A ratiometric and on–off fluorescent chemosensor (PB) containing a pyrene moiety was designed and synthesized for the selective detection of trivalent chromium ion over other common metal ions using an intramolecular-charge transfer (ICT) mechanism. The fluorescence emission intensities showed a significant decrease of the emission intensity at 425 nm and formation of a new band at 594 nm upon excitation at 343 nm. A well-defined isoemissive point was observed at 564 nm with increasing Cr3 + concentration. The emission ratios (F425/F594) showed good linearity with Cr3 + concentration thereby allowing the detection of Cr3 + using a ratiometric fluorescence method with a detection limit of 0.23 μM. A Job plot indicated a 1:1 binding stoichiometry with an association constant (Ka) of 7.52 × 104 M− 1, which was further confirmed by MALDI-TOF analysis.A ratiometric and on–off fluorescent chemosensor (PB) for Cr3 + was designed and synthesized based on an ICT mechanism. The fluorescence emission intensities showed a significant decrease at 425 nm and formation of a new band at 594 nm (λem = 343 nm) with a well-defined isoemissive point at 564 nm with increasing Cr3 + concentration. The good linearity allows the detection of Cr3 + by a ratiometric fluorescence method with a detection limit of 0.23 μM.

•A novel chiral dinuclear Cu(II) cluster has been synthesized and characterized.•The two Cu ions in complex 1 are sitting in a distorted octahedral arrangement.•Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers.•Magnetic susceptibility measurements indicate the presence of ferromagnetic Cu⋯Cu exchange.A novel chiral dinuclear Cu(II) cluster [Cu2(bpca)(bpy)(H2O)(NO3)3] (1) (bpca− is the anion of bis(2-pyridylcarbonyl)amine and bpy is 2,2′-bipyridine), was synthesized and characterized. Single crystal X-ray diffraction analysis showed that the two Cu(II) ions in complex 1 are sitting in a distorted octahedral arrangement and bridged by the organic spacer bpca−. Hydrogen bonding links neighboring dinuclear units into a three-dimensional framework. Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers. Racemization of complex 1 was confirmed by circular dichroism (CD) spectroscopy. The temperature dependence of the magnetic susceptibility for complex 1 in the range 2–300 K indicates the presence of ferromagnetic Cu⋯Cu exchange. The data fitting gave the magnetic coupling constant J = 8.08 cm−1.A novel chiral dinuclear Cu(II) cluster [Cu2(bpca)(bpy)(H2O)(NO3)3] (1) was synthesized and characterized. Single crystal X-ray diffraction analysis showed that the two Cu(II) ions in complex 1 are sitting in a distorted octahedral arrangement and bridged by the organic spacer bpca. Inversion crystallographic symmetry gives dimers as either Λ or Δ isomers. The magnetic studies indicate that Cu(II) ions in complex 1 are ferromagnetically coupled with the magnetic coupling constant J = 8.08 cm−1.

Two 1D systems with formulae [Ni(3,5-dmpy)2(N3)2]n (1) and [Co1.5(3,5-dmpy)3(N3)3]n (2) (where 3,5-dmpy stands for 3,5-dimethylpyridine) have been synthesized, and their magnetic properties have been analyzed. Both complexes crystallize in the monoclinic space group P21/n, with a = 13.302(3) Å, b = 7.5138(15) Å, c = 16.637(3) Å and β = 103.61(3)°, and a = 11.559(2) Å, b = 14.136(3) Å, c = 16.174(3) Å and β = 98.08(3)°, for 1 and 2 respectively. Compound 1 consists of a chain of nickel ions linked by double EE (end-to-end) azido bridges. In complex 2, the cobalt ions are linked by azide moieties, with an EO (end-on)–EO–EE sequence. Magnetic studies performed in the temperature range 2.0–300 K reveal that 1 and 2 exhibit spin-canting antiferromagnetic interactions along the azido-bridged chain. In addition, these magnetic investigations indicate that complex 1 behaves as a metamagnet.