Multichromophores for Nonlinear Optics: Designing the Material Properties by Electrostatic Interactions

Abstract

To fully exploit the promise of molecular materials for NLO applications, inter- and supramolecular interactions must be accounted for. We review our recent work on electrostatic interchromophore interactions in multichromophores for NLO applications. The discussion is based on a bottom-up modeling strategy: each chromophore is described in terms of an essential state model, validated and parameterized against spectroscopic data for solvated chromophores. The relevant information is then used to build a model for clusters of chromophores interacting through electrostatic forces. Exact NLO responses and spectra calculated within this model fully account for collective and cooperative interchromophore interactions, which can either amplify or suppress NLO responses; supramolecular engineering of multichromophores is a powerful tool for the design of NLO materials. Moreover, new features emerge in multichromophores with no counterpart at the single-chromophore level, offering new exciting opportunities for applications.

Differential Behavior of Amino–Imino Constitutional Isomers in Nonlinear Optical Processes

“…According to (3) in this simple model the hyperpolarizability depends on the charge-transfer energy, DV. Here, one can assume, as Lu et al, [8] that m VB % 0 and also that m CT have similar values for amino and imino structures.…”

“…[2] This kind of molecules possesses a low-energy charge-transfer electronic state (CT, also denoted as [D + -L-A À ]), and it exhibits a large second-and third-order nonlinear optical response. [3] Many studies of these compounds reveal an important correlation between hyperpolarizabilities and bond alternation of the conjugate bridge of the molecule, suggesting large effects induced by small changes in the electronic structure of the molecules. [2] Important features of this kind of molecules are the chemical and themal stability and the synthetic versatility for structural modification and functionalization (e.g.…”

Enhanced Two‐Photon Absorption of Organic Chromophores: Theoretical and Experimental Assessments

“…[146][147][148][149] Since only a few electronic transitions often predominate in the nonlinear resonant spectra of organic molecules, effective few-state models have become very popular for rational molecular design of NLO-phores. [90,103,127,[150][151][152][153][154][155][156][157][158][159][160] For branched structures, the Frenkel exciton model has been shown to provide a valuable qualitative tool to connect the photophysical properties of branched chromophores to those of their corresponding monomeric counterpart. [113,120,[161][162][163] Theoretical limits for TPA activities have also been explored as well.…”

The intramolecular charge transfer in a donor–π–acceptor dianion probed by resonance Raman spectroscopy and quantum chemical calculations

“…[1,2] The high asymmetry in the charge distribution of the excited states in this kind of molecules is responsible for several of their specific properties and photonics applications, as in nonlinear optical devices, [3] molecular switches, [4] and optical sensors, [5] among others. Use has been made of molecular design aiming to enhance such properties, and, in particular, the use of strong electron donor and acceptor groups connected by suitable conjugated π-linkers has been one of the strategies.…”