Amber L. Thompson

Thermal and light induced polymorphism in iron(II) spin crossover compounds

The spin crossover complexes [Fe[H(2)B(pz)(2)](2)L]([H(2)B(pz)(2)](-)= dihydrobis(pyrazolyl)borate, L = 2,2[prime or minute]-bipyridine (1), bipy and 1,10-phenanthroline, phen (2)) undergo both thermal and light induced spin crossover, but the structure of the low spin and light induced high spin states for are different from that of the thermally induced high spin state and from those of.

A new precatalyst for the Suzuki reaction—a pyridyl-bridged dinuclear palladium complex as a source of mono-ligated palladium(0)

A dinuclear pyridyl-bridged palladium complex, trans-(P,N)-[PdBr(μ-C5H4N-C2,N)(PPh3)]21, was obtained from material isolated from the Suzuki cross-coupling reaction of 2-bromopyridine with 2,4-difluorophenylboronic acid in the presence of catalytic (PPh3)4Pd. Complex 1 is an effective precatalyst for the Suzuki cross-coupling reactions of a variety organoboronic acids and aryl bromides, and represents a useful source of mono-ligated palladium(0), “(Ph3P)Pd(0)”.

Bridged diiridium complexes for electrophosphorescent OLEDs: synthesis, X-ray crystal structures, photophysics, and devices

Results are presented which challenge the accepted view that dinuclear transition metal–ligand complexes are unsuitable for organic light-emitting device (OLED) applications due to their low luminescence quantum efficiencies. We establish for the first time that halo- and pseudo-halo-bridged diiridium(III) species are viable electrophosphorescent dopants in OLEDs. New cyclometalated chloro- and isocyanate-bridged diiridium(III) complexes, viz. tetrakis[9,9-dihexyl-2-(pyridin-2-yl)fluorene-C2,N′]-bis(μ-chloro)diiridium(III) [Ir(flpy)2Cl]2 (complex 3) and tetrakis[9,9-dihexyl-2-(pyridin-2-yl)fluorene-C2,N′]-bis(μ-isocyanate)diiridim(III) [Ir(flpy)2NCO]2 (complex 4) were obtained in high yield from the 9,9-dihexyl-2-(pyridin-2-yl)fluorene (flpyH) ligand 1. The X-ray crystal structures are described for 3 and the monomeric complex Ir(flpy)2NCO(DMSO) (5) which was obtained from 4. The solution-state photophysical properties of complexes 3 and 4 are characterised by emission from mixed 3π–π*/3MLCT states at ∼545–550 nm. Complex 4 displays a solution-state photoluminescence quantum yield which is five times that of the dichloro-bridged analogue 3. This is ascribed to an increase in the ligand-LUMO/metal eg gap which reduces the probability of non-radiative decay processes. Spin-coated organic light emitting devices (OLEDs) made from the host polymer poly(9,9-bis-2-ethylhexylfluorene-2,7-diyl) (PF2/6) end-capped with bis-(4-methylphenyl)phenylamine (PF2/6am4) doped with 12.5 wt% of the complexes 3 and 4 show good stability: turn-on voltages are low (<4 V) with maximum EL intensities of ∼1300 and 13 000 cd m−2, and peak external quantum efficiencies (EQE) of 0.1 and 0.8%, at ca. 400 and 60 mA cm−2, respectively.

Synthesis, photophysics and molecular structures of luminescent 2,5-bis(phenylethynyl)thiophenes (BPETs)

The Sonogashira cross-coupling of two equivalents of para-substituted ethynylbenzenes with 2,5-diiodothiophene provides a simple synthetic route for the preparation of 2,5-bis(para-R-phenylethynyl)thiophenes (R = H, Me, OMe, CF3, NMe2, NO2, CN and CO2Me) (1a–h). Likewise, 2,5-bis(pentafluorophenylethynyl)thiophene (2) was prepared by the coupling of 2,5-diiodothiophene with pentafluorophenylacetylene. All compounds were characterised by NMR, IR, Raman and mass spectroscopy, elemental analysis, and their absorption and emission spectra, quantum yields and lifetimes were also measured. The spectroscopic studies of 1a–h and 2 show that both electron donating and electron withdrawing para-subsituents on the phenyl rings shift the absorption and emission maxima to lower energies, but that acceptors are more efficient in this regard. The short singlet lifetimes and modest fluorescence quantum yields (ca. 0.2–0.3) observed are characteristic of rapid intersystem crossing. The single-crystal structures of 2,5-bis(phenylethynyl)thiophene, 2,5-bis(para-carbomethoxyphenylethynyl)thiophene, 2,5-bis(para-methylphenylethynyl)thiophene and 2,5-bis(pentafluorophenylethynyl)thiophene were determined by X-ray diffraction at 120 K. DFT calculations show that the all-planar form of the compounds is the lowest in energy, although rotation of the phenyl groups about the CC bond is facile and TD-DFT calculations suggest that, similar to 1,4-bis(phenylethynyl)benzene analogues, the absorption spectra in solution arise from a variety of rotational conformations. Frequency calculations confirm the assignments of the compounds’ IR and Raman spectra.

Synthesis and characterisation of some new boron compounds containing the 2,4,6-(CF3)3C6H2(fluoromes = Ar), 2,6-(CF3)2C6H3(fluoroxyl = Ar′), or 2,4-(CF3)2C6H3(Ar″) ligands

Several new boron compounds containing the 2,4,6-(CF3)3C6H2 (fluoromes = Ar), 2,6-(CF3)2C6H3 (fluoroxyl = Ar′) or 2,4-(CF3)2C6H3 (Ar″) ligands have been synthesised from reactions of ArLi, Ar′Li or Ar″Li with BCl3, and characterised by 19F and 11B NMR spectroscopy. Chlorine/fluorine exchanges are evident in these reactions. The crystal and molecular structures of Ar2BF, Ar″3B, Ar2B(OH), Ar′B(OH)2 and Mes2BF (Mes = 2,4,6-Me3C6H2) have been determined by single crystal X-ray diffraction. Ar″3B represents the first example of a compound containing three Ar″ ligands to be structurally characterised. Molecular geometries and GIAO-NMR shifts for several new boron compounds have been calculated at the HF/6-31G* level of theory, and compared with the available experimental results.

Alkyl and aryl dicationic derivatives of cyclic triphosphenium ions

Direct alkylation of cyclic triphosphenium ions by triflates to give di-ium dications is only possible for small organic substituents on the attacking reagent. The dicationic products are not intrinsically unstable, however, and in many instances they may be synthesised by an alternative route, pioneered by Schmidpeter and co-workers. These species may be readily identified in solution by (31)P NMR spectroscopy. The crystal and molecular structures of five such derivatives have been ascertained for the first time by single crystal X-ray diffraction at 120 K. The results confirm that normal single P-P bond lengths are present in the dications, in contrast with the monocationic parent cyclic triphosphenium ions, where structural determinations have shown that the P-P bond lengths are intermediate between single and double bonds.

Structural characterisation of a diprotonated ligand lanthanide complex—a key intermediate in lanthanide ion association and complex dissociation pathways

The X-ray structure is reported of a diprotonated Gd(III) tetra-aqua complex of the ligand 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (DOTAM), a thermodynamic intermediate in metal ion association and dissociation pathways.

New group 15 compounds containing the 2,4,6-(CF3)3C6H2 (fluoromes = Ar), 2,6-(CF3)2C6H3 (fluoroxyl = Ar′) or 2,4-(CF3)2C6H3 (Ar″) ligands

Several new P or As compounds containing the 2,4,6-(CF3)3C6H2 (Ar), 2,6-(CF3)2C6H3 (Ar′) and/or 2,4-(CF3)2C6H3 (Ar″) ligands have been synthesised, and characterised by multinuclear NMR spectroscopy and (for all isolated compounds) elemental analysis. The crystal and molecular structures of ArPBr21, Ar2PCl 2, Ar″2PCl 3, Ar″2PBr 4, Ar′Ar″AsCl 5, Ar′Ar″AsBr 6 and Ar′Ar″AsH 7 have been determined by single-crystal X-ray diffraction. A particularly interesting feature of these structures is close contacts between ortho-fluorines and the P or As atoms, as observed previously in Ar′Ar″PCl and Ar2AsCl.

1,1,3,3‐Tetra­phenyl‐1,2,3‐triphosphenium tetra­chloro­aluminate di­chloro­methane solvate

The title compound, (C27H26P3)[AlCl4]·CH2Cl2, was isolated from a mixture containing the triphosphenium ion and its protonated derivative. The central cation ring is non-planar, as in the analogous hexachlorostannate (though the structures are not isomorphous), and the P—P distances are intermediate between those typical for single and double bonds.

Structural studies of light-induced excited states

Over the past few years there has been a marked increase in the number of structural studies carried out on light-induced excited states. Until now, however, there has been no systematic approach to the irradiation of samples, which can make data collection difficult and results unreliable. This paper presents a device for mounting a laser on a CCD diffractometer; this device not only enables the collection of data without any constraints on the data collection strategy, but also simplifies alignment of the laser and can be left in place permanently.