A Modular Approach to Inorganic Phosphazane Macrocycles.

Inorganic macrocycles, based on non-carbon backbones, present exciting synthetic challenges in the systematic assembly of inorganic molecules, as well as new avenues in host-guest and supramolecular chemistry. Here we demonstrate a new high-yielding modular approach to a broad range of trimeric and hexameric S- and Se-bridged inorganic macrocycles based on cyclophosphazane frameworks, using the building blocks [S=(H)P(µ-NR)]2 . The method involves the in situ generation of the key intermediate [E....._ (S....._ )P(µ-NR)]22- (E=S, Se) dianion, which can be reacted with electrophilic [ClP(µ-NR)]2 to give PIII /PV hexameric rings or reacted with I2 to give trimeric PV variants. Important issues which are highlighted in this work are the competitive bridging ability of S versus Se in these systems and the synthesis of the first air-stable and chiral inorganic macrocycles.

A versatile hard-soft N/S-ligand for metal coordination and cluster formation.

Deprotonation of the thialdiphosphazane [S[double bond, length as m-dash]PH(µ-N(t)Bu)]2 with a range of metal-bases gives the stable dianion [S-P(µ-N(t)Bu)]2(2-), which is valence-isoelectronic with the widely-used [RN-P(µ-NR)]2(2-) ligand. Structural studies show that the new ligand has adaptable hard-soft character with respect to the coordinated metal centre and that its multidentate nature can be exploited to construct large cage architectures.

Synthesis and structures of [S=(H)P(µ-NR)]2, potential building blocks for inorganic phosphorus-sulfur macrocycles.

The reactions of the chloro-phosph(iii)azane dimers [ClP(µ-NR)]2 with LiSH give the dimers [S[double bond, length as m-dash](H)P(µ-NR)]2 (), which are potential new building blocks for inorganic macrocycles of the type [{P(µ-NR)}2(µ-S)]n. NMR spectroscopic studies and DFT calculations show that the preference for the cis or trans isomers of is largely influenced by the steric demands of the R-group, with cis isomers being preferred for bulky substituents. This is an important factor in regard to applications in macrocycle synthesis since the cis arrangement is pre-organized for cyclisation.

Size and Energy Level Tuning of Quantum Dot Solids via a Hybrid Ligand Complex.

The performance of quantum dots (QDs) in optoelectronic devices suffers as a result of sub-bandgap states induced by the large fraction of atoms on the surface of QDs. Recent progress in passivating these surface states with thiol ligands and halide ions has led to competitive efficiencies. Here, we apply a hybrid ligand mixture to passivate PbSe QD sub-bandgap tail states via a low-temperature, solid-state ligand exchange. We show that this ligand mixture allows tuning of the energy levels and the physical QD size in the solid state during film formation. We hereby present a novel, postsynthetic path to tune the properties of QD films.

Extending N-heterocyclic carbene ligands into the third dimension: a new type of hybrid phosphazane/NHC system.

A simple, "click" synthetic approach to a new type of hybrid phosph(III)azane/NHC system is described. The presence of the phosphazane P2N2 ring unit, with P atoms flanking the NCN fragment and with this ring perpendicular to the binding site of the NHC, provides unique opportunities for modifying the electronic and steric character of these carbenes.