Ab Initio Computations of the Geometrical, Electronic, and Vibrational Properties of the Ground State, the Anion Radical, and the N,N‘-Dihydro Cation Radical of 4,4‘-Bipyridine Compared to Transient Raman Spectra

Ould-Moussa, Lynda; Poizat, O.; Castellà-Ventura, Martine; Buntinx, G.; Kassab, E.

doi:10.1021/jp951839h

Cited by 73 publications

(95 citation statements)

References 37 publications

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“…Even including sufficient diffuse basis functions (aug-cc-pVDZ), the SCF description (both Koopmans theorem and ∆-SCF) is even qualitatively inadequate; the anion is predicted to be unstable. This is already known from earlier work 47,49,50 . As visible in Table 1, we found that electron correlations (which, by definition, measure deviation from SCF) cannot be adequately included via MP2 and the OVGF 21,22 : the 44BPY •− anion remains unstable.…”

Section: Lowest Electron Attachment Energiessupporting

confidence: 57%

A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions

Bâldea

2014

Faraday Discuss.

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Abstract:The accurate determination of the lowest electron attachment (EA) and ionization (IP) energies for molecules embedded in molecular junctions is important for correctly estimating, e.g., the magnitude of the currents (I) or the biases (V ) where an I −V -curve exhibits a significant non-Ohmic behavior. Benchmark calculations for the lowest electron attachment and ionization energies of several typical molecules utilized to fabricate single-molecule junctions characterized by n-type conduction (4,4'-bipyridine, 1,4-dicyanobenzene, and 4,4'-dicyano-1,1'-biphenyl) and p-type conduction (benzenedithiol, biphenyldithiol, hexanemonothiol, and hexanedithiol] based on the EOM-CCSD (equation-of-motion coupled-cluster singles and doubles) state-of-the-art method of quantum chemistry are presented. They indicate significant differences from the results obtained within current approaches to molecular transport. The present study emphasizes that, in addition to a reliable quantum chemical method, basis sets much better than the ubiquitous double-zeta set employed for transport calculations are needed. The latter is a particularly critical issue for correctly determining EA's, which is impossible without including sufficient diffuse basis functions. The spatial distribution of the dominant molecular orbitals (MO's) is another important issue, on which the present study draws attention, because it sensitively affects the MO-energy shifts Φ due to image charges formed in electrodes. The present results cannot substantiate the common assumption of a point-like MO midway between electrodes, which substantially affects the actual Φ-values.

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Section: Lowest Electron Attachment Energiessupporting

confidence: 57%

A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions

Bâldea

2014

Faraday Discuss.

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“…The physics behind the similarity exhibited by the these numerical results is the following. The twisting angle θ of the 44BPY molecule is determined by the competition between the π-electronic interaction of the pyridyl fragments, which favors π-electrons delocalized between coplanar pyridyl rings (θ = 0), and the steric repulsion between the ortho H atoms, which is diminished by a twisted conformation (θ = 0) [32]. The latter prevails in the neutral species 44BPY 0 (empty/oxidized LUMO), which is nonplanar ( fig.…”

mentioning

confidence: 99%

Extending the Newns-Anderson model to allow nanotransport studies through molecules with floppy degrees of freedom

Bâldea¹

2012

EPL

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-The Newns-Anderson model is ubiquitous in studies of the molecular transport in the presence of solvent (outer) reorganization. The present work demonstrates that intramolecular reorganization can also be significant for the transport through molecules with floppy degrees of freedom, for which the Newns-Anderson model can be extended. The expressions of the model parameters deduced from electronic structure calculations for (4, 4')-bipyridine (44BPY) quantitatively differ from those characteristic for outer reorganization due to strong intramolecular anharmonicities. These expressions can be utilized as input in transport calculations for 44BPY-based molecular junctions of experimental interest

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“…This important shift may be compared to those already observed upon quaternisation of the pyridyl ring, for example on going from pyridine to pyridinium (+47 cm -1 ) 89 or to N-methyl-pyridinium (+49 cm -1 ) 90 or from 44BPY to N,N′-diprotonated cation 44BPYH 2 2 + (+44 cm -1 ) 56 or to N,N′-dihydro cation radical 44BPYH 2 •+ (+55 cm -1 ). 55 Modes 1 and 12 are characterized by a potential energy largely redistributed upon adsorption. The frequencies of both modes are significantly upward shifted on passing from PY to adsorbed PY.…”

Section: (+4)mentioning

confidence: 99%

“…The IR and Raman spectra of crystalline 44BPY have been reported in the literature. [52][53][54][55][56] Table 8 contains our more recent experimental data. 56 Accurate assignments have been obtained by our previous ab initio and B3LYP calculations using 3-21G(+*) and 6-31G(+*) basis sets.…”

Section: Free and Adsorbed 44bpymentioning

confidence: 99%

“…56 Accurate assignments have been obtained by our previous ab initio and B3LYP calculations using 3-21G(+*) and 6-31G(+*) basis sets. 55,56 The vibrational frequencies of 44BPY adsorbed on alumina, observed by FT-IR spectrometry by Bagshaw and Cooney, 26 are listed in Table 8. Only the PEDs of free 44BPY and adsorbed 44BPY on Al 4 O 6 are presented in Table 8.…”

Section: Free and Adsorbed 44bpymentioning

confidence: 99%

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Theoretical Study of Pyridine and 4,4‘-Bipyridine Adsorption on the Lewis Acid Sites of Alumina Surfaces Based on Ab Initio and Density Functional Cluster Calculations

Kassab

Castellà-Ventura

2005

J. Phys. Chem. B

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The interactions of pyridine and 4,4'-bipyridine with the Lewis acid sites of alumina surfaces are investigated using ab initio and density functional calculations. Four cluster models of different sizes and shapes are chosen to represent the Lewis acid sites: three hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12) and one non-hydrogenated cluster Al(4)O(6). The Hartree-Fock (HF) and B3LYP approaches with two basis sets 6-31G and 6-31+G are used to calculate the geometries, the electronic structures, the vibrational frequencies, and the adsorption energies of the complexes formed upon interaction of pyridine or 4,4'-bipyridine ligands on the cluster surfaces. Electronic structures are determined by the electrostatic potential (ESP) analysis of charges. Adsorption energies are calculated with corrections made for zero-point energies (ZPE) and basis set superposition error (BSSE). The ESP analysis of atomic charges reveals that the charge-transfer effects are more important in Lewis complexes formed with Al(4)O(6) cluster than in those formed with hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12). The significantly larger charge transferred from pyridine or 4,4'-bipyridine ligand to Al(4)O(6) cluster should increase the adsorption energy of these complexes. Consequently, at all levels of calculation, the adsorption energies of pyridine and 4,4'-bipyridine complexed to Al(4)O(6) cluster ( approximately 46 kcal/mol), which compare very well to experiment, are strongly larger than those obtained for both pyridine and 4,4'-bipyridine ligands complexed to Al(OH)(3) (32 kcal/mol), Al(4)O(9)H(6) (24 kcal/mol) and Al(10)O(21)H(12) (25 kcal/mol) clusters. The corrected adsorption energy is found to be insensitive to basis set and electron correlation effects. It essentially depends on the ionic character of the cluster model rather than on its size. For 4,4'-bipyridine complexes, similar results to those obtained for pyridine are found, and the geometry and the amount of charge of the unbound pyridyl ring are unchanged upon complexation. The calculated vibrational frequencies and frequency shifts are little sensitive to the size and shape of the cluster model. The two ring stretching modes 8a and 19b of pyridine and 4,4'-bipyridine observed in the 1400-1600 cm(-1) region are the most affected modes upon adsorption, in good agreement with the available infrared and Raman data.

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Ab Initio Computations of the Geometrical, Electronic, and Vibrational Properties of the Ground State, the Anion Radical, and the N,N‘-Dihydro Cation Radical of 4,4‘-Bipyridine Compared to Transient Raman Spectra

Cited by 73 publications

References 37 publications

A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions

A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions

Extending the Newns-Anderson model to allow nanotransport studies through molecules with floppy degrees of freedom

Theoretical Study of Pyridine and 4,4‘-Bipyridine Adsorption on the Lewis Acid Sites of Alumina Surfaces Based on Ab Initio and Density Functional Cluster Calculations

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