Density functional theory chromophore calculations

Density functional theory (DFT) calculations of two types of push-pull chromophores built around thiophene-based 7t-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions (Figure 6) have been carried out to assign the relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores <2003CEJ3670>. 

The following sections are purposely separated into specific structural classes of square planar Pt" complexes of the general formulae Pt(NAN)(C=CR)2, [Pt(NANAN) (OCR)]+, Pt(NANAC)(C=CR), rra s-Pt(PR3)2(OCR)2, and d.v-Pt(PAP)(( =CR)2, where NAN is a bidentate 2,2 -bipyridine, NANAN and NANAC are tridentate polypyridines, PR3 is a monodentate phosphine, and PAP is a bidentate phosphine ligand. The final section of this work is dedicated to recent electronic structure calculations on these molecules with an emphasis on the successful application of DFT (density functional theory) and TD-DFT (time-dependent density functional theory) methods towards understanding the absorption and emission processes of these chromophores. 

Deriving a force field for chromophores entails calculations of the electronic structure of these large molecules. In recent times, the density functional theory (DFT)[15j approach has been gaining popularity in the... 

The absorption of far-IR photons can be detected by the messenger method, which is based on forced evaporation of a weakly-bound ligand from the cluster complex upon the absorption of a small number of IR photons. The messenger method assumes that only the metal cluster acts as a chromophore while the detached atomic or molecular ligand merely delivers the message about the absorption event without perturbing the structural properties of the cluster. This assumption is fulfilled for most transition metal clusters complexed with rare gas atoms. In combination with density functional theory calculations, the experimental IR (multi) photon dissociation, IR-(M)PD, spectra often enable an unambiguous determination of the clusters structure. 

Recently, an extensive study on the photoexcitation and isomerization of PYP was published. In this study, a combination of molecular dynamics simulation techniques and time-dependent density functional theory calculations were used. Several interesting results were obtained. Out of five separate simulations that were performed of the excited state, two showed a twisted configuration of the chromophore, and in three, the chromophore retained its trans configuration. This could explain the two different excited states observed in the ultrafast absorption measurement (see above). 

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