We constructed a series of novel optical sensors for determination of broad-range pH based on a single fluorophore and multi-ionophores with different pKa values. These optical sensors use photoinduced electron transfer (PET) as the signal transduction and follow the design concept of “fluorophore-spacer-receptor (ionophore)” which employs 4-amino-1,8-naphthalimide as the single fluorophore, ethyl moiety as the spacer, and a series of phenols and anilines as the receptors. Key to the successful development of this sensor system is that coupling the receptors with six different pKa values with a single fluorophore produces the correct optical properties. This rational design affords a series of optical pH sensors with unique fluorescence property and accurately tunable pH measurement ranging from 1 to 14 pH units. Because of covalent immobilization of the indicators, these sensors demonstrate excellent stability, adequate reversibility, and satisfactory dynamic range up to full pH ranges (pH 1–14).

A novel, fluorescent sensor based on 2,7-dichlorofluorescein with aromatized diethylene triamine as ionophore was developed. Under physiological pH conditions, the sensor exhibited about 70-fold enhancement in fluorescence emission upon binding with Cd2+. It demonstrates that the sensor can be used to detect Cd2+ in aqueous solution and it was successfully applied to image Cd2+ in living cells.

A novel Hg2+-selective fluorescent sensor (Sensor-Hg) based on a rhodamine scaffold, with N-Ethylthioethyl-N-[N′,N′-(2′-Diethylthioethylamino)-5′-methyl-Phenoxyethyl]-2-Methoxy Aniline (EDPMA) as a receptor, has been developed. Sensor-Hg exhibited ∼35-fold enhancement in fluorescence emission upon binding with Hg2+, with a characteristic emission band of rhodamine at ∼585 nm. It demonstrates high selectivity and sensitivity for detecting Hg2+ in aqueous solution and living cells.

A new 4-amino-1,8-naphthalimide-based fluorescent sensor with phenyliminodiethoxyacetic acid as a receptor was synthesized and characterized. It can be used for continuous monitoring of the calcium ion concentration in seawater with high selectivity against magnesium ions.

•Two new oxamido-bridged trinuclear complexes have been synthesized.•Both the complexes were prepared based on a vanadium-oxo complex ligand.•The magnetic behaviors of the two complexes have been investigated.By using a macrocyclic vanadium(IV)-oxo complex ligand VOL (H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as a precursor, two new trinuclear complexes [(VOL)2Co(C2H5OH)2](ClO4)2·2C2H5OH (1) and [(VOL)2Ni(CH3OH)2](ClO4)2 (2) have been synthesized and characterized by elemental analyses, IR spectroscopy, and power and single-crystal X-ray diffraction. In the two complexes, the central ions cobalt(II) and nickel(II) are connected with two VOL fragments via exo-cis oxamido bridge. Magnetic susceptibility measurements indicate that both complexes 1 and 2 show weak ferromagnetic interactions.By using a macrocyclic vanadium(IV)-oxo complex ligand VOL (H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as a precursor, two new trinuclear complexes [(VOL)2Co(C2H5OH)2](ClO4)2·2C2H5OH (1) and [(VOL)2Ni(CH3OH)2](ClO4)2 (2) have been synthesized and structurally characterized by X-ray crystallography. Magnetic susceptibility measurements indicate that weak ferromagnetic interactions exist in the two complexes.

•4-Amino-1,8-naphthalimide-PET-based fluorescent sensor was developed.•Iminodiacetic acid is used as a receptor.•It is high selectivity and sensitivity for Zn2 +.•It was successfully applied to image Zn2 + in living cells.A new 4-amino-1,8-naphthalimide-based fluorescent sensor with iminodiacetic acid as receptor, was synthesized and characterized. Under physiological pH conditions, it demonstrates high selectivity and sensitivity for sensing Zn2 + with about 50-fold enhancement in fluorescence intensity. The fluorescent sensor exhibited a characteristic emission band of 4-amino-1,8-naphthalimide with a green color centered at ~ 550 nm and was successfully applied to image Zn2 + in living cells. Upon sensing of Zn2 + the fluorescence emission spectrum is “switched on” demonstrating the suppression of PET from the receptor to the fluorophore.A new 4-amino-1,8-naphthalimide-PET-based fluorescent sensor, with iminodiacetic acid as receptor, demonstrates high selectivity and sensitivity for sensing Zn2 +. It was successfully applied to image Zn2 + in living cells.

A novel macrocyclic oxamidato-bridged vanadium (IV)-oxo mononuclear ligand VOL (VOL = vanadium (IV)-oxo H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,10,12-trimethyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) (1) has been synthesized by solvent-thermal in situ reaction and characterized by electron paramagnanetic resonance (EPR). Subsequently, using VOL as a precursor, its derivative trinuclear complexes [(VOL)2Cu(CH3OH)2](ClO4)2⋅2CH3OH (2) and [(VOL)2Zn(CH3OH)2](ClO4)2⋅2CH3OH (3) have been prepared and the crystal structures of the two complexes have been identified by the same method with 1. Thermal stabilities of compounds 1, 2 and 3 were studied and the results revealed that 1, 2 and 3 could be stable up to 205 °C, 234 °C and 250 °C, respectively. Moreover, the simulation of the EPR spectra of 1, 2 and 3 indicated the three oxo-vanadium samples were not oxidized and all of them remained in the active +4 oxidation state.Highlights► A novel macrocyclic oxamidato-bridged vanadium (IV)-oxo mononuclear ligand has been prepared. ► Two new trinuclear complexes have been synthesized using VOL as a precursor. ► TGA showed thermal stability of the two trinuclear complexes is higher than the mononuclear. ► EPR spectra indicated the three oxo-vanadium samples remained in the active +4 oxidation state.

Two novel oxamido-bridged macrocyclic complexes, [LCu(CH3OH)Co(phen)2](ClO4)2·CH3OH (1) and [LCu(CH3OH) Cu(phen)2](ClO4)2·CH3OH (2) (where H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,10,12-trimethyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene, phen = 1,10-phenanthroline), have been prepared by stepwise synthesis and characterized. In both complexes, each Cu(II) atom from the precursor ligand CuL is connected to a Co(II) (or Cu(II)) atom via the exo–cis oxygen atoms, resulting in a binuclear subunit. Magnetic susceptibility measurements in the 2–300 K temperature range have been taken for the two complexes.

By using the macrocyclic oxamido-copper complex CuL (H2L = 2,3-dioxo-5,6:13,14-dibenzo-9,10-(O)cyclohexyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as precursor, two new trinuclear complexes with the formulas [(CuL)2Mn(ClO4)2] (1) and [(CuL)2Co(ClO4)2] (2) have been synthesized and structurally characterized. H-bonds are found between the molecules, which link adjacent trinuclear units together to form a unique one-dimensional structure. The temperature dependence of the magnetic susceptibility for the complexes was analyzed by means of the Hamiltonian \( {\hat{H} } = - 2J{\hat{S}}_{1} {\hat{S}}_{2} , \) leading to J = −14.66 cm−1 and J = −22.9 cm−1 for 1 and 2, respectively.

Based on self-assembly of the dissymmetrical mononuclear entity CuL(CH3OH) [H2L = (E)-N1-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N2-(2-benzyl-4-chlorophenyl)oxalamide] with Mn(II), two trinuclear complexes were prepared. They are of the formula [(LCuN3)2Mn(CH3OH)2] · 2CH3OH · 2H2O (1) and [(LCuSCN)2Mn(H2O)2] · 4CH3OH (2). Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −14.40 cm−1 for 1 and J = −15.48 cm−1 for 2. Hydrogen bonds help complex 1 to produce a novel S type one-dimensional chain-like supramolecular structure. In complex 2, Cl⋯Cl interaction also results in the formation of a one-dimensional structure.Based on self-assembly of CuL(CH3OH) [H2L = (E)-N1-(2-((2-aminocyclohexy-diimino)(phenyl)methyl)-4-chlorophenyl)-N2-(2-benzyl-4-chlorophenyl)oxalamide] with Mn(II), two trinuclear complexes were prepared. They are of the formula [(LCuN3)2Mn(CH3OH)2] · 2CH3OH · 2H2O (1) and [(LCuSCN)2Mn(H2O)2] · 4CH3OH (2). Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −14.40 cm−1 for 1 and J = −15.48 cm−1 for 2.

Four lanthanide coordination polymers, [{Ln2(bpdc)3(phen)2(H2O)2} · (H2O)6]n (Ln = Sm (1); Eu (2); Gd (3), Tb (4)), were self-assembled from 2,2′-bipyridine-3,3′-dicarboxylic acid (H2bpdc),1,10-phenanthroline(phen) and corresponding lanthanide oxides by hydrothermal synthesis. Compounds 1–4 are found to be isomorphous and isostructural. Single-crystal X-ray diffraction studies show that compounds 1–4 are all of one-dimensional zigzag chain structures and extend to two-dimensional networks through π–π interactions and hydrogen bonds. The pyridyl nitrogen atoms of the 2,2′-bipyridyl unit in the bpdc ligand are uncoordinated in an anti-conformation along the central C–C bond of the ligand. Thermogravimetric analysis of 1–4 showed an obvious thermal stability indicating that the coordination habit of the metal ions with bpdc and phen has an effect on the overall framework. Photoluminescence measurement indicates that compound 2 and compound 4 are strong red and green emitters, respectively.Four lanthanide coordination polymers, [{Ln2(bpdc)3(phen)2(H2O)2} · (H2O)6]n (Ln = Sm (1); Eu (2); Gd (3), Tb (4)), were self-assembled from 2,2′-bipyridine-3,3′-dicarboxylic acid (H2bpdc),1,10-phenanthroline(phen) and corresponding lanthanide oxides by hydrothermal synthesis. Single-crystal X-ray diffraction studies show that compounds 1–4 are all of one-dimensional zigzag chain structures and extend to two-dimensional networks through π–π interactions and hydrogen bonds. Photoluminescence measurement indicates that compound 2 and compound 4 are strong red and green emitters, respectively.

Two oxamido-bridged trinuclear complexes of formula {[(LCu)(EtOH)]2Mn(EtOH)2}(ClO4)2 (1) and {[(LCu)(EtOH)]2Co(EtOH)2}(ClO4)2 · 2H2O (2) (H2L = 2,3-dioxo-5,6:13,14-dichlorobenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-pentadeca-7,11-diene) have been synthesized and structurally characterized. The central ions of complexes 1–2 (Mn(II), Co(II)) are all bridged by macrocyclic oxamido groups. Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −16.91 cm−1 for 1 and J = −27.73 cm−1 for 2.Two oxamido-bridged trinuclear complexes of formula {[(LCu)(EtOH)]2Mn(EtOH)2}(ClO4)2 (1) and {[(LCu)(EtOH)]2Co(EtOH)2}(ClO4)2 · 2H2O (2) (H2L = 2,3-dioxo-5,6:13,14-dichlorobenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-pentadeca-7,11-diene) have been synthesized and structurally characterized. Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −16.91 cm−1 for 1 and J = −27.73 cm−1 for 2.

Based on the complex ligand (CuL H2L = 2,3-dioxo-5,6:15,16-dibenzo-1,4,8,13-tetraazacyclotetradeca-7,13-diene), which includes macrocyclic oxamido bridge, three trinuclear complexes were prepared. They are of the formula [(CuL)2M(ClO4)2] (M = Co(1), Ni(2)) and [(CuL)2Zn(CH3OH)2] · (ClO4)2 (3). The crystal structures of the three complexes have been determined and the M(II) of the three complexes all exist on the mirror plane. Complex 1 is the first Cu–Co complex bridged by oxamido. Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −28.12 cm−1 for 1, J = −42.88 cm−1 for 2, and J = −2.13 cm−1 for 3.Three trinuclear complexes were prepared which includes macrocyclicoxamido bridge. The crystal structures of the three complexes have been determined and the M(II) of the three complexes all exist on the mirror plane. Their magnetic properties were studied by susceptibility versus temperature measurement.

A novel Hg2+-selective fluorescent sensor (Sensor-Hg) based on a rhodamine scaffold, with N-Ethylthioethyl-N-[N′,N′-(2′-Diethylthioethylamino)-5′-methyl-Phenoxyethyl]-2-Methoxy Aniline (EDPMA) as a receptor, has been developed. Sensor-Hg exhibited ∼35-fold enhancement in fluorescence emission upon binding with Hg2+, with a characteristic emission band of rhodamine at ∼585 nm. It demonstrates high selectivity and sensitivity for detecting Hg2+ in aqueous solution and living cells.

A new 4-amino-1,8-naphthalimide-based fluorescent sensor with phenyliminodiethoxyacetic acid as a receptor was synthesized and characterized. It can be used for continuous monitoring of the calcium ion concentration in seawater with high selectivity against magnesium ions.