A Recent Development of the CS INDO Model. Treatment of Solvent Effects on Structures and Optical Properties of Organic Dyes‡‡dedicated to Professor G. Del Re

Baraldi, Ivan; Momicchioli, Fabio; Ponterini, Glauco; Vanossi, Davide

doi:10.1016/s0065-3276(08)60481-5

Cited by 12 publications

(9 citation statements)

References 46 publications

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“…In the SCF molecular orbital calculations, we used the most recent version of the CS INDO parametrization reported in refs , (for a general discussion on the CS INDO parameters see also ref ). With the purpose of giving a fairly good description of the electronic charge distributions for the ground and excited S 1 and S 2 states, CIPSI calculations were performed, on the whole MO basis set, with the two-classes version of the CIPSI algorithm. , The perturbation treatment was based on a Moller−Plesset partition of the electronic Hamiltonian.…”

Section: Methodology and Calculationsmentioning

confidence: 99%

Exciton Effects in the Dimer and Higher Aggregates of a Simple Merocyanine Dye. A CS INDO CI Based Theoretical Study

2000

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A simple streptomerocyanine with five methine carbons (Mc) has been used as a suitable model system to investigate theoretically the optical properties in organized assemblies of merocyanine dyes. The subject was treated by a methodology making use of a semiempirical quantum chemistry description of the isolated chromophore within the Frenkel exciton theory. Both an extended CS INDO CIPSI and easier CS INDO SCI (with different parametrizations of electron repulsion integrals) schemes were applied in order to establish the role played by the quality of the wave functions. The exciton states were built on the 1 (ππ * ) (HOMO-LUMO) excited-state responsible for the "color" band of Mc. Exciton effects were first analyzed for two stable dimer structures, having H-and J-type character, located by use of a semiempirical intermolecular potential and the simulated annealing method. Then, attention was shifted from dimers to higher-order model aggregates built in such a way as to obtain typical H (columnar) and J (staircase) arrangements. Exciton-state properties (energies and transition dipole moments) were studied as a function of the aggregation number N (up to N ) 50). The results are discussed with reference to the approximations used to calculate the excitonic matrix as well as to the effects of changing from CIPSI to simple SCI schemes.

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Section: Methodology and Calculationsmentioning

confidence: 99%

Exciton Effects in the Dimer and Higher Aggregates of a Simple Merocyanine Dye. A CS INDO CI Based Theoretical Study

2000

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“…More recently, the electronic states of both cyanine and merocyanine dyes have been the subject of several MO SCF CI studies. 1,[16][17][18][45][46][47][48][49][50] In this section we focus our attention on the strongly allowed long-wavelength absorption which, for the three chromogen types, mainly arises from electronic excitation from the p H to the p* L orbitals. For the sake of brevity, we only report in Fig.…”

Section: Dependence Of the Colour Band Maximum (K Theo Max ) On The N...mentioning

confidence: 99%

Photoisomerization of simple merocyanines: a theoretical and experimental comparison with polyenes and symmetric cyanines

Baraldi

Momicchioli

Ponterini

et al. 2002

Phys. Chem. Chem. Phys.

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The structure and electronic spectra of merocyanines are intermediate between those of acyclic polyenes and cationic symmetric cyanines of comparable sizes, shifting from one to the other as a result of a solvent polarity change. In this paper we address, both theoretically and experimentally, the question of how the photochemical behaviour of simple merocyanines compares with that of polyenes and symmetric cyanines. After a brief theoretical re-appraisal of the absorption maxima dependence on the chain length in the three classes of chromogens, we analyse the calculated potential-energy curves for two photoisomerization coordinates of a polyene, a symmetric cyanine and a merocyanine of comparable sizes. The results concerning both the energy curves and the nature of the relevant electronic states, particularly the TICT (twisted intramolecular charge transfer) character of the S 1 state at the perpendicular geometry, reveal the existence of a near relationship between merocyanines and symmetric ionic polymethines, traceable back to their being odd-alternant systems. The presence of a low-lying 1 (np*) state at the trans geometry and the associated solvent-modulated vibronic coupling with the 1 (p H p L *) state dominate the experimentally accessible photochemical behaviour of two simple merocyanines and make it peculiar with respect to those of both polyenes and symmetric ionic cyanines.y Dedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays. Fig. 1 Dominant resonance structures in strepto polymethinecyanines (SPC), strepto polymethinemerocyanines (SPMC) and acyclic polyenes (AP).

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“…Within a standard two-state scheme for D-A systems, in which the electronic structure is assumed to be controlled by the mixing of the neutral D-A and charge-separated D + -A À resonance structures, we have accounted for the absorption and emission solvatochromisms of a series of merocyanines. [7][8][9] More recently, an explicit use of the two-state model has enabled us to estimate, both quantum-mechanically and from UV-visible spectroscopic data, the polarizabilities and first hyperpolarizabilities of a few simple merocyanines with varying chromophore lengths: 10 the reliability of such an approach was proved by the near coincidence of the two-state-model and EFISH values of the relevant b components along the series of compounds.…”

Section: Introductionmentioning

confidence: 99%

Electronic spectra and (hyper)polarizabilities of non-centrosymmetric D–A–D chromophores. An experimentally based three-state model and a theoretical TDDFT study of ketocyanines

Ponterini

Vanossi

Krasnaya

et al. 2011

Phys. Chem. Chem. Phys.

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The electronic structure, spectra and linear and second-order polarizabilities of two symmetric ketocyanines, which are prototypic examples of D-A-D chromophores, have been investigated with two different toolsets: (i) the so-called 'essential-state model', here comprising three states, the ground and two lowest excited (1)ππ* states, has been adapted for these non-centrosymmetric, yet symmetric compounds to determine their permanent electric dipole moments, polarizabilities and first hyperpolarizabilities making use of experimental transition energies and moments; (ii) extensive TDDFT calculations have provided ground-state conformational results consistent with NMR-derived structural information, energies and dipole moments of up to 20 lowest-lying electronic states as well as, within the sum-over-states (SOS) scheme, the most relevant components of the polarizabilities and first hyperpolarizabilities. The two levels of description form consistent pictures of the ketocyanine excited states that provide the most relevant contributions to hyperpolarizabilities: extension of the SOS set beyond the three states of the basic model left unchanged (within ∼10%) the calculated vector component of the second-order polarizability tensor along the direction of the ground-state dipole moment (β(y)). Both approaches indicate that these D-A-D compounds, in spite of their quasi-linear structure, reminiscent of that of centrosymmetric quadrupolar chromophores, feature significant second-order molecular polarizabilities. These rapidly increase with the length of the polyenic bridges in the chromophores. About half of the total value of β(y) is predicted to come from the three-level-term part, β(y,3), most of which derives from the contribution involving the three electronic states of the essential-state model.

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A Recent Development of the CS INDO Model. Treatment of Solvent Effects on Structures and Optical Properties of Organic Dyes‡‡dedicated to Professor G. Del Re

Cited by 12 publications

References 46 publications

Exciton Effects in the Dimer and Higher Aggregates of a Simple Merocyanine Dye. A CS INDO CI Based Theoretical Study

Exciton Effects in the Dimer and Higher Aggregates of a Simple Merocyanine Dye. A CS INDO CI Based Theoretical Study

Photoisomerization of simple merocyanines: a theoretical and experimental comparison with polyenes and symmetric cyanines

Electronic spectra and (hyper)polarizabilities of non-centrosymmetric D–A–D chromophores. An experimentally based three-state model and a theoretical TDDFT study of ketocyanines

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