Jiun-Wei Hu

Ratiometric Fluorescent/Colorimetric Cyanide-Selective Sensor Based on Excited-State Intramolecular Charge Transfer−Excited-State Intramolecular Proton Transfer Switching

A novel salicylideneaniline-based fluorescent sensor, SB1, with a unique excited-state intramolecular charge transfer-excited-state intramolecular proton transfer (ESICT-ESIPT) coupled system was synthesized and demonstrated to fluorescently sense CN(-) with specific selectivity and high sensitivity in aqueous media based on ESICT-ESIPT switching. A large blue shift (96 nm) was also observed in the absorption spectra in response to CN(-). The bleaching of the color could be clearly observed by the naked eye. Moreover, SB1-based test strips were easily fabricated and low-cost, and could be used in practical and efficient CN(-) test kits. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations further support the cyanide-induced ESICT-ESIPT switching mechanism. The results provide the proof of concept that the colorimetric and ratiometric fluorescent cyanide-selective chemodosimeter can be created based on an ESICT-ESIPT coupled system.

A White-Light-Emitting Small Molecule: Synthesis, Crystal Structure, and Optical Properties

A white-light-emitting small molecule (1) was synthesized and characterized by single-crystal X-ray diffraction. Compound 1 undergoes an excited-state intramolecular proton transfer (ESIPT) reaction, resulting in a tautomer that is in equilibrium with the normal species and exhibiting a dual emission that covers almost all of the visible spectrum, and consequently generates white light. Furthermore, the geometric structures, the frontier molecular orbitals (MOs), and the potential energy curves for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. The results show that the forward ESIPT and backward ESIPT may happen on the same timescale, enabling the excited-state equilibrium to be established.

Synthesis, X-ray Structure, Optical, and Electrochemical Properties of a White-Light-Emitting Molecule

A new white-light-emitting molecule (1) was synthesized and characterized by NMR spectroscopy, high resolution mass spectrometry, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma, with a = 12.6814(6), b = 7.0824(4), c = 17.4628(9) Å, α = 90°, β = 90°, γ = 90°. In the crystal, molecules are linked by weak intermolecular C-H···O hydrogen bonds, forming an infinite chain along [100], generating a C(10) motif. Compound 1 possesses an intramolecular six-membered-ring hydrogen bond, from which excited-state intramolecular proton transfer (ESIPT) takes place from the phenolic proton to the carbonyl oxygen, resulting in a tautomer that is in equilibrium with the normal species, exhibiting a dual emission that covers almost all of the visible spectrum and consequently generates white light. It exhibits one irreversible one-electron oxidation and two irreversible one-electron reductions in dichloromethane at modest potentials. Furthermore, the geometric structures, frontier molecular orbitals (MOs), and the potential energy curves (PECs) for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations. The results demonstrate that the forward and backward ESIPT may happen on a similar timescale, enabling the excited-state equilibrium to be established.

1,6-Diaminoperylene bisimide with a highly twisted perylene core

Abstract1,6-Diaminoperylene bisimide (1) was synthesized and characterized by single-crystal X-ray diffraction. To the best of our knowledge, this is the first time that the structure of 1,6-disubstituted perylene bisimide has been reported. The crystal belongs to triclinic, space group P-1, with a = 10.3966(10), b = 15.3398(16), c = 16.8495(17) Å, α = 79.490(4)∘, β = 87.055(3)∘, γ = 79.423(3)∘, and Z = 2. Compound 1 possesses two intramolecular C–H ⋯N hydrogen bonds, which generate two S(6) ring motifs. The central perylene core of 1 is twisted with dihedral angles of 19.48(2) ∘ and 19.50(2) ∘; this twist configuration induces the axial chirality in this family of perylene bisimide chromophores. Density functional theory (DFT) calculations also show that the core twist angles of 1,6-diaminoperylene bisimide are larger than those of 1,7-diaminoperylene bisimide, which may account for the fact that the 1,7-regioisomer has a more extended effective conjugation length than the 1,6-regioisomer. Graphical Abstract1,6-Diaminoperylene bisimide (1) was synthesized and characterized by single crystal X-ray diffraction. The central perylene core of 1 is twisted with dihedral angles of 19.48(2)° and 19.50(2)°; this twist configuration induces the axial chirality in this family of perylene bisimide chromophores.

Synthesis, Crystal Structure, and Spectroscopic Properties of (Z)-4-(2-Methoxybenzylidene)-1-methyl-2-phenyl-1H-imidazol-5(4H)-one

The title compound, (Z)-4-(2-methoxybenzylidene)-1-methyl-2-phenyl-1H-imidazol-5(4H)-one (1), was synthesized and characterized. Compound 1 possesses two weak intramolecular C–H···O and C–H···N hydrogen bonds, which generate S(5) and S(6) rings, respectively. Intermolecular π–π stacking between the imidazolone ring and its adjacent one is observed in the crystal structure, which links a pair of molecules into a cyclic centrosymmetric dimer. Furthermore, two different C–H···π interactions lead to the formation of columns along the [100] direction that are connected to one another via intermolecular C–H···O hydrogen bonds, so linking the molecules into a continuous three-dimensional framework. Its spectroscopic properties and complementary density functional theory calculations are also reported.