Efficient non-doped OLEDs have been achieved using new binuclear tetracoordinate organoboron complexes containing 2-(N-aryl)formiminopyrrolyl ligands.

The synthesis and characterization of an oxidovanadium(IV) [V^IVO(L)(acac)] (1) and of two dioxidovanadium(V) [V^VO₂(L′)] (2) and [V^VO₂(L)] (2a) complexes of the Schiff base formed from the reaction of 4-(p-fluorophenyl) thiosemicarbazone with pyridine-2-aldehyde (HL) are described. The oxidovanadium(IV) species [V^IVO(L)(acac)] (1) was synthesized by the reaction of V^IVO(acac)₂ with the thiosemicarbazone HL in refluxing ethanol. The recrystallization of [V^IVO(L)(acac)] (1) in DMF, CH₃CN or EtOH gave the same product i.e. the dioxidovanadium(V) complex [V^VO₂(L)] (2a); however, upon recrystallization of 1 in DMSO a distinct compound [V^VO₂(L′)] (2) was formed, wherein the original ligand L⁻ is transformed to a rearranged one, L′⁻. In the presence of DMSO the ligand in complex 1 is found to undergo methylation at the carbon centre attached to imine nitrogen (aldimine) and transformed to the corresponding V^VO₂-species through in situ reaction. The synthesized HL and the metal complexes were characterized by elemental analysis, IR, UV–Vis, NMR and EPR spectroscopy. The molecular structure of [V^VO₂(L′)] (2) was determined by single crystal X-ray crystallography. The methylation of various other ligands and complexes prepared from different vanadium precursors under similar reaction conditions was also attempted and it was confirmed that the imine methylation observed is both ligand and metal precursor specific. Complexes 1 and 2 show in vitro insulin-like activity against insulin responsive L6 myoblast cells, higher than V^IVO(acac)₂, with complex 1 being more potent. In addition, the in vitro cytotoxicity studies of HL, and of complexes 1 and 2 against the MCF-7 and Vero cell lines were also done. The ligand is not cytotoxic and complex 2 is significantly more cytotoxic than 1. DAPI staining experiments indicate that an increase in the time of incubation and an increase of concentration of the complexes lead to the increase in cell death.

A series of zinc complexes of the general formula {[ZnCl(ArNC(An)–C(An)NAr)]⁺}₂[Zn₂Cl₆]²⁻ (where Ar = 2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl 2a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)phenyl 2b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl 2c; An = acenaphthene backbone) were prepared by the condensation of acenaphthenequinone with the corresponding o-triazolyl-substituted anilines (2-(1-benzyl-1H-1,2,3-triazol-4-yl)aniline 1a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)aniline 1b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline 1c) which were formed by the copper(I)-catalyzed Huisgen[3+2] dipolar cycloaddition between 2-ethynylaniline and the corresponding azides in high yields, using anhydrous ZnCl₂ as the metal template, in boiling glacial acetic acid. Zinc complexes of the type [ZnCl(ArNC(An)–C(An)NAr)]⁺[ZnCl₃(NCCH₃)]⁻ (4a–c) were synthesized by crystallisation of the corresponding complexes 2a–c in acetonitrile, at −20 °C. After removal of zinc dichloride from complexes 2a–c by the addition of potassium oxalate, in dichloromethane, the tetradentate N,N,N,N-chelating α-diimine ligands of the type ArNC(An)–C(An)NAr (5a–c) were obtained. The new ligand precursors and zinc complexes were characterised by elemental analysis, ¹H and ¹³C{¹H} NMR spectroscopy, two-dimensional NMR spectroscopy, and X-ray diffraction. Reaction of the ligand precursors 5a–c with [NiBr₂(DME)], in dichloromethane, gave nickel complexes of the type [NiBr₂(ArNC(An)–C(An)NAr)] (6a–c). The results of single crystal X-ray diffraction characterisation and magnetic susceptibility measurements demonstrated that nickel complexes 6a–c possess octahedral geometries around the nickel atoms with variable configurations, the Br atoms of which can be ionized when dissolved in methanol. In preliminary catalytic tests, complexes 6a–c revealed to be active as catalysts for the polymerisation of norbornene and styrene, when activated by cocatalyst MAO. The characterisation of the polymers by ¹H and ¹³C{¹H} NMR spectroscopy, gel permeation chromatography/size-exclusion chromatography (GPC/SEC) revealed that these polymers were formed by a coordination addition mechanism.