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A microscale metal-organic framework [Eu(atpt) 1.5 (phen)(H 2 O)] n (H 2 atpt = 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). Eu-MOF could be utilized as a multi-functional fluorescence chemosensor for Fe(III), Al(III) and 2-hydroxy-1-naphthaldehyde (2-OH-NA). The detection limit of Fe(III), Al(III) and 2-OH-NA was 45, 10 and 36 μM, respectively. The corresponding sensing mechanisms were explored. [ABSTRACT FROM AUTHOR]

An acylhydrazone-based derivative, 3-hydroxy-N'-(2-hydroxy-1-naphthalene methylene)-2-naphthalene hydrazide (H 3 L), was synthesized and characterized by elemental analyses, IR, 1 H NMR and mass spectrum. H 3 L is non-fluorescent in DMSO. But the fluorescence emission is enhanced obviously via the formation of aggregates in DMSO/H 2 O mixture. The formed aggregates were confirmed by DLS and SEM. H 3 L is an aggregation-induced emission (AIE)-active fluorophore. H 3 L can act as a fluorescence sensor for Al 3+ and Zn 2+ in DMSO/H 2 O (v/v, 9/1) and THF/H 2 O (v/v, 999/1), respectively. And H 3 L is also a naked-eye probe for Fe 3+ in DMSO/H 2 O (v/v, 9/1). The binding stoichiometry of H 3 L to both Al 3+ and Zn 2+ is 1:1, but that to Fe 3+ is 2:1. The metal complex species formed in the detection procedure are deduced by Job plot, spectroscopic titrations and ESI–MS to be [AlL(DMSO) 2 ], [Zn(HL)(H 2 O)] and [Fe(HL)(H 2 L)]. The detection limit is as low as 3.66 μM for Al 3+ , 1.01 μM for Zn 2+ and 0.34 μM for Fe 3+ . H 3 L can also be used to detect intracellular Al 3+ and Zn 2+ . The sensing event might be attributed to a combinational effect of excited state intramolecular proton transfer (ESIPT) and chelation-enhanced fluorescence (CHEF) mechanism for selective detection of Al 3+ and Zn 2+ ions, and ligand-metal charge transfer (LMCT) mechanism for Fe 3+ ion. [ABSTRACT FROM AUTHOR]

A new fluorescent sensor 6-(2,3-dihydroxyphenyl)-5,6-dihydrobenzoimidazo[1,2-c] quinazoline (H 2 L) and the Zn(II) complex [Zn 2 L 1 2 ]∙C 2 H 5 OH (H 2 L 1 = 3-{[2-(1 H -benzoimidazol-2-yl)-phenylimino]-methyl}-benzene-1,2-diol) ( 1 ) were synthesized and characterized by single-crystal X-ray diffraction. H 2 L can be used to recognize Cu 2+ in aqueous media as an on–off fluorescent sensor, forming the Cu(II) Schiff-base complex (CuL 1 ). Furthermore, CuL 1 can serve as an off–on fluorescent sensor to detect histidine (His) via the ligand displacement approach. The sequential detection of Cu(II) and histidine shows on–off–on phenomenon. The crystal structure of the dinuclear Zn(II) complex indicates that the coordination of H 2 L with Zn(II) promotes C N bond breakage, resulting in the quinazoline ring-opening of H 2 L to form the Zn(II) Schiff-base complex ( 1 ). The experimental results proved that H + can also assist the ring-opening of H 2 L to form a Schiff base, H 2 L 1 . H 2 L is stable in neutral and weak basic solutions. This is further confirmed by the theoretical calculations. The cell imaging studies indicated that H 2 L and CuL 1 can be used to detect the intracellular Cu 2+ ion and His under physiological conditions, respectively. CuL 1 can also be used to determine His in urine. [ABSTRACT FROM AUTHOR]

The compounds of 3-aminopyridine-2-carboxylic acid with K+ (1) and Zn2+ (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. [ABSTRACT FROM AUTHOR]

A chemosensor 3-[(2-hydroxybenzylidene)-amino]-1H-pyridin-2-one (HL) for multi-ions was synthesized and characterized by single-crystal X-ray diffraction. HL is a turn-on fluorescence chemosensor for Al 3+ , F − , and CN − ions in DMSO. F − and CN − anions could be further distinguished by the ratiometric absorption spectrometry method. Job plot and 1 H NMR data showed that the binding stoichiometries of HL with Al 3+ , F − , or CN − all were 1:1. Further observations of 1 H NMR titration and ESI-MS showed that the possible fluorescent species of Al 3+ with HL was [AlL(OH)(DMSO) 2 ] + in DMSO. The spectroscopic observations of the Al(III) complex showed that the two oxygen atoms and one imine nitrogen atom of HL were coordinated to the Al(III) ion. While the crystal structure of the Ni(II)-L complex confirmed the tridentate coordination mode of HL in the complexes. The experimental results revealed that HL and F − ion formed hydrogen bond in DMSO, while CN − attacked the carbon atom at –C N of HL to undergo a nucleophilic addition. The theoretical calculations confirmed that HL showed very weak fluorescence because of the excited-state intramolecular proton transfer (ESIPT). The turn-on sensing of HL to Al 3+ , F − , and CN − ions arose from the inhibition of ESIPT. MTT tests showed that HL was low toxic to cells. Also, HL could probe intracellular Al 3+ and F − ions by bioimaging. [ABSTRACT FROM AUTHOR]

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. The theoretical calculations at B3LYP-SCRF/6-31G(d) confirmed that it is the Cu(ii) ion that assisted the ring-opening of the quinazoline derivative, forming a Cu(ii) Schiff base complex during the detection. LMCT leads to the disappearance of fluorescence. A cell imaging study indicated that HL could be used to detect the intracellular Cu2+ ion. [ABSTRACT FROM AUTHOR]

Abstract: A new Schiff base 1-[(1H-1,2,4-triazole-3-ylimino)-methyl]-naphthalene-2-ol (H2L) exhibiting high selectivity for Al3+ ion over other metal ions, such as Li+, Na+, K+, Ca2+, Mg2+, Cu2+, Co2+, Mn2+, Ni2+, Zn2+, Cd2+, Pb2+, Fe3+, and Cr3+ was prepared, and it is sensitive for Al3+ with the detection limit reaching 0.69μM in DMF. Upon addition of Al3+, the significant enhancement (32-fold) of fluorescence intensity for H2L at 466nm is ascribed to the formation of a 1:1 complex between Al3+ and H2L, which is denoted as the chelation-enhanced fluorescence (CHEF) effect. The confocal fluorescence microscopy experiments demonstrate that H2L could be used as a fluorescent probe for Al3+ in living cells. [Copyright &y& Elsevier]