wave function reference of SCS-CC2/CBS(3,4) quality, which approximates select CCSDR(3)/CBS data adequately. To our knowledge, this is the first study that presents single-reference wave function dissociation curves at the complete basis set level for the assessed model systems. It is also the first time range-separated double-hybrid density functionals are applied to excimers. In fact, those functionals turn out to be the most promising for the description of excimer binding followed by global double hybrids. Range-separated and global hybrid—particularly with large fractions of Fock exchange—are outperformed by double hybrids and yield worse dissociation energies and inter-molecular equilibrium distances. The deviation between assessed functional and reference increases with system size, most likely due to missing dispersion interactions. Additive dispersion corrections of the DFT-D3(BJ) and DFT-D4 types reduce the average errors for TD-DFT methods but do so inconsistently and therefore do not offer a black-box solution in their ground-state parametrised form. The lack of appropriate description of dispersion effects for TD-DFT methods is likely hindering the practical application of the herein identified more efficient methods. Dispersion corrections parametrised for excited states appear to be an important next step to improve the applicability of TD-DFT methods and we hope that our work assists with the future development of such corrections.

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“…TCP, a trichromophore, is a natural extension to these studies with three close lying excited states. However, here, the flexibility of TCP is limited by the formation of the macrocycle, placing the three ultraviolet chromophores in well-defined orientations, a subject more thoroughly investigated in [2.2]paracyclophane and its derivatives. ,,− …”

Section: Introductionmentioning

confidence: 99%

Binding Water Clusters to an Aromatic-Rich Hydrophobic Pocket: [2.2.2]Paracyclophane–(H₂O)_n, n = 1–5

Buchanan

Zwier

2014

J. Phys. Chem. A

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[2.2.2]Paracylcophane (tricyclophane, TCP) is a macrocycle with three phenyl substituents linked by ethyl bridges (-CH2CH2-) in the para-position, forming an aromatic-rich pocket capable of binding various substituents, including nature's solvent, water. Building on previous work [Buchanan, E. G.; et al. J. Chem. Phys. 2013, 138, 064308] that reported on the ground state conformational preferences of TCP, the focus of the present study is on the infrared and ultraviolet spectroscopy of TCP-(H2O)n clusters with n = 1-5. Resonant two-photon ionization (R2PI) was used to interrogate the mass selected electronic spectrum of the clusters, reporting on the perturbations imposed on the electronic states of TCP as the size of the water clusters bound to it vary in size from n = 1-5. The TCP-(H2O)n S0-S1 origins are shifted to lower frequency from the monomer, indicating an increased binding energy of the water or water network in the excited state. Ground state resonant ion-dip infrared (RIDIR) spectra of TCP-(H2O)n (n = 1-5) clusters were recorded in the OH stretch region, which probes the H-bonded water networks present and the perturbations imposed on them by TCP. The experimental frequencies are compared with harmonic vibrational frequencies calculated using density functional theory (DFT) with the dispersion-corrected functional ωB97X-D and a 6-311+g(d,p) basis set, providing firm assignments for their H-bonding structures. The H2O molecule in TCP-(H2O)1 sits on top of the binding pocket, donating both of its hydrogen atoms to the aromatic-rich interior of the monomer. The antisymmetric stretch fundamental of H2O in the complex is composed of a closely spaced set of transitions that likely reflect contributions from both para- and ortho-forms of H2O due to internal rotation of the H2O in the binding pocket. TCP-(H2O)2 also exists in a single conformational isomer that retains the same double-donor binding motif for the first water molecule, with the second H2O acting as a donor to the first, thereby forming a water dimer. The OH stretch infrared spectrum reflects a cooperative strengthening of both π-bound and OH···O H-bonds due to binding to TCP. The TCP-(H2O)n, n = 3-5 clusters all form H-bonded cycles, retaining their preferred structures in the absence of TCP, but distorted significantly by the presence of the TCP molecule. TCP-(H2O)3 divides its population between two conformational isomers that differ in the direction of the H-bonds in the cycle, either clockwise or counterclockwise, which are distinguishable by virtue of the C2 symmetry of the TCP monomer. TCP-(H2O)4 and TCP-(H2O)5 have OH stretch IR spectra that are close analogues of their benzene-(H2O)n counterparts in the H-bonded OH stretch region, but differ somewhat in the free and π OH stretch regions as the tetramer and pentamer cycles begin to spill out of the pocket interior. Lastly, excited state RIDIR spectroscopy in the OH stretch region is used to probe the response of water cluster to ultraviolet excitation, showing how the proximity of a give...

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Paracyclophanes as Model Compounds for Strongly Interacting π-Systems, Part 3: Influence of the Substitution Pattern on Photoabsorption Properties

Cited by 16 publications

References 67 publications

A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

Noncovalently bound excited-state dimers: a perspective on current time-dependent Density Functional Theory approaches applied to aromatic excimer models

Binding Water Clusters to an Aromatic-Rich Hydrophobic Pocket: [2.2.2]Paracyclophane–(H₂O)_n, n = 1–5

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Paracyclophanes as Model Compounds for Strongly Interacting π-Systems, Part 3: Influence of the Substitution Pattern on Photoabsorption Properties

Cited by 16 publications

References 67 publications

A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

A pass too far: dissociation of internal energy selected paracyclophane cations, theory and experiment

Noncovalently bound excited-state dimers: a perspective on current time-dependent Density Functional Theory approaches applied to aromatic excimer models

Binding Water Clusters to an Aromatic-Rich Hydrophobic Pocket: [2.2.2]Paracyclophane–(H2O)n, n = 1–5

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Product

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Binding Water Clusters to an Aromatic-Rich Hydrophobic Pocket: [2.2.2]Paracyclophane–(H₂O)_n, n = 1–5