Molecular design of novel non-planar heteropolycyclic fluorophores with bulky substituents: convenient synthesis and solid-state fluorescence characterization

Abstract

Novel indeno[1,2-b]benzo[4,5-e]pyran-11-one-type fluorophores exhibiting intense solid-state fluorescence were conveniently synthesized and the relation between their solid-state photophysical properties and the X-ray crystal structures were investigated, which demonstrates that non-planar structures with sterical hindered substituents prevent the fluorophores from forming short pi-pi contacts causing fluorescence quenching in the solid state.

A Self‐Quenching‐Resistant Carbon‐Dot Powder with Tunable Solid‐State Fluorescence and Construction of Dual‐Fluorescence Morphologies for White Light‐Emission

“…[ 21 ] Furthermore, the emission maximum (525 nm) of the powder has remarkable red-shift of 111 nm from that of dilute aqueous solution (414 nm), which is much larger than the shift between the crystalline (aggregation) state and the solution state of organic molecules. [ 4 ] Besides this case, the fl uorescence of solution changes from blue to yellow-green followed by the increase of the solute concentration, and approaches that of powder when the concentration is up to 30 mg mL −1 (Figure 2 c). With the above phenomena and according to the spectral overlap between absorption and emission, which is usually described in terms of the Förster distance ( R 0 ) for convenience (Figure 2 d), it is believed that the extra-large red-shift are ascribed to RET or re-absorption, which always occurs in small interparticle distance less than R 0 .…”

“…[ 1 ] However, CDs always undergo self-quenching in the solid state, like organic molecules ascribed to excessive resonance energy transfer (RET) or direct π-π interactions. [2][3][4] Moreover, solid CDs are usually diffi cult to obtain because of hydroscopicity. These drawbacks must limit the wide use of CDs, because numerous applications, e.g., optoelectronic devices and sensors, generally require photoluminescent materials emitting in the solid state, [ 2,5,6 ] while so far, nearly all CDs-related research has focused on fl uorescence from aqueous solution, which is insuffi cient to support these applications.…”

“…interaction, a major energy-transfer process responsible for self-quenching, [2][3][4] can be effectively avoided by taking advantage of it. [ 21 ] Furthermore, the emission maximum (525 nm) of the powder has remarkable red-shift of 111 nm from that of dilute aqueous solution (414 nm), which is much larger than the shift between the crystalline (aggregation) state and the solution state of organic molecules.…”

Full‐Color Emission Polymer Carbon Dots with Quench‐Resistant Solid‐State Fluorescence

“…Since small molecular dyes exhibited fluorescence due to typical conjugated π‐domains fluorophores, their fluorescence suffered from π–π interaction, a major energy‐transfer process that may cause self‐quenching in solid state 24, 25. Unlike them, it is sub‐fluorophores in SSFPCDs that is the key of fluorescence, which do not undergo the π–π interaction process and thus prevent SSFPCDs with aggregation state from quenching in some extent.…”

Solid-emissive fluorophores constructed by a non-planar heteropolycyclic structure with bulky substituents: synthesis and X-ray crystal structures

“…In this paper, we report a molecular design and the convenient synthesis of novel solid-emissive indeno [1, b]benzo [4,5-e]pyran-11-one-type fluorophore (3a-3c) 7 constructed by a non-planar structure with sterical hindered substituents. To elucidate the differences between the photophysical properties in solution and in the solid state, we have performed the time-resolved fluorescence spectroscopic 60 measurement, the semi-empirical molecular orbital calculations (AM1 and INDO/S), and the X-ray crystallographic analysis of 3a-3c.…”