Aggregates of Cyanine Dyes: When Molecular Vibrations and Electrostatic Screening Make the Difference

Abstract

Aggregates of cyanine dyes are currently investigated as promising materials for advanced electronic and photonic applications. The spectral properties of aggregates of cyanine dyes can be tuned by altering the supramolecular packing, which is affected by the length of the dye, the presence of alkyl chains, or the nature of the counterions. In this work, we present a joint experimental and theoretical study of a family of cyanine dyes forming aggregates of different types according to the length of the polymethinic chain. Linear and nonlinear optical spectra of aggregates are rationalized here in terms of an essential-state model accounting for intermolecular interactions together with the molecular polarizability and vibronic coupling. A strategy is implemented to properly account for screening effects, distinguishing between electrostatic intermolecular interactions relevant to the ground state (mean-field effect) and the interactions relevant to the excited states (excitonic effects). To the best of our knowledge, this is the first attempt to simulate nonlinear spectral properties of aggregates of symmetric dyes accounting for molecular vibrations.

Disruption Mechanisms of Enveloped Viruses by Ionic and Nonionic Surfactants

“…This indicates quenching of the 670 nm signal, and it is possible if DiI molecules form aggregates in a suitable solvent or medium. Delledonne et al and others reported that DiI has an emission peak at about 575 nm for a range of solvents, and the emission peak is red-shifted in a mixed polar solvent of ethanol and water. − They explained this with J-aggregation of the lipophilic dye in polar solvents. Our spectral data also indicate the formation of such DiI aggregates.…”

Tuning the Optical Properties Through Hydrogen Bond‐assisted H‐aggregate Formation: The ODIN Case

“…[20] Here, our attention is focused on how the solvent polarity and capability to donate or accept hydrogen bonds influences the aggregation status and, consequently, ODIN's spectroscopic properties. Absorption and emission spectra are expected to be very sensitive probes of intermolecular interactions, [26,27] but to fulfill a complete understanding of the aggregation status and its consequences on photo-physics, ultrafast transient absorption spectroscopy, transient infrared spectroscopy and quantum chemical calculations (density functional level of theory, DFT) have been used. DMSO and CHCl 3 have been chosen as solvents, respectively representing a polar and highly prone to accept hydrogen bonds environment and a scarcely polar and poorly capable of forming hydrogen bonds environment.…”