New Styryl Phenanthroline Derivatives as Model D−π−A−π−D Materials for Non‐Linear Optics

Abstract

Four novel push-pull systems combining a central phenanthroline acceptor moiety and two substituted benzene rings, as a part of the conjugated π-system between the donor and the acceptor moieties, have been synthetized through a straightforward and efficient one-step procedure. The chromophores display high fluorescence and a peculiar fluorosolvatochromic behaviour. Ultrafast investigation by means of state-of-the-art femtosecond-resolved transient absorption and fluorescence up-conversion spectroscopies allowed the role of intramolecular charge transfer (ICT) states to be evidenced, also revealing the crucial role played by both, the polarity and proticity of the medium on the excited state dynamics of the chromophores. The ICT processes, responsible for the solvatochromism, also lead to interesting non-linear optical (NLO) properties: namely great two photon absorption cross-sections (hundreds of GM), investigated by the Two Photon Excited Fluorescence (TPEF) technique, and large second order hyperpolarizability coefficients, estimated through a convenient solvatochromic method.

Exploring a new class of singlet fission fluorene derivatives with high-energy triplets

“…The emission spectrum loses vibrational structure and clearly red-shis upon increasing the solvent polarity. 43,44 The positive uorosolvatochromism is the largest for NF, still remarkable but smaller for AF and only hinted for F. These results, in agreement with previous studies, [35][36][37] suggest the strongest push-pull character for NF, an intermediate but still signicant push-pull character for AF and a negligible push-pull character for F. The F F values were found to be quite low in cyclohexane (CH): 3% for F, 37% for AF and 0.3% for NF. Efficient non-radiative decay pathways for the excited states of these compounds are thus operative in non-polar solvents.…”

Tuning the Photophysical Properties of Push‐Pull Azaheterocyclic Chromophores by Protonation: A Brief Overview of a French‐Spanish‐Czech Project

“…[1] In this context, π-deficient nitrogen heterocycles such as pyridine, [2] quinoline, [3] diazines (pyridazine, [4] pyrimidine, [5] and pyrazine [6] ), benzodiazines (quinoxaline, [ 3 , 6 ] quinazoline, [ 3 , 5 c] phthalazine, [7] etc. ), phenanthroline, [8] triazines, [9] and tetrazines [10] are considered as moderate-to-strong electron withdrawing groups. Some pushpull chromophores that bear these heterocycles as the electron-attracting part exhibit intense luminescence properties.…”

Probing the structural features and the micro-heterogeneity of various deep eutectic solvents and their water dilutions by the photophysical behaviour of two fluorophores

“…The investigated fluorescent probes (shown in Scheme 1) were synthesized as described in reference [51] for PyI and in reference [50] for X5.…”

“…The two fluorophores were dissolved separately into the different DESs, and their photophysical properties were determined by recording their steady-state and time-resolved absorption and emission spectra. Both fluorophores are sensitive to the polarity of the medium: PyI features negative solvatochromism, that is its absorption spectrum shifts toward shorter wavelengths with increasing polarity [51]; while X5 exhibits positive fluorosolvatochromism, with its emission spectrum shifting to longer wavelengths when the polarity of the medium increases [50].…”

“…In order to shed light on the structural features of a set of differently structured DESs, a spectroscopic femtosecond-resolved study is proposed in this work with the use of suitable fluorescence probes, whose photophysical properties and excited state dynamics have already been deeply investigated in our laboratory [50][51][52][53][54]. Specifically, an N-methylpyridinium iodide (2-4-(diphenylamino)phenyl-ethenyl-1-methylpyridinium iodide, PyI) was chosen as a polarity and viscosity probe, while a phenanthroline derivative (4,4'-((1E,1'E)-(1,10-phenanthroline-2,9diyl)bis(ethene-2,1-diyl))bis(3-methoxy-N,N-dimethylaniline, X5), showing fluorosolvatochromism and bearing protonation sites, was used as polarity and H-bond probe.…”