•We report a Hg2+ two-photon fluorescent probe based on spirobifluorene for the first time.•The molecule exhibits high selectivity and excellent sensitivity in both UV/Vis absorbance and one-photon fluorescence detection of Hg2+.•The molecule is a pH probe and suitable to detect acidic regions in cells.•The two-photon emission wavelength change before and after addition of Hg2+ is large.•The molecule enables fluorescence imaging of both the probe and mercury ions in cells by two-photon microscopy.A novel fluorescent probe SPF-TSA was prepared by introduction of triphenylamine and dithioacetal groups on the respective biphenyl branches of 9,9′-spirobifluorene. The probing behaviors toward metal ions and pH variations were investigated via UV/Vis absorption spectra as well as one-photon fluorescence changes. SPF-TSA exhibits high sensitivity and selectivity for mercury ions and could be used to detect mercury ions even by naked eye. The detection limit of SPF-TSA for Hg2+ is at least 2.6 × 10−8 M, which is excellent comparing with other optical sensors for Hg2+. SPF-TSA showes significantly pH-dependent spectral properties within the acidic pH-range. Especially, the pKa value of SPF-TSA is close to 6.0, which is critical for precisely assessing the acidic environments of some organelles (pH 4.5–6.8). The two-photon absorption cross-section value of SPF-TSA at 800 nm is 248 GM. SPF-TSA emits strong two-photon induced fluorescence and the emission wavelength change before and after addition of Hg2+ was found to be up to140 nm. Cell imaging studies demonstrate that SPF-TSA enables fluorescence imaging of both the probe and mercury ions in cells by two-photon microscopy.

•We report Ag+ two-photon fluorescence probes containing spirobifluorene for the first time.•The molecules exhibit high selectivity and excellent sensitivity in both UV/Vis absorbance and one-photon fluorescence detection of Ag+.•The molecules have large two-photon cross-sections.•One molecule is a promising two-photon probe potentially applicable for bioimaging.•Another molecule is an excellent probe to measure water content of organic solvents.Two fluorophores, SPF-TNS and SPF-TBB, with electron-rich triphenylamine groups and Ag+ receptor units on the respective biphenyl branches of 9,9′-spirobifluorene were synthesized. They exhibit strong one- and two-photon excited fluorescence, and the two-photon absorption cross-section values are 665 GM for SPF-TNS and 355GM for SPF-TBB. The probing behaviors toward metal ions were investigated via UV/Vis absorption spectra as well as one-photon fluorescence changes. The results indicated that SPF-TNS and SPF-TBB exhibit distinct fluorescent quenching in the presence of silver ions that can be used for highly sensitive and selective naked-eye detection of Ag+. The one-photon excited fluorescence of SPF-TBB can be made to measure water content of organic solvents. The detection limits were calculated to be 0.04% for THF and 0.03% for 1,4-dioxane. The two-photon scanning microscopy experiments suggest that SPF-TNS is a promising label potentially applicable for the tracking of biomolecules.

•Quite high thermal stability for organic light emitting diode applications.•Good hole-injection and -transporting ability.•The molecule can be prepared starting from the readily available reagent biphenyl.•The CIE coordinates is close to the standard for blue.•The EL performances are among the best comparing to recently reported blue emitting devices.A tert-butylated spirobifluorene derivative incorporating triphenylamine groups was synthesized starting from the readily available reagent biphenyl. Without any hole-transport layer, an unoptimized double-layer device exhibits excellent electroluminescent performances with a radiance of 3013 cd/m2 at 9.8 V, a maximum electroluminescent efficiency of 1.71 cd/A, a maximal external quantum efficiency of 2.58% at a brightness of 4.8 cd/m2, narrow full width at half-maximum (<54 nm), and blue emission with Commission Internationale de l'Eclairage coordinates of (0.152, 0.103), which is close to the standard for blue. Compared to the reported organic light emitting diodes materials, the molecule displays very high thermal stability. In addition, the bilayer device showed a greatly improved performance as compared to a trilayer device with NPB as hole-transporting layer, which indicated that the molecule possesses good hole transport ability and can be good candidate for hole-transporting layer in organic light emitting diodes.

•We report a molecule exhibiting excellent transparency.•The two-photon absorption cross-section is as large as 4.5 × 103GM.•The molecule exhibits excellent thermal stability.•The molecule is a good two-photon induced blue fluorescent material.•The spiroconjugation effect explains the excellent properties.A spirobifluorene-bridged donor/donor chromophore, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9′-spirobifluorene (SPF-TP), was found to combine excellent transparency in the near UV–visible region (λcut-off ≤ 420 nm), large two-photon absorption cross-section (4.5 × 103GM) and high thermal stability (Td = 501 °C). In comparison to the reported two-photon absorption molecules, SPF-TP represents the best thermal stability so far described in the literature. The main electronic factors explaining the high two-photon absorption activities of SPF-TP were analyzed by theoretical calculations. Cyclic voltammograms were employed to explore the causes of the excellent transparency of SPF-TP. It was found that the spiroconjugation effect is responsible for the excellent nonlinearity/transparency/thermal stability trade-off in SPF-TP. In addition, SPF-TP is also a good two-photon induced blue fluorescent material with high fluorescence quantum yield (Φ = 0.90, in THF).

•A novel methyl pyridinium salt based on dipicolinate was synthesized.•The molecule exhibits pronounced negative solvatochromism.•High spectral sensitivities to water content changes in solvents were observed.•The molecule possesses high absorption spectral sensitivities to pH variations.•Enhanced two-photon absorption activity was obtained.A novel pyridinium salt based on dipicolinate, PM-1 was synthesized from the corresponding neutral chromophore and enhanced two-photon absorption activity was obtained. The two-photon absorption cross section value is 6.8 × 102 GM. PM-1 exhibits pronounced negative solvatochromism and possesses high absorption spectral sensitivities to pH and water content changes. PM-1 could be used as pH probe and to measure the water content, particularly for less than 10%, in common water miscible organic solvents such as THF, 1,4-dioxane, acetone and methanol.

•Three novel triphenylamine vinyl pyridinium salts based on dipicolinate were synthesized.•The molecules display considerably high two-photon cross-sections and reasonable water solubility.•PM-2 shows the highest value of two-photon absorption cross-section reported for such pyridinium salts.•The molecules exhibit negative solvatochromism and absorption spectral sensitivities to pH and water content variations.Three D–π–A type pyridinium salts based on dipicolinate were synthesized. Compared to the corresponding neutral chromophores, enhanced two-photon absorption activity and water solubility were obtained. When measured by the Z-scan technique at 800 nm, the three molecules display considerably high values of two-photon absorption cross-section. The two-photon absorption cross-section values were found to be in the range 2421–25,318 GM. In addition, the three molecules exhibit pronounced negative solvatochromism and possess absorption spectral sensitivities to pH and to changes in the water content of tetrahydrofuran.

A series of novel 9,9′-spirobifluorene-bridged donor-π-acceptor chromophores containing triarylamine moieties were easily synthesized starting from the readily available reagent 4,4′-dimethylbiphenyl. These chromophores were found to combine excellent transparency in the visible region, high thermal stabilities, and large optical nonlinearity.

Three novel ligands containing pyridine-2,6-dicarboxylic acid unit, trans-4 -(4′-methoxystyryl) pyridine-2,6-dicarboxylic acid, trans-4-(4′-(dimethylamino)styryl)pyridine-2,6-dicarboxylic acid, and trans-4-(4′-(diphenylamino)styryl)pyridine-2,6-dicarboxylic acid were synthesized and their complexes with Eu(III), Tb(III) ions were successfully prepared. The ligands and the corresponding metal complexes were characterized by means of MS, elemental analysis, IR, 1H NMR and TG–DTA. The luminescence spectra of Eu(III) and Tb(III) complexes in solid state were studied. The strong luminescence emitting peaks at 615 nm for Eu(III) and 545 nm for Tb(III) can be observed. The applications in cell imaging of the europium and terbium complexes were investigated.Graphical abstract.Highlights► Eu(III), Tb(III) complexes with novel ligands were synthesized. ► The coordination numbers of Eu(III) and Tb(III) ions is nine. ► The characteristic luminescence of europium and terbium ions can be observed. ► The europium and terbium complexes were applied in cell imaging.

Three novel chromophores, trans-dimethyl 4-(4′-methoxystyryl)pyridine-2,6-dicarboxylate (5), trans-dimethyl 4-(4′-nitrostyryl)pyridine-2,6-dicarboxylate (6), trans-dimethyl 4-(2-(1H-benzo[d]imidazol-2-yl)vinyl)pyridine-2,6-dicarboxylate (7) were synthesized and characterized. Their absorption, photoluminescence as well as two-photon absorption properties were studied. These compounds have strong linear absorption bands around 322–340 nm. From femtoscond nonlinear transmission measurements, compounds 5 and 7 have effective two-photon cross sections (σ) at 800 nm.

A novel naphthalimide molecule, 4-(2-methoxyethoxy)-N-butyl-1,8-naphthalimide (MEBN), has been synthesized and characterized. The UV–visible absorption and fluorescence emission spectral properties in n-hexane, toluene, CHCl3, and CH3OH were studied. Its optical properties depend on solvent polarity. The application of MEBN in cell imaging was investigated.

The presence of two carboxylic acid groups and two hydroxyl groups within the novel dye, (E)-4-(4-bis(2-hydroxyethyl)amino)styryl)pyridine-2,6-dicarboxylic acid, resulted in good water solubility. The compound's UV absorption and photoluminescence spectra were each highly pH sensitive in acidic solutions and two isobestic points were observed. The TPA cross-section coefficient and two-photon fluorescence cell imaging of the dye were investigated.