RESUMO
A cerium-based metal-organic tetrahedron has been developed as a highly selective and sensitive fluorescence sensor for the recognition of 4-amino-2,6-dinitrotoluene (4-ADNT). The redox-active tetrahedron could encapsulate 4-ADNT through weak interaction and spatial stereoselectivity, resulting in an enhanced fluorescence. The tetrahedral sensor Ce-ZPS is capable of realizing fluorescent sensing in urine and in cells and thus has the potential to detect 4-ADNT in organisms.
RESUMO
Understanding the effects of intermolecular interactions on metal-to-metal charge transfer (MMCT) is crucial to develop molecular devices by grafting MMCT-based molecular arrays. Herein, we report a series of solvent-free {Fe2 Co2 } compounds sharing the same cationic tetranuclear {[Fe(PzTp)(CN)3 ]2 [Co(dpq)2 ]2 }2+ (PzTp- =tetrakis(pyrazolyl)borate, dpq=dipyrido[3,2-d:2',3'-f]quinoxaline) square units but having anions with different size, including BF4 - , PF6 - , OTf- , and [Fe(PzTp)(CN)3 ]- . Intermolecular πâ â â π interactions between dpq ligands, which coordinate to cobalt ions in the {[Fe(PzTp)(CN)3 ]2 [Co(dpq)2 ]2 }2+ units, can be modulated by introducing different counterions, regulating the distortion of the CoN6 octahedron and ligand field around the cobalt ions. This change results in different MMCT behavior. Computational analyzes reveal the substantial role of the intermolecular interactions tuned by the presence of different counteranions on the MMCT behavior.
RESUMO
Magnetic and dielectric properties have been tuned simultaneously by external stimuli with rapid and sensitive response, which is crucial to monitor the magnetic state via capacitive measurement. Herein, positive charged FeII ions were linked via negative charged [(Tp)FeIII (CN)3 ]- (Tp=hydrotris(pyrazolyl)borate) units to form a neutral chain. The spin-crossover (SCO) on FeII sites could be sensitively triggered via thermal treatment, light irradiation, and pressure. SCO switched the spin state of the FeII ions and antiferromagnetic interactions between FeIII and FeII ions, resulting in significant change in magnetization. Moreover, SCO induced rotation of negative charged [(Tp)FeIII (CN)3 ]- units, generating dielectric anomaly due to geometric change of charges distribution. This work provides a rational way to manipulate simultaneous variations in magnetic and dielectric properties utilizing SCO as an actuator to tune spin arrangement, magnetic coupling, and charge distribution.
RESUMO
It is a challenge to reversibly switch both magnetism and polarity using light irradiation. Herein we report a linear Fe2 Co complex, whereby interconversion between FeIIILS (µ-CN)CoIIHS (µ-NC)FeIIILS (LS=low-spin, HS=high-spin) and FeIIILS (µ-CN)CoIIILS (µ-NC)FeIILS linkages could be achieved upon heating and cooling, or alternating laser irradiation at 808 and 532â nm. The electron spin arrangement and charge distribution were simultaneously tuned accompanying bidirectional metal-to-metal charge transfer, providing switchable polarity and magnetism in the complex.
RESUMO
Multiemissive sensors are being actively pursued, because of their ratiometric luminescent detection capabilities, which demonstrates better sensitivity and selectivity than conventional single-emission sensors. Herein, we present a trichromatic white-light-emitting metal-organic framework (MOF) composite (Z3) by simultaneously incorporating red/green-emitting Pt/Ru complex cations into porous blue-emitting bio-MOF-1 through post-synthetic modification. With the help of a three-dimensional (3-D) dual-ratiometric luminescence recognition method, and unique turn-on responses of the red emission toward amine compounds (ACs), including NH3 and aliphatic amines, via confinement-induced luminescence enhancement effect, Z3 can work as a dual-ratiometric luminescent sensor for discrimination of 7 out of 11 AC vapors. This work not only provides a new AC sensing mechanism (confinement effect) that can induce a "turn-on" response but also proves that the accuracy and selectivity of composite sensor can be greatly improved through the combination of 3-D recognition method and the confinement effect. Thus, it open up fresh opportunities to develop composite sensors with excellent sensing and differentiating ability.
RESUMO
How low can you go? An Fe(II) (4) square was prepared by self-assembly and exhibits both thermally induced and photoinduced spin crossover from a system with four high-spin (HS) centers to one with two high-spin and two low-spin (LS) centers. The spin-crossover sites are located on the same side of the square, and the spin transition and magnetic interactions (see picture) are synergistically coupled.
RESUMO
Two bilayered metal-organic frameworks with nanoporous channels were synthesized at different ligand-to-metal ratios, which demonstrated an interesting crystal-to-crystal transformation property and a special fluorescent response to the different guest molecules included.
Assuntos
Metais/química , Nanoestruturas/química , Compostos Orgânicos/química , Compostos Organometálicos/síntese química , Compostos Orgânicos de Estanho/química , Cristalografia por Raios X , Fluorescência , Ligantes , Porosidade , Solventes/química , Espectrometria de FluorescênciaRESUMO
Molecular materials possessing phototunable fluorescence properties have attracted great interest owing to their potential applications in optical switches and storage. However, most fluorescence modulation is realized through light-responsive structural isomerization in solution. It is a formidable challenge to achieve phototunable fluorescence emission with high fatigue resistance and a fast response rate in the solid state for the development of devices. Here, a mononuclear compound was constructed via the coordination of fluorophores with FeII ions, whose electronic configuration changed from low spin to high spin upon light irradiation. The photoinduced spin crossover of FeII ions was accompanied by a 20% increase in the fluorescence emission intensity. A temperature-dependent spectroscopic study together with time-dependent density functional theory calculations revealed that the effective spectral overlap between the emission of the fluorophores and the absorption band of the FeII ions differed between the low spin and high spin states. The photoinduced spin crossover switched the energy transfer from the fluorophore to the FeII ion, resulting in fluorescence modulation. The presented results provide a novel approach for developing optical memory and sensors via electron rearrangement of photoinduced spin crossover.
RESUMO
The intriguing features of two-dimensional (2D) materials such as better charge carrier separation and abundant surface reaction sites endow them with potential applications as cocatalysts in photocatalysis. In this paper, a ternary 2D nickel hydroxide/sulfides nanosheet composed of Ni(OH)2, Ni3S2 and NixS6 was loaded on CdS nanospheres by a simple chemical deposition route. The composition of nickel hydroxide/sulfides was determined clearly through an overall analysis using X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Mott-Schottky, electrochemical impedance, steady-state and time-resolved photoluminescence spectroscopy were used to investigate the charge transfer process in CdS and Ni(OH)2/Ni3S2/NixS6-CdS. The results confirm that a synergistic effect of Ni(OH)2/Ni3S2/NixS6 on CdS has occurred under light irradiation, where the Ni(OH)2 and nickel sulfides act as hole storage and surface reaction sites, respectively, to promote the charge transfer on CdS. The improved charge transfer and separation efficiency as well as the increased surface reaction sites in Ni(OH)2/Ni3S2/NixS6-CdS finally result in a dramatically improved photocatalytic performance. The photocatalytic H2 evolution rate of Ni(OH)2/Ni3S2/NixS6-CdS is ca. 46 times higher than that of CdS, and the photocatalytic stability of CdS is also improved substantially under visible light irradiation.
RESUMO
Low-cost, high-performance luminescent probes with wide application potential have been actively pursued. Conventional luminescent probes, which rely on single or dual emissions responsive to analyte molecules, demonstrate limited sensitivity and selectivity because the single emissions can be easily affected by many non-analyte factors, while the dual emissions can only offer single-ratiometric luminescent sensing. Here we report a white-light-emitting trichromatic MOF composite (W2) as the first multidimensional ratiometric luminescent probe. It is facilely synthesized by simultaneously incorporating red- and green-emitting iridium and ruthenium complex cations as encapsulated luminescent modules (ELMs) into a porous blue-emitting MOF via ion exchange. Specific volatile organic solvents (VOSs) can cause VOS-dependent changes to the MOF-to-ELM energy transfer efficiencies in W2, while nitroaromatic (NAC) vapors intriguingly and unprecedentedly quench the three emissions at different rates, both of which enable visible luminescent sensing. Each VOS can be correlated to a unique combination of the two MOF-to-ELM ratios of emission-peak heights, enabling a two-dimensional (2D) code recognition. Furthermore, the time-dependent evolution of the two ratios upon exposure to selective NAC vapors can be mapped out, achieving the first 3D code recognition. Both the synthetic and sensing strategies can be further implemented to develop low-cost and effective luminescent probes.
RESUMO
A test paper for high-selectivity detecting fluoride ion in natural aqueous environments without any spectroscopic instrumentation was achieved by using Ru-bipy based quinonehydrazone as a chromo- and fluorogenic hybrid chemosensor.
RESUMO
A two-dimensional porous framework, which was formed from neutral discrete hexanuclear copper clusters via self-assembly, exhibited highly selective absorption of aromatic molecules in water with special fluorescent response.
RESUMO
The rational design of magnetic and fluorescent bifunctional materials is attracting increasing interest. In this study, two mononuclear Fe(ii) complexes, namely [Fe(L)2(NCS)2] (1) and [Fe(L)2(NCSe)2] (2) are synthesised by combining a spin-crossover unit and a fluorescent ligand (naphth-1-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine (L) to achieve bifunctionality. Single-crystal X-ray studies and magnetic measurements confirm the presence of spin crossover behaviours; these measurements agree with the results of the temperature depended Raman spectra and infrared spectra. Thermally and light-induced spin crossover is clearly observed for both complexes. The nature of the co-ligand (NCS-vs. NCSe-) shifts the transition temperature by approximately 60 K. The infrared spectra after irradiation reveal that the electronic states are ascribable to the photomagnetic effect at 10 K. Furthermore, temperature-dependent fluorescence emission spectra exhibit the coexistence of spin crossover and fluorescence for 1 and 2.
RESUMO
It is a challenge to synthesize a porous tubular coordination polymer with magnetic properties. Utilizing [Fe(II)(bipy)(CN)4](2-) (bipy = 2,2'-bipyridine) as the building block to react with Mn(2+), we successfully synthesized a cyano-bridged tubular coordination polymer with dominant ferromagnetic interactions. The inner surface of the heterometallic tube is hydrophilic, whereas the outer surface is hydrophobic. The framework is stable up to 320 °C and can adsorb N2 and CO2. The ferromagnetic interactions were transmitted via the diamagnetic N-C-Fe(II)-C-N species between Mn(2+) ions in the tube.
RESUMO
One trinuclear and two tetranuclear cyanide-bridged Fe(III)-Ni(II) complexes were synthesized via treatment of a tricyanometallate with divalent Ni salts in the presence of 1-butylimidazole, 2,2-bipyrimidyl and 1,10-phenanthroline, respectively. Magnetic property studies demonstrated that the three complexes exhibit single-molecule magnet behavior as a result of strong intracluster ferromagnetic coupling and weak intercluster magnetic interactions.
RESUMO
New lanthanide heterometallic molecular squares functionalized with Ru-bipy antenna chromophore Ru2-Ln2 exhibit sensitized near-infrared emission upon photo-excitation of the Ru-centered antenna at 420 nm.
RESUMO
A 3-D porous zeolite-like metal-organic framework surviving guest removal is assembled from a well-defined tetrahedral Fe(4)L(6) cavity by the cooperativity of hydrogen bonds and [small pi]-[small pi] stacking.
RESUMO
A novel multiple alkali metal cluster K3(H2O)]3+ interior within a high-symmetry cubic capsule containing 16-nitrogen donors is achieved via self-assembly from twenty components.