Jianhua Yu

Rationally designed two-photon absorption compounds based on benzoxazole derivatives: structure–property relationships and bio-imaging applications

A new series of benzoxazole-based two-photon absorption (2PA) chromophores (T1-5) were synthesized and fully characterized. Among them, T1-3 are linear donor (D)-π-acceptor (A) type fluorophores with various electron-donating groups, while T4 and T5 are multi-branched compounds stemming from T3. Their photophysical properties have been systematically investigated, and the two-photon absorption properties indicate that the highest 2PA cross-section (σ2PA) is 2702 GM for T5 (in DMF). Structure-property relationships of the chromophores are comprehensively discussed based on their optical properties, crystal structures and density functional theory (DFT) calculations. In addition, a two-photon fluorescence cell imaging experiment demonstrates the potential bio-application of T1-5 with good photostability and low cytotoxicity.

Branched triphenylamine-core compounds: aggregation induced two-photon absorption

Three branched molecules (T1–T3) were synthesized through simple step to realize or enhance two-photon absorption (2PA) in aggregates. Spectra data show that one- and two-branched molecules (T1 and T2) possessed remarkable AIE properties, which came from the formation of J-aggregation because of their partial planarization in an aggregated state. SEM and DLS illustrate that the ordered aggregation and the small particle size had an important influence on fluorescence emission. Open aperture Z-scan experiments show that T1 and T2 possessed excellent 2PA properties in the aggregated state. The largest 2PA cross section was 8314 GM for T2 in aggregates, which was about 13-fold higher than that in pure solution. All the results demonstrate that the compounds could obtain outstanding 2PA performance by rationally adjusting their structure or changing state, which could provide a reference for preparing strong 2PA compounds.

Cadmium(II) supramolecular complexes constructed from a phenylbenzoxazole-based ligand: self-assembly, structural features and nonlinear optical properties

A new phenylbenzoxazole-based ligand bearing a pyridyl group (abbreviated as L) was designed and applied for self-assembly with corresponding cadmium(II) salts to generate four coordination complexes, namely, C19H15CdCl2N3O (1), C19H15Cd2Br2N3O (2), C40H38Cd2I4N6O4 (3) and C21H15CdN5OS2 (4). All the complexes 1–4 were fully characterized by single crystal X-ray diffraction. In 1 and 4, new supramolecular architectures are built mainly through synergistic effects of coordination bonds, hydrogen bonding interactions based on the anions and the benzoxazolyl nitrogen (oxygen) atom. There are more C–H⋯π and π–π stacking interactions constructing the higher dimensional structure in 2 and 3, respectively. In addition, in complex 3, we observe that CH3OH molecules are dispersed in the supramolecular structure and play a vital role in building the supramolecular structure. The nonlinear optical (NLO) properties of the complexes were investigated using the Z-scan technique, which showed that complexes 1 and 3 have obvious nonlinear absorption compared to ligand L.

High contrast off–on fluorescence photo-switching via copper ion recognition, trans–cis isomerization and ring closure of a thiosemicarbazide Schiff base

An easily available triphenylamine–isophorone-based Schiff base was synthesized and its specifically triple-addressable molecular photo-switching behaviour via copper ion recognition, trans–cis isomerization and ring closure were investigated in detail. Firstly, compound Lo was able to real-time monitor Cu2+ in an acetonitrile solution via displaying the “turn-on” emission in the near infrared region with high selectivity, and sensitivity. Furthermore, two independently photochromic phenomena based on the distinct mechanisms were found surprisingly, one through the ring closure of the thiosemicarbazide moiety based on a Michael addition reaction in tetrahydrofuran solution and another through the trans–cis isomerization of aldimine (–CN–) in the solid state under the stimuli of UV/visible light. Finally, fluorescence imaging experiments in living cells demonstrated the potential practical applications in biological systems.

Crystal structures and luminescence of a series of cadmium(II) complexes based on isophorone derivative containing imidazolyl

Three new complexes, [CdL2(CH3COO)2(H2O)2] (I), CdL2Br2 (II), CdL2I2 (III), have been successfully synthesized by self-assembly of corresponding metal salts with (E)-2-(3-(4-(1H-imidazole-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile (L). The structures of the complexes were determined by single crystal X-ray diffraction analysis (CIF file CCDC nos. 957831 (I), 957792 (II), 957832 (III)). In complex I, central metal is six-coordinated and the crystal packing shows a 3D supramolecular framework. Complexes II and III display the similar 2D supramolecular structures in which the central metals are four-coordination. The luminescent properties were investigated.

Anions-induced assembly: Structures and luminescent properties

Self-assembly of a multidentate ligand containing pyridyl groups, namely, 6-phenyl-4-(4′-[2-(2-naphthalene)ethenyl]phenyl)-2,2′-bipyridine (L) with corresponding zinc(II) salts, affords a series of coordination complexes, ZnLI2 (I), [ZnLCl2]2 · 2CH2Cl2 (II), ZnLBr2 (III). Complexes I and II were characterized by single crystal X-ray diffraction (CIF files CCDC nos. 943273 (I), 944798 (II)). In complex I, the π-π stacking and C-H⋯π interactions based on the pyridyl group constructed the 1D and 2D structures. While in complex II, various weak interactions including hydrogen bonds (C-H⋯Cl and C-H⋯π) played significant roles in the final supramolecular structures. The luminescent properties of ligand and the complexes were investigated. The results reveal that different anions have shown a great influence on both the molecular structures and luminescent properties of the complexes.

Correction: New zinc(II) dyes with enhanced two-photon absorption cross sections based on the imidazolyl ligand

Correction for ‘New zinc(II) dyes with enhanced two-photon absorption cross sections based on the imidazolyl ligand’ by Dan Liu et al., RSC Adv., 2016, 6, 77849–77853.

New zinc(II) dyes with enhanced two-photon absorption cross sections based on the imidazolyl ligand

A series of new zinc(II) complexes (Dyes 1–3) were obtained by self-assembly of the donor-bridge-donor (D–π–D) type ligand L with ZnX2 (X = Br, I, SCN). The single crystal of Dye 3 was obtained by slow evaporation of a mixture solution of methanol and dichloromethane. The molecular structure has been determined by X-ray crystallography. Hydrogen bonds (C–H⋯N, C–H⋯S) play significant roles in the final topological structures. Linear and nonlinear optical properties of the ligand and complexes were investigated in details. Experimental results revealed that effective two-photon absorption (TPA) cross sections of these complexes are larger than that of ligand L (18.7 GM) with the maximum values of 88.7 GM (Dye 1), 41.9 GM (Dye 2) and 46.5 GM (Dye 3) in DMF, respectively. The biological imaging result shows that L and Dyes 1–3 had excellent penetrability in living cells.