Fluorene-based Ligand Research Articles

Bi-nuclear luminescent europium(III) molecular complexes for white light emitting diodes: Experimental and theoretical study

Two newly designed and synthesized ancillary ligands with N1 functionalization (phenyl and fluorene) and its influence on photophysical properties of their corresponding binuclear europium complexes were investigated systematically. Photoluminescence (PL) emission spectral study was shown dominant electric dipole transition of EuIII ion (5D0 → 7F2) and it is clearly indicated that the EuIII ion occupies in the non-centrosymmetric site. The calculated parameter via Judd-Ofelt shown ligands are the best sensitizer for EuIII metal ion. In addition, there is no emission in the region of 400–550 nm (belongs to ligand), indicates that the efficient energy transfer from ligand to central EuIII ion in the complex. The energy transfer mechanism was proposed by the help of DFT and TD-DFT calculations. The obtained highest QY (59.5%, thin film) of the complex, Eu2(TTA)6(L2) indicating efficient energy sensitization from fluorene-based ligand than that of phenyl based Eu-complex. The calculated CIE color coordinates are well matched with NTSC standard values. The binuclear Eu-complexes were combined with InGaN near UV LED, obtained pure red emission (forward bias 20 mA) with CIE color coordinate value x = 0.65, y = 0.34 and x = 0.66, y = 0.33 for Eu2(TTA)6(L1) and Eu2(TTA)6(L2), respectively.

The coordination chemistry of two symmetric fluorene-based organic ligands with cuprous chloride

Two novel symmetric fluorene-based ligands, namely, 2,7-bis(1H-imidazol-1-yl)-9,9-dimethyl-9H-fluorene [L1 or (I), C21H18N4] and 2,7-bis(1H-imidazol-1-yl)-9,9-dipropyl-9H-fluorene (L2), have been used to construct the coordination polymers catena-poly[[dichloridodicopper(I)(Cu-Cu)]-μ-2,7-bis(1H-imidazol-1-yl)-9,9-dimethyl-9H-fluorene], [Cu2Cl2(C21H18N4)]n, (II), and catena-poly[[tetra-μ2-chlorido-tetracopper(I)]-bis[μ-2,7-bis(1H-imidazol-1-yl)-9,9-dipropyl-9H-fluorene]], [Cu4Cl4(C25H26N4)2]n, (III). There are three types of C-H···N hydrogen bonds in (I), resulting a two-dimensional network in the ab plane, including a chiral helical chain along the b axis. Compounds (II) and (III) are related one-dimensional polymers. In both, Cu(I) atoms connect the symmetric ligands (L1 or L2) into a one-dimensional chain. In (II), the {[Cu(I)Cl2](-)} unit, acting as a co-anion, adheres to the one-dimensional chain through a weak Cu···Cu interaction. However, in (III), the {[Cu(I)2Cl4](2-)} unit links two different chains into a one-dimensional rope-ladder-type chain. In addition, there are C-H···Cl hydrogen bonds and π-π interactions in the extended structures of (II) and (III), the difference is that the chains in (II) are linked into a two-dimensional network while the chains in (III) are stacked into a three-dimensional framework.

Ligand-based luminescence in lead-containing complexes: The effect of conjugated organic ligands on fluorescence

The asymmetrically substituted heterocyclic alkyne 5-(pyridin-3-ylethynyl) picolinate (P3PA) was synthesized via a one-pot Sonogashira coupling. After purification, P3PA was reacted with Pb(NO3)2 into the two-dimensional coordination polymer Pb(P3PA)2(H2O)2 (1) under hydrothermal conditions. Coordination polymer 1 crystallizes into the monoclinic space group I2/a, with a = 15.5775(10) Å, b = 5.9949(4) Å, c = 24.8380(16) Å, and β = 90.7500(10)°. In addition, the luminescent fluorene-based ligands, fluorene-9-carboxylate (FCA) and fluorenone-2,7-dicarboxylate (FDCA), were incorporated into hybrid materials via coordination to the lead (II) cation. Coordination polymer Pb(FCA)2 (2) crystallizes in the monoclinic space group P21/c (a = 8.0518(9) Å, b = 25.338(3) Å, c = 10.5842(12) Å, β = 94.913(2)°), and forms a 1-D polymeric chain. Coordination polymer Pb3(FDCA)3(H2O)3 (3) crystallizes in the triclinic space group P1 (a = 6.6990(5) Å, b = 10.1529(7) Å, c = 13.6935(9) Å, α = 81.884(2)°, β = 87.260(2)°, γ = 84.399(2)°), and forms pillared 3-D layers. These three compounds have been identified via single crystal X-ray diffraction and characterized via powder X-ray diffraction, UV–Vis spectroscopy, and fluorescence spectroscopy.

Fluorene-based Cu(ii)-MOF: a visual colorimetric anion sensor and separator based on an anion-exchange approach

A new 2D Cu(II)-MOF generated from a fluorene-based ligand and Cu(NO(3))(2) was reported. It is an interesting visual colorimetric anion sensor. In addition, it can completely separate Cl(-)/Br(-), Br(-)/I(-) and SCN(-)/N(3)(-) anions under ambient conditions.

Two Luminescent Coordination Polymers with a Triple-Helix Structure: HgX2(C31H24N2)·CH2Cl2 (X = Cl and Br)

The two new luminescent coordination polymers HgCl2(C31H24N2)·CH2Cl2 (1) and HgBr2(C31H24N2)·CH2Cl2 (2) feature helical zigzag chains intertwined in bundles of three. The luminescent properties of the isostructural compounds are due to the fluorene-based ligand 9,9-bis-ethyl-2,7-di-(4-pyridyl)ethynylfluorene and are red-shifted relative to those of the free ligand.