Fluorescent single crystals that respond to multiple external stimuli are of great interest in molecular machines, sensors, and displays. The integration of photo‐ or acid‐induced fluorescence ...enhancement and bending in one organic crystal, however, has not been reported yet. Herein, we report the interesting plastic photomechanical bending and switching on of the fluorescence of an azine crystal in a single‐crystal transformation, due to extended π‐conjugation and molecular slippage. Moreover, the fluorescent plastic bending driven by multiple volatile acid vapors was firstly observed, and attributed to the synergistic effect of push–pull electronic structure and hydrogen bonding. The single crystal also shows high elasticity under external force. In addition, reversible fluorescence switching can be triggered by grinding and solvent fuming, as well as by the adsorption and desorption of HCl vapor. The integration of plastic, elastic bending and switch‐on fluorescence into one single crystal provides a new strategy for next‐generation smart materials.
A slender single crystal based on azine exhibits controllable plastic bending and fluorescence enhancement upon UV light irradiation or acid vapor fuming, as well as elastic bending under external force and mechanoresponsive fluorescence. This is the first smart single crystal exhibiting fluorescence lit up upon bending triggered by UV light irradiation and exposure to acid.
A new rhodamine spirolactam derivative as a naked-eye and fluorescent chemosensor (
1
) for copper(II) with excellent antijamming capability was synthesized by using 1-(pyrazin-2-yl)hydrazine and ...rhodamine B as starting materials. Introducing of pyrazinyl hydrazine increased its solubility in water. In the presence of Cu
2+
, the solution color of
1
changed from colorless to amaranth. At the same time, a strong fluorescence at 575 nm was turned on. The absolute fluorescence quantum yield of
1
without or with two equivalents of Cu
2+
was increased from 0.010 to 0.298. The limit of detection was determined to be 89.9 nM. The stoichiometry between
1
and Cu
2+
was determined 1:2 through job’s plot. Based on the results of mass spectra, absorption and fluorescence spectra, as well as the theoretical calculations, a ring-opening process of the spirolactam form of
1
induced by Cu
2+
and further hydrolysis was proposed. The colorimetric test strips were made for
1
to recognize Cu
2+
quickly and conveniently. Furthermore,
1
was applied to image Cu
2+
in HepG2 living cells.
Aggregation-induced emission (AIE) materials have drawn great attention for their wide applications as optical materials. The applications of AIE materials, however, are restricted by the complicated ...syntheses, hydrophobic properties and short emission wavelengths. Herein, an imidazolium based hydrazone (
E
)-1-(4-methoxyphenyl)-2-((1-methyl-1H-imidazol-2-yl)methylene)hydrazine hydrochloride (
1
) and a pyridinium based hydrazone (
E)-
1-(4-methoxyphenyl)-2-(pyridin-4-ylmethylene)hydrazine hydrochloride (
2
) have been synthesized. Notably,
1
and
2
in crystals show distinct green and near-infrared (NIR) fluorescence, with emission peaks at 530 and 688 nm, and Stokes shifts of 176 and 308 nm, respectively. After grinding the crystals to powder, the absolute fluorescence quantum yield (
Φ
F
) of
1
is increased from 4.2% to 10.6%, and the
Φ
F
of
2
is increased from 0.2% to 0.7%. X-ray crystallography studies together with theoretical calculations indicate that the enhanced emission of
1
arises from hydrogen bonding induced rigid network, and the fluorescence in the NIR region and large Stokes shift of
2
are attributed to its twisted molecular structure and strong push–pull effect.
Graphical Abstract
A new fluorescent resonance energy transfer (FRET) based fluorescent probe (compound 1) containing a dansyl unit as a donor and rhodamine 101 as an acceptor was developed to detect Fe3+ from other ...transition metal ions through ratiometric sensing in organic-aqueous solutions. Fe3+ induced a ring-opening reaction of the spirolactam rhodamine moiety of 1 resulting in the formation of a fluorescent derivative that can serve as the FRET acceptor. Ratiometric sensing of Fe3+ was accomplished by plotting the fluorescence intensity ratio at 605nm and 515 nm versus ferric ion concentration. The probe displayed a linear response to Fe3+ in the range of 5.5–25μM with a detection limit of 0.64μM. A 1:1 stoichiometry for the 1–Fe3+ complex was formed with an association constant of 1.74×104M−1. The probe also exhibited a large Stokes shift (225nm) which can eliminate backscattering effects of excitation light.
•A new colorimetric and fluorescent “off–on” chemosensor for Fe3+ was synthesized.•It can respond to Fe3+ in the red spectral region based on a FRET mechanism.•Its ratiometric sensing for Fe3+ can be accomplished with a signal to noise ratio of 214.•The large Stokes shift (225nm) can rule out the excitation backscattering effects.
A new bis-spirocyclic rhodamine B derivative was developed as a near-infrared colorimetric and “turn-on” fluorometric chemodosimeter (
1
) with a large Stokes shift (70 nm) for Cu
2+
. In response to ...Cu
2+
, the solution of
1
displayed major absorption at 700 nm, from colorless to blue within ten seconds. At the same time, emissions at 580 nm (excitation at 520 nm) and at 770 nm (excitation at 650 nm) were turned on. Good linear relationships between absorbance at 700 nm, fluorescence at 580 and 770 nm and concentration of Cu
2+
in wide ranges were obtained in both colorimetric and fluorometric analyses, with the detection limits of 0.57 μM, 9 nM and 28 nM, respectively. Irreversible ring-opening processes of
1
coordinated with Cu
2+
, followed by hydrolysis as well as acylated reaction were proposed. Furthermore,
1
was applied to image Cu
2+
in HepG2 living cells and within the mitochondria of the cells in the roots of
paulownia
sprouts.
A newly developed acylhydrazone derivative (compound
1
) displayed solvatochromic fluorescence effect with dominant fluorescence from its keto form in most solvents, fluorescence from its phenolic ...anion in DMF, and concentration-dependent emission intensities for both enol and keto forms in toluene. The aggregation-induced emission enhancement (AIEE) properties of
1
were observed in THF − H
2
O and DMF − H
2
O. Red fluorescence in the root cells of
paulownia
sprouts was observed for application of
1
as a fluorescence marker. Notably, strong fluorescence centered at 602 nm with a large stokes shift (232 nm) and an absolute quantum yield of 22% for
1
was obtained in crystals.
X
-ray analysis indicates that the fluorescence of crystal
1
is caused by intramolecular hydrogen bonding-induced limitation in
C
=
N
isomerization and weak intermolecular interactions. Furthermore, compound
1
exhibited good colorimetric/ratiometric sensing properties for quantitative detection of acetate and dihydrogen phosphate anions with detection limits of 250 nM and 170 nM, respectively, and blue-shifted amplified fluorescence response with detection limits of 45 nM and 62 nM, respectively. Based on
1
H NMR analyses, intermolecular hydrogen bonding/deprotonation interactions of
1
with these anions and inhibiting ESIPT process were proposed for anions sensing.
Biothiols of cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen polysulfides (H
2
S
n
,
n
> 1) play vital roles in physiological and pathological processes. In this manuscript, a ...fluorescent probe (compound
1
) for simultaneous detection and discrimination of Cys/Hcy, GSH and H
2
S
n
was developed, employing fluorophore of 1-(benzodthiazol-2-yl)naphthalen-2-oxy linked with 7-nitrobenzo-2-oxa-1,3-diazole (NBD) as a response unit and a quencher. Compound
1
exhibited different ratiometric colorimetric responses toward GSH at 430 nm and 375 nm from Cys/Hcy at 480 nm and 375 nm, while it displayed a different colorimetric response at 561 nm toward H
2
S
n
. Meanwhile it could act as a naked-eye probe toward GSH, Cys/Hcy and H
2
S
n
with corresponding solution color of light yellow, orange and purple, respectively. Upon excitation at 370 nm, compound
1
responded to all these biothiols with 'turn-on' blue fluorescence, whereas upon excitation at 470 nm, it could respond to Cys/Hcy with 'turn-on' green fluorescence. Data of mass spectra, lifetimes and
1
H NMR spectra interpreted the aromatic nucleophilic substitutions of compound
1
by GSH, Cys/Hcy and H
2
S
n
to produce fluorophore1-(benzodthiazol-2-yl)naphthalen-2-ol (compound
2
) and corresponding NBD derivatives which could be discriminated through their absorption and fluorescence signals as well as solution colors. Furthermore, compound
1
was applied to image Cys/Hcy and H
2
S
n
/GSH in 786-O cells.
A new rhodamine-based derivative (1) is designed as a colorimetric and fluorescent “off–on” chemosensor for Cr3+ in aqueous solutions. Its sensing behaviors toward metal ions in neutral aqueous ...solutions were investigated by UV–vis absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 581nm and an amplified fluorescence at 600nm toward Cr3+ in a preferential, sensitive and rapid manner. Upon addition of Cr3+, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to form a ring-opened amide (purple red color and fluorescent) and a 1:1 stoichiometry for the 1-Cr3+ complex was formed with an association constant of 5.75×104M−1. The quantification of Cr3+ by 1 using a fluorescence spectroscopy method was satisfactory in the linear working range below 4μM, with a detection limit of 3.75×10–9M for Cr3+ and good tolerance of other metal ions. The chemosensor has been used for imaging of Cr3+ in living Hela cells with satisfying results.
•A new colorimetric and fluorescent “off–on” chemosensor for Cr3+ was synthesized.•It can respond to Cr3+ in aqueous solutions in the red spectral region.•Its sensing behavior is reversible, selective, sensitive and rapid.•The chemosensor has been used for imaging of Cr3+ in living Hela cells.
Fluorescent single crystals that respond to multiple external stimuli are of great interest in molecular machines, sensors, and displays. The integration of photo‐ or acid‐induced fluorescence ...enhancement and bending in one organic crystal, however, has not been reported yet. Herein, we report the interesting plastic photomechanical bending and switching on of the fluorescence of an azine crystal in a single‐crystal transformation, due to extended π‐conjugation and molecular slippage. Moreover, the fluorescent plastic bending driven by multiple volatile acid vapors was firstly observed, and attributed to the synergistic effect of push–pull electronic structure and hydrogen bonding. The single crystal also shows high elasticity under external force. In addition, reversible fluorescence switching can be triggered by grinding and solvent fuming, as well as by the adsorption and desorption of HCl vapor. The integration of plastic, elastic bending and switch‐on fluorescence into one single crystal provides a new strategy for next‐generation smart materials.
A slender single crystal based on azine exhibits controllable plastic bending and fluorescence enhancement upon UV light irradiation or acid vapor fuming, as well as elastic bending under external force and mechanoresponsive fluorescence. This is the first smart single crystal exhibiting fluorescence lit up upon bending triggered by UV light irradiation and exposure to acid.
