title: On the Simulation of Two-dimensional Electronic Spectroscopy of Indole-containing Peptides.
abstract: A benchmark study of low-cost multiconfigurational CASSCF/CASPT2 schemes for computing the electronic structure of indole is presented. This facilitates the simulation of near-ultraviolet (UV) pump visible (VIS) probe (i.e. two-color) two-dimensional electronic spectra (2DES) of homo- and hetero-aggregates as well as for processing of multiple snapshots from molecular dynamics simulations. Fingerprint excited-state absorption signatures of indole are identified in a broad spectral window between 10 and 25 k cm-1. The 18-24 k cm-1spectral window which has no absorption of the monomer and noninteracting aggregates is ideally suited to embed charge-transfer signatures in stacked aggregates. The small peptide Trp-cage, containing a tryptophan and a tyrosine amino acids, having indole and phenol as side chains, respectively, serves to prove the concept. Clear charge-transfer signatures are found in the proposed spectral window for an interchromophore distance of 5 Å making near-UV pump VIS probe 2DES a suitable technique for resolving closely packed aggregates. We demonstrate that 2DES utilizing ultra-short pulses has the potential to resolve the nature of the spectroscopically resolved electronic states and that the line shapes of the excited-state absorption signals can be correlated to the polarity of the relevant states.
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università degli Studi di Bologna, Bologna, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Giussani
authors.affiliation: International School for Advanced Studies (SISSA), Trieste, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Marcheselli
authors.affiliation: Department of Chemistry, University of California, Irvine, CA.
authors.forename: Shaul
authors.initials: S
authors.lastname: Mukamel
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università degli Studi di Bologna, Bologna, Italy.|Dipartimento di Chimica Industriale "Toso Montanari", Universita degli Studi di Bologna, Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Garavelli
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università degli Studi di Bologna, Bologna, Italy.|Dipartimento di Chimica Industriale "Toso Montanari", Universita degli Studi di Bologna, Bologna, Italy.
authors.forename: Artur
authors.initials: A
authors.lastname: Nenov