Twisted and Disconnected Chains: Flexible Linear Tetracuprous Arrays and a Decanuclear CuI Cluster as Blue- and Green/Yellow-Light Emitters

Defined arrays of transition metal ions embedded in tailored polydentate ligand scaffolds allow for a systematic design of their physical properties. Such molecular strings of closed-shell transition metal centers are particularly interesting for Group 11 metal ions in the oxidation state +1 if they undergo metallophilic d10···d10 contact interactions since these clusters are oftentimes efficient photoluminescence (PL) emitters. Copper is particularly attractive as a sustainable earth-abundant coinage metal source and because of the ability of several CuI complexes to serve as powerful thermally activated delayed fluorescence (TADF) emitters in molecular/organic light-emitting devices (OLEDs). Our combined synthetic, crystallographic, photophysical, and computational study describes a straight tetracuprous array possessing a centrally disconnected CuI2···CuI2 chain and a continuous helically bent CuI4 complex. This molecular helix undergoes a facile rearrangement in diethyl ether solution, yielding an unprecedented nanosized CuI10 cluster (2.9 × 2.0 nm) upon crystallization. All three clusters show either bright blue phosphorescence, TADF, or green/yellow multiband phosphorescence with quantum yields between 6.5 and 67%, which is persistent under hydrostatic pressure up to 30 kbar. Temperature-dependent PL investigations in combination with time-dependent density-functional theory (TD-DFT) calculations and void space analyses of the crystal packings complement a comprehensive correlation between the molecular structures and photoluminescence properties.

Hydrogen bonds and dispersion forces serving as molecular locks for tailored Group 11 bis(amidine) complexes

A flexible polydentate bis(amidine) ligand LH2 operates as a molecular lock for various coinage metal fragments and forms the dinuclear complexes [LH2(MCl)2], M = Cu (1), Au (2), the coordination...

Calcium and Magnesium Bis(β-diketiminate) Complexes: Impact of the Alkylene Bridge on Schlenk-Type Rearrangements

Dinuclear heteroleptic alkaline-earth-metal complexes are interesting synthetic targets because the close proximity of two metals allows for cooperative effects. However, these complexes are also prone to undergoing Schlenk-type rearrangements, affording less-active homoleptic complexes. Here we present the metalation of bis(β-diketimine) ligands possessing flexible bridging groups, i.e., 1,2-ethylene, 1,3-propylene, and trans-1,2-cyclohexylene, using calcium and magnesium precursors. Four mononuclear homoleptic calcium complexes were obtained, highlighting the pronounced tendency of calcium to undergo Schlenk-like redistributions. In the case of magnesium, however, the bridging group plays a crucial role, yielding seven dinuclear heteroleptic complexes but also one mononuclear and one dinuclear homoleptic complexes. In addition, a trinuclear mixed heteroleptic-homoleptic magnesium complex, which is a rare example of an intermediate of the Schlenk equilibrium, was isolated.

Synthesis, structure, and catalytic activity of dinuclear aluminium bis(amidinate) and bis(guanidinate) complexes

The ring-opening polymerization grand prix: Bis(amidinate)s outpaced their bis(guanidinate) competitors and won the race, while the drivers’ engines using acidic co-initiators collapsed before take-off.

Ditopic bis(N,N',N'-substituted 1,2-ethanediamine) ligands: synthesis and coordination chemistry

The synthesis of two different types of bis(N,N',N'-substituted 1,2-ethanediamine)s, bridged either through the secondary (type 1) or tertiary (type 2) amine groups is reported. Selected protio-ligands have been applied in subsequent metallation reactions using aluminium, magnesium, tin, and zinc sources allowing to isolate five mononuclear and eight dinuclear complexes. All complexes have been fully characterized and their solid-state structures have been studied by means of single-crystal X-ray diffraction analysis. Nine of the 13 complexes carry reactive alkyl, amide or hydride groups, which indicates their potential as catalysts or supports for (transition) metals.

Magnesium bis(amidinate) and bis(guanidinate) complexes: impact of the ligand backbone and bridging groups on the coordination behaviour

A library of ten dinucleating bis(amidine) and bis(guanidine) ligands, in which the bridging groups, terminal rests, and backbone substituents were systematically altered, has been synthesized and subsequently applied in metallation reactions using three different magnesium sources. Eight Mg complexes could be isolated and fully characterized, and in seven cases their solid-state structure could be determined by means of single crystal X-ray diffraction analysis. The results evidence a versatile coordination behaviour, which ranges from the first dinuclear heteroleptic magnesium iodide complex to dinuclear homoleptic complexes. These findings indicate the crucial impact of both the ligand and the magnesium source not only on the accessibility of well-defined dinuclear complexes but also on the aggregation in solution and in the solid state.

Ligands with Two Monoanionic N,N-Binding Sites: Synthesis and Coordination Chemistry

Polytopic ligands have become ubiquitous in coordination chemistry because they grant access to a variety of mono- and polynuclear complexes of transition metals as well as rare-earth and main-group elements. Nitrogen-based ditopic ligands, in which two monoanionic N,N-binding sites are framed within one molecule, are of particular importance and are therefore the primary focus of this review. In detail, bis(amidine)s, bis(guanidine)s, bis(β-diimine)s, bis(aminotroponimine)s, bis(pyrrolimine)s, and miscellaneous bis(N,N-chelating) ligands are reviewed. In addition to the general synthetic protocols, the application of these ligands is discussed along with their coordination chemistry, the multifarious binding modes, and the ability of these ligands to bridge two (or more) metal(loids).

Amido rare-earth(iii) and Ca(ii) complexes coordinated by tridentate amidinate ligands: synthesis, structure, and catalytic activity in the ring-opening polymerization of rac-lactide and ε-caprolactone

Y(iii), Sm(iii) and Ca(ii) monoamido complexes coordinated by tridentate amidinate ligand were synthesized and evaluated as initiators of ring-opening polymerization of rac-lactide and ε-caprolactone.

Preparation of star-shaped functionalized polylactides by metal porphyrin complexes as both catalysts and cocatalysts

Several aluminum porphyrin complexes as catalysts and a copper porphyrin complex as a cocatalyst were prepared. These complexes were characterized by 1H NMR and elemental analysis. These complexes are used for L-lactide polymerization. The kinetic data of the polymerization using complex 2 as catalyst revealed that the polymeric rates were first-ordered in both the monomer and catalyst. There is a linear relationship between lactide conversion and the number-averaged molecular weight of PLA.

Mono- and bimetallic amidinate samarium complexes - synthesis, structure, and hydroamination catalysis

In order to investigate the difference between mono- and bimetallic systems in the catalytic hydroamination/cyclization reaction two mono- and bimetallic amidinate samarium catalysts, featuring comparable coordination environments, were synthesized. Both systems comprise two {N(SiMe₃)₂}^- leaving groups to minimize the steric influence of the corresponding amidinate ligand. The bimetallic system is based on a bis(amidinate) 4,6-dibenzofuran derivative, while N,N'-bis(2,6-diisopropylphenyl)benzamidinate was employed as ligand for the monometallic catalyst. For the hydroamination/cyclization reaction five different substrates were investigated. Additionally, kinetic studies were carried out to gain deeper understanding of the mechanism.

Synthesis of biodegradable and biorenewable polylactides initiated by aluminum complexes bearing m-xylylenediamine derivatives via the ring-opening polymerization of lactides

Aluminum complexes derived from m-xylylenediamine were synthesized and investigated as initiators for l-lactide and rac-lactide polymerization.

A strategy to improve the performance of cerium(iii) photocatalysts

A structural modification strategy to improve the photocatalytic performance of molecular cerium(iii) luminophores was demonstrated.

Highly efficient hydroboration of carbonyl compounds catalyzed by tris(methylcyclopentadienyl)lanthanide complexes

(MeCp)₃Ln complexes are reported as highly efficient catalysts in promoting hydroboration and a plausible stepwise mechanism is proposed.

Rare-earth metal-mediated PhCN insertion into N,N-bis(trimethylsilyl)naphthalene-1,8-diamido dianion – a synthetic approach to complexes coordinated by ansa-bridged amido-amidinato ligand

We report the first example of rare earth metal-mediated insertion of PhCN into Si–N bonds with the formation of an amidinato moiety.

Bis(amido) rare-earth complexes coordinated by tridentate amidinate ligand: synthesis, structure and catalytic activity in the polymerization of isoprene and rac-lactide

Rare-earth bis(amides) {2-[Ph₂Р(O)]C₆H₄NC(tBu)N(2,6-Me₂C₆H₃)}Ln(N(SiMe₃)₂)₂ (Ln = Y, Nd, La) coordinated by tridentate amidinate ligand were synthesized, structurally characterized and evaluated as catalysts for isoprene and rac-lactide polymerizations.

Gallium and indium complexes containing the bis(imino)phenoxide ligand: synthesis, structural characterization and polymerization studies

A series of gallium and indium complexes containing the bis(imino)phenolate ligand framework were synthesized and completely characterized with different spectroscopic techniques.