Tuning the Fluorescence and the Intramolecular Charge Transfer of Phenothiazine Dipolar and Quadrupolar Derivatives by Oxygen Functionalization

Abstract

A series of new naphthalimide and phenothiazine-based push−pull systems (NPI-PTZ1−5), in which we structurally modulate the oxidation state of the sulfur atom in the thiazine ring, i.e., S(II), S(IV), and S(VI), was designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction. The effect of the sulfur oxidation state on the spectral, photophysical, and electrochemical properties was investigated. The steady-state absorption and emission results show that oxygen functionalization greatly improves the optical (absorption coefficient and fluorescence efficiency) and nonlinear optical (hyperpolarizability) features. The cyclic voltammetry experiments and the quantum mechanical calculations suggest that phenothiazine is a stronger electron donor unit relative to phenothiazine-5-oxide and phenothiazine-5,5-dioxide, while the naphthalimide is a strong electron acceptor in all cases. The advanced ultrafast spectroscopic measurements, transient absorption, and broadband fluorescence up conversion give insight into the mechanism of photoinduced intramolecular charge transfer. A planar intramolecular charge transfer (PICT) and highly fluorescent excited state are populated for the oxygen-functionalized molecules NPI-PTZ2,3 and NPI-PTZ5; on the other hand, a twisted intramolecular charge transfer (TICT) state is produced upon photoexcitation of the oxygen-free derivatives NPI-PTZ1 and NPI-PTZ4, with the fluorescence being thus significantly quenched. These results prove oxygen functionalization as a new effective synthetic strategy to tailor the photophysics of phenothiazine-based organic materials for different optoelectronic applications. While oxygen-functionalized compounds are highly fluorescent and promising active materials for current-to-light conversion in organic light-emitting diode devices, oxygen-free systems show very efficient photoinduced ICT and may be employed for light-to-current conversion in organic photovoltaics.

Gel Materials with Rubber‐Rubbing‐Chromic Luminescence: A Portable Tool for On‐Spot Composing Highly Encrypted Information

“…The possible noncovalent interactions between DPP and LGG enable DPP molecules in the supramolecular gel to undergo intramolecular charge transfer, thereby resulting the fluorescence emission. [ 12 ] The excited‐state supramolecular chirality of DPP‐LGG cogel at LGG/DPP = 4:1 can also be measured by circularly polarized luminescence (CPL) spectroscopy (Figure S7, Supporting Information). However, mirror patterns are obtained in CPL spectra, dissymmetry factor values ( g lum ), and CD spectra (Figures S7 and S8, Supporting Information), which indicates the solvent‐induced inversion of supramolecular chirality.…”

An Efficient Aequorea victoria Green Fluorescent Protein for Stimulated Emission Depletion Super-Resolution Microscopy

“…The experimental setup for the femtosecond transient absorption and fluorescence up-conversion measurements has been described elsewhere [ 50 , 51 ]. In particular, a 800-nm radiation is amplified by the Ti:Sapphire laser system (Spectra Physics) and then converted into 400-nm excitation pulses (ca.…”

Phenothiazine and phenothiazine-5,5-dioxide-based push–pull derivatives: synthesis, photophysical, electrochemical and computational studies

“…[1][2][3][4][5][6][7][8] These donor-acceptor (D-A) derivatives exhibit unique photonic properties and that can be improved by simple synthetic changes. 9,10 In these p-conjugated chromophores, the heteroatom-containing cyclic systems were primarily used to tune the photophysical and redox properties of push-pull dyes. Many studies have been reported on developing novel push-pull organic materials for optoelectronic applications.…”

“…Many studies have been reported on developing novel push-pull organic materials for optoelectronic applications. 7,[10][11][12][13][14] Our group is interested in the chemistry of phenothiazine. Phenothiazine is a heterocyclic compound with non-planar geometry and a bowl-shaped structure containing electron-rich nitrogen (N) and sulfur (S) heteroatoms.…”