Conducting polymers of a Schiff-base ligand and the corresponding oxo-vanadium(IV) complex have been synthesized, characterized, and studied. The metal-free ligand polymer allows for direct comparison between the properties of the ligand polymer and corresponding conducting metallopolymer. The role of the metal centers in the conducting metallopolymer is elucidated unambiguously.

Optoelectronic applications often rely on indium tin oxide (ITO) as a transparent electrode material. Improvements in the performance of such devices as photovoltaics and light-emitting diodes often requires robust, controllable modification of the ITO surface to enhance interfacial charge transfer properties. In this work, modifier films were deposited onto ITO by the electrochemical reduction of di(4-nitrophenyl) iodonium tetrafluoroborate (DNP), allowing for control over surface functionalization. The surface coverage could be tuned from submonolayer to multilayer coverage by either varying the DNP concentration or the number of cyclic voltammetry (CV) grafting scans. Modification of ITO with 0.8 mM DNP resulted in near-monolayer surface coverage (4.95 × 1014 molecules/cm2). X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of 4-nitrophenyl (NO2Ph) moieties on the ITO surface through the detection of a NO2 nitrogen signal at 405.6 eV after grafting. Further XPS evidence suggests that the NO2Ph radicals do not bond to the surface indium or tin sites, consistent with modification occurring either through bonding to surface hydroxyl groups or through strong physisorption on ITO. CV in the presence of an electroactive probe and electrochemical impedance spectroscopy (EIS) were used to investigate the electronic effects that modification via DNP has on ITO. Even at submonolayer coverage, the insulating organic films can reduce the current response to ferrocene oxidation and reduction by more than 25% and increase the charge transfer resistance by a factor of 10.

Two series of 4d–4f clusters [Ln8Cd24L12(OAc)48] and [Ln6Cd18L9Cl8(10)(OAc)28(26)] (Ln = Nd, Gd, Er, and Yb) with novel drum-like structures were prepared using a flexible Schiff base ligand. Their NIR luminescence properties were determined.

Four Zn-Ln salen complexes are formed with the Schiff base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine (H2L). The complexes are trinuclear [LnZn2L2(OAc)2]·CF3SO3·Et2O (Ln = Eu (1) and Tb (2)), and dinuclear [EuZnL(OAc)(NO3)2MeOH] (3) and [TbZnL(OAc)2(NO3)] (4). The structures of 1–4 were determined by single crystal X-ray crystallographic studies and the respective luminescence properties in MeCN solution were determined.Graphical abstractFour Zn–Ln salen complexes are formed with the Schiff base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine (H2L). The complexes are trinuclear [LnZn2L2(OAc)2]·CF3SO3·Et2O (Ln = Eu (1) and Tb (2)), and dinuclear [EuZnL(OAc)(NO3)2MeOH] (3) and [TbZnL(OAc)2(NO3)] (4). The structures of 1–4 were determined by single crystal X-ray crystallographic studies and the respective luminescence properties in MeCN solution were determined.Highlights► Synthesis of Zn–Ln (Ln = Eu and Tb) salen complexes. ► Crystal structures of Zn–Ln salen complexes. ► Luminescence properties of Zn–Ln salen complexes.

Recent work in the area of luminescent lanthanide-containing metallopolymers has been reviewed, as well as potential applications. These hybrid materials are classified into three types, Wolf Types I–III, which are distinguished by the position of the metal center relative to the polymer backbone and the subsequent electronic interactions of the two components. These interactions, the nature of the lowest lying excited state, energy transfer processes, and non-radiative deactivation pathways must all be carefully considered when designing luminescent lanthanide-containing metallopolymers. The advantages and disadvantages of each type have been discussed.Graphical abstractHighlights► We review luminescent lanthanide-containing metallopolymers. ► Metallopolymers are classified as Wolf Types I–III. ► We review potential applications of lanthanide-containing metallopolymers. ► The advantages and disadvantages of each are discussed.

Electropolymerization of novel gallium Schiff-base complexes results in conducting metallopolymers containing either coordinatively saturated or unsaturated gallium metal centers. Depending on the chemical coordination of the metal centers, the embedded metal ions can act as seed points for the direct growth of size-controlled gallium sulfide nanoparticles in a conducting polymer, yielding a hybrid electronic material.

A new class of highly luminescent nine-coordinated europium(III) tris(β-diketonate) bis[(ethylenedioxythiophene)pyrazolyl]pyridine (L) complexes has been synthesized and the photophysical properties studied: 1 = Eu(hfac)3(L); 2 = Eu(tta)3(L); 3 = Eu(btfac)3(L). The solid-state structure of complex 1 has been determined by single-crystal X-ray crystallography and shows the geometry of the local coordination environment around the EuIII ion to be a slightly distorted tricapped trigonal prism. Luminescence lifetimes were found to be 581, 473, and 576 μs for complexes 1−3, respectively. Absolute quantum yields for complexes 1−3 were measured as 16.4 ± 1.4%, 27.5 ± 1.2%, and 22.2% ± 0.3%, respectively.

Metal-controlled assembly results in a series of lanthanide clusters with the formula of Ln5(DBM)10(OH)5·n(solvent) (DBM = dibenzoylmethanido; Ln = Nd (1), Gd (2), Er (3), and Yb (4); solvent = CH3CN or toluene). These pentanuclear clusters with square-pyramidal core structures have been characterized by X-ray diffraction analysis. Clusters 1, 3, and 4 show typical near-infrared (NIR) luminescence upon excitation at 350 nm, which represents the first examples of pentanuclear lanthanide clusters with sensitized NIR emission.

In organic thin-film transistors (OTFTs), organic electron-transport materials (n-type semiconductors) are well behind the advances in development of hole-transport materials (p-type semiconductors). Currently, one class of organic n-type semiconductor materials that is widely utilized is N,N′-dialkyl-3,4,9,10-perylenetetracarboxylic diimide (PTCDI-R) derivatives with high electron affinities (EAs), such as N,N′-dioctyl-3,4,9,10-perylenetetracarboxylic diimide with a reported EA as high as 4.4 eV. The PTCDI-R derivatives have been manipulated by adding substituents on the perylene moiety or at the amine position to afford more stable compounds and higher EAs. On the basis of these materials, we have developed metal-containing perylenediimide analogues, placing a salpen ligand for metal ion chelation between two n-isobutylnaphthalimides. We demonstrate here that the electronic properties of this class of materials can be systematically tuned in a divergent manner by simply changing the metal center. The synthesis, characterization, electrochemistry, and band-gap analysis are discussed herein.

A bromo tricarbonyl rhenium(I) complex with a thiophene-functionalized bis(pyrazolyl) pyridine ligand (L), ReBr(L)(CO)3 (1), has been synthesized and characterized by variable temperature and COSY 2-D 1H NMR spectroscopy, single-crystal X-ray diffraction, and photophysical methods. Complex 1 is highly luminescent in both solution and solid-state, consistent with phosphorescence from an emissive 3MLCT excited state with an additional contribution from a LC 3(π→π*) transition. The single-crystal X-ray diffraction structure of the title ligand is also reported.

A heterotrinuclear Zn–Gd complex [GdZn2L2(OAc)2](CF3SO3) (1) based on the salphen Schiff-base ligand bis(3-methoxysalicylidene)-1,2-phenylenediamine (H2L) was synthesized and characterized by single crystal X-ray diffraction. The structure was solved in the triclinic space group P − 1 with a = 9.4743(19), b = 16.333(3), c = 19.291(4) Å, α = 88.89(3), β = 78.16(2), γ = 76.69(3)°, V = 2842.0(10) Å3, Z = 2, Dc = 1.610 g/cm3, F (000) = 1,386, R1 = 0.0458, and wR2 = 0.1239. In the solid state short intermolecular O···H–C hydrogen bonding, π–π stacking, and H···π interactions between neighboring [GdZn2L2(OAc)2]+ moieties generate a porous 3D-framework architecture with extended channels running along the a-axis.

Electropolymerization of bithiophene-substituted cadmium(II) Schiff base complexes forms thin conducting metallopolymer films with metal centers distributed throughout. The metal centers act as seed points for direct growth of CdS nanoparticles within the polymer matrix under mild reaction conditions. This synthetic approach offers control over both the size and distribution density of the nanoparticles formed within the polymer film. The resulting hybrid materials hold promise for a variety of organic electronic and optoelectronic applications.

Reactions of the “salen” type Schiff basesH2L1 and H2L2 with Cd(OAc)2·2H2O gave complexes with Cd2 and Cd3 cores and an extended 1-D framework architecture [H2L1 = N,N′-(1,2-phenylenyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine; H2L2 = N,N′-(propyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine)].

Electropolymerization of novel gallium Schiff-base complexes results in conducting metallopolymers containing either coordinatively saturated or unsaturated gallium metal centers. Depending on the chemical coordination of the metal centers, the embedded metal ions can act as seed points for the direct growth of size-controlled gallium sulfide nanoparticles in a conducting polymer, yielding a hybrid electronic material.

A bromo tricarbonyl rhenium(I) complex with a thiophene-functionalized bis(pyrazolyl) pyridine ligand (L), ReBr(L)(CO)3 (1), has been synthesized and characterized by variable temperature and COSY 2-D 1H NMR spectroscopy, single-crystal X-ray diffraction, and photophysical methods. Complex 1 is highly luminescent in both solution and solid-state, consistent with phosphorescence from an emissive 3MLCT excited state with an additional contribution from a LC 3(π→π*) transition. The single-crystal X-ray diffraction structure of the title ligand is also reported.

Reactions of the “salen” type Schiff basesH2L1 and H2L2 with Cd(OAc)2·2H2O gave complexes with Cd2 and Cd3 cores and an extended 1-D framework architecture [H2L1 = N,N′-(1,2-phenylenyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine; H2L2 = N,N′-(propyl)-bis(5-bromo-2-hydroxy-3-methoxybenzaldimine)].

Conducting polymers of a Schiff-base ligand and the corresponding oxo-vanadium(IV) complex have been synthesized, characterized, and studied. The metal-free ligand polymer allows for direct comparison between the properties of the ligand polymer and corresponding conducting metallopolymer. The role of the metal centers in the conducting metallopolymer is elucidated unambiguously.