Dynamic Fluorescence Sensing of Bromide Ions by Photochromic Bi(III)-Coordination Polymers Based on a Ligand Integrated by Naphthalene Diimides and Pyridinium in Solution and Films.

Bismuth(III)-based complexes have garnered increasing attention in fluorescence sensing due to their environmentally friendly and sustainable characteristics. A Bismuth(III) coordination polymer (CP),1-Cl based on a naphthalene diimides(NDI)-pyridinium is synthesized by an in situ reaction method. Notable for its sensitivity to visible light, 1-Cl shows excellent photochromic properties, and the integration of NDI and pyridinium in one ligand makes photogenerated radicals more stable.

Conformation- and Coordination Mode-Dependent Stimuli-Responsive Salicylaldehyde Hydrazone Zn(II) Complexes.

Luminescent Zn(II) complexes that respond to external stimuli are of wide interest due to their potential applications. Schiff base with O,N,O-hydrazone shows excellent luminescence properties with multi-coordination sites for different coordination modes. In this work, three salicylaldehyde hydrazone Zn(II) complexes (, , ) were synthesized and their stimuli-responsive behaviors in different states were explored.

Three-Dimensional Viologen-Based Lanthanide-Organic Frameworks: Photochromism and Fluorescence Detection of Quinolone Antibiotics.

Quinolone antibiotic residues, norfloxacin (NORF) and ciprofloxacin (CIP), have attracted more attention due to their frequent detection in surface water and food field, which seriously threaten the health of animals and humans. Rapid and efficient detection of NORF and CIP is critical for environmental testing and ecosystems. Herein, two novel isostructural viologen-functionalized Ln(III) complexes [LnL(IPA)] (Ln = Eu, ; Tb, ; L = ,'-bis (2-carboxyethyl)-4,4'-bipyridridylium dichloride, HIPA = isophthalic acid) with a three-dimensional structure have been synthesized solvothermally.

Enhancement of Long-Lived Persistent Room-Temperature Phosphorescence and Anion Exchange with I and SCN via Metal-Organic Hybrid Formation.

An in-depth understanding of structure-property relationships and the construction of multifunctional stimuli-responsive materials are still difficult challenges. Herein, we discovered a 4,4'-bipyridinium derivative with both photochromism and dynamic afterglow at 77 K for the first time. A one-dimensional (1D) Cd(II) coordination polymer () assembled by only a 4,4'-bipyridinium derivative and cadmium chloride showed photochromism, room-temperature phosphorescence (RTP), and electrochromism.

Multistimuli-responsive materials based on a zinc(II) complex with high-contrast and multicolor switching.

The development of stimulus-responsive luminescent materials, especially those based on a single compound exhibiting multicolor and high-contrast (Δ ≥ 100 nm) chromic properties, is a critical challenge. In this work, we synthesized and characterized a zinc(II) complex (1). As expected, 1 displays aggregation-induced emission enhancement (AIEE) in THF/HO mixtures, and remarkable multicolor switching under external stimuli in the solid state.

Multistimuli-Responsive Materials Based on Zn(II)-Viologen Coordination Polymers and Their Applications in Inkless Print and Anticounterfeiting.

Recently, stimuli-responsive materials have attracted great attention, while most of them respond to single or two stimuli. Thus, it is essential to design multifunctional stimuli-responsive materials and develop their applications. The strategy that constructing high-dimensional coordination polymers facilitates the application scope of a viologen-based photochromic system is put forward and confirmed for the first time.

Multistimulus Response of Two Tautomeric Zn(II) Complexes and Their White-Light Emission Based on Different Mechanisms.

A triphenylamine (TPA)-based 2-quinazoline Zn(II) complex () exhibiting dual fluorescence and phosphorescence emission in the solid state was designed and prepared. It possesses mechanochromic luminescence and thermochromic luminescence properties. In the solid state, the white afterglow luminescence could be observed at 77 K (CIE: 0.

Multi-stimuli-responsive Zn(II)-Schiff base complexes adjusted by rotatable aromatic rings.

Multifunctional luminescent materials have attracted intensive interest. However, the mechanisms behind them are still to be explored. In this work, three Zn(II) complexes based on Schiff bases (HL and HL) that contain rotatable aromatic rings were designed and prepared.

A Multistimuli Responsive Crystalline Cd(II)-Viologen Coordination Polymer with Single-Crystal-Single-Crystal Transformation.

It is necessary to develop stable and fast multistimuli responsive materials due to the growing demand in our daily life. In this work, a new viologen-based Cd-complex () exhibits multiple thermochromic and photochromic behaviors through 10 states with 7 colors. For example, it responds to both Cu Kα/Mo Kα X-ray sources and UV dual light quickly with a color change from colorless to dark blue () (Cu Kα/Mo Kα X-ray sources) and cyan () (UV light), respectively.

Multistimuli Responsive Solid-State Emission of a Zinc(II) Complex with Multicolour Switching.

The development of smart luminescent materials, especially those stimulus-responsive fluorescent materials that can switch between different colors repeatedly under external stimulation based on a single molecule, is of great significance but a challenge. In this work, a novel zinc(II)-Schiff base complex (ZnL) was obtained and characterized. Upon exposure to the HCl and NH vapors, it displayed remarkable tricolor acidochromic behavior with high contrast and rapid response under the ambient light as well as UV light (365 nm).

ESIPT-AIE active Schiff base based on 2-(2'-hydroxyphenyl)benzo-thiazole applied as multi-functional fluorescent chemosensors.

Three AIE (aggregation-induced emission)-ESIPT (excited-state intramolecular proton transfer) active 2-(2-hydroxyphenyl)benzothiazole derivatives, HL, HL and HL with one, two and three rotatable phenyl groups, were obtained and characterized. Their AIE properties in THF/HEPES solution were investigated in detail. HL shows the best AIE performance with 71-fold fluorescence enhancement, while HL only shows a 9-fold enhancement.

A multi-binding site hydrazone-based chemosensor for Zn(ii) and Cd(ii): a new strategy for the detection of metal ions in aqueous media based on aggregation-induced emission.

A multi-binding site chemosensor, N-(3-methoxy-2-hydroxybenzylidene)-3-hydroxy-2-naphthahydrazone (HL), with excited-state intramolecular proton transfer (ESIPT) behaviour was prepared and characterized. It possesses no aggregation-induced emission (AIE) characteristics but can detect Cd and Zn ions selectively in the "off-on" mode based on the AIE of their complexes in the media of THF/HEPES and THF/HO, respectively, which will provide a new strategy for target detection based on AIE. The detection limits of Zn and Cd were 9.

Grinding-Triggered Single Crystal-to-Single Crystal Transformation of a Zinc(II) Complex: Mechanochromic Luminescence and Aggregation-Induced Emission Properties.

We first report single crystal X-ray analysis of ground crystals of mechanochromic luminescence (MCL) that shows single crystal-to-single crystal transformation (SCSCT). Single crystals of [ZnL] (1-SG, HL = 2-[[[4-(2-benzoxazolyl)phenyl]imino]-methyl]-5-(diethylamino)-phenol) were obtained upon slight grinding of single crystals of [ZnL]·0.5CHOH (1), both of which were characterized by single crystal X-ray diffraction.

Photophysical properties of a D-π-A Schiff base and its applications in the detection of metal ions.

A D-π-A Schiff-base compound, 2-amino-3({[4-(diethylamino)-2-hydroxylphenyl]methylene}amino)-but-2-enedinitrile (H2L), was prepared using diaminomaleonitrile and 4-(N,N-diethylamino)salicylaldehyde. Compared with H2L at 293 K, a low temperature of 100 K makes the parallel aromatics in H2L come closer and fluorescence emission becomes weaker because of π-π interaction-caused quenching. After grinding the crystals of H2L, the colour changed from dark brown-red to yellow under room light and the fluorescence emission enhanced about 9-fold due to the damage of the intermolecular hydrogen bonds, leading to a decrease of non-radiative transition.

Coordination-Directed Stacking and Aggregation-Induced Emission Enhancement of the Zn(II) Schiff Base Complex.

2-(Trityliminomethyl)-quinolin-8-ol (HL) and its Zn(II) complex were synthesized and characterized by single-crystal X-ray diffraction. HL is an unsymmetrical molecule and coordinated with Zn(II) ion to form ZnL in the antiparallel-mode arrangement via Zn-O (hydroxyl group) and Zn-N (quinoline ring) of HL. A high degree of ZnL molecules ordering stacking is formed by the coordination bonds and intermolecular π-π interactions, in which head-to-tail arrangement (J-mode stacking) for L is found.

Hydrogen bond-assisted aggregation-induced emission and application in the detection of the Zn(ii) ion.

The compounds of 3-aminopyridine-2-carboxylic acid with K(+) (1) and Zn(2+) (2) were found to be AIE-active. The AIE behaviours could be attributed to the restriction of intramolecular rotation (RIR) and vibration (RIV) via hydrogen bonds, resulting in rigidity enhancement of the molecules. An AIE-based fluorescence turn on chemosensor for the Zn(ii) ion has been developed in aqueous media with high selectivity and sensitivity.

A microscale multi-functional metal-organic framework as a fluorescence chemosensor for Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde.

A microscale metal-organic framework [Eu(atpt)1.5(phen)(H2O)]n (H2atpt=2-aminoterephthalic acid, phen=1,10-phenanthroline) (Eu-MOF) was synthesized and characterized by elemental analysis, luminescence spectrum, powder X-ray diffraction, dynamic light scattering and scanning electron microscope. The fluorescence response of Eu-MOF to metal ions and aldehydes showed that Eu-MOF is highly selective to Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde (2-OH-NA).

Metal ion-assisted ring-opening of a quinazoline-based chemosensor: detection of copper(II) in aqueous media.

A quinazoline-based fluorescence chemosensor, 6-phenol-2-yl-(5,6-dihydrobenzimidazo[1,2-c])quinazoline (HL), for highly selective recognition of Cu(II) in aqueous media was synthesized. The detection limit was of the order of 10(-6) M. The crystal structures of the Cu(II) and Cd(II) complexes showed that HL changed to a Schiff base when it reacts with metal salts and that the metal ions coordinate with two nitrogen atoms and one hydroxyl oxygen atom from the Schiff base.

Three-dimensional frameworks based on dodecanuclear Dy-hydroxo wheel cluster with slow relaxation of magnetization.

Two new heterometallic coordination polymers, [Na4Ln12(stp)8(OH)16(H2O)12]·10H2O [Ln = Dy (1) and Ho (2)], have been prepared from monosodium 2-sulfoterephthalate (NaH2stp), dysprosium acetate, or holmium acetate. They are isostructural, possessing a [Ln12(μ3-OH)16](20+) wheel-cluster core based on four vertex-sharing cubane-like [Ln4(μ3-OH)4](8+) units. The Ln12 cores are linked by stp ligands into a three-dimensional (3D) architecture.

Intensive upconversion luminescence of Na-codoped rare-earth oxides with a novel RE-Na heterometallic complex as precursor.

Four novel heterometallic RE-Na-organic frameworks, [(RE)Na3(PZTC)2(H2O)4]·2H2O (RE = Yb (1), Ho (2), Er (3), Y (4); PZTC = pyrazine-2,3,5-tricarboxylate), were synthesized via solvothermal reactions and characterized by IR, elemental analysis, and single-crystal X-ray diffraction. The results show that the four complexes are isostructural. In the frameworks, the trinuclear Na cluster and RE ion acting as nodes are bridged by the multifunctional PZTC ligand to give a 3-D framework.

A highly selective and sensitive Zn(II) complex-based chemosensor for sequential recognition of Cu(II) and cyanide.

Two new Schiff base complexes, [ZnL(Ac)]2 (1) and [CuLCl]·H2O (2) (HL = 2-(2'-hydroxynaphthylmethylene)aminophenylbenzimidazole, Ac = acetate) were synthesized by a one-pot reaction and characterized by elemental analyses, IR and single-crystal X-ray diffraction. Fluorescence of complex 1 showed "on-off-on" switching when Cu(2+) and cyanide were sequentially detected. This phenomenon was investigated by UV-Vis absorption, fluorescence and ESI-MS spectra, and theoretical calculations to explain the response.

A tetrazole-based fluorescence "turn-on" sensor for Al(III) and Zn(II) ions and its application in bioimaging.

A tetrazole derivative 1-[(1H-tetrazol-5-ylimino)methyl]naphthalen-2-ol (H2L) as a fluorescent chemosensor for Al(3+) in DMSO and Zn(2+) in DMF was designed and synthesized. From (1)H NMR data, the Job plot and the ESI-MS spectrum, 1 : 1 stoichiometric complexation between H2L and Al(3+)/Zn(2+) was found in DMSO and DMF, respectively. The theoretical calculations at the level of B3LYP/6-311G** for the ground state and TD-B3LYP/6-311G** for the excited state revealed the sensing mechanism is the inhibition of excited state intramolecular proton transfer (ESIPT).

A highly selective chemosensor for Al(III) and Zn(II) and its coordination with metal ions.

This paper reports a fluorescence chemosensor, N-(benzimidazol-2-yl)salicylaldimine (H2L), for Zn(II) and Al(III) ions. H2L has high selectivity for Al(III) in dimethyl sulfoxide (DMSO) and for Zn(II) in N,N-dimethylformamide (DMF). In methanol, Zn(II) and Al(III) could also be distinguished by H2L with different excitation wavelengths.

A highly selective fluorescent chemosensor for Al(III) ion and fluorescent species formed in the solution.

A chemosensor for the Al(3+) ion, 1-[(3-hydroxypyridin-2-ylamino)methylene]naphthalen-2(1H)-one (H2L), based on inhibited excited-state intramolecular proton transfer was synthesized. The experimental and theoretical calculations at B3LYP+PCM/6-31G(d) revealed that Al(3+) and H2L form a 1:1 complex, [AlL(OH)(H2O)]2, in dimethyl sulfoxide that exhibits two remarkably enhanced fluorescent emissions at 523 and 553 nm. It is confirmed that H2L could be used to detect Al(3+) ions in cells by bioimaging.